This time i think i cracked the formula. please correct me if it is not true.
12.500 mah / 1000 = 12.5Ah * 1.6 (4000mah / 2500mah) = 20A?
12.500 = battery pack capacity 4000mah = max charge current pr cell 2500mah = capacity of one cell
The capacity of a single cell or pack does NOT matter when charging. As stated above the Parallel stack number 10S5P -> 5 in this case dictates the max. (continuous) charging current. So:
4A (Per Cell in Series!) * 5 (Stacks in Prallel!) = 20A
As braking is not cont. (Maybe 5-25s) you can increase it a bit: Up to 25-30A
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As this thread is called “Is regen charging bad for the battery” it think I should wirte something down:
-Regen Charging is good for the Battery!
There are a few published Papers and Studyes on electric cars which studied this topic. They wanted to know if the increased charge cycles had a negative effect on the battery life. It turned out there was no negative effect, and even a “healthier” longer lasting effect.
Charge current is in amps. Capacity is in Ah. Power Capability is usually stated as C for lipos and for liions they usually state how many amps they can put out continously.
Imagine your batteries being pigs.
Either you have a small pig that can eat only 1 pound of corn til its full. The larger pig can eat 30 pounds. How much corn the pig can eat is equal to its capacity. Thats the amount of energy it can utilize when digging in the dirt. So lets say 30 pounds of corn gives the pig a full day of gentle digging until its out of energy and collapses or overheats, or it can do super intensive digging for 1 hour, but not many pigs have done that without ending up in ICU, so thats only in theory. So lets call the capacity of the larger pig 30 pounds of corn in 1 hour as it’s the absolute maximum in theory. The smaller pig has a capacity of 1 lbs corn in 1h, so in comparison it’s a piglet.
Then there is something we call C or power capability, and in the pigs world this is digging capability. A high C means the pig is comfortable digging at a rate that is so intense that it burns a lot of that corn it previously digested. The smaller pig is in super good shape and it digs holes at a rate that would make it end up in China before sunset (if it would only have had a bigger belly to store that corn). If you try to push the pig to dig any faster, in time it will most likely overheat and eventually die. So at the maximum rate, it will burn lets say 10 lbs of corn / hour, so we decide to say it can output a continous digging “energy” of 10 lbs of corn. The larger pig is a lot slower though and if you pushed it to dig at the same rate as the small pig it would probably end up with hyperthermia and a heart attack.
How fast can you feed the pigs then to make them go dig again? Well for that you’ll have to ask their moms and dads, cause they usually know best. For batteries this is found in the specs for the specific cell. This is much dependent on how large the pigs mouth is. It likes to eat slowly, but it’s capable of eating faster as well, although its inner organs will probably take a beating if you feed it too fast too often.
What if you feed four equally large pigs at a time then? If they stand next to each other and you throw the corn on the ground, they share the food equally, cause every single pig will get to just as much corn as the one next to it. Every pig gets a 1/4 of the corn.
What if the pigs are standing in line while you’re feeding the first line of pigs? The first pig will be happy and eat all the food that was meant for all four, but after a while, what goes in must come out, and that’s where the second pig gets happy, cause even though he will have to eat shit, he is a dirty pig, so he will happily eat up all that processed corn,and so will the third and the fourth.
So there’s your batteries for dummies!
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Regenerative breaking is good, but not for everyone! If you are using a battery without a BMS (Or bypassing the BMS for discharge), regenerative breaking will unbalance your cells. That’s why your new battery is fully charged at 42.3V the first time, 42v the second time and 41.8 V next, so on and so forth. I really need a good way to disable it but when I set regen at 0, I don’t have no brake anymore 
Honestly why would I wanna charge my battery this way? (3 seconds every 30 seconds)
I don’t think that your cells get out of balance by this little tinny bit you charge back. You use a bms for charge only what means even if your cells get out of balance by reg breaking at the next charge the bms will bring them up on the same level. If you still worry than just use a bms for charge and discharge
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I wondering if you can set battery min to 0 and then turn on reverse to brake. Problem with 0A regen is that you with have no control of your brake. It can only short 3 phase together or not break at all.
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Most people think that BMS balance charge you battery! But in fact, that is just what it is suppose to do. Only good quality BMSs (expensive ones and industrial ones) do that. The ones we all end up buying for e-bike and e-sk8te don’t balance charge. They just cut off the current flow from the charger when one cell reaches 4.2V (some 4.15 or even less).Same for $50 and less lipo balance chargers. It is important to know that, they won’t bring your cells back to the same voltage if they were off, but they will keep the same gap between cells until fully charged. That s why you have to charge equally your cells before building your pack. A regular bms can’t stop charging one cell and keep charging the others.
That’s not correct. You can get a bms for charge only at 25$ or less like the d140 from bestech which will balance your cells out. There also smart bms options on the market with which you even can watch how the voltage from every pack get paired up to the others.
Yeah, just tried! It’s very unsafe. Braking becomes very jerky and I think this gives hard time to the VESC. Might work on different setup tho!
Also not right. I have a i max b6 charger for my lipos. It’s like 35€ balance charger. With it i definitely balance out every cell of my pack. I can even discharge the lipo pack to storage voltage.
One thing I need to add on the comment I made before, If you have a 2p 3p or how ever pack for sure the bms will not balance every single cell, only the p pack, but this will every bms even the most expensive one.
And one more thing… the data sheet from the d140. As you can see it’s written the balance current and also how the bms will balance your cells.
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I used to setup BMS both for charge and discharge. But you can’t use the full potential of your battery if you do so. That’s not really bad if you re using a decent amp tolerance BMS and a less power hangry setup. Furthermore, BMSs can also die during agressive rides and it’s painful. For the regenerative braking, you don’t really need to actually charge it for it to unbalance cells. I tried charging off BMS on a power supply (set charging current at .2 amps) at that point with a 10s6p, it’s not really charging but still, cells go unbalanced after a longtime. Pretty slow but effective. Now imagine the amount of juice your vesc tries to push to your battery trying to give you the max for your couple of seconds braking
That depends on your pack and your bms. If you buy the right bms this is not an issue.
That’s right. That’s why people go with charge only bms. But again, if you choose the right bms this will also not happen.
If you want to know that, than I can recommend you to get a Bluetooth module and track it. It’s not that much a current you think 
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agree. i was also surprised by the litlle amount it pushed back
“2p 3p or how ever pack for sure the bms will not balance every single cell, only the p pack”
This is not making sense. It does not matter how many cell you have in parallel (those cells in parallel are always balanced since they act like a single cell, they charge each other and drain at the same rate if they are similar). Cells in series need to be balanced (not P), your battery pack, you bought it, that means same voltage on each cell already. I build them, I test many of those lipo chargers (also got that i max b6). What I’m saying is simple and you can rely on it. If your lipo (3s) has
Cell 1: 3V
Cell 2: 3.5v
Cell 3: 4v
If you put it to charge with your imax, charging will stop when cell 3 is 4.20v, and will not care about 1 and 2 (they will not be 4.20v ).
Use a small dc motor and drain one single cell from your pack (through your balance leads), put back the pack in charge until full and you will tell me “now I see what you are saying”
This data sheet is full of what an Original balance charger or advanced BMS should have (even cheap balance chargers come with it lol). I don’t even look at advertisement! I test for myself.
You re just repeating what I said
The right BMS, you have a link for it?
Not that much current, I hope you re not thinking it can be less than the .2 amps from my power supply