Fuse size for 2nd battery

Hey everyone, I recently started setting up my second battery for my 06 DC. While in the process I realized that I need to throw a fuse in line with the battery for safety reasons. Just wondering what size I need, I spoke to some buddies and they were saying to just use the same size as my main battery. I checked the fuse box and I saw that there was a "battery charge" fuse and I believe it is a 30A fuse? I just need someone to confirm for my peace of mind or just inputs would be nice.

 

How are you using the second battery? (isolated/just for running accessories, completely integrated into the existing system to add reserve capacity) How are you wiring it?
Fuses are there to protect the wire. So the size of ther wire should dictate the size of the fuse.

 

I plan on using the battery as a house battery while camping/fishing; powering an inverter, some usb stuff, camp/fishing lights. I do have an isolator that I am planning on running as well so the second battery isnt always in the circuit and I am also planning on having the second battery completely removable so I can just unplug it via some anderson plugs I recently picked up. Kinda hard for me to describe how Im going to wire it up so heres a link to an isolator kit thats similar to the one I got, theres a wiring diagram in there thats pretty much how Im going to do mine;

https://www.keylinechargers.com/pro...-keyline-chargers-voltage-sensitive-relay-vsr

I am currently running 6 awg cables (same size that came in the isolator kit).

 

You’ll want to know the power draw of the items you’ll be using to determine what fuse (and wire size) you need. 30A is low IMO. (12x30=360 watts max). I run an 80A fuse for my stereo system for comparison.

 

While it is hooked up and charging I wont be using it for anything else, just charging the second battery until I get to my destination which then I'll disconnect it and hook up whatever I need. You are correct though, 30A might be a little too low if Im gonna run a 1500W inverter.

 

In that case, Toyota uses a 40A fuse on the auxiliary charging circuit to the 7 pin trailer connection if you care what their engineers came up with...

looks like 6 AWG is good for 75A.

 

Awesome! thanks man.

 

Check the manual for your inverter to see its max amps/watts on the input side. It sounds like that’s going to be your largest draw. Then add to that the rest of the accessories you’re planning.

Also, be aware the charging amps have the potential to be huge: like the max output of your alternator. (130 amps?)
So I don’t think 6 AWG is going to cut it.

EDIT: Never mind that second part... I just looked at the isolator kit you linked to. It's good for 140 amps, so you're all set.

BTW, what will you be running with your inverter?

 

https://www.potekelec.com/product/319/Kinverch-2000W-Pure-Sine-Wave-Power-Inverter

This is the inverter I have, it says in the description that it has an internal 30A fuse so I think Im good there.

So far Im planning on running my little 50$ electric bbq grill, water heater, maybe a little travel fridge/cooler (still gotta look into that), various electronics (radio, speaker, laptop), maybe some site lights but thats probably achievable by hooking straight to the battery box itself . I still need to look into picking up a solar panel so I can keep the battery topped off when not in use.

Are you running anything similar?

 

Electric grill and water heater? I would highly recommend against those. Electricity is an extremely inefficient way to make heat. Are those 110v AC or 12v DC?
Propane would be the way to go for heating food and water.

 

Sorry, didn't see this question. I was on my phone and didn't scroll down far enough.

I had a pop-up camper until last summer, when I switched to a hybrid camper. I only camp in the summer, and only off grid -- with no power or water hookups. We cook outside with a propane stove and a propane grill. Although I've stopped bringing the grill because it makes a big mess that's difficult to clean. Water for washing had always been heated on the stove, but with the hybrid, I now have a shower (one indoors & one outdoors) and a hot water heater. We only shower every other day, so the water heater is kept off. When we want to shower, I light the heater and it comes up to temperature in about 20-30 mins.. Once it's up to temperature, I can shut it off, and we get two showers out of it. (we're pretty conservative with water because when you're off grid, clean water is a valuable commodity.

I have a single 12v deep cycle battery and a 200 watt solar array. The only things I have that run on electricity are the electronics for the propane fridge/freezer (1/10th of an amp), chargers for cell phones and iPad, and lights -- which have all been converted to LED, and are generally used for less than 30 mins per day. As far as electric use, I generate far more than I consume so I could stay out indefinately. Fresh water and waste water capacity are my limiting factors. I can easily go for more than 1 week... and could stretch it to two weeks without much difficulty. To be clear though, where we camp isn't out in the willy-whacks. It's on a well-developed lake with private homes, all around it. We just don't have power and water on our property. The convenience store is 4 miles up the road (for ice, beer, etc.) Two supermarkets and a Super Walmart are about 8 miles away. And someone makes and ice/beer/food run just about every day.

 

Yeah I know, unfortunately I found that out after I already bought everything lol. Lesson learned. You are correct, propane is much more efficient producing heat. I'll probably end up picking up a small propane grill and burner soon haha.

 

I've been looking at pop up campers as well but I dont think I've seen hybrid ones before, I'll have to check them out. I havent been camping like "real" camping where you take a dirt/gravel road off the main paved road for probably an hour or two and just turn off to a narrow path that was made by other like minded campers for probably a mile or two. We usually tend to stay at these little man made clearings very close to a stream or river so water wasn't an issue (my pops always brought a water filter with us for drinking water, this was probably 20+ years ago so pollution wasnt really an issue up there but better safe than sorry). We used the camp fire/coals to heat water as well as cook food, but now that I'm older and technology has progressed I've decided to bring the comforts of home out there with the criticism of my pops haha. Food mostly meat was brought with us, the rest was either foraged or hunted/fished in the area. There are alot of plants and berries you can forage for and eat safely as long as you know what to look for.

I have no idea what kind of battery to get as a house battery or the size of solar panel so I think you're the right person to talk to. What size and brand is good to use as a house battery? Also I know absolutely nothing about solar panels, what size or brand would be good?

 

Hi @dropindeuces.

There's a lot of variables regarding battery type, solar panels, chargers, etc.. I'm really busy with work today so can't adequately respond... but will this weekend.

You have to do your homework though. You need to figure out how much power you'll be consuming. I suggest you camp in your driveway for a weekend to see what your power needs are. Use a multi-meter to see what things are drawing.

Edit: Here's what I have. I built a frame for them out of PVC pipe, and mount them with bungie ball ties. The frame breaks down for packing.

$190 XINPUGUANG Solar Panel 12V 200W System Kit 100W Flexible Solar Panel Monocrystalline Battery Charger with Extension Cable 20A Charge Controller Power for RV Boat Cabin Car Trailer(200W-1)

https://www.amazon.com/XINPUGUANG-M...rger+kit&qid=1614962676&s=lawn-garden&sr=1-10

 

There have been several responses, but the concept of fusing is actually simple, though it may take some doing to get your totals.

As @tvpierce stated in the first response, the fuse is there to protect the wire. And all downstream wires/devices ought to be of smaller gauge/ampacity than any upstream wires. So, since you are using 6 awg for the primary connection, that should be fused at its capacity (75A) if you will be using that capacity. If your max expected load is significantly less than that, you can fuse it about 10-20% higher than that expected load. THEN, to protect the smaller wires leading to each load, you ought to fuse those wires depending on their rating.

Again, simple concept, but gathering all the info on your devices can be tedious. The wire ampacities can be googled so that info is pretty easy to find.

 

I assume you intend to use most of the power at the back of the truck. So I'd do as @Bakershack suggested and run your 6awg wire (protected by the 75A fuse) to the rear of the truck, and connect it to a fuse block. Then you can run whatever accessories you need off that and have each circuit protected by a fuse.
Where do you plan on mounting the battery?
As I said earlier, ditch the electric grill and water heater. A single use of one of those will consume enough power to deplete a fully charged battery.
So with those two appliances out of the way, you're left with USB charging, and lights. Both of which will be handled at the 12 volt level, so there's no need for an inverter. Assuming your lighting will be LED (there's no reason it shouldn't be), your power needs are very modest.
You mention the possibility of a fridge/cooler. If you're thinking an Iceco or similar, that's going to be about a $500 item and will consume about 60 watts when the compressor is running (but it doesn't run all the time, just like your fridge at home). Don't bother with the $100 "chiller" coolers -- they're about as worthless as tits on a bull.
As far as battery brand: any deep cycle RV/Marine battery will be fine.

 

2000 watt inverter will draw more than 30 amps. 2000 watts /12 volts=166.6 amps and at 14 volts = 142.8 amps. Many inverters will have a surge/startup capability higher than the continuous rated output. Also, you’ll need to account for the length of wire run when determining the wire gauge.

 

The watt rating of an inverter is for the secondary/AC output. So it would be 2000 watts/110 volts = 18.2 amps. But that still doesn't tell you how many DC amps the inverter draws on the primary/input side. I don't know that there's a reliable formula for that because of the variables in inverter efficiency. But the 30A fuse at least gives you a ballpark figure.

 

Ok, boss. You put 30 amps on that inverter and let me know how it works out for ya.

 

Watts is a unit of power and doesn't change significantly from the input side to the output side. Of course the inverter is not perfectly efficient so 2000W used by the inverter does not translate to a full 2000W available for use on the 120V side. Plus, unless you have a (very expensive) high efficiency, true sine wave inverter, you will lose some power due to poor power factor (pf) losses. But again, FUSE BASED ON THE WIRE SIZE, NOT the inverter. The primary reason for a fuse is to prevent failure of the wire due to overcurrent. This failure can be very difficult to find, at least, and could cause a fire in the worst case.

 

The fuse must be sized for both. The wire gauge has to be selected for the current required to run the inverter and on the length of that wire. You can not put a 30 amp fuse on a 12 gauge wire ran 14 feet to a 2000 watt inverter. IT WILL FAIL.

 

You're right. I was going by what @dropindeuces stated about the unit having a 30A fuse.

Doing the math, that's a lot of draw on the battery. What's the 30A fuse for then?

 

My guess it would be the manufacturer’s attempt of protecting the A/C side of the current versus using a breaker. But I’m not familiar with that brand inverter, so I’m only speculating.

 

@tvpierce Sorry I've been busy the last couple of days. Yeah I looked into that solar panel you posted I think I will be picking that up. I dont know if I mentioned it but Im planning on making the second battery completely removable so I just disconnect it when I get to where I want to go, and while Im traveling I just hook it back up via the anderson power plug so it can charge. I have two fuses which I will install on both ends. And I actually ran across this fridge while surfing youtube, tell me what you guys think;

$310 BougeRV 12V Portable Refrigerator Fridge Freezer Portable Car Fridge 53 Quart Electric Cooler12V/24V DC 110~240 V AC for RV Truck Jeep Pickup SUV Van Boat Camping Tailgating Road Trip Outdoor Travel

https://www.amazon.com/gp/product/B0869NCSNH/ref=ox_sc_act_title_1?smid=AWA4NAV5T95KM

The 30A fuse you guys are referring to is a internal fuse/breaker I think because I dont see one on the outside. Hell after hearing from everyone I might just ditch the inverter or just carry it along as a "just in case" item.

 

Wow, those fridge/coolers have really come down in price. I think it was a year ago I was looking at them (maybe it was two years... I'm not sure) they were a little over $500.

 

The inverter install is no big deal. 0 gauge wire with a 200 amp ANL fuse within 18” of the battery. I’ve installed thousands of them (I’ve got 12 inverter installs scheduled one day this week). I run the ground directly to the battery as well. Give it room to circulate air to keep cool.

 

Where are you locating your second battery? I’m installing a second one myself passenger side under hood but it’s getting a little more difficult, but doable. Just seeing if you had some tips.

 

Lol yeah man, these have gotten alot cheaper apparently but some higher brands are still close to 1K$ or more.

Same here, I decided to just run a ground cable straight from my main battery because its just a much more solid ground. Do you work at one of those off road shops? Just curious.

I donno if this was directed towards me but Im planning on making mine completely removable. When Im just driving my truck around town the battery will be in my barn just collecting dust. And when Im gonna head out into the sticks I just grab the box, plug it in the the bed, start her up and off I go. I donno if I can offer any good advice as this is my first truck so Im learning as I go, but I decided to have my second in my bed so its easily removable and will be strapped down in the bed until needed. The only advice I think I can offer is plan out how you are going to wire everything up and drill holes to run wires because I didnt LOL, measure twice drill/cut once because my truck almost started to look like swiss cheese LOL.

 

I own a company that does fleet communications work.

 

Oh ok.