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Would it be ok to run 2 12v 4A SLAs in parallel to give 8A and connect in series with a 12v 8ASLA for 24v 8A? Answered

I'm building an electric go-kart from a bustup mobility scooter and the problem is this. I don't have cash around to buy batteries but do have 2 x 12v SLA @ 4A and 1 12v SLA @ 8A. Would wireing them in the diagram below work OK. Part of me is saying I missing something.

The reason I need 24v above 4A is to power the S-Drive controller & 24v Motor. I'm not sure of the the motor ratings as the label is damaged and can only make out 24v Brushed. I'm also using the S-Drive as I have 3 of them lying around, they're programable and can also handle upto 45A.

Any advice would be greatly apreaciated as my son is excited about the project as at the moment its just a battery issue.

Discussions

If you want to get it going for now and upgrade the batteries to two 12 volt 8 amp or 1 24 volt 8 amp later when you have the money, it should work.

Just one question when you say 8 amp, do you mean 8 amp hours?

Sorry been busy latley. I've only just realised what you meant by amp hours (Slow moment). I was suppose to put one 12v 8Ah SLA and and two 4Ah SLAs.

In Addition I'm a bit confused by the 8Ah. Looking closer at it, the text is a bit worn off but can just make out the following info printed on it :

12v 8Ah (10HR)
8.4Ah(20HR) / 135A(CCA)

I've been going by the 12v 8Ah marking.

If I have it right (10HR) and (20HR) is charge time or charge rate.

12v 8Ah (10HR) means 8 amp hours on a 10 hour charge.

12v 8.4Ah (20HR) means 8.4 amp hours on a 20 hour charge.

Or

12v 8Ah (10HR) it means .8 amp charge for 5 hours charging.

12v 8.4Ah (20HR) it means .84 amp charge for 10 hours charging.

135A(CCA) means 135 cold cranking amps, it will allow you to draw 135 amps for one minute to start a gas engine or something like a starter.

Right, that explains it more. I've been charging the bateries using a 1amp 15v charger to be on the safe side as I wasn't 100% sure on the charge rates on all the batteries individually just to be on the safe side.

I worked it out as 8hrs for the big SLA and 4hrs for the two small SLAs. Hope I worked it out right and not done any damage.

On Downunder35m's comment, the S-Drive controller prevents it being used before the safe operating limits are reached. However, my other generic 24v controller, which is used for testing, does'nt have this feature.

To be truthful I use a car trickle charger 6/12 VDC 1.5 ADC on my SLA batteries. Works for backup batteries on my UPSs and power inverters.

The generic drive may be easier to work with, for the other S-Drive I would go with a single 24 volt battery.

no it would not be ok.

It is unfortunately not a good idea, although its theoretically possible. IF your batteries were brandnew, and identical, its doable, but unless your wiring is identical, you'll find one of the parallel batteries taking the bulk of the load.

I need to agree here.
A mix of different batteries like this won't work in the long run.
There is always losses and different internal resistance which will deplete some battery much sooner than the others.
Once the battery is below safe operating limits it will be destroyed quite quickly.

I forgot to add, you can also get circulating currents, which REALLY bugger things up.