72 volt Cushman

Beaner913

I have a 72 volt cushman with a Curtis 1236-6415 controller and a Mahle 3 phase AC motor in it. The label on the controller states the voltage is 48 - 80 and 350 amp. The motor states 45v 7.0 KW and DC 72 volts. My question is that is this controller programmed from EZGo to only run on 72 volts or is it able to work on any voltage from 48 to 80 volts? I have four of these carts and they get A LOT of use. The carts are 2017 with over 16500 miles and we just put in our second set of batteries. Wondering if they would be good lithium candidates for the simple fact of the mileage they get driven and the life of lithium over lead batteries. Any help would be great. Ive been reading all the posts on Lithium's and reading over at Battery U.

BGW

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kgsc

Controller can be set to work in that voltage range but the motor is for a 72 volt setup so you need to stay close to 72 for it to work properly.

bronsonj

You may get a better response on this if it were in the Lithium EZGO section.

I do not know that controller, but I would imagine if it says 48 to 80v it should operate on any V in that range. If you remove two of your 8V batteries and the cart still moves then you know it'll run on 56V too and 56V is probably lower than you want to drain your lithium pack anyway. I am assuming you were thinking of a 72V lithium pack?

An 18S pack at 4.15vpc is 74.7V. That's an easy number to get to using either 9 Nissan Leaf modules or a 12S and 6S Chevy Volt module.

Discharged to 3.25vpc gives you 58.5v. So if you want to discharge that far it'll still run. You will need a BMS that includes an LV cutoff because the controller will continue to drain the cells far below their intended minimum V.

This sounds like a really interesting project.

bronsonj

But a 20S pack may be interesting too. 83V fully charged though, so I don't know enough about that controller to say if it'll accept that or no. Fully discharged a 20s will be 65v so probably a better V range for your motor as KGSC mentioned.

kgsc

Controller would work at 56 after you change the settings in the controller. It will operate in that range but you would need to make all the internal software changes so it knows the range. Low/high voltage cut off and the like

Beaner913

If the controller would at 56 volts wouldn't the BMS take care of the LV shut off?

bronsonj

The BMS will handle the LV cutoff but many people here like the idea of redundant safety systems. So if you want the BMS to kill the power at 56v or 3.11vpc then set the controller to stop at 58v.

This way the controller will perform a controlled stop of the vehicle and if something odd happens the BMS will act as a backup. You really have very little capacity between 3.22vpc and 3.11vpc since it is after the lithium knee.

Also, we've heard of some controllers (like on the RXV) getting corrupted when power is cut off while the controller is under a load. So using it as a redundant system reduces the liklihood of that happening. IDK if your controller is vulnerable to getting corrupted though.

Beaner913

Thanks for the reply. The more I look around at the other lithium builds and the more I teach myself on lithium Im just going to keep it 72 volts. I should start a new thread over in lithium side. I still have a ton of questions but dont want to ask if I can find it here some where. Like you suggested with a 20s pack.

kgsc

LV cutoff I am talking about is the setting in the controller where it will not operate once it gets there. Lower the voltage higher the current. Keeps it from melting.