Battery meter

[Burgerman]

On lead based batteries like AGM/GEL etc we ar all used to seeing the common charts like these 2 below.

At 12.2V or 24.4V we are toldd that the battery is 50% to 60% charge remaing.

See below for 24V as we use.

and a 12V battery.

So now we can go just as far again right? DONT BELIEVE IT!!!

[Burgerman]

That would be true, above IF we only wanted to light up a light bulb and draw out the current slowly over a 20 hour period...

Heres what REALLY happens in a powerchair

Note, this applies equally to all controllers, not just this old one. R-Net etc is the same. The issue is not the controller, its the way lead batteries work.

HERE we have 24.2V or 12.1V or according to the charts above about 45% of 50% of the range remaining.

And then, I went from my bedroom, to the kitchen, and back.
As I turned the chair around it started flashing red on/off and will not move any more. THIS is the point where the chair stops. Its done!

And so it dropped from 24.2 to 24V in just 45 feet of movement then stoppd moving!
With about 40% of the battery (supposedly) remaining...

So what happened here?
Well that 40 to 45% IS actually still in there! Its just that it is inaccessible to us at the RATE we want it. If we turn it off, wait a day, then much of that missing Ah will come back like nmagic and all the battery lights will come on. And then we will be able to use around 1/3rd of that recovered power before we have the same issue all over again.

As you try and discharge lead, in a chair, takes a lot of current. And as you discharge any lead battery its internal resistance goes up and does it fast at higher currents. At the 55% used up point (or there abouts) that allows the voltage to sag under load low enough to make the chair stop. And put out all the battery lights.
A 100Ah lead battery is really just 50 to 55Ah one in a typical wheelchair with the rest INACCESSIBLE to us..

Thats why lead is so crap!