If you're bashing with these batts, good charge rate would be 3.7amps. If you're racing would prob want to charge at higher rates, maybe as high as 4.5-5amps. Peak setting - good start at 5mv/c. I'm not familar with your charger, some use peak setting per cell and some use a total, you should be able to tell which is needed.

Believe what you're seeing are called "false peaks". Charger sees enough of a current rise to think batt has peaked when it hasn't. The 800 is prob what it put in of the 3900 capacity you input. Just re-set and charge it again. If you're worried about what is going into batt, take note of charge before resetting so you can add it up when batt does finally get a complete charge. When NiMH batt peaks, it should be hot - 120-130F or so, I know its aggravating, but you may have to re-set it a few times until it charges all the way. Some chargers feature a peak delay recognizing this that lets you tell charger to ignore apparent peak for certain time so this doesn't happen.

I had false peaks with my 1st charger but only when charging at its highest rate. It was an AC/DC charger and I later realized I had it on a busy circuit in the house and when I was charging, if something else kicked on or was turned on, that was triggering the false peaks. I moved it to a lot less used circuit and the probs went away.

Welcome to the forums btw!