@linsus I don’t really understand the bridges, between the batteries. To charge the batteries I have balance wires. This is original wiring diagram for my BMS.
The wiring is the same, either you charge them as two separate packs, 6S1P + 6S1P (separate balance wires). Or you parallell wire pretty much everything so they “share” balance leads. Guessing you want the later since you dont want to open it up everytime you charge.
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@linsus Okay great, but will the batteries charge balanced then? And do you approve of the construction I have to make a parallel connection?
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Yes, just make sure they share the series terminal on the “3S” line in prev. picture. Dont know what BMS you have but the chargetime will be minimum doubled with twice the capacity.
Google around abit on how to build your own lithium packs and you can get a better understanding of how and why things are connected.Youtube is a great source as well as this forum where sevral buildthreads exist.
Can also recommend battery university
@linsus okay great, but the way I connected the batteries was also two serie packs, which are then connected in parallel, right? What is exactly wrong with my connection scheme?
It will probably work with the wiring from your first picture. But you’ll have one extra lead to your BMS since they dont share the 3S terminal. Since they’ll physically be two separate packs. Parallell configuration also helps the cells to balance themselves, meaning they try to maintain the same voltage level when connected in parallell. The stronger one will push voltage into the weaker one simply put.
@linsus won’t that overcharge the first battery and undercharge the other battery ruining them in the proces?
I think it would work anyway because they would end up being connected by the balance wires. But it’s better to have a higher-current connection there
yeah, kind of defeats its purpose to connect them in parallell every 3d cell I guess. My mindset is always in li-on 18650…
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Since its segments of 3S I guess it’s not that important since the other cells inbetween will still be isolated. Might as well keep them separate as in your picture. The voltage test becomes even more cruicial now tho since they dont balance of eachother. Try to do half a discharge run and see what voltages you have on each.
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@linsus @b264 So this would basically be the wiring? Or am I missing wires from the other batteries?
You need to join all the balance wires from parallel cells together or havee two seperate bms/chargers. Remember to only add these connections after a full balance charge, if the packs have significantly different voltage when you parallel them it can be very dangerous.
Only dangerous if you try to charge them before they all balance with each other. Best safe practice is to plug all the batteries together including balance leads and then wait a couple of hours to let them all balance out prior to charging.
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If one cell is at 4.2V and the other 3.2V you will probably exceed the max charging amps of the 3.2v cell and most likely start a fire.
No; B3 needs to be connected to both batteries.
You should never run your battery down to 3.2v lipo or li-ion. The max percentage that you should run a battery down is about 80% of the capacity. I found that stopping at 3.50-3.60v per cell is a rough guesstimate on the amount of battery used. It also helps with battery longevity by not draining your batteries that low.
Not sure where that information is coming from? Pretty much any device you use lets the battery run down lower than 3.6v. 3.7v is the nominal cell voltage 3.6 is far from dead.
I have charged a couple thousand batteries over the past few years flying, racing drones. I use and charge batteries on parallel charging boards on a daily basis. I always put my batteries on a parallel charging board and let them sit there for a while prior to beginning the charge in order to give all he batteries the chance to balance out. By doing so I have never had a lipo fire because I utilize go battery management. The point i was trying to make is by hooking up the batteries together as well as the balance leads that takes the place of the parallel charging board. I know 3.7volts is nominal I have found over the past years and charging and flying 20-30 packs a day (when I am home). Running your batteries in particular lipo down past 3.5v on a regular basis will shorten the life span of your battery. I’ll digress because I don’t want to ruffle any feathers. I’m just here trying to give some insight.
My point is just for an inexperienced user, if you had a fully charged lipo and a fully discharged lipo according to regular values (commonly listed at 2.8-3v industry standard) and connected the two, bad things might happen. It sounds like thats not something you are ever doing.
A few tenths of a volt is totally fine. Think about with your current limiting charger, it doesn’t hit the pack with 4.2v right away most often. If it did battery damage might ensue, and no one wants damaged batteries.
Without specifying whether you’re referring to li-ion or lipo, this could be slightly misleading. These look like lipo numbers.
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