newbie confused about solar

[donttellmax]

Hi.  I've been reading and learning about solar but remain kinda confused.  I'd search, but not sure for what I'm searching.

Here's the situation.  I bought and moved into a new Winnebago class C with a Zamp 12V system.  Winnebago's documentation, at least what I've found and have with me, is useless in understanding the system.  I'm figuring it out on my own, the hard way.  It's been almost 2 months and I'm still struggling a bit.  I'm pretty sure the batteries are damaged already.

There's a really irritating alarm which awakens me almost every morning telling me the battery is low.  There's no mention of this in any documentation.  The battery monitor doesn't seem accurate.  Some nights I'll go to sleep with like 25 Ah on the monitor and no alarm.  Other nights, 60+ Ah charged, supposedly, and the charge doesn't last but a few hours.  If I run the generator for a while before bed, I'm generally OK, but not always.  

Dude who did my orientation said the system is really only enough to power the residential refrigerator.  I'm starting to believe him.  I think I need to upgrade something, just not sure what to do first, or if an upgrade is really even necessary.  I just don't have the money for lithium and all the other stuff that entails at the moment.

Any suggestions or guidance would be greatly appreciated.

 

[bass_sears]

You / we need more info.

How many batteries do you have, and how many amp hours is each battery rated for?

What are your draws? You mention a fridge, how many amps or watts does that draw per hour? What other uses do you have (lights, laptops, heaters, etc).

Do you have any solar yet?

This could be a simple calibration issue with your battery monitor, they have to be properly programmed to know when they're full and to know how many amp hours you have on board so they can properly estimate when you're running your batteries too low. Can you get access to the batteries themselves and get some basic voltage readings when the battery monitor thinks the batteries are full and when the battery monitor starts beeping?

-- Bass

 

[bullfrog]

When you say you have a residential refrigerator do you mean that it only plugs into the 110 volt power like in a house and has no controls to change to propane gas or 12volt DC on the front?

 

[donttellmax]

Thanks for the replies.

Yes, the refrigerator only operates on 110, no propane, no 12v. I don't know how much power it draws. It's not immediately available in the documentation. I do need to google that and add everything up. I've learned not to charge things in the evening, and to run the generator on heavy use days. There's the usual laptop, cell phone, two video cams, an eBike (which charges less than once per week,) the gas heater I use most mornings, when there's enough juice in the battery, and the occasional light bulb.

There are two group 31 wet batteries. They're supposedly 105 amp hours each. The ONE time the monitor read fully charged, it read about 75 amp hours. It currently reads 64 amp hours at 11.9 volts. I do have easy access to the batteries, and maybe a voltmeter in the toolbox, but not sure how to use it.

There are two flex panels on the roof, 100W each. They put out about 11 amps in bright sun.

One thing I've noticed which I need to ask Winnebago, the manual says everything the batteries should charge off the alternator while driving, but they don't. No idea what's up with that, but that alone might solve my problem.

 

[bullfrog]

I bought a new RV last year and it came prewired for Zamp solar. It appeared to me to be the smallest gauge wire they could use and still get it to work so there’s that. Since your refrigerator is strictly 110AC and you are not plugged in and only running the generator a few hours it is using battery power to continuously power an inverter which usually has a cooling fan as well as an energy loss inherently, so there is that. If the batteries are not maintenance free the cells need to have the fluid level checked as you will need to insure the plates are covered. They make automatic systems for this but nothing is better than being able to physically look. It is not unusual especially with the hot weather and high loads for the cells to be topped off with distilled water every few months but they should be checked monthly. The batteries you currently have will last longer the less you allow them to discharge. Last winter I had to use my RV heater quite a lot. I would run my generator from 6 PM till 9 PM and at 9 PM turn down the heater to 55 degrees. I happen to have a couple battery packs that I charged while running the generator to charge phones and such later that night should they go down. First thing the next morning my batteries would be at 3/4 charge and I would run the generator 3 or 4 hours from 9 or so until noon. I hooked up a 100 watt portable solar panel and controller directly to the batteries which then topped off the battery charge. I only charge my bicycle, phone, tool batteries and battery packs while the generator is running not using any if little battery power during the day. My batteries last several years longer than they should using them this way. I would monitor the temperature in the refrigerator and see how many hours you can turn it off safely as a start by turning off the inverter. I believe there is a way to use a controller and a smaller inverter to turn on a larger inverter when the compressor in the refrigerator needs to run which may help. There are some older threads here that discuss doing exactly what you are doing because 12volt DC cooler were so expensive to buy at one time. Running your generator isn’t cheap especially when you have to maintain it as well as buy fuel but it maybe your only choice until you get a large enough solar system and battery bank to power everything. So check the batteries, do what you have to to keep them from discharging more than half way, preferably run the generator when they go below 3/4 charge, charge phones, bicycle and anything else while the generator is running only and start saving up for a more/ better solar system and battery bank or a propane/12 volt/110 refrigerator. You should have an isolation relay somewhere that should connect the house batteries to the alternator while the engine is running but it will take a good 4 hours of highway driving to recharge your batteries if the are discharged much at all. Running the big vehicle engine just to charge batteries is not a good idea. Find the relay and check it as well as all terminal connections. Hope this helps if you have more specific questions there are several that can help you but you will need to tell them exactly what you have to work with.

 

[donttellmax]

That's very helpful, Bullfrog.  Thanks.  Hadn't considered turning off the refrigerator.  Was worried about frozen meat thawing and re-freezing.  Knowing me, I'd forget to turn it back on.  LOL.  I have learned only to charge big stuff like the bike when the generator is on, and to run the generator for a bit before bed even when not charging anything.

 

[tx2sturgis]

Sorry to say that the 'residential' fridge (RV residential fridges are trendy these days) is a poor choice for extended boondocking. They look nice, hold a lot of food, and are 'familiar' to homeowners, but they are power hungry, difficult to service and/or repair/replace, and the entire system as you bought it will work for a day or two off-grid but then must be fully charged by either the genset running for many hours OR, as the factory intended, you must plug in your 30 or 50 amp cord to a park or campground shore power connection.

200 watts of flat roof-mounted solar is just not enough to power everything you listed, especially the fridge. As the days get shorter this fall and winter, and the sun angle drops, your situation is going to get worse. If you want to be able to do extended off-grid boondocking you will have to make an expensive upgrade: more solar panels and more batteries, and probably an additional charge controller.

If I suddenly found myself in this situation tomorrow, I'd start by buying a 200 watt portable system, 'briefcase solar' or similar, that you can set on the ground and aim at the sun, with 20-40 feet of good heavy cable, with anderson connectors at the panels and near the batteries, and a suitable charge controller installed somewhere near the battery box.

Even then, on cloudy days, you may still have to run the genset for several hours per day to keep things topped off.

And, of course, reduce your power consumption as much as possible. Turn off every electrical item you don't need or aren't using.

There is one other option: You can buy an efficient 12v compressor freezer/fridge of the capacity you need (40-60 qts is usually about right) and then just use your 'residential' fridge as a 'dry' food pantry (turn it OFF). The 12v fridge will sip energy compared to the main fridge, and probably will run on the 200 watts of roof panels If you reduce or eliminate all other power consumers. 

Good luck with this.

 

[donttellmax]

...

Good luck with this.

Thank you so much!  That's pretty much the bottom line.  Gotta spend some cash.  I wonder, though, why add a portable system when my built in system is expandable?  I don't  currently have storage space for such a thing, and can put another panel or two on the roof to max out my system at about 490W.  I mean, I have considered it, just wondering what the advantage might be.  Same with the 12v fridge.  Great idea, just no place to conveniently put it.  

I have upgrades picked out.  They come to like $3k for a 190 watt panel, two battle born batteries, and battery-to-battery charger, not including a new charge controller.  Not sure if that's needed.  It's a lot, but I'm spending a ton on propane to run the generator, so...

 

[tx2sturgis]

If you have portable panels you can aim that array at the sun, moving them a few times a day, and harvest all of what they can capture...lets say close to 200 watts (not quite but lets assume that)

Flat, roof mounted (non-movable) 200 watts of panels will only harvest 100 watts or so in the winter (low sun angles) and only then, for a few hours a day...if that. Plus, they will require occasional washing or cleaning...flat mounted panels on the roof have to cleaned or washed now and then. Accumulated dust and dirt can reduce the harvest by quite a bit.

I use a combination of portable and roof mount panels, always...and it has worked well, and it is what I will always recommend unless there is some hard reason not to. 

But my suggestion is what I would do now, to start harvesting more power now, but it is not your only option. You can always add more panels to the roof, now or later. If you find the portable suitcase array is not needed at a later date, they are easy to sell.

 

[donttellmax]

Excellent!  Thanks again!