harbor freight solar controller

[danlaurajacobson]

I have the solar kit set up and I am just trying to figure out the controller. After some significant time on hold with the "technical questions" people, I gave up and figured someone here would know.
The panels charge the battery during the day, but seem to discharge the battery as the light fades. I was thinking that the controller prevented this, but yesterday the battery began the day at 11.7v and reached 12.6v during the afternoon. Then, as the sun got lower, the voltage dropped down to 12.0 and stopped there. This is well below the 13 to 14.5v that the instructions say indicates full charge.
It does appear that the controller stopped the discharge at 12v, but this is lower than I want, right? Does this mean that the controller should be switched off when the battery is at peak voltage (afternoon) so that it does not discharge every evening?
thanks!

[rreidnauer]

What you are seeing is not discharging of the battery. It is normal for a battery to show a slightly higher voltage when a forcing charge is applied. When there is no charging, the battery voltage will drop to it's "resting voltage." When you appy a load, the voltage will drop further. Remove the load, and you should see voltage come back up to a resting voltage.

Now, I am concerned by your resting voltage, as it is low. 12.7 should be the full resting voltage. I'm thinking either you have too much battery for your solar array, your electrolyte level is low, or you have a damaged battery. What is the wattage of your solar array? What is the amp.hour rating of the battery?

[danlaurajacobson]

thanks for helping. The solar array is the 45 watt harbor freight kit. I have not altered it at all. The battery is a brand new marine deep cycle rated at 105 ah. I use the battery for my camper lighting etc.

[donjuedo]

Rod is right. The resting voltage really should be higher. In the other copy of this thread, you said there is no load and the charging has been going on for days, with no improvement. I'd bet on the low electrolyte or damaged battery Rod mentioned.

Peter

[danlaurajacobson]

OK we'll try to stick to one thread. Sorry that I did that.

I will throw a regular charger on the battery to see if it will take a charge and rest at a higher voltage. I really appreciate the help.

Dan

[loghousenut]

What meter are you using to test your voltage? Are you sure it is accurate? What does it read when you take a read on your car battery? Have you tried charging the solar battery by jumping from your car?

[danlaurajacobson]

I'm just using the digital display on the solar controller. My main question was in regard to the voltage rising during the sunny day hours, and then dropping in the evening. The previous explanation makes sense because the panels are no longer contributing and the battery drops back to it's stable "resting" voltage. You're right, the controller may not be accurate. I will take a multi meter with me to confirm voltage.

[rreidnauer]

Your solar array is rather largly undersized for the battery, but without any loads should be capable of bringing the battery up to full charge.

First off, if your setup is simply being used as a maintenance charge for something like an emergency backup sump pump or something, your system is sized fine. But typically in situations where you'll be using power from the battery bank daily, you want the charging rate of your array to be somewhere around 15 to 20 percent of the amp-hour rating of the battery bank. In your case, I believe you are around 2.5% The theory goes, if you use battery power during the evening, to where you drain the battery bank to 75% of capacity, the next day, a few hours of sunlight (at 15~20% charge rate) would restore the batery to full charge.

[danlaurajacobson]

The set up is not used daily. This is for a camper on vacant land where usage will be mostly on weekends. The battery is used mostly for lighting in the camper and a small tv now and then. the solar system should be able to keep up if charging during the week... right?

D

[rreidnauer]

Yes, using the panels for just a maintenance charge alone will work fine. I keep a 50w panel on my trailer as well. I don't know how old your battery is, or how well you've kept it charged. If it's been neglected in the past, (remained under-charged for extended periods) it may be sulfated, and would explain why the numbers are low.

Speaking of the camper, while you may or may not have read of my process of rebuilding my trailer in another thread, I have been converting lighting over to energy efficient fixtures. I don't like the color of typical fluorescent lights, but the warm white CFLs are very good for color and lumens per watt. I have been replacing the 12v ceiling light fixtures with standard 120v fixtures, but wired to the 12v. You can get 12v CFLs with a regular screw in base. They are sized bout the same as a regular bulb, so they'll fit in about anything. At 13 watts, they use about a quarter the power. They aren't cheap though, at about $9 a piece.
I also swapped out the 12v undercounter fixture for a 120v four light xenon strip light. (clearance special) Again wired into the 12v, and I put in these little, warm white surface mount LEDs. At only 2 watts a piece, I'm getting 140 lumens each, which lights my countertop with plenty of light. I'd compare it to at least 75 watts of incandescent light.
I still have a few lights to change out, and I'd love to find some way to make the furnace blower motor more efficient, as that's the biggest power hog now.

[danlaurajacobson]

Yeah, I never did figure out a way to run the furnace on batteries. I ended up pulling it and building a small (8x12) attached room with a wood stove. I also use one of those indoor-safe big buddy lp heaters for the bedroom. Between the two, I have stayed comfortably in the camper down to 0 degrees F.