Best Generator Use

ForeverHomestead · January 2021

I am wondering the best way to use the generator while off grid. By this I mean as far as keeping batteries charged.

In the winter I usually wake up, start the generator to handle the morning coffee making and breakfast and to charge up the batteries for a couple hours. Then in the evening I start again to deal with power used by cooking and such and run for 3 or so hours.

Usually once a week I run the generator for 5 or 6 hours to give the batteries a good charge.

I have recently realized my batteries needed some work... (That is a whole other Post) and wondered if there is a better way for me to use the generator. Am I better to try to run the generator just once a day as far as charging goes and run for 4-5 hours instead of 2 times only 2 or 3 hours at a time, then still do a weekly longer charge to fully charge.

In the summer this is never an issue because there is plenty of sun.

wellbuilt · January 2021

My panels are covered by snow most of the winter.

I do sweep the panels with a 35’ pole and squeegee that can get me some sun power most days .

But what seams to work best for me so far is running the generator every morning for a hour or so every day and 4 hours every 3 or 4 days or when I am heading home with the power turned off when I’m not there .

Trukinbear · January 2021

I relinquish complete control of my generator to my SMA SI6048 Inverter/Charger - my previous system that left control of the generator to people had batteries that didn't last long.

mike95490 · January 2021

Everybody's set is different. If running the generator a couple hours in the AM handles the big loads and charges batteries, I think that's a good thing. Just be sure to get the batteries full a couple times a week - watch the cloud forecast, let the sun do it's work

mcgivor · January 2021

Then again it's battery chemistry specific, lead acid need to be kept out of partial states of charge, whereas lithium tolerate it without detrimental effects, making late generator charging a better option, charging just enough to get through the night.

Charging multiple times a day with LA may actually be detrimental as each counts as a cycle, theroitically speaking, but weather is hard to predict. Invariably when I chose to charge in the morning due to overcast conditions, with LA, the sky cleared, and vice versa, thankfully, since my change to LFP was made, my generator has become superfluous for the most part, except for welding

ForeverHomestead · January 2021

Hmm thanks for the input guys.

Yes I have flooded cell batteries. I have 48 Rolls 2 Volt batteries.

wellbuilt · January 2021

48 2 volt cells is a lot of power , I would only charge once a day .

Or even every other day , down to 20% or so .

I think I would try not so get below 20% in one day .

Maybe turn some things off if you are not getting any sun .

BB. · January 2021

There is one way people have been charging deep cycle lead acid batteries... Assuming you are using power every day (not sitting "unused"), you can cycle between 50% to 80% state of charge... Start charging at 50% on the genset, and stop charging at 80% on the genset. And you can recharge to >90% state of charge once a week (genset+sun+whatever), once a week (although, I as I remember, one member here contacted Rolls/Surrette engineering and they said once a month >90% was OK too).

Charging below ~80% State of Charge is very energy efficient for lead acid batteries. The efficiency falls between 80-90% SoC, and falls to near zero efficiency at 100% SoC (such as during equalization) when almost all energy is converted into gassing and heat.

As long as the batteries are cycling--They do not sulfate if they are actually cycling (vs just sitting for days/weeks unused below <75% State of Charge--When sulfation accelerates).

I am not a battery engineer--So I offer that as a starting point for research.

-Bill

ForeverHomestead · January 2021

Thanks for the advice guys. I have done some major repair EQ over the last week or so. My SG was very low and I have gotten it back up to 1.26. I wake up with allow more power than I was before. I think I will research the charging to 80% throughout the week and then get to 100 once a week. It most defiantly uses allot of power to get it up that far

ELYNN4 · January 2021

I have essentially the same battery bank as you. 48 Trojan L16 2v batteries. My daily power use in the winter is +/- 100 amp hours. I have my 9kw generator programmed to start after the batteries have been below 49.5 volts for two hours. The generator runs every 3 to 4 days. It takes about 4 hours to charge up to the 95% level and then I have a 6 hour absorb time. If I am around I run the generator manually to get the batteries up to the 95% level and then let the system run thru the automated charge cycle, with the 6 hours of absorb time, once each week. I have half a dozen problem cells that only get up to 1.25 after 6 hours of absorb time. They have always been my problem children from day one. The rest of the 128 cells play nicely. Once a month in the winter I equalize and the problem cells get up to 1.265, the rest get up to 1.277. The battery bank is 3.5 years old at this point and performing just fine. In the summer my power use is about 60 amp hours per day and the 4.5kw array can keep all the cells above 1.265. I have Hydrocaps on the batteries so I only need to top of the cells a couple of times per year. I live in Alaska so we have good sun from mid February thru mid October.

MichaelK · January 2021

Looking at the size of your battery bank, I think one reason why you are having charge issues is that your array is somewhat small for your system. I never thought I would ever refer to a 10,000W array as "small", but let's do the math. Assuming you have the Rolls S2 L16-E battery, and you want to charge at the recommended 1/8 capacity, then the math would be...

1040Ah X 2 strings X 0.125 capacity X 52V charging X 1.25 loss factor = 16,900W, call it 17000W

My bank is much smaller than yours, but I'm overpaneled for my bank size, and I sail through winters without running the generator at all. I finally discovered that the piston rusted in the cylinder, so now I run the generator every few months just to run the generator.

ForeverHomestead · January 2021

MichaelK said:

Looking at the size of your battery bank, I think one reason why you are having charge issues is that your array is somewhat small for your system.

I think you are right. I did not design the system and did not know allot about it at the time. Originally they called for one string of batteries. When I asked about autonomy they added the 2nd but did not change the size of the array. I have plans to add to the solar, but also am working on a hydro electric this summer to give a good source of charge in winter as well as cloudy days.

My batteries are the Rolls S-1415 batteries

MichaelK · January 2021

ForeverHomestead said:

My batteries are the Rolls S-1415 batteries

I'm not finding those on the Rolls website. What is their Ah rating? Whatever that is, just plug that value into the formula. It will then spit out the optimal solar value.

?Ah X 2 strings X 0.125capacity X 52V charging X 1.25 loss factor = optimal wattage.

I myself am over-paneled, but I have arrays on rotating mounts, so I can point one array SE and another SW to reduce noontime production. What's great though is at 7:30am I can rotate them all SE and make enough power to run my wellpump. They are made out of standard HomeDepot unistruts. In landscape orientation, you might squeeze between 1500 and 2000W per array. Add four of those, and I'd say you'd be OK.

Image: https://us.v-cdn.net/6024911/uploads/editor/a7/l0wpnmp8ha2j.jpg

ForeverHomestead · January 2021

I think they don't make them anymore. They are 1120 AH. I like you array. We lose sun on our panels around 1400 in the winter. I have 6 extra panels I was thinking about adding to the mounting to the west side of the barn to get a few more hours of sun. I like the movable idea. I will mount more on a steep angle for better winter production. I need to add a new classic 150 to it as well. I am maxed with the 3 I have.

Also working on starting a hydro electric this summer. Our creek flows all year

MichaelK · January 2021

Here's another pic of the frame before I added the panels. That gives you a better sense of the construction. What I did was cast a 3.5" schedule 40 pipe 3' down in concrete. Next I slipped on top the T-post I made with a 4" schedule 40 pipe. The top of the 4" pipe has a flat steel plate welded to it, then the horizontal unistruts welded to the plate. The T-post is re-enforced with the diagonal half-channel unistruts.

The actual solar frame is bolted onto the T-post via heavy steel hinges. This makes transport and assembly a 1-2 person job instead of the 3 person job. The long, vertical unistruts of the frame are 10' long, so you should be able to fit two rows of three 39" grid-tie panels on the four vertical unistruts.

Notice the trusses on the back to support the frame. They keep the frame rigid enough that high winds don't flex the panels to the breaking point. Notice that the two inner trusses are cantalevered over the hinge. I also added extra 14gauge earthquake anchors at each member to member junction, to increase strength.

If you look at the center of the T-post, about 30" above the ground, you can see two locking handles that screw down on the 3.5" pipe to lock it's position. Directly below that you can see two threaded stems sticking out of the pipe. Those are for the 3/4" conduit that is not yet added. That controls the angle at which the array faces the sun, which I adjust seasonally.

Like you, I lose sun by about 5pm on my main arrays. This array is positioned on the west side of my cabin to produce extra solar till after 6pm in the summer.

Image: https://us.v-cdn.net/6024911/uploads/editor/5v/egkcp4truzhc.jpg

ForeverHomestead · January 2021

Very Nice. Looks like a great summer project before I get into the hydro electric side of things.

Best Generator Use

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