Need Help w/small solar system

[MikeC]

I have a cabin in the mountains that I solarized a few years ago. The system consists of 2 pairs of panels totaling 310 watts/RV controller/6 trojan 6 volt batteries/1750 'go power' inverter which is wired into the cabin fuse box. My only other source of electricity is propane generator that I rarely use. The system only operates LED lights (I think they are all 4 watts & we are careful about only using lights as needed); satellite radio boom box; charging iPhones & iPods; charging Bose boom box and occasional iMac computer. Morning sun on the panels begins about 10am and ends about 3pm this time of year. My battery voltage is dropping by early afternoon to 11.8 and by bedtime is down to 11.4 or so. I don't know if I need more battery storage or more panels to charge the existing batteries faster and more completely. Any advise would be much appreciated.

Second question; how does one determine if a solar panel is working at peak capacity?

Thanks in advance,

mike

[SunEagle]

I have a cabin in the mountains that I solarized a few years ago. The system consists of 2 pairs of panels totaling 310 watts/RV controller/6 trojan 6 volt batteries/1750 'go power' inverter which is wired into the cabin fuse box. My only other source of electricity is propane generator that I rarely use. The system only operates LED lights (I think they are all 4 watts & we are careful about only using lights as needed); satellite radio boom box; charging iPhones & iPods; charging Bose boom box and occasional iMac computer. Morning sun on the panels begins about 10am and ends about 3pm this time of year. My battery voltage is dropping by early afternoon to 11.8 and by bedtime is down to 11.4 or so. I don't know if I need more battery storage or more panels to charge the existing batteries faster and more completely. Any advise would be much appreciated.

Second question; how does one determine if a solar panel is working at peak capacity?

Thanks in advance,

mike

I can think of a few things that could be the problem.

More than likely the 310 watts of panels was not enough to properly fully charge all of your batteries.

Also with the system being a couple of years old and the batteries being wired in a series / parallel configuration I would presume one or more of those batteries is not properly charging causing the entire system to lose capacity.

You also need to charge the batteries using a generator and charger every once in a while to make sure they haven't stratified.

Before you go out and purchase any more panels or batteries you will need to check each of the batteries and solar battery charger to see if everything is working properly.

To determine if a solar panel is working properly you need to check the amperage during a clear sunny day at solar peak (around noontime). The panel also needs to be at the right angle aimed directly at the sun. You should get a reading about 90% of the Imp rating on that panel.

[MikeC]

Need Help w/small solar system

Thanks SunEagle for the quick response.

The batteries are only 1 year old and tested OK. They are wired in a series. Sounds like a good idea to top them off w/generator and charger. Does it matter how the charger cables are connected to batteries so long as neg to neg and pos to pos?

Excuse my ignorance but how do I go about testing the panel's amperage?

Thanks,

Mike

I can think of a few things that could be the problem.

More than likely the 310 watts of panels was not enough to properly fully charge all of your batteries.

Also with the system being a couple of years old and the batteries being wired in a series / parallel configuration I would presume one or more of those batteries is not properly charging causing the entire system to lose capacity.

You also need to charge the batteries using a generator and charger every once in a while to make sure they haven't stratified.

Before you go out and purchase any more panels or batteries you will need to check each of the batteries and solar battery charger to see if everything is working properly.

To determine if a solar panel is working properly you need to check the amperage during a clear sunny day at solar peak (around noontime). The panel also needs to be at the right angle aimed directly at the sun. You should get a reading about 90% of the Imp rating on that panel.

[SunEagle]

Thanks SunEagle for the quick response.

The batteries are only 1 year old and tested OK. They are wired in a series. Sounds like a good idea to top them off w/generator and charger. Does it matter how the charger cables are connected to batteries so long as neg to neg and pos to pos?

Excuse my ignorance but how do I go about testing the panel's amperage?

Thanks,

Mike

Ok. I may have misunderstood how your batteries are wired.

You said you had 6 x 6V Trojans. You also indicated the battery voltage measured at the end of the day was 11.8 volts. So the only way to get 6 batteries wired for a 12 volt system is to have 3 parallel strings of 2 in series.

If they were all wired in series as you indicated you would have a 36 volt system. So exactly how are they wired?

When testing solar panels I use a clamp on DC ammeter. This shows me what is being sent to my charger. In the middle of the picture you will see a red device on the ground. That is my ammeter. The orange device on the left is my voltmeter. With these two instruments I can measure both the voltage and amperage of being generated by that folding 80 watt solar panel which is aimed directly at the sun.

Small Portable PV sys pic3.jpg

[Sunking]

Yes something is definitely wrong.

1. If you have 6 golf cart batteries (6 of them), there is no way to wire them in series to get 12 volts. They would have to be wired 2 x 3 to get 12 volts. 2 in series per string, and 3 parallel strings.

2. Assuming those are the standard golf cart batteries of 200 to 2225 AH with a 2 x 3 configuration would give you a 12 volt @ 600 to 675 AH which is quite a bit for a 12 volt system. However 310 watt panel and a PWM controller is not enough wattage to really maintain them, at least not for full daily usage. With only 6 hours of direct light translates to around 2 to 3 Sun Hours, and that will only give you roughly 400 to 500 watt hours of usable power per day. The batteries are capable of giving you as much as 3600 watt hours to 50% DOD or 1500 watt hours @ 20% DOD. So you are way short on panel wattage and Sun Hours. Depends on how much you actually use in a day which we do not know.

So yeah first thin gis get the batteries on a commercial AC charger and charge them for 24 hours to see if they can be saved or not. It is possible you already destroyed them.

[MikeC]

Need Help w/small solar system

Sorry for the confusion and my ignorance.....

It is a 12v system w/3 parallel strings of 2 in a series. Picture attached.

mike

ATTACH=CONFIG]4316[/ATTACH]

Ok. I may have misunderstood how your batteries are wired.

You said you had 6 x 6V Trojans. You also indicated the battery voltage measured at the end of the day was 11.8 volts. So the only way to get 6 batteries wired for a 12 volt system is to have 3 parallel strings of 2 in series.

If they were all wired in series as you indicated you would have a 36 volt system. So exactly how are they wired?

When testing solar panels I use a clamp on DC ammeter. This shows me what is being sent to my charger. In the middle of the picture you will see a red device on the ground. That is my ammeter. The orange device on the left is my voltmeter. With these two instruments I can measure both the voltage and amperage of being generated by that folding 80 watt solar panel which is aimed directly at the sun.

[ATTACH=CONFIG]4315[/ATTACH]

[Sunking]

OK those are Trojan T-105's. Wiring is suspect but I will assume it is at least correct, but seeing 12 AWG Romex is a bit frightening.

The big question is how much energy are you pulling each day from the batteries in terms of watt hours? We do not know, nor can we guess. What I do know is your panel wattage and hours of sun are not good. So that leads me to say you are in deficit charging, meaning you are using more than you can replace.

For a 12 volt 675 AH battery stack would require a minimum 1000 watt panel system on a 60 amp PWM controller with the panels exposed to the clear horizon east, south, and west. If you had 60 amp MPPT controller would require a 675 watts of panels. So I am pretty confident you are in deficit charging. You might as well get use to using the generator every day for a few hours. With your limited sun exposure there is really no way for you to get enough panel wattage to properly charge the batteries without damage. It will take a 2 Kw genny with a 60 amp 12 volt charger to keep those batteries up and running.

[inetdog]

The most efficient use of your generator (avoiding running it at less than 50% load) will be to use the generator in the AM for just long enough to get the batteries to the point where the PV can finish the charge during the rest of the day.
However, to start out on the recovery process you need to:
1. Have a temperature compensated hydrometer so that you can accurately measure the state of your batteries, and
2. Do whatever is necessary (read some threads here in the subject) to get your batteries back to 100% SOC and equalized if that proves necessary.
Do that as soon as possible to avoid irreversible damage to your expensive batteries.
Read carefully the charging instructions from Trojan and then keep in mind that they probably refer to a charging method that your PV system will not be able to follow.

[MikeC]

Need Help w/small solar system

I sure appreciate the feedback from all who have contributed to this thread. You have all been extraordinarily helpful and I have learned a lot.

Thus far I have learned that my panels aren't getting sufficient exposure (nor do I have sufficient panel wattage) to top off my six 6 volt batteries daily so I'm losing ground and should charge them up with my generator. I need to retest my batteries and check the amperage of the panels.

Another question #1: Yes, I am using 12 AWG romex from my controller to the batteries. Is the size insufficient? Dangerous?

Another question #2: My controller is an RV style. It is either a Mark 20 or 22 by Specialty Concepts. Is it adequate for my 4 panels (310 watts) or the batteries?

Just FYI....my cabin is surrounded by pine trees which limits my exposure. There may be some confusion with regard to the wiring. All the smaller black wiring shown in the picture is for wall mounted RV type lighting that is seldom used. Otherwise, most of our use is the converted AC current.

Thanks again!

mike

OK those are Trojan T-105's. Wiring is suspect but I will assume it is at least correct, but seeing 12 AWG Romex is a bit frightening.

The big question is how much energy are you pulling each day from the batteries in terms of watt hours? We do not know, nor can we guess. What I do know is your panel wattage and hours of sun are not good. So that leads me to say you are in deficit charging, meaning you are using more than you can replace.

For a 12 volt 675 AH battery stack would require a minimum 1000 watt panel system on a 60 amp PWM controller with the panels exposed to the clear horizon east, south, and west. If you had 60 amp MPPT controller would require a 675 watts of panels. So I am pretty confident you are in deficit charging. You might as well get use to using the generator every day for a few hours. With your limited sun exposure there is really no way for you to get enough panel wattage to properly charge the batteries without damage. It will take a 2 Kw genny with a 60 amp 12 volt charger to keep those batteries up and running.

[SunEagle]

Sorry for the confusion and my ignorance.....

It is a 12v system w/3 parallel strings of 2 in a series. Picture attached.

mike

ATTACH=CONFIG]4316[/ATTACH]

Alright. So my first guess that you have a paralleled battery system is correct. Due to that and what looks like different wire sizes connecting them (black wire is larger than the red) they will not charge or discharge equally due to different resistances and therefore create a weak link (one battery) which will hurt the rest.

Next as Sunking has mentioned you do not have enough solar panel wattage to charge that bank up to full so you have been slowly depleting them.

You could try to get them back up to full charge using a generator and charger but I fear that even though they are one year old they will not last much longer.

[Freezer66]

Good Info, Thanks.