eMark
100 kW
Whether 13s, 14s, 17s, etc if only two or four + series runs the length of the pack does not lend itself to positioning the idle 14S balance leads of a BMS or positioning the 14 balance leads for true balance charging. Your wiring description with 8 series strings (4-positive) is less than ideal for fuse wiring and less than ideal for BMS balance leads or balance charging leads. For fuse wiring you need only 2 positive series strings running lengthwise if fuse wires were your only means of pack cell protection (besides the pack fuse).goatman said:16s4p was just an example, im jumping upto 17s4p, the batteries iam using right now are 2-14s4p in parallel wired with a removable 14s 25amp bms I use for charging.
An indication that you aren't abusing your two packs and more likely doing only a 85%-95% charge the majority of time and only a 35%-50% discharge the majority of time. Not sure what you mean by different battery(cell) sizes? Seems like it's just a matter of time before your pack of different battery sizes (mAh capacity) becomes more and more unbalanced with pack cells having different capacities (e.g. possibly as much as + - 50-70mAh high/low variance from the combined 14S4P pack cell mAh average of the 56 cells).goatman said:I play with different battery sizes so my 13s batteries have bms, 14s yes but not when on my bike, 2-15s5p I never balanced charged and after 3000km they were still balanced.
So it sounds like your pack series runs are lengthwise instead of crosswise like this 14S4P pack ... https://i.imgur.com/KPNtKSB.jpg ... https://i.imgur.com/KT4ZbUd.jpg (when i say pack fuse i'm referring to the fuse on the red wire). According to your pack wiring the 4P cells makeup the series strings. That was why i started this thread and as spinningmagnets corrected another member that parallel cells are not always in a "group" but sometimes in a "string". According to your pack description the 4 parallelled strings are connected at the ends making them in affect 4 paralleled series strings. From your description your 4 series runs are lengthwise instead of the 7 series crosswise runs like in those two 14S4P photos? These packs are by EbikeAus ... http://endless-sphere.com/forums/viewtopic.php?f=14&t=93297&sid=27077d11fcc5c01fa46ffc50b82b1240goatman said:My 14s4p have 4-14g positive wires and 4-14g negative wires coming off the pack/ 1 for each P so I pull current straight through pack. then it all gets soldered into 1 positive and 1 negative
Those two photos should help explain how to run your series strings with the provision for attaching the idle balance leads of a BMS and/or attaching balance leads for true balance charging ... https://i.imgur.com/KPNtKSB.jpg ... https://i.imgur.com/KT4ZbUd.jpggoatman said:So when you talk about fusing a battery, what im hearing you say is on a 4p battery you would use two fuses going from 1s to 2s and you would place the fuses in between the 1p and 2p going to the 2s then 3p and 4p going to 2s. and if that is the case I could use only 2 positive wires and 2 negative wires coming off the battery but heavier gauge.
At first got the impression you were running only two series strings the length of the battery with one P-cell of the 4P on each side of the two strings. That arrangement calls for fuse wiring (IMO) when you don't properly incorporate a BMS or provision for properly running the series runs for attaching either the idle BMS balance leads or the balance leads for true balance charging.
If each of your packs has the same cells and each pack when balance charged has the same Ah capacity shouldn't be a problem; especially if each cell is fuse wired for added protection. Being as you say, "I never balanced charged and after 3000km they were still balanced" then why even parallel them together? Just switch over to the other pack when the first one is discharged to (say) 35%. You may even have a watt meter to keep an eye on while riding?goatman said:I'm curious how to protect battery pack A from battery pack B(paralleled) without using a bms while on the bike.
You bottom balance charging is actually discharging, by balance charging i meant until each cell is the same voltage as the highest cell (e.g. 3.2-3.4v until all cells are at 3.4v). It takes forever with a BMS to idle discharge balance. The primary reason i decided to go with a Vruzend kit is for experimenting with cell arrangement, occasionally using a balance charger (when needed), as well as being able to check individual cell voltages with a DMM when necessary.goatman said:I did what I considered a bottom balance. when these cells were in a 2-14s5p with 2 bms wired I took all cells to 3.0v then I parallel charged both packs through a watt meter for 13 or 14 hours? at 2 amps 58.8 and the watt meter said 27ah. cant really remember exactly maybe the bms burned off 2 ah of the 25r packs but the meter said 27ah.
If you can get 3000km and your pack(s) have never been bottom balance charged i'd say your previous source for acquiring relatively inexpensive used cells is GOOD ENUF!goatman said:So my next build will be 2-17s4p and if I like it ill buy a couple bms. then ill worry about getting new higher quality batteries