Custom Bluetooth BMS on Master

[daniel1234]

Hi
I would love to have Bluetooth BMS on mine master and build mine own pack - Main reason is to see if pack are balanced and I can drain battery to 0 safely. There is a lot of smart cheap BMS on market we can use. But, there is some communication between EUC and packs via that white wire - anybody tried to investigate that ?

regards

[Chriull]

40 minutes ago, daniel1234 said:

Hi
I would love to have Bluetooth BMS on mine master and build mine own pack - Main reason is to see if pack are balanced and I can drain battery to 0 safely. There is a lot of smart cheap BMS on market we can use.

Be carefull with single cell undervoltage cut off! This is normally activated in standard BMS - as also early EUCs used. 

Burdening such a battery at low charge states lead to nasty faceplants...

So this battery safety feature is disabled wirh all EUCs by now!

40 minutes ago, daniel1234 said:

But, there is some communication between EUC and packs via that white wire - anybody tried to investigate that ?

The additional sync line between the bms is shut off all battery packs at the charge side once one sees single cell overvoltage.

Without this sync line this pack with single cell overvoltage would still be charged through the discharge side by the other packs...

 

[daniel1234]

1 hour ago, Chriull said:

 

The additional sync line between the bms is shut off all battery packs at the charge side once one sees single cell overvoltage.

 

I don't see any voltage there, I was thinking it is something more complex like serial bus communication - any idea what state/voltage/signal trigger that behavior ?

For discharge I will bypass BMS anyway and add XT60 key to have ablity to unplug battery for storage  - I will rather destroy cell and replace it, than nosedive at high speed.

[Chriull]

15 minutes ago, daniel1234 said:

I don't see any voltage there, I was thinking it is something more complex like serial bus communication - any idea what state/voltage/signal trigger that behavior ?

Should be in the link i posted.

15 minutes ago, daniel1234 said:

For discharge I will bypass BMS anyway and add XT60 key to have ablity to unplug battery for storage  - I will rather destroy cell and replace it, than nosedive at high speed.

Even Begode decided to implement a short circuit protection with their BMS now...

[meepmeepmayer]

Heyo, I split this off into its own thread because it's an entirely different topic, so people can find it better like this

[alcatraz]

How about attaching 8S balancing leads (JST-XH)?

Every once in a while plug in a little tester and check.

I know that people that fly RC have testers connected while flying because they're equipped with low voltage audible alarms for when it's time to land. I think the voltage is programmable and all the stuff costs nearly nothing. Peanuts.

Qustions are. Can you protect the balancing leads? Can you hear the alarms while riding?

[daniel1234]

On 7/15/2022 at 11:34 AM, alcatraz said:

How about attaching 8S balancing leads (JST-XH)?

Every once in a while plug in a little tester and check.

I know that people that fly RC have testers connected while flying because they're equipped with low voltage audible alarms for when it's time to land. I think the voltage is programmable and all the stuff costs nearly nothing. Peanuts.

Qustions are. Can you protect the balancing leads? Can you hear the alarms while riding?

in theory yes. I am seriously thinking about making 4 x 8s2p out of p42A to have lightweight off-road wheel with half battery capacity and thinner - better s18.