installing dual batteries

[krazyfisher]

Two questions
1. where should you mounted the switch e.g. near the batteries, in the wheather, under cover?

2. how do you charge and run the batteries? one out one back? run out and back on both? when do you change over?

thanks

[blaze]

Mines in the weather
I normally use a run battery and if overnighting I use the 2nd battery as overnight battery, then start and run on the overnight battery the next day, that way I in theory get back to port with full charged batteries. Hasnt failed yet
cheers
blaze

[revs57]

Hi KF

Mine is under cover...I set the battery's up side by side under the rear transom, with a battery management switch and 150 amp curcuit breaker (BLA gear) mounted on the rear bulkhead wall immediately behind it - might be over kill but it works a treat

cheers

Rhys

[krazyfisher]

and 3rd question when would you use the both position?
thanks

[HarryO]

:) NEVER ;)

[Grand_Marlin]

Why not Harry?

I have actually only had one single engined boat with twin batteries and the changeover switch. The rest have had twin motors with separate batteries.

I always ran the switch on "both", in theory to charge both batteries.

The boat / batteries never really had any great drain out of them - only sounder, gps and occasional cabin light, so they weren't working hard at all.

When we stopped to fish, I always selected Batt 1, just in case it went flat. at least then Batt 2 is still good.

There must be a good reason why you say "Never", as you know your stuff.

I look forward to your reply, as I am obviously about to learn a lesson I didnt know.

Cheers

Pete

[Angla]

Personally I leave mine on 2 batteries all the time except when running a major appliance while fishing, like a deckwash pump for aerating the kill tank or lights at night time.
Then, when I am ready to pull the pin I go to both and charge back to the ramp.
I also alternate from battery 1 to 2 on different outings.
Both batteries are 70 amp marine batteries that give 660 CCA (cold crank amps) and I run a 135HP from that.
Batteries are positioned on the port and starboard sides for balance with the switch mounted up under a side with easy access.
You should keep the heavy leads as short as possible and close to the motor as possible to reduce voltage drop to the starter motor.

Angla

[drevil]

Pete, if the switch is set to both and, say battery 1 has less charge than battery 2, then battery 2 will spend its time trying to charge battery 1. You will always end up with the batteries at the same charge potential, which may not always be a good thing.

When I set up my older boat (now Cheech's) for 2 batteries, I had one original one and bought a new one. the original was maybe a year old and worked fine so I didn't replace it, but I felt it didn't hold a charge as well as the new one. So having it on both would effectively see the newer one wasting energy keeping the older one at charge.

Someone will probably offer a more technical explanation, but that's how I understand it works.

[Tony_N]

Doesn't having it on both all the time just mean that you are effectively operating on one battery. Then if one goes, they both go. Surely it is better to go out on one and in on the other that you have been using for sounder etc while out?

[Bosunsmate]

I was always taught go out on one and the change over and return on the other that way you always have a fully charged battery for emergencies.

[dnej]

The high crank battery, should be used to start your motor,and after start, is recharged by the run to your destination. They dont like to be fully discharged, and then long charged.

When you get there, switch to your deep cycle battery, to run all your gear. Deep cycle, doesn't mind getting run down, and long recharged.

Coming back,switch again to the high crank amp battery, to restart.

This usually leaves the deep cycle battery, not fully charged, when you get back to port, unless you are on a long run, and can switch over to this battery, on the way back.

The only time you should run on two, is to make sure you are always connected to a battery at all times, when you are running.

That is , dont move from say switch position 1, back through off, and then onto position 2.Move from position 1, through to position " both", (as you will remain connected to position 1),then onto position 2.

I have a recharge system, that I plug in when I store my boat at home, and the deep cycle gets the treatment firstly.

The charge system consists of a pos & neg wire, from the battery, to a 2 pin socket, on the dash.

A compatible plug, and short cable, go to the battery charger, which turns on and off, as the battery drops in power.

The two pin socket ( I have one for each battery), also allows for checking of voltage, using a multi meter. Also great for checking the charge rate of the motor.

Hope this all helps.

David

[finga64]

The only time you should run on two, is to make sure you are always connected to a battery at all times, when you are running.

That is , dont move from say switch position 1, back through off, and then onto position 2.Move from position 1, through to position " both", (as you will remain connected to position 1),then onto position 2.



Excellent point David. ;)
If you don't do this you have a good chance of stuffing something real bad ie rectifier/regulator or electronics in the motor (that's if the motor keeps going at all).

Yep, (assuming the batteries are the same) run out on one, use the other for standing still uses such a sounder etc #but see if the motor starts on the one you've been using whilst still (you soon get to know how long sitting and using things like sounder, radio etc still will flatten the battery beyond the ability to start) and give it a good old charge on the way home.
Batteries should be used alternatively in the high current/deep cycle uses
And running batteries on alternative trips is good maintenance because batteries are funny things ... the less you use it the quicker it takes to stuff up.

P.S. it's been said before but good to remember.
Keep the battery cable runs as short as practical, use good quality tinned cable, use good quality copper lugs on the cables, solder or crimp the lugs properly with the correct crimpers (I do both, but some say not to do both crimp and solder) and use a heat shrink with the resin to seal the cable/lug joint. Use good quality battery terminals with stainless bolts and use a good battery terminal treatment/sealer to seal the battery posts and terminals once the terminals are tight. And Bob's your uncle.
P.S.S. Don't forget to mount the batteries where they are accessable but can't get knocked and mount so they can't get loose and run around the boat.

[Dignity]

drevil has the most valid point - drop a cell in one of the batteries and you could be well and truly stuffed. Also have been advised never to have it on both if they are of different types eg deep cycle, high crank, calcium etc - don't know the reason why but did come from a battery seller and also independantly from an electrical engineer I once knew - any else heard this

sam

[Dignity]

I forgot - also have the negative terminals linked to a separate battery switch in case I have to charge the batteries at home or want to make sure there is no leakage what so ever - not really needed but feel more secure - this one is up under the gunwhales where a thief wouldn't think to look

[finga64]

drevil has the most valid point - drop a cell in one of the batteries and you could be well and truly stuffed. #Also have been advised never to have it on both if they are of different types eg deep cycle, high crank, calcium etc - don't know the reason why but did come from a battery seller and also independantly from an electrical engineer I once knew - any else heard this

sam
Very true Sam,
If a cell shorts out your stuffed if the switch is on both. It's like bunging a piece of wire over the terminals.
And if for instance you have a 900cca battery connected to a 350cca battery, when you connect them together and the 350cca battery is 1/2 charged and the 900cca battery is fully charged it's like putting the 350cca battery on a 125A charger. Gases build up quick, lots of heat and maybe a bang or BOOM.

[Magneto]

I have it on" BOTH" when I am doing a charge, connect it to one batt and the other charges as well, as one of the other posts mentioned about the batterys evening out. When going out today I use battery"1 " tomorrowr battery "2".
Anyway that what I been doing for years. Cheers Mag

[Tony_N]

So Magneto, when you charge on "both" do you simply rig up the charger with one lead to the positive of one battery and the other to the negative of the other battery?

[krazyfisher]

two more questions
1. is there any reason that rather than running the + to the switch you can run the -. I have been told to run the switch on the -

2 do you run the accessories to the battery and the common on the switch

its a 4 way switch 1,2,both,off and 3 nuts on the back(common,bat1,bat2)

the reason I ask is its all wiried up and the switch is a bit warm when playing with it

[HarryO]

Hi krazy, and Pete, and all.

Firstly, heat is a problem..

Wiring should be as follows.

Neg lead from engine, connect to Neg terminal on start battery. (1)

Pos lead from the engine connect to "common" on the switch.

Pos lead from start battery connect to "bat 1" on the switch.

Pos lead from 2nd battery connect to "bat 2" on the switch.

Neg lead from "bat 2" connect to neg terminal on Bat 1.

(Under no circumstances should a neg lead be connected to
the iso switch

Assuming there is no seperate field wire coming from
the outboard.

The main cable(s) in the harness from the helm (that was originally connected to the pos terminal) should be connected to the
"common" on the iso switch, and all the other items on board
should also be connected to "common" on the switch as well ,
either directly, or thru a positive "bus bar" set-up.

With the exception of the bilge pump, which should be
connected directly to the start battery, via an
auto/ override switch.

This ensures that nothing is left on to drain your batteries
when the switch is off.

Guys/gals with memory set radios and cd players should get
used to reprogramming the stations.

If there is a field wire present, then this can be connected to
a VSR (voltage sensitive relay) and then wired to each of
the pos terminals on both batteries.

Harry

[HarryO]

Pete,

The others have answered this well..

I know a lot of people who run with the switch in BOTH mode,
who have had no problems in doing so, but I adhere to
the following "method" in the interest of "best practice".

However, as mentioned prior, the battery with the least charge
will drain the better one until they level out, and the net gain
of power in the weaker battery is smaller than the net loss
of the better battery.

The charge "output" of most outboards, unles you have
one of the current larger 4 strokes, is pretty dismal.

Point in case, my 2000 mod 90hp Yamaha 2 stroke.

Charging output at idle is 1.5amps.

The rated MAXIMUM output is a whopping 12.5 amps @ 2000rpm.
(in the real world, this is 6-8 amps, input, per hour of running
at 2000rpm or above)

The power drawn in an average #start is 7-10 amps.
In a cold start, could use anything up to 100 amp or more.

I run 2 x M70 15 plate marine batteries, (fairly common)
and for reasons of space, they are fitted at the transom
in opposite corners.

I fitted the start battery starboard, close to the engine as possible,
and mounted the iso switch close as well, as this minimises
the length of cable required.

You know, you lose 1 volt for every metre of standard battery cable.

Using the 2nd battery to start the outboard is starving the
starter motor of full available power.

It may sound like nitpicking, but the quickest way to kill an
electric motor on, a say 15cfm compressor, is to run it off
an extension lead.

To charge one of these batteries from dead flat with one
of those 4A 240v home charges would take between 3-4
weeks! (not joking)

Best to start on the start battery, and direct all the available
current back to that battery, and keep the 2nd battery as a backup,
and to run the electronics while at anchor.

This will require periodical home charging of that battery.

Sorry to prat on.

Regards, # Harry..

#

[krazyfisher]

harry
your post was about the best info I have read.
thanks

[boyzie]

what size battries and what type

[dnej]

Hey Harry,
You didnt mention the negative connections, for all the electical items. You need a buzz bar for them as well, do you not?
Say, why the connection direct to the battery, for the Bilge pump?
David

[Boz]

HarryO

How many amp hours and or cca are your batteries?

Sounds like you have enough power going on there for a fully functioning warship.

A 1000cca battery (approx 110 a/hr) charging at 4 amps should be fully charged in about 27.5 hours. 4 amps per hour for 27.5 hours is 110 amps.

Also, a battery will reach its peak voltage very quickly, after this it only charges at about 4-5 amps per hour so if your outboard can put out 8-10 amps you should be able to charge two batteries at the same rate as if you were only chaging one.

Most 4WD vehicles with a duel battery set up run one battery for the starter which is isolated when the ignition is switched off. The other battery then runs everything (radio, fridge, etc) when the engine is switched off. That way you always have a good battery to start the engine even if the other is dead flat. On start up though, both batteries are connected when the engine is running in order to keep both fully charged.

Is this a different method than that used on a boat for a reason, or is it just more of a personal preferance thing?

It just makes sense to me to keep one just for starting and one for power when stationary and always charge both batteries.

Boz.

[HarryO]

No problem, Krazy.

Glad you understood it.

I was a bit concerned when I read it back later, as I
wrote the post off the top of my head, that it was a bit
"all over the place", and it wouldn't make sense.

I forgot to say that to be careful with switching from 1 to
both, to 2 positions on the switch when the engines running.

Not all switches keep the circuit closed when doing this,
a simple way to check this is to switch on a cabin light, or
something like it, and slowly go thru from "off" to "1", then "both",
then "2". #If theres no interuption to the light, then it should
be safe to #do this while the engines running, but never
pass thru the "off" position.

The Hella marine ISO switch I run is no problem.

Sorry, David, you're right, but I thought it was a no brainer that
all the negatives be connected to the neg terminal, on either battery,
(as they are both connected to one another anyway), or to #a
negative bus set-up, which , I think, would be the preffered option.

Connecting the bilge pump directly to the start battery simply
removes the potential for any wiring, or connection failure that
may happen at a time when you REALLY NEED the bilge pump
to work, ie:, when the hull is filling with water.

This may sound a bit controversial, but I don't run a fuse on the
bilge pump, either, for exactly the same reason.

Harry..

[Bosunsmate]

Thanx Harry and everyone else who has posted here you just answered all of my unasked questions.......

I am now well educated in this regards......What a wonderful site we have :D

[HarryO]

G'day Boz,

Yeah, good point.
Motor vehicles are different, and are set up differently.

Cars running proper dual battery set-ups do so thru a VSR,
with alternators running regulated output @ 65 amps plus,
charge being supplied via a dedicated field wire @ 4mm max.

The VSR, will direct charge to the start battery until full, then
direct subsequent charge to the 2nd battery.

The output on an outboard has to supply a much smaller charge
via much heavier cable, so there is some loss.

The 240v 4A home chargers peak output is 2.5A, and will supply that
until the battery reaches approx 70% full, then trickle charges the
balance @ 1-1.1A.

They do not reach "peak" very quickly at all.

To charge a brand new MFM70 marine battery on one of these
DOES take 2-3 weeks until it is FULLY CHARGED.

For a quick charge, we'd use a 50A PRO charger, set at 10A, to put enough charge (overnight) into them to sell, however,
we'd always advise the customer as such, and to
trickle charge it for a few days at home if possible.

My boat batteries are 660CCA, @ 160a/h.

Using your figures of 4A output to reach 110A, will require
27.5 running hours, in this case @ 2000rpm.

I know blokes that don't achieve that in a year, let alone 6 months.

I read that the average running hours per annum by a rec boatie
is approx 40 hours.

When I take all things into consideration, to run one battery as a dedicated start battery, and the second as a backup, with the
majority of the charge directed to the start battery, and, of course,
if you know that the battery is full, and you've got a few trolling
hours to do, then its easy to switch over to "bat2".

My initial response was to, "when do you run in "both" mode",
to which my answer was, and still is, NEVER. ;) ;)

[finga64]

Hi krazy, and Pete, and all.

Firstly, heat is a problem..


With the exception of the bilge pump, which should be
connected directly to the start battery, via an
auto/ override switch.


Harry

Yes Harry is quite right. If there is heat in the switch there is definitely a problem in the making. Heat is a symptom of a high resistance joint (ie bad connection or joint) or caused by a too low of a current carrying capacity of the switch (ie switch too small). Voltage drop and radio interferance are other symptoms of a problem about to happen.

And sorry Harry but I have to disagree with the bilge pump connect directly to the start battery. What happens if the start battery fails. Your b-ggered.
And people Alway, always use a fuse on every electrical accessory in the boat. No matter what, no matter what anyone says. The plain truth is if a short happens in the bilge pump or any accessory high currents are evident and where high current occur there is always heat. Where there's heat there can be smoke. Where's there's smoke there can be FIRE
I know. I used to investigate electrical fires for Northpower.
The manufacturers say to use a fuse, use a bl--dy fuse. Simple.
Explain to the insurance company when/if they investigate a fire and find no where a manufacturer says to use one.
If your worried about failure of the bilge pump or wiring bung 2 or 3 seperate pumps in. One on each battery and one connected to the common terminal should be better protection then 1 with no fuse. That's just crazy.
The reason a fuse is used is to protect people and in this case your boat from a potentially dangerous electrical breakdown which may be caused by a short or high currents in the electrical accessory by means of isolating (ie the fuse blows) the offending item from the electrical system. The fuse is not there to protect the electrical accessory (in this case a bilge pump)

Voltage drop is not a problem if the right sized cable is used. If the cable is big enough a battery can be put up the front with everything else down the back. The right sized or bigger sized cable is the answer to voltage drop. No point in having two batteries if only one can start the motor/s. Just use the right size cable so you have the ability to use either/both batteries to start the motor/s.

PS Use a bl--dy fuse...the only thing in a boat without a fuse is the starter motor. Everything else NEEDS a fuse not for the protection of the electrical item. A fuse is for the protection of YOU and in this case your boat.

PSS Use a bl--dy fuse if you didn't get my message above.

Come on you boys who know better, please back me up on this point before somebody gets hurt.

[blaze]

All circuits should be fused.

[Alan_L]

Finga and Blaze are spot on. It really is a no-brainer. Protect every circuit with a fuse or circuit breaker that is suitable for the wire size or electrical component. No good fitting a 30A fuse when the wire size or component is only rated at 10A. Not a pleasant experience watching a harness burn when you're 50km out.

IMO a good quality auto resettable circuit breaker would be more suitable for a bilge pump as some fuse holders are susceptable to corrosion, and with corrosion you will get voltage drop, which will greatly affect the performance of your pump.

Being in the electrical trade for a "Long Time" I've seen some shocking ::)things happen. I have also investigated many automotive equipment fires. Many were caused by a lack of circuit protection, mainly by unqualified people "Having a Go"
One of the worst was live.22 shell used as a fuse in a Fiat car using the european type fuse. When I asked why? they said because it fitted. It required a total rewire.

Always protect your electrical circuits. Fuses/circuit breakers are very cheap insurance.

Cheers
Alan

[HarryO]

:) # :) # :) # #:)

I knew that would be controversial.

G'day finga,
you're right about the heat issue, and in this case I think its
more to do with the pos/neg being connected at the iso switch,
closing the circuit, not a "high resistance point".

Don't understand the comment, "no point of having 2 batteries
if only one can start the motor(s)".

how did you draw that conclusion? :-?

If you read the post properly, with the iso switch fitted
properly, either battery can be used to start the engine if
required.... simple, really. ;)

Voltage drop may not be a problem with domestic / industrial supply,
where power is diverted from a much larger supply, where the
HEAVY cable, if I remember rightly, has to be rated @ 20% above the maximum VA to be carried.

But with a 12volt portable / limited storage system, ie, car battery, you do LOSE 1 VOLT WITH EVERY METRE OF STANDARD BATTERY CABLE.
Thats why engine batteries are down at the transom, and batteries for
trolling electric motors are fitted at the bow.

What we have is a battery(s) supplying 12V cranking power via heavy cable, (100A plus) then a rectifier returning 1.5- 8 A to the battery
(or batteries, if you run in "both" mode) via that same heavy cable.

My whole reasoning for the initial post, was the syphoning of power
by the weaker battery from the better battery, thus creating 2
"below par" batteries, and the capacity of the engine to divy up
the meagre amps created, back to the 2 batteries, and the
time it would take to do so.

The equasion would change if there was a dedicated "field wire"
from the alternator/rectifier running back to the batteries via a VSR.

For the record, I do run 2 bilge pumps, one wired the standard
way (fused) via a helm switch, and a 2nd wired directly to the battery
as previously described.

I am aware of the potential hazard of the 2nd pump, and I nearly
didn't type that bit in, as I knew it would get jumped on.

Again, for the record, I will heed to common sense and wire in
an inline waterproof fuse holder to that pump, and urge all
other members to do same when wiring in accessories.

Regards, #Harry.. :) # # :)

[finga64]

Gidday all,
Not running a fuse is not controversial. It is down right dangerous. If I had a bilge pump put in my boat by a professional and it came back with no fuse or circuit protection (thanks Alan for mentioning the other methods :)) it would be a case for consumer affairs. I wouldn't even take it back to the dealer to get an excuse. It (not using a fuse) is not recommended by any pump manufacturers, it is not recommended by any boat manufacturers and if something did happen and the insurance company found it I doubt if they would pay a claim. And that is stating the facts very politely.

If anybody puts any accessory in their boat use a fuse or a circuit protection device. If your worried about total failure of the electrical system put a manual bilge pump in. NEVER CONNECT ANY ACCESSORY DIRECT TO A BATTERY, NEVER.

Harry mate I think you said the bit about not been able to use the second battery. See below. In my books damaging a starter due to voltage drop is the same as not been able to use that particular battery to start a motor



You know, you lose 1 volt for every metre of standard battery cable.

Using the 2nd battery to start the outboard is starving the
starter motor of full available power.

It may sound like nitpicking, but the quickest way to kill an
electric motor on, a say 15cfm compressor, is to run it off
an extension lead.

#
Please tell me if I have mis understood what you are trying to say but that's what it says.

That's just plain garbage about extension cords. If the extension cord has conductors of suitable size to counteract or limit voltage drop you can theoretically run a 15cfm compressor hundreds of metres away from the power point. How do you think you can power a house 100's of metres away from the electricity suppliers mains or run irrigation pumps or anything 100's of metres away. You work out the appropriate size cable taking into account the load (current draw) of the item whether it be a house or a lightbulb and the distance the item is away from the power source. The appropriate size cable keeps the voltage drop to acceptable levels which in 240/415 volt wiring is a maximum of 5% of supply voltage.

DC voltage works in pretty much the same manner as AC voltages where voltage drop is concerned.

Voltage drop is a measured quantity not a made up figure. It is calculated by a formula taking into account the current going through the cable, the size of the cable and the length of the cable.

An example is 6mm cable I use in mining situations has a voltage drop value of 7.0mV/Am. or millivolts per amps used mutliplied by the length of the cable and if you go up a size in cable to 10mm the voltage drop is reduced to 4.0mV/Am and if I use 16mm cable the figure drops down to 2.6mV/Am.

So the theory of 1 volt per metre is an old wifes tale

As an old broken down Electrical contractor with over 22 years in the trade (we also work in DC as well) we have to work out the voltage drop, we cannot guess. Not unless we have good public liability.

Voltage drop is a bit like water going through a garden hose. If you have a normal 1/2 inch garden hose that's 100m long and turn the tap on fully you get a dribble out the end due to internal friction of the hose. Use a 100m 1 inch hose and turn the tap on full you get a hell of a lot more water out the end. In both cases the flow and pressure is the same at the tap.

Batteries are usually mounted where they are because of the cost of the cable or the ease of installation. You can put batteries anywhere if you want to buy the appropiate sized cable to limit the voltage drop. And realistically even the largest outboard doesn't use that much current to start compared to my old V8 Kingswood and the battery for that is in the back and the cables to the starter are about 6m long.

I am not trying to scare people from putting in a duel battery system in their boat. Quite the opposite. It's not rocket science by any definition.
Get a couple of good batteries, get a good switch and get some battery cables and bung them in. If your not sure about cable size ask someone.
As a rough rule of thumb, if you can buy a premade battery cable from places like Repco in the length that suits you then I wouldn't worry about voltage drop. Some smart cooky has already worked it out for a fairly large motor.
The local autosparky will fix you up with the cables made to the right length taking into account voltage drop if needed. Easy as that. The hardest thing to do is deciding where to put the batteries and switch.

I'm still not convinced duel batteries are needed in a lot of cases in boats. A 4m tinny running up and down the Richmond river that's in good serviceable condition and has a good battery really doesn't need dual batteries other wise manufacturers would put them in at the producton stage.
It's a bit likes cars on the road. A patrol wagon taking the kids to school and goes to the shopping mall and maybe tow the trailer to the tip doesn't need duel batteries but people taking their car, 4x4, bus,truck etc into the bush/ outback need a duel battery system. Hell I even had duel batteries on the Beemer bike when I went around Aussie (had spare wheels too just in case :))

Posters of information on this site should remember that people get information and use information from here. Contriversy is not needed. Accurate information is needed.
I would hate to say I don't use circuit protection and somebody acted upon that information and then had an accident directly due to the information given by ME. Bad carma.

Cheers Scott :)

[ahoj]

Please ask FINGA to draw you a diagram he knows all about sparks. I am sure he will oblige.. this subject is creating confusion and can cause broblems...


Ahoj

[HarryO]

Downright dangerous? Yeah, ok, then.

I would love to hear the reaction of comsumer affairs when you ring em
and declare that "they didn't fit a fuse my bilge pump!!''
"don't worry, we'll send out the troops, and arrest em!" #;D #;D

I admit that I shouldn't have writtem that, and I regret that I did, and
I retracted it accordingly..

Although I should add that I've had the 2nd pump wired directly, and
independantly for over 8 years with no problems whatsoever.

But, I do realise that its not an excuse, and have acknowledged that.
If you want to make further issue out of it, then thats your call...

Using the 2nd battery,if wired with long length of std cable, does restrict full available power to the starter, but I never said you can't start with it,
Mate, you can twist that around as much as you like, again, thats
your call...

Plain garbage about extension cords???
Ring your local compressor manufacturer and ask the question,
will they warranty an electric motor on a 13cfm and above compressor
if its run via an extension lead??? # #Go on, do it.

We found out the hard way......

Never once seen an extension lead with conductors fitted.
Where do you buy these?

My sparky tells me you lose 1 volt with every metre of cable, and as he
owns the largest independantly owned auto electrical workshop on the n/side, for over 35 years, I hope you don't mind if I take his word on that.

ON the subject of dangerous, how do you figure its ok to run duals on
a fourby when offroad, but not really necessary on a boat?

Ask subzero how many rescues have they done regarding flat batteries?

Harry...

[finga64]

Plain garbage about extension cords???
Ring your local compressor manufacturer and ask the question,
will they warranty an electric motor on a 13cfm and above compressor
if its run via an extension lead??? # #Go on, do it.

Mate I fixed them and did insurance claims on them. I was an Electrical Contractor. The blame falls on the consumer because the manufacturer can not be sure how many extension chords have been plugged together. A single extension of 15amp capacity will run a compressor if it has a 15amp plug/socket on it and the wire/conductor is accordingly and suitably sized for the current and the length of the extension chord. That's why they call them a 15amp extension chord, but plug two together it will derate the current carrying capacity by more then half.

We found out the hard way......

Never once seen an extension lead with conductors fitted.
Where do you buy these?

A conductor is anything that carries current. A wire is a conductor. The guard rail of the South east Freeway is a conductor

My sparky (so you don't do your own work I take it) tells me you lose 1 volt with every metre of cable, and as he
owns the largest independantly owned auto electrical workshop on the n/side, for over 35 years, I hope you don't mind if I take his word on that.

So what he is saying is if the cable is 12 metres long zero volts comes out the end. Maybe he should go back to Tech for a refresher. Maybe you should remind him that by definition voltage drop is dependent on the length of conductor, the amount of current going through the conductor and the size/type of conductor

ON the subject of dangerous, how do you figure its ok to run duals on
a fourby when offroad, but not really necessary on a boat?

I was comparing the use of some 4X4's compared to other 4X4's ie the town cruiser compared to the around aussie tripper. Some boats need duals but there's not a hope in hell I'm putting duels on my tinny. I was trying to say if the boat is basically well maintained and the battery is in good condition there is no real reason for a boat (15 foot tinny with an electric start 30hp motor on the back) that has a sounder and maybe a gps to have dual batteries to have a days fishing in the Richmond river. It's a different story if your going offshore and have more electronics and bells and whistles then a Tricky Dick store.

Ask subzero how many rescues have they done regarding flat batteries?

And how many of these could have been prevented by having a good battery to start with. Not 1 or 2 dodgie batteries or wiring or charging system.
How many times have we heard the story about...."thought it would charge up on the way out"
Or "it's always a bit hard to start when it's hot". Sometimes even if you had Marshall battery truck sitting next to you the motor is just not going to start.

Well that's it for me. I've had enough of this waffle.
Cheers Scott

[krazyfisher]

ok well the batteries are no.1 730 cca sealed battery and no.2 is a 650cca.
yes a use fuses.
it needs to run
1.colour gps/chart plotter
2. colour sounder
3.vhf
4. cd player/radio
5. bilge pump
6. deck wash
7. nav lights
8. anchor light
9. 140hp 2/s

[ahoj]

Is there such a thing as multiple board with fuses and switch on-off---- say 10 unit
that can be mounted somwhere below or on a dashboard in a vacuum type -waterbroof box???
Come back FINGA --we need ya.....

Ahoj

[HarryO]

:o :o :o :o :o :o :o

No, Finger, I'm not an electrician, and never said I was...

Our business dealt with auto electricians almost on a daily basis
for over 20 years, and we soon sorted out the DUD tradesmen
with ATTITUDES, that KNEW EVERYTHING (yes, they're out there, folks) from the good operators...

The reminders from him came whenever he supplied
custom made STANDARD BATTERY CABLES for whatever application we
needed them for.
(and No, I would NEVER get repco to make these again, either)

Obviously, the 1V per metre is graduating, slowing down to a
trickle the longer you get (quote 12mm garden hose@ 100 metres)
(water in the pipe is a good analogy of describing current flow)

I x 15cfm compressor. 1 x 10metre 15 amp extension lead.
! x burnt motor. conclusion? SORRY, NO WARRANTY.

Read into that what you want, but I won't do the excercise again.

(In hindsight, maybe we should've used the guard rail on the
sth east freeway for a lead) ;D ;D ;D ;D

My apogogies to Krazyfisher and others, this thread degenerating
the way it has, it was not my intention.

Posting here should be to help Krazyfisher, not to belittle other
contributors with their indignous attitude.

The chance to really help Krazy with his problem has now
been compromised.

My fellow member may harbour a grudge, possibly from being
(politely) made aware of some irresponsible and dangerous info that was posted on another thread, so it seems a bit ironic that the
reminder of posting accurate information was made here.

90 odd % of the members here seem to be reasonably inteligent, and
would take information posted here, or any site, as a perspective,
or opinion, not as gospel.

Keep smilin', stay happy.
Harry...

P.S.
Krazy, you should talk to an auto sparky, preferably one with good
marine experience, take your plan in, and he will guide you in
the right direction..

[krazyfisher]

harry
I did go to an auto sparky who has done a number of boats and the way I first did it was the way he told me to but........
just because you have a trade does not mean you know what your talking about...... it should ! but it it doesnt always

[krazyfisher]

well I have re-wired it and will see how we go no heat that I can tell and everything seems to work
thanks to all that posted it was all a help thanks again

[familyman]

Basically KF when it comes down to good electrical practice it means ALL joints are soldered then insulated,crimp lugs and screw connectors are a no no.
Water flow is the standard analogy for for year 1 electrical trades ie electricity behaves exactly the same as water in terms of flow and resistance,just the two dont mix. ;)
Excuse me if this has already been said as snarly threads dont attract me.
Looking at your list of gear you will need two types of batteries,a high cca model and and a LARGE deep cycle type.The high cca model will produce high starting current for short periods ie starting loads for the motor.The deep cycle is designed to give low to medium current for a long period ie overnighting.
I have a dual setup on my half cab and use a similar system with a battery isolater on the positive side only.You can get switches that isolate both pos and neg if you want.You need fuses if you want any of your gear to survive any kind of electrical hiccup.Fuses are designed to protect the wiring and equipment-thats it -nothing else.Circuit breakers have the same function as fuses.
The idea is that a short will blow the fuse and not turn the wiring into a molten mess.
Heat in a wiring system is caused by two things- a high resistance joint ie corroded terminals or a loose connection,and undersized conductors being forced to carry too much current.Dont do either of these and you'll be ok.Do get the best stuff you can afford ie switches, fuse panels,premade cables for instance.Do go to every effort to make good joins on your wiring.
Ohm's law is the basic electrical rule for direct current ,power =volts x amps.Volts is always (hopefully ;)) about 12-13 volts so as the power goes up so does the current which is what creates the heat.Go back to the water analogy - a big pipe will carry more than a small pipe at equal pressure(voltage is electrical pressure) so if you have a big load you need a big cable.Do not compare wiring in a house with wiring in a boat or car as the two are VERY different .A house uses smaller wiring because the pressure (voltage) is MUCH higher which uses less amps(current) to produce the same power.
Sorry if I have confused you KF but if you can understand the basics then the rest is alot easier to work out.
If you want any more info pm me but if you dont want to do the job yourself then go to a BOAT electrician not an auto elect who may not be up to date with modern power managment systems....a whole different can of worms :o
Hope this has helped.
cheers jon

[wayne_cook]

just to keep the discussion going guys. :)

i read one part about the importance of fuses. i agree.

here's my query

how come i have never seen any boat with the starter motor cable fused.

surely if a short took place in this size cable (aprox 16 mil) which is not fused at least close to the load side of the battery it would cause signifigant damage.

if it is so important (i think it is) to have all apliances fused why not the one that can cause the most damage? :-?

[HarryO]

Hi Krazy,
yep, know what you mean....

Jon, great post... Thanks

Bear, the circuit is fused, not on the heavy cable, but
on the secondary ignition circuit, (key switch-control box/starter motor)
with a "fusable link" fitted under the engine cowl.

Its a good "spare part" to include in your onboard kit.

Regards, Harry.

[ahoj]

For starter you will need a fuse--like 200 amp plus-- the surge of power to start is too high .. Cars do not have starter fuses

Ahoj

[wayne_cook]

ahoj
i realise how heavy the fuse would have to be and how $$ it would be but surprises me its recomended for all other circuits but the main one. A short on that cable would probably draw 200+amps.
harryO
how could that fuse protect a short in the cable mentioned? Thanks for the spare part advice ;)

[Grand_Marlin]

Lol... thanks for answering my question... ;D ;D

It does make sense to run one battery or the other ... not both.
Again... I always keep good, fresh batteries in my boats... but you never know when a new one is going to drop a cell.

I also didnt know about the off position whilst motor is running.... not that I had ever selected "off" while running.

I had forgotten about this post, and obviously, just looked it up again.

I thought it was only Mantaray and Myself that argued on here!!

Harry, I share your concerns with the bilge pump. From experience, when the proverbial hits the fan, the last thing you want to be worrying about is the fuse blowing because it is too light.
You will notice that on the majority of pumps, they recommend a fuse, but rarely do they state what size..... thats useful....

I set my bilge pumps up for the maximum rating on the wire - i.e. 6mm tinned copper, I use 30amp fuse. I figure that this gives me the best chance of the fuse lasting if really needed, and no chance of a fire.

Realistically, there should be no need for a fuse to blow, unless there is a problem in the motor, or possibly a chaffed / shorted wire.
In either of these cases, a 30amp fuse will readily blow.

Circuit breakers are a good option, but rarely do they get used on smaller boats... maybe us installers should have a "mind shift" and start using and recommending them more.

Cheers

Pete

[Alan_L]

Brrbear, it's not common practice in the automotive industry to fuse the main battery cable, although I have seen it done on certain underground mining equipment.

If you do fit a fuse then you have 2 extra connections to deal with. With EVERY connection you will get a certain amount of voltage drop over the connection (not good), if the connection does get corroded/loose then you have the potential for the motor not to start.(this will only happen at the worst time as we all know). It also has the potential to pop a rectifier diode if the circuit went completely open as well as destroy radios/electronics.

When the main battery cable becomes open circuit the alternator voltage will rise very quickly as the regulator has no reference voltage to check. Voltage can rise to 50 to 100 volts or even higher until the rectifier is destoyed. However some new alternators do have protection against this .

Starter motors do not like low voltage. Low voltage is the biggest killer of starter solenoids, it can also lead to the solenoid contacts welding themselves together causing the starter to stay engaged. This scenario has the potential to cause a fire.

IMO I would not fit a battery cable fuse, just ensure all your cables and terminals are in good condition and have protection against chaffing etc.




Cheers
Alan

[Magneto]

:-X :-X
Tony-m
I apologize for not returning sooner.
Yes the charger is connected to tthe one battery.
Its the same as when you have a bad battery, the good one will loose charge until they are even.
Cheers 8-)

[Drunken_Pirate]

Great thread....Has really given everyone something to think about.

Seems to be some good leanings here. #

I do have a background in marine electronics and will be the first to admit that some of the "expert" trademans out there have a lot to be desired. # I always do my own work and have been told how anal I am in doing it right. #

I will summerise what I have read and seen which may be of help:

1. Always have a form of protection against a short cct (This can be a fuseable link, circuit breaker or auto resetting circuit breaker{these are great but protect from water})

2. #If an "Emergency Override" is required (for what every reason you have :o) you could install a momentary switch to bridge the fuse/cct breaker. #This type of switch requires you to hold it on to operate so limits risk of fires etc. #Before I get posted to death, I state this option as it is better that the "Fag Packet Paper wrapped around the fuse" or "2 inch nail" trick which I have seen before.

3. #High resistance joints are the biggest problem in boating electrics. #Soldered joints are preferred over crimps. #I then generally smear some Silastic over the soldered joint and use heatshrink or wrap in elec tape to finish. #

4. #Hot components (switches crimps etc) means one of two things. #a) Something is drawing a lot of current or b) you may have a high resistance joint that a unit is trying to draw current through.

5. #Battery Selection - 1,2 or Both?? #My spin is to charge one battery at a time while at cruise and use the other battery while at rest (drift fishing or anchored with sounder/radio on). #That way you should have good charge to get you going again. #Both position is one I would use in a last resort. #Alternate which battery is the start battery each trip. #Have worked so far ;D

6. #Dont wait until the night before to look after your batterys. #Batterys dont like long perids of inactivity. #If you have a dual set up in your fourby (as I have) you can give a tickle by putting them in the truck for a while. #Trickle charging is OK, but they need a work out every now and then.

7. #Check you battery posts for corrosion. #Very common problem area. #Also look to see how many "add-on" crimps have been added to the wingnut as this can become spagetti junction abd leads to high resistance joints, arcing, and is a cause of boats not starting at the ramp. #
I have heard the old "But I tested the battery by turning the radio on when I was home" comment but then found 7or 8 crimps accompaning the starter lead on the battery post in a pile of corrosion product which prevented the engine turning over.

8. #Get behind the Dash. #As with the comments in point 7, addons and quick connect couplings are the cause of most elec faults. #It it looks like a mess there is a good chance that some backyard work has been done without thought to the longivity of the installation. #

9. #If you see any of those quick connect fittings (you put the two wires in, and then squish a metal bit in with pliers and close a flap??) get rid of them. #Poor quality Autoelectricians use them, especially when fitting trailer plugs in cars. #These are one of the main sources of intermitant faults.

10. #Tidy up you wiring. #Less chance of it getting caught up on something. #Coventry's or other stores sell split tubing which is really good to get all the wires running down to the stern in one package. #Buy a big bag of zip ties and go to town!! #No more catching your gaf on the wires hanging down in the side pocket ;D


Bottom line is, if you have a tidy installation you are less likely to have problems. #If you do have problems they are easier to find and fix. #Remember in most case faults can be found visually.


I have heard this some of the new four strokes (suzukidf175)have dual charging ccts so you charge two battery's independantly? #Does anyone know anything about this?

Regards

Phil

[steveg1100]

Harry you should know that what finga is quoting on voltage drop etc is fact. A lot of the tradesmen use a rule of thumb voltage drop because that was what they were taught and they probably don"t even know what the voltage drop of the cable they are using is in mV/A.m. Thats fine, in simple wiring rule of thumb usually works fine. Finga you were probably getting a bit too technical for them.

Cheers guys. Keep on Boating.