Gel batteries and lead acid batteries on line?

[foxx510]

I stuck this in another thread but it's useful info http://www.landiss.com/battery.htm

[driveon]

Hi Fox, I’ve seen this document before and there is some good info in it, but did you see the dates at the bottom of the page.

Not only has lots charged since that was written but ironically, some of the suggested improvements have been adopted.

For instance, Land Rover Discovery 3s have continually adjusting alternator voltages that vary from 13.2 to 15.5 volts, all controlled from the vehicle’s charge management system.

Other vehicles are following suit but the criteria for the charging system in the discovery 4 goes even further with the system able to recognise when the vehicle is cruising or coast down hill, at which point the alternator’s output is optimised to improve the charging of the cranking battery at a time when there is minimal power needed for the vehicle, thus improving fuel economy and reducing exhaust emissions.

[foxx510]

I assume the Disco charging circuit is designed around a calcium battery then with 15.5v? (also, doesn't that reinforce not using gel batteries in parallel? 15.5v would damage them for certain)

[driveon]

Hi Fox, actually, the voltage level seems more related to ambient temperature.

In Australia, after the boost cycle, 13.2v is common place whereas in Europe in winter, 15+V is common place.

Now, a little clarity here, are you talking about gel cell batteries or AGM batteries, there is a huge difference and personally, I wouldn’t use a gel battery for deep cycle situations but paralleling them still does not seem to have any adverse effects, and as posted, I would be very interested in hearing from anybody who has had problems, because to date, I have never seen nor heard of any form of reoccurring problem when paralleling any form of automotive batteries.

[TheRealAndy]

Hi Fox, actually, the voltage level seems more related to ambient temperature.

In Australia, after the boost cycle, 13.2v is common place whereas in Europe in winter, 15+V is common place.

Now, a little clarity here, are you talking about gel cell batteries or AGM batteries, there is a huge difference and personally, I wouldn’t use a gel battery for deep cycle situations but paralleling them still does not seem to have any adverse effects, and as posted, I would be very interested in hearing from anybody who has had problems, because to date, I have never seen nor heard of any form of reoccurring problem when paralleling any form of automotive batteries.

Interesting, I have used GEL Batteries extensivly for deep cycle use in remote weather stations with no issues before... I also have a bank of 4 Vision Gel Cells that I have been using for deep cycle use for the last 2 years to run my Waeco, and when I got them they had been in use for 2 years in a UPS...

For the record, I have seen a couple of exploded GEL cells, that were brand new and stuffed into a bank. Also, mixed banks of batteries in my experience dont last anywhere near as long as a banks from the same batch. But hey, I dont know what I am talking about so I guess it must be all crap.

Oh, and I nearly forgot, I used to design battery chargers for Lead Acid batteries...

[foxx510]

I'm talking about the standard gel battery that manufacturers recommend never taking above 14.4v. Something like a Sonnenschein that you might stick in a caravan and want to charge in parallel with the cranking battery(which I'm still not advocating).

[driveon]

I didn’t say gel cell batteries couldn’t be used, it is just my personal preference not to use them because they tend to be far more temperamental than either flooded wet cell or AGM batteries.

Again, this thread is about using dissimilar batteries in an automotive situation and there are some major differences when comparing this to RAPS and UPS set ups.

Also you will have no argument from me about using similar type batteries in a RAPS and UPS set ups and I too would NOT use dissimilar batteries in a RAPS or UPS situation, but because of the difference in the way an alternator charges as compered to a battery charger designed for charging and maintaining a battery or battery bank, as I would imagine is an area you would know better than I, the situation is different.

The point is, vehicle charging is a whole different kettle of fish.

[driveon]

I'm talking about the standard gel battery that manufacturers recommend never taking above 14.4v. Something like a Sonnenschein that you might stick in a caravan and want to charge in parallel with the cranking battery(which I'm still not advocating).

Fox, I’m not going over the same ground or anything like earlier in this thread but what do YOU perceive as being a problem with paralleling these two battery types in the set you mention?

[foxx510]

The problem I see is that car alternators do go over the 14.4v gassing voltage of gel batteries, thus damaging them(according to the manufacturers).

[sheridan]

I have an old 1992 70hp johnson my manual states i cannot use a maintenance free or sealed battery because my motor has a unregulated alternator so what would the concequences of using a sealed gel or maintenance free battery be .Would the battery explode or would it damage my altenator.

Geoff

[cormorant]

You can buy a rectifier/ regulator kit for em .

Sealed gels will bulge , overheat, gas and can crack cases and explode if overcharged especially with high voltage.

A lead acid of a reasonable size is what those old motors used and the basis of the thought was they were set up/ A small battery would boil its head off and damage the electrics on the motor.

[oldboot]

now lets not muddy the waters with issues that are ONLY maximum charging voltage related.
The choice of maximum charging voltage is a whole different discussion.

most small to meduim outboard motors do not have alternators in the conventional sense..... as prevoiusly mentioned..... they have magnetos with charging coils and there are a range of specific issues associated with them.

The unregulated charging circuits usulay found in small pull start motors are realy designed arround a battery of a specific size and type......if the battery is too small the terminal voltage will rize too high and stew the battery....if the battery is too large the terminal voltage will not rise high enough and the charging system will be too small to do meaningfull charging......another member here can testify to this.......

There are all sorts of funky charging arrangements comming thru in newer cars and the latest large outboards.........one would be wise to not fiddle with those....


some of the newer large outboards have two independent charging systems so they can independently charge two seperate batteries...........hmmm I wonder why that is.

cheers

[cormorant]

There are all sorts of funky charging arrangements comming thru in newer cars and the latest large outboards.........one would be wise to not fiddle with those....

Merc and those tiny batteries and alternators designed only for them.


some of the newer large outboards have two independent charging systems so they can independently charge two seperate batteries...........hmmm I wonder why that is.

cheers

Some have seperate system for the engine itself and injectors as they run higher voltages and a second system for the battery charging. The dual battery ones I know aren't a actual seperate alternator as such but a built in smart isolater system and are looking into computerised setting for different battery types. Yeah I wonder why they would go to all that trouble.

[oldboot]

Oh while i think about it.......there seems to be quite a bit of variation from manufacturer to manufactuere and even between different battery products of the same manufacturer......when it comes to required and permissable terminal voltages and charge characteristics.

When it realy comes down to it you have to check the specs of the individual battery product.

If you go onto the sonnenschein site and wade thru all the tech spec on their different battery products.........there are small but significant differences in what their different battery products will do and tolerate.

Multiply this across multiple brands, many of which do not provide the technical documentation like sonnenschein & the better brands...............you can easily have very different requirements in two different batteries charged in paralell.

And Oh yess I have seen sealed lead acids ( these were not gell) blow up like a balloon due to sustained over voltage charging......this was a + & - 48 volt back up supply for a 350 W amplifier........I threw a box full of very bloated looking batteries in the bin that day.
I have seen many SLA batteries spill their guts inside alarm panels due to poor regulation.

there is a great deal more to the question than yes or no, you can paralell charge batteries without consequence.

I have held in my own hand a reasonably fresh, partly charged 7AH VLRA sealed lead acid battery ........connected in paralell with a standard car battery with a standard car alternator running, charging at 13.8V..................with voltmeter and ammeter in circuit...........I have been surprised at the charge current thru the 7AH battery.........arround 12 amps and sufficiently concerned at the rapid temperature rise in the 7AH battery that I disconnected the jumper cable in a hurry.

This experiment convinced me that some form of current controll is required to charge small SLA batteries in paralell with car electrical systems.... even if it is only a resistor.

interestingly......an old nearly donnged, but still holding a fair charge, 7AH battery did not exhibit this behaviour.......nor was it capable of delivering as much current into a load......high internal resistance due to age.

cheers

[TheRealAndy]

I have an old 1992 70hp johnson my manual states i cannot use a maintenance free or sealed battery because my motor has a unregulated alternator so what would the concequences of using a sealed gel or maintenance free battery be .Would the battery explode or would it damage my altenator.

Geoff

An unregulated alternator puts out a much higher voltage. This basically causes the acid in you battery to bubble and release hydrogen and oxygen (called gassing). A flooded battery can tolerate this to a certain extent because you can add the hydrogen and oxygen back in as water. A sealed battery recombines the gasses and turns them back into water, however if a sealed battery start bubbling the gasses vent out and the battery dries out. Because sealed batteries cannot be maintained, you cannot add water. So when they dry out, you have to throw them away.

As a side affect, unregulated alternators do not put out a stable DC voltage, this can also cause an increase in heat which casuses buldging and can even cause expolsions in rare cases.