RXV and locked breaks on battery disconnect

[MrBritGolfFan]

Hi all. Thank you upfront for any assistance and help!

I have an in-line 300 amp fuse from my lifepo4 pack to my Navitas 600Amps tac 2 RXV controller.

If that fuse blows I am under the impression the cart will come to an immediate stop. If I’m doing 20+mph I might be thrown out a bit :)

So, are there any ideas or suggestions on how I could make sure the RXV does not come to a sudden stop if the fuse from the pack were to blow?

Or am I wrong in stating the RXV would just lock the motor brake?

[molfpedal]

Originally Posted by MrBritGolfFan

Hi all. Thank you upfront for any assistance and help!

I have an in-line 300 amp fuse from my lifepo4 pack to my Navitas 600Amps tac 2 RXV controller.

If that fuse blows I am under the impression the cart will come to an immediate stop. If I’m doing 20+mph I might be thrown out a bit :)

So, are there any ideas or suggestions on how I could make sure the RXV does not come to a sudden stop if the fuse from the pack were to blow?

Or am I wrong in stating the RXV would just lock the motor brake?

You are correct in your assumption about the motor brake. I have a 400 amp in line fuse. It is doubtful that you would ever see enough current to blow the fuse while cruising. In my estimation you would only see anything in excess of 200a on acceleration from a stop. So I would imagine you would be going considerably slower than 20mph.
Before I switched to lithium one of my battery connectors broke at 15mph and the cart locked up. I was able to stay in. Barely.


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[MrBritGolfFan]

Originally Posted by molfpedal

You are correct in your assumption about the motor brake. I have a 400 amp in line fuse. It is doubtful that you would ever see enough current to blow the fuse while cruising. In my estimation you would only see anything in excess of 200a on acceleration from a stop. So I would imagine you would be going considerably slower than 20mph.
Before I switched to lithium one of my battery connectors broke at 15mph and the cart locked up. I was able to stay in. Barely.


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Thanks molfpedal. I just feel real nervous about it all as have three small kids and worry we could one day have a bad accident. We keep around 24-27mph and don’t care for the speed but still wouldn’t want it to happen.

That’s also a good point you make. The surge happens with torque and usually from starting. I did buy a 500amp fuse that I might consider switching out. Especially now that I know Navitas have written in lithium settings that can be based around your discharge amp rate on your pack and also the surge amps for x seconds. That might negate the need for the fuse altogether perhaps?

[Sergio]

Those fuses will not blow on regular usage, they are really intended to protect the pack and wiring in case of a short of someone dropping a wrench causing a direct short.

A direct and non-fused short on a Lithium pack is very dangerous.

The 300 amp fuse can pass more than 500 amps for 10 seconds before blowing:

ANL 300 Amp fuse datasheet

[MrBritGolfFan]

Originally Posted by Sergio

Those fuses will not blow on regular usage, they are really intended to protect the pack and wiring in case of a short of someone dropping a wrench causing a direct short.

A direct and non-fused short on a Lithium pack is very dangerous.

The 300 amp fuse can pass more than 500 amps for 10 seconds before blowing:

ANL 300 Amp fuse datasheet

Good stuff. Thanks for posting the sheet Sergio!