Battery banks and fuses

[Mark W. Ingalls]

All-

I am wiring up a battery bank to supply my wife's travel trailer when dry camping. I have always been a little bit suspicious of the way my Hawk (with one battery inside the truck and one house battery) was fused, so I did some digging around and cogitating.

It turns out that the American Boating and Yachting Council (ABYC) has a standard for 12 wiring, which states that every wire connected to the +ive terminal of a storage battery must be fused within 7 inches of the battery.

In my case, I have up to three storage battery banks connected in parallel-- Battery 1 is under the hood, and connects to battery bank 2 in my truck bed. When we are towing my wife's travel trailer these two battery banks are connected to the battery on the tongue of the TT. I need to fuse both ends of all wires that connect the +ve terminals of these batteries together.

Here is why: Consider what would happen if one of the "red" wires developed a short circuit to ground. Current can flow into the short circuit from more than one source, so every possible source needs to be fused.

The ground wires should not be fused, but (unlike high voltage AC wiring) there is no danger in doing it.

I decided to post this because, after I realized what I had done and started imagining all the different ways I could have set my camper and truck on fire, the old way of wiring my batteries scared the b'jeepers out of me.

Be safe,

Mark

 

[pods8]

Yeah we smoked this one out a year ago or so, it was a brain fart moment for me as well as I hadn't thought to initially put one on the feed IN from the truck. Good repost!

 

[Mark W. Ingalls]

Yeah we smoked this one out a year ago or so, it was a brain fart moment for me as well as I hadn't thought to initially put one on the feed IN from the truck. Good repost!


I didn't see that one, pods; care to add a link?

 

[ntsqd]

A comment someone recently made in a thread made me realize that I hadn't fused/breakered the camper battery either. I've since remedied that.
In that process I realized that the power panel, which is diagonally opposite of the battery in the camper, has 4 fuses totaling 100A but is fed by a 14 ga. wire. I realize that I'm not likely to pull 100A all at once, but 14ga. seemed a little too small. When I remove the Exlir charger/fuse/breaker assembly and replace it with a Blue Seas fuse panel & breaker I'll address that one as well. In the mean while the OE power wire to the panel is connected to the 80A breaker on the truck side, which has is down stream of the VSR so that it can't pull from the truck batteries unless the alt is charging.

 

[cwdtmmrs]

I have never been crazy about isolators, so I took a bit different approach when I wired my camper battery to the truck's charging system. I came directly off of the truck positive terminal stud with a heavy duty 40 amp fuse (the kind that bolts to a stud) to a constant duty 40 amp solenoid, then back to another 40 amp fuse at the positive terminal of the camper battery. Another 40 amp fuse connects to the feed wire to to factory fuse/breaker panel. All of the load wires are "hot" all of time, charging or not, so all have to be protected. I used 8ga wire throughout and trigger the solenoid from the key switch accessory circuit. That way the camper battery is charging whenever the key switch is in the "on" or "accessory" position, but cut out in the starting circuit and not trying to pull juice forward from the camper battery.

CWD

 

[pods8]

I didn't see that one, pods; care to add a link?


BenG pointed it out in the thread were sunman had some wires melt down (page 2). http://www.wanderthewest.com/forum/index.php?/topic/4513/

 

[SunMan]

BenG pointed it out in the thread were sunman had some wires melt down (page 2). http://www.wanderthewest.com/forum/index.php?/topic/4513/


Thanks for posting that pods. When I read Mark's post I instantly flashed back to that horror story. A lesson worth repeating for others who may have missed that post and have potential ticking time bomb electrical set ups. I often think about that day and all the what if's, glad my karma bank was full.

 

[craig333]

Thanks for reposting that. I know I intended to deal with that. Not sure now If I completed that project or not. Good thing to check today before I undertake a long trip. Its inexpensive too.

 

[Mark W. Ingalls]

BenG pointed it out in the thread were sunman had some wires melt down (page 2). http://www.wanderthe...hp?/topic/4513/


Somehow I forgot about that. Thanks plenty, pods.

My response action at that time was to move my "house" battery into the engine compartment, shortening the charge wire. I still only had one fuse on each "red" wire, not one on each end of the wire connecting my engine battery to the house battery. In hindsight, this seems inadequate.

Friends, this is important: Between every "red" wire and every battery put a fuse!

 

[ntsqd]

Looking thru Sunman's thread I keep seeing "re-setting breaker" being tossed around. The way that I see it that is the wrong choice in a breaker. If you have a dead short it will pop. Then the bi-metal in it will cool down and it will re-set the circuit thereby re-initiating the dead short. On and on we go. How would you, in a hurry, disconnect this circuit?

I used Blue Seas manual re-set breakers on both ends of our 6 ga. charge wire (btw also a 6 ga. ground wire back to the truck battery). If either of them or both pop, that's it, nothing further happens until I do something. They are positioned in the circuit such that all of the camper loads as well as the VSR are between the two breakers with the camper loads between the camper's breaker and the VSR. These breakers have a manual "break" button as well. They're not really designed to be used as a switch, but they can be.

EDIT: Just got to Leadsled's post on his use of manual re-set breakers. Those covers look neat, but I've been using vacuum caps over the studs for years. Still leaves a little exposure, but they cover the biggest portion of the studs and most of the nuts. FWIW I have not experienced the popping open of the manual re-set breakers that was predicted in the later posts. That may be due to my using this type of breaker in a 60A version (clicky):