RXV HV/LV BMS Shutdowns

[molfpedal]

Originally Posted by MrBritGolfFan

This is excellent news. I have this issue, and i thought i may have to live with it. I use a navitas controller, and a 42.9v LiFePO4 battery from bigbattery - https://bigbattery.com/product/lifep...-cart-battery/

I have some issues where the navitas is shutting down on LV because this LF Pack range is 35-46.8v - however i dont like the immediate stops for sure!

Do you have any additional photos of how you did this on the RXV you can share please?

I'll have to get them together and mark them up a little. Maybe by the weekend.


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[MrBritGolfFan]

Originally Posted by molfpedal

I'll have to get them together and mark them up a little. Maybe by the weekend.


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Thank you Molfpedal!

[MrBritGolfFan]

Originally Posted by molfpedal

I'll have to get them together and mark them up a little. Maybe by the weekend.


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Molfpedal the BMS on this battery pack i got says 130A on the side, however in my tests of using a clamp meter around one of the battery leads shows me i was able to pull 250+ amps and the BMS didnt shut down. My question around your circuit, would that help eliminate the possibility of the BMS getting shutdown or blowing up?

[molfpedal]

Originally Posted by MrBritGolfFan

Molfpedal the BMS on this battery pack i got says 130A on the side, however in my tests of using a clamp meter around one of the battery leads shows me i was able to pull 250+ amps and the BMS didnt shut down. My question around your circuit, would that help eliminate the possibility of the BMS getting shutdown or blowing up?

That BMS is rated for max 130A continuous discharge, which means that it will withstand short bursts above that. My BMS is rated 300a continuous and I'm still bypassing it on the discharge side.
When you first accelerate you will see 250+ for a few seconds and then it will drop into the 30A to 90A range. However, if you have long hills as I do you can see draws approaching 200A for more than 10 seconds, which can lead to BMS failure. My pack is 120ah, so I'm not too concerned with overworking the pack.
But, I do want my BMS to control the voltage, both high and low. With the relay setup and bypassing the BMS discharge side I don't have to worry about BMS failures due to too much current.
So, yes it would virtually eliminate that!

[MrBritGolfFan]

Originally Posted by molfpedal

That BMS is rated for max 130A continuous discharge, which means that it will withstand short bursts above that. My BMS is rated 300a continuous and I'm still bypassing it on the discharge side.
When you first accelerate you will see 250+ for a few seconds and then it will drop into the 30A to 90A range. However, if you have long hills as I do you can see draws approaching 200A for more than 10 seconds, which can lead to BMS failure. My pack is 120ah, so I'm not too concerned with overworking the pack.
But, I do want my BMS to control the voltage, both high and low. With the relay setup and bypassing the BMS discharge side I don't have to worry about BMS failures due to too much current.
So, yes it would virtually eliminate that!

Thanks Molfpedal!

What BMS do you have?

I live in Florida, so no hills here, so maybe i will be ok. Is there some way to make sure i dont blow the BMS up? perhaps it might go over load if i have too much load on the cart, like 4 adults etc?

[molfpedal]

Originally Posted by MrBritGolfFan

Thanks Molfpedal!

What BMS do you have?

I live in Florida, so no hills here, so maybe i will be ok. Is there some way to make sure i dont blow the BMS up? perhaps it might go over load if i have too much load on the cart, like 4 adults etc?

I have an ANT BMS, 10-24S version. It has built in Bluetooth, so I can monitor it and adjust settings if I need to.

The Setup that is in the first post eliminates those hard stops!

[MrBritGolfFan]

Originally Posted by molfpedal

I have an ANT BMS, 10-24S version. It has built in Bluetooth, so I can monitor it and adjust settings if I need to.

The Setup that is in the first post eliminates those hard stops!

something like this...:

https://www.ebay.com/itm/10S-24S-Sma...cAAOSwqQpducD2

Would i simply just be able to take my old BMS out and reuse the wiring harness do we reckon? or would i be in for a complete re-fit?

inside.jpg

[molfpedal]

I can’t answer that. You would need to compare the wiring diagrams to see if you can do that.
Be aware that if you are planning on running the discharge through the Bms then an HV or LV event
WILL lock your wheels on a RXV. So, if you’re running 20 and the voltage goes low it will be like turning off the key. Motor brake will engage. 5000rpm to 0 in milliseconds.


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[MrBritGolfFan]

Originally Posted by molfpedal

I can’t answer that. You would need to compare the wiring diagrams to see if you can do that.
Be aware that if you are planning on running the discharge through the Bms then an HV or LV event
WILL lock your wheels on a RXV. So, if you’re running 20 and the voltage goes low it will be like turning off the key. Motor brake will engage. 5000rpm to 0 in milliseconds.


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Thanks Molfpedal. So as long as i build this circuit and add it into my cart, that will eliminate that sort of issue right?

Would it be possible for controllers to be updated to have this type of design built in to them?

[molfpedal]

Originally Posted by MrBritGolfFan

Thanks Molfpedal. So as long as i build this circuit and add it into my cart, that will eliminate that sort of issue right?

Would it be possible for controllers to be updated to have this type of design built in to them?

It has for me. I had a loose connector on my charger interlock wire and it tripped the circuit. My cart coasted to a normal stop, found the bad connection and took off. I didn’t get the bullet connector all the way together when I put it together, sod it vibrated loose.
I will try to get some good pics of the circuit for you. What controller was is in your cart before the Navitas?