What batteries are you running?

[itsid]

actually a good idea to take some pyrometer samples if you own one.
Surely doesn't hurt to know what temperatures you are actually dealing with.
(well get a good idea of the temps.. since I doubt you're willing to properly calibrate it )

Anywhoo.. also: please add a load measurement..
cold unused for hours,
then 30seconds up the steepest incline you can find and promptly measure again.
(ideally the wedged inbetween packs, not the top ones)

Also: if you series wired just four (as you stated iabove)
you are up for 96A continuous not 180A. (only if you wired both sets in parallel 180 is a viable continuous draw..)
Since you'll need roughly 42Amps max (if geared properly) not to mention nasty peaks...
that's about 50% of the allowed continuous discharge thumbsup
with just four of the packs... a good safety margin IYAM.
Still temperatures are better be checked.

if you can run a fully charged set dry (well till the controller triggers undervoltage protection)
as quick as you can (10mins or such)
very little chance the batterypacks will ever see more discharge abuse
(as long as you do not increase capacity of course)
that raise in temperature should therefor be about the maximum as well.
and with that you can feel reasonably safe IMHO.

'sid

PS I'm still for velcros instead of cutout foam to hold the packs in place...
but that's just me

 

[sikbrik]

Thanks for the testing suggestions! Very much appreciated. Added some venting holes which I'll screen over to keep grass/debris out.

Also going down the Velcro path with airspace in between... I'll probably test both to see what the actual difference is because the foam is more convenient for loading/unloading the packs. I won't trade safety and lifespan for convenience, though!

 

[itsid]

I'd say for now stick with what you have and take a close look at the temperatures involved;
if they're perfectly fine there is no reason to improve cooling for now.

If you think it could be slightly better, maybe cutting vertical grooves in the foam
so that it's grabbing the batpacks with ridges instead of 'solid' walls is doing the trick already

maybe you can (depending in the foam density) get away with nothing but an
inch of foarm on each corner (half an inch per side) even,
that way you'd even have nice routes for the wires and can grab the batpacks even more conveniently.

I have several velcro ties laying around (pack of five in the local dollarstore... a no brainer)
ties my cable to the laptop PSU for easier storage, tidies up the annyoingly long ethernet cable behind my computer etc...

So yeah, I'm fast in velcrotying part A to part B
(even riveted one into my car's trunk to hold a slightly more sophisticated toolkit in place )

Use what works best FOR YOU; as long as you keep an eye on shortcomings, I doubt you'll have much of an issue.

'sid

 

[Functional Artist]

Check out these bad boys

https://www.ebay.com/itm/LG-Chem-So...r-16-Cells-2-5-kWh-each-64-volts/142700202089

Its a 60V (64V nominal) 2.5kWh (~45AH) lithium battery section. (~$400.00 delivered)

It's basically like the Chevy Volt 2kWh sections, just these are configured as 16S
(the Chevy Volt sections are configured as 12S)

Since their both designed & built by LG Chemical I would anticipate the same level of quality.
(professionally designed, closely matched cells & professionally constructed)

Here are some specs:

LG Chem Module
-Number of Cells: 16
-Construction: 16s
-Length: 14.5"
-Width: 9"
-Height: 6.5"
-Weight: 40 lbs
-Output Terminal: M6 nut
-Amp Hour: 45Ah
-Total Voltage: 64 vDc
-Chemistry: NMC
-Capacity: 2.5 kWh
-Output: 10C
-Density: 138Wh/kg

I notice, the positive (+) & negative (-) terminals are on the side (not the top like the Volt batteries)
...there are NO coolant channels along the sides (like the Volt batteries) these seem to use a metal cold plate on the bottom concept for cooling
…& the connector plug has BMS leads to the individual cells & some temperature sensor leads that may come in handy too.


These battery packs seem to match up pretty well with the voltage parameters of most 60V lead battery packs

Fully charged this lithium battery pack would be ~66.4V (4.15V per cell)
…& the low cut-off would be ~51.2V (3.2V per cell)

Full charged a SLA (lead) pack would be ~66.5V (~13.3V per cell)
…& the low cut-off is ~50V (~10V per cell)

* It's the amount of "on board" energy that is the BIG difference
(~45AH lithium instead of ~12AH-~20AH for most SLA's)
…& with 45AH of energy you should be able to ride all day

 

[sikbrik]

That thing is awesome! Great price, too.

 

[Quinc]

@FA that is a deal right there! cheaper then buying leaf cells and building your own pack. Maybe ebay will drop a 20% off coupon soon and make the deal really good!

 

[sikbrik]

"spark free" plug on the series wiring

 

[Quinc]

"spark free" plug on the series wiring

Looking good! Have you tried them yet?!

 

[sikbrik]

No... working too much. Still need to hard-mount the box. Hopefully next month it'll be back in action.

 

[Panhead5496]

WOW! Those are some nice looking lipos!

 

[sikbrik]

Maiden voyage on electric...used to hit about 35mph on a 2 stroke race engine.
Really happy with 27mph and enough torque to do donuts on 13" turf savers!

Batteries did well. I didn't charge them to peak capacity but about 15.9v each.

Itsid was right about the heat trap...top batteries Rose from (uncalibrated) 70f to 76f. Bottom rose to 93f! I swapped them halfway through the run. We probably played with it for 30 minutes but it was only around 15 to 20 minutes of full throttle mashing runs.

Will keep testing and posting back.

 

[sikbrik]

Getting about an hour of playtime per set. Since we have 8 lipos, I balance charged one set this morning and then balance charged the other set while he drove that set down.

The 20a charger gets them topped back up in about 90 minutes, which is awesome so we rechecked the kart fasteners while we waited for the second set to charge. Now both sets are just cooling down and waiting to be topped up to storage voltage.

After 2 hours of riding a rigid kart in the yard, he's beat up enough to want a break.

 

[Quinc]

Batteries are on sale again!