Souping up a Razor

[Canuke]

As some of you may know, The Sharper Image retail chain is in liquidation; the store where my fiance worked just shuttered its doors yesterday. While they were cleaning things up, I found some merchandise returned as defective that were slated to be disposed of -- including three Razor "Vapor" Scooters . I picked them all up for a few bucks.

These are powered by a pair of 12V 7Ah SLA batteries feeding into a 250W motor. Given the proclivity of these things to die if not kept topped up, I expect that's what will turn out to be defective.

But then I wondered, what sort of upgrades would work here? Lithium batteries would be a great upgrade -- more power, and much lighter to boot.

The motor is a 250W MY1016 24V motor. What lithium setup, if any, would you use for this application? The only restriction is that the power pack fits into the space occupied by the 2 12V 7Ah SLA's.

I'd also appreciate anecdotes and/or links for tips on constructing power packs and charging them, as I don't have any experience with it (though I do have the mechanical and electrical background), as well as recommended manufacturers for the cells.

EDIT: some googling reveals LiPo packs at batteryspace.com, but these run about $300 each for comparable amp-hours.... how much do I stand to save rolling my own?

 

[Sgt. LED]

I request lots of pics to get things started!

 

[Canuke]

Hi Sgt.,

I won't likely have time to do anything with this until the weekend, but I'll be sure to document the potential project as it goes along.

More googling reveals some interesting videos of battery pack construction involving A123 cells here.

 

[bob_ninja]

Here is a good approach:

http://www.endless-sphere.com/forum...sid=e7e8c9e97452fce99763b8b1171d7ffd&start=45

Also you'll find plenty of info on the site.

 

[Canuke]

OK, I just drank from the firehose of that link, thanks Bob! From there, I found this thread which talks about using the a123 cells in the DeWalt battery packs.

However, before I dig into that, I need a bit more of a grounding in some basics, which I haven't run across yet; too many conversations I've been finding are all between people already schooled in this side of things, and I'm still a bit lost.

1. IS building a lithium battery pack as simply as hooking them up in the necessary series/parallel configuration and away we go? I expect there's more to the equation, though it sure doesn't look like it at the DeWalt-related link above. But then again, what is a "balancer" plug for?

2. When building a pack, do I have to pick and choose among cells to match them up? Or can cells with varying capacities easily coexist in a pack? Do the good chargers somehow accomodate that variation?

3. Regarding motors: How tolerant are DC motors to different voltages? Wha are their input characteristics? The motor I'll be using is the MY1016 type rated at 24V 250W. What happens if I feed it 36V from some DeWalts? (The guy at bob_ninjas' link was feeding more than 500W into a 250W rated 36V motor using custom controllers). What if I give it only 20V?

I'm somewhat temtped to pick up one of the ready-made packs at Batteryspace, but I'd like to make this as do-it-myself as possible, down to installing LED headlights and my own low voltage warnings etc... this is as much about tuning up my hardware skills as it is about having an electric runabout. (as an aside, once this thing is built, the next project will be to set up solar power charging).

 

[Nubo]

An NiMH alternative

http://nilar.com/index.php?pageID=33&languageID=1

24V, 9AH but I read somewhere they make a 12V also.

 

[Canuke]

Well, after digging around, so far it looks like the savings to be realized by building my own are rather minimal. I'm also finding a lot of technology links, like the Nilar one mentioned by Nubo, as well as this one that I found on a British e-bike enthusiast board, which are long on specs but short on where I can buy the product.

I plan to finish reading up on the a123/DeWalt setup at endless-sphere.com, as the notion of running a small scooter on the same batteries as in the Chevy Volt is pretty appealing.

But first, tomorrow I have the day off, so I'm going to check out the scooters and see what's busted.

 

[Canuke]

As I hoped, two of the scooters were fine, all they need is new batteries :rock: The third one still had some life in its batts, but the rear wheel was removed, so I have to reassemble that to see why it was returned as defective.

There is a heatsinked component in all of these which acts as the throttle, and includes a 20.5V "undervoltage" cutoff; this is cool, as it means I don't have to add my own low voltage protection, at least for NiMH's should I go with that cheaper option.

I cannibalized two freshly charged SLA's from some UPS units and ran the two known good ones around a bit; I don't know if it's voltage sag, motor limitations or my own weight (I'm just under 180lbs and the scooters are spec'd at 150-170 lbs max rider weight), but they were very sensitive to inclines, bogging down sharply enough to make me wonder if one of the UPS batteries was bad... but the cutoff did not engage.

I'm going to complete the R&D on the a123 solution this weekend, and then decide on whether I will also upgrade the throttle/motor combo as well.

 

[Nubo]

Well, after digging around, so far it looks like the savings to be realized by building my own are rather minimal. I'm also finding a lot of technology links, like the Nilar one mentioned by Nubo, as well as this one that I found on a British e-bike enthusiast board, which are long on specs but short on where I can buy the product.

US Distributor for Nilar batteries:

http://pluginconversions.com/phevs1.html