Hi,
I see there's been a lot of discussions about monitoring and controlling charge on the newer phosphate chemistry cells.
I've been working with the A123 cells for awhile now, mostly for integration into large scale packs for EV's. I'm also a TidalForce bike owner, and have another bike with a C'lyte 408 motor and 72v controller.
To help our fellow TF owners, I assembled a relatively simple system to clamp the cell voltage during charge, and reduce the charge current when the preset voltage is achieved on any cell.
An MCU monitors each of the vclamp modules, linearly decreasing the charge current until charge is eventually terminated when the last vclamp activates after the charge current is reduced to I minimum. I minumum is 50ma per cell in any parallel configuration, or max time achieved, or temp max from an embedded sensor in the pack(s).
The charger is a 1kw lab power supply that is being driven by the PWM output feature of a Uchip MCU. I've ordered a couple of low cost 500w SMPS's from a HK distributor that will be used in the final design.
Image of the individual vclamp board.
An image of the vclamps installed on 6p A123 clusters.
The schematic of the vclamp in pdf.
I'll post the schematic of the MCU board when the power supplies arrive. It'll probably require a board revision to accommodate the changes needed for these cheap power supplies.
I did not include a low voltage cutoff (LVC) in the Tidalforce version, since the controller can do this task.
This is recommended if your controller does not include an LVC circuit and you're not familiar with the actual performance of the cells you have used to build the pack.
An LVC can be added to the clamp circuit with another small darlington, a few passive parts, and another optoisolator. Or a low voltage reset IC, and a couple passives, and the optoisolator.
Regards, Jeff
I see there's been a lot of discussions about monitoring and controlling charge on the newer phosphate chemistry cells.
I've been working with the A123 cells for awhile now, mostly for integration into large scale packs for EV's. I'm also a TidalForce bike owner, and have another bike with a C'lyte 408 motor and 72v controller.
To help our fellow TF owners, I assembled a relatively simple system to clamp the cell voltage during charge, and reduce the charge current when the preset voltage is achieved on any cell.
An MCU monitors each of the vclamp modules, linearly decreasing the charge current until charge is eventually terminated when the last vclamp activates after the charge current is reduced to I minimum. I minumum is 50ma per cell in any parallel configuration, or max time achieved, or temp max from an embedded sensor in the pack(s).
The charger is a 1kw lab power supply that is being driven by the PWM output feature of a Uchip MCU. I've ordered a couple of low cost 500w SMPS's from a HK distributor that will be used in the final design.
Image of the individual vclamp board.
An image of the vclamps installed on 6p A123 clusters.
The schematic of the vclamp in pdf.
I'll post the schematic of the MCU board when the power supplies arrive. It'll probably require a board revision to accommodate the changes needed for these cheap power supplies.
I did not include a low voltage cutoff (LVC) in the Tidalforce version, since the controller can do this task.
This is recommended if your controller does not include an LVC circuit and you're not familiar with the actual performance of the cells you have used to build the pack.
An LVC can be added to the clamp circuit with another small darlington, a few passive parts, and another optoisolator. Or a low voltage reset IC, and a couple passives, and the optoisolator.
Regards, Jeff