Questioning Battey/Voltage gauge

I can already see how a Gauge like a Batt Sixx (BSM) that would read my state of charge would solve this problem. But seeing how they are close
To $500 I’m holding off and saving for a New Quick Charge battery charger
(I have the stick Vivan right now)

So here is my question. I have brand new FLA battery’s. My state of charge registers at 100% on the stock dash gauge. I drive the Gem around till my state of charge drops into the 11% range. The charge seemed to fall off rather quick. 10-12 miles of hilly miles Now remember I’m Relying on my dash gauge to tell the truth. Once it’s low I race back home but it’s dropping rather quick and it’s all down hill. So I get back home and plug it in and 30 mins later I UN plug it and the dash gauge is reading 100%
The red charging light is still on and solid. It had me thinking How could this thing be anywhere near 50% state of charge with only 30mins of charge.
It had me 2nd guessing the stock dash gauge. Did I realy dip down to 11%
Or was it inaccurate?

2nd scenario ; I was driving a friends GEM we left the house with 100% charge. Drove it for a few miles and got down to 70%. Got to our destination and turned it off and came back out to go home and the dash is now reading 100%. How is this possible.

Are the stock dash gauges not to be trusted?


Personally I don’t “trust” the OEM SOC (state of charge) gauge. As you’ve noted, it’s not reasonable to have it charge up to 100% that quickly from such a low SOC. I SUSPECT it’s simply reading the total voltage and extrapolating pack’s overall SOC from there. Each type of battery technology has a different discharge curve so when it’s a generalized algorithm I’m very skeptical.

I’ve too have had the experience of driving it and stopping for an hour and come back to find it’s “recovered” to 100% although it rather quickly drops again once I start driving. I imagine that all has to do with the age of the batteries and their technology (FLA, AGM, GEL).

If I had the $500 to throw at the problem I’d go with the BattSix since it does read and indicate voltage AND SOC and that would make me feel much better.

Incidentally my rule of thumb for whatever it’s worth is I don’t run the pack below 50% on a regular basis. Once in great while I’ll drive it into the 40% range but anything beyond that I think you’re playing a risky game AND it’s not good for the batteries. Given the replacement cost of the batteries, I’m their best friend and they’re mine!!