2017 Roadtrek Simplicity wire gauge for battery

[GJorey]

Anyone know what gauge the wire from the house battery to the inverter is? Replacing battery with a pair of Battle borns and want to reuse the wires that go under to the battery to hook up the new batteries. Need AGM gauge size to order new connectors.

Thanks

[avanti]

Wire almost always has its specification printed every few feet on the outside of the insulation. You have to look very carefully, but if you read the numbers and do a quick internet search, you will know exactly what you have.

[rowiebowie]

Originally Posted by GJorey

Anyone know what gauge the wire from the house battery to the inverter is? Replacing battery with a pair of Battle borns and want to reuse the wires that go under to the battery to hook up the new batteries. Need AGM gauge size to order new connectors.

Thanks

Welcome to the forum GJorey!

All cables I've seen have a gauge embossed on the cover. As Avanti said, you may have to have just the right light an angle to read it, but it should be there on your existing wires.

Otherwise, to determine the gauge you want to replace them with (if you even need to) will be calculated by length of wires and power (amps) they need to handle.

When I did my Lithium battery & 3000W inverter upgrade, I initially used 4 ga. wires. The reason? It was what was originally used in my van, my runs were about 1/4th the original length, and it was all I could source locally before we took a trip. Of course, with the intention of running the microwave at about twice the old inverter capacity, my intent was always to upgrade the wire gauge.

However, for the few months with the 4 ga. wires (max 4' length) the wires never got warm. The only time I felt the inverter positive wire getting mildly warm was when I was load testing by running the batteries down using a 1600w heat gun for over 15 minutes. They never got warm just using the 1200w microwave (rated as a 700w model) for 3-5 minute periods.

The above being said, I went overboard and rewired with very thick 4/0 gauge copper welding wire cables which were truly overkill. When I ordered my cables from ebay acdcwireandsupply https://www.ebay.com/itm/4-0-AWG-GAU...72.m2749.l2649 (who are great by the way) I got the largest gauge wire available because it was only incrementally more expensive than the next smaller gauge. However, it is heavy gauge and harder to work with. If I did it again, I'd use 2/0 or 0/0 wire and not ever worry about it.

[mkguitar]

if 2 x 12 volt, same gauge wire-


if you are replacing with 2 x 6 volt batteries, then the gauge needs to be larger for the jumper between the 2 batteries as 1/2 volts means 2x amps



mike

[DWorrell3]

Originally Posted by GJorey

Anyone know what gauge the wire from the house battery to the inverter is? Replacing battery with a pair of Battle borns and want to reuse the wires that go under to the battery to hook up the new batteries. Need AGM gauge size to order new connectors.

Thanks

I replaced my 750w inverter with a 1250w job and I had to use #2, #4 were there for the 750W inverter. Big wires. Don't forget the frame is the ground and only a wire from the inverter to the frame is required for that. JDW

[Nic7320]

Originally Posted by mkguitar

if 2 x 12 volt, same gauge wire-

if you are replacing with 2 x 6 volt batteries, then the gauge needs to be larger for the jumper between the 2 batteries as 1/2 volts means 2x amps

mike

No, you're misapplying a basic rule.. Current is the same in all three wires and in both batteries in a series connected string. And since the wire is usually very short between two 6 volt batteries, it can actually be smaller, since the IR drop is small. But most people use the same gauge anyway.

Now if you were powering a 6 volt load from a 6 volt battery, then the current would be double compared to a 12 volt system for the same power. That's where that idea comes from.

[Yoshimura]

Cables are 4/0 with 300A fuse on my 2018 Roadtrek Simplicity.

You don't have a underwood generator, right?

[GJorey]

Just finished installing Battleborns. Wow what a difference from the single under carriage battery. Hooked lithiums in parallel using 4/0 cable with Blue Sea System's 300 amp shut off switch. Under hood generator charges them nicely. With the old system just running the fridge over night was taxing on the battery.

Thanks everyone for suggestions.

[booster]

Originally Posted by GJorey

Just finished installing Battleborns. Wow what a difference from the single under carriage battery. Hooked lithiums in parallel using 4/0 cable with Blue Sea System's 300 amp shut off switch. Under hood generator charges them nicely. With the old system just running the fridge over night was taxing on the battery.

Thanks everyone for suggestions.

Be aware that with a battery cutoff switch and an underhood generator, you stand a chance of spiking the voltage if the engine is running and someone shuts off the battery shutoff switch, same thing with the solar if you are in the sun when it shut off, or you drive out of the garage into the sun from a dark garage with the cutoff shut off.



With lithiums it is likely best for them to shut off the charging once the batteries are filled, so you would want to shut off the field of alternator first before shutting off the connection to the battery, if you have that on a switch.

[Yoshimura]

Originally Posted by GJorey

Just finished installing Battleborns. Wow what a difference from the single under carriage battery. Hooked lithiums in parallel using 4/0 cable with Blue Sea System's 300 amp shut off switch. Under hood generator charges them nicely. With the old system just running the fridge over night was taxing on the battery.

Thanks everyone for suggestions.

Did you kept the AGM battery? Also did you added a Balmar external regulator to your underwood generator?

[Yoshimura]

Originally Posted by booster

Be aware that with a battery cutoff switch and an underhood generator, you stand a chance of spiking the voltage if the engine is running and someone shuts off the battery shutoff switch

Furthermore, the Batlleborns batteries have an internal BMS that automatically disconnect the battery when it's full. If this happened while the engine is running, the generator internal diodes will burn out. I can't wait to see how he's preventing this.