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First Build... max charge just under 42v  

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djbrandonr
(@djbrandonr)
Street cred = 10 mAh Customer
Joined:4 months  ago
Posts: 3
14/01/2018 10:39 pm  

hi,

 

so just finished my first build of a 10s6p with new 30q cells... after i assembled each row of 6p and squeezed the caps on right i tested each row to mach sure there was voltage, 3.7 on average, in each cap... however as i linked each row to build the main block I didnt do a final test of each and every cell before adding bus bars... at any rate once the block was built it 34v... no biggie.. so charged it up and it stopped at 40v... ideas?

didnt want to rip all the bars off before getting some insight, otherwise i will rip the bars off, row by row, and make sure each cell is making proper connection...

 


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Micah (Vruzend Rep)
(@admin)
Street cred = 5 Ah Admin
Joined:11 months  ago
Posts: 272
20/01/2018 6:54 am  

Do you have a BMS installed on the battery? If you have a BMS, then it could be that it stopped early and began balancing, especially if there are a couple cells that didn't make connection, so it 'senses' a couple lower AH groups and is trying to balance them.

It would be recommended to double check each cell's connectivity before finishing the build. The good news is you would only have to remove bus bars on one side of the battery and not both, in order to be able to measure the voltage of each cell.


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djbrandonr
(@djbrandonr)
Street cred = 10 mAh Customer
Joined:4 months  ago
Posts: 3
29/01/2018 9:50 pm  

i started a thread on endless if you want to check it.. overall all is good and all have connection... 1 cell was low vs the rest of the string and all strings seems to be balanced now  after a few runs of the battery... how ever my max charge is is topping out at 41.6v and Im not sure if that should be considered "good enough" or if i should still be expecting 42 -42.2ish like my other pre-fabbed batteries. If you have any thoughts I love to hear. 

 

thanks

https://endless-sphere.com/forums/viewtopic.php?f=14&t=92382


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Micah (Vruzend Rep)
(@admin)
Street cred = 5 Ah Admin
Joined:11 months  ago
Posts: 272
07/02/2018 6:42 am  

When your charging stops at 41.6, how long do you leave it plugged in after that? If one or more cell groups are a bit low, they can need a slow balancing, which the BMS will allow for but over time. I often leave my battery plugged in overnight. I use a cycle satiator most of the time, which displays how many Ah it has pumped into the battery. I'll often check it at night before going to bed and after it has "finished" charging, when it displays a "charging completed" screen and shows how many Ah the battery took. Then in the morning it will still have the "charging completed" screen, but there will be another few tenths of an Ah in the battery, meaning the BMS allowed the charger to kick on a few times over night while it did some slow balancing. It could be the case in this pack, though its hard to know for sure. If possible, I'd try this to see if the voltage increases a bit overnight. Just remember if you charge any lithium battery overnight then leave your battery in a safe place. I'm sure you did a good job building it but you just never know with li-ion. Maybe the factory was a tiny more humid that day or a microscopic conductor was sealed in the jellyroll, etc... better safe than sorry.


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