Still struggling to fully understand top balancing with bench top power supply

[Sanwizard]

You could just float at 54.4V (3.4V per cell) until the balancer gets delta down to .003V.

That alone should balance your cells well enough for you to have full usable capacity.

ArthurELD, I purchased my BMS based in your overview of the Heltec you bought. I went with the 200a 2a active balance. I purchased from chengdu Heltec automation on Alibaba, which I assumed was the parent company. I noticed the order details indicated a 14-24s string, but the unit I received seemed to be 16-24s. The label looked like it was manuallly manipulated to remove the specs.

I am concerned they sent me a lesser unit, perhaps the 150A version, and ripped me off. I was wondering if you can see a model number in the software of your BMS, so I can double check mine once my batteries arrive through Michael B Caro.

 

[Sanwizard]

Also, did you replace your cables? The BMS shipped with 2 x 7awg cables, which would not handle 200 amps. My batteries are 16 x 280ah 16s for 48v. I woukd have to remove the tamper labels to open up the unit to resolder new wires. I imagine that wouls void any warranty. These 200a 2a active BMS are not cheap at over $200 each. Would love your thoughts and any insights you may have.

 

[ArthurEld]

As far as I know, nobody uses these BMSs for the full amp rating.
I plan to use 100A
I think you'd be asking for trouble using 200A for an extended time.
What size cables would you attach for 200A?

I wouldn't worry about the label. It will probably work for 14s and it is probably the 200A version.
You'll find out when you connect it.

I'm using 4 batteries the same size as yours and I plan to use 200A to charge/discharge all 4. So 50A each.
Even doing that requires a 4/0 cable coming out of my charge controller.

 

[Gazoo]

Also, did you replace your cables? The BMS shipped with 2 x 7awg cables, which would not handle 200 amps. My batteries are 16 x 280ah 16s for 48v. I woukd have to remove the tamper labels to open up the unit to resolder new wires. I imagine that wouls void any warranty. These 200a 2a active BMS are not cheap at over $200 each. Would love your thoughts and any insights you may have.

I agree with ArthurEld. Your effective wire gauge is 4awg and the wires are short. Perfectly capable of carrying 200 amps. I would be more worried about your BMS failing if you plan to run it continuously at the full 200 amps than I would be about the BMS wires.

Having said that you need to connect the negative out of the BMS to a terminal and adjust your wire awg accordingly which will depend on the maximum load as well as the length of wire running from your pack to your loads. I used this voltage drop calculator and other awg calculators to figure out what I need.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

I have a 24 volt 100 amp Overkill BMS and Steve (the supplier) reassured me the two pairs of 12" 10awg wire would be fine for 100 amp continuous loads. I don't plan to ever use the full 100 amps and my BMS will power a 2000 watt inverter.

It would take apx. an 8kw inverter to draw the full 200 amps from your BMS.

 

[Sanwizard]

My Inverter is 6.5KW. It will connect to 2 x 16s 280ah strings, each with a Heltec 200a BMS. I will be connecting them in parallel to the inverter via shared bus bars.
I doubt I will ever use the full 200A, but the charger in the inverter goes to 120A. (MPP 6548). I like to overbuild stuff for reliability, so will most likely be using 2/0 wiring.

 

[ArthurEld]

It sounds to me like you are overbuilding so it should work fine.