Safest battery configuration - LTO or LFP?

[Jacob Scoville]

So I came across a post here about a LTO bank failure. Now the quality of the build was highly in question, but it got me thinking. With the extra potential surge of power from LTO cells, are they really safer? The cell might not catch fire but it could still start one. Could LFP potentially be safer since those cells typically have lower output at once?

Cost isn’t a concern, extra space isn’t the end of the world, and the vehicle will regularly be below freezing, and will for sure be below 0F° inside at times, so the simplicity of cold proof LTO cells seemed favorable. But watching one too many battery fires online has me chasing for the ultimate safe setup and the best most overbuilt failsafes.

If a BMS were to fail, what prevents undesirable outcomes?

 

[wpns]

Doesn't matter if the batteries are completely safe, if you have the possibility of thousands of amps of short circuit current, you are going to have danger. BMS, FETs, contactors, T-class fuses, all of the usual overcurrent protection devices are necessary, and the care with which they are selected and implemented will determine the final 'safety' of the system.

 

[AntronX]

If a BMS were to fail, what prevents undesirable outcomes?

You can have another cell voltage monitor to open batt contactor if things go wrong. For ultimate fire protection I would place battery inside steel container and dump water into it if fire is detected.

 

[Jacob Scoville]

Doesn't matter if the batteries are completely safe, if you have the possibility of thousands of amps of short circuit current, you are going to have danger. BMS, FETs, contactors, T-class fuses, all of the usual overcurrent protection devices are necessary, and the care with which they are selected and implemented will determine the final 'safety' of the system.

Oh for sure! It will never be 100% but I like to be as safe as possible. That’s why I was curious if LTO’s could actually be more dangerous because they can(?) output more amps at once for the same capacity(?)

At least I’d assume as much since the charge/discharge rates are typically much higher.

(For use case reference I’d put in a 24v 75a LTO to replace my 24v 100a LFP setup).

 

[Supervstech]

Oh for sure! It will never be 100% but I like to be as safe as possible. That’s why I was curious if LTO’s could actually be more dangerous because they can(?) output more amps at once for the same capacity(?)

At least I’d assume as much since the charge/discharge rates are typically much higher.

(For use case reference I’d put in a 24v 75a LTO to replace my 24v 100a LFP setup).

No.
Output capability is negligible in the safety factor.
FUSE for safety.
Use proper fuses.
Use correct or oversized wire
Use correct terminals.
Set proper charge and discharge parameters.
If 0F is likely, you for SURE want heated, or at least monitored LFP... LTO i am not sure it can even charge that low.

 

[frankrudis65]

Hi there, for me-and I was asking myself for quite some time- every bms should have on every single cell a heat sensor.Like this some of the concerns could be ruled out.And then maybe a heat-sensor-camera with alarms....I have heared some,they build above the battery rack some sort of sand container,which gets released when the eggs get boiling

 

[zcskywire2]

LTO will charge down to -40C with ~65% total capacity available, ~85% at -20. There are also cold weather LFP cells coming with 90% efficiency at -35C