Batteries wired in parallel are now fully charged

Dead Power Wheels Battery? Maybe You Can Trick it Back to Life! 1

It’s a story that repeats itself in garages across America every summer. Your kid wants to drive his Power Wheels Jeep, or her Power Wheels Escalade (is it really selling for $800-$900 on Amazon?)… and the battery is dead. You plug in the proprietary charging connector (if you haven’t lost it, that is), but the battery is too dead to charge. And even if you could rig up some sort of method to connect it to a “smart” 12V battery charger like the CTEK models I’ve reviewed in the past, the battery is too dead for the smart charger to sense it, so you end up with an “error” light. Which means you’re about to spend $56 for a new Power Wheels battery so your daughter can terrorize the neighborhood in her pink Barbie Cadillac Escalade:

Pink Power Wheels Cadillac Escalade

Pink Power Wheels Cadillac Escalade

Not so fast…

Remember this scene from Princess Bride? “There’s a big difference between mostly dead, and all dead.”

It’s possible that your Power Wheels battery is only mostly dead, which means there’s a chance you could revive it with this trick.

Forget the cheap-o OEM Power Wheels wall-plug charger. I took a pair of wire cutters to ours long ago. It’s a “trickle” charger, not a “float” charger, meaning it delivers a constant trickle of 12 volts at a low amperage to slowly charge the battery. But because the charger has no circuitry to measure the charge level of the battery, it never stops charging… which is why the manufacturer warns you not to charge it for more than 24 hours at a time. But nobody remembers to do that, so we all end up with over-charged (dead) batteries, or batteries that we forget to charge at all… which also end up dead.

A “float” (or “smart”) charger also delivers a low-amperage charge to the battery, but features circuitry that senses when the battery is fully charged. When that happens, it stops charging and only monitors the voltage. When the batteries voltage drops enough, the charger re-activates and fills it up again.

Like I mentioned above, I’d snipped off the “wall wart” adapter portion of our Power Wheels charger long ago and crimped a female spade connector to each lead, giving me something metal to which I could attach charging clamps from my trusty CTEK 7002 smart charger, which kept the 12V Power Wheels battery at the ready without risk of over-charging. But I use my charger for other stuff, too… meaning I sometimes let the Power Wheels battery sit for months without charging. So when I went to try and charge it yesterday, my smart charger sensed too little voltage to even register the existence of a battery on the other end, so the charger lit up its red “ERROR!” light.

That’s the main drawback of “smart” chargers… sometimes they’re too smart for their own good. But because I had those female spade connectors crimped onto my Power Wheels charging plug, I was able to “piggy-back” charge it by wiring it in parallel with a separate 12V battery, like this:

"Piggy-back" charging a mostly-dead Power Wheels 12V battery with another 12V battery wired in parallel

“Piggy-back” charging a mostly-dead Power Wheels 12V battery with another 12V battery wired in parallel

Prior to hooking everything up, I made sure the black 12V Werker battery shown above was fully charged to the point that that my charger lit its green “full” LED.

Then I connected everything as shown in the above photo: the positive spade connector from the Power Wheels plug is connected to the positive terminal of the fully-charged 12V battery, and the negative spade connector is on the full battery’s negative terminal. The “thirsty” Power Wheels battery immediately began drawing a small amount of charge from the fully charged battery, so that the combined voltage of the two batteries was well below 12V on my multi-meter. When I attached my charger clamps to the battery terminals (positive to positive, negative to negative), the charger sensed the circuit’s voltage, and decided it was was low enough to require charging, so it started charging. You can see in the first photo that the charger’s status LED is showing “more than 50% charged.” After a few hours in that state, the light turned green:

Batteries wired in parallel are now fully charged

Batteries wired in parallel are now fully charged

At this point, I disconnected the black 12V battery from the circuit completely, and connected the charger to only the leads on the Power Wheels charging plug:

Previously, the Power Wheels battery had been so dead that the CTEK charger gave up and turned on the error light. But after being wired in parallel and “piggy-back” charged, the Power Wheels battery had recovered enough to allow the smart charger to “see” it and start charging, so I let it charge like this for another hour or so before I checked it again. Eventually, the green LED indicated that the Power Wheels battery was fully charged. I disconnected the charger and confirmed with my multi-meter: a victorious 13.2 volts!

I put the battery back in the pink Escalade, and it ran like a champ. Because of its age, it’s hard to say whether this battery will still provide runtimes as long as it did when it was new. It probably won’t. But the good news is that it’s not all dead, and it’s not even mostly dead any more. I’ve dodged the $56 new Power Wheels battery bullet for at least another day. 🙂

Keep in mind this trick only works with batteries and chargers that use the same voltage — 12V in this case. If you have a 6V Power Wheels battery, you’ll need a 6V charger and another 6V battery to piggy-back. Do NOT try to charge a 6V battery with a 12V charger or “host” battery. Also remember that when you wire two batteries together, it really makes a huge difference whether you wire them in parallel, or in series. If you don’t know the difference or why it’s important, do some web searching on batteries in series vs. parallel before you start tinkering.

  • Jerry

    Since you’re a connector cutter, I have to share with you that everything in our household 12 volts has been connectoriezed to Anderson Power Pole using the Amateur Radio Emergency Service (ARES) standard. Ditto for any connectoriezed 12 volt supply in vehicles, and even my test bench. I got the power poles for ham radio, but use them daily for everything else. For example: Weather radio, 12 volt thermo-electric cooler…. power jacks in the boat, etc. That includes not only the the John Deere lawn mowers (and accessories like lawn sprayers), but the John Deere Power Wheels gator. I even spliced in connectors on a couple of my little APC SMART UPS. If I need another 12 volt battery, I can rob one from an UPS, with no fuss. Or I can power the SMART UPS from a vehicle. Or lawn mower. Or power wheels battery. And our 12 volt weed-eater? Yeah, it’s got a power pole connector. I can run it off the power pole outlet on the lawn mower and charge it while I use it. My 400 watt inverter has a power pole and we can get 400 watts out of it without getting the battery clamps out, since it can just plug in to the power pole in a dash of a vehicle. Currently, I think we use the wall wart that came with the weed eater to charge the power-wheels battery. I think the power wheels charger is currently connected to a power pole in one of our cars to keep the battery float charged. Mix and match. You have no idea how handy it makes life with 12 volts when every genderless connector can connect to everything else. One of my kids referred to them as “legos for electricity.” Anyway, finding chargers to mate with a 12 volt power wheels battery becomes easier now that everything hooks to everything else. I have run in to the “mostly dead” battery problem, but when you have all of the 12 volt options with power poles on everything, it’s not hard to find something to resurrect it. And I would like to think that we solved the problem of dead batteries in the power wheels Gator with a very pretty simple system. We have one Gator, and two batteries. The kids are trained to bring the dead battery to the work bench, and plug it in to the charger when they exchange it for a charged one. I used to have a couple of gel cell “bench batteries” with power poles, but now I just use one of the higher capacity power wheels battery when I want to do some task that requires portable power. If I want to run the 400 watt inverter off a power wheels battery, I grab both, and plug them together.