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Old 10-01-2021, 12:09 AM   #127
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Originally Posted by Nomadist View Post
== The 12VDC / 24VDC / 48VDC Choice ==
Another thing to consider is going 48V instead of 12V. When I first stumbled across the idea I said to myself, "I don't need that, it's too much for what I'm doing!" and quickly pushed through specing a 12VDC system.

Well, here I am, 11 months later specing a 48V system.
My son has a Gree 9K Saphire SEER 38 on his 34' motor home. The SEER rating is not applicable unless one is full time and stays at one location year-round. But, the EER is 16.5, one of the best around. My C&H 9K 120V unit has an EER of 15.5.

He had the Gree before planning and building the solar power system in the RV. He went with a 12V system with a 3 kW 120V inverter based on simplicity, lower cost, and easy to source replacement parts. The battery to inverter is less than 3 feet and a second parallel 1/0 welding cable to the inverter (340 Amp rating) was the only concession to 12V.

He built an autotransformer from an ebay 1 kVA used medical equipment torroid transformer to get 240V for the mini split. It gets warm, but probably wastes only 10 or 20 watts.

I do wonder if a 48V inverter would have been more efficient. His probably does 85% on a good day. Do you know if inverter losses are the lower 10% you mention on a 48V dc to 240V AC inverter?

The 6:1 modulation range of the Gree is great, though I've been monitoring my sons unit (it has been in my yard in sunny northern CA most of the summer) and it runs up around 1000W most of the day and drops through the lower power stages fairly rapidly at dusk and back up by 9 or 10 in the morning. That said, his 2KW of solar covers much of the day use. Still, it's more of a power hog than he was expecting. Even with bubble wrap in all the windows, it runs hard through the day.

His RV, like mine, does not have shore power capability. That said, he can move his 9K mini split and autotransformer to a power cord (U-ground) and plug that into the post's duplex receptacle when available ... and he does expect to have shore power when it's up around 100F like it has been this summer in Northern CA. His battery and solar powers everything else and will power the mini split as well when it's less than 90F out.

BTW, his outdoor unit sits under the front hood of his diesel pusher .... where the Onan 5.5 kW generator once sat.
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Old 10-01-2021, 09:57 AM   #128
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Originally Posted by Jim_HiTek View Post
I easily get 8-12 years from flooded cell batteries. The secret is using 2 oz of mineral oil per cell. And then my lackadaisical service routine isn't so important to battery life since the water stays in the cells. Doesn't hurt to have a 'smart' converter so they're not overcharged like in the old days.
I have never understood the presumed "science" behind the mineral oil. It "might" stop water from evaporating in a static state but I am unsure of the oils value when the water is being "boiled or percolated" during the charge cycle.

I know neither the "B or P" terms are correct but I'm not sure of what term best describes the chemical / electrical transformation that's occurring to the water when you can see and hear the water roiling and heat is being generated.
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Old 10-01-2021, 10:29 AM   #129
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Originally Posted by NorCal Hal View Post
I'm not sure of what term best describes the chemical / electrical transformation
Electrolysis. And with that process it's not water that's leaving the cells as it would being boiled or evaporated, but it's core components as gas.

Mark B.
Albuquerque, NM
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Old 10-01-2021, 11:05 AM   #130
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Originally Posted by Nomadist View Post
== The 12VDC / 24VDC / 48VDC Choice ==
Another thing to consider is going 48V instead of 12V. When I first stumbled across the idea I said to myself, "I don't need that, it's too much for what I'm doing!" and quickly pushed through specing a 12VDC system.

Well, here I am, 11 months later specing a 48V system.

The primary reason is so that I can install a 38-SEER mini-split heat pump. Once a unit goes above 25 SEER or so they run at 240V.

I want that efficient of a unit so that I can run all night off battery in cooling mode and run at high during the day in 110 °F heat with about 1300W of solar (rated; actual likely will be no more than 1100W since they will lie flat).

The current 23-year old Coleman/Dometic ac unit uses ~1400W to produce 13500 BTU of cooling. No way I can run it only off solar without dipping into the batteries. But then how do the batteries charge if I'm using all the juice for cooling? (I understand the newer units are not much more efficient—a major failing of the manufacturers, in my view.)

And it's so loud I want to throw it in the lake in front of me right now because I work fulltime in the rig. The mini-splits are whisper-quiet once they've reached the set temperature.

This 38-SEER model should use about 900W to produce 9000 BTU of cooling. That will be needed only during the day and only on the hottest days. At night, its lowest power draw is about 250W. That can easily be handled by the 5kWh battery I'm looking at with plenty left over to brew my morning coffee.

10 hours x 0.25 kWh x 10% inverter loss = 2.75kWh

All the above means buying:
• a 240V 5000W inverter with 48V input and a built-in MPPT solar charger (looking at the Growatt 5000 ES at the suspiciously low price of $899)
• a 48V 5kWh battery ($1500)
• a 240V to 120V transformer ($400)
• a 120V to 48VDC 25amp lithium charger ($259)
• 4 residential solar panels ($200 each)

It's possible to do the above with 12VDC but then the cables have to carry more amps making them more expensive and the equipment is more expensive (also because they need to handle more amps). One bonus is that I get a much larger inverter out of this; my microwave causes my current 120V 2000W inverter to pop making it usable only when I'm running the generator or connected to shore power.

Prices have really come down. I paid $1200 for my 12VDC 2.5kWh battery last November. Now, 11 months later, I'm getting double the storage for just 25% more cost.

Anyone want to buy a slightly used 12VDC 2.5kWh LiPo battery? ;-)

This fellow did it with a 120V system but he would redo it with a 48V system if he were to re-do it.
What is the capacity of those panels? I do the numbers and if you have 1200w panels, you will not produce more than 800wats hrs for about 5 to 6 hrs depending position of the panels and time of the year, so best scenario 4,8 kwh or 3 hrs fully draining the batteries, I think that will not be enough to run the a/c, also you will need to put a soft starter in the a/c to be safe because after an hr or hr and a half running the system will not support the start consumption,
Please keep us posted in the progress of your system
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Old 10-01-2021, 11:57 AM   #131
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Originally Posted by radar View Post
We are looking at a T@B 400 and pulling it with a medium sized SUV/CUV. This is new from T@B and although they haven’t indicated the brand of batterie yet they have indicated that they are now using a converter that is compatible with LFP batteries. Cool. A lot of our camping spots we plan to visit have powered sites but there are some that don’t have power. It will have 200 watts of solar on it but of course a lot of those unpowered sites are also treed, so not sure the solar is going to work well. Trying to avoid packing a generator. In a pinch we can always plug into the SUV I suppose.

Cheers.
You could install an additional power inlet to the solar controller and deploy portable panels remotely.
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Old 10-01-2021, 12:00 PM   #132
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Yes, but...
.
.
Our Concorde LifeLine 105ah 12v AGM were new in 2003, and serve us nicely with our rare 2-3% discharge and 1,830-Watts of photovoltaic.
.
I can hear the dis-believers -- "Two decades! No way!"
"Way!" I snort in retort.
How so?
By gentle aware use, our bank remains functional far beyond the usual, partly because we are extremely conscious of our draw-versus-fill, fill-versus-draw.
(Or, it was 'extremely conscious' early on.
These days, it is second-nature.)
.
2003, at the time we installed our bank, cost was less an issue compared to longevity and readability.
We need it to work.
.
As we peruse the fervor about LiFePo4 as a potential replacement for our cherished bank, we are yet to see any benefit... for our use.
.
We think a 'one-size-fits-all' dictate from a-high fails to (aka 'cannot possibly') address differences in individual use and needs.
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Old 10-02-2021, 08:44 AM   #133
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"Two decades! No way!"
What's the capacity? "Present" and "not dead" are not equivalent to "good". Perhaps the degree of capacity they offer is all you need which checks the box, but I suspect these batteries are far below spec. It is a testimony though of their construction and care, nearly all batteries succumb to some sort of trauma before their useful life is realized.

Mark B.
Albuquerque, NM
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Old 10-02-2021, 10:21 AM   #134
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Originally Posted by NorCal Hal View Post
I have never understood the presumed "science" behind the mineral oil. It "might" stop water from evaporating in a static state but I am unsure of the oils value when the water is being "boiled or percolated" during the charge cycle.

I know neither the "B or P" terms are correct but I'm not sure of what term best describes the chemical / electrical transformation that's occurring to the water when you can see and hear the water roiling and heat is being generated.
Of course a battery is NOT supposed to be 'boiled or percolated' so a modern converter is suggested if that's happening. One that will dial back to a float state once the batteries reach the proper SOC.

What happens with the mineral oil floating on top of the electrolyte is simple mechanics. As a battery is being recharged, sometimes bubbles will form on the plates. Eventually these bubbles are large enough that they detach from the plate and float upwards. When they reach the surface of the electrolyte, they are slowed by the layer of oil. Because of the viscosity of the oil, the bubble struggles to keep moving upwards. But it does, though slower now, eventually it reaches the oil to air boundary and because of the surface tension of the oil, the bubble busts with much less energy. The thickness of the oil reduces the energy of the bubble and after 100 years of usage and experience by others, 2 oz is the recommended amount per cell.

And that's the only trick to the mineral oil. It's viscosity reduces the energy of the bubble as it bursts (if it bursts) at the surface. This lessor energy lowers the height and energy of the acid cast into the air above the surface of the electrolyte too. Then ambient temp and air pressure has more to do with how far that acid will travel and whether or not it'll escape out of the vents. Sometimes, because of the atmospheric conditions and ambient temps, some acid will escape, so the water level in the battery slowly drops, which means you still need to service the batteries occasionally. I check the batteries every few months, but only need to add water perhaps once per year. I haven't had to remove any corrosion from either set of batteries or from the trays for years now. I no longer use any of those corrosion reducing products either.

One other benefit I saw with my last RV...a '94 Bounder. The converter was an old style so it did tend to overcharge plus the conditions conspired once to drop the water level in the batteries to 1" below the tops of the plates. I could just see them starting to warp when I discovered they were that low on water. But I could see oil coating those plates and after I refilled them, added more mineral oil, and recharged them they worked fine for several more years.

This method of reducing corrosion of flooded cell batteries with a layer of oil isn't something new. Edison endorsed it, and it's been around since his time. You still have to maintain your batteries, it's just that the oil makes it much much easier as there's no corrosion to deal with, doesn't require maintenance as often since the water stays inside the batteries, and gives them longer life.
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Old 10-03-2021, 12:19 AM   #135
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Lithium Batteries are NOT Worth the Extra Cost?

From the Trojan battery site

1. Can I use battery additives?
Trojan Battery, along with other battery manufacturers, do not recommend that you add anything to your batteries other than distilled water. Extensive testing has shown that most of these additives do not work as advertised; in fact, some may do more harm than good. Be aware that adding anything other than water to your batteries will void the warranty.


https://www.trojanbattery.com/tech-support/faq/

So beware that if you do don’t expect a replacement under warranty.

I would think if it helps, the battery manufacturer would be putting it in every battery they sell to put them ahead of the other manufacturers.

If someone could point me to a Scientific study that proves an additive would work, that is not sponsored by the manufacturer of the additives or the battery manufacturer, please do. I know of 1000s of golf clubs that would pay 1000’s of dollars for the additive.

I used to add oil to all my house lamps 40 years ago so I sill need too right…. Just because it was done 30-40 years ago does not mean you should do it today.

Of course switching to lithium makes this all mute.
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Old 10-03-2021, 10:42 AM   #136
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Lithium batteries cost 5 times+ more than golf cart batteries from Costco. I get 5 years from golf cart batteries with minimum maintenance. No special charging required - just plug in, generator, drive and solar panels. All my requirements are covered.


To break even (not counting the fact that the extra lithium $$ can be invested) I'd have to have the same motorhome for 25 years.That will not happen. I will not even alive in 25 years.


So why buy lithium? Is it just the latest "big deal"?


So don't buy them!!!! I think this guy just wanted to start what you people are doing!
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Old 10-03-2021, 10:45 AM   #137
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Good reasons for using oil:

1) Long endorsed by users, even Edison endorsed it.
2) The oil can be removed with a simple turkey baster.
3) It's very effective preventing corrosion & evaporation. Especially with modern, smart chargers.
4) iRV2 thread.

They're your batteries, do what you want. As for me, I'll keep adding the mineral oil because it works great and after 15-16 years of adding it, I haven't found a down side yet. But I'm not an extreme RV'er either.

I haven't read about a battery failing and returned under warranty for years. Usually it's the user that screws up and damages them. I suppose it happens but if that's a concern, buyers could just use them for a few weeks before adding the oil. That's all I did.

So it is my opinion that using Lithium is NOT worth the money when I can buy flooded cell for $89 at Costco (Interstate), add oil and get years of use out of them, with very little maintenance.
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Old 10-03-2021, 11:02 AM   #138
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Quote:
Originally Posted by Jim_HiTek View Post
Good reasons for using oil:

1) Long endorsed by users, even Edison endorsed it.
2) The oil can be removed with a simple turkey baster.
3) It's very effective preventing corrosion & evaporation. Especially with modern, smart chargers.
4) iRV2 thread.

They're your batteries, do what you want. As for me, I'll keep adding the mineral oil because it works great and after 15-16 years of adding it, I haven't found a down side yet. But I'm not an extreme RV'er either.

I haven't read about a battery failing and returned under warranty for years. Usually it's the user that screws up and damages them. I suppose it happens but if that's a concern, buyers could just use them for a few weeks before adding the oil. That's all I did.

So it is my opinion that using Lithium is NOT worth the money when I can buy flooded cell for $89 at Costco (Interstate), add oil and get years of use out of them, with very little maintenance.
Do fill the battery with distilled water to the top of the fill ring and add the oil on top of that or stop a little under the fill ring and add oil to bring it up to the ring - or doesn't it make any difference? What and where do you buy "mineral oil"? Is there any particular type, kinds, .etc?
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Old 11-21-2021, 08:51 PM   #139
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Oh Puleeese!
This argument has gone on for too long.

Ok.. here is a scenario for you. I plan to boondock. My basic starter config will be running everything in the rig, without the need for a generator running or shore power. My power demand is such that I would need 3 times as much space and 4 times the weight to have enough LA batteries to support the load. Lithiums will last longer than I will, will take up less space and less weight and require zero maintenance. If all you are doing is keep the fridge running between RV parks, LA is fine, you don't need lithium.. if you want to boondock for weeks at a time and hold a lot of usable power Lithium is a much better choice. My initial battery bank will be around 14000 usable watt hours, supported by 2200 watts of solar, and a back up sine wave 2500 watt gasoline generator.

I am replacing the roof AC with a mini split, deleting it and the Furnace, Also deleting the Onan 4000 and eventually the massive LP tank..

LA would not be practical in this situation. I can build a 24v lithium battery for this setup for a bit under $3k, how many LA batteries would it take to give me 14000 wh? .. short answer = a 28000w LA battery bank.
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Old 11-21-2021, 11:12 PM   #140
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..... if you want to boondock for weeks at a time .....
LA would not be practical in this situation. .....
It is not what I plan to do, it is what I do. I do it in vintage MH without modifications.

LA is the king of practical.

Consider spending more time boondocking before you start making modifications.
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