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Old 09-16-2020, 08:46 AM   #15
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Originally Posted by geordi View Post
Great - it confirms what I said - less than 50% discharge is recommended.

You want to go deeper, knock yourself out. But it will be reducing the total lifespan of the battery.
So you buy 2 batteries every 3 years or you buy 4 batteries every 6 years.

If you can't fit 4 batteries, you use 2, and not sit in the dark with 50% charged batteries between charges.
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Old 09-16-2020, 09:58 AM   #16
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Battery University

What actually kills batteries fast is storing them below full charge or not fully charging them frequently. Fully charging requires 14 to 18 hours of charging.

The other thing is using them. The posts above explain what happens when you draw batteries down to 10% state of charge.

The second step is to fully charge the lead acid battery to clear all the sulfate deposits from the plates. The fine sulfate partials recrystallize to form larger crystals. The larger crystals resist being redissolved thus reducing storage capacity.

Check out some authoritative sources. Out of thousands of pages of information, no where does the Battery University say lead acid batteries are damaged by drawing down below 50% state of charge.

Battery Universityhttps://batteryuniversity.com/

How does the Lead Acid Battery Work? https://batteryuniversity.com/learn/...ased_batteries

Charging lead acid batteries https://batteryuniversity.com/learn/...d_acid_battery

AGM https://batteryuniversity.com/learn/..._glass_mat_agm

How to Charge and When to Charge? https://batteryuniversity.com/learn/...o_charge_table

How to Store Batteries https://batteryuniversity.com/learn/...tore_batteries

Summary of Do’s and Don’ts https://batteryuniversity.com/learn/..._battery_table

Charging with Solar, Turbine https://batteryuniversity.com/learn/...ar_and_turbine
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Old 09-16-2020, 11:56 AM   #17
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My point is most people don't track their battery state of charge because they are not equipped or knowable to do so.

I believe solar is very useful for extending lead acid battery life because it will automatically bring the batteries up to full state of charge as long as the RV is exposed to sunshine.

I sold a 5x8 cargo trailer converted to equipment hauler and bedroom to a friend. After 11 years the pair of Trojan T105 batteries are still going strong. They have been connected to a 15 amp MorningStar SunSaver MPPT controller feed by 240 watts of solar. They rarely where discharged below 50% and always reached 100% SOC by mid-day afterwards.

The bulk of RV people don't pay attention to their battery until it fails.

I currently use seven 100 amp-hour BattleBornBatteries and use a Cerbo GX, BMV-712 and four VE MPPT solar charge controllers to keep my batteries appropriately charged. I have a VE Multiplus 3000VA inverter/charger that never needs to actually charge the batteries because the solar charging is enough.
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Old 09-17-2020, 07:53 AM   #18
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My point is most people don't track their battery state of charge because they are not equipped or knowable to do so.

I believe solar is very useful for extending lead acid battery life because it will automatically bring the batteries up to full state of charge as long as the RV is exposed to sunshine.

I sold a 5x8 cargo trailer converted to equipment hauler and bedroom to a friend. After 11 years the pair of Trojan T105 batteries are still going strong. They have been connected to a 15 amp MorningStar SunSaver MPPT controller feed by 240 watts of solar. They rarely where discharged below 50% and always reached 100% SOC by mid-day afterwards.

The bulk of RV people don't pay attention to their battery until it fails.

I currently use seven 100 amp-hour BattleBornBatteries and use a Cerbo GX, BMV-712 and four VE MPPT solar charge controllers to keep my batteries appropriately charged. I have a VE Multiplus 3000VA inverter/charger that never needs to actually charge the batteries because the solar charging is enough.
First, the charge profile of Battle Born's is of course significantly different than lead acid. Comparing the two types is pointless.

Second, It is highly unlikely that solar power will fully charge the lead acid battery bank in one solar cycle. Possibly it would work in the far northern summer or above the arctic circle.

Solar may fully charge during storage if next to nothing is being drawn from the batteries overnight. It may take two or three days.

If you don't fully charge for 14 to 18 hours periodically, battery capacity will slowly deteriorate due to accumulation of large sulfate crystals on the plates. If you do fully charge periodically, the lead acid batteries will provide 300 to 400 full discharge cycles. 50% discharge cycles would provide 600 to 800 cycles. That amounts to more than 10 years for my battery banks.

I often camp for 5 days at a time. I fully charge at the end. I usually camp once per month. That usage provides more than 10 years of life.

I wish you good luck and happy trails ahead!
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Old 09-17-2020, 10:30 AM   #19
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I used my 5x8 cargo trailer for camping from 2009 to 2018 when I sold it to a friend. I would see my pair of Trojan T105 batteries fully charged by mid day everyday. I had 240 watts of solar on the roof. My demand wasn't huge. I had LED lighting, Engel freezer, fantastic fan, laptops and astronomy mount and camera.

The batteries are still working fine after 11 years because of the daily full solar charging and light discharge cycles.

We camp in open unshaded areas that are suitable for astronomy. The Great Basin is very sunny.
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Old 09-17-2020, 06:29 PM   #20
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900 watts / 12 volts = 75 amps at 12 volts. Add efficiency loss and other things running at the same time. Results are you need at least 200 amp hours of AGM batteries. I don't know the discharge profile of the Lithium battery.

Charging using a 400 watt solar array will vary a lot. You will only get 20 amps on sunny summer days for a few hours. The company selling the solar may provide examples of how many amp-hours you might get in a day under different weather conditions. Estimate your amp-hour usage and compare to what the solar might produce.

Charging lead acid batteries goes fast for the first few hours if you have a high capacity charger. A 100 amp hour AGM may absorb 30 or 40 amps for 4 hours. The lead acid still needs a long slow 14 additional hours maybe once per week to maintain full capacity and long life. A 20 amp charge for 6 hours will probably cause the battery to struggle to supply what you need.

Lithium batteries do not need the periodic long slow finishing charge. They can take their rated full charge from beginning to end. 6 hours at 20 amps will probably still be limiting.

I would choose a pair of lithiums over the mixed battery type. An alternate would be a pair of 100 amp hour AGM's. Pairs working together will support a 900 watt microwave for 10 minutes.

One lead acid alone will struggle. The inverter may trip due to low voltage on the 12 volt side. This is especially true when using the battery at low state of charge. For example, after running the furnace all night, the battery may not supply enough to keep the inverter running to support a microwave.

One 100 amp hour lithium may also struggle. Check with battery manufacturer.

Just a thought: A 1000 watt portable generator is enough to run the on-board charger plus a few other 12 volt things. Run the micro on the inverter. Charge the battery using the generator for 2 hours in the morning. Let the solar provide the long slow finishing charge all day.

I wish you good luck and happy trails ahead!
Do you know of a small inverter generator? like 1000w? Smallest i see are like 2kw. Maybe a small quiet regular one?
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Old 09-17-2020, 06:45 PM   #21
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Here's one... But for $100 more, you get double the power.

https://www.homedepot.com/p/RYOBI-1-...1000/205536859

Running anything like this at full-out is a good way to wear them out fast, and also use up way more fuel. I have the older 2k version (same as the one with wheels that is now 2200 watts) and it is very quiet and runs close to 8 hours on just ONE gallon of gas when half-loaded.

https://www.homedepot.com/p/RYOBI-2-...0GRA/308279711

Or just a touch more expensive and you get wheels and it likely will be even quieter.

https://www.homedepot.com/p/RYOBI-2-...0GRA/300404697
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Old 09-17-2020, 08:06 PM   #22
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You want to go deeper, knock yourself out. But it will be reducing the total lifespan of the battery.
It will reduce the total number of cycles. But it will increase the power delivered per cycle. So it's a wash.
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Old 09-18-2020, 07:30 AM   #23
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Do you know of a small inverter generator? like 1000w? Smallest i see are like 2kw. Maybe a small quiet regular one?
I bought a Honda i1000 over 10 years ago. It cost almost as much as a Honda i2000 at the time, but took up less space and weighed a lot less. Then, it was the only quiet reliable generator available.

Today there are many 2000 watt generators for a lot less money. Some are quiet, cheap, and reliable. I suppose most people buy the bigger 2000 watt gens so retailers don't stock the smaller 1000 watt size.
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Old 09-20-2020, 08:58 AM   #24
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I have a Champion 3100 inverter generator and I wish I had bought a Honda. Everybody says 'almost as quiet as a Honda'. No. If you want quiet, get a Honda.
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Old 09-20-2020, 09:19 AM   #25
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I have a Champion 3100 inverter generator and I wish I had bought a Honda. Everybody says 'almost as quiet as a Honda'. No. If you want quiet, get a Honda.
JK
I don't know about their inverter generators... But I had a "Champion" open frame generator and after just 150 hours in use it started banging loudly until very soon after, the cylinder head broke in half. Cheap chinesium cast metal. Never again.

The Ryobi uses a Yamaha engine so at least that is also as Japanese as the Honda.
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Old 09-23-2020, 02:49 PM   #26
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Continuing the thought process from Persistent's reply...

If you had TWO of those lithium batteries and they were totally flat, you would probably be able to finish them off to full each day... BUT that's with no other loads sharing the power at the same time. It's always better to have way more solar than you need, you can always just not capture, versus still needing more power when the sun goes down.
I'm at this point as I write... currently have 480W on the roof, another 120W portable. This week sees the install of a 100/50 Victron MPPT Solar Controller, a Victron 712 Voltmeter, and 4 - Battle Born Lithium Batteries @ 100Ah each. Thinking is, get all this installed, and then determine if additional solar is needed... but...

I'm of the belief that it is better to have it and not need it, than the other way around... considering another 2 panels at 340W, but may go larger with Renogy 300W panel, get two, and increase wattage to 1200W... with as much dry camping as I anticipate, this oughta handle most anything I'll need...
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Old 09-23-2020, 06:39 PM   #27
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When I designed and installed our solar system I used three 350 watt panels, 1050 watts total. The Morningstar control can only handle 800 watts. Since the panels are flat mounted they loose about 30% +/- of rated output to start with. Most of us rarely see the rated output as that's determined under standard testing conditions in a lab. I would guess the controller gets perhaps 60% of the rated value at best.

The bottom line is I've turned off the breakers to the converters when I installed the panels and have generated 100% of our 12 volt power from the solar system. On most days the batteries are back at 100% SoC before 10:00am. I have four 6 volt GC batteries for a total of 230 AHrs of usable power. I have not seen the battery charge level ever drop below 84% even running the furnace all night. This system works well for us.
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Old 09-23-2020, 07:32 PM   #28
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I have not seen the battery charge level ever drop below 84% even running the furnace all night.
I'm sort of in the same boat, but I wonder about one thing (and this looks like a good time to find out):

Do we NEED to be dropping our batteries down lower periodically? Is there any memory issue here?

(Asked out of ignorance, so be gentle.)
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