Something weird is going on then because I checked the circuit board for a LLT BMS and it has none of the components needed to shift charge from one cell to the other but does have the components to only bleed charge from individual cells.
The Flexi only does passive cell balancing too, just discharging individual cells as needed to balance the pack. Unless by “active” you mean using a MOSFET to switch the individual cell balancing discharge current on/off versus using true charge transfer balancing between the cells?
Could be a different model, i’ll admit ive tried to buy more of these and the perticular 60A discharge model i have, I cant even find a photo of it. Basiclly it shares the same charge discharge port - where most have a seperae port (makes no differeance)
Also it has a UART out port, insead of more Potential Balence pinouts.
To answer your Mosfet question - It Does Balence with MOSFETS on, and when they are switched off . Though the operation does seem slightly different between the two which i think you have explained possibly why.
The flexi BMS is killing cells, but with the same pack i orginally set it up with it balences just fine.
Makes me wonder if there is a benfit to wiring each set of 4 cells +/- So a 10s4p would have an insane amount of leads… so i could just route those outside of enclosure for charging/bal.
Clearly going to have to learn more in the field of battery pack design.
Side note: I do notice some BMS come with Sheilded Balence wires. is this simply to ensure the readings are acurate?
Huh? What is it doing wrong? Which pack is it doing this with?
Some people do bring out leads for each cell for balancing.
I don’t know why they did it but keeping out electrical interference (which can affect voltage reading accuracy) would certainly be the most logical reason. You can still get conducted interference coming down the wires though so filtering and other ways to handle that need to be in place.
That makes sense, I generally also either keep my wires from overlapping or i twist them if the fist option doesnt work.
Though with flexi i did use a extra long silcone 22awg bal leads… folded neatly, wondering if i use sheilded cable if that will improve.
The Sheilded Cable is rated at 105c 600v… to my memory only a few types of insulation go to 105 (i thought it was FEP/and irradiated PVC. I’ll check the cable for the Unique ID and see what it is.
The flexi works great but of course if your pack is 10s but actually 9s… it dosent like that. which is fair.
But i did drain 1 cell from 3.7 to 2.0v. (could be reading issue)
Bought some LCD’s to basiclly wire up to my packs leads so i can watch the progress on a few packs at once. 300 cells 40 at a time takes to long.
Question: Would it be best to make an adapter that splits the balence leads on the male connector plug that goes into the BMS? (can imagine that might kill the lcd’s?) which would mean id need to somehow access the leads on the packs?
Sorry, I’m not sure I understand the question. If you are accessing the balancing leads then I can only recommend doing it in the easiest, most reliable way that jeopardizes the pack the least,
which would be :D? talking to a fella thats blown more cells in the name of ignorant science
Quick learner once i get it though.
All i can see going wrong is as charging is via bal once at a certain voltage. if the connector is split… the current would be split on both wires…as far as i know?)
Sorry, I just don’t understand the scenario you are describing. An image might help.
You want to take the existing balancing harness connector and put a y-connector on it so you can run the balancing leads to an external charge/balance port in addition to the BMS?
You’ll probably want to disable a lot of the BMS’ functionality so it’s not “fighting” your external balancing.
Active balancing on the LTT BMS just means it balances when it’s not charging. It doesn’t have the circuitry to move energy from one cell to another, just bleeding it as heat.
So, Techniclly Some kinda Hybird Diebie/Flexi-lite dr.frankenstein combo would be the ultimate.
Active Balence (Flexi) Charge Balence (Flexi/Diebie)
and Discharge (diebie)
.
In my head it seems right - except i would imagine the Balence wire setup would have to be done in a pertocular way to allow for both to function side by side in their respective roles without treading on eachtoher.
