Designing new battery + inverter setup/system

[garbonz]

Another thing about wire gauge. The conventional recommendations are based on voltage drop between the batteries and inverter at 3% voltage drop which is needed for lead acid battery chemistry.

Your Lithium’s batteries don’t need the 3% rule and work fine at a 10% drop due to their higher resting voltage and minuscule voltage drop. 4 gaugewire is fine for all but the larger inverters and highest loads.

[ScottBrownstein]

Originally Posted by ependydad

Scott, how are you figuring out the amps needed? And I assume the wire size is a direct correlation from them (and run length)?

Here is a spreadsheet that I built a while ago to take the magic out of wire sizing. The difference between the green and red values is merely the NEC rated ampacity of the cable. HOWEVER, you should also take into consideration what the duty cycle is of the max amperage load.

I added the column for "equivalent 6 W LED lights" and you can see that the difference between #4 and #6 conductors is equivalent to leaving 2 more ceiling lights on in the coach. You can see the absurdity of using the really big stuff as the difference between 4/0 and 1/0 is a single LED lighting fixture!!!

Personally I run a 1500 watt Xantrex, 22 feet from the battery bank on #6, since that is also the cable between my 70 amp converter and the bank on my Georgetown 335DS! Never had a problem and it is fused at 100 amps.

If you are really serioius about lithium you do need to be careful about shorts since the internal resistance is so low you can easily pump tremendous currents without knowing it.

[ependydad]

Ok, I've revised the diagram with a couple of updates:

1. I noticed my charger was bypassing the battery disconnect and worse was also bypassing the shunt so it wouldn't be counted.
2. I tried to add clarity to the 15amp transfer switches

Click for full-size

As for wiring and charging- everything will be within a couple of feet of each other. I actually will be turning off the camper's current converter and will be installing a second one in the same bay with all of the other equipment. (I brought the converter/charger from my old rig but it doesn't fit the new one.)

As for lithium, the Battle Born drop-ins are supposed to be pretty self-aware and self-protecting. But, I definitely want to try and be as safe as possible with them.

[ependydad]

I spent some time today to map which circuit breakers control which outlets. Turns out, I can make most of them "hot" with the inverter by putting automatic transfer switches on just 2 breakers (GFI and GEN).

Even better, I learned I have a non-contract tester. Make it short work to test outlets.

[rk06382]

Originally Posted by ependydad

Ok, I've revised the diagram with a couple of updates:

1. I noticed my charger was bypassing the battery disconnect and worse was also bypassing the shunt so it wouldn't be counted.
2. I tried to add clarity to the 15amp transfer switches

.....

As for wiring and charging- everything will be within a couple of feet of each other. I actually will be turning off the camper's current converter and will be installing a second one in the same bay with all of the other equipment. (I brought the converter/charger from my old rig but it doesn't fit the new one.)

As for lithium, the Battle Born drop-ins are supposed to be pretty self-aware and self-protecting. But, I definitely want to try and be as safe as possible with them.

I like your design. I thought of going that route but I decided on going with a Inverter/Charger.

I am installing a Samlex Evolution EVO-2212. It is a hardwired 2200 Watt Pure Sine Inverter/Charger.

The main feature of the EVO-2212 is has a connections for both Shore & Generator.

I also purchased four 100ah Battle Born Batteries & Six 100 Watt Solar Panels.

Good luck with your install, Please post updates.

[aeblank]

Originally Posted by ScottBrownstein

Personally I run a 1500 watt Xantrex, 22 feet from the battery bank on #6, since that is also the cable between my 70 amp converter and the bank on my Georgetown 335DS! Never had a problem and it is fused at 100 amps.

1500W on #6?
I don't disagree people go a little nuts on wire size, but dang.

My (planned) 2000W inverter should be like 185 amps (with 100% inverter efficiency). I don't know the real wire length yet, but it's probably nearly 20' (each way). I was planning on 3/0 fused at 200A. Should be 3% or a bit less voltage loss.

I'd think you're in the 17%+ voltage loss at full load. something like 138A.

I'm not sure when full load would ever happen for either of us, but it should be considered, anyway. Am I missing something? One thing too, what voltage do we want to call all of this? 12? 12.5? 13? It changes the math quite a bit when dealing with small percentages.

Not trying to derail the OP, but I couldn't quite let it go.

[ependydad]

Originally Posted by ScottBrownstein

Here is a spreadsheet that I built a while ago to take the magic out of wire sizing. The difference between the green and red values is merely the NEC rated ampacity of the cable. HOWEVER, you should also take into consideration what the duty cycle is of the max amperage load.

Looks like you might have attached a PDF export of the Excel file. Can you send the actual Excel?

[1A Camper]

The 4 fuses that are in the neg side of batteries, make them circuit breaker so you have a switch to turn off battery. I have had problem with connector on high amp fuses. If using fuses do not go cheap on the holder/connectors.
Seeing fuses and disconnect on the neg side of batteries, I can not think of any reason that would be bad. I would expect them to be on Positive side.

[rk06382]

Originally Posted by aeblank

1500W on #6?
I don't disagree people go a little nuts on wire size, but dang.

My (planned) 2000W inverter should be like 185 amps (with 100% inverter efficiency). I don't know the real wire length yet, but it's probably nearly 20' (each way). I was planning on 3/0 fused at 200A. Should be 3% or a bit less voltage loss.

I'd think you're in the 17%+ voltage loss at full load. something like 138A.

I'm not sure when full load would ever happen for either of us, but it should be considered, anyway. Am I missing something? One thing too, what voltage do we want to call all of this? 12? 12.5? 13? It changes the math quite a bit when dealing with small percentages.

Not trying to derail the OP, but I couldn't quite let it go.

You need to size the cable to the surge amps. My Samalex 2200 has a maximum continuous DC input current of 266A. That means 4/0, also twist or shield the cables to reduced interference.

[ScottBrownstein]

Originally Posted by ependydad

Looks like you might have attached a PDF export of the Excel file. Can you send the actual Excel?

Sure. Here it is. When you download it, change the extension back to .xlsx since they won't allow xlsx uploads.

Fill in the amperage, I use 12.5 for voltage and the round trip distance. It will show you the losses at that current. As I said, the colors are just for wiring that is within the NEC code ampacity. Inverters don't draw continuously, so you can go slightly beyond rated ampacity. NEC allows this for welders since they do not normally run at 100 duty factor (in fact most cannot.) As I said, I have a 1500 watt inverter running on #8 with at least a 30 to 45 foot round trip distance. Never had a problem, even when someone put a 2000 watt coffee maker on the circuit. The inverter just shut down for overcurrent and then came right back when the load was removed. Depends on what you are planning to run on the inverter, I never have hit much more than 750 watts, and as I said, I am fused for 100 amps. I have also never had it alarm for undervoltage either.

[ScottBrownstein]

Originally Posted by aeblank

1500W on #6?
I don't disagree people go a little nuts on wire size, but dang.
...Not trying to derail the OP, but I couldn't quite let it go.

Of course you are right. I have the inverter installed in the rear power bay of my 335DS which has a PD 70 amp converter going to the batteries. In reality it is probably a 30 foot round trip. I just piggy backed to the lugs on the output of the PD as there is an extra set. At some point I would like to up the whole circuit, since my inverter is not the problem, it steals almost .75 volts when I am in boost mode and that lengthens the genny runs. Making it bigger would fix both problems, but in actuality, there never have been serious problems so I haven't gotten around to it. Here is what it does to me going from 66% SOC back to 88% with a 4 hour boost from the Charge Wizard pendant on the 9270.

Big conductors are cool, but I don't own stock in a copper mine. When I get to it, I would up the feed from #8 to maybe #4 or #2, and use the chassis all the way as a return.

[rk06382]

Originally Posted by ScottBrownstein

Of course you are right. I have the inverter installed in the rear power bay of my 335DS which has a PD 70 amp converter going to the batteries. In reality it is probably a 30 foot round trip. I just piggy backed to the lugs on the output of the PD as there is an extra set. At some point I would like to up the whole circuit, since my inverter is not the problem, it steals almost .75 volts when I am in boost mode and that lengthens the genny runs. Making it bigger would fix both problems, but in actuality, there never have been serious problems so I haven't gotten around to it. Here is what it does to me going from 66% SOC back to 88% with a 4 hour boost from the Charge Wizard pendant on the 9270.

Big conductors are cool, but I don't own stock in a copper mine. When I get to it, I would up the feed from #8 to maybe #4 or #2, and use the chassis all the way as a return.

Do not use your chassis for return. You will get EMI noise on your electronics.

[ScottBrownstein]

Perhaps, although I, off hand, don't know why it would be any worse. I am open to having it explained. All autos use the chassis as a return and FR eventually does since the house battery bank and the chassis battery both connect directly to the chassis and only the chassis. I never traced it out but I think FR grounds the negative to the chassis in the DC fuse panel.

[rk06382]

Originally Posted by ScottBrownstein

Perhaps, although I, off hand, don't know why it would be any worse. I am open to having it explained. All autos use the chassis as a return and FR eventually does since the house battery bank and the chassis battery both connect directly to the chassis and only the chassis. I never traced it out but I think FR grounds the negative to the chassis in the DC fuse panel.

Low power led lights can use the chassis but as our RVs have wood panels, there is a 12VDC ground wire on everything installed by Forest River. I am install my inverter in the bay next to the batteries to keep the cables to under ten foot.
See my post: Expanding compartment space for 2200 Watt Inverter/Charger

EMI FAQ from Samlex website:
FAQ: Inverters - Limiting Electromagnetic Interference

[ScottBrownstein]

already followed and read it. Nice design.

I have two inverters in my coach, both Xantrex, both with cases grounded to the chassis (like here is a ground wire...guess it has to go to ground!) I have never, ever experienced any EMI on audio, video or digital channels, and I have spent a lot of hours chasing EMI before everything went digital. My cables are not shielded (with the exception of coaxial ones) they are not twisted (with the exception of my Trimetric sense leads.) No EMI...ever.

I think Samlex is being a little overprotective...I doubt that anyone has shielded DC cables to their inverters and I doubt that they are twisted either.

Sure inverters, by their nature, are noisy beasts, but Xantrex is quiet as a mouse in the RF range based on my experience.

I installed my second inverter in my rear power bay...because it was close to the power converter feed, which I tapped, and just below the main AC panel, which I also tapped. Solid install that has been working well for me for years now. I could have installed it in a nice storage bay adjacent to the batteries and had a 3 or 4 foot run. But I didn't want to trap the heat in that small compartment and I didn't want to clutter it up either. I probably might have drawn 800 watts a couple of times, but generally it runs below .25 KW.

You can't believe everything you read, or at least take it as gospel. Sure shielded cables are better, twisted 4/0 even better...but how much better is the issue.

[rk06382]

Originally Posted by ScottBrownstein

already followed and read it. Nice design.

I have two inverters in my coach, both Xantrex, both with cases grounded to the chassis (like here is a ground wire...guess it has to go to ground!) I have never, ever experienced any EMI on audio, video or digital channels, and I have spent a lot of hours chasing EMI before everything went digital. My cables are not shielded (with the exception of coaxial ones) they are not twisted (with the exception of my Trimetric sense leads.) No EMI...ever.

I think Samlex is being a little overprotective...I doubt that anyone has shielded DC cables to their inverters and I doubt that they are twisted either.

Sure inverters, by their nature, are noisy beasts, but Xantrex is quiet as a mouse in the RF range based on my experience.

I installed my second inverter in my rear power bay...because it was close to the power converter feed, which I tapped, and just below the main AC panel, which I also tapped. Solid install that has been working well for me for years now. I could have installed it in a nice storage bay adjacent to the batteries and had a 3 or 4 foot run. But I didn't want to trap the heat in that small compartment and I didn't want to clutter it up either. I probably might have drawn 800 watts a couple of times, but generally it runs below .25 KW.

You can't believe everything you read, or at least take it as gospel. Sure shielded cables are better, twisted 4/0 even better...but how much better is the issue.

Your right, It is a gray area. My son complains of the noise that I can not hear. It must be my gray hair. (or ringing in my ears)

I know the 6 AWG wire on the converter/charger goes straight to the DC power panel in my FR3. Since I am installing an Inverter/charger I plan to use the 6 AWG wire for a solar charge controller.

[ScottBrownstein]

I considered that. However, that run goes through the battery disconnect switch and that is not ideal for a solar charge controller. For some reason FR runs their converters that way as well and I guess it is because they seem to go to the panel first and then to the batteries.

[rk06382]

Originally Posted by ScottBrownstein

I considered that. However, that run goes through the battery disconnect switch and that is not ideal for a solar charge controller. For some reason FR runs their converters that way as well and I guess it is because they seem to go to the panel first and then to the batteries.

I'm sorry, I forgot to mention that it would be the 2nd removable charge controller connected to a portable 200 watt solar panel. Primary charge controller with 600 Watts on roof will connect straight to the Samlex EVO-2212 inverter.

A quick connect will be on the end of the 6 AWG wires where the converter is. Amazon: Orion Motor Tech 6-8 Gauge Battery Quick Connect/Disconnect Wire Harness Plug Kit

[ependydad]

I've posted about the battery disconnect being on the positive or the negative side and got a lot of good information (often times conflicting- but hey, that's what makes things fun).

I had also gotten a suggestion for using circuit breakers vs. fuses for the battery isolation. Seems like it would be easier than futzing with fuses.



Still need to sort out fuse/circuit breaker sizing.

And of course, start buying stuff. Amazon is going to love me.

[1A Camper]

If it was me
The 4 circuit breaker change to switches, 80/100 amps breaker going to be expensive, that what the converter/charger will need.
The catastrophic fuse change to 40 to 80 amp and add another for the converter/charger that would be 120 to 180 amps.