please check my BMS wiring

[dlwilson]

I've been using a lot of these Chevy Volt modules, at $110 shipped for 48v lithium rated at 20-22AH. https://www.greentecauto.com/hybrid-...battery-module

I don't use a BMS with them, and instead initially balance the cells manually using a headlight as a load to discharge each cell to get them equal. But that's a pain, and I want to use a BMS to charge and balance them. It's a 12S battery, so I got this BMS off eBay https://www.ebay.com/itm/323217175378 I'm thinking that at $18 maybe I can just leave the BMS on there fulltime for charging.

The BMS is only rated at 15A. I charge at 2-4A, so that should be fine, but the BMS won't work for discharging at 200-300A.

If I don't want to use the BMS for discharge, do I still need the wire from B- on the BMS to negative on the battery? Doesn't the charging current all go into the battery through the positive terminal on the battery, and return to the charger via the individual wires to the cells? That's how the BMS is able to monitor and balance the cells? Then I would attach the load (controller/solenoid/motor) directly to the positive and negative on the battery, and discharge that way?

Here is the wiring diagram provided by the seller:


Here is a diagram I made here a few years ago in this post: https://buggiesgonewild.com/showpost...95&postcount=9

[simicrintz]

I don't see the seller diagram. My initial build was a Chevy Volt system (2 batteries in parallel) so I am interested to see what was provided. I bought my batteries from an older gentleman in Northern California (I have tried reaching him semi recently but no reply) and am wondering if your info matches what I may still have.

[TheCartBoy]

That BMS is not suitable. You want all charge and all discharge current to be monitored by the BMS. You also want all cells to be monitored by the BMS, which means you need 1 BMS per Chevy module since you are adding them in parallel to your cart.

How many amps are pulling per pack? Perhaps an 80 amp JK BMS would be good for each, they aren't too expensive.

[dlwilson]

Originally Posted by simicrintz

I don't see the seller diagram. My initial build was a Chevy Volt system (2 batteries in parallel) so I am interested to see what was provided. I bought my batteries from an older gentleman in Northern California (I have tried reaching him semi recently but no reply) and am wondering if your info matches what I may still have.

The seller diagram is the first one, with the thirteen batteries at the bottom. It shows up for me, hopefully you can see it.

[davros]

So it is kinda a "poor man's" resistive BMS and you only want to use the balancer

AFAIK:
The sense wires would normally only 1) sense the voltage and 2)pass the balancing currents.
If you want the charge current to be cut off at max volts you need it wired as drawn.

Won't help you with low cell voltage cutoff tho

[dlwilson]

Originally Posted by TheCartBoy

That BMS is not suitable. You want all charge and all discharge current to be monitored by the BMS. You also want all cells to be monitored by the BMS, which means you need 1 BMS per Chevy module since you are adding them in parallel to your cart.

How many amps are pulling per pack? Perhaps an 80 amp JK BMS would be good for each, they aren't too expensive.

I've been running these battery packs for years with no BMS at all. I think it would be an improvement just to have charging current monitored. Do I need the connection in question if I don't use the discharge protection?

I don't know how many amps I'm pulling. This particular battery is going into an older EZGO serial cart that's been converted to 48v by upgrading the 1205 controller and solenoid.

[davros]

How many packs in parallel?

[dlwilson]

Originally Posted by davros

How many packs in parallel?

This is just one pack. It's for a friend who's ex put six small 36v lithium cells in their EZGO, which they got at a yard sale for $200. It would get them around downtown with a mile of range, but those cells finally died. I converted the cart to 48v and put in one battery pack this weekend. I'm finishing the wiring now. The battery will get a 3d printed top.

[TheCartBoy]

Originally Posted by dlwilson

I've been running these battery packs for years with no BMS at all. I think it would be an improvement just to have charging current monitored. Do I need the connection in question if I don't use the discharge protection?

I don't know how many amps I'm pulling. This particular battery is going into an older EZGO serial cart that's been converted to 48v by upgrading the 1205 controller and solenoid.

We didn't have great off the shelf BMS with all protection modes and able to handle high currents years ago, and even until within the last couple years, they were very expensive.

Just because it worked fine so far doesn't mean it doesn't have risk. At this point IMO, the risk is higher than the cost of doing it right and either installing a proper BMS or retiring that pack and getting something new with safety in mind.

[WalterM6]

Back before everybody was buying store-bought batteries and everybody had DIY batteries the main drive current was never run through the BMS. The BMS function mainly was to balance the batteries. The overcurrent was handled by the controller. For ideas on how to connect it up search for some of the posts by Sergio. There may even be a post about Chevy Volt batteries