Basic Programmable BMS

[agpfl]

I am just wondering if anybody else has used an inexpensive programmable BMS. Over the past year I have built 4 Leaf module based packs utilizing a BMS that can be programmed via a USB cable and has some Bluetooth functionality. I keep seeing what looks like overkill when it comes building the BMS.

[BobBoyce]

Originally Posted by agpfl

I am just wondering if anybody else has used an inexpensive programmable BMS. Over the past year I have built 4 Leaf module based packs utilizing a BMS that can be programmed via a USB cable and has some Bluetooth functionality. I keep seeing what looks like overkill when it comes building the BMS.

I have seen the overkill as well. Spending way more than required to convert to Lithium. Lower cost Lithium conversions are more appealing to the public. With lower cost Leaf modules available, there should be no reason that a 7 module conversion should cost more than buying a new Lead/Acid pack. The original Lead/Acid 48V pack charger should be fine for most of these conversions if you put the BMS in control of it.

I used a preprogrammed simple 14 cell BMS PCB on my 7 Leaf module RXV conversion. I retained my Lead/Acid charger.

I would be interested in a simple programmable BMS for my 2Five conversion that will use 16 of the 100 A/H GBS NiFePO4 cells.

Bob

[agpfl]

I read your install. Your configuration was even more advanced than what I normally do because you are cutting off the AC side of the charger. You have used relays for interlock and bypass.

I have the BMS cut off power on the DC side of the charger if any cell hits 4.2v, or the pack reaches 58.8. I purchase a new Li-on charger for less than $200 that is programmed to turn off about .5v shy of max voltage. So for a 14cell Leaf pack I have the charger cut off at 58.3. This gives me two different forms of protection from overcharging. My charger is the one that normally stops the charging, but the BMS can shut down charging as well if the charger does not do its job.

[izzybird]

W

Originally Posted by agpfl

I read your install. Your configuration was even more advanced than what I normally do because you are cutting off the AC side of the charger. You have used relays for interlock and bypass.

I have the BMS cut off power on the DC side of the charger if any cell hits 4.2v, or the pack reaches 58.8. I purchase a new Li-on charger for less than $200 that is programmed to turn off about .5v shy of max voltage. So for a 14cell Leaf pack I have the charger cut off at 58.3. This gives me two different forms of protection from overcharging. My charger is the one that normally stops the charging, but the BMS can shut down charging as well if the charger does not do its job.

I don’t know what charger you’re using, but a lot of these cheaper Chinese chargers can be easily adjusted to different end of charge voltages if you even slightly know what you are doing. I think charging to 4.1v and never dropping below 3.65v will keep a person in a very safe range and keep balancing to a absolute minimum. There are tons of very inexpensive RC gadgets out there that are very useable on leaf modules as well. I’ve read scores of builds from electric motorcycles to the solar dudes using leaf modules and some go all out while others KISS. I’m keeping it simple.
What BMS are you using if you don’t mind me asking?

[agpfl]

Just google 14S smart bms. I used one like this: https://www.aliexpress.com/item/14S-...794186005.html

[brad2388]

Originally Posted by agpfl

Just google 14S smart bms. I used one like this: https://www.aliexpress.com/item/14S-...794186005.html

What does the bluetooth function give you?

[PingEye3]

Originally Posted by agpfl

Just google 14S smart bms. I used one like this: https://www.aliexpress.com/item/14S-...794186005.html

Hi agpfl,
I just googled that page. That looks very much like the BMS supplied by Nick at EV battery. The PC software pages shown are identical to the PC software I use with the usb-serial programming cable on one of Nick's BMS. Nick did not allow that much control of the BMS parameters by the typical user so he did not supply that cable. His WiFi app showed cell voltages, pack voltage etc., very generic. This looks to be a pretty good BMS to give a try.

What amperage rating did you choose to order from them for your pack? They show on their drawing that all pack discharge current passes thru the BMS. I would choose this one at 320A for 14 cells.

https://www.aliexpress.com/item/80A-...9-bfeb6b43f417

[yurtle]

It doesn't appear to have an HMI, or display/touch panel.

[agpfl]

Originally Posted by yurtle

It doesn't appear to have an HMI, or display/touch panel.

What is HMI?

Do I really need a display/touch panel? No, operationally it has no effect on the pack. Its not like I had a backlit display for my each of FLA batteries, so why would I need or want one for my Lithium modules? I spend around $120 per leaf module which is a similar price per FLA battery, so why would I over-complicate it with an elaborate battery management system that costs more than the whole battery pack itself?

[yurtle]

Originally Posted by agpfl

What is HMI?

AN HMI is an industry term. Human Machine Interface.
http://bfy.tw/LDEp

Originally Posted by agpfl

Do I really need a display/touch panel? No, operationally it has no effect on the pack. Its not like I had a backlit display for my each of FLA batteries, so why would I need or want one for my Lithium modules? I spend around $120 per leaf module which is a similar price per FLA battery, so why would I over-complicate it with an elaborate battery management system that costs more than the whole battery pack itself?

Someone asked why Bluetooth. I answered. Maybe I should have been clearer. So you can use a smart phone, laptop, tablet, anything you already have. Never said you needed it.