Help with Design for multi RV charging setup

[chrisski]

Mostly following along to learn about proper charging of batteries.

I used a solarargizer to keep the Dual Batteries on my truck charged for six months. Started up nice and strong afterwards. I can no longer find this product.

For my fifth wheel, with a single battery, used a 10 watt solar panel from an auto part store, that I screwed up my extending the wires by 25 feet into the sun. Did not produce enough voltage with the loss from the extended too small gauge wires, and killed the battery. I now remove the battery, and charge with a battery tender junior.

[Ampster]

if 'wintering' for stored RVs is in question, each RV already has it's own 12v Disconnect that allows the House battery bank to be disconnected, just for this reason - so that batteries aren't drained while in storage - the disconnect is actually called the 'USE/STORE' switch. Some find that they like having some power, regardless, but it's not necessary, and most RVrs aren't as requiring of it as you might think.
Installing solar arrays, controllers, and wiring just to give storage RVs 'some' power is probably an expensive proposition compared to what you'll get back in fees, and if solar isn't 'working' properly for your paid RV owners, how are you going to 'fix it', if it's simply because the sun isn't out, weeks of clouds or rain, etc., or are you going to have owners want to argue that they 'need' that power and that's 'why' they stored it with you(?)... I think electrical might be overkill.

Good points from a risk management perspective. I am risk adverse so I would provide the technical support and the infrastructure in the form of wires and a structure to support solar panels. It would be hard to provide a system that works for everyone. The one tenant that already has weak batteries and plugs into your system will blame you if you couldn't provide enough capacity. If you had unlimited 120v capacity it would be a different story.
NOTE: As an after thought, as more RVs evolve to Lithium batteries, self discharge would not be an issue that would need to be addressed.

[PNW_Steve]

if 'wintering' for stored RVs is in question, each RV already has it's own 12v Disconnect that allows the House battery bank to be disconnected, just for this reason - so that batteries aren't drained while in storage - the disconnect is actually called the 'USE/STORE' switch. Some find that they like having some power, regardless, but it's not necessary, and most RVrs aren't as requiring of it as you might think.
Installing solar arrays, controllers, and wiring just to give storage RVs 'some' power is probably an expensive proposition compared to what you'll get back in fees, and if solar isn't 'working' properly for your paid RV owners, how are you going to 'fix it', if it's simply because the sun isn't out, weeks of clouds or rain, etc., or are you going to have owners want to argue that they 'need' that power and that's 'why' they stored it with you(?)... I think electrical might be overkill.

Battery cut off switches are a great idea. I have them on both my house and chassis batteries. Unfortunately they do nothing for self discharge. I stored one of mine longer than I had intended. Life happens. After sitting for eight months my batteries were degraded to the point that if I let it sit for more than a day it would not start. I replaced them and added my $100 solar tender. No worries now.

If OP had shore power in the facility it would make the most sense to use it. Lacking shore power, I would not hesitate to spend a couple of hours and a hundred bucks for each space to add that amenity for your guests.

Just my $0.02.

[PNW_Steve]

I thought that spending about $100 was a bargain after replacing $400 worth of batteries.

Again, an 80watt panel and a reasonably priced PWM controller worked great for keeping my 3x group 31 starting batteries happy.

[NCmountainsOffgrid]

if 'wintering' for stored RVs is in question, each RV already has it's own 12v Disconnect that allows the House battery bank to be disconnected, just for this reason - so that batteries aren't drained while in storage - the disconnect is actually called the 'USE/STORE' switch. Some find that they like having some power, regardless, but it's not necessary, and most RVrs aren't as requiring of it as you might think.
Installing solar arrays, controllers, and wiring just to give storage RVs 'some' power is probably an expensive proposition compared to what you'll get back in fees, and if solar isn't 'working' properly for your paid RV owners, how are you going to 'fix it', if it's simply because the sun isn't out, weeks of clouds or rain, etc., or are you going to have owners want to argue that they 'need' that power and that's 'why' they stored it with you(?)... I think electrical might be overkill.

[SunEagle]

I suspect that it is for the same reason many of us connect an external 12v source every Winter. To keep the batteries charged.

It seems that I am the only one who thinks OP has a good idea. I have stored my RV's in places with no 120v power. A generator would NOT be a practical solution. The first year I stored without power I destroyed a set of batteries. The next year I threw an 80 watt panel on the roof and a PWM controller to keep the batteries. Worked great for me.

Something like this: https://www.amazon.com/Battery-Tende...omotive&sr=1-7 along with a 50watt panel for each bay.

While I agree that keeping the coach batteries topped off and happy there are a number of ways to do it.

I use to have my RV in an open storage place so needed to run the generator or main engine to get the batteries recharged. Not the cheapest way but a small solar trickle charge should work provided the batteries get enough

[PNW_Steve]

as an RV owner, a diesel motorhome, and having 'stored' my RV several times, my question would be 'why' are you wanting to provide 12v power to these bays, if I get that you are using these as 'rv storage' for patrons.... ?

I suspect that it is for the same reason many of us connect an external 12v source every Winter. To keep the batteries charged.

It seems that I am the only one who thinks OP has a good idea. I have stored my RV's in places with no 120v power. A generator would NOT be a practical solution. The first year I stored without power I destroyed a set of batteries. The next year I threw an 80 watt panel on the roof and a PWM controller to keep the batteries. Worked great for me.

Something like this: https://www.amazon.com/Battery-Tende...omotive&sr=1-7 along with a 50watt panel for each bay.

[NCmountainsOffgrid]

as an RV owner, a diesel motorhome, and having 'stored' my RV several times, my question would be 'why' are you wanting to provide 12v power to these bays, if I get that you are using these as 'rv storage' for patrons.... ?

[J.P.M.]

It sounded to me like OP simply wants to float the batteries on stored RV's.

There is a product out there called "battery tender" or "battery minder". I forget which but a little Google Fu should turn it up. The US Army uses them to keep batteries up on vehicles parked long term. They make a 12v version as well. IIRC: they use an 80watt panel.

That may well be. If so, and depending on particulars, meeting the duty with an off grid PV solution, while having cachet and a gee whiz factor, may not be the overall best way to meet the as yet undefined duty.

If it's simply a float operation for batteries, and nothing or not much more besides a light or two, a phone and a laptop, etc., depending on that duty, seems to me that a small ice powered generator would be less $$ by about an order of magnitude, and a lot less hassle as well.

Still, whatever the duty (= output requirements and patterns), that load is usually a required input for the design of any system, on or off grid.

Maybe the OP came here unaware of the costs in treasure, time, and toil required to obtain and maintain an off grid system.

Posters coming here with not much more than good intentions and the rose colored glasses outlook that's been imparted to them by their own uninformed wishful thinking and by peddlers and the greenwash media pushing the idea of PV as simply an always cost effective plug/play no brainer is not uncommon and seems to me has happened before around here.

An ICE generator solution may not be simple as an extension cord and some fuel, but it's probably less complicated than off grid PV and a whole let cheaper and easier to maintain.

It'll most likely be needed anyway for off grid applications. Get one that's appropriately sized for the duty, Spring for a knowledgeable, licensed electrician to wire it in, and maybe add the PV one bay at a time or other increment after learning the possibilities and limitations of PV from a reliable source, and then see how it goes.

[PNW_Steve]

I haven't seen any mention of system duty yet. How much energy do you expect all this PV to provide over a year's time? PV systems are usually sized to meet all or some portion of a load, particularly off grid systems that tend to be expensive in ways beyond initial $$ cost. Depending on how many of what may wind up being a number (how many ?) independent systems, get set for a part time job maintaining them.

If you're looking for help with system design, my respectful suggestion, if you haven't done so already, is to start system design by specifying a system duty.

Add the cost of generator backup to the PV costs.

Also, do you have any building codes or permitting to contend with ?

It sounded to me like OP simply wants to float the batteries on stored RV's.

There is a product out there called "battery tender" or "battery minder". I forget which but a little Google Fu should turn it up. The US Army uses them to keep batteries up on vehicles parked long term. They make a 12v version as well. IIRC: they use an 80watt panel.

[J.P.M.]

Thanks for all the great replies. The ridge of my roof runs north-south but the angle is not all that steep. This is a metal building. The simple idea of putting a panel on the roof over each bay is a good one. I will get to thinking about making a roof mount for the two panels I have.

I haven't seen any mention of system duty yet. How much energy do you expect all this PV to provide over a year's time? PV systems are usually sized to meet all or some portion of a load, particularly off grid systems that tend to be expensive in ways beyond initial $$ cost. Depending on how many of what may wind up being a number (how many ?) independent systems, get set for a part time job maintaining them.

If you're looking for help with system design, my respectful suggestion, if you haven't done so already, is to start system design by specifying a system duty.

Add the cost of generator backup to the PV costs.

Also, do you have any building codes or permitting to contend with ?

[OkanoganJim]

Thanks for all the great replies. The ridge of my roof runs north-south but the angle is not all that steep. This is a metal building. The simple idea of putting a panel on the roof over each bay is a good one. I will get to thinking about making a roof mount for the two panels I have.

[SunEagle]

Well who doesn't want to be cool. But to bring in Grid power, I need to open up a road, ditch in Primary power, purchase a Grid transformer, then since this is Commercial, pay an electrocution to setup a meter and a service, and wire each bay. My RV which is inside the building has a solar panel on the roof that maintains the battery. Only problem is, its now inside. So this is my inspiration for trying to design this system. This building will store RVs, so only a maintenance level of charge is to each bay during daylight hours is what i am trying to achieve.

As I and others have stated. It would be less expensive and more resilient to have a solar panel and charger for each RV bay. Since you only need a trickle charger a 100watt panel should be enough. But you still need to run either the generator or engine to get the coach batteries back up to 100% SOC and stir up the fluid to keep them around as long as possible. A trickle charge will just keep them up but it is not good to keep them that way for long.

[littleharbor]

Even if you have to tilt the panels with a couple legs I'd say put each individual panel directly over each bay. The shorter the wiring, the better. Also the closer to the battery to the CC the better.

[Mike90250]

Does the roof have a good angle and view of the sky for direct sun in all seasons ?

if so, here's what I'd do.

a) 100w panel on the roof, extend wire to a J box with fuse and Anderson connector (female)
b) install a simple PWM charge controller INSIDE the RV to be charged, and wire the BATT terminals to the battery to be charged (fuse this also)
c) install a Anderson connector near the drivers side front grill, connected to the PV input of the controller (female)
d) get a neon colored electrical cord from wally world and install male Anderson connectors on both ends.
e) drive the RV in, connect the colored cord to the RV and solar Jbox. One RV is now charging when the direct sun hits the PV panel.

Lather, rinse, repeat as needed

https://www.andersonpower.com/us/en/resources/PowerPoleResourcesPage.html

and

https://www.andersonpower.com/content/dam/app/ecommerce/product-pdfs/PP30-P-S/ds-pp30ps.pdf