i leave car on the charger. the led goes to red (good chargeing) later led goes to Yellow( good looking nearly charged) later led goes to green ( good charged,
in the morning the battery the show 85 percent. mades no difference if I take of the charger or not.
i replug it on and the led goes led yellow. if about 20 minutes goes green and shoews 100 percent.
not about the speedometer but i put my GPS on and the speeed shows 28 the speedo shows 22.
My car does that every so often. I think it could be the difference in temperature when you charge it. I use a WANF kilowatt hour meter I bought on Amazon. See how many kilowatt hours it takes to charge the batteries after a 10 mile run. It should be around 2-2.5 KWH. I find that sometime the meter will start at 100% or 85% but after running the car 10 miles the meter will read around 70% regardless of the starting charge percentage. The meter will go down faster from 100 than it does starting at 85.
All of our pre-2005 GEMs have shown a fast initial loss of charge. Apparently, the indicator “guesses” what the correct percentage of temperature corrected charge should be and displays this on the meter. This has been an indicator that one of the batteries is getting weak. The meter drops fast as the weak battery quickly looses voltage. A weak large battery often acts much like a much smaller battery. It will reach full charge quickly because it is unable to absorb very much power. A load test on each battery will show which one(s) is(are) bad.
Yes, I agree with Daniel if the battery charges up too fast or discharges fast this is a classic sign of a battery or batteries in the chain that has lost its capacity. If I put even a mile or two on the car the charger will always take at least an hour to get to the green light.