House Battery Charging - Generator and Solar Panel

[Smitty77_7]

We've had our Solar Panels now for about three years. For the first time, we're in a spot that has a mix of shading we've never encountered. We get early AM 75% shading until about 9:30-10:00AM. Then we have full sun, except for an occasional cloud passing thru, until around 3:15-3:45PM. Them, due to the leaves rapidly dropping from the tree that is shading us in the afternoon, we have a diffused sun up until about 6:45-7:00PM. Still sun until 7:25PM, but at such a low angle, the Midnight Classic is reflecting less 2 - 7.5 AMP.

 

My question. Is it better to run the generator in the AM, then let the SP complete the charge when it has the full sunshine. Or, let the SP do it's thing, and then run the generator later in the afternoon or early evening to top off? (We can run generators in this campground, up until 10:00PM. And a few people do so. The gent two spaces down came to apologize to many of the campers in the site near him. He said he found out on this trip, that his house batteries are just about shot. So, he tries to give them as much as he can, as late as he can, from the generator.

 

Just a side note. If the evening cooking requires the convection oven, we run the generator at that time too.

 

Have never been in location where we have almost enough of sun to get the charge back up to 95% SOC, but sometimes a bit short at 89-92% SOC. So, using the generator in combo with SP's more then I have before.

 

Appreciate any tips!!! Best to all,

Smitty

[baphenatem]

As a rule in solar design we shoot for no shading between 9AM and 3PM, since that is the time frame when the maximum amount of solar insolation is available. The earlier and later hours are of less consequence since the effects of the sun angles and atmosphere limit the available energy to be harvested. That having been said, if you are monitoring your batteries with a good charging monitor and if you are getting close to a maximum charge it probably makes more sense to get what you can from the sun and then top things off with the generator in the late afternoon. There's no point in using fossil fuel to do what the sun can do for free, or at least that's my take on it.

[oldjohnt]

Smitty, here is my approach to your situation. Id start the day off on Solar BUT IF AT ANY TIME MY BATTERIES REACHED 30% DISCHARGE STATE ID FIRE UP THE GENERATOR. I don't care if its morning noon or night, I don't like letting my batteries exceed 30% discharge. I don't like to draw them down

any more then necessary, I don't even like them 20% down but used the 30% as a reference. A battery has so many Life Cycles and the less you use them up (IE don't let them discharge) the more battery life you end up with.

 

John T (Live from Zion Natl Park)

[Yarome]

In that type of situation, I would run your genny in the AM to do your bulk charging.then let your panels top them off in absorption. Personally, I don't let my battery bank fall below 80%. If you are, regularly,,discharging into the 20 and 30 percentile I would highly recommend enlarging your battery bank.

 

To get the maximum life from your battery bank, I would highly recommend keeping your discharge rates to 50-70% at the least.

[skp51443]

I take a bit different approach depending on my battery charge level and how much sun I expect. My goals are fully charged batteries but with minimal generator use.

 

First the easy case where I'll get enough sun to charge the batteries, just let the sun do the work.

 

Second is where I know I'm going to come up short and have to use the generator. Since the generator can pump a lot of amp hours back in fast if the batteries are in the bulk-charge range I fire up the generator early and get some or all of the bulk charging done. Some if I think I'll have enough sun to get to a full state but tending to go longer if the sun is weak or shaded. You can get a feel for how long to run the generator if you watch when the charger switches to absorption and then float.

 

Using the generator during the absorption phase isn't efficient as you aren't putting many amp hours back into the batteries at that stage, far better to let the sun top you off if there is a good chance it will.

 

Even if you come up short one day as long as you get to 100% the next day you won't be courting getting sulfate crystals built up and hardened. Longer than 48 hours is iffy, longer than 72 is worse so getting to 100% is important for battery life.

[baphenatem]

After some further thought, I have to agree that if you know that you'll come up short using solar only, then it is best to use the generator earlier, during the bulk charging stage in order to get the charge into the batteries as quickly as possible. You can monitor the input and shut down the generator at the point where you're fairly confident that the solar can top off the batteries during the absorption phase.

[Smitty77_7]

Thanks all! That was my thinking, that get the heavy lifting done with the generator, and top off via solar panels.

 

We have 1200W SP, feeding 800AH Lifeline house bank. The MidNite Classic150 will quite often reflect 45-50A during peak hours.

 

One final confession, I realized that I've been neglectful on resetting my Magnum BMK Meter when at full charge. Highly probable my stated SOC are off at this time. I'll burn some dino fuel to be sure I reach 100% full by end of day, then reset the SOC. (I was very good at resetting the BMK at the end of long days drives, at least weekly. Somehow I spaced out on doing so. Probably has been over 6 weeks + since doing so. I've asked my 'Voice of Reason', wife, to help me in remembering to do so on a regular basis!)

 

The MidNite Classic 150 has the WhzBangJr installed, but I have not wanted to update the Controllers software to incorporate it while traveling. Like to do those kinds of changes, while at home, so that if I mess something up I have time to correct it. When the software is updated, I'll have and additional SOC to reference. Both feeding off the same shunt. I told my wife, that is good and bad, same as looking at temperature gauges when they have different readings - which one do you believe! But, as all of this really only an approximation of charge, if I'm within + or - 5% on the readings, I'll be happy.

 

Generator hours start in 10 minutes, and luckily the campers near have either left for the day, or gone into the park and should be gone for quite awhile. (In Gros Ventre in the Tetons.) So a long generator run should not disturb them:)!

 

Thanks again for the feedback!!

Smitty

[baphenatem]

One other thought on this; there is nothing that says that you have to charge to 100% EVERY day, provided that your depth of discharge (DOD) is not excessive. If you are not going beyond a DOD of 30% (state of charge (SOC) of 70%) or even 50% and the solar is getting things back up to 90% or so on a daily basis, without the generator, you could simply top things off every four or five days with the genny and call it "good enough". As Yarome pointed out, it's the DOD that kills the battery (along with about a half-dozen other things). If you are faithfully monitoring and making the necessary corrections as needed you could significantly reduce the run time on the generator.

[reed and elaine]

When we had to use a generator, we started off using it in the morning as Yarome, baphenatem and Stanley suggest. (#4, 5, and 6). One wastes a lot of fuel trying to get the lead acid batteries to 100%. Hope Smitty is not reflecting all the solar.

Reed and Elaine

[Smitty77_7]

When we had to use a generator, we started off using it in the morning as Yarome, baphenatem and Stanley suggest. (#4, 5, and 6). One wastes a lot of fuel trying to get the lead acid batteries to 100%. Hope Smitty is not reflecting all the solar.

Reed and Elaine

 

 

Not much reflection going off of those 5 panels at the moment! For a great reason, covered with golden yellow leaves!! Will up to clean them off!

 

And yes Tom, I agree with your comment. On this trip, now ending month three, we've very seldom gone more then 4 days without having at least a 30A electric hookup. Between that, and the alternator topping off between destinations, we have more often then not, been at 100% SOC. When without power, I usually am at between 70-75% SOC in the AM, 30 mins after the electric brewing of our coffee. So doing well on not dipping too low. We hit a 'stated' 67% SOC yesterday for the first time, that was when we were at 89% SOC at around 4:30PM. I strive to reach 95% or above, before going into our night time cycle. (Usually, we're at 100% SOC every day via mostly Solar Panels.) So, we do keep the SOC levels protected, and topped off fully regularly, to protect the investment in the Lifeline's:)!

 

And with my poor maintenance of resetting the BMK, I suspect those SOC's are not accurate. Will be reset today, and we'll see. We have four more days in Gros Ventre, and then four more days in Madison Campground, Yellowstone. I expect to be in more shade, pines, at Madison!

 

Smitty

[Jack Mayer]

When we had to use a generator, we started off using it in the morning as Yarome, baphenatem and Stanley suggest. (#4, 5, and 6). One wastes a lot of fuel trying to get the lead acid batteries to 100%. Hope Smitty is not reflecting all the solar.

Reed and Elaine

And that is the way we do it as well. Taking advantage of maximum battery deficit for maximum (fastest) bulk charge input. Then finish with solar.

[Smitty77_7]

I did find one other setting that was not where I thought I had set it. The RC50 & BMK-Meter have a Charge Efficiency Setting. My notes clearly show that I had left it with the default setting of 'Auto'. I wen with Auto, as it compensated and considered several variables, like age of battery for one, and after reaching 100% SOC, it 'resets' from a new baseline of simple in/out usage as the primary determination of SOC (And others, again like age of battery.) This was the item I was referring to needing to go back and reset. As the tech I work with often, had suggested I try it on a 95% Charge Efficiency Setting for awhile. (I had forgotten I had OK'd him making this change, while talking with on the phone about a stereo instal.)

 

3 1/2 hours of generator to reach 90% SOC by 11:45AM. We went out for a hike, and at 3:00PM we were stating 100% SOC, from the SP's topping things off.

 

If I understand the 95% Efficiency Setting, and how it works into the calculation of SOC, simply more AH's would have needed to be 'put back in' to the battery bank, then if it were on Auto.

 

Will run with this (Again, it is how we operated for out trip to Alaska last year, with probably 65% of the time being off grid, but with looonnnngggg sunny days too:)! for the next few weeks, and see if what I consider normal SOC behavior returns.

 

Again, appreciated the input on do the heavy lifting with the generator in the AM, and letting the SP top things off.

 

Best to all,

Smitty

[skp51443]

Do some reading on leaving your batteries below a full charge, it can lead to crystals forming in the plates and hardening. Over time that can lead to plate warping, shedding and a general loss of capacity. I planned on a full charge every 48 hours but faintly recall 72 not being a problem.

 

These folks think longer between full charges is ok.

 

http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it

 

Here they mention 24 hours.

 

http://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html#8

 

So opinions vary, pick your favorite I guess...

[Dale P]

I believe topping off whether in the early morning or evening, evening is best. But it really will depend on the Inverter/Charger you have and how it is setup for the absorption mode. That is if you have a Good Charger/Inverter. i.e 3 or 4 stage charging.

Once it is started, it will enter into Bulk Mode. Depending on the SOC, it CAN hit the Bulk Voltage Cutoff, and transition into the absorption mode. The absorption mode is Time Depended and is based on your battery capacity and how you set it up.

At a min, you need to preform a deep charge twice a week using your generator and inverter charger letting it go thru the whole process.

[oldjohnt]

One more factor to toss into the mix is when we stay at nice QUIET peaceful Natl Forest Camps (especially if tent campers are nearby), even if Generators are allowed at certain times I JUST HATE TO START ONE UP IN THE PEACEFUL QUIET MORNINGS. Also some Natl Parks (and Forests) only allow Generator operation at certain time periods. Of course if you're all alone or in dispersed camping locations these considerations go away.

 

All in all I agree to the use of a Generator (assuming it powers a quality smart charger) during the initial BULK CHARGE stage, but stick to not allowing the batteries to go beyond 20% to 30% max discharge, at which time if Solar doesn't suffice its time to start the genny or move where it can be used.

 

Currently in Carson City Nevada having been 12 days out and all dry camped so far and never a problem from a combination of Solar and Generator and engine alternator. I may have dropped to 20% discharge at some point but never below.

 

John T

[Smitty77_7]

Thanks for the added tips and opinions!

 

And yes to the quiet AM's of a National Park... We have a bull moose, two teenagers and a another two females in the meadow outside our loop of Gros Ventre every AM. Maybe a 100' at most, at times, away. They sort of ignore all the people getting close to them for pictures. Even when others start their generators, I just don't like doing it, though they seem to ignore those too:)!

 

MS2812 set to the Lifeline AGM charge setting. So bulk really cranks in the amps, I've seen over 120 A at start up, quickly settling to 100 A + or - 5 for a good period of time.

 

At 78% at 6:00AM today, before the coffee was brewed! So, kind of back to what I consider the norm.

 

Best, and thanks,

Smitty

[shaman52]

When boondocking I run generator in the morning. Running generator later in the day results in more diesel fuel consummed. Your Lifeline AGM batteries can take the big in-rush of amps as you have stated. This is a real advantage for the AGM over typical lead-acid types. I have a 3.1Kw MSW inverter and have seen as much as 160 amps initially. 78% battery in the morning is a good point to be at.

 

Good Luck!

David

[shaman52]

To save battery power in the early moring, I brew coffee on the gas burner using a Venus Espresso Coffee Maker, Stainless Steel, 4 cup

by Bialetti. http://www.amazon.com/Venus-Espresso-Coffee-Maker-Stainless/dp/B00067WBU4

Makes a descent cup of strong, yet smooth coffee. I grind Italian/expreso roast beans only during generator run times.

Good Luck!

David

[Smitty77_7]

Bialetti makes a good cup of joe, have one at home. We do have an old Revere Ware (Was my parents, a wedding gift from 1946.) with the copper bottom. It makes 10 cups, and we use that when we're off grid and know that we'll have little Solar Panel output.

 

I bumped up from a 2K modified sine wave, to the Magnum PSW. Good price, and more power for the addition of HiFi (Got Tubes?) and Samsung. I considered adding a dedicated PSW smaller unit to do fridge duties, for the lower idle consumption. But frankly, felt I had enough battery bank to more then adequately support our usage. A repeat on this comment, my timing was off on the newer breed of hybrids, I would have really liked to have had that unit, for when in parks where we pay for power consumed.

 

You know, I sometimes how we ever made it in our 98 Bounder, with only two T125's:)! Zero solar panels... But we did, and dang if we did not have as much fun in it, as we do our current coach:)!

 

Best,

Smitty

[kinseypw]

Have you considered getting one additional solar panel and have it free standing in the sun? We have 400watt of solar and 500amp hour batteries and generally have them going to float by 2-3pm even up here in Canada ( S Alberta for the next week). We have the panels free standing rather than on the roof and find that they give us bags of power. We dont usually have to move them except on cloudy days and generally dont run our generator more than 3-4 days every 6 months. Pictures here http://pjsnowbird.ca/index.php/tutorials/installation

[Smitty77_7]

Having a mobile panel, as with a dish, can come in handy based upon where you are parked:)! At this time, we have neither.

 

If we find we're doing more boon docking in areas that don't provide adequate direct sunlight, or dish coverage, or both, we can add these. For now, we're doing OK.

 

I was just confused due to a post I read on another site, that recommended waiting to top off towards the end of the day with the generator, vs running it in the AM. Did not match what I thought I had understood, and figured I'd get some straight answers from here - and I did:)!

 

Best,

Smitty

[Forest Grump]

This is a very interesting thread with a lot of nuances. The major being the design of the system. How much battery, how much solar, power management, how much usage and being able to efficiently deliver those necessary recharge amps at the right time.

 

We love to boondock, at high altitudes, full sun. But, we love to camp at Twin Lakes in Mammoth, heavy tree cover, big tall lodge pole pines. Lucky to get 1 to 3 hours of prime solar in. Batteries two Trojan 6v for 360 Ah, J185H. Solar 3 X 160 watts 27 amps. Battery Minder desulfonator.

 

My design goal was to replace the amps we used in two hours, go into adsorption then hopefully float each day. At Twin Lakes we were there five days. I also would take the 12v 100 Ah Trojan trolling battery and using 6 gauge parallel wiring take it back to 12.7v. Yes you can do it. Any port in a storm. Never got to float with solar, always had some solar for about 7 hours. Usually got to adsorption each day. Each evening the batteries were fully charged at 12.7v and the battery minder desulfonator active for the 7 hours of charging. Next 5 days June Lake, 12 miles away, full sun. Reached float first day.

 

Never used the generator.

 

Lots of ways to do it. Lots of good ideas. I've been very pleased with the battery minder desulfonator. Had 5 marginal days but I'm pretty sure it made them better as far as overall battery health is concerned.