Solar planning thoughts

[belfert]

    I got an incredible deal on used batteries.  A storage guy had 10 AGM "High Rate Max" batteries, 12V. 78 A/hr each that somebody had bought surplus from a cell phone maintenance company and dumped at his place.  I asked him if he'd sell them - he said "yes, I was going to take them to the battery recycle place, they offered me $12

I got 16 telecom AGM batteries for free when the telecom decommissioned equipment at my employer.  They told me they just scrap the batteries so I asked if I could have them.  They had just been on float for three or four years.  Never discharged as we had never had a power failure.  Not light, but free is good.

[belfert]

This thread has drifted into batteries so how do you guys keep from charging lithium batteries at temperatures below freezing?  My understanding is that lithium batteries are destroyed if charged below freezing.

[freds]

This thread has drifted into batteries so how do you guys keep from charging lithium batteries at temperatures below freezing?  My understanding is that lithium batteries are destroyed if charged below freezing.

That is an important consideration if the couch is going to be left unoccupied.

As to preventing damage that is generally the job of the battery management system, some charge controllers also have a temperature input.

Even on a poor solar day you generally get some power which should first go towards warming the batteries.

I am planing on doing IOT (internet of things) local automation using a Raspberry Pi and Node Red as I progress in my modifications.

Further edit: Also lithium batteries do not have to be vented, so can be in a more insulated compartment.

[Jim Blackwood]

Getting back to that video of the sliding array, while pretty slick it doesn't strike me as particularly robust. No, what I was thinking about should  be better able to resist wind loadings without damage, and would have some capability to adjust tilt. Also, any sliding mechanism is inherently more troublesome than a hinged array.

Think tri-fold brochure. It all folds flat but hinges open to the preferred position, the cells protected inside in the transport position.

Jim

[chessie4905]

If you get the panels installed on the roof, but haven't yet wired them up, does it cause an issue with the panels out in the sun? Should they be covered till wired up?

[richard5933]

In my reading, most of the panels out there will do just fine if in the sun but not connected. What do you think happens to the panels with the batteries are full and the charge controller cuts off the flow? There is no heat sink to absorb the output from the panels - it just goes to nowhere until needed.

https://physics.stackexchange.com/questions/71434/where-does-electricity-go-from-a-solar-panel-that-is-not-plugged-in-to-anything

The one thing that I have seen warnings about is open terminals/connections on the panels if left outside. I've seen recommendations of plugging in dummy terminals to prevent moisture and/or dirt from entering the panels connectors.

[belfert]

That is an important consideration if the couch is going to be left unoccupied.

As to preventing damage that is generally the job of the battery management system, some charge controllers also have a temperature input.

Even on a poor solar day you generally get some power which should first go towards warming the batteries.

I don't have solar on my bus and probably won't have solar on my bus, but I do have batteries.  It is possible I might buy lithium batteries the next time around due to lighter weight and high DOD.  Low temperature last winter was -30F.  I keep my bus plugged in so the AGM batteries get charged as needed all winter long.  I cover the bus over the winter so any solar panels wouldn't charge anyhow.

I have solar for my house that was installed with a combination of DIY and a friend who works for a solar company.  Last winter we had so much snow that my rooftop panels didn't produce any power for over two months.  Often the snow will melt and slide off, but not when you have lots of heavy snow.  I'm sitting on the power company owing me nearly $500 right now.  We have true net metering in Minnesota and the power company will write me a check based on the retail value if I still have a credit at the end of my yearly cycle.  I expect to get a payment from the power company when true up time comes around.

[freds]

I don't have solar on my bus and probably won't have solar on my bus, but I do have batteries.  It is possible I might buy lithium batteries the next time around due to lighter weight and high DOD.  Low temperature last winter was -30F.  I keep my bus plugged in so the AGM batteries get charged as needed all winter long.  I cover the bus over the winter so any solar panels wouldn't charge anyhow.

If you are going to leave them for months; I think the procedure is to discharge to the 60% level and then disconnect them. They don't need a trickle charge like AGM batteries.

When you select a battery vendor, ask them for their storage procedure. Another option is place them in a insulated box and add water freeze warmer.

[buswarrior]

If whatever management of a new battery type relies on a steady source of electricity...

That's playing the same dangerous game as counting on the electric company for freeze protection...

If "just sitting there" under certain weather/temperature conditions is going to harm something, without anyone there to deal with it, that's not a good battery choice for most busnuts.

If those conditions come about, there's likely many other distractions, life safety, the ability to travel/access, and the coach is going to have to fend for itself.

Good old golf cart batteries won't mind?

The whole story is hard to find on the internet.

Safety first!

Happy coaching!
Buswarrior

[Fred Mc]

Unlike lead acid batteries, Lithium batteries don't loose power over time so you can leave them for months.About the only thing that will damage them is charging when its freezing.Cold doesn't hurt them otherwise. So if you are storing your bus for the winter disconnect the batteries(also applies to FLA's) and turn off the solar panels(if you have them).

[belfert]

I don't like anything sitting for months that requires power or heat to keep something from getting damaged due to cold.  What happens if the power goes out or the heat source fails?

Years ago as a teenager I got shocked by some warming cables for a outside drain.  They were cracked and probably not providing heat to keep the drain open any longer.

[Iceni John]

Getting back to that video of the sliding array, while pretty slick it doesn't strike me as particularly robust. No, what I was thinking about should  be better able to resist wind loadings without damage, and would have some capability to adjust tilt. Also, any sliding mechanism is inherently more troublesome than a hinged array.

Think tri-fold brochure. It all folds flat but hinges open to the preferred position, the cells protected inside in the transport position.

Jim

That's pretty much also what I thought.   It's a very Rube Goldbergian way to do what should be a very simple process, and there's lots of things that can (and probably will eventually) go wrong.   Lots of critical single points of failure!   The fact that the panels cannot tilt means that he is throwing away a lot of his potential solar harvest.   Also, cleaning the panels will be neither easy nor safe;  cleaning them needs to be regularly done to preserve their efficiency.

I guess some folk just like high-tech for its own sake.   I prefer simple mechanical solutions and human power.

John   

[Fred Mc]

"It's a very Rube Goldbergian way to do what should be a very simple process, and there's lots of things that can (and probably will eventually) go wrong.   Lots of critical single points of failure!   The fact that the panels cannot tilt means that he is throwing away a lot of his potential solar harvest."

Ive been following this guys build for some time. I don't think that lack of tilting panels will even be noticed. In one of his videos he shows running 3 air conditioners from the panels"only". And while I'm sure he will have some teething problems it certainly doesn't look "Rube Godbergian" to me.
There are other examples of using sliding panels on you tube. Also sliding panels means you don't have to get up on the roof to tilt them-a safety concern.

[somewhereinusa]

I don't like anything sitting for months that requires power or heat to keep something from getting damaged due to cold.  What happens if the power goes out or the heat source fails?

I have lithiums and, as of right now, no solar. I have installed two fail safes to keep the batteries from being charged when below freezing.  Both are controlled by digital thermostats. First is a heat pad that the batteries are sitting on comes on about 38° and off at 45°. Second, a latching contactor to totally disconnect batteries from everything, set to 34°

The latching contactor also has a manual switch so, in winterizing the bus, I ran the batteries down to about 60% and unhooked them.

I work on the bus in the winter so I need power, it's always plugged in. My inverter/charger needs 12V to energize and pass 120V AC through so I added an AGM just to keep everything happy. My inverter/charger also has an extra 12V output circuit to maintain the start batteries.