Fuse melting... any clue?

**russoxley187** · 06-15-2008, 01:28 PM

I have a 2001 f150 running 2 batts and they are hooked up in series...
I sorta drew a pic showing how hey are hooked up and where the problem is.
The fuse melts when I hook up the second battery.I have never has that problem before and I have not changed anything.
The second battery runs my amps and laptop computer through a inverter..
Any suggestions?

**FusionFanatic** · 06-15-2008, 06:08 PM

what gauge wire are you using to connect those batteries?

P.S. in your picture it looks like the batteries are wired in parallel, not series

**russoxley187** · 06-15-2008, 07:16 PM

its either 0 or 1, its thick.
No skinny stuff..

**colin** · 06-15-2008, 08:34 PM

Do you have a high power multimeter?

My guess is that there is resistance between the grounding points or something else along the line. I could be VERY wrong, but heat is a product of wasted power and power means there's resistance between the two points...

Check the wire between those points firstly, try checking the resistance all throughout the circuit, then get back to me

**billmee** · 06-15-2008, 09:40 PM

Tell us more about the batteries, are they the same size and AH rating?
Is the second a deep discharge type?
With the connection broken are you reading about the same voltage on both batts?
Also is the ground wire for the second also a 0 or 1 gauge?

Could be a bad cell in a either battery this will look like a load to the good batt.
It would be good to have a dc clamp meter ( sears ) to see how much current is flowing.

**HiJackZX1** · 06-15-2008, 11:12 PM

I dont know about this stuff, but isnt there some special device you need to hook up 2 batteries... A isolator or something like that? Also is it me or is 12+ going to 12v+..... is that correct?

Here is a link to the device you need... its called a Battery Isolator http://www.jcwhitney.com/2-BATTERY-S...0926_10101.jcw

**colin** · 06-16-2008, 12:18 AM

Yeah a tank circuit or isolator or something should probably be something to look into. If they're hooked up in series though, you would get 24v instead of 12... which I don't understand. If there's a difference though, you may be using one battery to charge another...

**billmee** · 06-16-2008, 06:42 AM

One more thing, with the car off....

Take the positive connection off the second battery and measure the voltage difference between it's positive terminal and the connection you just removed. It should be small.

Charge the battery with the lesser voltage over night.
Remove the charger and check the voltage difference again.

Lather rinse repost.

**jimmler** · 06-16-2008, 01:10 PM

You definitely need a battery isolator. That's not why your fuseholder is cooking, but the way you have your system wired, both batteries will still discharge and leave you stranded. With two batteries, it will just take longer. The isolator will allow both batteries to charge, but if you leave the pc on with the engine off, only THAT battery will be dead. The other battery will still start your car.

As mentioned in a previous post, it sounds like something has some high resistance. Pop the fuse out and make sure all the connections are bright and shiny. If there's any corrosion or anything, either replace it with new or try to clean it up with some ScotchBrite.

Good luck!

**wired48** · 06-16-2008, 02:06 PM

Connect the negative terminals of the batteries together with the same gauge wire you are using to connecting the positve terminals. The problem you are experincing is caused because you assumed using the chasis to act the grounding point , it will be 0 volts. However because of the resistance of the chasis, the battery in the rear will always be at a lower voltage than the battery at the front. This difference will increase when the batteries are being charged. This voltage difference will be distributed across the chasis and the wire connecting the positive terminal proportionately. Because the chasis is a large surface it can easily dissipate the heat. However the contact surface of the fuse holder is small; it will get hot. By connecting the batteries directly, the difference in voltage is significantly reduced and less heat is produced.