BMS cutoffs in EV

[AndreMalta]

Hi all

I have a compact car converted to EV using a 48v series wound DC motor with the following basic setup:

• 16s Winston Cells LYP300AHA
• Elcon charger outputting 58.4v 25A
• JLD404 connected to a shunt for visually monitoring Volts, Amps, and Ah usage. This also has two internal relays (J1 & J2).
  • I am using one of them to disconnect the charger
  • The other one sounds a warning when the voltage is getting low

The batteries are quite old and I am starting to see some cell drift. To try and get some additional life out of them I am looking into adding a layer of protection.

Since these are traction batteries, current draw varies wildly. e.g. standing still at 10A in traffic one moment, accelerating for a few seconds at 350A the next, and cruising at 120A. Similarly, voltage can briefly go dangerously low on hard acceleration but goes back to a stable range for long enough to get me back home.

My main concern with BMS systems is with overcurrent and under voltage protection. I wouldn't want to be in a position where the BMS completely shuts off because of a small peak in use, leaving me stranded.

My question is, am I better off fitting a set of active cell balancers and continue monitoring manually? Or are there any BMS that can cope with these peaks by e.g. turning themselves back on and/or have a tolerance of time before it trips?

I have gone through a number of threads on this forum but cannot quite find an answer to my question yet. I have also tried communicating with Daly about their newish 300A-500A variants however the language barrier is not helping me get the answer I am looking for.

Any help would be appreciated.

 

[Steve_S]

I tinker with EV's but don't talk about it on here as a matter of course (this isn't the forum for it). This spring we are building two E-Mud-Trucks with serious whoopie potential... hehehe... EV's and LEV's most typically use BMS with Relays (Tesla, VW, BYD, GM, Ford and everyone else does too) because relays are the only way to really manage that kind of loading, reliably. GM uses Panasonic Relays and they can be had fairly easily but they are not cheap. Alternately Gigavac & TE/Kilovac Energy Saver relays are commonly found in various EV's & LEV's.

To give you an example of an Appropriate EV BMS subsystem look at these two examples below:
NOTE the details and interfaces.

100A~1000A Battery Management System,Programmable BMS with CANBus, RS485, RS232, UART Communication protocol-BesTech Power Co., Ltd

BesTech Power designs and produces battery protection circuit module,battery protection circuit board,battery managemant system,PCM,BMS,PCB,BMS for 4S 14.8V 3S 12.6V battery Packs

bestechpower.com

100A~1000A Battery Management System,Programmable BMS with CANBus, RS485, RS232, UART Communication protocol-BesTech Power Co., Ltd

BesTech Power designs and produces battery protection circuit module,battery protection circuit board,battery managemant system,PCM,BMS,PCB,BMS for 4S 14.8V 3S 12.6V battery Packs

bestechpower.com

You will see the interfacing for guages & monitors along with relay con\trols for heating/cooling battery system. CANBUS interface as well to support standard motive interfacing... few realize it but CanBus was invented for automotive electronics interfacing.

 

[AndreMalta]

I tinker with EV's but don't talk about it on here as a matter of course (this isn't the forum for it).

That would explain why I have not found my answer I was drawn to this forum by Will's excellent teaching skills on youtube

This spring we are building two E-Mud-Trucks with serious whoopie potential... hehehe... EV's and LEV's most typically use BMS with Relays (Tesla, VW, BYD, GM, Ford and everyone else does too) because relays are the only way to really manage that kind of loading, reliably. GM uses Panasonic Relays and they can be had fairly easily but they are not cheap. Alternately Gigavac & TE/Kilovac Energy Saver relays are commonly found in various EV's & LEV's.

To give you an example of an Appropriate EV BMS subsystem look at these two examples below:
NOTE the details and interfaces.

100A~1000A Battery Management System,Programmable BMS with CANBus, RS485, RS232, UART Communication protocol-BesTech Power Co., Ltd

BesTech Power designs and produces battery protection circuit module,battery protection circuit board,battery managemant system,PCM,BMS,PCB,BMS for 4S 14.8V 3S 12.6V battery Packs

bestechpower.com

100A~1000A Battery Management System,Programmable BMS with CANBus, RS485, RS232, UART Communication protocol-BesTech Power Co., Ltd

BesTech Power designs and produces battery protection circuit module,battery protection circuit board,battery managemant system,PCM,BMS,PCB,BMS for 4S 14.8V 3S 12.6V battery Packs

bestechpower.com

You will see the interfacing for guages & monitors along with relay con\trols for heating/cooling battery system. CANBUS interface as well to support standard motive interfacing... few realize it but CanBus was invented for automotive electronics interfacing.

That opens a whole new world for me to explore and a lot of more research to do! Thank you very much for linking the products Steve it's extremely insightful