I might have asked this before but wanted some clarification. Even when using a .5A charge, I still get some swelling towards the end. The charger often misses the delta peak. So what is a "safe" voltage I can charge these modules up to? I can't sit there and monitor the modules for when they start to show signs of expansion.
The low cost hobby chargers that I have (IMAX B6AC and Supermate DC6) both automatically reduce the charging current as the module approaches a full charge if you tell the charger what battery chemistry it is charging (Lead Acid, NiMh or Lithium). JeffD ps: you do clamp and provide cooling air while charging the modules to avoid swelling.
Is that a separate program? Mine has both charge and "auto charge" but doesn't really clarify what auto charge does.
There is a menu which allows you to set parameters and say which battery chemistry is attached to the charger. It then figures out how many cells in the module itself. JeffD DoctorD.webhop.net/Prius/iMAXB6ACmanual.pdf
I've asked before but didn't get an answer yet. What is generally considered "good" for capacity? Let's say you've done 3 charge/discharge cycles on a module and it won't get above a certain amount of MAh, what number would that be to decide it needs replaced? I've read 2500MAh on YouTube but wanted to make sure.
The important thing is to have 28 modules with the same capacity. When I rebalanced the modules from my 2004 Prius (195k miles at that time) all of them had over 5000 mAh but that was at a low discharge rate (they should be measures at a 6.5 amp discharge rate) so the capacities were overstated. If the modules had measures less than 4000 mAh i would not have sold then to others as useful. JeffD
5000 mAh at low discharge is overstated in what way? What would you expect at 6.5 amp discharge for a normal or good module. Measure mAh after 1, 2, or 3 discharges? Discharging 6.5 amp to 6V or less per module? As opposed to grid charging and discharging pack at .325 amp? Seems to be different suggestions on the best charge and discharge rates for grid vs module.
Not an expert but for the purpose of capacity testing I'd imagine you'd want at least a 5A load. Some batteries like car batteries might test OK on a very small load, like leaving the lights on overnight, but wont test well if put on a 100A load bank tester. Likewise I'd imagine the same for the prius modules to mimic the high amperage load the hybrid system puts on these modules.
I'll have to wait until I pick up my BD250 discharger at the border. I send any USA shipments to ND, try to group a number of shipments to make it worth my while. My 4 channel charger fans really ramp up if I discharge at 1 amp per channel, gets fairly hot.
The fan on my particular charger quit working after a week, I need to email the company and see if they can send me a new one.
The discharge rate does affect the performance of a battery. Measuring the capacity at a low rate will result in a higher capacity reading than at the "1C" rate (6,5 for our NiMh modules) that is used for the new module specification of capacity. A low discharge rate can overstate the capacity by 5 to 10%. JeffD
Well, this is interesting... Last night I fell asleep while the charger was still going. I had it set to 0.5A on two modules. When I woke up, the "capacity limit reached" was showing for both modules, which I had set at 7500MAh. Neither module was warm or showed signs of swelling. So I'm curious at a very low charge rate of 0.5A, does the extra charge "bleed off" or is the battery discharging faster than 0.5A?
I know batteries discharge naturally over time, I'm just not sure at what rate. But I was also reading about form charging which overcharges the battery a few hours after making a completed charge. If I have the capacity for the charger set at 7500 MAh and charging from around 5-6 volts, at 0.5A, should I be safe? I don't want to blow the modules up.
Freaking wonderful, I'm going to have to repeat some tests. I noticed a few modules were completing discharges awfully early. When one I fully charged completed in 10 minutes with only 800MAh capacity, it really raised my eyebrow. These El-cheapo alligator clip leads I got..the wire is crimped with the insulation still on, and the connection is made by what looks like about 1/2mm stripped off the ends, just folded underneath the insulation. I swapped them out with a better pair and the results are much more realistic.
Well the 1st module I drained down to 3 volts is done. On the first discharge cycle down to 6 volts it came back at 2580MAh, now after two more cycles, including taking it down to 3V and letting it charge at 0.5A all night, it discharged to 6V with 6.5A current to 4174MAh, a 61.8% increase.
Some charge/discharge settings from @TMR-JWAP post #268 Dorman Battery Experiences | Page 14 | PriusChat
