Golf Cart battery build

[tracker1]

I am working to replaced the lead acid batteries in my 48V Club Car with LiFePO4 for two purposes. One, to power the golf cart that I use for chores around my yard and for occasional short street trips for the grand kids. Second, as possible back-up storage for my house when the power goes off.

I ordered four Dr Prepare 12v 100Ah from Amazon for $819 that each have a complete BMS system and are rated at 1280Wh. I also ordered an Ocell 48v Lithium battery charger that has a rated output of 58.4 Volt /5 Amp. I plan to buy some solar panels to charge the batteries in the future and will need some help with that down the road.

First, do you think the four batteries hooked up in series will provide enough power and amps to run the cart?

My second question concerns charging. I'm concerned if using a 48v charger will be a problem. I read another post on this site concerning charging two LiFePO4 12v batteries, and the consensus was to initially use a 12v charger to balance each battery to get the same SOC, then hook them in parallel to further equalize both batteries, then after putting them in series use a 24v charger for normal maintenance charging. Would that same process work for the 4 LiFePO4 batteries I'm buying? I asked the manufacturer of the charger if they thought it would work. They said no, here is their answer: Our engineering team does not recommend you to operate in this way,There is a possibility that the MOS and TVS tubes of the battery module may be damaged, which could in turn damage the charger.

I have also asked the battery seller if they recommend using a single 48v charger but have not heard back. I'm also worried what would happen when using the 48v charger and one of the batteries hit full charge first, would that batteries BMS stop the charge for all the batteries, or would it just divert the charging voltage to the other 3 batteries and possibly send too much voltage?

 

[hwy17]

Those batteries are not endorsed for running in series.

We recommend using 48v batteries for 48v applications. Even when 12v batteries are rated for running in series, there's no way for them to stay balanced long term without adding an additional balancer.

Edit: I suppose they do have some models rated for series?

100Ah LiFePO4 Lithium Deep Cycle Battery with LED Screen - Connect In Series [10-year Warranty]

Dr. Prepare 12V 100Ah Lithium Iron Phosphate Battery is a safe energy source which offers a greater capacity than other lead acid batteries, with only 1/3 of the weight and size. The integrated BMS protects the battery from various abnormal conditions, so that the battery cells have 3000+ deep...

drprepare.com

 

[Partimewages]

It's likely that you won't make it out of your driveway. The BMSs are 100 amps and your motor will probably draw 3 times that on startup.
You will need to do extensive work to keep them balanced and charged. Probably more trouble than it's worth.

 

[Q-Dog]

You will probably need a 300 - 400 amp BMS to handle motor startup surge. It depends on your motor and controller.

 

[Solar Guppy]

Stock golf cart controllers are typically peak 175 amp maximum draw so if the BMS is rated for that ( or something in parallel / series combination ) should be OK.

 

[tracker1]

Wow, looks like I screwed up with these batteries. So 4 of these 100Ah batteries hooked in series still only gives me 100 amps, not 400 amps? I don't understand why they advertised them as working for golf carts? Also, just received word back from Dr Prepare on how to charge them:

We'd like to tell you what you have to do is that each battery needs to be full charged separately by 12V lithium charge before series. Only once that's done, 4 batteries will achieve the balance effect in series. In balance status, the capacity of the four batteries in series is at the same stage, and the full charge of 4 batteries will also be synchronized, which will not deliver too much voltage to the remaining three batteries.In series, if BMS of one of the batteries exerts a protective effect, the whole electrical circuit of 4 batteries will stop working, and will not cause damage to the remaining batteries.

 

[wme]

You tube is a starting point.
Some info on batteries
https://bigbattery.com/golf-carts/
Have fun

 

[Solar Guppy]

Wow, looks like I screwed up with these batteries. So 4 of these 100Ah batteries hooked in series still only gives me 100 amps, not 400 amps? I don't understand why they advertised them as working for golf carts? Also, just received word back from Dr Prepare on how to charge them:

We'd like to tell you what you have to do is that each battery needs to be full charged separately by 12V lithium charge before series. Only once that's done, 4 batteries will achieve the balance effect in series. In balance status, the capacity of the four batteries in series is at the same stage, and the full charge of 4 batteries will also be synchronized, which will not deliver too much voltage to the remaining three batteries.In series, if BMS of one of the batteries exerts a protective effect, the whole electrical circuit of 4 batteries will stop working, and will not cause damage to the remaining batteries.

Series: voltage add, parallel: amps add is the rule

As for 100 amps, it depends on the surge ratings of the battery. Golf cart batteries typically have much high current abilities that match or exceed what the maximum draw of the speed controller, most stock carts are 175 amps from dead stop, which is only that high for the first few mph ( 0 - 3 as an example ).

A good resource is https://www.buggiesgonewild.com/, I did extensive search on this for my highly modified cart.

 

[GuyG]

I ordered four Dr Prepare 12v 100Ah from Amazon

Is it too late to cancel order and get a 48-volt battery with a 200+ amp bms?

 

[tracker1]

Is it too late to cancel order and get a 48-volt battery with a 200+ amp bms?

Yes, too late, they are out for delivery. I did get a response from Dr Prepare and basically they said the same thing everyone on the forum has told me that you have to ensure the Ah of the batteries are sufficient to match the amps required for your cart. Dr Prepare does not sell higher Ah batteries. Did find other 200Ah 12v batteries or even 48v 100Ah batteries I could hook up in parallel, but it would cost twice as much, i.e. $1,600 to $2,000. Since I don't do much with the golf cart other that drive it around my yard I think I'll charge and hook up the Dr Prepare 12v 100Ah batteries when they arrive and see how they do. If it keeps tripping the BMS I'll return them.

 

[Solar Guppy]

To be clear, it is the BMS that must meet the amp rating, not the cells.

I have a pair of BigBattery 36V 60Ah battery's in parallel in my custom cart I built and have my controller set to limit at 220A. The Big battery specs 300A peak for 10S, 115A Continuous each

 

[tracker1]

To be clear, it is the BMS that must meet the amp rating, not the cells.

Thanks, I had assumed the BMS peak rating would be 100 amps. I just contacted Dr Prepare again to see what the peak and continuous amp ratings are for their battery.

 

[tracker1]

I have a pair of BigBattery 36V 60Ah battery's in parallel in my custom cart I built and have my controller set to limit at 220A. The Big battery specs 300A peak for 10S, 115A Continuous each

I heard back from Dr Prepare: We would like to tell you that for single 12V 100A battery, the continuous amp is 100A, 200A for 5s, 400±80A for 70ms.

I also found out my cart has a 225 amp controller. Seems your BigBattery has much better peak and continuous amp ratings. I looked at their website and see they have a 48v 61Ah similar to yours. It's rated at 150 amps continuous and 360 amps 6s peak. Do you think one of those would be an option for my cart?

 

[millsan1]

I will weigh in with my experience.

I have an Intimidator Classic EV. It is a 2,000 lb side by side.

It came with 8 6V Trojan batteries.

Those 8 batteries gave me about 10 mile range.

I replaced those batteries with drop in replacement, 48 volt Lithium batteries from big battery.com.

I put in 8 of those batteries. They were the Eagle, which looks like it has been replaced by Eagle 2 now.

Anyway, those are in parallel, and provide me more than 50 miles of range.

You will need to figure out your heaviest draw in amps, and make sure you buy enough batteries that their continuous will hold that max draw.

My batteries can do 60 AMPS continuous, each, so with 8, I am at 480. My machine can draw 400+, going uphill, in 4WD, etc.

 

[raurre]

Don't know if this will help but here's what I built. https://diysolarforum.com/threads/diy-230ah-eve-mobile-battery-aka-ezgo-golf-cart.40927/

 

[Solar Guppy]

I heard back from Dr Prepare: We would like to tell you that for single 12V 100A battery, the continuous amp is 100A, 200A for 5s, 400±80A for 70ms.

I also found out my cart has a 225 amp controller. Seems your BigBattery has much better peak and continuous amp ratings. I looked at their website and see they have a 48v 61Ah similar to yours. It's rated at 150 amps continuous and 360 amps 6s peak. Do you think one of those would be an option for my cart?

A single should work as that battery is designed for this application, someone else posted recently that has a single and works well.

Also the battery doesn't see the current the controller draws due to it PWM on the low side, similar to a buck controller which converts higher voltage to current.

I did two for range and extra margin, as I have a 400 amp controller, but with my motor was not certain what dead start amps would be.

 

[tracker1]

Also the battery doesn't see the current the controller draws due to it PWM on the low side, similar to a buck controller which converts higher voltage to current.

I don't understand anything in that statement, could you elaborate?

Also, as an update, I have installed the 4 Dr Prepare 100Ah batteries and got the cart running. So far it's not drawn more than 70 amps driving around my yard and on the street. However I've not done any big hills or had it loaded with 4 people. Here's a picture with the batteries temporarily installed.

 

[yourunclefats]

doh! wrong thread

 

[RodWorks]

I don't understand anything in that statement, could you elaborate?

Also, as an update, I have installed the 4 Dr Prepare 100Ah batteries and got the cart running. So far it's not drawn more than 70 amps driving around my yard and on the street. However I've not done any big hills or had it loaded with 4 people. Here's a picture with the batteries temporarily installed.

View attachment 185763

Any updates? Curious how the 4 battery setup has worked out? Also, did you still use the 48v charger?