Maintenance free batteries - how to check?

Use a volt meter. 12.8 volts equals fully charged.
When the battery is under charge the volt meter should show something like 14.1 volts or better.

Apart from that, you can have the battery tested with a load voltage meter which any battery reseller outlet should perform free of charge.

Moose you can check the cells, it should have a plastic peice the length of the battery, peel up that (50mm wide by the length of the battery)

No such thing as a maintenace battery, you can add water

Fully charged battery is actually 12.6 volts (2.1volts per cell)

I use sealed lead acid, calcium batterys and they can have the voltage checked, and be load tested, but this does not check the specific gravity and the ones I use cannot be opened and refilled , and I asked.
The only way to fill them up is to drill a hole in the top.
The manufacturer has garanteed me that they wont dry out and my dealer asured me he will replace them if they need it.
It is hard to get used to not checking and topping up battery's after all these years.

Cheers Pesty

Moose

If you use the volt meter, test it after the car has done a bit of running. With the engine off, turn on all the lights (including reversing) and the fan and watch the voltage. See how far down it goes - I'm not sure but it will be around 11 volts from memory. Then without starting it again till next morning, do the same again and see if its about the same as the night before.

Any major decrease, or really low voltage is an indicator to go to a battery place and have them put the tester on it.

All you can do - certainly don't go unsealing the cells or they will lose water - and you'll lose warranty!

Max

I don't think anyone uses a hydrometer any more.
I measure voltage with a digital gauge inside the vehicle. A resting voltage of about 12.8 is usual with wet cell batteries when mostly charged. As a guide I'd suggest 50% charged at about 12.2 and 10% charged at about 11.8 volts. But theres a heap of variables that affect these readings, so they are only a guide.

Both Tricky Dicky / Tandy and Jaycar sell an LED 12v battery testing (volt) meter for $9.95 (strangely they all sell for the same price), that covers the basic tests of rested battery alone, battery under charge, alternator charging voltage, and external power supply charging voltage. You may find that is all you need. The instructions are limited but with a lttle help you can cover all the above operations

You can use a multi meter to check your battery but to get a roughly accurate idea of the State of Charge, you need to leave the battery in a No Load / No Charge state for at least 48 to 72 hours and then you can get a reading that will be around 95% accurate because, as posted above, there are a lot of variables that come into it

Even so, a 5% error margin is still going to give you a fairly good idea of the State of charge.

One additional point, if you have wet cell batteries and use a hydrometer to check them, they have about the same 5% error margin.

If you test your battery and think it may be down a bit ( or more than a bit ) as posted above, take it somewhere and get it load tested.

If you do your own testing, make sure you then go to your battery manufacturer’s web site and get the correct info for your specific battery. It does very slightly from one battery type to another.

One more tip, if you see advice on the State of Charge or battery charging that states by doing this form of charge or not doing that, that the battery is or is not 100% charged,take it with a pinch of salt.

There is NO WAY to determine if a battery is 100% charged or not, while the battery is in the vehicle or caravan or what ever. The best results are only likely to be 95% accurate and to determine otherwise means removing the battery and taking it to a laboratory to fully analyse it to be able to get a 100% accurate SoC of the battery.

Cheers