I bought a small 20 watt panel from Amazon with an external controller. I have it hooked up to two 12V 12AH batteries in parallel for a couple of days now. At first the batteries' charge were too low for the controller to detect so I had to bring it up high enough for the controller to 'see' them. That's all good and working but one thing I'm noticing is that at night when the solar panel disconnects, the battery voltage is always at 12.6v. Will this change over time?
What charge controller do you have and what is the battery load?
Not quite sure what you are asking...
12.6V is actually what a 12V battery should read when it is fully charged. It may read higher than 12.6V while it is being charged, but after a few hours, it should settle down to 12.6V. Like all batteries, it will slowly self-discharge over time.
1 Like
It's this kit from Amazon, Topsolar 20W - load is a couple of wyze cam.
@dean - I wasn't sure if it should register more than 12.6V
If this is a true PWM 3-stage charger it should get to >14V during the absorb stage then drop down to >13V in float, assuming that panel is large enough to even get it out of Absorb, which it might not be depending on the battery size, load and hours of sunlight. Try connecting just on 12V battery and the Wyze cams on the Load side of the controller. See it can get just one battery into absorb.
I think my used battery may be the issue here. I have another set of the 12AH ones that I know are still good but not new so I'll set that up after it's pulled from service. I hooked up a Shelly uni to the load without the cameras just so I can do some logging on google sheets.
Almost certainly, since you first said:
It sounds like those batteries sat discharged for a while. They're probably sulfated, which drastically reduces their capacity.
You're right, they were spares that I had sitting on the shelves for more than a year possibly longer that was an exchange from an Amazon purchase. They were probably questionable to begin with and then sat for a long time.
Just updating thread... the new set (older battery) is working much better than my first try. I let the wzye pan cam record continuously last night and still had 12.2V this morning.
Finally got some logging going with two batteries in parallel. I'm curious to see if one battery can handle just one of the wyze pan cam so I'll remove one of the battery over the weekend.
2-battery 12AH setup
I understand that some batteries will have issues if their voltage goes too low too often. I had a setup a while back with AGM batteries (before I had my Shelly Uni to monitor voltage) and I ended up killing them by dropping the voltage too low too often. Not sure how low I brought them though… Something to keep in mind!
Thanks! My setup has been holding up well so far. One battery getting charged during the day and powering my wyze cam pan 24/7 
1 Like
Good advice, 'low' is ALOT higher than many realize. Like 12.2V DC
I remember watching this video (wouldn't necessarily recommend it unless you are into deep cycle batteries) where an an engineer that works for Odyssey basically said their batteries will last A WHOLE lot longer cycling only 50% "depth of discharge". There is a reason a lot of solar charge control units are set to shut down the load around 12.2V DC
Video highlights at 13:00 on and a bit at 39:00
.
.
More on this from another source here:
1 Like
According to the info I posted in the prior post, those hours from 18:00-09:00 in your graph will be taking your batteries to an early grave if that's how the overnight load is continuing to drain them deeply below 12.2V DC.
I'm dealing with a similar task to get the "solar panel size + battery size + load balance" right for an application.
It's been working out great... I only had one time where the controller shut down the load due to a couple days of very cloudy weather in the area. I have the batteries back in parallel, the single battery setup didn't last very long. The above graph shows battery drain with my wyze cam pan set in continuous recording. Lowest level was 12.09v.
Interesting, you're just going to have to see how long that battery lasts but depending on what "time of day" is most important to you for coverage....I'd be tempted to weigh the benefit of having full 24/7 recording and maybe giving up some hours of constant recording between the hours of 09-16 (using motion triggered or lowering the frame capture rate) so that you stay above 12.2V between 00:00 and 07:00.
That might make the difference between the battery lasting through next winter or not.
Doesnt look like it ever reaches the absorb charge voltage which is typically >14v for lead acid. I have a similar situation where I only have a 100w panel which is shaded half the day trying to keep up a 70ah lead acid battery with some sensors and a security camera load. Its been alive for a couple years in the shed but getting worse. Low voltage disconnect is around 11.5V I think. I got the battery's for free from a UPS swap out so rolling with it..
I think this is what you're referring to, it regularly reached this when I didn't have it on 24 hour record mode. Like @PunchCardPgmr mentioned earlier, there's room to mess with the recording time, just haven't played with it much.
Here's my setup in the corner of the backyard 
, it might get moved to a more permanent location. Right now it's a test to see what other things I can do with it.
1 Like
I'm happy if mine gets up into 13.5V ball park but that's a result of poor design. Two old old 10watt panels which on average show .6 amp charging through the controller and .5 amp out to the daytime load I have (DC fan pulling hot air out of a small greenhouse). Add to this an ambient temp of 90F when the sun is pushing hard and I clearly am not doing the battery any favor whatsoever.
So, on my to-do list is to get the battery out of that space, get some better mounting for the panels so I can optimize the sun angle and maybe to put in an old Odessy car battery that may not have what it takes to start the car but might do the job for what I need in a solar system. Actually, the panels on the market today are probably worth the upgrade. Ought to add that to the list, one new 20w.
EDIT: Well, this thread has been good motivation to get out there and tend to some of this stuff. Better panel orientation (beyond my makeshift test positioning) made a significant difference in voltage and amperage coming from the two old 10w panels. I'm now pulling in about 14VDC mid-day and 1.3 amps, well over twice the daytime Ioad I'm expending. It's also worth noting how significant a little dust is to efficiency.
@eibyer that nice voltage graph is coming off the solar controller hook up and not anything HE+Zigbee/Zwave right ? ...Or is it????
