solar panel battery charging?

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dlb
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solar panel battery charging?

Post by dlb » Tue Nov 27, 2018 10:37 pm

Is anyone here knowledgeable about charging batteries with solar panels? I ask because I had a battery that died either because I killed it by leaving it to charge on a small solar panel for too long, or it was simply it's time to die. I hope one of you smart lads can tell me which it was.

Here's the story. We had a small deep cycle battery that sat in our basement for several years that eventually wound up being used in our camper and travel trailer as the house battery, despite being a little small for running the water pump. That camper eventually ended up on our second property several hours drive away so to make sure the battery was charged each time we went up there, I would disconnect it from the camper and hook it up to a solar panel. I would leave it hooked up this way for 1-2 months at a time.

Here's a complicating factor. The first few times I left the battery connected to the solar panel, I forgot to put the charge controller inline. I noticed some boil over once or twice, then on the next trip the battery wouldn't hold a charge so I checked and the fluid level was low. So I brought it home, topped it up, and charged it on an electric charger. It worked ok after this but seemed to run out of charge even quicker than normal. After that, I put the charge controller in the solar charging system and left it to charge for a month or two.

On my last trip to the property a few weeks ago, I arrived to find the battery was completely dead. I haven't gotten to checking the fluid levels yet or putting it on the electric charger again because at this point, I figure the battery is f-ed anyway. Now, I know I made a critical error by forgetting the charge controller, but I thought that everything should have worked fine this time with the charge controller in the loop.

So basically, I'm wondering if it's a no-no to leave a battery connected to a solar panel indefinitely even if there is a charge controller between the two.

Thanks gang.

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splatterdog
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Re: solar panel battery charging?

Post by splatterdog » Wed Nov 28, 2018 2:55 pm

Don't know much here, but I would imagine a controller is absolutely essential. Several years on a battery is a lot especially if a charge wasn't maintained regularly.

Anything new/neat with your recreational property? Do you go there during winter?

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Re: solar panel battery charging?

Post by Petros » Wed Nov 28, 2018 5:50 pm

I see those used on boats and RVs, and I have seen small ones for use on phones and tablets when out in the wilderness. As I recall they do not provide a lot of voltage, it takes a long time to charge, they are more to maintain the charge. I would think it would not damage the battery because of this low voltage charging, but I have no personal knowledge or experience with them. Seems to me to completely kill the battery something had to malfunction or short out perhaps.
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Re: solar panel battery charging?

Post by BlackStraw » Fri Nov 30, 2018 12:30 pm

As to your battery going dead, it's probably more due to old age, or being damaged during the period of overcharging, than simply having it connected for a long period to the solar setup. Not entirely sure of this, but I think there might be a thing too where if you have a solar panel hooked up directly to a battery with no controller between, there can be something happen overnight where the charge can "leak" back. So generally yes, a charge controller is very important.

Mid-grade, off-the-shelf deep cycle batteries, even under ideal usage/maintenance are generally going to lose a significant amount of their capacity after 4-5 years. There are some specialty deep-cycles which I have heard might be good for 8-10 years, but you might pay 3-4x the cost.

A few other things I've learned over the years that may or may not apply to your setup:

I've got a Boler camping trailer with a small (35 or 40AH) deep cycle battery….when it's parked I have a 10W solar panel hooked up to a very basic charge controller. In the summer it gets enough direct sunlight to keep it topped up, but in the winter 3/4 of our property is in the shade until spring, so I'll try and remember to drag out an extension cord and charge up the battery with an AC charger every 6 weeks or so. If a battery gets drained below a certain voltage and then sits for several months, it's pretty much pooched, you can't just charge it up again and carry on. Once sold a campervan to my father in law with a fairly new deep cycle battery in it, and he either didn't understand or didn't bother about charging it on a regular basis , and he let it go flat and had to replace it the next summer because it wouldn't hold enough of charge to be much use.

Over the years I've collected a few different charge controllers - I've found that some of the larger, fancier ones with the digital screen etc that are meant for bigger installations will actually draw enough power to wear down the battery on small scale setups when you've got long periods of cloudy/rainy days. Not generally an issue in the summer, but here in the pacific northwest as you know it would not be unusual to go 20 days in the winter with only a few hours of full sunlight. So in the camping trailer I've ended up using the smallest, most basic controller for my year-round parking / trickle charging in the yard, and then if I go out camping for an extended time I'll bring the bigger solar panels, and the high-end controller - the advantage being that with the fancy digital display, I can see exactly the current coming in and out, and how it changes as I adjust the angle of the panels. And that makes a huge difference too - having a solar panel in one fixed position means it will only function at maximum efficiency for a couple of hours a day, even if you got 15 hours of sunlight.

MPPT charge controllers can adjust the amperage/current on the fly to get the most out of the available power….so if your solar panel can output 18 or 19 volts, it will transform those extra volts into a higher useful amperage at 14.2v (or whatever the charging voltage is) but the more basic controllers will simply take the 14.2 volts and dump the rest. So with a non-MPPT charge controller you might only be getting 70W of useful power out of a 100W rated panel, even under full sun.

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Re: solar panel battery charging?

Post by dlb » Sat Dec 01, 2018 3:00 pm

That's great info, thanks Blackstraw. Here is the solar panel and charge controller we have been using:

https://www.canadiantire.ca/en/pdp/cole ... p.html#srp

Looking at the details on that page, it seems like the controller should prevent the battery from overcharging. So along with what you said, it was probably a combination of the battery being too small for what we were using it for, too old, never maintained properly, and charged without a controller -- the poor thing had a hellish life, really. Live and learn.

I keep an electric charger up at the cabin and charge the battery with it whenever we run the generator while working on the cabin, so the whole solar thing is primarily just to keep the battery maintained for the month or two between our visits up there.

SD, I can't remember if I've posted any other pics of our cabin so far so I will put them all here. We recently built the frame for the deck roof, the next thing is to put the roofing on it. Then siding is next, and then we will start gutting the camper and move all the cabinets and propane appliances into the cabin. The first pic is a lean-to we made just to keep some supplies dry and have camp fires. You can see in one of the pics that we have a bit of a view of the water but will need to take some more trees down eventually to improve that. Lots to do up there.
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Re: solar panel battery charging?

Post by ARCHINSTL » Sat Dec 01, 2018 5:24 pm

Wow - Thanks, David! It looks quite sturdy - I like the idea of the 2x4 walls!
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dlb
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Re: solar panel battery charging?

Post by dlb » Sun Dec 02, 2018 6:59 pm

Thanks, Tom. I got the idea from a pic of another lumber log cabin so I can't take all the credit for it. Once it's done, I'll take more pics of the interior. Our big concern was not giving rodents anywhere to make nests in the periods when we are not there, so we wanted to stay away from typical frame and insulation construction. Of course it will not hold heat very well but we will only be heating it a small percentage of the time anyway.

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Re: solar panel battery charging?

Post by keith » Sun Dec 02, 2018 9:17 pm

It will hold heat better than you might think. I would have recommended that you treat the 2x4's with a sodium borate solution like Timbor or Boracare before putting on the Tyvec. It is pretty harmless to humans but it resists most bugs and stops most wood decay. Because it is water soluable, you still need the Tyvec layer on the outside. For additional warmth, you could add 2" of solid foam and then side over it. Also put 2" or more of foam on the roof and cover it with a layer of plywood, a rubber membrane and then shingles. You'll be cozy in that.

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Re: solar panel battery charging?

Post by dlb » Wed Dec 18, 2019 6:14 pm

Just remembered I've been meaning to post an update about our cabin for a while. All the exterior stuff is done now, and the propane appliances are in and working well. There is still lots to do though, like plumbing in the drain for the sink, interior door and window trim, more shelving, gutter and rainwater collection system, outdoor shower stall, build a less terrifying outhouse, etc. But being done all the time-sensitive outside stuff has been a real relief -- we'll get to all that other stuff eventually but we're not going to stress about it or rush to get it done. We're looking forward to working on whatever we feel like, IF we feel like it, whenever we go up there next. We had hoped to go last month but work got in the way, and this month it's a monsoon out and we don't feel like sitting in the cabin for a few days, so maybe next month.
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Re: solar panel battery charging?

Post by Mark » Fri Dec 27, 2019 10:01 pm

Cool! Is that a ventilation fan over the stove? What are you using as a power source to run it?

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Re: solar panel battery charging?

Post by dlb » Sat Dec 28, 2019 11:02 am

Mark wrote:
Fri Dec 27, 2019 10:01 pm
Cool! Is that a ventilation fan over the stove? What are you using as a power source to run it?
Nah, no fan. Just the hood that was in the camper. Thought about adding a battery-powered fan and still might if we find condensation when cooking is an issue but for now we'll see how it is without one.

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Re: solar panel battery charging?

Post by marlinh » Wed Jan 01, 2020 9:57 am

Very nice construction David! Looks cozy and beautiful part of the island.

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