E-Kart Build

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ElectricTraveler   1 µW

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E-Kart Build

Post by ElectricTraveler » Apr 19 2018 5:07pm

I have been spending a great deal of time reading and trying learn and tailor for my build. I believe that the direction i am going is a good one, but before I spend any more time and money some opinions are a good thing

Hardware currently in hand:
Motoenergy ME-0708 48V, 100 amps continuous, 300 amps for 1 minute
Alltrax SR48300 300amp max

Hardware I propose to purchase.
Qty 7 Nissan Leaf batteries 16S
BMS (https://www.ebay.com/itm/60V-67-2V-16S- ... 1763000252)
Charger http://www.thunderstruck-ev.com/cycle-s ... 4-48v.html

I have been contemplating Leaf and Chevy Volt batteries as they are plentiful and reasonably cheap. This is where I am a bit confused with the nominal vs max vs. min and how the Alltrax paired with the ME-0708 will work. It is not my intention of over-volting the motor or for that matter under-volting with the early generation Chevy Volt battery. The newer generation Chevy Volt battery are ~56V nominal so that seems high. Guidance here would be of great interest.

I have been told that the BMS is not completely necessary, provided they are balanced occasionally and the voltages are monitored while charging and discharging. There are risks with this scenario. The BMS I linked can only handle 150amp continuous although the motor can take more. I figured limiting this max current in the Alltrax controller would work. A BMS that can handle the higher current may be too costly at this moment.

The charger I linked seemed to be really flexible and possible the answer to safe charging with out a BMS.

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amberwolf   100 GW

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Re: E-Kart Build

Post by amberwolf » Apr 20 2018 2:35am

ElectricTraveler wrote:
Apr 19 2018 5:07pm

Qty 7 Nissan Leaf batteries 16S
I dont recall for sure, but the cells are probably 3.7v nominal, 4.2v full, so 16s gives a nominal pack voltage of 59.2v, and a full charge of 67.2v.

I think that is going to require the 72v version of the Satiator to charge it (if you go the CS route).


Depending on what cell version, they could be about 33Ah per 16s string, so 7 strings x 33Ah = 231Ah.

231Ah x 59.2v nominal gives about 13675wh, which is a decent sized pack.
Thats going to take quite a while to charge up, as the Satiator is only a 360watt unit. Its a really *nice* 300w unit, but it does have its limits.

If you run the pack down near empty and need to charge it back up, then 13675wh / 360w = about 38 hours.

This is where I am a bit confused with the nominal vs max vs. min and how the Alltrax paired with the ME-0708 will work. It is not my intention of over-volting the motor or for that matter under-volting with the early generation Chevy Volt battery.

All batteries have a voltage range, so all motors and controlelrs are designed to work at least with that range, meaning a 48v controller or motor is likely to be meant to work with something like 40v up to 60v. Motors themselves dont actually even have a voltage except that they spin at a certain speed at a certain voltage (and brushed motors will arc more at higher voltages, heating more and wearing brushes faster). So when a voltage is given for a motor it really means it was meant to run at a certain RPM range at that voltage. Its a bit more complicated than that, but thats the basics.

I dont knwo what hte voltage limits (HVC and LVC) of that Alltrax is, but if its not designed to go up to 67v+ you will need to use a different controller or youll need to use a lower voltage battery.

I have been told that the BMS is not completely necessary, provided they are balanced occasionally and the voltages are monitored while charging and discharging. There are risks with this scenario. The BMS I linked can only handle 150amp continuous although the motor can take more. I figured limiting this max current in the Alltrax controller would work. A BMS that can handle the higher current may be too costly at this moment.
Should be easy enough to have the BMS drive the coil of the system contactor rather than direclty passing current. Then the BMS doesnt have to handle more than however much current it takes to turn the contactor on. When the BMS hits LVC, itll shut off the contactor and cut power to the system. Exactly how youll wire this, I dont know, as it depends on your BMS design and how you want to wire up the rest of the system, what kind of contactor, etc.

Thats assuming you want to use a contactor for disengaging/engaging the power to the pack, but itll be a good safety feature and you can also use it as part of a precharge circuit to keep sparking during pack connection down (either during turn-on or physical connection).
The charger I linked seemed to be really flexible and possible the answer to safe charging with out a BMS.

ITs about as safe as any other well-built well-designed charger, as far as charging without a BMS goes. As long as the cells are good quality and well matched, and not run near their performance limits, theyll probably stay in balance pretty well. If you run them really hard and down to low charge levels, thats where they may not stay balanced.

Since they are used cells, which you cant know how or how long they have been used or under what conditions (other than the limitations normally imposed by the car they came from), its safer to assume they dont have quite the full capacity or quite the highest performance they started with, although they should still be well-matched if they all come from teh same car.

ElectricTraveler   1 µW

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Re: E-Kart Build

Post by ElectricTraveler » Apr 20 2018 8:45pm

Thanks for the clarification on the motor voltage and RPM. Everything is more complex that it seems, appreciate the simple explanation. The Alltrax SR48300 has a max voltage of 62v, so I will definitely rethink the battery situation.

Good catch on the Satiator only a 360watt. I was attracted to the configuration of the unit and not the performance. More than 24hrs to charge seems excessive amount of time between the fun, in my mind. I really like the idea of a BMS driving the system contactor, certainly a good way to protect the batteries and not require a monster BMS handling the current. I'll investigate this BMS and see if a scenario like this would work.

Looks like I need to investigate the pack charger situation a bit further.

I assume that a completely separate charger would be necessary to charge/balance the individual modules/cells? I seen folks use RC programmable chargers for this purpose.

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amberwolf   100 GW

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Re: E-Kart Build

Post by amberwolf » Apr 21 2018 2:39am

RC chargers (and common BMS units) have very tiny balancing capabilities, so with a large pack like yours, if it did get out of balance, it could take days to weeks to rebalance it.

The best way to avoid that is to use the pack well within its performance limits, so it doesnt get out of balance in the first place. ;) Some info below about that.


I dont know off the top of my head what the Leaf cells you have can do, so well illustrate using some imaginary numbers:

Lets say your pack is 250Ah, and is capable of 5C maximum sustained. That means it could handle up to 1250A, but if you use only half that, 625A, as the max current even for bursts, then it wont push the cells very hard at all, and theyre likely to stay balanced. (assuming they are also charged at much less than their charge rate limit)

However, if its only capable of 2C, thats only 500A, and using only half that, 250A, probably wouldnt be much fun. ;)


Regarding a capable charger that wouldnt cost a lot, the Meanwell LED PSUs like their HLG and similar series are usable as chargers, and as long as their voltages are correctly and equally set, can be paralleled for higher charging currents. A number of us here on ES use them.

I use my Satiator for slower charges, and my lighting pack, but for fast charges I use a pair of HLG-600H-54A units in parallel, adjusted to just under 58v, for my 14s2p 40Ah EIG NMC pack, to get a 24A rate (which is actually higher than the 0.5c rate the cells are speced for, but I dont do it often, just on a rare occasion I need a really fast charge--usually I charge at 12A with just the one HLG bolted to teh bottom of the SB Cruiser trike).

The pack itself I use at a burst max of around 2.5c, though its rated for 5c continuous and 10c burst. Sustained max is much less, around 0.5c or less. I dont normally use more than a few percent of its capacity, either. And it stays balanced without BMS or other manual interference. (as did its predecessor with the same kind of cells, on a previous lighter cargo bike that had lesser power requirements).


Most of the BMS units are made to fix small imbalances in small packs, so they have less than 100mA of balancing current capability. If you have a pack thats more than 200Ah, and it gets really badly unbalanced, so say 20Ah or more of imbalance between highest and lowest cells, it would take a 100mA bleeder BMS at least 100 hours to correct that much imbalance, as the BMS will shut off input current as cells reach HVC, then bleed those down, then let charge current resume until the high cells reach HVC again, etc., repeating until all the cells reach the same voltage (which generally means theyll be the same state of charge, and thus contain the same Ah again).

If the cells are well-matched its unlikely theyll get like this until they get older, or if theyre pushed really hard, or both, so probably not somthing to worry about (but to keep in mind).

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Re: E-Kart Build

Post by markz » Apr 22 2018 8:24pm

I have read some people bulk charging up to say 4.05V then using a balance charger for the remaining charge to 4.20V. Saves a lot of time.

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Re: E-Kart Build

Post by garolittle » Sep 09 2018 6:28pm

This is an excellent thread that deserves revisiting. I had originally planned to use an 18650 pack for my electric go kart build but now I am considering purchasing six or seven Nissan leaf modules such as those referenced in this thread. If possible, my plan is to stack four modules on one side and three on the other and connect the sides with large gauge wire (probably 2AWG or 4AWG). Here is a possible source for the modules....

https://evbatterycenter.com/HAC4/index. ... Itemid=605

Motor/Charge Controller information:
Motenergy ME1004 PMDC Motor 48V 200 Amps Continuous/400 Amps Maximum for 1 minute.

Alltrax 48V/400 Amp Controller

My plan is to limit the max current to 300 amps to avoid stressing the motor/charge controller/battery. So what do the ES experts think? Thanks for any advice/suggestions/criticism you can offer.
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