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bench charger vs reg charger LiFePo4 24v

boatmonkey

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Joined
Oct 5, 2020
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Hi!

i have a 24v 200Ah LiFePo4 pack. I used to charge it with RSP-750-27. Its fully programmable charger. I have set it to 29v and it outputs 31.8A. It has a remote disconnect hooked up to the bms. The bms shuts it down when one of the cells hits 3.53v. Its a save value for my prismatic cells (max is 3.65). But lately i have been seen a lot of posts stating it might be better for longevity to set this cutoff value abit lower (3.45 or even 3.4).

Question 1: What is your take on this?

I recently bought a bench charger. Mostly to experiment with individual cells. Do capacity tests etc. But I really like it so far. It can output 0-30v, 0-10A. Now i was wondering, can I also use it to charge my whole pack. Set the bench charger to 28.0v. (Of course with a remote disconnect controlled by the bms). It only outputs 30% of my original charger, so it will take a lot longer. But it has a lot less noice, and uses less power (so i could use a small dedicated generator for it).

Question 2: Are there any drawbacks of doing a slow charge with a bench charger as opposed to my original 32A pumping puppy ?

Thanks!
 
Your charge cut off voltage should be a function of the charge C rate. If you charge at 1C, a cutoff of 3.65V might be just fine. If charging at 0.15C, like you are, the limit should be lower. The 10A charge on a 200Ah pack would only be 0.05C. Cutoff should be lower still.
 
No way of knowing how much lower?

Besides charging time, there are no disadvantages of charging with 0.05C as opposed to 0.15C?

(The data sheet that came with me cells shows reg charge rate at 0.2C)
 
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