mielke avatar image
mielke asked

How to determine absorption/float/equalisation voltage

Hi guys

I recently bought myself a BlueSolar MPPT 150/35 CC to use in combination with a battery bank, consisting of 2x 6 V gel lead acid batteries (for golf carts): Golf Cart TAB Motion Gel Batteries ( ).

Now I ask myself the question how to determine the right determine absorption/float/equalisation voltage for this type of batteries. This link ( ) gives like a general rule of thumb for lead acid batteries: 2.25/2.4/2.55 V/cell ==> 13.5/14.4/15.3 V

I found there's a pre-installed program for forklift batteries: PzS tubular traction (1), 13.8/14.9/16.7 V. As forklift batteries are more or less similar to golf cart batteries and these numbers more or less look like the ones I found above, I intended to use this mode. However, I'm not quite sure if the batteries are tubular, and if that even matters.

Is there any other (experimental) way to determine these voltages?

Also, I read that it is not advisable to equalise gel batteries, is this right? Why not?

Thanks in advance!

battery chargingvoltagefloatequalisation
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Mielke. Your batts won't be tubular, else they'd say so.

Being gels, leave 'equalization' turned off (yes that's right, they don't need it, and may destroy them). A 'forklift' setting is probably at the aggressive end of charge algorithms, but it depends on your daily cycle demands and how fast you require they be charged. Impatience may cost in battery life.

With gels I'd go easy on them, as they won't appreciate being 'bubbled'. Perhaps a 'stock' Pb algorithm with 14.3V Absorb and 13.5V Float set would do. Leave temp compensation on, so those V's will vary a little in practice.

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mielke avatar image mielke commented ·

Thanks a lot! The thing is that it will probably not be used too heavily, maybe some context.

Every year we go on a scouts camp where we'll use it for only two weeks to power some off grid applications (refrigerator, a radio, some phones and lights). Usually we've got plenty of sun, but the batteries are dimensioned so that we can bridge at least one day without/with very little sun. Do you suppose this would change anything to your suggestions?

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JohnC avatar image JohnC ♦ mielke commented ·

No, I'd say the same (others may differ, and that's fine too).

The other 50 weeks may actually require more attention. Best stored fully charged, with perhaps a Float dose of 13.2-13.5V for a day or two every month or so. If they hold 12.5V or higher in storage, then they should be ok for the next year's camp.

'Be Prepared', hey. I wish you and your Troop the very best. I was there many years ago, nowadays my motto is 'Stay Charged' (in the electrical sense. :-) )

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