The batteries need to be the same and need to be charged and discharged together. Getting all the batteries charged properly is the only way to have the full capacity from your battery bank. Any deviation will not allow you to use them as deeply and their life will be shortened. If you split the bank then the ones always being used would get slightly weaker than the ones not being used as much. If the batteries are different, they will charge a bit differently and the whole bank will not get charged properly. Mismatching usage or size is a quick way to turn a 450 amp-hour battery bank into a 400 amp-hour battery bank and eventually a 300 amp-hour battery bank.

The 6V vs 12V is due to normal battery sizes, since the 6V golf cart batteries have thicker plates and thus have better deep cycle performance. It requires 4 plates for 6V and 8 plates for 12V. 8D batteries and others that are physically much larger do not have this problem, the batteries are wide enough to support 8 thick plates.

It sounds like the company is not creative on finding a place to put the batteries or using alternative batteries.  Look for a place to weld a battery cage, move the chassis battery (or batteries).  You could use AGMs, they do not need to be vented and are maintenance free, but are around twice as much.  You could go with lithium batteries, another price jump, but they can be discharged to 80% safely and there is little voltage sag, so 200 amp-hours of lithium will power a microwave.

-- Edited by bjoyce on Sunday 16th of March 2014 10:19:03 AM

Thanks for the replies! I'm going to call them tomorrow and run some of these suggestions by them. I may have to take a drive up there to talk to the mechanics personally if I can't get answers thru the sales staff. I like the idea of the AMG batteries so I will ask about that too.

What manufacturer did you all go with? Do you have the same company for all of the components or did you mix and match?  I'm looking at Zamp Solar and Go Power.

Who should I be looking for to do the install? An automotive electrical person, an electrical engineer, a solar person? Does anyone have any recommendations in New England to do a solar install on an RV? I'm not doing roof panels. Thanks!

Just an observation – Have you noted just how much physical area a 450 watt solar panel system takes?  That is when placed on the ground or wherever for operation it is a fairly large area. So the physical mechanics of storage and setting up such an array could be somewhat challenging.  

In many people’s opinion, 6 volt batteries are a bit better but not enough to lose a lot of sleep over.  But I recommend 6 volt.

You could carry “extra” batteries and connect them but they must be the exact same battery and the connecting cables, all things being equal, need to be the same distance from the charge controller as the installed batteries to insure balanced changing and draw.  However, if you vehicle charges the batteries which are installed in the trailer when you travel then adding batteries when you stop is not a good idea due to the fact the charged level of the installed vs. “portable” batteries won’t be the same.  Will it work?  Yes, but it will shorten the life of all the batteries.  Now, if you don’t move a lot maybe all this doesn’t matter as much.

Here’s the link to Jack’s discussion as Mike suggested.  Get a cup of coffee.  This is technical and solar is technical.

http://www.jackdanmayer.com/rv_electrical_and_solar.htm

Bill

Hey Bill, I'm definitely going South West! As far from cold and snow as I can get. It's been a looooonnnng winter! Bill and Linda, no I haven't really looked into that yet so I will check out the size.  Mike, I have been reading Jack's info and it's a good idea to PM him. Also, great advice to wait, thanks!  I think I may do that as I'm getting any level of confidence that the RV guys where I"m buying it from know anything about solar systems, even though they represent one!

Thanks for all the info and advice, I really appreciate it!

Bill and Larry both make good points....our 3 panels take up a 5' x 10' foot print. Each panel weighs about 69 lbs. The 6 batteries we carry in the front compartment put an additional 450 lbs into the hitch pin. At 75 lbs each they are not portable by any means. Careful patient planning is key and consulting with Jack is a must!

If I may

I use a 230 watt high voltage panel and a 20 amp mppt controller unmounted. There are ups and downs to using a portable, some you can mitigate.

The ups are

A portable can track the sun from before sun up until after sun down, allowing you to collect twice as much as you can with a ridged roof mounted panel of the same size. On a clear summer day we can collect around 200 ah with 230w.

You can take advantage of the sun when you get it. We had many morning sun, afternoon cloud days last year. A mounted system would have had only 3 hours of peak sun at best.

The cost of a portable system is cheaper simply because it doesn't have to be mounted with the hardware needed and again it can be twice as effective meaning you buy less from the start.

Not being mounted also means no holes added to the roof and if you trade up your rig, the solar stays with you. You also don't have to remount if you upgrade the system.

You can leave a portable baking in the hot sun while your rig sits in the cool shade.

Cleaning a panel at ground level is much easier than climbing on the roof.

Now for some of the down sides.

Our 230w panel is big. Newer ones are smaller but still, they are not small or light. I can pick ours up and carry it but the size means I need help getting it in and out of the rig so that I don't bang things up.

We have stored ours on the bed or in the walkway. It's fine for us because we never travel and only deal with it once when we get to the spot and again when we go home. Be traveling and stop for the night and you still have to take the panel out to use the rig.

Being in the rig means there is no charging while on the road.

Portables are subject to high winds and theft.

The last thing is that even as much as I like the positive side of portables, I can't wait until I finally mount one of my panels and can just not deal with the system most of the time.

Now the mitigation

You can get portable systems made out of smaller panels hinged together for easier handling. You can lock up and stake down the panel and we have even transported it on top of the truck so that we had charging while on the road.

-- Edited by jimindenver on Sunday 23rd of March 2014 11:18:59 AM

My system is bits and pieces from here and there.

I woke one morning, checked craigslist and saw a 230w and 220w set of 24v residential panels for $50 each. I was on the road by 6:30 am to pick them up and was on cloud 9 as I drove home. I had no idea about solar or what I had just bought but I was sure happy about it. That didn't last as I quickly found out that I was going to have to spend at least three times as much on a controller to run them. The panels sat in the garage for a year while we used a generator to keep the battery up while out camping.

A year later I found and took a chance on a new Chinese 20a MPPT controller for $100 and luckily it has done what it said would do. I picked up a set of 25 ft solar cables on ebay for $32 and we started using one of the panels last spring. It was so nice to not hearing the generator run and even better not needing to conserve the power.

I have found that most pre made portables are vastly over priced for what you get. My 230w system would cost roughly $400 to set at retail prices. There are less expensive kits, a 200w kit with two 100w panels, controller and cords for $300 but the controller is low end. Luckily a PWM controller is much less expensive than a MPPT.