1993 Marathon- new owner, new member

[bronsonj]

In a basic sense, Amps = torque.

So it would be easy to say 250 amp controller is 20% more torque than a 200 amp controller, but that isn't the whole story.

I've read on here from many people who are actual experts that different brands of controllers are better/worse than others and some stock controllers can be reprogrammed if you have the tools/knowledge to outperform some aftermarket ones and whatnot. So no, there isn't an accurate formula that I know of or that I could imagine would work.

Also, if you check out http://www.cartsunlimited.net/alltrax-sr-series--.html

The 400 amp Alltrax is really close in price to the 300 amp.

The 300 amp is good for stock use whereas the 400 can be used for stock or can support an aftermarket motor if you go that route in the future and it produces more torque.

Since your only complaint is torque I'd skip the 300 and go for the 400.

On my conversion, I did use the 300 amp, but I also dropped 400 pounds of lead acid out of the cart and upped the voltage to 58V. If you aren't dropping several hundred pounds or increasing V, then I'd look at the 400 or possibly even the 500 amp controller.

Worst thing you can do is buy the 300 and install it, realize it doesn't get you the torque you need then go back and buy the 400 or 500.

[Yeoman]

I was actually looking at the 400 if I were to make a change, but referenced 300 for conversation purposes about torque pickup.
So you went lithium? If you did it over again, would you go lithium or just upsize the controller?
What is the impact on battery depletion (time between charges) and/or battery life from stepping up a controller?

[bronsonj]

I went lithium and I would go lithium again.

Lithium does require you to "knowledge up" as there are things you need to do and things you need to avoid so as to avoid risks. Lithium can be done very reasonably, but you need to figure out a lot more and read a lot more to do so without catastrophic failure.

The first time I replaced the controller was after I went Lithium, so I can't give you specifics on a controller upgrade vs run time with lead acids.

What I did may not work for you.... But here's what I did for better or worse.

I charged my lead acid batteries and I measured the voltage at the batteries during charge. On my 48v pack it topped out around 61V if I remember correctly. I made the assumption that my stock controller should be able to handle running on a voltage somewhat near that level, so I put together my lithium pack with a designed max of 58.8v. In reality I don't charge that high so it adds years to the life of my pack. My stock 48v controller worked fine on 57v for the several weeks before I upgraded to the Alltrax controller. I do not know if my stock 48v controller would have lasted another week, year or lifetime at 57v but I do know it lasted several weeks with voltage in the high 50's and was a blast to drive. You have to be careful you do not over-deplete your lithium batteries as that will destroy them.

If you go with higher voltage, you will see more speed and have a livelier cart. If you go with more amp hours (ah) you will have more run time.

If you convert to lithium and increase the voltage, you will need a new charger and you will need to program your Alltrax to not go below a voltage that is listed as safe for your battery. The BMS they sell with those 48v/50.4v lithium modules on ebay don't have a low voltage cutoff, so you will need to be extra cautious with that or buy and install your own BMS. You have a series cart so I think you'd also need a new F-N-R switch and solenoid. The loss of 400 pounds from your cart will help reduce the load on it to help offset how you'll be using it.

If you do not increase your voltage then I would suggest more than 47 amp hours for the pack. I have a buddy with a 36v cart, we built an 11 cell (46.2v max) but he only charges to 44V. 47ah was barely OK. He tripled his pack to 141ah at 44V. He uses his cart all the time, it's higher voltage means it's faster than it was on 36V, weighs less so it accelerates better and he charges one a month or so. Not increasing the V means your stock controller, F-N-R and Solenoid may be fine. Note, increasing V later is more difficult than increasing Ah later. Your stock charger may or may not be OK, depending on your pack and what your charger does.

On a side note, we initially started with a 12 cell pack, 50.4v max, since we didn't know how far his stock 36v charger would push the batteries. It stopped at 44V, well below the safe max and he drove it that way with HORRIBLE range since each cell was only charged to 3.66V, pretty close to the lithium "knee". We removed one cell making his an 11 cell pack still charged to 44V and his range was MUCH better because each cell was now charged to 4.0v. He wanted more range so he upped the ah later.

[Yeoman]

That's some great detail and a lot to digest. Thank you. I will likely live with the current setup for a year or so, to see how I use it, whether I need or want more torque enough to spend the time & $ and how the current batteries are holding up. The logical time to make changes, particularly to lithium, would be close to battery replacement.
Did you have any thoughts on impact to battery life/cycles from a boost to a 400 amp controller?

[bronsonj]

I would imagine that a 400 amp controller would have to reduce run time, if it is enough to notice? I would imagine/guess probably not.

The best thing you can do to get the best cycle times is to verify your cart and batteries you currently have are in good order.

Her's a list, starting with the easiest stuff first.

Firstly, make sure your batteries are watered with distilled water to the proper height and the terminals are sealed with the red spray and no corrosion. Batteries will lose water. So you may go 3 months without having to add any water or you may need to add a gallon of water in 1 month. When I had lead acid batts I kept 2 gallons of distilled in the corner of the garage.

Don't go below 50%. On a 36v cart 50% is basically 36.3V and a 48V cart it's basically 48.4V. It shifts with brand and temperature some. This is not the V while driving... It is the V after been sitting 12 or more hours with no load or charge. But most of the rebound occurs in the first hour so if your cart has sat for an hour, check the V.

If you have a float charger that's best, but when the cart is not in use it should be on the charger. You don't need to go crazy, but when done for the night it should be plugged in even if you still have 80% remaining in the batts.

Make sure your tires are well inflated. They should be capable of handling 20PSI or more. I started mine at 18PSI when I had lead acid but lowered to 16PSI for better ride. More pressure means more GO time.

Check for dragging brakes. Lift both rear tires of the ground and see if you can spin them by hand easily. The lift *might* have pulled the brake cable so you may be having drag or the brakes may just be out of adjustment.

Check your alignment. Depending on who you talk to and the method you use you want anywhere from 1/4 to 1/8th inch toe in. There's a cart in my hood that has the toe in very much off. So bad he was nearly plowing the dirt as he drove. I did tell him, but don't know if he fixed it.

[bronsonj]

Originally Posted by Yeoman

I will likely live with the current setup for a year or so, to see how I use it

That is a very smart move... Figure out what you like and don't like before you spend $$$. Many people (myself included) jump in and buy before truly understanding what they want/need.

[Yeoman]

Bronsonj- thanks for the "easy stuff" pointers. I checked tire pressure yesterday and they were way low, maybe 5lbs. Interestingly not noticeable looking at them. Inflated to 20#'s. They're almost new condition.
Unfortunately, my charger is timer style. So far, I've charged when around 70%. Takes 2-3 hrs to get to 38v from around 36.5. Water levels are good and I plan to get one of the "easy filler" jugs to encourage proper maintenance of water level. Floating charger is likely in my future.
I'll check the brakes and toe in. Easy enough to do.

Thanks again for the great advice.

[cgtech]

As far as "will going to a 400a controller reduce my range" topic goes, I look at it like this- if everything else stayed the same (pack voltage, daily distance usage characteristics, vehicle weight, tire size, ect). You will love, and use the new-found torque to "zip away" from your house with a grin on your face for a while, then eventually drive it more similarly to how you used to, so overall it won't make a huge difference (unless stock was totally inadequate for your use, then this is the new normal). If you got a huge speed increase by replacing the stock controller and you got a huge increase in top speed (for SepEx cart owners), and you now are "enjoying that new top speed" that would decrease your range.

[Yeoman]

Cgtech- I gather what you're saying is that the only added depletion would be when giving the cart juice beyond what the current controller can provide: as in climbing a hill at a faster pace or towing at a faster speed than with the current setup. Both controllers when providing the same energy needed would cause the same battery depletion. The larger 400 amp would just be there when needed. Basically what you mean in different words?

[cgtech]

Yes