Additional batteries or solar, or both?

[RVLola]

We have a new Winnebago Forza and it comes with a 2000 watt inverter and 4 house batteries. There is room for 2 additional batteries to be installed.

We would like to have more time when boondocking to run the fridge and lights and fantastic fans, and maybe the TV, without having to run the generator. Right now we can go about a day and a half.

Would additional batteries give us significantly more time? How much difference would solar panels help (it's usually cool and sunny when we camp, but not always)? What makes the most sense financially?

Thanks for your input.

[simonsrf]

You don't want to mix old and new batteries. If you are considering solar panels, you'll have the extra expense of controllers, combiner boxes, possibly battery monitors etc. We are full timers, and use our solar a lot,but if you're not going to use it a lot, chances are that using your generator is the best option for the possible added expense.

[SilverBob]

Adding 50% more battery capacity will obviously give you 50% more power to use, all things being equal. A decent solar system would probably be your best bet. Panels are pretty cheap right now. I've been buying 100-125 watt panels for about $1.25 per watt lately. Spend a couple hundred dollars on a good charge controller, and you'll be amazed what a difference it will make.


On the other end, there are some things you can do to cut down on usage. If you still have incandescent light bulbs in your coach, replace them with LEDs. Make sure your inverter(s) is/are appropriately sized. You don't want a 2000 watt inverter "idling" most of the time, when you only need 700 watts for your load, for example.


Google "The 12 Volt Side of Life", and you'll have lots of entertaining reading on this subject.

[Imurphy907]

How old are the batteries? If less then a year old I would have no problem adding more. If they are more then a year old then I would add more when I replaced the others.

Adding more capacity is always a good thing. But then you have to realize, you now have more battery to charge. Many stock "rv chargers" are far from being chargers. You will be headache's ahead by using a real charger from the get go.

Now for usability It depends on how you use your system. If you only go out for a few days here and there then just add the batteries. You will get longer use out of your toys. and be able to recharge when you get home.

If you Camp for a week or more at a time, then Add solar.

To size the solar system to work best for you, we need to know how much power you use on average per day, and where in the country you like to hang out.

You can put together a nice 200 watt kit for ~$600 and a 400 watt for about a grand. Depending on your usage. But even with the solar I would always suggest more storage. This allows you to make it thru more cloudy days without generator. And it also reduces the depth of discharge on the batteries during use, and makes them last longer.

I just sold my coach with a 400 watt system. And we are getting ready to pick up a 5th wheel. That will be getting a 1KW system to start. And may expand it in the future. But we are going full time and don't plan to live in RV parks.

[MattTaylor]

Well... If you are running off of battery/inverter for a day and a half then using the generator to recharge the battery bank then I suppose it's safe to assume that you are not plugged in and are wanting to dry camp off the cord, awesome!

If that's the case, go solar, you won't regret it.

In my opinion, this would be the easiest way for you to answer your question. Since you already have a battery bank and an inverter, use a voltage meter with an AMP clamp to find out exactly how many amps per hour are being drawn from the bank. Put the clamp around the positive wire between the battery bank and the inverter. Turn on just the inverter, the meter will tell you it's true no load AMP draw. Now turn on the fridge, and so on, each thing one at a time by itself. You can even recall exactly how you camp when for example, watching tv in the evening. Just turn on everything that you would normally use, read the meter. Then turn those things off that you normally turn off when going to bed, set up for sleepy time, read the meter.

For example. I have 6 batteries in the bank that hold 675 AMPs, giving me 337 usable AMPs before needing to be recharged. When I did this AMP draw test I found that our regular NORCOLD fridge draws 23 AMPS per hour from the battery bank, so I could run it for 337 / 23 = 14.6 hours. This of course is a simplistic way of considering AMP draw to battery capacity but it's easy and it works, good thing our fridge also runs on propane

If you wanted to go solar without installing panels you could try one of the folding portable solar panels. Eco Worthy has a 200 Watt version that comes with a charge controller built in. It has long leads so you can set it away from the shaded RV if needed. Just point it at the sun, clamp the leads to battery bank, and you're done. This will only run you about $500 and will increase your run time without having to run the generator. If you decide later to install a full solar charging system on the RV, this portable will still be VERY useful and will become part of the overall system.

As for battery banks. For the Trojan T-105's I pay $135 each, and that includes the core charge. $810 for a bank of 6, at a local golf cart shop. I highly recommend them.

Best of luck and happy camping whatever you decided!

[Reed Cundiff]

Go with both. Increase battery by 50% and look further into solar to determine if it will satisfy your requirements. Most that go with solar are extremely happy with it. Six large lead acid batteries and several hundred or more watts of solar will permit you to boondock in the woods indefinitely (limited only by requirement to dump holding tanks and get fresh water - we carry 2 to 6 x six gallon jerrycans for water)

Reed and Elaine (way into the dark side of autonomous solar living (95% boondocking/mootchdocking full time)

2006 Chevie 350 diesel 4x4 (dualie) w/45 gallon Transfer Flow
34' Open Range 337RLS 5th wheel
1400 W of solar (90 V to controller)
TriStar MPPT-45 controller
8.6 kW-hr (48 V nominal) LFP
Magnum 4.0 kW PSWI
Mean Well 508 W 48 V to 12 V converter

[MattTaylor]

1400 Watts of solar, wow!! What is your average peak incoming amps from the array? The 480 watts I have on the roof peak out around 29 amps. 120 Watt portable accounts for another 7. I'm guessing, yours must be around 90 amps, that's AWESOME!

I'd really LOVE to see photos of your 5th wheel solar setup

[normandlegra]

Originally Posted by MattTaylor

1400 Watts of solar, wow!! What is your average peak incoming amps from the array? The 480 watts I have on the roof peak out around 29 amps. 120 Watt portable accounts for another 7. I'm guessing, yours must be around 90 amps, that's AWESOME!

I'd really LOVE to see photos of your 5th wheel solar setup

Anyone can write anything on their signature... we'll just wait for the pictures to find out !

BTW, his controller is a 45 AMP

[bobandshaz]

WOW 1 1/2 days I think that is great!!! Please keep us updated.
Thanks

[Reed Cundiff]

Max we have gotten is just over 1400 W. Maximum harvest according to TriStar. TriStar monitor has shown that one-day harvest in June has been above 8400 W-hrs. Things are much easier to explain in watts.

1400 watts at 90 V is 16 amps. The controller converts to 48 V for the battery suite so 1400 W at 48 V nominal is 25 amps. Most solar systems son designs and fabricates for businesses and power companies are above 400 V. If we went with 12 V arrays in parallel, this would be 117 amps. If we were to add another two or three panels, then we would go to an MPPT-60 for safety margin of 100%

Attached are photos that normandlegra seems to have requested, even though they have been posted before.

1. Front bay of 5th wheel. Included are:

4 x 180 amp-hr (12 V nominal, 13.5 V actual) batteries.
Each battery is 4 CALB cells
The four batteries are in series to provide a 48 V nominal (54.5 actual) battery suite (16 CALB cells) which provide 8.6 kW-hrs at 48 V nominal.
Magnum 4.0 kW PSWI
as was explained above.

Three possible problems with LFP are:
to hot, to cold, and being kept at full charge

The battery suite is in shade of overhang and is well ventilated. Problem can occur when running air conditioner for several hours off battery/solar panels and inverter emits a lot of heat when converting 1750 or 2000W. Front panel and side panels must be open. Will install 12 V receptacles for 12 V fans (12 W - OK will pay grandson to do same.

LFP can discharge at very low temperatures but there are problems with some LFP cell chemistries with charging at high C levels. Such problems are probably not important with solar charging since the cells will warm as they charge. however, will install two halogen bulbs (30 W) in bay to keep it warm on cold nights.

Finally, we have never hooked up in cold weather (only hooked up once in two years - and the few times we have been in RV parks, we have not hooked up - no reason to). So system cycles an we are usually down around -3kW-hrs in morning since we run the Dometic fridge (another power hog) all day on AC on sunny days and all night if it will be sunny the following day.

Next photo is roof of 5th wheel. There are six x 235 W panels in two gangs of three in series, and then in parallel at 90 V to controller. We have room for two or three more panels but cannot convince ourselves it is necessary. Two more panels would run the Dometic 13,500 BTU energy hot without battery drain.

Finally is photo of 5th wheel at son Cary's place where we are currently (Elaine just had full knee replacement on 1 July so that shot our plan for either Trans Labrador and Newfoundland or Queen Charlotte Islands this summer). Son is totally off grid with around 5 kW of solar. Note panels on his workshop. Daughter has about 7 kW in Las Cruces, NM and brother-in-law has about 4 kW on house in Albuquerque.

Previous system is in wrecking yard somewhere west of Mexico City. We were in 70 car pileup at 8400' on Mexico 85 between Orizaba and Puebla. Truck and 5th wheel were totaled. Hit/and got hit so hard that the kingpin/hitch were destroyed. Onan propane generator was destroyed All four panels on that system remained in place as did the batteries (then glass mat) and inverter. System still worked perfectly.

We have lasted 6 days or so in rain forest of Olympic Peninsual and about the same time in heavy timber at Cave Creek in the Chiricahuas. Had to change power management SOP. The inverter was off unless we were running microwave or watching Mystery Theater on DVD. We were down to about 40% SOC. LFP can operate down to 20% SOC for supposedly 2000 or more cycles but we choose not to go below 50% SOC if we can help it.

Last photo is in the wrecking yard between Orizaba and Mexico City. Mexican Insurance decided that they really could not fix that with bondo. Elaine woke up after operation (three broken ribs and two compound fractures of lower right arm) and said "Reed, rig and truck are destroyed, have to start thinking of their replacements!" "Yes dear."

Any further questions or photos will be cheerfully answered. Have had requests for better photos on another forum. Do hope you believe this post now.

[normandlegra]

Thanks for all that great information and pictures; I never tought you could have so many solar panels on a rv roof !
You do have a nice and functional setup !

p.s. MattTaylor originated the demand for pictures.

[Reed Cundiff]

Normandlegra

We just made a template of the 235 W panel (fancy term for a sheet of cardboard cut to the correct dimensions) and laid it about the roof to find places that would not be in shade from the various protuberances. You might find that other sized panels might fit your roof features better. Six x 350 W panels would have worked as well but son likes 235 W panels and had six pallets on hand.

We have a friend who will wind up with 2 kW of panels on his camper shell and motorcycle trailer combined. I think he plans to have panels that fold down alongside the camper shell and are then cammed into horizontal when in use. He has battery banks in both trailer and camper shell (1 1/2 ton truck). I think he is not quite sure what he will do with all that power since the a/c requirements of his camper are not that great.

There are discussions of whether one should go with roof mounted or ground based panels. Ground based has the advantages of being able to place in sun while rig is in shade, and being able to orient the panels to get maximum solar insolation in morning and afternoon; however, after a certain level of power (say 300 W), it would probably get to be a bother unless set up for a few weeks or more.

Roof based means that you can forget about them unless they covered with snow and you can be charging while going down the road.

Photo attached of scraping snow off panels at son's place. Tried getting on roof and I could not even sit down without sliding (turn 75 in a month and getting on snowy roofs is not on my list of things to do). Final photo is where we prefer to be in winter, on the beach in Yucatan, about 20 miles from Tulum

Reed and Elaine

[MattTaylor]

Okay, I'm lost in nerd nirvana!! That is totally AWESOME!!

The only thing stopping me from upgrading our solar system to something like yours, that will even run the A/C units is the cost of those Lithium batteries. Ouch!! For the Trojan T-105s I pay $135 each and that includes the core charge.

If you don't mind me asking, can you estimate what it would cost to put together a batter bank like yours?

[Imurphy907]

200ah balquin cells are ~$250/each. To get 48 volt you need 16 of them.

Mppt controller like the midnight solar classic 150 is ~$650

Panels are between $0.85-$2.00 per watt.

Copper cost money, so do fuses and such.

But having the power you need, when ever you need it. PRICELESS.