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Upgrading my son's Power Wheels "Yamaha" ATV as a learning project
#1
My son has a Power Wheels Yamaha Raptor ATV that doesn't hold a charge anywhere near as well as it used to. We've been saving our change to buy a new battery for it, but I'm wondering if the 80 dollars they want for it is a sensible expenditure when I could built a Li-Ion pack that outperforms it by a great deal. This battery, when new, had a 12AH rating with a 12V output and a pair of 40amp fuses(unsure how they are wired on there, but I will find out as soon as I can).

What I am wondering first of all is should I build a pack that is higher than 12V. I've seen a couple of projects with these where people add a second lead-acid battery to bump the motor up to 24V, but I have no data on what actual motor is in it and how long it would survive the increased voltage. So I was thinking maybe 16V might be a reasonable middle ground. Perhaps do 4 sets of parallel cells in series and kept charged to no more than 4.0-4.1V? I've seen 8AH 18650 cells on eBay and even doing 6 of these per set could supply 48AH capacity(though obviously I never want to discharge them completely...). Realistic run time on this thing could be hours without the power loss that this lead-acid battery experiences as it drains. If I can salvage a better motor(brushless perhaps?), I would consider upgrading it even more, and maybe even putting proper tires on it. Maybe once we have our ideas all figured out, we could even consider just putting together a totally custom electric ATV.

Have any of you done a project like this? Any recommendations on how to proceed? Is there an existing DIY template I could follow that would suit my needs? I'm looking in to doing DIY home power storage and I think this would be a really good learning project for me that would also make my son really happy.

hbpowerwall likes this post
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#2
The DC motor can easily/safely take higher voltage than 12-15V. You could run it at even 20V. Altho, the motor will get hotter faster. But this also means that acceleration and top speed will be faster/higher.

To know the amp draw, put a clamp meter on one of the power cables, put about 50lbs in the Power Wheels, and press the throttle to full speed while holding it still (maybe tie it to a post or something) and this will give you a good example of peak amps needed for the motor at that given voltage.
Then you can build your packs accordingly to handle this amp with the appropriate parallel cells. If using laptop cells, figure each cell will only yield about 250mA under normal load and 500mA surge (this is quite generous, but may be fine for the kid toy as longevity isn't needed for a full day of use).
If using powertool or high drain cells, then you can figure around 1-2A per cell (depending on the cells characteristics).

Check out the https://secondlifestorage.com/f-Electric-Bikes-Cars for examples of these types of projects.
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#3
If you are going to buy new batteries, I would look at buying LiPo. Have a look at what HobbyKing have to offer. LiPo batteries are best for high current applications. Also, most can be charged at 1C so you can fast charge one in about 45mins, assuming you don't discharge below 3.4v and only charge to 4.1v.
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#4
I'd recommend running at 50% higher voltage max, so around 18V.

That means something like a 4S lithium-ion pack would be your best bet, with a cutoff voltage of 12V being optimal.
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#5
I've put 4s (16.8v max) lipo into my kids quad and it has been great. they can pull small catwalks when just starting to which they are thrilled. goes a bit faster and actually runs better but I also had to put a bit of rubber on the front tires as to give them more steering as it liked to push with the extra power
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#6
Charge Them to 4.2. why even bother half Charge Them? Do you expect to run the atv for 10years ? Smile


I would do 4s lipo for sure. Most bang for the Buck and just balance Charge with rc Charger. I have ton of kids Gear converted to that
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#7
(07-19-2019, 02:20 AM)Geek Wrote: If you are going to buy new batteries, I would look at buying LiPo. Have a look at what HobbyKing have to offer. LiPo batteries are best for high current applications. Also, most can be charged at 1C so you can fast charge one in about 45mins, assuming you don't discharge below 3.4v and only charge to 4.1v.

Thanks for the tip. I have heard LiPo cells are heat-sensitive though, and this thing does get pretty toasty out in the sun sometimes. Do you think that's a serious problem? This thing is going to sit right under my son so erring on the side of safety is a big deal for me.

(07-19-2019, 12:12 PM)jdeadman Wrote: I've put 4s (16.8v max) lipo into my kids quad and it has been great.  they can pull small catwalks when just starting to which they are thrilled.   goes a bit faster and actually runs better  but I also had to put a bit of rubber on the front tires as to give them more steering as it liked to push with the extra power

Great to hear! Do you have a project journal on any of these or any sort of how-to's, photos, etc? Sounds like you've done exactly what I'm aiming to do here!
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#8
Sorry to bring up an older thread, but to OP, I have modded my daughters power wheels (12v) to accept my cordless tool batteries and they are above the 12v range. They are Kobalt batteries. They say 24v but the are 6s (they calculate their voltage at full charge). Shes used it all summer with no issue.
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#9
+1, Cordless tool battery packs could make a lot of sense, 18V ones are common, swap out a battery to keep going, robust, plenty of chargers, etc?
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#10
With 3D printers, you could take the older chargers of a particular brand and make new shells to get them closer. Then design it so that you could plug them in so they could charge the wheels as well. And have a switch that would switch from charging mode to discharging, perhaps. But still allow the batteries to be swapped out.

For the power wheels vehicles, power tool packs would be great as they are designed for high discharge amps.
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