Today I'm upgrading the battery capacity on my 24v Grave Digger Power Wheels. The stock batteries are a pair of 12v 7.2Ah batteries run in series, for a total of 24v 7.2Ah. The stock 7.2Ah batteries were already lacking with the stock motors and I exacerbate that lack when I upgraded to faster Traxxas motors.
This article will detail how I upgraded to 20Ah capacity (nearly triple the run time of stock batteries). While I was in there, I added a charging port because having to remove the seat screws to charge the battery got annoying quick.
2x 12v 20Ah SLA Batteries (batteries between 18-22Ah share a case size, so you can use most SLA batteries between 18-22Ah. 22Ah would be even better, but I already had one 20Ah battery so I just purchased one more)
10awg Fuse Holder - this 10 pack is a great value, plus you should be using these on all your modded rides, so get extras!
24v 2A XLR Charger - Twice the charge rate of the stock charger, while still being safe for the new batteries.
Various Crimp Fittings / Scrap wire / Shrink tubing
Drill w/ 1" bit
Multi tool with metal/plastic blade
Step 1: Trim Out the Stock Battery Pan
The stock battery sat on a little platform of raised plastic ridges. All that crap has to go to make room for the much larger 20Ah batteries.
I found the easiest way was to cut straight down at each intersection with the multi tool, then score lightly along where it meets the bottom of the body. Then grab the pieces with a pair of pliers and twist it off in chunks. Keep test fitting your batteries and removing more material until the batteries sit flat on the bottom of the compartment.
If they made the bump outs just a hair smaller, the batteries would fit like a glove... but they didn't make this easy on us, so the batteries end up sitting in there slightly crooked. Hurts my OCD, but its under the seat and no one will see.
The seat also has some structural honeycomb cardboard on it that used to sit on the shorter stock batteries. I used the multitool to trim that down as well. Cutting it about in half fit on top of the new batteries very nicely.
Step 2: Wire Up the Fuse Holder
The fuse holder is one of the most important aspects of any modified power wheels build. DO NOT SKIP THE FUSE HOLDER. I'm wiring these batteries in series, so I used my 10awg fuse holder to connect the pos/neg terminals together. When I connect the vehicle wiring to the other terminals, this will create a 24v 20Ah battery cell.
If you're running stock motors, stick with the 30a fuse. If you've upgraded, you might need to run 40a fuses. If you up the fuse size, YOU NEED TO MONITOR TEMPERATURE OF MOTORS AND WIRING. If the wires and motors are getting too hot too touch, you are overloading your circuits and asking for melted wires, fires and hurt kiddos. Every riding circumstance is different, so if you're unsure of what you need to be aware of, don't modify your kid's ride on toys.
Step 3: Test the Charger and Wire Up the Charging Port
You need to find out which prong on the charger plug is positive and which is negative. Do this by touching the prongs with your multimeter (set to 20v dc). It should read +24v when you have the red on the pos and the black on the neg. It will read -24v if you have the leads reversed. Once you know which prong does what, label the side of the plug with +/- in sharpie.
Now compare the prongs on the charger with the socket on the charging port. Solder 12-14awg wires to the terminals on the back that correspond with the pos/neg prongs on the charger. You'll soon be attaching these wires to the battery, so make sure your polarity is correct.
I soldered my wires to the XLR receptacle and used heat shrink tubes to cover the connections. I just used scrap 14awg wire that I had laying around, although this port accepts up to 12awg wire.
Step 4: Mount the Charging Port and Wire the Battery
To mount the charging port, I simply drilled a 1" hole in plastic between the foot well and the under-seat battery compartment. I fished the soldered wires through the hole and screwed the receptacle to the wall. This will be where I plug the charger in.
Once I had the charging port wires into the battery compartment, I just cut them to length and crimped ring terminals on. I also cut the stock battery plug off the wiring harness and crimped ring terminals onto those 10awg wires. Then I connected the ring terminals to the screw terminals on the new batteries.
Step 5: Go Play!
That's it! Now you're ready to enjoy longer run times and easier charging on your 24v Grave Digger!
If you've enjoyed this mod, please take a look at my other Instructables. I have detailed write ups on improving the shocks, turning radius and speed on these new Grave Diggers.
I'll be posting the rest of my mods here as I continue to upgrade our GD, so follow me on here to see the latest mods!