‘21 6.7 F-350. This truck sits in the garage the majority of the winter to avoid the salt. For the past two years I have popped the hood and hooked up a NOCO Genius 5 charger/maintainer with the alligator clamps (been meaning to permanently mount the eyelets) it worked fine with the exception of the NOCO shutting itself off after a couple weeks, unplug from wall and re-plug in and it would go back to maintaining. This year I try to do the same thing and it keeps blowing the in-line fuse of the maintainer almost instantly. Tried hooking to other battery just for grins, although batteries are both still hooked together within the truck wiring, same results. Tried hooking a Genius 10 to both batteries, same results. Tried hooking positive on one, ground on the other, same results. Tried positive on one, ground to grounding lug on truck, same results.

Two different chargers, hooked multiple ways, keeps blowing in-line fuse.

Truck still starts and works as normal, but I can not get a battery maintainer to connect and not blow the in-line fuse on the maintainer.

What is wrong?

Thanks for the help.

Edit: Both charger/maintainers work on other equipment/vehicles bigger and smaller in size.

 

Suggest disconnecting the batteries from each other and try the charger on each battery individually. Beyond that, contact NOCO directly for help.

 

A fuse blowing = too much current draw.

Pull the negative cable off the passenger side battery. Connect the charger to the driver battery. Does it blow the fuse when connected to just one battery?

 

Agree if charger works on other vehicles. You could have something on truck not shutting down.
I would get a meter that can handle 10-20 amps and see what draw you are getting from truck
when everything is supposed to be off (more or less).

 

Thank you, I was thinking of doing that, disconnecting and isolating batteries individually, will do later today and let you know. Problem with that, is if it does work, what does it mean? If its bad batteries (seems to be a ford trend) thats easy, but diagnosing electrical gremlins is not my strong point, lol. Will keep you all posted.

Thanks again.

 

Very strange. I would not think the fuse would ever have a chance to blow, unless there is some current being applied back to the charger.
I would assume that the charger is limited in how much power it can put out, and that the fuse is over that limit.
I definitely would check with Noco.

 

How many amps is the charger?

I have a few 6a smart chargers that I only use on motorcycle batteries.
My truck has dual batteries and if I needed to charge it manually or run it thru conditioning…I would disconnect the batteries to prevent pcm gremlins.

give you an example…my 70 dollar 6a smart charger on a motorcycle battery disconnected from the bike ….charger says charging to 95%, I check the voltage at the battery terminals and I get 15.25 volts.

I wouldn’t put a 15.25 volt charger on my truck charging system…the trucks electrical system would try to drain the charge to 14.75 volts…this behavior may be why your blowing fuses.

you don’t need your pcm arm wrestling your smart charger. Disconnect the battery and try that.

 

Poor trouble shooting on my end. No problem with truck or current batteries. One of the Nocos was bad. I just spent the last hour or two (few beverages involved) isolating and trying different things only for the light bulb to go off in my head that the whole time I had been using the same set of alligator clamps. Pulled a different set off another one and tried them with the chargers and all works as it should and has. It was the set of alligator clamps. Verified this by blowing another fuse in them. Couldn’t find anything visually wrong with them, threw them away.

Sorry for wasting your time. Appreciate the ideas and help.

Thank you.

 

How does it go about trying to do that? Does it turn stuff on, even with the ign off, to use "power"?

 

Because of all the differing opinions, I contacted Clore tech. Here is there response. Not what I was hoping as I wanted to run a plug to the grill from each battery to keep them on a maintainer without needing to open the hood. Noted to Clore Tech that I have a 2023 Lariat with the inverter and dual batteries..

 

I would not expect the system to 'drain' the voltage. It definitely would control the alternator while the engine is running to not produce power when voltage is higher than it's set level.
I could be wrong, but charging systems usually are like keeping a bucket filled partway. The bucket (battery) has a leak (power usage), and the alternator refills the bucket as the level (voltage) drops. When the voltage gets high enough it shuts off.
Not sure how Ford does this exactly, but there is usually an overvoltage protection built into the system, which shuts down the modules if the voltage exceeds a certain level. I assume it is built into each module. I have experienced this on a GM with a plow-sometimes angling the plow with low electrical loads, when I let off the control and the electric motor stopped it caused the voltage to spike, which shut down the radio and a few other modules for a second. This was due to the computer seeing a voltage drop, then ramping the aternator to full output, then suddenly no longer having that draw, and the battery basically already at full charge, so no place for the power to go.
All that said, with the ignition off I don't see how any of the systems would be regulating power.

 

The reason is because if one battery is bad the charger cannot tell. It will only see the average voltage, and will charge appropriately for that voltage. This could cause the good battery to become overcharged and damaged. If there are any features built in to alert to a bad bettery the good battery would mask the signs, so the charger will not work properly.
They are protecting themselves from customer complaints and the potential liability if a battery has an issue (leaks/explodes/etc.) by saying to charge them individually.I suspect nothing negative would happen if both batteries were equal in condition and capacity. But if something happens to one there's no guarantees.
FWIW, it appears that the stock charging system charges both batteries together. They are run in parallel and there does not appear to be any disconnect, so it certainly appears Ford charges them together.