Dual batteries (for electric motor), can they be charged off alternator ????

[Aeon]

I'm fitting a 74lb motorguide to my new 5.2 savage (which is currently being fitted out) with a 24v dual battery (deep cycle) set up.

The mechanic tells me that I cannot have the system charge off the alternator.

However, I have friends with dual battery (deep cycle) set ups that are rigged this way.

I'm having a 115 mercury 4 stroke fitted, and the mechanic tells me that it has a 12v alternator and that this is impossible.

Can anybody shed some light on this for me. Is it possible or not ? And if so, would it be difficult to retrofit?

Cheers for any help.

MICK

[Hamish73]

the only way would be to have them connected in parallel (12v) for charging whilst underway, and in series when using the electric to get your 24v. This would require a elaborate array of high current relays and/or switches
Only issue I can see is alternator output, as you will effectively be charging 3 batteries at once and if the electric mnotor batteries are approaching flat the current draw would be high.

[NormC]

One way is to fit an inverter to convert the 12 Volt output from your alternator to 240 Volt, then run a smart charger to charge your 24 Volt batteries. There are of course safety issues to consider, having 240 V on the boat. Mounting the inverter as close as possible to the charger (to limit the distance the 240 V cables run is one simple measure.

This is a method used in some caravans (albeit charging 12 V, but no difference in concept) to overcame the problem of voltage drop over the long distance from vehicle engine bay to van batteries.

Norm C

[Steve B]

MICK,

YES YOU CAN!!!

BEP puts out a converter (I cant think of the exact name...something like voltage sensitive relay???..anyway its in the BLA catalogue) that charges your cranking battery first to max then alternates between the 2 deep cycle batteries at 1 min intervals (the batteries remain in the 24volt setup). They cost from memory about $280 or so...only a small unit.

I have one set up on my 90hp Optimax (has 60amphour output charging) I do the majority of fishing at Monduran with a 10-15 min run up and back the dam.....I have put my battteries on charge twice in 2 years, That was because I used the electric lots in the ABT barra events, and the dams were alot smaller, hence less outboard running time....well worth the investment.

I will post the exact BLA code if I can find the info
cheers
Steve

PS found it!!! BLA Code 113655

Google BLA (boating leading accessories) type in that code number in search and you will find what your looking for. I had mine fitted when I bought the boat. I noticed the price has gone up a bit.

[Lovey80]

Steve, I am looking to put a 55lb Water snake on in a couple of weeks. I have only a 50hp suzuki and its going in a 4.3m Webster CC. Do you think I will need dual batteries? Im not sure what voltage the watersnakes are but would like to set it up so I have to charge the batteries as least as possible.

Cheers

Chris

[Steve B]

Steve, I am looking to put a 55lb Water snake on in a couple of weeks. I have only a 50hp suzuki and its going in a 4.3m Webster CC. Do you think I will need dual batteries? Im not sure what voltage the watersnakes are but would like to set it up so I have to charge the batteries as least as possible.

Cheers

Chris

Chris I am far from an expert on electrical stuff, but a 55lb watersnake is a 12 vt setup, IE only need one battery....the bigger motors require 24v setup (2 batteries with a lead running from neg to pos and motor cables running off the other 2 terminals...that makes it run in 24v)..

My neigbour has 55lb watersnake and it can run all day on 1 X 85AMP hour battery.

I think BEP (Same BLA catalogue) has a VSR which does the same thing except for 12vt (single battery), charges the main cranking battery first then switches over to the single 12v battery for you electric....and its heaps cheaper...thats the way I would go.

The output charging from you outboard is important....if its minimal...then it may not be worth it.....I figured with 60 Amp hours output from the Optimax (heaps) why waste it....saves wasting power at home charging batteries, and easier too.

You can run 2 batteries in line as a 12 volt formation...I think (someone correct me please) you run a lead from pos to pos, and a seperate lead from neg to neg...then hook up you motor leads to 1 of the batteries as per normal.....I doubt you would need to do that if you got a good, say 130amp hour deep cycle.

As I said, I am far from an expert and I hope someone can add, or correct me if any info is incorrect.

cheers Steve

[NAGG]

Correct me if I'm mistaken ........ but from what I have heard - Trickle feeding a deep cycle battery will diminish the performance over time:-/

DCs are meant to be discharged ( not completely) & then recharged to full capacity

Chris

[Hamish73]

The unit that Steve was talking about which will do the job.

http://www.bla.com.au/index.php?fn=productView&dId=1&id=9918&eId=10&actual_dId=79&sId=b163b7ca50da38f1366649d0550dbdc8

[Aeon]

Thanks for the input fellas.

I've faxed to the mechanic the specs for this charger. He has spoken to the mercury tech who gives it the nod. However, he tells me that he is unable to use deep cycles with this system (I see that's what you use Steve?!?!) and he will use regular 120 amp/hr batteries instead. He believes that the trickle charging would therefore not be an issue although I would need to run the motor from time to time to keep the dual batteries topped op.

I can't see any problem with this.... but then again I know sfa about it !

[TheRealAndy]

Correct me if I'm mistaken ........ but from what I have heard - Trickle feeding a deep cycle battery will diminish the performance over time:-/

DCs are meant to be discharged ( not completely) & then recharged to full capacity

Chris

Trickle charging wont have any performance on deep cycle battery, so long as you dont overcharge the battery.

[Hamish73]

Trickle charging wont have any performance on deep cycle battery, so long as you dont overcharge the battery.

X 2

This method is not trickle charging anyway. The battery is being connected to the 14v alternator output, so you would class it as fast charging. I'm curious to know why this system isnt suitable for deep cycle batteries. IS it the 1 min on, 1 min off switching that is the problem?

Solar powered houses use deep cycle batteries on trickle charging and it doesnt seem to do them any harm

[Steve B]

X 2

This method is not trickle charging anyway. The battery is being connected to the 14v alternator output, so you would class it as fast charging. I'm curious to know why this system isnt suitable for deep cycle batteries. IS it the 1 min on, 1 min off switching that is the problem?

Solar powered houses use deep cycle batteries on trickle charging and it doesnt seem to do them any harm


yeah agree with you Hamish, I have a 10 amp trickle charge, had it for about 10yrs and it has never wrecked a Deep cycle battery in previous boats.


Mick

My biggest concern would be the reccomendation by your mechanic to NOT use a deep cycle on an electric motor...cranking style batteries are not designed to be drawn right down then charged up again like a DC battery are.

All I can say is I have the set up with 2 x Deep Cycle batteries and it hasnt stuffed them in 2 years......and these are cheap batteries too. But saying that, its a high output charger. From what Hamish describes it sounds like your motor is OK for the job....I would go against his advice and get DC batteries.

Steve

[NAGG]

Trickle charging wont have any performance on deep cycle battery, so long as you dont overcharge the battery.

Maybe its an issue with AGMs or GELs ./..... cant remember where I heard / read it

[rc@hinze]

If you are going to run batteries off the standard charger on your motor they need to be lead acid or flooded type batteries. You cannot charge GEL batteries off your motor charger/alternator. I believe this is the same for AGM batteries.

I have just been thru the exercise recently and purchased a US made Trojan Lead Acid deep cycle battery for charging off my Yamaha. Its130Ah, can supply 15 amps for 7 hours and has 820 cc (cranking amps). It weighs 32kgs. This does my house electrics, motor starting and transom electric.

Up front I have 2 GEL batteries for extended bow mount electric use. These are only ever charged off a high quality smart charger. If I go away and need a to charge via a generator the smart charger requires a full sine wave generator.

I am a sparky by trade but have never had alot of experience with 12 volt DC stuff. I have a great marine wholesaler I buy from who supplies electrics to major boat manufacturers and they give me all my technical advice.