Lithium Golf Cart Fire

[expoman55]

Man I am glad you and your family is ok. I am sorry for the loss. that buggy looked so clean and well cared for don't know what to say. Have to be honest this battery fire stuff scares the daylights out of me. I read previously about a LA battery set causing a fire now this.. I am actually starting to think we shouldnt park our carts in our garages regardless of the tech. I just converted to Allied Lithium. each of their batteries have an on board bms. My wiring is CLEAN as CLEAN gets and new and I check my roc meter all the time.. Charge ONLY from day one with a smart charger for lithium but still ... but all that said. For every one that has an issue like anything else there are thousands that don't and haven't been cared for ... Again sorry for your loss Glad you are all ok.

OP can you tell us what charger make and model was last used on this cart? If you don't know, do you have a pic of it? I'd like to understand if the charge cycle was supposed to time out and failed to do so. Additionally, I'd like to understand its intended charge profile.

Sorry for your loss and thanks for making us aware.

[UpstateNYDS]

Originally Posted by Pat911

That voltage info is correct for 14s NMC chemistry.

Now I'm confused

[CP241]

Originally Posted by UpstateNYDS

Now I'm confused

That’s the LiFePO

The NMC chemistry is different and much lower voltage tolerances. Seems that the NMC would be better suited for solar or RV maybe… but not as desirable for a golf cart.

https://bigbattery.com/Manuals/FHBGR-48012-G1.pdf

[Pat911]

To clear up some confusion, NMC maximum voltage is 4.2v/cell, LiFePO4 is 3.65v/cell.

All things being equal, NMC has a higher specific energy and higher currents than LiFePO4 so it is more suited to carts than LiFePO4 but it is also more volatile and less tolerant to abuse, hence more dangerous than LiFePO4. But, used within specifications and matched to a capable BMS, it is very safe to use. I have NMC in my cart.

When making a “48v nominal battery”, 14s is used for NMC and 16s is used for LiFePO4. When I write 14s or 16s what I mean is 14 or 16 cells in series.

Now, 14 x 4.2 is 58.8v maximum charge voltage for a 14s NMC battery. 16 x 3.65v is 58.4v maximum charge voltage for a 16s LiFePO4 battery. These limits should never be exceeded.

The specs that CP241 linked to above is an example of a battery manufacturer cheating and only using a 12s configuration for a 48v nominal battery. A 12s NMC battery is only 44.3v nominal. For charging, 12 x 4.2 is 50.4v. But, even using a 58.8v charger, the BMS should have protected the pack.

The fire described here was caused by a BMS failure. Even if the charge voltage was too high, the BMS should have intervened and stopped charging. That’s its job. With a working BMS, a lithium battery, no matter what chemistry, is safe to use.

Cheers
Pat.

[chelmuth]

No I wasn't using a BB charger, I switched to a dakota lithium charger that had been recommended for this type of battery. I went back and took a look at the specs and realized it wasn't recommended for the NMC chemistry. Now that I know this, I guess i'm still a bit puzzled what would have caused the BMS to fail...

[chelmuth]

Agreed, the only reason I allowed it to be parked inside was because I felt very comfortable knowing these batteries had a BMS

[dundeebarnbuggy]

Let us know how you make out with your insurance company, as they generally frown upon client modified electrical systems, especially if they cause a fire.

[UpstateNYDS]

That makes sense Pat, thanks.

Originally Posted by Pat911

To clear up some confusion, NMC maximum voltage is 4.2v/cell, LiFePO4 is 3.65v/cell.

All things being equal, NMC has a higher specific energy and higher currents than LiFePO4 so it is more suited to carts than LiFePO4 but it is also more volatile and less tolerant to abuse, hence more dangerous than LiFePO4. But, used within specifications and matched to a capable BMS, it is very safe to use. I have NMC in my cart.

When making a “48v nominal battery”, 14s is used for NMC and 16s is used for LiFePO4. When I write 14s or 16s what I mean is 14 or 16 cells in series.

Now, 14 x 4.2 is 58.8v maximum charge voltage for a 14s NMC battery. 16 x 3.65v is 58.4v maximum charge voltage for a 16s LiFePO4 battery. These limits should never be exceeded.


The specs that CP241 linked to above is an example of a battery manufacturer cheating and only using a 12s configuration for a 48v nominal battery. A 12s NMC battery is only 44.3v nominal. For charging, 12 x 4.2 is 50.4v. But, even using a 58.8v charger, the BMS should have protected the pack.

The fire described here was caused by a BMS failure. Even if the charge voltage was too high, the BMS should have intervened and stopped charging. That’s its job. With a working BMS, a lithium battery, no matter what chemistry, is safe to use.

Cheers
Pat.

[Pat911]

Originally Posted by chelmuth

No I wasn't using a BB charger, I switched to a dakota lithium charger that had been recommended for this type of battery. I went back and took a look at the specs and realized it wasn't recommended for the NMC chemistry. Now that I know this, I guess i'm still a bit puzzled what would have caused the BMS to fail...

Not true at all. The chemistry has nothing to do with what type of charger you use, it is only the voltage that you must look at. All lithium batteries are charged with a current limited constant voltage power supply (Charger).

You can use a 58.4v lithium charger for both NMC and LiFePO4 but you cannot use a 58.8v charger for LiFePO4 as it’s voltage is too high.

Your issue is that your battery is not a “standard” 48v lithium battery, it is two cells short of that, therefore limiting its maximum charge voltage to 50.4v. What was the voltage specified on the Dakota charger you were using, 58.4v?

As to what caused the BMS to fail, I don’t have an answer for you. I’m assuming that the BMS is wired correctly and is protecting both charging and discharging.