starts smoking on BYD pair: JW 17cell battery balancing v2.4

[solarHandyman]

For reference: https://www.amazon.com/Li-ion-Lifep...ds=16s+battery+balancer&qid=1614110048&sr=8-4

Hi, I have 4 pairs of the infamous BYD 24v batteries (Tech Direct, BatteryHookup, BatteryClearingHouse), wired in pairs for 48V. To manager the entire group of 16 cells, when connecting this simple battery balance board (not a BMS) the board starts smoking and it looks like it wanted to catch fire (can't learn anything without a couple dead shorts catching fire I pulled the plug before that happened. I only tried connecting one. Same result 12 hours later after calling it a night....

My batteries are not exactly top balanced. I just got a little bench top variable power supply tester off Amazon which only does 300 watts max to get them up from below 25 volts as they were when purchased at Battery Clearing House in Raleigh.

Is my issue that my difference in voltages between the two 8s packs are just too great for the board and its little chips to handle? If I could get all my packs within 0.5 volts, would this little board work out for me?

I didn't want to go with a $100 BMS because low temperature/high temperature cut offs and low voltage disconnects are not an issue for my installation.

Any help would be appreciated comrades

 

[codfish]

Well smoke probably means the boards are now dead, and better double check your connections, but...
These inductive balancers can usually be hooked up with less than the number of cells, just start at B- and work up. So you should be able to balance each 8s pack individually. Leave the balancers on each 8s pack and
Then hook the two 8s in parallel, use some resistance between them when you first parallel them. After some hours the packs should be at the same pack voltage, and similar cell voltages. then you can hook them in series. Check pack and cell voltages before proceeding. Once everything is similar a 16s balancer spanning the two packs should be ok.

 

[solarHandyman]

Is the resistance required when paralelling the two 8s packs to prevent sparks/smoke when connecting them? Or a dangerous current flow from one to the other?

 

[codfish]

Just a precaution for excessive current flow (and should eliminate spark / smoke)

As I've thought about it...
These inductive balancers only work on pairwise cell voltage differences. Hence the pack voltage difference doesn't really matter. What matters is the individual cell voltage difference between cell 8 voltage and cell 9 voltage. It's a little hard for me to imagine that those two cell voltages were so far different that it caused smoke. But you can measure those voltages now.

I'm leaning towards either a faulty board or something mis-wired.

 

[Maast]

I've got 18 of those BYDs and you're going to need a BMS AND a very hefty balancer. The cells in the BYD modules are so badly capacity mismatched that their voltages will differ wildy during your charge/discharge cycles and you will (not can - will) drive a cell into over discharge or over charge and permanently damage it or kill it altogether. A BMS is absolutely mandatory, especially with these turds.

You need the BMS for cell-level monitoring to cut the charge/discharge if one cell or cell group runs away. A inexpensive Daly can do it. And as far as your balancer goes I highly recommend the inexpensive Heltec 5A capacitive balancers. Dont use the induction ones, they're crap.
https://heltec-bms.com/product/5a-capacitive-active-equalization-active-balancer/

I also STRONGLY recommend you parallel your cells at the cell level - it somewhat averages out the mismatches. I also strongly recommend you get a good top balance, then do a discharge test to find out your weakest 3 or 4 cells/cell groups, then add capacity in the form of 'booster' cells. 15AH to the worst two, then 8AH to the next worst.

Adding capacity to the weak ones will let your pack charge/discharge a lot more evenly and give you a good bit more overall capacity by preventing the weakest cell from dropping out a prematurely causing a pack disconnect.