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What is correct leisure battery charge rate?

7449 Views 5 Replies 4 Participants Last post by  Clarkson46
Hello everyone, hope you had a happy Xmas.

We've been doing some electrical measuring in my campervan (Early 73 Bay). We wondered if anyone could tell us... what is the normal charging rate for a Leisure Battery?

When the engine is running nicely, and the two batteries are connected via the split charge relay, the Leisure Battery is charging at only 2A or so. This seems a bit miserable, since it would take several hours (or days possibly) to recharge a flattened Leisure Battery.

We have hunted down a bit of drop-off, and are going to make amends to claim a few milliamps back, but not much really. I guess we had expecting it might be charging at something more like 8A - are we mental?

(we haven't been able to measure the charging rate of the main battery, for obvious (?) reasons - but if anyone can tell us what this is likely to be charging at as well, we'd be interested to know)

BTW it's an alternator conversion.
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A battery will only "draw" what it wants from the alternator.

Think of it like a sponge soaking up water, if a dry sponge was introduced to some water it would soak it up quite quickly until it was holding all the water it could then it would soak up no more. Your battery is the same, when it's near full or full it will draw very little amps.
A leisure battery has very different charge/discharge characteristics to a starting battery. As Roly said it will take whatever it needs from the charging system. A flat leisure battery can take up to 4 days to recharge which is why people moan about them, as popping down to Tesco's won't charge it.
Thanks, good points both. And yes this battery is freshly charged from the mains, so perhaps it's not surprising it only charges at 2A today.

The background to this is I just took a 3 week camping trip to Rome and back, and the Leisure battery performed appallingly. It was brand new, and it wasn't charged on the mains beforehand. Immediately after long drives (say 4 hours) the battery would be showing a healthy 12.5-13V, but after just half an hour of DVD watching (6A draw maybe?) the invertor would bleep and switch itself off (because the battery had reached 10.5V). When I got back from the trip, the battery was pretty much totally discharged. So I was worried that maybe the circuit wasn't charging the battery at all or with not enough current.

I can't recreate this situation now because I have a fully charged battery! But can you tell me, with a half flat or totally dead battery, what sort of Amps might I expect to be reading while the engine's running?
Charging of lead-acid batteries, whether for cranking or deep-cycle use, primarily depends on the battery terminal voltage. Charging to some lesser voltage, even for long periods, may not fully charge the battery.

Charging is a complex issue, but there are some guidelines here:

A leisure battery needs a commissioning charge before use. I suspect that is where you original problem lay. Put it on charge for a week and then check the state of charge using a hydrometer as that is the only true test of the battery's state of charge.
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