Solar charge controller, what for?

[PNjunction]

Ack - I promise to clean up my responses when I am once able to edit my replies. Guess they are still working on that.

[PNjunction]

I'm thinking of leaving one of my old FLA sets at the house doing what they like best, being an ornament on float, for emergency bad weather or what ever other reason. I'll give them a panel to keep them floating.

It may be off topic, but had to say this up front - you ARE going to use a controller too right? Conventional wisdom has people popping small panels on their Pb batteries without them, and this works as long as you are CYCLIC duty with them, but in a fully-charged float / standby - NO WAY. Even a dinky panel without a controller on a fully charged or nearly fully charged battery will have them trying to reach 18v or so. Bad news and dangerous obviously.

back to our regularly scheduled program..

[bungawalbyn]

It may be off topic, but had to say this up front - you ARE going to use a controller too right? Conventional wisdom has people popping small panels on their Pb batteries without them, and this works as long as you are CYCLIC duty with them, but in a fully-charged float / standby - NO WAY. Even a dinky panel without a controller on a fully charged or nearly fully charged battery will have them trying to reach 18v or so. Bad news and dangerous obviously.

back to our regularly scheduled program..

Yes Yes Yes. It's all still in place. Just have to make a few adjustments as I have pirated some bits for the new system.

[bungawalbyn]

With all the panels hooked up I'm getting about 65 amps, which runs the batteries up to my HWS diversion cut in about 1 hour after the sun hits the panels. As this amperage is less than HWS element pulls this means the HWS is cycling. I've adjusted it so the cycling is not rapid, but it does draw on battery power to make up the difference. Oddly enough it should work better as the sun comes up towards summer and the amps increase.

The efficiency of the LIFePO4's harvest and return of power has caught me a little by surprise. On the FLA's I was struggling to keep up with usage in fine weather, now I'm looking at taking panels out of the array. I got them because of their promise of efficiency, but how much difference that has made is amazing.

The HWS just turned on, 1 hr into charging!!! Maybe I'll go get an air conditioner for summer.

[PNjunction]

With all the panels hooked up I'm getting about 65 amps, which runs the batteries up to my HWS diversion cut in about 1 hour after the sun hits the panels.

Wow - you have the luxury now of figuring out how much more you can power with it. OR, ask this question again in December, when you may have very little solar insolation! Think twice before removing those panels. What I'd do now, is just run in a lower psoc window and basically have the cells consider your needs as a mere aggravation.

The efficiency of the LIFePO4's harvest and return of power has caught me a little by surprise. On the FLA's I was struggling to keep up with usage in fine weather, now I'm looking at taking panels out of the array. I got them because of their promise of efficiency, but how much difference that has made is amazing.

This is the WOW effect that can't be reproduced on paper or in a forum. Kind of like describing to someone how riding a Harley Davidson feels like. You can't - they have to experience it for themselves. Or pilot a large radial-engine prop plane.

If you run lead as a standby / backup like I do instead of lifepo4 for daily cycling, consider a pure-lead agm now that you are addicted to efficiency. The internal resistance of even a conventional agm is twice the rate of fla (0.10C vs 0.25C typical, which means less time charging), and of course pure-leads which are even more efficient / faster to charge.

I'll leave the lead to other threads, but just goes to show you I'm no lifepo4 fanboy, but man, can I relate to your wow factor. Everyone who actually goes hands-on goes through it.

[bungawalbyn]

Wow - you have the luxury now of figuring out how much more you can power with it. OR, ask this question again in December, when you may have very little solar insolation! Think twice before removing those panels. What I'd do now, is just run in a lower psoc window and basically have the cells consider your needs as a mere aggravation.

Hi PNJ,
I have to fiddle with the settings a bit when I can eliminate the voltage drop on the board, or reroute the cell sensor wires to get a truer reading. Other than that all seems to be working as designed.

As to sun in December, I'm in Australia, December is summer. Its winter here now. SHORT DAYS

[PNjunction]

Perfect! Oh man, so many choices. Run more gear? Re-purpose a panel or two for another purpose? Become a 10% psoc pioneer like 40-60 soc?

I catch a few AFL games on Saturday nights here, and forgot about the seasons - people somewhat bundled up in the stands, sun going down at 5:30p local or so. Looking forward to the Grand Final in October.

[bungawalbyn]

AFL fan, cool. My team is Collingwood. Unfortunately they are not having their best year. I may be biased having grown up in Melbourne , the home of AFL, but I think it's the best "Football" game to watch. Mostly.

[solar pete]

AFL fan, cool. My team is Collingwood. Unfortunately they are not having their best year. I may be biased having grown up in Melbourne , the home of AFL, but I think it's the best "Football" game to watch. Mostly.

Mad Port Adelaide fan here, we are having a bad run this year, oh well there is always next season

[Living Large]

I'll leave the lead to other threads, but just goes to show you I'm no lifepo4 fanboy, but man, can I relate to your wow factor. Everyone who actually goes hands-on goes through it.

This is actually something I expected based on the research I did on this site. When I saw the consequence of low insolation in my area, I envisioned my generator running 6-8 hours a day, which is totally unacceptable to me.

My estimates for an LFP solution were 2-3 hours. To me, that is a WOW difference. Having a stable source with a flat discharge curve just clicked for me.

I guess I am arguing that I did in fact see a wow factor in my spreadsheet and in print. The price is a wow factor too, a negative one, but I am willing to pay the premium for usability and lower maintenance and peace of mind. Others may find more peace of mind with keeping half the cash in their bank account - which I can understand. Each to their own.

[PNjunction]

For me the biggest wow factor was from an operational standpoint of not having to strive charging back up to 100%, and also that I can LEAVE a project with a discharged battery (not all the way mind you) and walk away provided I have no parasitic loads. In fact, that is actually GOOD for it.

In your case, provided you do your power budget properly, on a practical level with a genny, if solar isn't cutting it for that day, you switch off the Pb mindset, and let the genny put back what you think you'll need the next - stopping when you just dang well feel like it - if autonomy or lots of spare reserve are not in the plan. Just put back what you think you'll need or desire.

But that is just for that day - you can easily switch gears operationally depending on changing circumstances.

THAT operational flexibility is what really turned me on to lifepo4. When I try to do that with my beloved pure-lead agm's, I am always facing a corrective action of some sort to pay the deficit-charge piper.

[Living Large]

For me the biggest wow factor was from an operational standpoint of not having to strive charging back up to 100%, and also that I can LEAVE a project with a discharged battery (not all the way mind you) and walk away provided I have no parasitic loads. In fact, that is actually GOOD for it.

In your case, provided you do your power budget properly, on a practical level with a genny, if solar isn't cutting it for that day, you switch off the Pb mindset, and let the genny put back what you think you'll need the next - stopping when you just dang well feel like it - if autonomy or lots of spare reserve are not in the plan. Just put back what you think you'll need or desire.

But that is just for that day - you can easily switch gears operationally depending on changing circumstances.

THAT operational flexibility is what really turned me on to lifepo4. When I try to do that with my beloved pure-lead agm's, I am always facing a corrective action of some sort to pay the deficit-charge piper.

I have considered this flexibility as well, and other factors as the conversation proceeded over the months. Pretty much everything I saw I liked. Parasitic load was a concern to me as well in leaving for an extended period occasionally - but I never got far enough to address it. Not yet.

[PNjunction]

Parasitic load was a concern to me as well in leaving for an extended period occasionally - but I never got far enough to address it. Not yet.

We know that floating stirs up a lot of angst here, and rightly so when the voltage is held high. If you must guard against parasitic draws, then a float, um "parasitic guard" well under full charge, like 3.375, maybe 3.36v per cell will hold it at bay without actually overcharging. The idea here is to avoid coming back to a bank that has triggered the lvc requiring time you may not have recharging it. This voltage is not written in stone, so pick your poison (BELOW 3.4v please) of what soc level you'd like your parasitic guard to activate.

Ideally, just check and design against parasitic loads as it is never a good idea to leave a battery unattended for long periods of time no matter what gear you use. That's just me. Overnight with me around is one thing, but I don't even leave stuff unattended over the weekend.

[bungawalbyn]

A little off topic.

Now that I have batteries with very low resistance, it's interesting to watch the ammeters on a day of scattered cloud.

In constant bright sun at present late winter angle, my (Now 7) panels charge at about 55amps max. With bright sunny breaks in passing cloud, I've read 80 amps on the meter. I figure this must be due to the panels getting hot in constant sun but staying cool with scattered cloud. That's a big difference.

I guess if one could find a cost effective method of keeping the panels cool it would make a big difference to their real world efficiency.

[PNjunction]

Heh, many of us thought about external cooling schemes that always fail, are impractical, or just too expensive (both power and financially) to do the cooling.

Also consider you may be witnessing "edge of cloud" lensing affects, which tends to have the same big but temporary jumps in current. That's why most CC's have a "nominal" and a peak rating for current.