Voltage drop on inverter

BFL13 wrote:
So in amongst all that, how do you shut off the Li bank at home at 80% SOC, and run on just the converter for 12v? Does your co-pilot have to read you the check-off list?

Lol, no checklist required. The battery mfg confirmed that it's fine to keep the SOC above 80% (even at 100%) for a few weeks at a time. Right now when at home I have the charger set to kick in at 12.8V (which will almost never happen), and the solar controllers are kept on. The RV is stored in a pretty shaded area, so the batteries top up during the day but not fully and at night the parasitic draw on 12V (I keep extra 12v accessories on to help out) draws them down enough to exercise them properly. While camping that's not an issue since we regularly draw down to ~ 80% overnight.

Use cable protection sheathing between the battery post and fuse protector. You can put the fuse close to the battery if lithium or
AGM batteries are used. It is in a word foolish to place ANYTHING near a flooded battery.

There are various material SPIRAL WRAP products to protect cables. Slitted loom cover is virtually useless. Search for spiral NYLON wrap. That material adds another dimension of safety to properly routed heavy cabling. To demonstrate the security of nylon cable wrap I used to use a sample length, placed on the ground then struck several times with a splitting maul. It would border on the ridiculous to state such a test is inconclusive.

Place protective devices well distant from corrosive battery fumes.

Ensure the spiral wrap is not cheap Chinese plastic.



I've used thousands of feet of nylon spiral wrap. It is scrape and rub proof even on caterpillar tractors if routed correctly. Nylon is tough stuff.

So in amongst all that, how do you shut off the Li bank at home at 80% SOC, and run on just the converter for 12v? Does your co-pilot have to read you the check-off list?

BFL13 wrote:


I still don't understand why he wants the pos and neg links to the batteries to be equal. I get that all the pos links should be equal to each other and all the neg links be equal to each other. IMO the pos and negs do not need to be equal, since it is a circuit.

You are correct.

His method is less wordsmithing. And method 4 would be even more involved explanation.

I don't think I'd have room for all that anyways :) My storage bay is already pretty cramped with all h heavy gauge wiring as it is.
The fuse off the battery bus would be a couple of inches max, no worry there.
I can put the battery cut-off on either pos. or neg., I was always 'told' to put it on the positive side, but the possibility of shorting pos. battery to frame wasn't something I had considered (I do have battery post covers on all connections).

CA Traveler wrote:
Well I can't remember any post of someone actually fusing all parallel batteries. More danger I'm sure walking on my street with no sidewalk.

Theory vs practice! :)

Well I can't remember any post of someone actually fusing all parallel batteries. More danger I'm sure walking on my street with no sidewalk.

Itinerant1 wrote:
BLF13 is that site talking specifically to a lfp dropin battery. You realize that within each of his drop in batteries there is bms that is cell balancing and if the cells drift outside their lvd/hvd it will shut his batteries down.

No, it was about flooded batts.

Related? Is that rule for the battery fuse to be no more than 18" from the battery on the pos wire.

I was told at a car audio shop (which had big enough ANLs that I was looking for) that this rule came from car crashes. The battery can short and a fire start in the wiring to the audio amplifier (plus the other wires) back in the car somewhere. With the fuse there, only the 18" wire is not protected.

Here's my switch, battery buss bar not needed for balanced connection. AGM batteries so no concern about the shunt location.


Click For Full-Size Image

Based on the diagram I'd make 2 changes:

1. Change the wiring so that there is a maximum of 2 wires on any battery buss bolt.

2. Move the cutoff switch to the negative buss. When it's off then a short (like a wrench) from any positive post or wire to ground will not cause a problem.