Off Grid & Having Problems...

[offgridder]

Hi,

I have been away from the forum for quite some time. We are totally off grid in New Mexico. I have been having some troubles with our system for a little while now & the last 2 nights the trouble got much worse.

Disregard my signature - need to update the info!

Our set up consists of:
8 - 90 watt monocrystaline panels
Xantrex 60 amp controller
8 - AGM 100ah batteries
Xantrex 1000 watt sine wave inverter
1000 watt cheapie inverter
8awg to the panels

When I upgraded the system last winter to what it currently is I was overwhelmed at the increase of power we had. We had much more than we could use. Just before the monsoon season arrived I noticed a decrease in power & once the rains came we were in trouble. I was only seeing at most 10 amps when the sun did come out, not good. Once the monsoon passed I expected to have a jump in power but it didn't happen.

I had a friend stop by who said it is the charge controller that is the problem but I am not sure. Another friend was just here & while he was here we did some troubleshooting. We decided to hard wire the panels to the batteries directly to see what the results would be under supervision. The 8 batteries never went above 12.9v & the amperage never rose above 9 amps (panels are rated at 5.13 amp). We then started to test the batteries & one looks to be shot for sure, reads 12.0 after a charge. There are 3 others that are reading 12.5 after charging & the other 4 were 12.75. Next we hooked up the 4 good batteries to the panels & got 15volts after some time.

Last night we had the 4 batteries hooked up to the system & they were charged. The charge controller was still disconnected. At dusk the battery voltage dropped like a rock. Was that because the controller was not connected? Can the panels draw power when the are not producing? I hooked up the controller & let the batteries get a fresh charge today.

We saw a good charge today & I was working online when maybe 3 hours after dark again, a quick a serious drop in power sent the inverters into a frenzy along with myself! So now this is where I am at (with generator running)

I have a controller that is only showing 10 amps & 130 watts of power at most at high noon. I am having quick discharges for no reason. My batteries are all less than 2 years old which really bothers me....

Please any suggestions as to what the heck is going on or what I can do to figure out a solution??

Thanks, Jonathan

[Cariboocoot]

Let's see.
800 Amp hours @ 12 Volts?
720 Watts of array?

There's your problem: don't expect that array to successfully charge those batteries.
The rough calculation: 720 Watts @ 77% efficiency = 554 / 12 Volts = 46 Amps which is 5.75 % charge rate at best. Subtract any concurrent loads and you have chronic deficit charging. Remember the hotter the panels get the less power they will produce, making the situation worse. The batteries' actual capacity will steadily decline.

For that much battery you should have something like this:
80 Amps peak current (10%) * 14.2 Volts charging = 1136 Watts * 77% efficiency = 1475 Watt array. Or about double what you've got. The Xantrex isn't going to handle that much current either. Without it the batteries will drain through the panels at night.

In all likelihood you now have ruined batteries that aren't going to perform no matter what you do to them. Time to start over.

[BB.]

What kind of Charge Controller? MPPT or PWM?

How are the panels wired? All parallel, series/parallel, (Vmp-array/Imp-array)?

I would suggest that you look at a reasonably priced (aka cheap) DC Current Clamp Meter from Sears. They are much easier to use to measure/trace down current flow/issues. And much safer too.

When you have lots of paralleled connections, the DC Current Clamp meter can quickly identify which paths are carrying current and which are not (connection problems, panel/battery problems, etc.).

-Bill

[niel]

sorry to hear you are having trouble. just to be sure you need to clarify some things for us.
1 which 60a xantrex cc do you have and if it is an mppt style then how are the pvs wired, series/parallel or both?
2 what gauge wire and their lengths are you using from the pvs to the cc and from the cc to the batteries?
3 are you using a bts to detect the battery temp?
4 what charge settings did you use?

i think 720w of pv is a bit too light for 8 agm batteries, but that has now dwindled.

if you wire direct from pv to battery with no cc or blocking diode then the power is free to discharge into the pv from the battery when it's dark or shaded. i do not advise you continue to charge the remaining batteries without the cc as agms are prone to overcharge. this will cause it to outgas and you can't replace the water lost in the outgassing so you lose capacity this way. in the future i would suggest a good battery monitor so you won't discharge your batteries too far again which i believe happened and you lacked enough sun to bring them up to full with the undersized array during a dismal period of time. i suggest a backup plan such as a generator and a good 3 stage charger for those times the weather does not cooperate.

[offgridder]

Let's see.
800 Amp hours @ 12 Volts?
720 Watts of array?

There's your problem: don't expect that array to successfully charge those batteries.

In all likelihood you now have ruined batteries that aren't going to perform no matter what you do to them. Time to start over.

Hmmm... NOT what I wanted to hear, but I guess I was and am still a newbie...

I guess my best bet right now is to stick with the 4 batteries that are still strong & use just those with the array?

Thanks, Jonathan

[BB.]

That will help... But knowing which type/model of solar charge controller you have and how are your panels wired will help us too.

-Bill

[offgridder]

What kind of Charge Controller? MPPT or PWM?

How are the panels wired? All parallel, series/parallel, (Vmp-array/Imp-array)?

I would suggest that you look at a reasonably priced (aka cheap) DC Current Clamp Meter from Sears. They are much easier to use to measure/trace down current flow/issues. And much safer too.

When you have lots of paralleled connections, the DC Current Clamp meter can quickly identify which paths are carrying current and which are not (connection problems, panel/battery problems, etc.).

-Bill

Hey Bill,
A PWM contoller, 60 amp Xantrex.
Panels are wired parallel
Do you have one certain DC Clamp Meter you can recommend (with a link to it maybe)? I looked on Sears and so soooo many....

Thanks, Jonathan

[Cariboocoot]

Hmmm... NOT what I wanted to hear, but I guess I was and am still a newbie...

I guess my best bet right now is to stick with the 4 batteries that are still strong & use just those with the array?

Thanks, Jonathan

Yes. Unfortunately with AGM's you can't take SG readings. And please note what Bill & Niel have said. Keeping the current flow even amongst eight batteries in parallel is very difficult. Wire sizing, length, and connections are critical.

When I suggested it was time to start over I meant go back to your loads. What are your daily Watt hour requirements and can they be reduced? Maybe you don't need 800 Amp hours of battery (up to 4.8 kW hours) to begin with. That would be a help. If you do need that much you might want to consider a higher system Voltage: it makes it easier.

[offgridder]

sorry to hear you are having trouble. just to be sure you need to clarify some things for us.
1 which 60a xantrex cc do you have and if it is an mppt style then how are the pvs wired, series/parallel or both?
2 what gauge wire and their lengths are you using from the pvs to the cc and from the cc to the batteries?
3 are you using a bts to detect the battery temp?
4 what charge settings did you use?

i think 720w of pv is a bit too light for 8 agm batteries, but that has now dwindled.

if you wire direct from pv to battery with no cc or blocking diode then the power is free to discharge into the pv from the battery when it's dark or shaded. i do not advise you continue to charge the remaining batteries without the cc as agms are prone to overcharge. this will cause it to outgas and you can't replace the water lost in the outgassing so you lose capacity this way. in the future i would suggest a good battery monitor so you won't discharge your batteries too far again which i believe happened and you lacked enough sun to bring them up to full with the undersized array during a dismal period of time. i suggest a backup plan such as a generator and a good 3 stage charger for those times the weather does not cooperate.

The PV is parallel
It is a pwm CC, wired via 8AWG - about 80 foot distance
No bts - is it possible to feel the heat when a battery warms up?
Not sure what you are asking on the settings I set...

Thanks for the info on the discharge. I hooked the CC back up right after drain occured & is still connected.

As far as a generator I have one & was building on the cabin so the batteries were being charged every time I ran a power tool which was often, & during the monsoon season... helped but never enough. I got desperate & borrowed a second charger which gave me 10 amp service each or 20 amps total. What type or brand 3 stage charger can anyone recommend? I know I need something with a little more power for sure....

Thanks for all the replies so far! I guess I have a lot to learn & I have made an expensive mistake not to mention I am on a tight budget...

[BB.]

Sorry, the link got messed up in the previous post (I will fix it next). Here is the correct link:

http://www.sears.com/shc/s/p_10153_12605_03482369000P

It is ~$60.00 and about the least expensive version I have seen that is functional.

You can easily pay $350-$450+ for a very nice Fluke meter--but this will do what you need for debugging your system.

-Bill