Using a solar regulator with a laptop power supply

[pete_melb]

Hi again,

Thanks for the info. Makes sense.

I've decided to ditch the idea of using a laptop power supply.

Instead, I'm now using standard SLA battery charger (that does float charging). So, I now have the option of either using a solar panel (connected to a DC input socket), or a the SLA battery charger (connected to the 12V cigarette socket) which I can use indoors.

[PNjunction]

I have a 20W panel, and that works fine with the 2A battery.

Note that most small ups-style agm like your 2 or 7ah battery has a maximum current inrush of only about .25 to .3C. (C being the 20-hour ah rating, ie 2ah or 7ah for your batteries) If it isn't listed on the case, then use this value. That means that for your 2ah battery, the maximum current you should be supplying is about .6A, or 600ma. Your 20 watt panel is capable of more than this, about 1amp under the very best conditions, but with some inefficiencies of the controller and lower light levels, you may be just getting away with it. Your 7ah battery should only be able to handle about 2.1a inrush current max.

It's when I swap the 20W solar panel with a 19V laptop power supply that the battery starts to cook. Is the regulator supposed to limit the amount of current that reaches the battery?

Nope - it regulates the *voltage*, and the the battery (or maximum current that your source provides) is doing the current regulating. The CMP12 regulates the voltage you set and merely passes all the current that you provide. In your case, the laptop charger is providing WAY more than 600 milliamps, and the 2ah battery is cooking. Note that solar charge controllers are really meant to be used with solar panels, and not with other power supplies as inputs.

One thing you want to be sure of is connecting the battery *first* and then attach the panel. Otherwise, some controllers can get confused without knowing the battery as a reference first. Also, you cannot determine if a controller is working without having a battery attached. Merely using a voltmeter on the CC output terminals without a battery does not work.

I would now doublecheck that the controller isn't fried. Attach the 7ah battery, then your 20 watt panel, and follow it with a voltmeter during the charge procedure to make sure. It should not rise beyond 12.7v or so during absorb. Also, toss your 2ah battery - being cooked, it is no longer trustworthy for any project.

[Mike90250]

A charge controller is intended to take power from a CURRENT source like a solar panel, not a VOLTAGE source like a laptop supply. If you intend to continue to use a powersupply, you need a true MPPT controller, Morningstar makes some that are allowed to use voltage sources.

[pete_melb]

What wattage is the panel? a 12 volt 2 A battery cannot handle more than a 15 to 25 watt panel. The sound you heard was your battery cooking from way too much charge current.

Hi Sunking.

I have a 20W panel, and that works fine with the 2A battery.

It's when I swap the 20W solar panel with a 19V laptop power supply that the battery starts to cook.

Is the regulator supposed to limit the amount of current that reaches the battery?

Cheers,
Pete

[Sunking]

Hi again,

Things have been working well using the 12V 7AH SLA battery. Recently, I replaced that battery with a smaller one, a 12V 2A battery. When I then connected the 19V laptop power supply to the charge controller, the charge controller immediately cut off power to the load and then I started hearing sizzling sounds coming from the battery. I immediately disconnected the battery to be safe.

What wattage is the panel? a 12 volt 2 A battery cannot handle more than a 15 to 25 watt panel. The sound you heard was your battery cooking from way too much charge current.

[pete_melb]

Hi again,

Things have been working well using the 12V 7AH SLA battery. Recently, I replaced that battery with a smaller one, a 12V 2A battery. When I then connected the 19V laptop power supply to the charge controller, the charge controller immediately cut off power to the load and then I started hearing sizzling sounds coming from the battery. I immediately disconnected the battery to be safe.

Any idea why the charge controller is behaving differently, when the only difference is that one battery is rated at 7AH and the other at 2AH? It seems like the charge controller is passing way too much current over to the SLA battery. Is that what that sizzling sound could be?

I'm wondering whether it might be worth trying to limit the 19V laptop power supply to a maximum of around 1A.

Cheers,
Pete

[pete_melb]

Thanks daz.

All good now. I simply connected a single diode between the charge controller's + LOAD terminal and the amplifier. The amp is now getting 13.8V instead 14.5V and all is working. No more cut outs.

Thanks to all for your suggestions. Sometimes the answer is obvious, and thinking out aloud (i.e. posting on the forum) goes along way to solving the problem (and realising the obvious .

Cheers,
Pete

[daz]

So, at the end of the day, it looks like the combination of battery and laptop power supply both connected at the same time produces too much voltage for the amp to handle.

Glad to hear that you found the problem!

Assuming that's the case, is there any easy way to address this? Is 14.5V the 'official' maximum voltage for the CMP12 charge controller?

From the little "manual" that comes with it (I have used these before), 14.5V is it....there isn't any option to change the voltage.

Would the solution be to somehow limit the voltage at the LOAD terminal to keep it under 14V?

There are a few options that you could try, depending on what complexity you decide to go. The easiest may be to just use 2 power diodes (eg 1N4004 etc) in series for about a 1.4V drop (connected via a switch). Then when you operate just off the battery without the solar panel connected, you can disconnect the diodes (via the switch). There are many other ways...but the diodes are the easiest!

[pete_melb]

Just did some more tests...

I tried connecting the load to the battery terminals... same problem. Amplifier gets cut off as soon as I connect the 16V laptop power supply.

I measured the voltage at the LOAD terminals of the controller. With no laptop power supply connected, it read around 13V. With the laptop power supply connected, it read 14.5V.

It then dawned on me that maybe the amplifier was going into its own protection mode due to overvoltage. The more I think about it, the more this seems to make sense. I guess my original voltage measurements were somehow wrong, as I remember measuring only 1 or 2V across the LOAD terminals.

In any case, I connected the other power supply, that allows you to select the voltage. When I set it to 12V, everything worked fine. Amplifier did not get cut off. As soon as I bumped up to the next voltage (15V), the amp immediately cut off.

From what I know about these T-amps, around 14.5V is their absolute maximum, so I guess that explains it. The reason why it worked earlier on is maybe because the SLA battery wasn't fully charged, and probably caused the resultant voltage to be under 14.V (with the laptop power supply connected at the same time).

I bumped up the voltage a few more times until I reached 20V. In all cases, the maximum voltage across the LOAD terminals was 14.5V.

So, at the end of the day, it looks like the combination of battery and laptop power supply both connected at the same time produces too much voltage for the amp to handle.

Assuming that's the case, is there any easy way to address this? Is 14.5V the 'official' maximum voltage for the CMP12 charge controller?

Would the solution be to somehow limit the voltage at the LOAD terminal to keep it under 14V?

Thanks,
Pete

[pete_melb]

Hi Green,

I have a toggle switch that allows me connect / disconnect the battery from the entire circuit. I flipped it over a few times, but that didn't help.

One thing I forgot to mention... Before I even assembled all the components in the toolbox, I initially had all the bits and pieces lying around on the garage floor, connected to each other via thin jumper wires. The amp was actually able to play music while the battery was being charged via the laptop power supply. I connected the cigarette lighter socket, and was able to charge my iPhone at the same time as playing music. I also connected the voltmeter and associated momentary switch, and everything was working.

When I modified that toolbox and fitted all the components inside, I wasn't expecting any issues since it all worked OK during the 'dry fit' stage.

After assembling all the parts in the toolbox, that's when I first encountered this issue of the load (amp) being cut off by the charge controller. I was stumped. After checking all connections, solder joints, etc. I though the actual wire thickness may be the cause. Instead of using the relatively thin jumper wire I had originally used, I replaced it with thicker lamp cord wire. That proved to be successful. After doing that, I was able to get the amp to remain switched on and playing music, even after plugging in the laptop power supply.

For some reason, the original problem returned after a few days, and that's where I am now. No idea how the problem re-emerged. Maybe somehow related the battery's charge which had increased gradually over a few days of being charged by the laptop power supply.

Cheers,
Pete

[green]

Have you tried disconnecting the battery in order to get the CC to reset? I have one of those CCs and I remember having to disconnect the battery after I did something stupid (I don't remember what it was) in order to get it to reset.

[pete_melb]

Try connecting all loads to the battery terminals and not to the load terminals on the controller.
That will work and fix the problem

Hi Rich,

By connecting all loads directly to the battery terminals, doesn't that negate the management capabilities of the controller (i.e. it will then not be able to cut off power to the load to prevent the battery from over discharging)? I was under the impression that the load always gets connected to the load terminals, so that the regulator can control the conditions under which the load receives (or does not receive) power.

Can you maybe explain your suggestion, as I'm still just a newbie when it comes to electronics, etc.

Thanks,
Pete

[Naptown]

Try connecting all loads to the battery terminals and not to the load terminals on the controller.
That will work and fix the problem

[pete_melb]

Hi there,

Thanks for your replies, and for the explanation.

I've included some photos below, so let me know if you think more would be useful.

The way I've connected everything is as follows:

The regulator's SOLAR terminal is connected to the power input jack (this is where I plug in the solar panel, or the laptop power supply).

The regulator's BATTERY terminal is connected to the on/off power toggle switch, which in turn, connects to the 12V SLA battery. There is also a momentary switch wired in parallel to light up the voltmeter.

The regulator's LOAD terminal is connected to a fuse, which in turn, connects to the amplifier. There is also a cigarette lighter socket wired in parallel (this is where I plug in the iPhone or MP3 player for charging).

The load is a TA2020 amplifier, that runs on 12V and draws up to 2 or 3 amps. I only listened to it at low volumes, and still had the problem occur (i.e. the regulator cut off power to the LOAD terminal when I plugged in the laptop power supply).

Just to recap, the problem I encountered was that plugging in the laptop power supply (while everything was connected, and music playing) causes the regulator to cut off power to the LOAD terminal. As soon as I unplug the laptop adapter, power to the LOAD terminal is restored, and the amp immediately kicks in again and starts playing music. I would have expected the regulator to cope with this scenario (it's rated at 10A).

I also tried switching the amp off, and then on again (while the laptop adapter was still connected), but that didn't change anything.

BTW, I tried with two different power supplies, as you can see in the photos. One is a 16V laptop power supply, and the other is the type that allows you to select different voltages. I had it set to 19V. The same scenario occurred with both of these power supplies. The photos show the specs of each of them.

Daz, you said "the amp and computer supply should be connected to the battery terminals, not to the Load output of the controller". I wonder if this is the cause, since I have connected the amp to the LOAD terminal of the regulator. I thought the LOAD terminal would be the correct place to connect the amp???

Let me know if you need any more information, or if you have any suggestions on what I could try.

Thanks!
Pete

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[daz]

Any ideas?

Can you upload a drawing/photo of how you have connected everything together?
Also, let us know what the specifications (wattage, operating voltage, etc) are of the load, and of any other items that you are using (eg power supply, etc).