M.L. Toys
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for 12v vehicles that NEED to be upgraded to 18v
By Biggjimm
So my granddaughter accidentally stuck the key in the charge port! Yikes!
Fortunately, all is well. It was just a quick short & so far everything seems to work correctly. The fuses in the modules did not blow. The sudden shower of sparks scared the bejesus out of her though.
I had just unplugged the charger & as I was laying the charger aside she stuck the key in before I closed the door on the charge port.
It's a port like on a laptop, 5.1mm or so & it's on the dash about 5 inches to the right of the key switch. Bad design on my part.
You know what they say about hindsight....
Anyways, rather than move it right now, I thought if I put a diode in the line to prevent that from ever being able to happen again.
All I have on hand are 4007 & 4002 diodes. The 4002 is a little more robust than the 4007.
Which one should I use?
I don't know much about diodes but the larger 4002 is from the charge port of a cordless drill that I think was 18v so it should probably handle it.
My charger is 18v 2amp that I got with the batteries from mighty Max.
Thanks. Jim

User avatar
By wired
Hey Jim,
Sounds like the fuse/breaker (if there is one in your charging circuit) did not do it's job and luckily nobody was hurt. Here are a couple links for diode info. Read carefully about how the diode works in regards to your proposed application and also the voltage drop you will be inducing into the charging system. There should be a fuse or breaker in the circuit that would open to prevent this from happening. If I am reading your post correctly (forgive me if I'm not), the key was placed into the vehicle/battery side charge port. I recommend placing a small fuse/breaker on the wires to the charging port. A 5amp breaker should be large enough to cover charger amperage but small enough to open quickly if shorted out.
By Biggjimm
Yes wired, that is what happened. It is fused. It was just a quick, merely brushing the key across the terminals in the charge port. Perhaps just fast enough to not blow the fuse??
I'll read those links you provided. Thanks.
It may be covered in those articles you linked to but I was thinking, which is dangerous sometimes, if this charger is the voltage sensing kind, my idea wouldn't work anyways as the charger would not be able to detect the voltage at the charge port, correct?
I'll read through what you've provided & see where I'm at after that.
Thanks again. Jim.
By Biggjimm
I have to admit, that is quite complicated. I think my brain is kind of mushy now after skimming over that second link.
Maybe I'll just move the charge port to a safe location where no one can put the key or anything else in it that is not supposed to be in there.
I thought the diode would just simply block the current & prevent a short if the key was inserted in the charge port again. I didn't realize the complexity of those little guys.
I will definitely have to read through all of that info when I have the time to sit down & absorb it all. Like, when its quiet. Lol.
Thanks again wired.
User avatar
I'm not sure this is the right application for a diode since you're trying to avoid voltage drops. While subtle, it's still a drop and will reduce your full charge.

Something else to consider may be a relay. I know, relays consume power and that will extend your charging time. BUT, they don't reduce your charging voltage. Now, you don't need a big 30A Bosch relay for this. A 2A or so relay with a small 12v coil will be more than enough and will draw minimal power. You should be able to find these online for a few bucks. Use this to isolate your +12 line to the charge port. You'll of course need to test and see if your charger will trip it so you connect to the battery, but the benefit here is that once you remove the charger, the relay opens and isolates your +12 line making the charge port 'dead'. Food for thought.
User avatar
By wired
Just a thought here. If you want to keep it really simple, you could install a small toggle switch to the charge port. this would perform the same protection that CJB described with the relay but it would make it a manually driven switch instead of automatically operating with charger voltage. Flip the switch on after connecting to the charger to close the circuit for charging and then flip it off to open the circuit before unplugging the charger. Just put the switch somewhere not easily accessible by small hands. ;)

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