Leisure battery test gauge

[darren_5121305]

Could some advice please? I have an old caravan which i have bought a leisure battery 12v 80ah for,I charge it up at home but i am looking for some kind of gauge so i can tell when the battery is getting low so i can ease of or get it recharged,I have been told a volt meter tells you the condition and a ampmeter is the one i wont which tells me how much power is left,,advice please?

 

[rayc]

Darren, an amp meter will show the current being drawn at any instant in time. It will not show you how much capacity is left in the battery.

You need a voltmeter which does as it says. A fully charged battery should read about 14v ( if it has been charged with a car type charger). This will fall off as current is drawn. When the voltage gets to about 11.5v when drawing current it is getting to the discharged state. Some voltmeters are marked in green/ yellow/ red segments indicating the state of charge.

 

[Giles_5119239]

You need a voltmeter, a simple one from maplins or similar will do the job if you can not get a propper car one that is designed for the job with coloured bars indicating the state of charge.

After the battery has stood for 24Hrs the Charge level vs. Voltage is approximatly as below. If you can't let the battery stand put a good load (all the lights or something similar) on it for 5 mins or so to remove the surface charge.

100% 12.7V

75% 12.4V

50% 12.2V

25% 12.0V

Discharged 11.9V

It should be noted that as soon as the battery gets below 75% charge it will start to sulfate and the overall capacity will reduce. In extreme cases where the battery is left in a low state of charge for a long period it will hold little or no charge. Batteries such as the Ecsol carbon fibre/lead batteries claim this won't happen to theirs though...

Hope this helps.

Giles