Making changes to existing solar system

[okcnewbie]

It appears that you're going to have a little over 100amp/hrs of useable storage.

That means you probably bought too big of an inverter IMO.

Looking at voltage drop tables and installation instructions I don't see how you're even close with "0" wire. 4/0 minimum.

I went with 1000 watt inverter and occasionally use the microwave on defrost (less than 90 amps). I connect the 30amp plug and power the entire MH with it. Mostly just using for charging stuff and watching the TV.

From what I could see of your existing converter it's pretty old and probably not the greatest thing for your batteries. Keep this in mind though. I bought a progressive replacement converter and almost never use it. My 200 watts of solar keep me charged. I'm more of a weekend end warrior right now though.

[okcnewbie]

Originally Posted by CyrusL

....I can disconnect one of the batteries if for some reason I plan on a lot of inverter usage. but don't want to completely drain the house battery.....

I've never heard of this and it doesn't really make since. You can only discharge to 50 -60 %. If you disconnect one of the batteries you only have 50amp/hrs of storage. I don't think you'll be disconnecting the batteries.

[twinboat]

Keep in mind that the typical AH rating of most batteries is at the 20 Hour rate.

That means 5 amps draw, per 100 AH of capacity to get the rated performance.

With your 2, 100 AH batteries you can draw 10 amps for 20 hours. Once you start going over 20 amps, the AH capacity drops and your batteries are discharging faster.

At the 5 hour rate, you have about an 80 AH battery and that works out to only 17 amp draw, per battery.

[John Hilley]

Your concept is flawed. First the batteries you indicate are true deep cycle batteries not meant for starting the vehicle. You should never count on the starting battery for "house" use. Most manufacturers have a method of charging both batteries from alternator, some even from converter to keep both house and chassis batteries charged. To add reserve capacity you could add a third battery (another house battery) with a switch as you diagram. You could then use the first battery and then switch to the second as a reserve. Some changes would be necessary to your diagram and still not a good way to go. The inverter you show, 3,000 watts is much too large for your application.

[CyrusL]

Originally Posted by John Hilley

Your concept is flawed. First the batteries you indicate are true deep cycle batteries not meant for starting the vehicle. You should never count on the starting battery for "house" use. Most manufacturers have a method of charging both batteries from alternator, some even from converter to keep both house and chassis batteries charged. To add reserve capacity you could add a third battery (another house battery) with a switch as you diagram. You could then use the first battery and then switch to the second as a reserve. Some changes would be necessary to your diagram and still not a good way to go. The inverter you show, 3,000 watts is much too large for your application.

John,

I know it's a bit confusing. These batteries will never be used to start the vehicle. This whole system is separate from the vehicle battery.

[John Hilley]

Originally Posted by CyrusL

John,

I know it's a bit confusing. These batteries will never be used to start the vehicle. This whole system is separate from the vehicle battery.

In that case what you are suggesting will wok, the easy way to do it would be with a Marine 2 Battery switch. Charge by putting switch in "All" position and use by selecting "Battery 1" or "Battery 2" or "Both"

Marine 2 Battery Switch

[twinboat]

Originally Posted by John Hilley

In that case what you are suggesting will wok, the easy way to do it would be with a Marine 2 Battery switch. Charge by putting switch in "All" position and use by selecting "Battery 1" or "Battery 2" or "Both"

Marine 2 Battery Switch

There are a few reasons why using a dual battery switch is a bad idea.

It drains one battery deeper, each cycle, shorting it's life. With 2, together, the cycle should be shallower and increase cycles.

It sits discharged, until you get back to it with the charging source, that should be connected to the battery you are using. Batteries sitting discharged is a sure way to kill them.

Doubling the AH capacity lowers the discharge rate and you will get longer lasting power then discharging each one indivudually. The more amps you draw, the faster it dies.

[John Hilley]

Originally Posted by twinboat

There are a few reasons why using a dual battery switch is a bad idea.

It drains one battery deeper, each cycle, shorting it's life. With 2, together, the cycle should be shallower and increase cycles.

It sits discharged, until you get back to it with the charging source, that should be connected to the battery you are using. Batteries sitting discharged is a sure way to kill them.

Doubling the AH capacity lowers the discharge rate and you will get longer lasting power then discharging each one indivudually. The more amps you draw, the faster it dies.

Although this is all true, a dual battery switch is actually a good idea if

1. You want to be able to manage each battery independently

2. You want to have a reserve emergency battery

3. You want to exclude a battery which has failed

The original post was also concerned about cable length and size. It is necessary to size the cables between the batteries for the length and capacity required for the inverter from the farthest battery to the inverter.

[twinboat]

Originally Posted by John Hilley

Although this is all true, a dual battery switch is actually a good idea if

1. You want to be able to manage each battery independently

2. You want to have a reserve emergency battery

3. You want to exclude a battery which has failed

The original post was also concerned about cable length and size. It is necessary to size the cables between the batteries for the length and capacity required for the inverter from the farthest battery to the inverter.

1, You don't want to manage each battery. You want to build a battery bank, that can handle the load.

2, You have a emergency reserve battery. It starts the engine.

3, I agree. I use 2, A-B switchs in my 8, 6 volt battery bank. I can manage any 6 volt pair.

[baphenatem]

Originally Posted by CyrusL

Ok, here's my proposed setup/changes. I'm attaching a diagram for reference:

• I've ordered two LifeLine GPL-31XT (12-volt AGM) batteries. I plan to replace each of the existing batteries with one of these.
  
• I've replaced the existing cheesy 1000-watt inverter (that had only one working plug) with a new Krieger 3000-watt inverter that I can wire outlets to.
  
• I'm going to run 0-gague wire from the house battery to the other battery that's under the seat of the dinette. I will install a battery cutoff switch on the positive wire between the two.
  

The benefits of this setup are:

• Increased battery life of the house battery (for heater blower, etc).
  
• Both systems will be charged by solar, the generator, or the alternator if the engine is running.
  
• I can disconnect one of the batteries if for some reason I plan on a lot of inverter usage. but don't want to completely drain the house battery.
  

My concerns are:

1. Does it matter that the two batteries are so far away from each other? I'm connecting them with some pretty thick wire.
   
2. Will it be a problem if disconnect the two batteries from each other and then they drain to different levels?
   

Thanks for all your help. I look forward to your responses.

To wire the system as shown will not work as the wire length between the batteries will make it extremely difficult to get both batteries to charge and discharge equally. Is there no way to get both batteries and the inverter installed at the same location, even if you have to extend the wiring to the house system? The disconnect switch makes no sense as you're installing parallel batteries to increase the amp-hours. All that disconnecting one battery does is reduce your overall capacity and lends to decreased battery life via unequal charge/discharge cycles. Also, don't forget the overcurrent protection, for EVERYTHING.

The coffee maker solution looks like this and will save you a lot of money on a bigger inverter!

[baphenatem]

Originally Posted by C.Martin

RV with Tito shows a way to simplify an installation...IMPORTANT!!!! You have to remember to trip the breaker on your charge converter...It's of no use to use your batteries to make 110v just to convert it back to 12v to charge your batteries. Viscous cycle.

"Vicious cycle" you say. It sounds like the concept for the Ronco Camp-O-Matic perpetual battery charging system. Connect your power cord to your inverter and stay in the woods forever!

[CyrusL]

Originally Posted by baphenatem

... Is there no way to get both batteries and the inverter installed at the same location, even if you have to extend the wiring to the house system? .......Also, don't forget the overcurrent protection, for EVERYTHING.

Well, I really really really didn't want to have to move the batteries, but at this point I guess I might have to. It's probably doable, just very inconvenient.

As for the overcurrent protection, I assume you're talking about fuses? The inverter came with a 300A fuse, which I will certainly be installing. I just forgot to put it in the diagram.

Thanks for all the help from everybody who responded.

[Reed Cundiff]

I am holding myself in check with regard to subject "Making changes to current solar system?" But it hurts.
Reed

[baphenatem]

Originally Posted by Reed Cundiff

I am holding myself in check with regard to subject "Making changes to current solar system?" But it hurts.
Reed

Fine job, Old Boy. Fine job!