Some of you may know my own distaste for external balancing boards on simple 4S lifepo4 batteries for a variety of reasons.
I have to say that in front of my own eyes, the Tecmate-Optimate TM-291 lithium charger actually does the job without using individual charging leads. It has nearly perfectly balanced my own 20 and 40ah GBS 4S lifepo4 batteries. They say it can handle up to 100ah, but I don't have that large of a battery yet.
The reason it does this is that it does NOT apply just a CV at the end of charge, but a variable oscillation from 14.1 to 14.3. Each cell reacts differently during the minsiscule lifepo4 absorb curve, and if it didn't oscillate, current would just stop prematurely on an unbalanced pack. By oscillating it, during the time it takes to go back up to 14.3v at each oscillating cycle, the undercharged cells slowly catch up.
Ordinarily under a standard CC/CV routine, this would not happen as you'd expect and no balancing would occur.
I proved this to myself by purposely severely unbalancing my pack, and having a go at manual balancing via an RV incandescent bulb during charge. By hand, I could do no better than getting the cells to about 0.020mv delta before going nuts. Actually, this isn't that bad, but I wanted better, but just could not obtain it.
I let the Optimate do it's thing instead, and bang. 0.005mv difference.
Thing is, you won't think this is happening if you use only the Optimate, as during the cell balancing cycle, voltages are not going to be exactly equal under charge, or even after a few hours rest due to slight differences in manufactured capacity and internal resistance.
BUT, if you then take that optimized battery, discharge it, and then charge it again with a standard CC/CV charger (which I take no higher than 14, and a drop to 0.05C), THAT is where I encountered near perfect voltage balance under charge. I use a Samlex charger for this normal duty - or my solar CC and panel setup.
One tip is that you probably want your cells to be *reasonably* close to each other before the start - that is, if you notice that one cell is surpassing 3.6v when the overall pack voltage is 13.8v, and another cell is sitting at 3.3v, that is way too far off. Use a single-cell charger, or some other technique to get them reasonably close, and let the Optimate finish the job.
So ok, the Optimate is coming from a powersports application (like Antigravity batteries that use A123 cylindricals, and NO balancing circuits), but it worked just great on my larger prismatic GBS lifepo4.
I wouldn't post this if I hadn't seen it before my very own eyes. Remember though that I have only verified balance with 20 and 40ah batteries. I'll have to save up a bit to prove it on something as large as 100ah, which is supposedly the limit for the Optimate.
I have to say that in front of my own eyes, the Tecmate-Optimate TM-291 lithium charger actually does the job without using individual charging leads. It has nearly perfectly balanced my own 20 and 40ah GBS 4S lifepo4 batteries. They say it can handle up to 100ah, but I don't have that large of a battery yet.
The reason it does this is that it does NOT apply just a CV at the end of charge, but a variable oscillation from 14.1 to 14.3. Each cell reacts differently during the minsiscule lifepo4 absorb curve, and if it didn't oscillate, current would just stop prematurely on an unbalanced pack. By oscillating it, during the time it takes to go back up to 14.3v at each oscillating cycle, the undercharged cells slowly catch up.
Ordinarily under a standard CC/CV routine, this would not happen as you'd expect and no balancing would occur.
I proved this to myself by purposely severely unbalancing my pack, and having a go at manual balancing via an RV incandescent bulb during charge. By hand, I could do no better than getting the cells to about 0.020mv delta before going nuts. Actually, this isn't that bad, but I wanted better, but just could not obtain it.
I let the Optimate do it's thing instead, and bang. 0.005mv difference.
Thing is, you won't think this is happening if you use only the Optimate, as during the cell balancing cycle, voltages are not going to be exactly equal under charge, or even after a few hours rest due to slight differences in manufactured capacity and internal resistance.
BUT, if you then take that optimized battery, discharge it, and then charge it again with a standard CC/CV charger (which I take no higher than 14, and a drop to 0.05C), THAT is where I encountered near perfect voltage balance under charge. I use a Samlex charger for this normal duty - or my solar CC and panel setup.
One tip is that you probably want your cells to be *reasonably* close to each other before the start - that is, if you notice that one cell is surpassing 3.6v when the overall pack voltage is 13.8v, and another cell is sitting at 3.3v, that is way too far off. Use a single-cell charger, or some other technique to get them reasonably close, and let the Optimate finish the job.
So ok, the Optimate is coming from a powersports application (like Antigravity batteries that use A123 cylindricals, and NO balancing circuits), but it worked just great on my larger prismatic GBS lifepo4.
I wouldn't post this if I hadn't seen it before my very own eyes. Remember though that I have only verified balance with 20 and 40ah batteries. I'll have to save up a bit to prove it on something as large as 100ah, which is supposedly the limit for the Optimate.
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