Golf Cart FLA to LFP Conversion, BMS Help Request

[Highhorse]

Thanks for looking:

I am a hobbyist with extensive high-amperage/high-voltage LiPo experience, so I understand the basics of the various lithium chemistries and the care/feeding thereof. Am in the process of selecting components for a 100ah 16S LFP conversion for my golf cart, the FLA batteries of which are on their last legs.

The sketchy data I’ve found thus far suggests that the cart currently draws somewhere upwards of 250A on acceleration (much less at steady speeds) and it is possible that future upgrades will push that substantially higher.

I can’t seem to find an LFP BMS with high and low temp cutoffs that also handles upwards of 400-500A. I have no qualms using a lower amperage BMS and wiring the load through a relay, but am unsure of the wiring. Has anyone here done this, and if so would you kindly share a diagram?

Alternatively, is anyone here familiar with a video or other reference which would enlighten me?

Many thanks,
Don

 

[FilterGuy]

Thanks for looking:

I am a hobbyist with extensive high-amperage/high-voltage LiPo experience, so I understand the basics of the various lithium chemistries and the care/feeding thereof. Am in the process of selecting components for a 100ah 16S LFP conversion for my golf cart, the FLA batteries of which are on their last legs.

The sketchy data I’ve found thus far suggests that the cart currently draws somewhere upwards of 250A on acceleration (much less at steady speeds) and it is possible that future upgrades will push that substantially higher.

I can’t seem to find an LFP BMS with high and low temp cutoffs that also handles upwards of 400-500A. I have no qualms using a lower amperage BMS and wiring the load through a relay, but am unsure of the wiring. Has anyone here done this, and if so would you kindly share a diagram?

Alternatively, is anyone here familiar with a video or other reference which would enlighten me?

Many thanks,
Don

Don,
What voltage does your cart operate at? At 250A, I am wondering if it is 12V.

@Will Prowse has some videos that shoes how he hooks up a BMS to directly control an inverter, but I am not aware of one to control a motor.

 

[Highhorse]

Sorry, I should have said up front that it’s a 48V cart. The onboard controller is rated for 250A, so my guess is that the stock surge amps with FLA are somewhere below that but I am anticipating higher surge amps with LFP because I don’t the the V will drop as much as the FLA while under load.

 

[FilterGuy]

I could be wrong, but my guess is the surge amps won't change a lot due to LFP. If anything, if the voltage does not sag the surge would be shorter (but just as high).

With large currents like that, I like putting the current control outside of the BMS. This means either relays/SSRs or using an external signal to control the load/charge components. I doubt there is a way to use an external signal to control the motor, so that leaves you with Relays or SSRs.

For this kind of set-up I like the Chargery or the Electrodaucus BMS, but I don't think the Electrodacus will do 16S so that leaves Chargery. Chargery also recently released a set of High Powered SSRs that might work reasonably well for you.

 

[Highhorse]

Thanks for the suggestions. I don’t see a low temp charge protection for the Chargery units. Suggestions?

 

[FilterGuy]

Thanks for the suggestions. I don’t see a low temp charge protection for the Chargery units. Suggestions?

The Chargeries did not have low temp protection for a while, but it was been added to the firmware several months ago. Any new chargery ordered will have it.

NOTE: A new version of the chargery was just released and as far as I know, no one on the forum has received and tested it.
https://diysolarforum.com/threads/chargery-bms-news-update-nov-25-2020-ver-4-02-firmware.15122/

 

[Delmar]

I measured my 48V Yamaha AC motor golf cart at acceleration around 120A. Then again it was done with a handheld clamp meter while driving, without a seat, so was difficult to multitask while attempting not to fall off. Steady speed was around 25A.

 

[FilterGuy]

....it was done with a handheld clamp meter while driving, without a seat, so was difficult to multitask while attempting not to fall off.

that paints a pretty funny picture!! ? I can just hear your wife yelling in the background about how she isn't going to take you to the emergency room!

 

[Highhorse]

Thanks guys!

 

[AussieInSeattle]

Thanks guys!

As mentioned above you need to go the relay route. Im about to start my build using the diagram and components from the link below but with 120Ah higee cells instead of nissaneaf cells. The thread is 41 pages long but should answer all your questions. The guy who created it (sergio) answers regularly and thoroughly. Tons of great content on BGW but most lithium conversions are used leaf cell based.

Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS Lithium Club Car

www.buggiesgonewild.com

 

[mattadata]

Thanks guys!

Hi. Any updates on your Golf Cart conversion? I am looking into the same thing.
As far as current draw when accelerating in a 48V cart, I made a video which shows the stats a while back.

Peaked about 240 Amps. This was an aftermarket controller, so stock would be a little less.

 

[AussieInSeattle]

Hi. Any updates on your Golf Cart conversion? I am looking into the same thing.
As far as current draw when accelerating in a 48V cart, I made a video which shows the stats a while back.

Peaked about 240 Amps. This was an aftermarket controller, so stock would be a little less.

What controller are you using and what format did you export the data in to get it into racerender?

 

[mattadata]

What controller are you using and what format did you export the data in to get it into racerender?

The controller is an Alltrax XCT500. It can log data to a laptop via USB in CSV format.

 

[Heyjimmy911]

How many amps (surge) do you folks think it takes to start a 48V golf cart? I blew up a 300 Amp DC Contactor yesterday on my maiden test voyage. Actually moved about 24 inches at the lightest throttle I could then...,. bang! No fire, but plenty of smoke.

It's a chargery system. I've read that people have had problems with Chargery but I'm really hoping that the bugs are worked out, and I simply underestimated the start up surge. Do you folks think the 600 amp DCC would be enough to handle the surge or might a KILOVAC be in order. My other 48v system is REC and Victron but all in it was pretty expensive.

I have it set up in a separate port configuration. I imagine if I go the kilovac route, I would need to reconfigure to common port.

Thanks.

 

[Ai4px]

Just to contribute some info... I have a stock Club Cart Precedent. Just replaced the batteries with 100AH LFP and a daly 250A BMS. Seems to be overkill. I had to try really hard to see 100 amps on the bluetooth port. Granted it doesn't update but every couple of seconds but most of the time it was pulling 14-28 amps on the road in front of the house (up hill / down hill).

Also, if the Daly goes to sleep you simply short pins 1 and 3 on the light board plug. Those pins will be 0v and 48v if you check them with a volt meter. Just briefly touch them together to wake Mr Daly up. The plug you need is an 8 pin JST PH female.