Shore Power to Solar input using a solar controller to charge two batteries?

B

Bear in NM

Adventurer
I do not post here a lot, but have used this site to empty my wallet on many occasions. That's a thanks.

I just completed a portable solar generator suitcase. Have upgraded my truck with dual batteries. Solar is nominal 12 volt system. I am at the part now where I need to decide whether I can use my solar suitcase with AC to charge my batteries?

In my suitcase, I have 2 35 amp hour batteries, in parallel. On the left side of my platform, I have a Morningstar 20 PMW that is wired for solar input, wired to the suitcase battery, and wired for an Anderson plug on the load side, for charging small devices. The middle has two posts, positive and negative, for direct battery connections, like inverters. On the right, I have a Sunsaver duo PMW charge controller, solar in, one battery output to the suitcase batteries, the other to an Anderson plug so that I can connect another battery, be it either of my truck batteries. All three sections are independently fused and switched.

I have boned up on the proper charging needed for all of my batteries, and they are all AGM. The two controllers I have installed, are suited for proper AGM charging, from panels. I understand that AC charging any of my batteries, I need a proper 3 stage charger, for the deep recharge. But, as both of my controllers are set up for high volts and reasonably high amps, in my simple mind it seems that I might only need a "dumb" ac to dc charger, plugged into either solar input, and let the brains of either controller handle the battery charging? Maybe a simple 14 or 15 volt converter running at 10 or 15 amps for a quicker battery top off?

If this can work, then the size would be helpful, as well as the fact that I already have charge controlling with my Morningstars. But, this seems so simple, I am sure I am missing something important.

Thanks,

Craig
 
dwh

dwh

Tail-End Charlie
Using an ac->dc converter (a.k.a. power supply) on the solar side is the method recommended by Morningstar when bench testing their charge controllers (PWM or MPPT).

http://support.morningstarcorp.com/wp-content/uploads/2014/07/TS.TST_.Bench_Testing.01.EN_.pdf


So...go for it. I would recommend a regulated dc power supply with a voltage of 15v or more and as many amps as the charge controller can handle. The PWM circuitry (the Duo is PWM as well) will handle regulating the voltage to the battery side.

I would use the Duo for a couple of reasons:

1. As I recall, it's rated to 25a, where you say your other charge controller is a 20a unit.
2. It can be rigged to charge/float both the internal and external batteries from a single input source.
3. With the interface and software available from Morningstar, it's programmable, so you can configure the bulk/absorb/float set points to whatever your batteries manufacturer(s) recommend.
 
B

Bear in NM

Adventurer
DWH,

Thank you most kindly. I did look at the support documents on the Morningstar website for the Duo, but either missed that one, or the logical deduction, use the bench test to answer use. Very clever of you. Yes, the plan would be to use the Duo for the bulk charging, if on AC. I did attempt to download the software for the custom setpoint software, but my virus software cancelled the download due to "seeing" a virus in the download. I have not got back to sorting that out.

You are spot on, the tradtional Sunsaver is 20 amps, and the Duo is 25. Now I can use the money saved on a ac charger on additional solar panels.

Since I have your ear, Morningstar specifically says "no" to hooking up a dc to ac inverter on the load side of the PWM controller. I have no need to do this, as I have fused posts in my suitcase, but I have been wondering what the electrical reason for this might be?

Thanks again, and I am really having fun with all of this.

Craig
 
dwh

dwh

Tail-End Charlie
The "load" circuit for most charge controllers is usually limited to a 10a load. That's 10a @ 12v or 1a @ 120v. Either way, it's 120w. Good luck finding an inverter less than 120w. A typical 400w inverter would be drawing AT LEAST 33.3a on the 12v side [EDIT: Well..it would if you were supplying a 400w load.]


Also, the load circuit is almost always controlled by a LVD (low-voltage disconnect). So it's suitable for powering a radio, or a night light, or the control board for an electric gate, and the LVD will automatically shut off the load before the battery is totally dead.

In other words, the "load" circuit on a solar charge controller is pretty much useless most of the time for what most people are doing.
 
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B

Bear in NM

Adventurer
dwh,

Thanks again. I had not actually thought about the load side maximum amperage. It's a little hard to gather that info from the tech files or data sheet, but it looks like my 20 amp model specifies the same 20 amps on the load side. But either 10 or 20 for the actual load circuit, yes, it is pretty low. The plan for this controller was to simply plug in small devices like phones or my amplified speakers for my music. I'll also be setting up dc lights for my truck tent or up at the cabin. I have a Samlex 120 pure sine ordered, which I will mount in my suitcase as well, again for low amperage type devices. I also have a Goal Zero Sherpa 50, with a 75 watt inverter. The big stuff will be set up on my second truck battery. I already have quite a few of the cheaper high wattage inverters that I have been using, over the years.

I know the usual solar method is to identify the loads, then spec out the solar. I sort of started in the middle, by building the portable control center with minimal battery capacity, and adding a second truck battery. I should be able to now add a battery bank here at home, for back-up, and match up with panels. And still have the same controller center work for my portable needs. Next summer, I will start looking seriously at dc loads for camping.

As to the Duo controller, for now the factory presets look pretty close to the spec's for my aux truck battery. But the meter bus is less than 50 bucks, so I am pretty sure I will be adding that. When your a geek, it is hard to resist software.......

Craig
 
whitenoise

whitenoise

Adventurer
dwh said:
Using an ac->dc converter (a.k.a. power supply) on the solar side is the method recommended by Morningstar when bench testing their charge controllers (PWM or MPPT).

http://support.morningstarcorp.com/wp-content/uploads/2014/07/TS.TST_.Bench_Testing.01.EN_.pdf


So...go for it. I would recommend a regulated dc power supply with a voltage of 15v or more and as many amps as the charge controller can handle. The PWM circuitry (the Duo is PWM as well) will handle regulating the voltage to the battery side.
Click to expand...

I think the key is where it says in the document "DC power supply, current limited". If you did not have this feature, I figure you'd be burning up power supplies on a regular basis. Has anyone found a good current limiting DC power supply for a reasonable cost? I like the OP's solution, it is elegant esp. if you mount the charge controller onboard. Then all you need to do is wire a DC plug accessible with the hood closed, plug in solar or AC as needed.
 
B

Bear in NM

Adventurer
whitenoise,

I spent a little time trying to research the power supply, per dwh's suggestion. In the test protocol document, they went as high as 5 amps. Laptop charging bricks are all mostly rated at 19 volts and a couple of amps. I found an HP #adp230db d, charging brick, which is rated at 19.5 v, and 11.8 amps. Then there are the DC power supplies as used in the document, that from what I have looked at, allow for exact control of both the volts and amps. These are typically found at 5 amps tops. I found a couple that go to 10. Both the HP laptop brick and the desk top power supply look to run a shade less than a hundred dollars, with the laptop bricks being pretty small, compared to the desk top power supply. I also found a few places that would build a spec'd power supply, but I did not actually price a build. Thinking that it might be fairly expensive. I think I am on the right track, but not sure.

I have an inline automotive fuse holder in my solar cable. I also have one of the 20 dollar fuse insert amp meters that I can plug in. Both of my Morningstar controllers appear to limit the incoming amps, based on load. If I plug in a couple of small loads in usb sockets, the meter shows only about 0.6 amps being "pulled" from the solar panels. If I add to the load, I am seeing more like 2.5 amps, which is the max from my 52 watts of portable panel. This all had me stumped at first, thinking I had a problem in my panels, as I was only getting the 0.6 amps with a small load, thinking that I should still see 2.5 coming out of the panel. My ignorance of dc power is showing, but I am testing and learning. I think this is telling me that the charge controller limiting current, as needed.

While my suitcase is on the large side, as it contains 75 ah worth of battery, I do have my truck wired with plugs in the cab, direct to my aux battery, so I can do everything from inside the cab. I am also setting up to run from my tailgate area (bed tent) for both truck batteries. My 7-pin trailer plug is constant power/connection to the starting battery, and I made an anderson to 7-pin for that side. I have the parts for a 1 gauge cable and anderson that I will be running to my aux battery, again from the back of the truck. All of this should have the cat thoroughly skinned. I hope......

Craig
 
B

Bear in NM

Adventurer
Thank you sir, I get it now. No load, no amps. duh.. Both of my Morningstars look to consume about 0.03 amps (or smaller), waiting to charge, or smoke. Been a lot of years since I smoked anything electrical, but I can smell it in my minds eye ;^)

Craig
 
B

Bear in NM

Adventurer
Just an update. I stopped by my local PC shop, the one that I use for building my work computers. I asked the guys if they had a box o'bricks in the back, where they collected power supplies from PC's that bit the dust. I explained what I was doing, and the guy was intrigued. We found a 20 volt, 6 amp brick, the highest amp one they had. Got it for 10 bucks. I modded the output plug for my anderson connector, squinted my eyes, and plugged it into the solar input......

At start up, I saw about 8 amps cross my meter, then it settled down to just a couple. The volts at the plug were just a tad over 20. My suitcase batteries were not horribly drained, so I did not see much above 13.85 v going to the battery. I need to really run them down, and watch the volts and amps to see if this is going to work, for charging. I am thinking that the brick probably has some "brains" in it to limit amps, as the demands for an expensive PC probably differ from a big dumb battery. maybe it will work, or maybe I have a spare 10 dollar trickle charger.....

Craig
 
B

Bear in NM

Adventurer
Verkstad,

Yes, the PC guy said the same thing about monitoring for heat, although I would have done that anyway. Hence the reason I had an amp meter on it. I ran the idea past the tech at my local solar company, and he said that it all sounded good in theory, but would not give a thumbs up, outright. I am actually sipping my coffee right now, and chuckling to myself, at your post. Who, me, trying to do something a little different :sunny: It would seem that in talking with my local solar guy, that my portable charge controlling suitcase is a bit outside the box.

whitenoise, a most excellent read. I did try searching this question on the web, and most certainly did not find that thread. looks like I need to expand my research to the more traditional RV charging methodologies. I am not trying to cheap out here, but trying to invest correctly. Different battery makers "suggest" different (read expensive) chargers, and my thinking was a more generic (also probably expensive), find an alternate charging source that could use the brains of my two controllers and be used with different makes of batteries, over time. The PC brick was more of a cheap test. I like the idea of a proper bench DC source as was suggested by dwh, as this device could be used for other chores. It seems that the typical less than 100 dollar bench supply might be the type that was fried in that link.

I have certainly learned from the good folks here that while batteries may be dumb, they can be very picky about how they are fed......:)

Craig
 
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