Review/critique of planned battery/inverter system?

[ependydad]

Before we traded the old rig, I yanked out the batteries, battery monitor, inverter, and related accouterments (battery disconnect, catastrophic fuse, and circuit breaker).

The old setup was fairly simple:

• wired 4 batteries in parallel
  
• added the battery monitor + inverter
  
• and tied into the camper's 12v system
  

To use the inverter, I would run an extension cord and backfeed the camper by plugging it into the shore power receptacle (with an adapter).


The new camper has a built-in generator and an automatic transfer switch. I have a few goals in mind with the new setup:

1. get rid of the hokey extension cord + backfeeding of camper
   
2. be able to provide power to most outlets in the camper
   
3. better protect each individual battery
   
4. be able to isolate down to a single battery (for yearly charge maintenance)
   
5. provide an upgrade path for the future:
   
   
   
   • adding solar charging
     
   • adding a larger inverter
     
   • make it easier to add additional 12v loads (TPMS repeater, basement lights, and USB outlets to the living room slide are on my immediate "to do" list)
     
   • adding a subpanel for inverted vs. not inverted breakers
     
   
   

The idea is that I can parallel the batteries using bussbars for positive and negative. This will aid in better charging of each battery. I'll put a fuse onto each battery in order to protect each one and to be able to pull the fuses in order to isolate individual batteries.

I'll use either the Xantrex 15amp Automatic Transfer Switches or the KISAE 15amp Automatic Transfer switches.

For the future 12v loads, I'll introduce a fuse block that I'll be able to add and protect new 12v needs.


Click for full-size

My specific questions:

1. are there specific recommendations you would make with all of this design?
   
   
2. for the battery fuses, how many amps should they be?
   
   
3. I previously opted for 1/0 between the batteries, 2/0 between the rest of the components, and 2awg to the inverter (just because it came w/ the inverter). Are these wire sizes sufficient for now and the future?
   

[ependydad]

phemens wrote:
Better if all batteries feed to bussbar with equal length cables on pos and neg.
For the combined inverter charger deals, I’m more a fan of keeping the components separate. If one part fails you are stuck replacing the entire unit. Also easier to troubleshoot if you have an issue. I am a big fan of the Victron monitors and Bluetooth app!

Definitely plan on keeping the bussbar cables in equal lengths.

I have mixed feelings on the combo units- exactly for the reason you stated.

And yes, I'm in LOVE with my Victron BMV w/ bluetooth. I like their stuff and like the idea of keeping everything under one maker for integration and simplicity.

[phemens]

Better if all batteries feed to bussbar with equal length cables on pos and neg.
For the combined inverter charger deals, I’m more a fan of keeping the components separate. If one part fails you are stuck replacing the entire unit. Also easier to troubleshoot if you have an issue. I am a big fan of the Victron monitors and Bluetooth app!

[ependydad]

Rbertalotto wrote:
Balance batteries.....I thought you would connect positive to positive and negative to negative and then take positive from top battery and negative from bottom battery

That is the common way of doing it. But, there is another way of tackling it- positive to a bussbar and negative to a bussbar and then the load goes to the bussbars (so it's split across all of the batteries equally).

If you read the link that pianotuna post, it explains it much better than I can.

[Rbertalotto]

Balance batteries.....I thought you would connect positive to positive and negative to negative and then take positive from top battery and negative from bottom battery

[ependydad]

time2roll wrote:

ependydad wrote:
get rid of the hokey extension cord + backfeeding of camper

That is not back feeding. Back feeding generally involves a cord with a male plug at each end. aka dead man's cord or suicide cord.

Plan looks generally good.

I agree on larger inverter, say 2000 watts, to run any large item that plugs into a normal outlet. (one at a time) Microwave can draw 170 amps BTW. Maybe a little less amps on lithium as voltage sag should be less.

Your transfer switches may need some work. You need switches rated for the full generator power. As shown the generator power goes through a 15 amp switch. Are there two breakers on the generator? What is the rating(s)?

Also the inverter needs to be wired so it does not feed the converter. You can put the 15 amp transfer switches on the branch circuits (outlets only) or do the subpanel to break out inverter vs non-inverter circuits.

Thanks for the clarification on backfeeding. That's what I get for using terms that I don't entirely understand. :B

I ran with this 1000W inverter for a while and understand its limitations. I wouldn't mind a 2000 or 3000W inverter, but I'm thinking about a major upgrade down the road. But, I'm really thinking about one of the Victron solar charger/inverter/charger combo units. We'll see, though.

The transfer switches are misleading on this document. The Xantrex or KISAE 15amp switches are designed to control just a single breaker.

The generator and shore power ATS is already there and is rated for the 50amp service (split phase, blah, blah, terms I don't wholly understand 🙂 ) that the rig already wired for. Nothing changes between that and the camper's distribution box/circuit breakers.

What will change is that each of the breakers (up to 2) that I want supported by the inverter will be wired to the little mini automatic transfer switches.

The subpanel is a future plan, but I'm not ready to go down that road yet. When I get the bigger inverter, I'll definitely do it.

[time2roll]

ependydad wrote:
get rid of the hokey extension cord + backfeeding of camper

That is not back feeding. Back feeding generally involves a cord with a male plug at each end. aka dead man's cord or suicide cord.

Plan looks generally good.

I agree on larger inverter, say 2000 watts, to run any large item that plugs into a normal outlet. (one at a time) Microwave can draw 170 amps BTW. Maybe a little less amps on lithium as voltage sag should be less.

Your transfer switches may need some work. You need switches rated for the full generator power. As shown the generator power goes through a 15 amp switch. Are there two breakers on the generator? What is the rating(s)?

Also the inverter needs to be wired so it does not feed the converter. You can put the 15 amp transfer switches on the branch circuits (outlets only) or do the subpanel to break out inverter vs non-inverter circuits.

[ependydad]

phemens wrote:
How far is the inverter from the battery bank? That will dictate the gauge you should use. For reference, my 2000w inverter is about 3 feet from my bank, and I use 0000. I use 00 to interconnect everything else.

Should be about 3'. Same with the converter/charger.

[ependydad]

pianotuna wrote:
Your bank is not balanced.

Have a look here:

http://www.smartgauge.co.uk/batt_con.html

I use method #3

Don, thanks for sharing that link. I had seen it before but couldn't find it when I went to make this diagram. That said, I tried to reproduce method #3 from memory and looking again, seems like I did.

Would you mind taking a closer look? Is there something specific in my diagram that you think I've missed?

[time2roll]

pianotuna wrote:
Your bank is not balanced.

Diagram shows equal length wire to a bus bar. Looks balanced to me.

[phemens]

How far is the inverter from the battery bank? That will dictate the gauge you should use. For reference, my 2000w inverter is about 3 feet from my bank, and I use 0000. I use 00 to interconnect everything else.
Pianotuna, maybe I'm missing something, but his wiring diagram for the batteries lines up with method 3 on that website?

[Lwiddis]

All this and still not charging by solar? Interesting.

[pianotuna]

Your bank is not balanced.

Have a look here:

http://www.smartgauge.co.uk/batt_con.html

I use method #3