Lead acid battery charge indicator

Green is the new black I hear.

Being semi sensible for a moment. I never did find those gadgets worked and in any case who could tell when the bonnet was closed? :-) Brian

Not my field, but I would venture to say it's not very informative anyway if it doesn't tell you the state of the battery under cranking, which I'm guessing it doesn't.

Can't see the original post.

However in a motor home the charge indicator seems reasonably useful. More so for the habitation than the engine battery, but still an indicator.

Cheers

Dave R

I added a digital volt meter to the old Rover. Just a bare LED PCB, but as accurate as my Fluke, and only a few quid. It's a two wire type, so couldn't be easier to connect. Although I did find it needed to be directly connected to the battery for best results, rather than to the dashboard wiring.

If you know how to read it, shows both the battery condition and that the charging system is working correctly.

But you open the bonnet to se why the car won't start, and glance at the indicator.

Or you have the battery sat in the garage and can't remember if you charged it recently.

Maybe it was just temporarily stuck. If it's the sort I am thinking of, they're just a simple float of the right density to float or sink depending upon the specific gravity of the electrolyte - just like the old battery hydrometers from when the batteries weren't sealed for life.

Sometimes I see green on the leftmost quarter of the window, perhaps it's not floating straight.

I read something once that only calcium based batteries have these floats. And the USA prefers calcium batteries and the UK doesn't. They have different discharge characteristics I believe.

If the battery indicator is tuned to the battery in question, then it is possible to get a fair representation of battery condition.

Though it will not tell you the immediate capacity, it will show progressive indications of low full-charge voltages as the battery's internal resistance grows.

As others have said, taking a battery through charge/discharge cycles will tell you more.