Design Stage for Off Grid Generator and Battery Shed

[Iboondock]

I'd appreciate more details on your solar and generator installations, if you don't mind.

I have 19.2kw in battery (48 v), 2200 watts of solar, Schneider MPPT 60/150 CC, Magnum inverter, 7 kw Generac generator. I have the Magnum magweb for monitoring and the AGS manages the generator. With the controller that came on that model of generator it was a 5 minute, $5 modification to make it a 2-wire start that draws zero power when it's off. I understand it is much harder or impossible to do this with the new series controllers. If I was doing this today I would double the solar, and leave everything else the same.

[ChugiakTinkerer]

Thanks homer and lboondock, appreciate the details.

[MacGyver]

I have 19.2kw in battery (48 v), 2200 watts of solar,
If I was doing this today I would double the solar, and leave everything else the same.

Hi iboondock: May I ask how long you had the batteries and what batteries are your using?
You need more panels is it because of your location, weather or snow on the panels?

[4merguide]

We're 100% solar from mid January thru mid October. November and December are generator months..

I was going to ask where you were located because I didn't think that possible in AK., but I clicked on your "about" page and see that you are in Anchorage. Very impressive! Should I assume you heat with wood?

[Iboondock]

Hi iboondock: May I ask how long you had the batteries and what batteries are your using?
You need more panels is it because of your location, weather or snow on the panels?

I have Rolls S-530 batteries and I've had them for just about 8 years. More panels would help in the shoulder seasons, especially the fall when we can get the long stretches of rain. And it would mainly be to reduce generator time. December will always be generator month, but I think I could get it down to 45 days.

I'm not going add them now, but if I was building today I could get almost twice the array for the same cost I paid for what I have. I am able to put my panels vertical in the winter so snow isn't an issue.

I was going to ask where you were located because I didn't think that possible in AK., but I clicked on your "about" page and see that you are in Anchorage. Very impressive! Should I assume you heat with wood?

Yes we heat with wood. Maybe I should clarify, this isn't our full time residence, this is a cabin in the Matsu.

[homer]

Couple of things to consider. 48 volts system. If they improve electric car batteries, and bring the cost down, they could be your next set. Are you sure you need your generator in autostart? I don't think your batteries will freeze, with the solar.

[MacGyver]

With out heat .....It’s a hole new ball game when it comes to batteries.



At the time I suggested using lithium battery the OP was going to be keeping the battery warm. No heat ....no LiFePO4 storage batteries.

[lyuluck]

1.The real wattage of an off-grid solar system is the total wattage of solar panels X hours of sunshine X 0.6(wire lost) X Sin Light angle, due to the effect of snow or dust it will even lower. Thus you should calculate the real power in conservative calculations.
2.As the battery is charged and discharged each time, its actual electricity capacitance will decrease. It is important to check the battery condition regularly.
3.If the battery is over-discharged, the battery may freeze at extremely cold temperatures. In this situation, neither solar system nor diesel generators can generate electricity when connected to frozen batteries, but in your plan, there is a room with a constant temperature, that can prevent the liquid from freezing.
4.Bluesolar MPPT is a good controller for the solar system, and you can download an APP which can show the voltage, wattage, and more details,that MTTP will prevent the battery from freezing and inform you when and where the problem happens.
5.It is best to use monocrystalline solar panels in high latitude areas.

[hunter1951]

MacGyver, The system they specced for me is based on my guesstimate of what future energy use will be. The system is 24V, with an inverter capable of 4000 watts. I'll have to look up what the range of daily energy use was, but as I recall it was 4 to 5 kWhr per day. That's pretty substantial, but I envision having remote internet with a continuous weather station and remote monitoring, plus many of the comforts of home. I hadn't considered lithium batteries, I'll have to do some reading up on those. Thanks for the inout, and let me know if I've missed something obvious. CT

from my understanding lithium batteries do not work well in the cold -5 and they stop functioning

[ChugiakTinkerer]

from my understanding lithium batteries do not work well in the cold -5 and they stop functioning

Yep, that's my understanding as well.

I think I'll stick with the proposed AGM batteries. They have the best performance at low temperatures and are more freeze-resistant. But I'll still be putting the batteries and electronics in an insulated enclosure. With the internal power draw of the equipment and the heat generated when charging the batteries it will be equivalent to having a 60W light bulb on. So it shouldn't be an issue to keep the batteries above freezing. I can add another heat source too, such as the aforementioned light bulb or perhaps a battery blanket, heat mat, etc.

I am more concerned about the enclosure overheating in the warmer months. So that will be something to plan for. Maybe something as trivial as vents that get plugged with insulation in the fall and removed in the spring. Or a thermostatically controlled vent fan. My goal is to keep the batteries in the recommended range of 32 to 104 F.

[Iboondock]

Couple of things to consider. 48 volts system. If they improve electric car batteries, and bring the cost down, they could be your next set. Are you sure you need your generator in autostart? I don't think your batteries will freeze, with the solar.

In my case, I have a steady 50 watt draw for remote monitoring/control/security. It's not unusual in December that 2200 watts of solar won't cover that load during daylight, much less provide any charging. Without that load, solar would probably cover the draw of just the charge controller.

[MacGyver]

Couple of things to consider. 48 volts system. If they improve electric car batteries, and bring the cost down, they could be your next set. Are you sure you need your generator in autostart? I don't think your batteries will freeze, with the solar.

You don’t need to freeze a battery to kill them.

People killed batteries the weapon of choice is chronic deficit charging, or not doing battery maintenance. ALL batteries including AGM needs to be recharge to 100% SOC within a day or two before they start to loose Ah’s. The first signs of a problem is filling the generator fuel tank daily not weekly follow by replacing the battery bank $$$$.