Thread: Interesting battery information

Hi Ron, batteries will “Equalise” ( for want of a better word ).

It doesn’t matter if you have two identical batteries or two totally different batteries, the results will be the same.

If you have a fully charged battery and you connect it, in parallel, to a very discharged battery, say with an SoC ( State of Charge ) of 10%, which is about 11.3 volts, the full battery will discharge into the low battery.

In this extreme case, the low battery will charge slightly but the bulk of the full battery’s charge will, putting simply, be used up by the low battery’s on going chemical reaction.

When ever you apply a voltage to a battery that is higher than the battery’s SoC, there will be a chemical reaction.

If the voltage is less than 1 volt higher than the battery’s SoC, the applied voltage’s energy will do little more than keep the chemical reaction going. ( this is still VERY important )

If the applied voltage is more than one volt above the battery’s SoC, the chemical reaction in the battery will cause the to absorb power. In other words, the battery starts to charge.

So while the full battery’s SoC is more than 1 volt above the low battery’s SoC, some of the current going from the higher to the lower battery will be absorbed as stored power but this will be very little of the capacity coming from the higher charged battery and once the voltage difference is at 1 volt or less, the power coming from the higher charged battery is simply wasted.

The “Equalise” of the two batteries voltage’s will not happen in an instant or even in a few hour but more likely take a few days.

Just some additional info. Where there is an applied voltage of less 1 volt higher than a battery’s SoC, two important things occur,.

1. The battery, while not being charged, it will not discharge either, this is how the float charge cycle of a multi stage battery charger keeps a batter fully charged without over charging it.

2. While any charge ( or discharge ) is occurring, a chemical reaction is occurring in the battery, so a battery will not sulfate, Sulfation is the most common cause of the early demise of stored batteries.

Hope this answers your question!

Originally Posted by p38arover

.....and being in the business, Hoodoo got them at trade!

Gotta love that name,,,
he was a big guy Hoodoo,, took me a while to figure out how to kill him,,




oops.
did I say that out loud?

oh yea,,,
sorry,


but he was a BAD man.

honest,
no really he was,,

had a crooked preacher man working for him,,

treated the gals badly,,




oops,,

Sticking my head abovee theparapet. Have read this thread with interest and am not an expert on split charging or batteries so it is possible I have misunderstood the thread, if so apologies.

The system in my 110 is a South African Gensis system. This system charges the starter battery first and only when the starter battery is at full charge does it start to charge the auxilary battery. As far as I understand it these batteries are isolated from each other so that the primary starter battery can not be discharged by the auxilary circuits. It is possible to switch the batteries into a parallel mode so that you can have start assist from the second battery if the starter battery is low.

Is this a good type of split charging system to have?

Ducking below parapet

Regards

Brendan

Hi Leeds, with the exception of vehicles with very small alternators, there is no real advantage to charging batteries separately.

There is actually the problem of taking longer to charge the auxiliary batteries when done separately then when done in parallel and at the same time, but it also depends on use.

If your system has been working for you then it should be fine.

Thanks drive safe.

As a matter of interest what size of alternator is considered to be small?

Running a standard 65(?) amp alternator in my 110.

I have had issues with the 2 Optima yellow tops in the 110, they are about 3-4 years old and do not seem to be holding charge as well as they should. i.e. the auxilary yellow top voltage was 4.6volts after shipping back from Sydney i.e. 2 months at sea.

Optimas apparently have a reputation in UK for only lasting 3-4 years which coincides with a shift in manufacturing facilities.

Currently considering Odysseys as replacement


Regards


Brendan

PS Using Barbaras laptop

Hi Brendan, it’s a wonder you managed to get any charge back into the Yellow Top after having it get down to 4.6 volts.

Any other type of battery and you would have thrown it away.

If you not doing any long drives, you might try putting the batteries on a battery charger that has a float mode and leave them there for as long as you can and see if it bring the capacity up.

As far as your alternator goes, 65 is fine but you would need to drive for just a bit longer, depending on how low your batteries were when you started driving.

Optima batteries, like most batteries, will normally have a better life span in warmer climates, if looked after.

Hi again Brendan, one other thing you might try, but I must be honest, I really think the battery is beyond help BUT, if you know someone with a Ctek battery charge, try it on your battery.

The Ctek have a recovery mode that just might do some good for your battery.

Again, I am amazed that you managed to get any charge back in that battery so you can’t loose by trying the Ctek.

a small alternator is one that barely runs all your electrics....

fozzy when running on high beam with the fridge on, 3 fuel pumps running and with the fuel changeover valve in the powered position, radio on, 2 way on, dash lights on, and the gps on charge draws 31amps the alternator delivers 35.....

normal daytime running is 10-14 amps

night time running is 15-19 amps