BMS for GBS LFMP 40ah 4-Pack Lithium Setup

[jonmiles]

Hi,
I have never added a BMS to a battery pack and I need advice. I have 4 GBS LFMP 40ah cells (each 3.2v). I am planning on running all 4 of them in series to achieve a 12.8v 40ah pack. Should I have a BMS for my cargo bike project with a Lynch motor? If I should get one, can anyone advise what to get. I am mostly concerned about not overdrawing the battery, too much or too low, for safety reasons. I understand that these cells are more stable than most and that makes me wonder if I need any management systems at all. Thank you for your input.

 

[john61ct]

Opinions will vary, little consensus.

Mine is primarily not to **really** trust any, even if it costs thousands.

Wire so that it is easily removed when the lack is not in use

easily replaced when it fails.

Understand the failure modes

verify proper operations regularly.

Diagnose cell health independently,

balancing may be done separately.

In the end "a BMS" is a collection of functionalities, and dozens of excellent ways to gain each goal

without expecting one device to do it all without you paying attention.

 

[jonmiles]

Thanks John! Sounds reasonable. Where would you source a BMS for this application?

 

[john61ct]

If I knew I would have linked to it.

The BT thread has several cheap options people say are great.

A few swear by the Chargery units.

Energus Tiny BMS is at a higher level, as are Zeva and Orion.

https://endless-sphere.com/forums/viewtopic.php?t=104246#p1522183

 

[jonyjoe303]

chargery is a good bms all around. I use it on my 220 ah 4s lifepo4. The chargery bms8 cost around 100 dollars, it uses contactors/relays (not included) to stop the charge/discharge so it can handle as many amps as your contactor can handle. I use a 4 dollar 30a automotive relay to stop the charge, for discharge you can find 200 amp relays for 15 dollars. It also has audio alarms to warn of overlimits besides triggering the relays, 1.2 amp per cell balancing and 2x temp sensors. It has a good LCD screen to show all cell voltages. And since it can monitor current use with a shunt, it can trigger the relay if the motor uses more current then what you program. All the parameters are programmable from the LCD control box. This bms is good when you like to fast charge your battery and want max performance.

picture of chargery bms8, doesnt show all the wiring or shunt that come with the unit.

 

[jonmiles]

Thanks John! I'm going to follow your lead and go with Chargery