HELP: Electric (SLA) Skateboard Battery Upgrade

[mjp8081]

Thanks for looking.

I am buying an M6-800 Altered/Exkate electric skateboard. Powered by 3x 12v SLA cells (36 volts, 12Ah) and an 800w motor. Speed and braking is controlled by a wireless 2G handheld trigger device and electronic board on the skateboard.

http://www.alteredelectricskateboards.com/m6_800.htm

I want to lighten up and improve the board with lithium batteries. For a while I was looking at the Chinese LiFePO batteries on eBay, until I read an article on this forum about the DeWalt 36v a123 batteries.

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=2498

Could I possibly use one of these without any modification?

THANKS!!

 

[Link]

No. The cells can do far more, but the packs they're put it are limited to 15A. The controller in the board likely peaks at 30 or 40A. And a single pack would only get you about 1/4 the range you get with the SLAs, so you'd need more than one, anyway.

I'd go with the Chinese stuff. Cheaper, and the A123's are actually 33V nominal, not 36V, so you'd lose a little top speed by going with them, though they'll likely live longer just because they're much better quality.

 

[mjp8081]

Thanks for that, Link. I knew it was probably wishful thinking on my part.

Another question then about the LiFePOs on eBay:

1) The makers of the skateboard said they experimented with these, and a 36v pack overloaded the electronics. Is this because they overcharge to 40v+? Is there a way to regulate the discharge voltage nearer to 36v? Or was it something else that fried it? The wrong Ah rating? If I upgrade the power source to LiFePOs, I want to make sure to avoid the same problem and make sure it's compatible.

2) Also, what Ah rating could I get away with? The OEM SLAs are rated at 12Ah, but because the motor is 800w I'm told I need more. I obviously don't need to commute long distances--the board is purely for an hour or so of fun. It will need some hill-climbing power though.

Thanks, again!

http://3.bp.blogspot.com/_yuxAcNzO_BM/Se98prE3CUI/AAAAAAAAAD8/MadkR7JsV4g/s1600-h/IMGP1042.jpg

 

[Link]

1) The makers of the skateboard said they experimented with these, and a 36v pack overloaded the electronics. Is this because they overcharge to 40v+? Is there a way to regulate the discharge voltage nearer to 36v? Or was it something else that fried it? The wrong Ah rating? If I upgrade the power source to LiFePOs, I want to make sure to avoid the same problem and make sure it's compatible.

WTF?

If they REALLY fried at the few extra volts LiFes peak at after charge, the electronics are utter crap. Tolerances on even cheap controllers usually are great enough handle another 12V battery. My $36 eBay board that doesn't even come with a way to modulate speed worked on 36V (up from 24V) without modification. If you can open up the controller and look at the capacitors (big cylinders) and FETs (black and square-ish with three legs) to check their maximum operating voltages, that should tell you what it can handle. They shouldn't have a problem with a switch from SLA to LiFe, but, if they can't, you can try replacing them with something better. Personally, I'd replace the board's controller with an RC ESC in that event, but that would also require some modifications to the throttle, which I'm guessing you'd rather not hassle with.

Ah has nothing to do with whether or not it fries. Ah only dictates how much charge the batteries hold, and therefore how long they last between charges. More is ALWAYS better, unless you're like racing a car and a bunch of extra weight would be a disadvantage.

2) Also, what Ah rating could I get away with? The OEM SLAs are rated at 12Ah, but because the motor is 800w I'm told I need more. I obviously don't need to commute long distances--the board is purely for an hour or so of fun. It will need some hill-climbing power though.

Figure you're getting 9Ah out of your current pack. What with the Peukert effect and all...

However, even Ping's batteries don't have the best discharge rates compared to mid- or high-end batteries, so the 10Ah packs would do slightly better than the SLAs in range, but probably wouldn't live very long. That's assuming the BMS would even allow that much current without tripping, which it shouldn't. A 15Ah might just cut it. 20Ah would be better, but you might have problems fitting it in there; check the dimensions to be sure.

And FWIW, these aren't cheap by a long shot. So be sure you really wanna do this before you drop any money on anything. You might be better off with a second SLA pack if you don't mind having to swap it out in the middle of a ride too much.

 

[mjp8081]

Thanks again, Link

Yeah, maybe they mixed up polarity? Even so, isn't there a breaker somewhere? I'm not clear on exactly what went wrong.

The main thing I'm trying to do is cut down on weight. What does ESC stand for?

 

[Link]

Yeah, maybe they mixed up polarity? Even so, isn't there a breaker somewhere?

Iunuh. A fuse/breaker wouldn't protect against reverse-polarity, so mebbe they did?

The main thing I'm trying to do is cut down on weight. What does ESC stand for?

I guess you could shave off a few lbs...

"Electronic speed controller". It's pretty much the same thing we use with ebikes. Finding one for a brushed motor (that thing is brushed, right?) at 36V would probably be kinda difficult, though.

 

[TylerDurden]

Maybe consider Milwaukee V28 powertool packs, Yardworks packs or Bosch fatpacks.

SLA sux so bad, you pay more in the long run. Lead *can* kick the amps out, but ugh... the weight, slow charging, short life...

 

[mjp8081]

Thanks Tyler

Those battery packs you mentioned would require the same disassembly procedure as the DeWalt, right? There is none of those batteries that would work without modification, true? I guess I'm asking why you recommend considering them. Thanks!

Is that your name or a Fight Club reference?

 

[TylerDurden]

IIRC, you could use the V28 packs at standard voltage and parallel them up & go slower, but in parallel you can get better current. Yardworks could run in 2sXp for 36V, with no mods.

36V Fatpacks and Dewalts should have terminals for discharge around the BMS, but with internal fuses ~40A... you might want smaller fuses inline to protect the internal fuses. Parallel packs to reach desired current.

Search the boards for more info (my memory ain't so sharp).

Also consider NiCd... big amps, fast charging and long life (not too light tho).

 

[mjp8081]

So I looked around, and basically you can parallel maybe 4-36v fatpacks to get decent Ah, splice in a smaller fuse inline, then what? BMS? Charger?

Sorry so Noob

 

[TylerDurden]

Some folks are using tool packs intact, by using connector plates that are on the tools from the manufacturers.

Kinda like making your EV into a large powertool that uses four packs at once.

Unsnap the packs and snap onto chargers when done riding.

Pack, BMS and chargers stay intact.

Check out Jondoh's bike. Nuts&Volts might be using Yardworks packs intact.

 

[mjp8081]

Cammy_CC said they can build a pack that wont output more that 40v, that will stay around 36v. Does that make sense? Is that a good idea?


So I think I might just order a 36v 15Ah from Ping.

 

[TylerDurden]

... I'm diggin the hell out of my single fatpack for a town runner/grocery getter. Realizing that 6 of these in parallel, while a bit heavy/bulky give almost half a kilowatt/hr @ ~60A for at least 500+ cycles for ~$300 shipped. Now that's a great deal if you need a powerful 37v12ah+ pack... $60 less than a comparable Ping pack that can only do 20a... sure it *might* last 2,000 cycles but by then we'll all be running on nuclear power or something!

http://endless-sphere.com/forums/viewtopic.php?f=14&t=10230

 

[skatetowork]

G'day mjp8081,

can you give us an update on how you went with the Ping Battery? I have recently purchased an 800W electric skateboard myself and I am also interested in lowering the weight and swapping the native SLA with a LiFePo battery. If you could let us know how your experience went it would be great.

Cheers, Kirby.

 

[Lock]

So I think I might just order a 36v 15Ah from Ping.

Mr.Pings eBay pages describe the 36V15Ah pack as "Wattage: 350 -500 watt"... the 36V 20Ah pack as "up to 800W"...
tks
lock

 

[kiwi_nigel]

Hi, I've been converting 800watt electric skateboards to run on LiFePO4 packs for the last 12 months with no issues at all

I source my 36V 15Ah packs from Optimum Battery in Hong Kong and have had no problem with the quality and reliability.

They "just" fit inside the existing battery compartment and weigh 5kg (which is a 10kg weight saving on the SLA packs!).

Performance is outstanding, leaves the SLA pack for dead. 30km/hr steady for over an hour!

The motor controller has no problem with the higher voltage of a fully charged pack (approx 43 volts), as far as it's concerned its just a battery pack.

My only advice is get a good BMS which allows peaks of up to 50Amps (a board climbing a steep hill draws 46ish Amps so the BMS has to be able to deliver that for a few seconds without cutting out)

I've also been converting the smaller street style boards (600watt), swapping in a 10Ah LiFePO4 pack which also works very well.

Cheers
Nigel

http://www.greenskate.co.nz and http://www.e4ride.co.nz

 

[Steff]

Hi there,
I'm quite new to these forums and first of all, I've got to say thanks to everyone for making it such a great start for everyone who wants to get hooked on EV:s in any form. I was initially googling for a good place get some replacement SLA batteries for my electric skateboard when I stumbled in here, and quickly came to the conclusion that I don't really want SLAs anymore. So, I am also looking for some help regarding going LiFePO.

My skateboard of unknown (Chinese) origin is powered by 36V, 3 * SLA (12V, 9Ah), and a brushed 600W motor using a belt drive to one of the wheels. I haven't been able to measure what amps the motor draws, but I suppose I should do that before deciding on a battery pack.

After reading this and other threads, my options for new batteries at the moment seem to be:
- Ping V2.5, 36V 15AH
Costs $385.00 (charger included), and pingbattery.com suggests "Suitable Wattage of Motor: up to 600 Watt, 450 Watt suggested". Seems OK, but perhaps unnecessary heavy/large.
- Ping V2.5, 36V 10AH
I doubt that I need 15 AH for my commuting, and the weight difference compared to the 10Ah pack ($289.00) is almost 2 kg.
Not to mention the difference in size which really matters for making it fit under a skateboard while keeping some ground clearance.
However, the Ping site says that their 10Ah packs are for a motor "up to 400 Watt, 300 Watt suggested". So I guess I'd either kill the pack fast, or get cut-off when starting too fast/going uphill if I chose this one.

- Get Nigel (previous poster) to ship to Europe
12Ah LiFePO4 Battery Pack (~500$, http://www.greenskate.co.nz/lifepo4-battery-packs-2/)
"The packs are made up of 12S4P - 26650 Cells (3.2V) 3000mAh, 3.2V @ 12Ah x 12 to give a rated pack voltage of 38.4 Volts"

- Build my own custom pack
This option would also require me to find a suitable charger, get a BMS and also the knowledge on how to actually build a pack... which could be fun, but also very expensive when I destroy something in the process. But then again, I'd probably learn a lot and could get a pack that fits by board well.

As an example, using A123 26650A cells: 3 packs of 10 cells from Hobbycity would give me 6.9 Ah, 33V for 448$, which would give me around the same Ah as I currently have in my SLAs? Scavenging EBay for DeWalt's might be a better option. At 10C though, I shouldn't need to worry about killing the pack with the amps for my 600W motor.

- Forget about LiFePO and keep it simple, buy new SLA's and hate them
Sounds boring and expensive in the long run, doesn't it?

This leads to the following questions:
1) Do you have any advice? Have I missed any popular battery packs or misunderstood something about Ah:s, Volts and C:s for building an own pack?
2) Is it because Nigel has been using better cells than Ping that he's been able to use 10/12 Ah packs successfully with a 600W motor?

I'm also thinking about going for a brushless motor and building a entirely new board instead. The motor currently on my board is something like this,
http://www.rokitscience.co.uk/online_store/electric_skateboard_replacement_motor_600w.cfm
I just can't seem to find any brushless motors similar to whats on these types of skateboards, but a low Kv Turnigy or HXT, as discussed in many other threads in this forum, sure seem to be of better quality than the motor on my current board.

I do see a lot of challenges here, just mentioning a few:
- Getting the remote for the skateboard to work with a brushless RC ESC
- More expensive batteries are required in order to support the higher amps for these motors
- Keeping the motor protected and cooled underneath a skateboard
3) What are the benefits of going for a brushless motor for a skateboard? (either a "R/C type monster", or if I manage to find an brushless motor, with windings resulting in something similar to the brushed I've currently got)

 

[Lock]

Hey Steff...
welcome aboard the Good Ship ES... Yer right. Excellent crew. About yer ride... Is this an electric deck intended for Olies etc?

...didn't think so... So why not consider adding (handle)bars to yer ride? When the US CPSC studied kids kick scooters (hospital admissions) versus bikes/decks/blades years ago they concluded that the kick scoot kids were having accidents 1/2 as many as their classmates learning pedal bikes with injuries 1/2 as severe, and both kick scoots and pedal bikes far, far safer than decks and blades...

My two cents? Consider adding handles and real brakes to yer ride... Lottsa threads on ES w/folks motorizing kick scoots... Success to ya
tks
Lock

 

[mrzed]

What you are looking for is A not Ah, so the prismatic packs like ping are not the best choice, because in order to get the A, you are overdoing the capacity.

Seems like a good candidate for Lipo, or at least a higher rate lifep04 like headway cells.

 

[Steff]

Lock:
Nah, you're correct in assuming that these decks are not intended for ollies etc. I find that they're a bit heavy for those kinds of tricks.

I'm not really considering adding a handles to it though, since what I'm after is a fun way to get to work at morning. And in that regard, I really think a kick scooter has a hard time beating the sensation of longboard carving - especially when you can do it even uphill with one of these motorized longboards. Otherwise I think I'd simply go for a bike with an electric pedal assist system, if only for the simple fact that it would actually be legal around here.

Mrzed:
I think I'm ready to sacrifice some performance in order to feel a bit safer around my batteries, and lifepo seems like the safer bet (thinking fire hazard here). Thanks for mentioning the Headway cells though, I've been reading up on them and, like you say, choosing better cells seem like a better option than overdoing the capacity .


My problem is just deciding what cells to use. I guess a good source for information is finding reviews on this forum, rather than just trusting the specifications from different manufacturers/retailers. Good thing it's way to cold for longboarding here now, so I got quite some time to do the research before chosing batteries. Need to get the amp draw measured as well...