... Found a RC Pack that has great potential for 24V systems and specifically for my eZips with the RMB battery packs.
Floureon 7S 5000mah 25.9V 40C Lipo Battery <$60 delivered from USA
Recommended for rebuild of eZip 24V RMB battery packs.
Will fit up to 4 x 5Ah = 25.9V 20Ah vs oem 24V 10Ah (5-6Ah usable) SLA.
Every 24V controller I've ever tested works properly with 7s 25.9V battery, but a bit faster with some more torque ...
eZip RMB pack internal dimensions:
150mm x 65mm x 230mm
1 $60 brick = usable capacity of $120 SLA pack
2x ($120) = capacity of $570 10Ah oem Lithium RMB battery
4x ($240) @ 10lb = 2x $570 10Ah oem Lithium RMB battery or 4x $120 (65lb) SLA
(4x leaves room for 22mm x 650mm x 150mm BMS)
Received 1 sample and began testing.
(Dimensions confirmed and solid brick no noticed defects)
#1 Tested shipped voltage of each cell.
7 cells varied from 3.80V - 3.84V (.04V variance = reasonably equal)
#2 Bulk charge to iMax Lion 4.10V
2207mAh to average 4.07V
Additional Bulk charge to iMax Lipo 4.20V
776mAh to 4.168V-4.218V (.05V variance = reasonably equal for oem shipped but "poor" for "use")
#3 Precisely equalized cell voltages
within .001V (4.159V- 4.160V)
1000th V meter recommended (Lucked into a $150 Fluke multimeter for $10)
#4 Letting cells set to evaluate self-discharge
100 hours 4.150V 4.158V - less than 100thV "self-discharge"
(variance is liable to be amplified charge\bleed down of cell voltages to match - "equalized" voltages were not "settled" results)
Will continue to compare voltages at 24 hour intervals until any self-discharge can be determined.
- Self discharge tests
14 days worst cell loss .027V
All cells within .013V
8 days worst cell loss .03V
All cells within .006V
8 days worst cell loss .03V
All cells within .011V
8 days worst cell loss .026V
All cells within .010V
4 days worst cell loss .018V
All cells within .005V
No cell seems to be of abnormal self discharge.
Self-discharge will be reassessed on a scheduled basis or if any indication deems necessary.
#5 IR testing
Will continuous discharge at 5A (1C) and monitor voltage sag as a measure of IR (Internal resistance)
Each cell will be metered under discharge and compared for equal IR
Will discharge to ~50% and precisely measure static voltage several minutes after voltage removed (pending)
Compared voltage will indicate comparative capacity
#7 Will discharge further, at reduced rate, while monitoring all cell voltages
.001V meter will be relied upon to determine capacity cliff @ ≤3.60V (unable to find oem discharge graph!)
#8 iMax bulk charge to 4.10V Lion setting will indicate if all cells return to equal (balanced) voltage
as safety before continuing with iMax 4.20V LiPO bulk charge setting
#9 If battery prove of good-equal quality, I will create a capacity map to determine optimal charged and discharged voltages
0.8C max recommended charge rate. ≤0.5C recommended for better life!
". Long cycle life (150 times minimum)" - moderate discharge rates combined with lowered charged voltage expected to extend cycles into the thousands! ... ?
". One-year battery warranty." - nice safety net!