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post #11 of 16 (permalink) Old 30-05-2020, 17:19 Thread Starter
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I recently charged the battery with the mains charger so it is pretty full. It's at 86% at the moment. When it's fully charged it reads 12.9V.
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post #12 of 16 (permalink) Old 30-05-2020, 17:27
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My batteries are generally 12.7v when fully charged and have been allowed to rest for a while - 24 hours or so.
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post #13 of 16 (permalink) Old 30-05-2020, 18:15
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Quote:
Originally Posted by Micro Camper View Post
I recently charged the battery with the mains charger so it is pretty full. It's at 86% at the moment. When it's fully charged it reads 12.9V.
I suspect that with the charger still operating or after it has been disconnected/switched off for at least 30 minutes ? That is the recommended time to read the voltage as has been said before by several people.

If it is reading 12.9v have you calibrated your meter in any way ?

A difference of 0.2v would not be significant to me. Generally a significance value of + or - 5% is a commonly accepted value, which for 12.9v would be + or - 0.6v.

That is my way of thinking anyway. If I was you I would probably accept what you have until something indicates a major problem.

Any typo that I make means the errorists win.

Any comments above are only MY OPINION and should be read as that.

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post #14 of 16 (permalink) Old 01-06-2020, 20:12 Thread Starter
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I have two devices which test the voltage at full capacity and both say 12.9V. One of them also has a battery percentage indicator. But regardless of that the problem still stands that the battery is not charging from the main van battery. The voltage is pretty good at the moment due to me charging the leisure battery from the battery charger I plugged into the house mains electricity. But prior to that, and now, when I drive the van or start the engine the battery doesn't seem to charge. The battery reader and other voltage indicator I have both stated 12.9V at full charge and subsequently the battery percentage reader stated 100%. Now it's at 84% and 12.7V. After I drive the van for 30 to 45 minutes nothing changes. Same as before I charged the battery at home (but with different readings).

Please let me know if I haven't been clear but I've tried to describe it the best I can.

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post #15 of 16 (permalink) Old 01-06-2020, 21:29
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Have a look at the picture on the link I posted earlier, 12.7v IS fully charged if you are getting a reading of 12.9v was that obtained after the charging system, whatever it was - the alternator or the battery charger, has been switched off for AT LEAST 30 minutes ?

Your gauge saying the % may well be where the misinformation comes from, 12.7v is fully charged.

The ONLY way that I know of to reliably check whether the alternator is charging, assuming that you have checked the operation of anysplit charge relay, is to partially discharge using a light for instance, so that the voltage drops to say 12.3v and THEN try driving to test the charging, once again waiting at least 30 minutes after stopping any potential charging, then test the voltage which should now be higher than the 12.3 earlier.

If it gas gone up, the charging system is working correctly, if not there MAY be a fault. BUT, it takes a long drive to raise the charge - typically several hours to restore full charge. The reason for the slowness of the charging is due to characteristics of the control system for the alternator which primarily recharges the vehicle battery until it is fully charged, it then reduces the output from the alternator which is what slowly charges the leisure battery.

It is possible to fit a larger alternator or modify the charging control system, but suchbthings are beyond me although they have been discussed on here many years ago I think.

30 - 40 minutes charge will make little difference to the leisure battery charge as I have said, during that time the charge drained from the vehicle battery for starting is being replaced only then will current trickle into the leisure battery.

The leisure battery should not change on starting the vehicle,nthat is why there are two batteries.

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Any typo that I make means the errorists win.

Any comments above are only MY OPINION and should be read as that.

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post #16 of 16 (permalink) Old 02-06-2020, 10:34
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My guess is that the alternator regulation is 'seeing' that the cab battery is charged. The leisure battery, due to the size and length of the connecting wires, has no influence on this and therefore gets about 2A maximum charge. These systems should only be regarded as maintaining ones and not as a charge from flat especially with a low daily mileage.
Only my opinion as an amateur of course. I was though a radio engineer in the Army and our radio vehicles were specially equipped to charge the comms batteries from the alternator and had hand throttle controls to increase the revs when parked up. It was possible to input 16A into the comms batteries independent of the state of charge of the cab battery. I suspect the OP's simple split charge system is nothing like that and as I said perhaps 2A max.
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