Battery choice for electric go-kart

[M0tWat]

Hello everyone,

I'm working on an electric go-kart project and need to pick the batteries + their accessories. I have a budget of about €300-500 ($330-550). My motor is the 3 kW 72 V Golden Motor (https://www.goldenmotor.com/frame-bldcmotor.htm) and a 72 V, 80 A Kelly controller (https://www.kellycontroller.com/shop/kbs-e/). My main objective is to be able use the power the motor can provide, even if only for a short time. 5 minutes of ride time would be sufficient, but the more the better, of course.

Considering this, I have come up with the following plan:
Buy 4x 18.5 V 5S 5000 mAh XT90 LiPos (https://www.amazon.de/HRB-18-5V-500...Ñ&keywords=lipo+5s&qid=1579893710&sr=8-5&th=1)

Put them in this configuration:

...and then put them into the whole system as shown here:


Buy accessories:
50 W charger (https://www.amazon.de/Netzteil-ORIG...80849968&sprefix=lipo+la,aps,194&sr=8-11&th=1)
XT60 balance board (can't find XT90) (https://www.amazon.de/Crazepony-UK-...ords=lipo+balance+board&qid=1580854053&sr=8-6)
XT60 and XT90 plugs + 10 Gauge wire to make adapters for the balance boards and connect the LiPos between each other (https://www.amazon.de/LHI-Männlich-...ÅŽÕÑ&keywords=xt60&qid=1580854198&sr=8-6&th=1 and https://www.amazon.de/LHI-Connector...ÅŽÕÑ&keywords=xt90&qid=1580853192&sr=8-5&th=1 and https://www.amazon.de/Silikon-Schwa...J7QGEN368K6&psc=1&refRID=1J6EAXRJWJ7QGEN368K6)
2x Bat-safes for safe LiPo charging and storage (https://www.amazon.de/Li-Polar-BAT-...&keywords=lipo+safe+box&qid=1579893319&sr=8-6)

What do you think? Is this setup of good value? Have I forgotten about anything important?

One thing that I am wondering about is that the LiPo I've picked advertises continuous 50 C, which would imply a continuous current of 250 A. As far as I know, this would require massive wires - around 0 AWG (https://www.powerstream.com/Wire_Size.htm), yet from the picture of the battery I can see that it has a 10 AWG wire. According to the chart in the previous link, that would allow for 55 A... So is it even safe to pull the 80-160 A that my controller would possibly allow? And what about the XT-90 connectors, that - according to the seller - are 120 A peak? I hope I'm misunderstanding something here, because otherwise the wires would be quite a bottleneck.

 

[DogDipstick]

YOu are on the right track. Do not worry about the current /conductor size so much as the load would not be continuous. With wheeling around and without 100% load you will not have much problem with 3Kw and 10 gauge. The 5Ah batteries would be long dead first from such ( >250A, 50C) current draw. (<1 min). As is, a 50A average load should give you a 10 min ride for a 50A = 10C discharge, not very hard. EV do not run continuously . Also, you are running a higher voltage and lesser current, for that 3Kw rated motor number, and the current will not be so much out of the battery.

 

[M0tWat]

Hi! Thanks for your advice. I would go ahead with the purchase, if it wasn't for some warnings I have gotten on another forum: http://www.diygokarts.com/vb/showthread.php?t=42809
Are those valid concerns?

 

[999zip999]

You need at less 15ah or more to go around the track. You don't want to every drain them.

 

[M0tWat]

You need at less 15ah or more to go around the track. You don't want to every drain them.

I'm not necessarily going to go on a track with this kart. Mainly I would like to test its acceleration and top speed.

Anyways, why 15 Ah? Shouldn't I be able to ride about 5 minutes with 5 Ah? For example, if I drew 40 A continuously on average, then that should equate to 7,5 minutes of ride time (5 Ah / 40 A * 60). Naturally, I would enable a low voltage cutoff on the controller to prevent the voltage from sinking too low and damaging the cells.

 

[999zip999]

You can just eat one potato chip ?
Venom kart made a battery out of leaf cells.

 

[M0tWat]

If I'll be able to finish this project and ride the kart for a few minutes, that's more like a truckload of chips from my perspective

AFAIK, leaf cells aren't all too easy to come by and building a 72 V pack would cost me around $1000, which is way outside my budget (https://www.ebay.com/itm/Nissan-Leaf-Battery-Module-Lithium-Ion-7-6V-64Ah-Gen-lls-/331954848206)