Battery capacity test?

Is there a SIMPLE reliable way to varify the capacity of a 12V lead acid battery? I have it on an optimate which says its heathly but I would still like a real world check. I have several multimeters.

Is it sealed or can you get at the acid? I used to use a hydrometer to measure the specific gravity of the acid, that tells you for sure.

Is there a SIMPLE reliable way to varify the capacity of a 12V lead acid battery? I have it on an optimate which says its heathly but I would still like a real world check.

Try and start something with it

That checks if it has enough. Not how much.

You could discharge it with a known load e.g. a bunch of bulbs and measure how long it takes.

You can then calculate the power available in the battery.

Or you could take it to Halfords and have them stick it on a meter which will display the CCA.

You can use expensive (I think) load testing devices that measure voltage drop under load.

There must be complex calculations you can do having a known load and voltage drop for given time.

You can just leave it a week or month and see if it will still do what is required.

The problem with batteries is they can maintain a voltage but under load this drops away.

Modern cars are prone to having batteries die with little warning. My understanding is: They generally start with little cranking, modern charging systems and battery monitoring systems maintain battery till it just gives up.

Is there a SIMPLE reliable way to varify the capacity of a 12V lead acid battery? I have it on an optimate which says its heathly but I would still like a real world check. I have several multimeters.

The only way to test capacity is to fully charge the battery and then apply a known drain for x amount of hours, then leave the battery disconnected for 2 hours and look at the chart above to see what the stranding voltage is. Don't discharge the battery more than 50% though.

Probably not worth faffing about with a bike battery mind, if it's dodgy buy a new one