diy solar

diy solar

Old panels need to go, need suggestions for new ones

Alpha-y2k

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Apr 11, 2020
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So I have a 3 yr old harbour freight panel kit.
The solar controller that came with the kit recently gave out. So I bought a Renogy 40a MPPT solar controller and I love it.

Renogy 40A 12V/24V Auto MPPT Solar Charge Controller with LCD Backlit Display w/ Temp Sensor Fit for Gel Sealed Flooded and Lithium Battery, Rover Elite https://www.amazon.com/dp/B083BFYJJG/ref=cm_sw_r_apan_i_K86CS62YVRX7DJDQ8FB1

Rewind to 3 yrs ago I was brand new at solar, had no clue about it so so I bought this kit, hooked it up, and went along my way without the bothering to check specs, if it was working as it was supposed to, alli knew is it worked and that's all that mattered so I didn't bother checking anything. Rooky mistake.

Fast forward to today and I've learned a lot, especially in the past week, things like ah, amps from the panel, voltage and testing all of them etc...
That being said, with the new control box I have been keeping a very very close eye on things, and to my surprise I was sorely disappointed in the results.

I have a harbour freight 35ah agm deep cycle battery I'm using. I am not getting topped off at all to 13.1/13.2, my incoming at most is 3.0amps and that's in the hottest part of the day around 1-3, after that it starts going down drastically in amps. We are talking by 5pm, still plenty of light out I'm getting more like max of 1.5, and it gets worse down to .08amps incoming ?.

I seem to float at 12.8/12.7 but today I noticed it at 12.4 now. Not good to run clip fans on at night, even if they are only drawing .08 amps, a bit uncomfortable at running the battery down at this point.
So that given, I have everything I need except for panels.

I am looking at a dual set 100watt x2
Renogy brand at home Depot.


So any thoughts on these panels?
 
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I am looking at a dual set 100watt x2
Renogy brand at home Depot.


So any thoughts on these panels?
I can't comment on their 100W panel but I very recently upgraded a junk 7W starter-battery panel with Renogy's 50W panel with their 10A controller, and I could no believe how many amps I was getting out of this package. IIRC I was getting almost 3A around 11am. I am coming back to the cabin today and I expect to see the batteries all full.

I can't do the exact math for you, but i think you'll get that 35 Ah battery topped off with the (2) new 100W panels without any problem.
 
Used solar farm panels are available if you have a truck and can drive for an hour or two to get some. 250watt are going for about $65-$75 each and typically produce about 80% of rated power, being used. They are large, so if you are mounting on an RV they wouldn't be ideal.
 
I recently lost 4 agm batteries and your charging problem actually may be indicating your battery is giving up. If you have an alternative way to charge it you might want to check that out before blaming the panels.
 
Used solar farm panels are available if you have a truck and can drive for an hour or two to get some. 250watt are going for about $65-$75 each and typically produce about 80% of rated power, being used. They are large, so if you are mounting on an RV they wouldn't be ideal.

I have been looking around Indianapolis area for a while now for these and am not having luck. I can drive to get panels. What google-fu are you using to find them?
 
I have been looking around Indianapolis area for a while now for these and am not having luck. I can drive to get panels. What google-fu are you using to find them?
Try Google "craigslist Indianapolis" and then search in their page. Maybe try some other nearby locations.
 
You have a 40a mppt controller, why not buy a used residential panel? You can sometimes buy them for $200 for 400 watts. Then buy a cheap 100ah deep cycle battery. If it hasn't been getting full, may already be trashed.

What is your application?
 
Okay quick update.
I tested all four panels at the panel.
One was at 1.8a, the other three were at .08a. Mind you this was at 6:30 pm and overcast, but still should be better than even 1.8, maybe 2.0 at the least. DEFINITELY should be better than the .08a. Any panels doing that little, may as well have no panels at that point. So it's most definitely my panels.

Time for a replacement

Just as an fyi for those who don't have the harbour freight 100 watt kit, make a note, these are not for longevity. I've had them 3.5 years and having to replace them.
If you but these just know they are not for the long haul.

On another note though, I have looked at the 100watt single panels, and those surprisingly have good reviews. A lot of people saying they are getting upwards of 6a incoming from a single panel, that's pretty impressive. A couple of the videos I saw were definitely overcast cloudy days, no sun in sight, and they were still pulling in 5.8a - 6a.
I just hope my ole 35ah battery can last just one more night.

I'll post back when I get everything up and running with results.
 
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Final update:
I bought two of the harbour freight 100 watt monocrystalline solar panels, $99 each on sale, normally $129 each.
Have them hooked up in parallel about an hour ago, and sun was shining it was 11am no cloud cover and I read 8.5 amps incoming. Over the next hour the clouds rolled in, covered the sun, and with full cloud cover am reading 20 volts, 5.4a incoming.
With the fun peeking for a few mins now and then I read 7.5a - 8.0a 21v incoming.

I'm pretty impressed honestly, and now I'm a LOT more confident my battery will charge up and not have issues with going dead.

This is the first hours, but so far I'm impressed, especially pulling 7-8a on a semi cloudy day.
I'm not exactly sure how long these will last, but my initial first impression are very good, much better then the 100 watt kit by far.

Fast forward a few hours it's now 2pm. Intermittent sun shining threw the cloud cover, and I've been checking very intently at the controller box, I've hit a high of 9.7a incoming. It goes up and down if course but my lowest has been 3.8a, my highest so far is the 9.7a.
Even at the lowest, that's double what my old panels were giving me.

If anyone is interested I could check in from time to time giving results, if not I won't bother.

I will say again, I'm pretty impressed right now.
 
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