Loss of power...somewhere?

[solar pete]

Hello all!
I'm a new member. And a new (ish) owner of an off grid system. I will be quick with the intros..
Live in Virginia. Nearest transformer is about 1.5 miles from my house. REC wanted about 40K to run power to my house, so I looked into an off-grid solution.
I altered appliances to suit, closed cell foam in the walls, high efficiency everything... FYI: My one mistake was an electric oven. Nothing I can do about it now.

My system is 39 Axitec Solar Modules, Dual Hybrid Inverter system (Schneider Electric Conext XW+), a Generac 15kW Standby Generator and 24 Crown CR430 Deep Cycle Batteries. (3 stacks of 8 batteries). It was designed and installed by a professional company.

Back in August is when the system/house was finished. Back then I thought I was just prepaying for electricity and that was all I needed to worry about. Ha!

Since then we have struggled with having "enough" power, but I wasn't educated enough to know if this was our fault (i.e. trying to live fat on the hog) or the systems fault. This is already getting long, I apologize.

Since then I installed a Conext Combox and an SOC Battery Monitor.

Roughly a month ago (as my knowledge increased to the point of being able to question things, my battery "day" was maybe 10 or so hours. The company told me to get a Battery Life Saver. I had a long conversation with BLS guy and went about testing all my batteries before installing the device. With a fairly barbaric Hydrometer, I determined I had 3 bad batteries (at this point they are like 7 months old) due to an open cell (i.e. the specific gravity delta between the cells of an individual battery was greater than 0.05). I moved those three batteries to the far stack and disconnected that stack of batteries from the system. 3 days later the company who installed the system disagreed with my conclusion about the batteries and said to put them back into the system and "let the BLS do its job." For those two days, I still was running at least 10 hours without solar power before the generator would come on. He gave me a different kind of open cell test to conduct and those three batteries all passed.

I put them back on and went back to living on 3 stacks. Coincidentally, there were 4 or 5 days straight of good sun and I really had no sense if the system was any better or worse. Then the lil blizzard hit the DC metro area. On day one, I realized my generator was buying me about 4-5 hours of power before it would restart. On the second day, I went out in the storm and disconnected that far stack (back to two stacks). I was awarded with recovering to the 8-10 hours between generator runs state I was in before I put that third stack back on.

When the weather cleared, I went back out and tested each and every battery again.

Now, all my specific gravities are higher (previously ~1.23; now 1.24 or higher) and in the "bad" batteries I don't see the delta of 0.05 between cells. I put the third stack back on the system. Right now, I'm getting about 12-13 hours of power.

So... here's the question. Where's my dang power??? I know I run about 20 kWh per day. This system should be providing me roughly 30kWh before I would be at 40% battery power and need a charge. So that's a day and a half...NOT a half a day. I know there are temperature losses and what not, but theres no way it should be that much.

The latest thing the company told me is they are going to come by and replace all the serial cable in my battery bank. I guess this could be a part of the issue (and could account for some of the fluctuations in performance between otherwise identical configurations), but when the generator is charging the batteries would the "losses" show up there as well? I mean, wouldn't the generator be running, the inverter think it's charging the batteries, but this mythical bad wire would be preventing the battery from receiving the charge? This doesn't seem to be the case because when did my battery testing all the loaded volt test were good (i.e. over 60 volts).

Sorry for the length of this post.... I'm just looking for some thoughts/advice. I trust this company (maybe this post doesn't summarize that well) but I also know this the largest system they've ever done and there are times I think they are learning just as much from me as I am from them.

Oh...and I was a Mech E, so the knowledge is hidden in there... it's just been 20 years since I've worked those brain cells.

Thanks.

Howdy, what size in watts are those panels, I want to know the size of your system e.g 39 x 250watt panels would be a 9.75kW system, I suspect you need more panels, is your genny on a auto start switch or do you have to manually turn it on?

[inetdog]

Don't assume your specific gravity meter is accurate. I have seen three of the SP101 meters read low. I think they had a bad run. The one I have now is spot on.

A good point. For those who will be relying on a hydrometer to check the health of their thousand dollar battery bank it is a relatively small expense to buy or make up a jar of reference electrolyte with a known SG. That way you can calibrate your hydrometer when you first get it and check it periodically for damage.
Checking for 1.00 SG in plain distilled water is not a good enough test, but is better than nothing if your hydrometer goes that low.

It is also worth repeating that you either need a hydrometer with built-in temperature compensation or an easy to use correction factor chart into which you plug the electrolyte temperature (not the room temp or the outside case of the battery if you are charging heavily at the time.

[hammick]

For those who will be relying on a hydrometer to check the health of their thousand dollar battery bank

I wish my battery bank was only a thousand dollars. I suspect the OP has 7k in his batteries alone.

[SunEagle]

I just thought of another area the OP has an issue. There are 3 strings of 8 x 6v batteries that makes that 48 volt 1290Ah system.

There is a chance the parallel wiring issue has bit him causing one string of batteries to not charge/discharge evenly with the other 2 strings.

Depending on his daily needs I would suggest a battery bank made up of 24 x 2V XXXX Ah batteries. That would eliminate any parallel wiring issues.

[Logan005]

"Back in August" Those batteries are only 6 months old.

[SunEagle]

"Back in August" Those batteries are only 6 months old.

Yeah, but they could have been abused and certainly the snow cover did not help.

[Mike90250]

You didn't mention what your charge controllers are ?
But you sure have need of an energy diet.

Short term fix - get a honda eu1000 and hook it up to the 2nd inverter via a 120-240VAC step up transformer and just run that sucker all night, should keep you going till you get it all sorted out
(I don't know if you can hook a 2nd genset to the slave inverter, you could also hook it up to AC1 of the prime inverter

[LETitROLL]

Yes. Vertical refrigerator and oven. However, the part we use regularly is the cooktop, which is gas... this unit cost over 6 grand. And quite frankly, we don't use it all the time. I'm not in the category of people who live in fear of running the generator, and if I have to fire up the generator on the occasion that my wife uses the oven, so be it. I also have a Kamado Joe which does most of our "cooking". And my back up generator lives on propane, I have a thousand gallon tank buried in the yard. Furnace is LP, dryer is LP. I'm looking for an LP hair straightener. Know where I can get one, the wife is waiting patiently.

But you aren't saying these appliances (coffee maker too) are my problem?? I know what my usage is, even with those appliance factored in, and its still way to damn low for the system I have.

Peukerts law is possibly coming into play a bit with all those large electric appliances, keep in mind that if your usage is not spaced out the same each day and sometimes multiple large loads are on at the same time, even though your system is large enough to handle it, your batteries will fall faster and not provide as many total AH as they would at a lower discharge rate.