Solar charge controller for car battery tender?

[n8n]

Good morning

For a while now I've had a Harbor Freight solar panel and charge controller in one of my seldom used cars that has a high key off current draw. I think the charge controller has packed it in however. I don't like it anyway as it doesn't have any kind of readout, just LEDs to indicate charging and high/low voltage. Anyway I went to move it to another car yesterday and the "charge" light wasn't lit. Couldn't find a multimeter quickly but will check it out more thoroughly.

In any case I need another one of these setups so I'm going to need another charge controller anyway. Does anyone have a recommendation for a good charge controller that would work for my use? I'm basically using a small (10-20W) solar panel to act as a battery tender for a car that can't be parked by a receptacle. Thanks!

 

[whateg01]

I would like to do something like for my trailer. There are solar chargers on Amazon but I don't know how well they work. Maybe as good as what you had before?

 

[n8n]

this is the one I have

https://www.harborfreight.com/7-amp-solar-charge-regulator-96728.html

someone on CPF recommended this one

https://www.amazon.com/Newpowa-10A-Controller-Compact-Adjustablefor/dp/B09MVYXQ1P/?tag=atomicindus08-20

which looks more like something I'd prefer and the price is right, just looking for specific product recommendations otherwise I may order the one in the second link and give it a try.

 

[n8n]

Well I ordered the Amazon one but I apparently need two; I got home and it was sunny out and the panel was putting out 15.something volts but the charge controller was not charging. Verified all connections to battery and panel and still no bueno. Got the battery in landlady's car on a recond cycle on my CTEK 7000, but now I apparently need solar in both that car and my BMW. Fortunately the battery in the BMW had enough charge to start it yesterday, it's 6 years old so already on borrowed time.

 

[kerrynzl]

@n8n
I used a Deltran battery tender for a solar panel.
I also purchased a C-Tek extension cable and cut the end off to add a European car plug [approx 10" from the end].
The end piece that I cut off was attached to my Deltran solar controller .

Now everything can Mix-n-match



Here is the European car Plug [This was spliced onto the C-Tek extension cable]



Here is the C-Tek connected to the Euro car



Here is the Deltran with the C-tek plug connected to solar. [In my tow hack] I use a Cig Lighter adaptor that came with the C-Tek battery Tender



I can swap the Euro car over to Solar or the Tow Hack over to the C-Tek plus I also have my trailer battery hard wired with a spare C-Tek pigtail adaptor.
the C-Tek also came with a pair of jumper clamps that I can also use to adapt my 57 Chevy to solar or C-Tek


I'm into the whole setup for less than $120 [2 chargers, solar panel ,multiple adaptors that interchange]

 

[n8n]

Coming back to this after a few months of use.

I purchased two solar controllers, this one

30A 12V/24V PWM Flush Mount Solar Charge Controller - Negative Ground

OVERVIEW For those committed to off-grid living, this HQST 30 Amp Flush Mount Solar Charge Controller allows you to keep your battery powered via solar panels wherever you happen to be - traveling by RV or truck or maintaining a convenient and reliable solar-powered solution for your cabin or...

hqsolarpower.com

and this one

https://www.amazon.com/dp/B09MVYXQ1P?tag=atomicindus08-20

With each, I am using this Harbor Freight solar panel thrown on the dashboard

https://www.harborfreight.com/7-watt-solar-panel-kit-64801.html

Prior to buying the two controllers I mentioned above, I was using this guy

https://www.harborfreight.com/7-amp-solar-charge-regulator-96728.html

which appears to also be sold under the "Schumacher" brand elsewhere.

So, to recap: Wanted basically a battery maintainer because at least one of my cars has a ~6 year old battery and I'm trying to get as much life as possible out of it. I do not have the ability to run a cord to the cars as they are parked on the street (working on that issue, but it's what I am working with for now). Trying to get a solar solution working so cars will always be ready to start even if having sat for a couple weeks. One (BMW, same car that has the old battery) also has high key off current draw so this seemed to make sense.

Problem: nothing has worked. The Harbor Freight charge controller failed fairly quickly, and the two others share a problem. I was hoping to be able to simply be able to throw the solar panel on the dash, hook it up, and be able to come back a week or more later to a charged battery. However they do not seem to work this way. What is happening is that the panels will charge the batteries during the day, but it appears that at night when the sun is down, the controllers draw the battery down so that in the morning the battery is actually lower than it would have been without anything hooked up. So, over a period of several days, although the solar panel is charging during the daytime, my setup is resulting in the car battery draining down faster than if I had nothing at all hooked up.

I am sure that the solution would be either a larger panel (which I don't really want) or a less sophisticated controller that draws less current to operate (similar to the HF/Schumacher one that I tried initially). Any ideas anyone?

 

[n8n]

@n8n
I used a Deltran battery tender for a solar panel.
I also purchased a C-Tek extension cable and cut the end off to add a European car plug [approx 10" from the end].
The end piece that I cut off was attached to my Deltran solar controller .

Now everything can Mix-n-match



Here is the European car Plug [This was spliced onto the C-Tek extension cable]



Here is the C-Tek connected to the Euro car



Here is the Deltran with the C-tek plug connected to solar. [In my tow hack] I use a Cig Lighter adaptor that came with the C-Tek battery Tender



I can swap the Euro car over to Solar or the Tow Hack over to the C-Tek plus I also have my trailer battery hard wired with a spare C-Tek pigtail adaptor.
the C-Tek also came with a pair of jumper clamps that I can also use to adapt my 57 Chevy to solar or C-Tek


I'm into the whole setup for less than $120 [2 chargers, solar panel ,multiple adaptors that interchange]

I like it. I also have a CTek charger so your solution is nice for me.

Do you have any issues like I describe in my last post, or does it seem that this is actually keeping your batteries topped up?

 

[duneslider]

Just curious but how are you determining the battery is charged and not charged in the morning? Are you taking actual voltage readings at night and comparing to morning? What are your voltages at those two times? Don't use the display on the controller either, take a reading off the battery with the controller/panel disconnected to see what is actually happening at the battery.

Charge controllers should list what their consumption is when not charging and it shouldn't be that much. Is it possible the solar panel is actually not producing enough to charge the battery in a day and it isn't actually ever getting charged.

 

[kerrynzl]

I like it. I also have a CTek charger so your solution is nice for me.

Do you have any issues like I describe in my last post, or does it seem that this is actually keeping your batteries topped up?

The battery in my Falcon Hack was purchased in 2016 , load testing is showing that it needs replacing . But I've had it on the solar for a few years and it still starts straight away . The only issue was the battery drain due to lack of use ,which doesn't happen with the solar controller.
It actually managed to crank over a faulty starter motor until eventually I replaced that

Cheap controllers will drain current.
The Deltran solar battery tender has an internal circuitry [diodes?] to prevent back-feeding.

The only issue I ever had was poor contact in the cig lighter fitting [a twist while installing remedied that]
The charger wasn't showing fully charged.

Disconnect the charger and use a multimeter to measure amp draw across the battery ground [computerized cars usually draw about 1.8a for approx 1 minute then between 20ma to 80ma when the computers go to sleep.
Then measure the current input of the solar charger [across the neg wire]

@duneslider Correct! If the solar panel is too small the battery won't fully charge and at night the parasitic losses of the vehicle might draw too much.

It could be a simple math problem of only 4-6 hours of too small input vs 18-20 hours of draw.

 

[rawen2]

Is the solar power charging the car battery through the cigarette lighter? Some cars disconnect the lighter when the key is off.

 

[kerrynzl]

Is the solar power charging the car battery through the cigarette lighter? Some cars disconnect the lighter when the key is off.

I rewired it so it is spliced to the brake controller 12v + [which is 12v constant via the factory tow package wiring]
You can see the brake controller beside the cig lighter port.



The cig lighter original harness was then connected to a motorcycle USB charger I installed inside the console.

These connections all have bullet connector plugs ,so it is easy to swap / restore back to original


If you ever need to do something similar, simply splice the 12v plug into the radio memory wire [usually yellow]
A 60w solar panel is only 5A
You can buy a C-Tek hardwire pigtail for a few $$$ if you want to do what I've done.

 

[n8n]

Is the solar power charging the car battery through the cigarette lighter? Some cars disconnect the lighter when the key is off.

Good point, but yes in one case but it's always hot, in the other I have it connected via alligator clips to the jump points under the hood.