EZGO Lithium Conversion - Cutting out when regen braking

[tschmidty]

So I recently put in 3 30AH 48V Lithium batteries and i have had an intermittent problem where it will cut out and start free wheeling when going down my fairly steep driveway. Since the braking is electric it's more than a bit scary. Turning the key off does kick the brakes on, I have not tried to let it go to see if it will come back by itself.

My vague theory is that the lithium is letting the regenerative braking to go over a given amp limit (since lithium can take more amps).

Has any one seen this behaviour or have any suggestions? I did order the jakes front disc add on since it just makes sense to have real brakes in case of an electrical failure.

FWIW, I otherwise love the conversion, more speed uphill (since voltage doesn't drop) less weight, etc.

[Volt_Ampere]

The regen is probably tripping the BMS on the batteries. Charge current too high for what the BMS is set for. This is a bummer with this cart. I assume it's an RXV cart which relies heavily on Regen for braking.

[Dallas@Eco Battery]

We have seen this in testing. It is generally an over voltage issue when the battery is fresh off the charger, no time for the battery to "rest" and goes into regen shortly after. The excessive voltage trips the BMS and is especially dangerous on electric brake equipped carts. We have specifically addressed this in our BMS programming to all but eliminate the possibility of it happening.

[Tom47]

Earlier this year I contacted EB about where to set my regen amperage. My 72Ah is rated for 350 amps in short bursts and 100 amps continuous regen.

I have my Alltrax set at 50 regen amps and have never had an issue. The cart will slow nicely from top speed without touching the brakes. I don't have any hills to test it on however.

[tschmidty]

Thanks all and that totally makes sense that it would be the regen. Oddly I have seen a similar behaviour going uphill with the lead acid batteries when it was overloaded on a steep section.

It is generally an over voltage issue when the battery is fresh off the charger

The odd thing is I have a voltage meter on it and the voltage never goes over like 54.2v or so, which doesn't seem like it should kick it, but who knows.

I have my Alltrax set at 50 regen amps and have never had an issue.

Thanks @Tom47. So your Alltrax controller can be programmed for the amount of regen. I assume it limits how much it brakes. Can the stock controller be reprogrammed I wonder?

I have a different battery monitor I will set up, curious if it will allow me to see regen amps/voltage. And the more longer term fix will be to add actualy mechanical brakes which seem like a no brainer for the hills I am dealing with here!

[bronsonj]

Tom has the aftermarket Alltrax (as do I) and it is easily configurable. But you have the RXV cart right? The RXV has regen braking and a parking/emergency brake, but no normal brakes. Is there a Jake's front brake setup you can add to your RXV? I think I saw someone talking about that on this forum somewhere.

Your issue sounds like an overvoltage issue. Not much you can do to stop that except for possibly not fully charging the battery. I know that's not helpful because then you'll have less range.

Actually I just looked it up and there is a Jake's front brake kit for 2008 and up RXV carts. I personally like the idea of physical brakes since the electrical (regen) brakes drop out when the lithium battery disconnects.

[Tom47]

The front disk brake kits are around $500.

I admit that would be a nice way to go, but an Alltrax controller would cost about the same and give your lithium setup some good charging-while-driving which will extend your range if that is an issue.

I don't know how it would feel about locking up front disks going down a steep drive with light weight lithium packs. With the FLA pack, there would be more counterweight.

I really am not familiar with what might happen. I would get an Alltrax myself.

[Imapled]

On an RXV series in another resistor coil as well. Lithium on RXV is painful. I don't recommend doing it. OEM lithium on an RXV is CAN Bus integrated to the Curtis traction inverter. Its well done setup but, legacy units that were designed for lead acid batteries are a pain in the butt.

[ojo]

Originally Posted by Tom47

I really am not familiar with what might happen. I would get an Alltrax myself.

Alltrax doesn't have any AC controllers

[carter95138]

I have the opposite problem, my cart goes to full speed and I have to turn it off to get it to stop. See my post "2014 RXV out of control after full charge" in the "Electric EZGO" thread.