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| Modding old ATX supplies for 3.65v output at high current for LiFePO4 charging |
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| fixy88:
I have a 4s LiFeP04 pack that I hope to use very occasionally in short notice. It is stored ~1/2 charged. Unfortunately the pack was originally supplied with mismatched cells - at the I was unable to return them. This makes charging very slow as the cells have different charge curves and a standard charger reduces the charge rate before some cells are close to charged as the inbuilt balance shunts can only handle very low currents. I'd like to build a charger with 4 independent channels capable of around 20-25 amps per channel at 3.65v and am considering using modified ATX supplies. Is this feasible and is the modification likely to be more complicated than changing a few resistors? Thanks for any ideas! |
| wraper:
Modifying PSU for this purpose is not feasible. But it's completely suitable for powering proper charger, though there might be issues with minimum load requirement for some ATX PSUs. --- Quote ---capable of around 20-25 amps --- End quote --- You'd be an idiot if used dodgy charger at such current. |
| fixy88:
--- Quote from: wraper on June 29, 2019, 12:45:10 am ---Modifying PSU for this purpose is not feasible. But it's completely suitable for powering proper charger, though there might be issues with minimum load requirement for some ATX PSUs. --- End quote --- Can I ask specifically why it isn't feasible? Thanks! |
| wraper:
First of all, constant voltage won't work to begin with. It needs current regulation with current dependent on battery charge. Also it needs to detect when battery is fully charged, overcharging is completely unacceptable. |
| NiHaoMike:
Have you checked how many banks are high/low? Most likely the easiest way to solve the problem is to build a temporary balancer with a comparator switching a load (such as a car light bulb) using a MOSFET, to be manually connected to a high bank. You can also modify the BMS to have a higher balance current. I like to use LEDs as the loads to give a visual indication of balancing activity. http://www.kerrywong.com/2017/09/10/modifying-a-4s-100a-lifepo4-bms-module/comment-page-1/ |
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