SMC Lipo cells won't balance out?

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Wheels007

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Arrma RC's
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I have an SMC lipo that after about 8-9 cycles won't fully balance charge. The charger charges it to 4.2, 4.18, 4.16 and then continuously tries to balance them. I always storage charge my batteries at 3.8 volts. I don't think it's the charger because my other batteries don't have this issue...well yet. Is the battery safe to use or is it on it's way out?
 
Completely safe to use. It’s just tired. But absolutely, completely, safe to use. They’re no longer safe to use when it looks like a football. Lipo cells are pretty strong. I have a hobbystar lipo that fell out of balance last year and it’s still not even puffed! It just takes forever to balance and the third cell never quite makes it. I’m impressed with how it manages to not even puff at all.
 
Yes, still safe. My guess is that you keep running it down to LVC, which is a battery killer. It increases internal resistance and causes other issues. One sign is the longer balance time or inability to balance at 4.2V. Some chargers balance at 4.18 or lower values, which is perfectly ok. Keep in mind that you are talking less than 1% of capacity at that point.
 
Yes, still safe. My guess is that you keep running it down to LVC, which is a battery killer. It increases internal resistance and causes other issues. One sign is the longer balance time or inability to balance at 4.2V. Some chargers balance at 4.18 or lower values, which is perfectly ok. Keep in mind that you are talking less than 1% of capacity at that point.
I've been running my zeee batteries to lvc for over a year (hundreds, if not thousands of cycles) without any imbalance issues. Only issue I have is one of my four old packs is finally puffing a bit but still holds a perfectly balanced charge. Discharging below 3.2 volts is when it gets hairy and most lvc's are set to 3.4 to 3.6 volts so running to lvc shouldn't shorten the life. Charging shortens the life, every time power is applied it is ticking the life cycle away.
 
Yes, still safe. My guess is that you keep running it down to LVC, which is a battery killer. It increases internal resistance and causes other issues. One sign is the longer balance time or inability to balance at 4.2V. Some chargers balance at 4.18 or lower values, which is perfectly ok. Keep in mind that you are talking less than 1% of capacity at that point.
Very good point! And I actually remember seeing a video on this same subject back in 2012, but it was before the 4.18v balance was adopted. Years ago they balanced to a full 4.20 volts. This was bad because most chargers don’t have the ability to charge one cell by itself. It has to charge all cells, then discharge those that are high. So if you have a 3 cell lipo with voltages 4.20 4.20 and 4.18, it would charge all cells: 4.21, 4.21, 4.19. Then it would discharge the first 2 because they’re high: 4.20, 4.20, 4.19. Then do the same thing until the last cell hits 4.20. This presented a very fatal issue, because the charger would overcharge the batteries (4.21 as shown above) which is NOT good. So that’s why they balance at 4.18 nowdays for those wondering ?
 
I have an SMC lipo that after about 8-9 cycles won't fully balance charge. The charger charges it to 4.2, 4.18, 4.16 and then continuously tries to balance them. I always storage charge my batteries at 3.8 volts. I don't think it's the charger because my other batteries don't have this issue...well yet. Is the battery safe to use or is it on it's way out?
If it isn't getting puffy and the voltage is within a couple of hundredths I wouldn't worry too much about it. I have some 8 year old 2s lipo's that are limping but still technically function. Gotta watch for the big ballooning of your batteries and if you have a cell that loses it's charge quickly on it's own. Other than that you should be good ;)
Very good point! And I actually remember seeing a video on this same subject back in 2012, but it was before the 4.18v balance was adopted. Years ago they balanced to a full 4.20 volts. This was bad because most chargers don’t have the ability to charge one cell by itself. It has to charge all cells, then discharge those that are high. So if you have a 3 cell lipo with voltages 4.20 4.20 and 4.18, it would charge all cells: 4.21, 4.21, 4.19. Then it would discharge the first 2 because they’re high: 4.20, 4.20, 4.19. Then do the same thing until the last cell hits 4.20. This presented a very fatal issue, because the charger would overcharge the batteries (4.21 as shown above) which is NOT good. So that’s why they balance at 4.18 nowdays for those wondering ?
Overcharging is definitely a killer. Thankfully most modern chargers don't do this anymore ;)
 
My SMCs look like this and still run them.
20200121_163733.jpg
20200121_162814.jpg
 
From what I understand a small amount of puffing is to be expected throughout the life of a lipo and small differences in cell voltages aren't a big issue.

Secondary and slightly related question for everyone else. What do you do with your batteries when they reach end of life? I've been fully discharging (as close to zero volts as possible) and tossing in the trash...
 
I rarely balance to 4.2, no need. I use between 4.15 and 4.18 depending on the battery and the truck they run in. I set my LVC in the ESC up to 3.4v / cell. On smaller single batter applications I run a LiPo checker/alarm and set it for 3.3 or 3.4. That will usually alarm or hit LVC and the batteries will be 3.65-3.8 v/cell at rest. Perfect. Lithium chemistry batteries last the longest when kept between 20% and 80% charge and those last few tenths of a volt to 4.2 will shorten their life. I will charge to 4.2 if I have need of a really long run for some reason, and it's OK to do that some of the time, but I try to keep mine between 3.7 and 4.15 most of the time.

I lowered the target volts per cell after noticing that cells charged to 4.2 would drift down to 4.18 fairly quickly. That tells me they are pretty unstable right up at 4.2. Charging to 4.15-4.18 range will help them last longer.
 
I rarely balance to 4.2, no need. I use between 4.15 and 4.18 depending on the battery and the truck they run in. I set my LVC in the ESC up to 3.4v / cell. On smaller single batter applications I run a LiPo checker/alarm and set it for 3.3 or 3.4. That will usually alarm or hit LVC and the batteries will be 3.65-3.8 v/cell at rest. Perfect. Lithium chemistry batteries last the longest when kept between 20% and 80% charge and those last few tenths of a volt to 4.2 will shorten their life. I will charge to 4.2 if I have need of a really long run for some reason, and it's OK to do that some of the time, but I try to keep mine between 3.7 and 4.15 most of the time.

I lowered the target volts per cell after noticing that cells charged to 4.2 would drift down to 4.18 fairly quickly. That tells me they are pretty unstable right up at 4.2. Charging to 4.15-4.18 range will help them last longer.
That's the rub, I've been charging my batteries to 4.2 for over a year now and other than the one puffing slightly I've not had any issues. I think the puffing is a product of accidentally leaving the battery fully charged and unused for over a month. Thought it was on storage but turns out it wasn't :(

How do you dispose of your batteries?
 
From what I understand a small amount of puffing is to be expected throughout the life of a lipo and small differences in cell voltages aren't a big issue.

Secondary and slightly related question for everyone else. What do you do with your batteries when they reach end of life? I've been fully discharging (as close to zero volts as possible) and tossing in the trash...
I short em and cut them open with a hatchet.
 
I have two SMC 3s hardcase packs that were in a crash about a year ago, the hardcase is fractured on both and the batteries look slightly puffed. They still hold a charge well and work great, but neither will balance exactly, there will always be one or two cells that are higher or lower. I keep an eye on them and store them in the shed instead of the house just in case, but I still use them regularly with no issues.. In my experience most Lipos aren’t quite as volatile as many think they are unless physically damaged in some way. If you keep them at storage charge in between uses there shouldn’t be problems
 
I short em and cut them open with a hatchet.
LOFL! I see, so you save yours for the 4th of July (or whatever Holiday that frequently has fireworks)?
I have two SMC 3s hardcase packs that were in a crash about a year ago, the hardcase is fractured on both and the batteries look slightly puffed. They still hold a charge well and work great, but neither will balance exactly, there will always be one or two cells that are higher or lower. I keep an eye on them and store them in the shed instead of the house just in case, but I still use them regularly with no issues.. In my experience most Lipos aren’t quite as volatile as many think they are unless physically damaged in some way. If you keep them at storage charge in between uses there shouldn’t be problems
Yeah, I think the biggest issue is letting them sit fully charged too long, couple of weeks is absolute max from what I can tell. Just remember, lipos are at their most dangerous during the charge phase, store them as close to 3.8 volts per cell as possible and store in a fire resistant bag/box/cabinet ;)
 
A friend of mine did that in his yard to a damaged lipo to make a lipo safety video.. it was pretty intense, lol the neighbors thought his house was on fire there was so much black smoke
They pack a lot of magic smoke into those batteries ;)

So long as the casing on the cells is in one piece you shouldn't have fire, only reacts like that with oxygen...try hammering a nail through it or sawing it in half...woof!
 
A friend of mine did that in his yard to a damaged lipo to make a lipo safety video.. it was pretty intense, lol the neighbors thought his house was on fire there was so much black smoke
Yup it’s always a good smokeshow. I have good reasons why I do this instead of just draining it. A lot of times there’s still tons of energy left in a lipo after being drained to 0 volts. Tons, of energy. Very hard to explain how it works.
 
Yup it’s always a good smokeshow. I have good reasons why I do this instead of just draining it. A lot of times there’s still tons of energy left in a lipo after being drained to 0 volts. Tons, of energy. Very hard to explain how it works.
Chemistry is fun! Just add water to some lithium...very similar reaction as sodium ;)

I might try piercing a battery under water to see what happens...need a remote setup to do that because boom? LOL
 
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