12V - Solar - Inverter Set-Up 101

[TBS]

I am wanting to build a solar panel system for my econoline. I have a rough idea of what I need, but was hoping someone could help me fill in the blanks.

My rig - 97 7.3 Diesel E-350

List of Components: 2000w inverter, 125w solar panel w/ controller(possibly adding another panel later if needed), 2 deep cycle marine batteries.

Questions: With my van already having an aux battery, should I consider using the aux battery as one of the batteries in the solar system. If so, should I think about isolating the solar 12v system from the vehicles primary batt so that I dont have to worry about draining all battery power while using appliances at night? Would I need an extra component in the mix to do this?

It seems like it would be beneficial if I could integrate the two systems, so that I could charge the batteries for the inverter/appliances while on the road or on a cloudy day.

 

[herdnerd]

This thread is a good place to start.

 

[tanglefoot]

That thread has a great method in it.

How is your aux battery currently connected? Is it always connected to the starting battery or is it isolated when the engine is off?

RVs with separate engine/house batteries usually have the two connected via an isolator, that charges the house battery when the engine's running and disconnects it when the engine is off.

Here's one example:

http://www.adventurerv.net/isolator...urce=Froogle&gclid=CIbQmf_VpLUCFe1AMgodrjcAJg

You'll absolutely want to isolate your house batteries from the engine starting battery. Not only are starting batteries not designed to be drawn down significantly, but you want to keep the starting battery fully-charged to get you running when you're ready to drive.

Is your aux battery of deep-cycle design? If so, you may want to include it in your house bank so that you can stick with 3 batteries instead of 4, if you don't need the capacity of 3 house batteries.

Depending on your electrical demand on the solar batteries, you may or may not want to have them connected to the engine. I only have small electrical draw in the camper, so my solar-battery system is not connected to the engine at all. If you have a lot of electrical draw from the camper part, you may need to have the engine help charge while driving. With that large of a panel and two deep cycle batteries in parallel, you may not need to use engine charge unless you do have a lot of electrical loads in the back of the van.

Good luck,

Eric

 

[TBS]

That thread has a great method in it.

How is your aux battery currently connected. Is it always connected to the starting battery or is it isolated when the engine is off?

RVs with separate engine/house batteries usually have the two connected via an isolator, that charges the house battery when the engine's running and disconnects it when the engine is off.

Here's one example:

http://www.adventurerv.net/isolator...urce=Froogle&gclid=CIbQmf_VpLUCFe1AMgodrjcAJg

You'll absolutely want to isolate your house batteries from the engine starting battery. Not only are starting batteries not designed to be drawn down significantly, but you want to keep the starting battery fully-charged to get you running when you're ready to drive.

Is your aux battery of deep-cycle design? If so, you may want to include it in your house bank so that you can stick with 3 batteries instead of 4, if you don't need the capacity of 3 house batteries.

Depending on your electrical demand on the solar batteries, you may or may not want to have them connected to the engine. I only have small electrical draw in the camper, so my solar-battery system is not connected to the engine at all. If you have a lot of electrical draw from the camper part, you may need to have the engine help charge while driving. With that large of a panel and two deep cycle batteries in parallel, you may not need to use engine charge unless you do have a lot of electrical loads in the back of the van.

Good luck,

Eric

What would be the difference between running a swtich like shown in the link herdnerd posted tapped into an ign hot signal, and the isolator you posted?

 

[tanglefoot]

This thread talks about them...

http://www.expeditionportal.com/for...in-a-battery-isolator-versus-starter-solenoid

It sounds like an isolator usually has some voltage drop and current limiting built-in, and is designed for long-term current passage. If you plan to charge dead or nearly dead house batteries, an isolator might help with the shock of suddenly throwing a switch between the batteries. The isolator and solenoid terms are sometimes used synonymously though. Isolators vary in how complex and "smart" they are. A solenoid is always just a switch.

 

[Sheep Shagger]

Personally I wouldn't touch the diode style of isolator. (ie that link and most RV junk). Manual switch or a manual (or automatic) relay is a better solution.

This link explains it better that I can.
http://www.neon-john.com/RV/Electrical/rv_battery_isolation_relays.htm

Solution I went with was an auto relay from Bluesea, as it has all the benefits of an automatic solution, and has a manual overide. so I can start off the house batteries if needed in an emergency.
http://bluesea.com/category/78/79/productline/385

A 200~500 amp relay would do exactly the same job BTW. It just wouldn't be waterproof and wouldn't auto switch if you have solar charging the house and want to use the extra power to trickle charge the starters.

 

[TBS]

Personally I wouldn't touch the diode style of isolator. (ie that link and most RV junk). Manual switch or a manual (or automatic) relay is a better solution.

This link explains it better that I can.
http://www.neon-john.com/RV/Electrical/rv_battery_isolation_relays.htm

Solution I went with was an auto relay from Bluesea, as it has all the benefits of an automatic solution, and has a manual overide. so I can start off the house batteries if needed in an emergency.
http://bluesea.com/category/78/79/productline/385

A 200~500 amp relay would do exactly the same job BTW. It just wouldn't be waterproof and wouldn't auto switch if you have solar charging the house and want to use the extra power to trickle charge the starters.

The blue sea auto switch you posted is perfect. Exactly what I was thinking, but it takes the guess work out of getting the proper relay and puts everything in a nice neat package. I suppose if I really wanted I could hunt down a heavy relay like listed in the tech write up you also posted, and I might do so just to check out the price difference. I'm a bit of a neat freak whe. It comes to electrical though and the bluesea switch is pretty tidy.

Any input on battery selection?

 

[G35Vortec454]

Any input on battery selection?

With the info you provided, I would use 2 golf cart batteries in series, and if the current aux battery box accomodates 2 GC batteries, use GC batteries there too, and connect them all in series-parrallel arrangement. This would be your "house" battery bank. Separate the bank from your engine starting battery, which is hopefully a Group 31 unit, using either an isolator or an ACR.

You did not mention what kind of charger you'll be using to fully charge your batteries, since your 125W panel nor your alternator would not be able to do. You may also want consider having your solar charger charge your engine starting battery, and if so, use the SunsaverDuo controller.

 

[spencyg]

I use an isolator solenoid triggered off the engine run circuit. When the engine is running, the house and starting batteries are connected and are charging. When the engine is off the house bank is automatically isolated. I have an emergency manual switch which can connect the batteries from both banks if the need arises.

I run dual 105Ah deep cycle marine batteries for my house bank which has proven adequate for the most part. I also run a 100W solar panel which is barely adequate. I'm going to get another 100W panel in the spring which should be enough to keep ahead of refrigeration and night time fan usage.

One thing to note is that you'll want to have an upgraded alternator to handle the additional battery load. My van's charging system is grossly inadequate with only a 90A alternator. I intended to upgrade to a 200A unit this spring.

SG

 

[TBS]

With the info you provided, I would use 2 golf cart batteries in series, and if the current aux battery box accomodates 2 GC batteries, use GC batteries there too, and connect them all in series-parrallel arrangement. This would be your "house" battery bank. Separate the bank from your engine starting battery, which is hopefully a Group 31 unit, using either an isolator or an ACR.

You did not mention what kind of charger you'll be using to fully charge your batteries, since your 125W panel nor your alternator would not be able to do. You may also want consider having your solar charger charge your engine starting battery, and if so, use the SunsaverDuo controller.

I have heard mention of people using 6v golf cart batteries in series, but what is the advantage of doing so if any over a deep cycle marine like spencyg mentioned.

Also, I'm not sure as to the output of my alt or how exatly the aux batt is hooked up on the 7.3, but in short term I was starting to think I' just throw in a deep cycle 12v(1 maybe 2) isolated and charge it off the alt for a trip or two. The number of additional batteries I suppose will be determined by how dependent the main batt bank is on its existing aux batt. Do you think the alt will keep up?

 

[G35Vortec454]

I have heard mention of people using 6v golf cart batteries in series, but what is the advantage of doing so if any over a deep cycle marine like spencyg mentioned.

Also, I'm not sure as to the output of my alt or how exatly the aux batt is hooked up on the 7.3, but in short term I was starting to think I' just throw in a deep cycle 12v(1 maybe 2) isolated and charge it off the alt for a trip or two. The number of additional batteries I suppose will be determined by how dependent the main batt bank is on its existing aux batt. Do you think the alt will keep up?

The advantage of using GC batteries is it doubles the AH capacity and also doubles the longevity since they come with thicker (heavier) plates and can tolerate deeper discharges along with higher charge/discharge cycles. With the series parallel arrangement I described youll have 460AH capacity.

If you'll be using close to your 2000W inverter output (like running a 9000btu air conditioner for a couple of hours) your marine batteries will fail prematurely. I'd say you'll need a minimum 160A alternator to bulk charge the GC batteries adequately while driving. For trickle charging, I'd go for at least 240W of solar panels.

Now, if you'd only be using 800W of inverter output, you can probably get by with half of the mentioned equipment capacity.

Remember the top 2 commandments for treating a battery: #1 charge it fully as soon as possible, #2. Do not discharge more than 50%. If you follow these and maintain it well, it will last a very long time.

 

[spencyg]

You might consider also having the large inverter for your heavy loads, and then a much smaller one for daily charging tasks, etc. Inverters have a current draw even when they're not being used. I wouldn't be surprised to see a 2000w inverter drawing an amp or more just sitting there. I run a single 400W inverter tied into the domestic outlets in the van and it draws around 0.25A sitting still. I turn it off whenever I'm not in need of 120V power.

G35 is right on the money with GC batteries. They are very heavy and take up more room than the equivalent deep cycle marine battery, but the cost in size and weight is offset by their tolerance for abuse and their storage capacity. Having more battery than you need is expensive and cumbersome however, so if you don't need 480AH of house bank (and likewise, if you don't need 2000W of inverter power), just don't. "More is better" absolutly doesn't apply here. Have what you need, not 2x what you need.

SG

 

[TBS]

You might consider also having the large inverter for your heavy loads, and then a much smaller one for daily charging tasks, etc. Inverters have a current draw even when they're not being used. I wouldn't be surprised to see a 2000w inverter drawing an amp or more just sitting there. I run a single 400W inverter tied into the domestic outlets in the van and it draws around 0.25A sitting still. I turn it off whenever I'm not in need of 120V power.

G35 is right on the money with GC batteries. They are very heavy and take up more room than the equivalent deep cycle marine battery, but the cost in size and weight is offset by their tolerance for abuse and their storage capacity. Having more battery than you need is expensive and cumbersome however, so if you don't need 480AH of house bank (and likewise, if you don't need 2000W of inverter power), just don't. "More is better" absolutly doesn't apply here. Have what you need, not 2x what you need.

SG

I am inticipating running a small ac unit in the future. Summers here in south TX get hot, and I have my fiance and daughter that have different tolerances than I do when it comes to camping. So if I want to broaden my camping season I'll have to be equipped to keep them comfy. It might seem as though I'm overbuilding, and I might very well be, but I certainly am not a fan of doing things twice.

 

[goneover]

try this web site they are great people and their site has an educational section that cover it all ... www.amsolar.com

 

[spencyg]

If I was running AC I would much sooner spring for a small generator to handle the load than carrying 500lbs of batteries. The honda 2000W units are relatively inexpensive, whisper quiet (the AC unit will make far more noise than the generator), and lightweight. The only time I'd consider carrying the battery capacity and inverter wattage necessary to run AC is if I was doing lots of camping in close proximity to others who might find my generator offensive.