Suspect panel: At what voltage should a 12V panel be charging a battery?

[Simon99]

What would one expect the voltage to be for a 12V panel in full sun connected directly to a 12V battery?

I am having a boatload of problems with my solar project. Here is what it looks like: P1110342.jpgP1110347.jpgP1110353.jpgP1110358.jpg

It is a 5W BP panel connected to a Morningstar Sunsaver-6L charge controller connected to a 5Ah sealed lead acid battery, supplying power to a 12V car cigarette lighter to USB adapter, to an Android phone. I wrote Android software to be able to send back remote photos to any other phone.

I have already had one system out in the field for months. It works like a charm. Although I will admit that on that one I used a 10W panel with a 7Ah battery.

I have had problems with this one since the moment I put it together. The first morning I came outside, I had all sorts of critical errors on the charge controller, the battery was close to flat and the panel wasn't charging the battery. Since then I have focused on the panel because I can't get more than 12.4 volts out of it. This happens to be less than the low voltage reconnect on the charge controller, so it is never going to start charging the battery in the morning.

The panel is a BP Amaresco AMS-SX405M (http://www.mrsolar.com/pdf/Ameresco/Ameresco%20405M.pdf). I took readings this morning. The open voltage is 22V. The short circuit current is 280mA. I bought a brand new car battery yesterday. The voltage on the car battery is 12.6V. When I connect the panel directly to the battery, it is still 12.6V. The current running to the battery is 300mA.

Before I go and get another panel, I'd like some advice on whether the voltage is too low. I would have thought 14V better. I do recall the 10W panel being around 13.3V when charging. I bought a small electroncs charger yesterday to see if there was a problem with my 5Ah battery, but it charged up in a couple of hours, starting at 1.4A and trickling down to 100mA.

[inetdog]

What would one expect the voltage to be for a 12V panel in full sun connected directly to a 12V battery?

I am having a boatload of problems with my solar project. Here is what it looks like: [ATTACH=CONFIG]2318[/ATTACH][ATTACH=CONFIG]2319[/ATTACH][ATTACH=CONFIG]2320[/ATTACH][ATTACH=CONFIG]2321[/ATTACH]

It is a 5W BP panel connected to a Morningstar Sunsaver-6L charge controller connected to a 5Ah sealed lead acid battery, supplying power to a 12V car cigarette lighter to USB adapter, to an Android phone. I wrote Android software to be able to send back remote photos to any other phone.

I have already had one system out in the field for months. It works like a charm. Although I will admit that on that one I used a 10W panel with a 7Ah battery.

I have had problems with this one since the moment I put it together. The first morning I came outside, I had all sorts of critical errors on the charge controller, the battery was close to flat and the panel wasn't charging the battery. Since then I have focused on the panel because I can't get more than 12.4 volts out of it. This happens to be less than the low voltage reconnect on the charge controller, so it is never going to start charging the battery in the morning.

The panel is a BP Amaresco AMS-SX405M (http://www.mrsolar.com/pdf/Ameresco/Ameresco%20405M.pdf). I took readings this morning. The open voltage is 22V. The short circuit current is 280mA. I bought a brand new car battery yesterday. The voltage on the car battery is 12.6V. When I connect the panel directly to the battery, it is still 12.6V. The current running to the battery is 300mA.

Before I go and get another panel, I'd like some advice on whether the voltage is too low. I would have thought 14V better. I do recall the 10W panel being around 13.3V when charging. I bought a small electroncs charger yesterday to see if there was a problem with my 5Ah battery, but it charged up in a couple of hours, starting at 1.4A and trickling down to 100mA.

A panel that small (5 watts) is typically thought of as suitable for solar garden lights or as a battery maintainer rather than a battery charger.
The fact that you measure 22 volts open circuit (Voc) is a good indication that the panel has enough voltage to charge a 12 volt battery. But the output voltage of the panel (and the output voltage of the CC) will be limited by the battery voltage. 280 ma is not enough current to significantly raise the battery voltage above the resting voltage of that battery. For a 5 AH sealed battery you need to be able to get at least 500 ma from the panel at 14 volts. Since the maximum power voltage of the panel is probably around 20 volts, you would need at least a 10 watt panel to give you that.

It is also possible that the CC you are using just cannot work properly with that low a current.

Since you are seeing the battery at or below the low voltage cut off (LVCO) in the morning, it looks like the phone charger circuitry is taking more power out of the battery than the panel can put back in during the course of one sunny day. Again, your panel is too small for this use.

By the way, the low voltage reconnect on the CC only affects output to the load terminals of the CC, not the charging process. Are you sure you have wired the CC correctly? Have you measured the charging current between the CC and the battery? (DO NOT try to do this by shorting the meter across the battery similar to the way you measure Isc of the panel!!! You need to put the meter in series in either the + or - lead of the battery.)

[Sunking]

What would one expect the voltage to be for a 12V panel in full sun connected directly to a 12V battery?

Battery voltage. Here is a big problem for use connecting the panel directly to the battery. You 5 watt panel produces .27 amps @ 18 volts. Connect it directly to a 12 volt battery and you have 12 volts @ .27 amps = 3.2 watts.

[Simon99]

Interesting.

280 ma is not enough current to significantly raise the battery voltage above the resting voltage of that battery.

That I did not know.

For a 5 AH sealed battery you need to be able to get at least 500 ma from the panel at 14 volts. Since the maximum power voltage of the panel is probably around 20 volts, you would need at least a 10 watt panel to give you that.

Maybe that explains why the 10W panel I used in the previous version I built worked fine.

It is also possible that the CC you are using just cannot work properly with that low a current.

Could be. But if I unplug and reconnect the CC it charges just fine. I see 12V across the load terminals and measure 280mA going into the load (Coincidentally, this is also about the full sun current from the panel, which would result in no net charge to the battery while in the sun. So yes, maybe the panel is not big enough - although I should mention that the load is only drawn part of the time. When the phone is charged, there is no load). More likely the unit it cutting out when the battery voltage gets too low - it gets down to 11.7V and that is the LVD of the unit. But it never gets up beyond 12.4V in full sun and the LVR of the unit is 12.6. So that is consistent with a working CC but not enough power from the panel.

Since you are seeing the battery at or below the low voltage cut off (LVCO) in the morning, it looks like the phone charger circuitry is taking more power out of the battery than the panel can put back in during the course of one sunny day. Again, your panel is too small for this use.

Agreed. I have already decided to order a 10W panel.

Mind you, I do think the CC might have been fried for some reason the first night I had it. The flashing LEDs correspond in the manual to a damaged internal temperature sensor. No idea why.

Are you sure you have wired the CC correctly?

Yep. Done this before. Checked it. Not much to check.

Have you measured the charging current between the CC and the battery?

Yep. 280mA. And yes - in series.

Thanks for the good advice. Maybe just not enough oomph in the 5W panel.

[Simon99]

Battery voltage. Here is a big problem for use connecting the panel directly to the battery. You 5 watt panel produces .27 amps @ 18 volts. Connect it directly to a 12 volt battery and you have 12 volts @ .27 amps = 3.2 watts.

From where did you get the 18V?

I should clarify that my setup involves a charge controller between the panel and the battery. I was just connecting it directly to see if the panel would raise the voltage above the resting voltage of the car battery (12.6V). It didn't.

For the small 5Ah battery in my project, it got depleted overnight and its resting voltage was around 11.7V. The charge controller was showing a bunch of errors, including flat battery and low voltage disconnect to the load. I disconnected everything, reconnected and in full sun via the charge controller, the voltage from the panel to the charge controller and charge controller to the battery was 12.4V. Still not high, but showing that it was charging. I measured the current at 280mA.

As in my earlier post, I think a bigger panel is going to fix the problem. I was just trying to get a more scientific answer to what I was seeing.

[green]

The location you have it in appears very shaded from the photos. More Sun would help your problem.

Green

[PNjunction]

That is the latest Gen-3 sunsaver. There have been reports that it would be wise to contact Morningstar in regards to possible early gen-3 issues. Some had the led light-show, and others seemed to have needed replacements.

http://www.solarpaneltalk.com/showthread.php?7780-Morning-star-ss20l-12-charge-controller

With my earlier gen-2 Sunsaver models, I run at 14.4 volts on my agm's, which means I remove the jumper and actually run with "flooded" on purpose. I go by the actual voltage ratings, and not the canned silk-screen labels. Sealed is jumpered for 14.1, which is too low for my agm application. The gen-2's don't have the auto equalization routine.

HOWEVER, with a Gen-3, if you purposely set it for 14.4v by manipulating the jumper, every 28 days it will do an equalization which nearly everyone agrees is bad for an agm! Yet, here what Morningstar calls an eq seems pretty mild - only 14.9v for 3 hours once every 28 days. My agm's have no problem with that.

[Simon99]

The location you have it in appears very shaded from the photos. More Sun would help your problem.

I had it in that location originally to simulate less than ideal conditions. Later I moved it into a full sun areas but I still had problems.

That is the latest Gen-3 sunsaver. There have been reports that it would be wise to contact Morningstar in regards to possible early gen-3 issues. Some had the led light-show, and others seemed to have needed replacements.

I suspected that. After only 3 days, I came out one morning to find red-yellow-green alternating LEDs, which according to the manual means the temperature sensor is fried and I need to have the unit "serviced" (Read "replaced"). I can't afford to have an unreliable unit. This thing is going to be in a remote location.

You may wish to run in the flooded setting if 14.4 volts is a better cv voltage setting for that agm.

I am going to have to do my reading on that.

[PNjunction]

By all means go by what the best voltage for your system is. Some products lump both agm and gel into the same chemical category, perhaps figuring that the consumer might not know what the chemistry of their battery is, and take the safest way out with the lowest voltage in the "sealed" setting.

Just be sure that if you do this with a gen-3 by purposely running 14.4v flooded with the agm, that you are ok with the mild 14.9v eq every 28 days. Normally eq to me means running at 15.5v or greater with a forced overcharge. At 14.9 it seems mild, but you'll have to make that choice.

Also, is that box totally sealed? That's not a good idea, even with the small battery. If for some reason that thing outgasses, you've got to have some ventilation.

[Simon99]

Also, is that box totally sealed? That's not a good idea, even with the small battery. If for some reason that thing outgasses, you've got to have some ventilation.

No, it is open. You can see in the photos above. The inner box is pretty much sealed and contains the phone and the USB charger. This is to keep it out of the winter elements. The outer casing contains the charge controller and battery, both of which might get hot. The outer casing is designed to shield the inner box from direct sun, thus keeping it relatively cool in the summer. It also gives the charge controller shade and fair cover from rain, but is completely open at one end to allow the phone's camera to get a picture. You can see I have cut out a slot in the outer cover.

[Sunking]

From where did you get the 18V?

Because any 12 volt battery panel Vmp = 18 volts.

[Sunking]

I should clarify that my setup involves a charge controller between the panel and the battery. I was just connecting it directly to see if the panel would raise the voltage above the resting voltage of the car battery (12.6V). It didn't.

Not possible at least in any acceptable time frame. .25 amps into a car battery is pretty much meaningless.

[Simon99]

Because any 12 volt battery panel Vmp = 18 volts.

Really? The BP panel specifications say Vmp = 16.5 volts.

http://www.amerescosolar.com/sites/default/files/sx305m_a.pdf

[Sunking]

Really? The BP panel specifications say Vmp = 16.5 volts.

http://www.amerescosolar.com/sites/d...s/sx305m_a.pdf

OK that is a little low Vmp for a 12 volt battery panel, but point is its Imp is .27 amps and at 12 volts = 3.2 watts. Not enough panel wattage to charge your 5 AH AGM that has a minimum charge current requirement of 1.25 amps. You need a minimum 25 watt panel to charge that battery properly. 50 to 100 is ideal.

[Simon99]

Not possible at least in any acceptable time frame. .25 amps into a car battery is pretty much meaningless.

Agreed. I just used the car battery because I did not know if my 5Ah battery was fried. I charged it fully, let it discharge for 3 hours at 400mA until it got down to 11.85V, disconnected it, found that it had a standing charge of 12.5V and now I have it hooked up back again to my project just to see how things go.P1110366.JPGP1110369.JPG

The panel charges the battery at 300mA when perfectly aligned to the sun, but when I connect the load (Which has now discharged a little - a cell phone), it drops to 40mA. Obviously not much of a charge. Over the last hour it has come up to 70mA as the phone slowly gets more charged, but as someone suggested, I should just get a bigger panel so that in full sunshine, a flat phone will be charging at the max rate at the same time as the battery is charging at the max rate. So that's what I did. Just ordered a bigger panel an two hours ago.