Lithium Batteries - General Question

Captr

New Member
The 8 volt wet cell batteries are shot. Therefore I am not able to do a load test. I agree in the margin of safety when electronics are concerned. A 200amp bms detuned would be better than 100A
max out.
 

TomBuggy

Member
Definitely one single 48v battery as it will be managed by a single BMS that will keep all cells balanced. 4 x 12v batteries is asking for trouble. You have 4 BMS’s all, doing their own thing and your batteries will (not may) become unbalanced. This will reduce your run time more and more over time. When this occurs, The fix is to top balance by fully recharging each battery individually with a 12v charger. But they will then drift out of balance again over time.

More important than capacity is maximum continuous discharge amps, maximum peak discharge amps and the time that the maximum peak amps can be drawn for. Unlike FLA batteries, lithium batteries have a BMS that will limit current to protect the cells. It will disconnect the battery and shut the cart down if the parameters are exceeded. These maximum figures will be dependent upon your carts configuration, but I personally wouldn’t go for anything under 150A continuous and 250A peak for 20 seconds for an unmodified cart.

Choose the correct battery for your cart and you’ll never regret the added initial cost. Performance is so much better, not to mention virtually no maintenance and long term costs will be less as lithium’s should last you at least 10 years.

Cheers
Pat.

Thanks for all your informative posts on this thread.

TombuggyPicnic.jpg

That's my buggy and the kind of thing I sometimes do to it.

It was a Club Car 6 seater from the factory. The previous owner put the aluminum cage on it. I put a hard top on that and put the Carryall bed on it, along with a (heavy) hitch extension. It has 8 x 6 volt batteries.

It weighs close to 1,700 lbs.

It has a motor and controller from Hi Performance Electric Vehicle Systems, installed by the previous owner. The controller is a Curtis.

It goes almost 35 mph, way too fast for my needs. I'm going to have a local shop try to hook up their computer and tune the speed down on that controller.

While they're doing that, I want to switch to lithium power, shedding as much weight as possible. I don't have much need for range, as it travels less than a mile on a typical day, maybe 3-5 miles on a heavy use day.

I'm going to continue to tow inappropriately heavy things with it, sometimes up boat ramps.

The shop that will work on it doesn't sell lithium batteries, so I want to buy a 48 volt lithium battery pack and bring it to them to make the swap when they tune the controller down.

My question for you and any others with an opinion: which one do I buy?
 

Pat911

Cartaholic
Nice cart.

Have you considered that by shedding weight you will likely have problems towing inappropriately heavy things up slippery wet boat ramps.

I would still go lithium but would consider adding ballast over the rear wheels or at least ensure that the lithium pack is installed under the rear seat, not the front.
 

TomBuggy

Member
Nice cart.

Have you considered that by shedding weight you will likely have problems towing inappropriately heavy things up slippery wet boat ramps.

I would still go lithium but would consider adding ballast over the rear wheels or at least ensure that the lithium pack is installed under the rear seat, not the front.
Yes, that has been very much on my mind. Our boat ramp is the slickest one in the county. Dogs fall down trying to walk on it. I've broken a hip on it. But my old cart used to do it all the time and my new one is not having a traction problem. It's having a torque problem.

It will tow my smaller aluminum skiff right up the ramp, no problem. If I want to get the bigger one up the ramp, that's a problem.

Before I added even more weight, my wife could make the difference by getting out and pushing. She's a normal, middle aged woman, no body builder. Now I need two pushers.

I figure if I can knock a few hundred pounds off the total weight, that might be about the amount my wife could push up a ramp.

The poor thing is still going to weigh 1,300 or 1,400 lbs, so will still be pretty firmly attached to the ground.

It currently has 6 batteries under the rear seat and two more under the front seat. My plan was to put a lithium pack under the rear seat because that's where batteries are supposed to go in this model and that will keep cable length shortest.

But I'm still wondering which lithium battery pack?
 

Pat911

Cartaholic
Good to see you have considered it in great detail. Can’t help you with drop-in packs as I have no experience with any of them, I build my own. I will advise that considering the weight of your cart and the inappropriately heavy :) things you’re towing, you’re going to need a pack that can sustain a substantial amount of peak and continuous current.
 

TomBuggy

Member
My dad was an electrical engineer but he died some years back. I'm just a guy who likes to play with things and break them and then winds up having to fix them. Not really sure what is meant by "substantial" in this context.

It wasn't easy to get a picture of the sticker on the motor because it's under the three big wires that I did not want to disturb, but I managed to get this one:

TomBugMotor.jpg


The Curtis controller was a bit easier to photograph:

CurtisController.jpg


650 sounds like a lot of amps. And I guess 6 sounds like a lot of HP too.
 

Cdenjo72

New Member
I just bought the Dakota lithium batteries 3 12 volt with a 36volt charger with BMS. They sold them as golf cart batteries and have an 11 year warranty. Seems to work fine so far but have not had that long of running time yet. Here is list of properties for the batteries.
lithium-battery-bms.jpg
 

Pat911

Cartaholic
Tom,

You have a 6HP (4.5kW) AC setup there, that will give you plenty of torque. Your lack of pulling power up the boat ramp is most likely due to voltage sag from the Lead Acid batteries. Lithium will help mitigate this as voltage sag is minimal. As you correctly state, weight reduction will help but I believe it's the voltage drop that's stopping you.

To answer your original question, "Which one do I buy?" buy the one that has the highest peak and continuous current ratings. 100A is not going to cut it here. I'd be looking for something that has at least 150A continuous and 300A-450A peak for at least 30 seconds, or however long it will take to pull your boat up the boat ramp. Do you have a DC clamp meter that you can use to measure the current?

The problem with Lithium is that on overcurrent, the pack will shut down and your cart will stop, you won't be able to get your wife to help push as you do now, although helping to push may stop an overcurrent situation arising in the first place. Also ensure that whatever pack you get auto resets on a fault condition. Some require you to plug into a charger to reset the BMS, not good when you're on a boat ramp with a small yacht behind you.

Lastly, stay away from the 12v batteries as described above. A 12v series setup will always be a compromise for many reasons that I've gone into numerous times before. A single BMS managing all cells is much better than 4 BMS's (in a 48v system) doing their own thing. You will have balance problems with 12v batteries. Get a single 48v pack that is sized appropriately for your application and you will never look back. Or build your own :)

Cheers
Pat.
 

TomBuggy

Member
Thanks for the additional tips, Pat! In addition to the balancing problem you described, I would think multiple batteries wired together would be less efficient than a single pack just because of the "wired together" part. Wires and their connections are resistance.

Didn't know about the auto reset thing, that's good info. It's about a 15 minute walk from the boat ramp back to a charger, and then what? I get my generator to places like the boat ramp using... the golf cart!
 

TomBuggy

Member
Dakota makes a 48 volt 96 Ah golf cart pack and their web page about it says this:

How Much Power do I need for my golf cart?
This single 48V battery will replace a set of 6V, 8V, or 12V batteries in a 48V cart. This battery is suitable for most carts with a max speed of less than 27 mph and a motor controller rated under 240 Amps. If your motor controller is rated 240 Amps or higher, you may need two of these 48V batteries in parallel (some dune buggies, off-road carts, ATVs, and high speed carts fall into this category).

So how does that math work? Do they add up directly, so two such packs would handle 480 and three would handle 720?

If so, I'd need three of them to exceed the 650 amps shown on the sticker on my controller. That's $8,100. My wife is going to make me sell a boat or two when she finds out.
 

Pat911

Cartaholic
Your math is correct, but you don’t need to exceed the controller limit. The statement you quoted is BS. You could replace your controller with a 1000A controller but it doesn’t mean it will draw any more current than your 650A one, all else being equal. In fact I don’t believe your contr is drawing anything near 650A with the motor you have. If you can measure the current you’ll have the info you need.
 

TomBuggy

Member
I don't have a clamp-on ammeter and I assume you mean measuring the current at full power. There are only a couple of stretches on my property that are smooth enough to go at full power and even in those places it's pretty terrifying.

So you think the 650 is the max (continuous or peak) that the controller can handle, but probably not what my motor/cart setup is asking from it? Makes sense. You'd want the controller to be able to easily handle projected current.

I'm hoping to have the local shop tune this controller down to the speeds shown in the manual I got with the cart. That says it should go 25 mph, 12 mph in "golf" mode. It currently goes about 35 and 25 in golf mode. 25 is more than enough for me. If I have to accelerate to that speed slowly, that's OK too.

I'd guess the most I will ask of it is dragging a boat up the ramp at low tide, probably max of ten seconds at full power.

Now I'm wondering what might happen if I buy one of those 48 volt packs and run it to see how it does, then add another if necessary?
 

Diode

Cartaholic - V.I.P. Sponsor
Max current is obtained when just taking off from a dead stop at Full Throttle when cruising your current usage drops dramatically that's why the voltage comes back up at cruising speed
 

Pat911

Cartaholic
In addition to what Diode said, current will also increase with weight, especially when accelerating. From the insight you’ve given in regards to how you use your cart, I believe your max current will be achieved when accelerating up the boat ramp from standstill with your boat behind you. As Diode implied, you can reduce this current by feathering the throttle at takeoff.

And yes, 650A is the maximum the controller can handle, not what the motor will be drawing.
 

englishwl

New Member
I would like to upgrade my 36V TXT to Lithium...What I am getting from this thread is buy the biggest single 36v battery and do not connect more in series or parallel. The biggest one I see out there is Bigbattery.com 36v 120Ah are there other options?
 

TomBuggy

Member
From the insight you’ve given in regards to how you use your cart, I believe your max current will be achieved when accelerating up the boat ramp from standstill with your boat behind you. As Diode implied, you can reduce this current by feathering the throttle at takeoff.
I can feather a bit and ease off the brake instead of letting it pop free, but without a whole lot of throttle pretty fast the whole business starts going backward.
 

Pat911

Cartaholic
@englishwl,
Definitely not series. If you must then parallel is an option, but it’s always best to have a single, correctly sized battery.

@TomBuggy,
I also own and launch a 2400kg boat (with a Range Rover though, not with a cart) so I know what you’re talking about in regards to going backward. Without a battery that can sustain high peak currents then I’m afraid you’ll be stranded at the ramp, unable to pull your boat out of the water. I cannot give you a definitive answer as to what that peak current will be as there are too many variables (controller settings, cart weight, boat/trailer weight, drag from the water, inclination of the ramp etc….) If you cannot get a DC clamp meter then maybe purchase a SOC meter with a shunt. Many of those will give you a current reading and it will come in very useful when you upgrade to Lithium. The one I recommend is this one.

Renogy 500A SOC Meter
 

TomBuggy

Member
there are too many variables (controller settings, cart weight, boat/trailer weight, drag from the water, inclination of the ramp etc….)
Yeah, contemplating all of those is what got me thinking that the only real test I can do is a live one with the boat on the ramp. And some other vehicle on standby, in case the results are bad.

I contacted Dakota and they said that two of their 48 v 96 Ah packs might do it, but might not. They're coming out with one that should do it in March. Waiting is an option, at least for now. My batteries are old but working.
 

Pat911

Cartaholic
If you have an AC system you don't need a DC clamp-on ammeter
The draw from the battery pack will be DC, it’s the controllers task to convert from DC that the battery provides to AC that the motor requires. The DC clamp meter would be placed on one of the battery leads.

@TomBuggy, do you have the full specs for the Dakota battery?

Cheers
Pat.
 
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