Battery bms shutoff
 

2019 tempo with Navitas ac conversion/72v controller and 5kw motor, 72v solenoid, (6) 72v allied batteries, 6 to 1 gears, 12" rims, 18" steel belted-radial-directional tires, Jakes 3" spindle lift kit.

So far I have done 6 test runs with no problems. Yesterday I modified my Navitas settings. I calibrated my throttle and changed the throttle ramp rate to 200 *max and the maximum acceleration to 9000 *max. Took it for a test drive and it failed. The battery bms's all shut down. Dead in the water. looked everywhere for how to reset the bms, no luck. By chance, I thought I would plug the charger in for a few seconds. Voila! Batteries are back to normal. I reset the settings back to the factory for now. By the way, the acceleration was crazy fast for as long as it lasted!

Re: Battery bms shutoff
 

Many lithium batteries require a charger connection after a shut down event to reset. Can be quite inconvenient if it happens away from a power outlet. I much prefer self resetting BMS’s.

You can make a “jump starter” with a small 12v power source and a current limited dc-dc boost converter. Could even use an 18v power tool battery if you have one available. DC-DC boost converters are available cheaply from Amazon or AliExpress.

Cheers
Pat.

Re: Battery bms shutoff
 

That is an awesome idea. All I need is a rechargeable 12v lithium compact slimline battery that will fit in the battery compartment
and a booster, correct? Thanks!

Re: Battery bms shutoff
 

Do you connect directly to battery terminals from the booster?

Re: Battery bms shutoff
 

Yes, that’s all you need. It should connect to the same points as your existing charger as the booster is essentially a charger.

Get a booster with adjustable voltage and current. Set the voltage to about 58v and the current to under 1A. Remember, when allowing for losses, 1A at 58v will be about a 6A draw from the 12v battery. Use the booster just to get going again, do not leave it permanently connected as the 12v battery will drain very quickly.

Lastly, disconnect, or have a switch between the booster and the 12v source or the booster will drain the 12v battery over time even when not connected to the cart.

Cheers
Pat.

Re: Battery bms shutoff
 

I'm just an amateur when it comes to this, but it seems to me that if your BMS shut down it would be for (maybe?) a low voltage reason?

Drawing that many amps that fastly\quickly perhaps dropped an individual cell voltage below the minimum?

If that's the reason\culprit I'd be somewhat concerned that this could be an issue for the short part of a long term?

Re: Battery bms shutoff
 

Hi Dave,

From what I read he turned up the acceleration on his Navitas controller, hence increased the current draw. Too many amps is what I suspect tripped the BMS. The internal resistance of Lithium cells is very low, so pulling high amps won't drop the cell voltage too much, unless the cell was very low to begin with. He's now turned it back down.

My solution will not get you going again if the battery trips on low cell voltage (it might, but not for long), just if you trip out on high current due to a long incline, carrying extra weight, difficult terrain or something similar. It's a work around for the BMS's that require a charger connection to bring them back to life after an over-current event. Reset the BMS and change your driving style, better than getting a tow.

Cheers
Pat.

Re: Battery bms shutoff
 

Thanks pat!

Re: Battery bms shutoff
 

Pat,

Can you post a link for a 12v to 60v adjustable dc boost converter waterproof that you would recommend? I am struggling to find one that is waterproof and boosts more than 48v. Would a 48v work? Thanks!

Re: Battery bms shutoff
 

48v will not work, it must be higher than the battery voltage to work. You most likely won’t find a waterproof one, just purchase a standard one and build it into a waterproof enclosure. This one will work.

https://www.amazon.com/Converter-Vol...s%2C339&sr=8-6

You can also throw 3 or 4 high current 18650 lithium cells in there with protection board and usb charger and make it self contained.

Cheers
Pat.