BlueSmart 12/15 settings for self-built LiFePO4 (4s) battery

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jaycobius asked Jul 19, '21

BlueSmart 12/15 settings for self-built LiFePO4 (4s) battery

Hi guys,

I just finished building my battery bank (4S 202Ah Lishen A-grade) and I now want to initialise the battery using my new IP65 12/15 charger. The manufacturer sent along a detailed data sheet where a charging end voltage per cell of 3.65V (x4 = 14.6V) is specified. I programmed the BMS to cutoff at that voltage accordingly.

My question now is: Which settings do I use with the 12/15 charger to fully charge/initialise the battery? I want to top balance the pack and then use the Orion-Tr in my vehicle to recharge it. The initialisation/top balance step will have to occur now. And then just once in a blue moon...

Normal (which I understand is for lead acid batteries, is rated at 14.4V) and Li-Ion (14.2) both seem too low, and High (14.7V) seems too high. Inside the app I can select a preset "LiFePO4" profile, but this also has a setting which to me seems too low: 14.2V absorption and 13.5V float and storage, as 14.2V/4cells = 3.55V

Maybe I am getting something wrong? I'd greatly appreciate your help with this.

Cheers, Jacob

battery charging BMV Battery Monitor Lithium Battery ip65

screenshot-2021-07-19-at-214433.png (77.7 KiB)

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Mike Dorsett answered · Jul 20, 2021 at 03:20 AM

I think that to do this correctly, you will need to create a custom battery configuration - if that is possible with the 12/15 charger. For the Lithium spec - +/-50mV is typically specified, so if you can get to 3.6V per cell that will be adequate. If not 3.55V/cell will be good enough, the soc difference will be <2%. Never go above the specified voltage, but if you can't quite get there, there is no problem. You will need to set the Float voltage equal to the Absorption voltage to do this properly, as the tail current will drop quite low during balancing. The trick will be to ensure that no cell goes over the 3.65V limit as full charge is approached. If this happens, the charge current needs to be reduced so as the balancing circuit can do it's work.

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jaycobius commented · Jul 20, 2021 at 05:20 AM

Thanks @Mike. This makes total sense. Luckily the IP65 12/15 is able to handle a custom battery setup. Very good point with the absorption/float settings. I will try your suggestions and let you (and everybody who's interested) know what happened.

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Answer 1 · 2021-08-14T07:03:33Z

jaycobius answered · Aug 14, 2021 at 07:03 AM

After some trial and error, I managed to get the pack to 14.2V, with absorption set to a fixed 8 hours. After balancing each cell now has 3.55V - which will do the job for me. I’ll now measure the capacity with the shunt and set the BMS to work the pack between 90 and 10 percent SOC.

thanks again, Mike!

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