Series wiring 36v batteries

[Dalimar]

I have two 36v batteries here but only one has the output protected by bms and it's only lvc. Can this one go before the unprotected pack without a diode? And if so can i use an ideal diode? Where would i place it?
They are identical packs with the same manufacturer and ah rating .

 

[n00b]

Idk, but I have wired 2 36v Liitokala batteries in series and it worked great until physical damage.
Batteries slammed into bike tube and arced. Can't even get batteries that small and light with same capacity now.
Tomorrow I try to keep that from happening again. With plywood n packing stuff.
I would use the BMS one in series before the un-BMS one. Hopefully not the wrong idea.
My batteries were identical.

 

[docw009]

The failure comes if a BMS on two batteries in series opens up, its switch transistors has to withstand at least 84 volts. Depends on the breakdown voltage of the transistor selected for the BMS. You can always look them up.

Here's a 10S BMS and a close up of the four switching MOSFET's. They are RU6888R, which are rated for 68 volts and 88 amps. If I used this BMS in a series arrangement, the MOSFET's could blow up if the BMS opens. If the transistors blow open circuit, the battery won't work. If they short circuit instead, then the BMS is bypassed an the battery is always on. Now you can overcharge the cells or run them too low, both of which can lead to fires later,

A designer probably won't choose 100V transisors for a 36V BMS. It costs more money for the higher voltage transistors.

 

[Dalimar]

The failure comes if a BMS on two batteries in series opens up, its switch transistors has to withstand at least 84 volts. Depends on the breakdown voltage of the transistor selected for the BMS. You can always look them up.

Here's a 10S BMS and a close up of the four switching MOSFET's. They are RU6888R, which are rated for 68 volts and 88 amps. If I used this BMS in a series arrangement, the MOSFET's could blow up if the BMS opens. If the transistors blow open circuit, the battery won't work. If they short circuit instead, then the BMS is bypassed an the battery is always on. Now you can overcharge the cells or run them too low, both of which can lead to fires later,

A designer probably won't choose 100V transisors for a 36V BMS. It costs more money for the higher voltage transistors.

An ieal diode is usually rated for 600v and 80amps Isn't necessary in my use case i take it? Which would be great my 750 watt hub motor that was sold as 36v can't climb a 3 degree incline and overheats at 36v but works great at 60v. I couldn't keep the 60v battery but i can series two 36v batteries. I was already invested in 36v beforehand.
I only have 1 bms on this string, one battery only uses bms for charging and the other has bms on the output.

 

[Dalimar]

Idk, but I have wired 2 36v Liitokala batteries in series and it worked great until physical damage.
Batteries slammed into bike tube and arced. Can't even get batteries that small and light with same capacity now.
Tomorrow I try to keep that from happening again. With plywood n packing stuff.
I would use the BMS one in series before the un-BMS one. Hopefully not the wrong idea.
My batteries were identical.

Yeah mine are quite heavy, their completely potted and they have silicone molded into them for physical shock and vibration protection. Pain in the butt but it's what i could afford.

 

[Dalimar]

The failure comes if a BMS on two batteries in series opens up, its switch transistors has to withstand at least 84 volts. Depends on the breakdown voltage of the transistor selected for the BMS. You can always look them up.

Here's a 10S BMS and a close up of the four switching MOSFET's. They are RU6888R, which are rated for 68 volts and 88 amps. If I used this BMS in a series arrangement, the MOSFET's could blow up if the BMS opens. If the transistors blow open circuit, the battery won't work. If they short circuit instead, then the BMS is bypassed an the battery is always on. Now you can overcharge the cells or run them too low, both of which can lead to fires later,

A designer probably won't choose 100V transisors for a 36V BMS. It costs more money for the higher voltage transistors.

After reading through this again, it seems i need a diode, i misunderstood until proof read.