Solar vs. generator run time

[Smitty77]

Originally Posted by WileyOne

I'm trying to learn as much as I can before I purchase my first inverter.

It sounds like you're saying that the charger is the bottleneck (limiting factor) for how fast you can charge your battery bank. I believe your Magnum can deliver 125 amps DC which is something less than 1500 watts. If your genny is cranking out 4000 watts, does that mean that 62% of the generated power is going nowhere?

If you were to connect a second 1500 watt charger in parallel, could you cut your charging time in half?

The MS2812 is a good combo inverter/charger, it is not a perfect device software wise!

The simple answer to your question is 'Yes' to faster charging of battery bank with an added charger. Probably not half.

But it's not a simple item to execute. The MS2812, and most 'Smart Charger's' (That was said with a smile, and at times I question how smart these things are! For sure, they try to Smitty/Idiot Proof them by removing some software choices as far as overriding the 'smart' programming!).

Most Smart Chargers, including the MS2812, have the traditional Bulk/Absorb/Float/Resting or Finished steps. With temperature sensor added to the equation. The Smart Chargers look at many variables, to determine how many Amps to send to the battery bank in say Bulk or Absorb. For example yesterday AM, after about 6 hours of HydroHot Diesel heating of just one of our two zones, we were at 67% SOC in the AM when I fired up the generator for it's AM 2 hour run. Some sun yesterday too, but at 8:00AM and where we are parked in the shade of Superstitious Mountain, no sun was on the panels until closer to 8:45AM - so not a factor. The MS2812 detects power, went into charge mode, analyzed the variables - and went into Bulk mode. Started at about 112A, but within three minutes was down in the 70A range of input to the bank. (Battery temperature was 57 degrees at the start. (Today, 50 degrees, as it 2as 27 degrees outside this AM!). The Smart Charger part of the MS2812, then tapers down the Amps being fed into the bank as time goes by. At the end of two hours, with a bits of sun hitting the panels too, the MS2812 was putting 33A into the bank.

So though it is capable of 125A, you can't really force it to generate that full power during the charge cycle.

Adding a second charger, say one that removes the Smitty/Idiot Proofing attempt, and has manual settings to allow me to set the parameters - would allow me to determine based upon battery temperatures and SOC level - the amount of Amps that I want to crank into the bank. And that would shorten the charging time. I'd probably run it back up to about 90-95% at higher Amp levels, then taper it back down to a float mode to finish off. (I'd turn off the 2nd charger, and let the MS2812 with the MidNite Classic 150 (With WhzBng in the mix.) - finish the full charge cycle.

And it's important to understand and follow the guidance of the specific AGM battery Manufacturer. Lifeline has documented in it's Tech Manuals, and also verbally when working with Tech Support - that they can handle quite amount of Amps being pumped into them. Other AGM, and Wet, batteries typically do not have that high of allowable juice to flow into them. (Not sure about Crown AGM's? But no Deka as one example, have lower values.).

And don't get me wrong in what I'm sharing. I have zero problems with how things are working for us. In 6-7 years of X's 4 L16 Lifeline AGM's, and 1250W of solar - I can count on one hand the number of times that I've gone more then three days without reaching 100% SOC. Solar usually takes care of us. When not, the generator/solar combo does.

I had the Batterymider 8A available to play with the other day... And if I did beef up my Auto Inverter (500W would not support a more robust charger power needs.) - I could run a second charger with more Amp's capability.

Good thread, with various opinions on how to approach power to feed our coaches. Many different combinations available, many price points, and many views on costs vs rewards - and again, all personal as to what is important to each of us!

Best to all, have fun, stay safe,
Smitty

[astrocamper]

For me it is what is silence (for you and your neighbors) and convenience worth. We live and camp in a very sunny part of the country. Did our own install of 400 amp-hours LiFePO4 batteries, 2200 watt inverter, and 985 watts solar. Almost all our camping is off grid. Spent about $30K on the trailer and about $10K on power related improvements. Took me about 4 weekends to get it all figured out, ordered and installed.

We are very happy with the system.

[rarebear.nm]

JT has it right.

Before adding solar to our 5th, we had to run the geny to recharge every day. Since we frequently are cooler areas, running the furnace at night is common to us. That furnace fan uses lots of 12v power. It would take about 4 to 6 hrs of geny time to get back to 97%. Never saw the geny (3500 watt) top off the batteries (460 AHR) at 100%.

After adding 1050 watts solar (three 350 watt panels flat mounted @ 44 volts measured on the down haul cable), and a Morningstar 60 amp controller our batteries at typically at 100% by 9-10 am every day regardless of our power usage. Only once in a year has 100% recharge been after noon. This was also true the entire time we in Canada and Alaska this past summer with cloudy days and tree shade. Some of the better panels today will produce reasonable power in less than direct sun and low sun angles. I ran all of the math for this design and the results have exceeded expectations, by a lots.

The choice of solar vs geny is largely personal life style and values. I suspect very few people will see their solar system payback over running the geny if money is your main justification. But, then for most of us we will never see a payback of buying our RVs in the first place. Most do it for the life style and/or freedom of travel. So its hard to accept the solar vs geny cost argument in most cases. I'd guess that many solar systems cost are similar to an auto leveling system, how do you determine its payback? Its a personal choice issue. We do not like the noise or fumes from the geny running for hours per day. Our converters have been turned off since the solar was installed, thus 100% of our 12 volt power is from solar alone. While in Canada/Alaska the geny ran for about 24 hrs total in four months, mostly for the microwave.

Everyone has different power requirements and a different energy budget. There is no solution that works well for every body. I've seen many solar systems that are poorly designed and/or installed and never meets expectations and owners wonder why.

[Reed Cundiff]

Astrocamper and ratebear

We seem to be on same page.

LFP can be charged at C if you have sufficient battery chargers. We have about 9.5 kW-hrs of LFP and 2.2 kW battery chargers. We do have a 1 kW generator but only used several years ago while camped in 100’ trees on Olympic Peninsula.

We do have 1400 W of solar so we are generally fully charged before noon as Astrocamper. The solar charging is through a 45 Amp MPPT controller. Voltage is 90 V from panels and 48 V to battery bank
Reed

[followingsea]

Originally Posted by rarebear.nm

That furnace fan uses lots of 12v power. It would take about 4 to 6 hrs of geny time to get back to 97%. Never saw the geny (3500 watt) top off the batteries (460 AHR) at 100%.

I take a different approach to breaking the silence by running my generator.

The first step is conservation. I only need to run generator 1 hour a day, two if the furnace is running.

My blower is about 300 watts. Here is the interesting thing. If the blower is running the silence is broken. The biggest TV is 50 watts. If the TV is running the silence is broken.

The power usage for enjoy the silence is maybe 40 watts if you are sitting under the awning, hiking or sailing.

[Itinerant1]

Originally Posted by followingsea

I take a different approach to breaking the silence by running my generator.

The first step is conservation. I only need to run generator 1 hour a day, two if the furnace is running.

My blower is about 300 watts. Here is the interesting thing. If the blower is running the silence is broken. The biggest TV is 50 watts. If the TV is running the silence is broken.

The power usage for enjoy the silence is maybe 40 watts if you are sitting under the awning, hiking or sailing.

After reading this post I had the image of a cave troll for some reason.



Or I'm losing it from the silence of the solar.

[Reed Cundiff]

Itinerant1 - well played. He does make sense in that conservation is important and that there are better things to do then to be in the RV. Hiking, kayaking, reading, wildlife watching, talking. Internet is out of range most of the time with dispersed camping (a blessing). Other than that, he is right and the rest of us are wrong.

We did get a used (1969 or earlier) Klepper kayak with basically unused skin. It tracks in cross winds. Our older blowup kayak just spins in winds.

Reed and Elaine

[HaRVey 74.5]

I put 680 watts of solar and swapped to Lithum batteries on our brand new 2018 Palazzo just so I wouldn't have to use the generator most of the time (I prefer to hear nature and not generator whenever possible) and our first dry camping trip when using the generator to run the AC for a minute, the flywheel bolts came loose on the generator, making an awful racket. So we were very happy we had the solar!

[outdoorplay]

Originally Posted by Freqz

You’ll never come out ahead vs a generator that’s already purchased on a strictly dollar basis.

It might be worth it to you to stretch time between generator runs though...to the point where you’re eliminating them entirely unless you need AC. Of course, with a larger converter/charger and more batteries you could reduce runtimes and increase intervals if you’re not adverse to running the gen and don’t camp in no-gen places.

that's not true on all trailers, I sent the last 4 months looking at new units and there are a lot of mid-range 5th wheels that do not come with a generator, prime example is AZ trailers. and at $4,000 I can buy a lot of solar for that.

(however, I did buy one that had a generator.....)

[PbdBlue]

We went with 650 watts of rooftop solar + 200 watts portable for when shaded. Replaced LA batteries with 200Ah of LFP. We have an adsorption fridge. For years ran a Honda 2000 but since the solar\lithium upgrade haven't used it in almost a year. We boondock about 80% of the time. Is solar the most economical solution? No but I love it!

[Searching_Ut]

Personally, I didn't find the solar to be that expensive doing it myself. 4 gc batteries cost less than $400, and I don't really count them as my rig is a power hog and I would have gone that route without solar. Same goes for the trimetric and also the inverter as my TV's recliners, stove vent and range light etc. all require ac power to operate, and it's more convinient to use with my cpap, phone and computer chargers etc.

Solar itself, 10x100 watt panels about $850 delivered. Metal to make brackets, charge contoller and wiring and I was at approx $1300 for the solar itself. Since you'll be running the gen a whole lot less with solar, just by a predator 3500 instead of a honda 3000 and you made up the difference.

[saddlesore]

If only 4 hrs of generator time allowed per day @ the Lost Dutchman area..will just scratch that area off of our "go see list". and let those who do not require A/C to enjoy.

[Freqz]

Originally Posted by outdoorplay

that's not true on all trailers, I sent the last 4 months looking at new units and there are a lot of mid-range 5th wheels that do not come with a generator, prime example is AZ trailers. and at $4,000 I can buy a lot of solar for that.



(however, I did buy one that had a generator.....)

Huh? Or, as my rhetoric professor was so fond of scrawling in giant red letters on underdeveloped arguments, so what?

[twinboat]

Battery charging in 3 and 4 stage chargers is controlled by voltage, only.

No matter the size of the charger, it will drop out of constant current ( bulk or maximum amp output ), once the voltage reaches the absorb point, about 14.7 volts

If you start your charging at 70% DOD ( depth of discharge ), the voltage is going to climb to 14.7 volts quickly, depending on the size of the battery bank. At that point the charger switchs over to constant voltage, in absorb mode.

When it switchs over to constant voltage, the amp output will start tappering back. Higher amp output will push the voltage up. That along with the increasing internal resistance of the battery is why the amps keep tapering off.

If you want to get the fastest charging from your high output chargers, you will need to run the bank down to a minimum of 50% DOD and shut down at 80%.
Beyond 80% the charging is very slow. Best left for solar.

If you want to re-charge fast, use the middle of the battery 25% to 75% DOD. Sure your discharging your bank deeper but that's what deep cycling is.

You could use a smaller bank of batteries, deep cycle them, and replace them sooner. About the same cost but extra work replacing them.

I you only want batteries to last a long time, use the top 30%, but be prepared for longer generator run times to charge them.