Gdetrailer
PA
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spoon059 wrote:Couple of thoughts... I suggested a mini-split which would draw significantly less than 21 amps or 1000 watts. From what I am reading a 12K mini-split pulls about 4 amps at maximum draw and throttles down substantially from there. I've seen plenty of Youtube videos of people running mini-splits off 8 panel solar systems with larger battery banks. Its doable, likely for about the cost of a typical onboard generator.
I simply don't want to pay those prices to make it silent, so I'm leaning back towards a $1200 Honda 2200 for the occasional dispersed camping.
But, it is absolutely possible with a reasonable solar array and not nearly as expensive as your model.
Doubtful.
Looked at a MR Cool 12K BTU mini split which uses inverter technology compressor, calls for minimum 14 ga wire which would be a "15A" circuit..
They are claiming 7.8-10 BTU/watt for efficiency in their brochure HERE
4A at 120V is 480W and at the max of 10 BTU per watt that gets you 4800 BTUs worth of cooling.
You would need to find a mini split well under 9K BTU that might get you closer to that magical "4A" at 120V range.
4A at 120V is most likely a very small window air like 5K BTU if it was using inverter technology compressor and low fan speed.. But unless you have a small TC or sub 17ft TT, 5K BTU isn't going to cut it in 90F+ temps with high humidity.
Lets face it, in most RVs even a 13.5K BTU A/C barely gets it done.
On edit..
Found a Bosch 5K mini split that runs on 120V HERE (out of stock of course).
So, there is some very small 5K BTU mini splits out there, but in most RVs 5K BTU isn't going to be of much help.
You almost need to check on sizing the system, found a guide on sizing a mini split (or any A/C for that matter)HERE
"To determine the size of a mini split, calculate the square footage of the room and multiply it by 25 to obtain the cooling capacity needed in BTU. Then, select the nearest mini split size based on the calculated BTU.
For instance, a 500 sqft room requires a 12000 BTU mini split because 500 sqft multiplied by 25 is 12500 BTU and the nearest mini split size is 12000 BTU.
As a rule of thumb, we use about 25 BTU per square foot to calculate the cooling capacity needed for a room. Because mini splits have several fixed capacities, we have to select the one that matches our needs.
But, we don't always need to use a rule of thumb of 25 BTU per square foot. Generally, anywhere between 20-30 BTU per square foot is acceptable to be used to calculate the capacity needed for room air conditioners such as a mini split.
However, the rule of thumb of 20-30 BTU per square foot is meant for insulated rooms or houses.
So, if your room or house is not insulated or, the insulation is known to be in poor condition, you need to double the rule of thumb figure or use 40-60 BTU per square foot to calculate the capacity needed thereby choosing the right mini split size."
RVs are very poorly insulated (R3 or less in walls and roof and R2 or less in the floor) and have single pane windows so landing on the oversized system typically is your better choice.
In my case, I have a 26ft TT, using 60 BTU per square ft gets me 12,480 BTU.. The 13.5K BTU roof air barely got the job done.. Now I have two Window units placed in cabinets.. 10K BTU for the main area and 6.5K BTU for our master bedroom.. Now we no longer lack for cooling.
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valhalla360
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spoon059 wrote:Couple of thoughts... I suggested a mini-split which would draw significantly less than 21 amps or 1000 watts. From what I am reading a 12K mini-split pulls about 4 amps at maximum draw and throttles down substantially from there. I've seen plenty of Youtube videos of people running mini-splits off 8 panel solar systems with larger battery banks. Its doable, likely for about the cost of a typical onboard generator.
I simply don't want to pay those prices to make it silent, so I'm leaning back towards a $1200 Honda 2200 for the occasional dispersed camping.
But, it is absolutely possible with a reasonable solar array and not nearly as expensive as your model.
The difference with inverter based mini-split units is they can adjust the draw to the output desired.
So if for a given rig at a given temp, it takes an average of 7500btu to achieve the desired temp:
- A 15k btu mini-split will draw power enough to put out 7500btu but run continuously.
- A 15k old style roof mount will draw power enough to put out 15k btu but run around 50% of the time.
Net effect is you need roughly the same amount of stored energy. Mini-split units might be a slightly more efficient but not a chance it's going to put out the same cooling btu at a 1/3 the power consumption.
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pianotuna
Regina, SK, Canada
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Gdetrailer wrote: No matter what "batteries" you use, they all need to be recharged as soon as possible, Lithiums are not immune to this and are not an exception if you want to get the most life for the money you spend.
I thought this was their main claim to fame???
* This post was
edited 08/18/22 09:24pm by pianotuna *
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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Gdetrailer
PA
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pianotuna wrote:Gdetrailer wrote: No matter what "batteries" you use, they all need to be recharged as soon as possible, Lithiums are not immune to this and are not an exception if you want to get the most life for the money you spend.
I thought this was there main claim to fame???
Lithiums do a much better job than FLA, AGM or gel, but they are not 100% immune to some degradation if you continually allow them to sit in a partial discharge.
Some of the claim to fame is the not to charge to 100% in order to store them. Reality is you don't really control the charge, the BMS does that. Allow them to store at too low of a charge and you take a chance the BMS will disconnect (BMS has low voltage disconnect built in and most BMS once that is tripped are not able to be reconnected) and now you have an expensive door stop. The Lithium battery pack will have a bit more capacity built in, often about 10% more capacity, but you typically cannot use that capacity due to BMS. The BMS stops you from charging or discharging more than 90% of the battery, good quality BMS will prevent you from using more that extra capacity. Basically that extra capacity is reserved for the BMS and also not allow battery to fall out of normal and stable state of charge range.
I have had some small Lithium batteries swell after being stored in a partial discharge state (inactive for 6 months or more and were not charged until the BMS stopped charging before storing).
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afidel
Cleveland
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All the calculations seem to be expecting to cool the whole RV, my plan is to use an inverter based 48V unit just for the bedroom, if it's above 80 when I'm going to go to bed start the AC 2 hours before and cool down the bedroom. With 2-3kW of solar panels and 10-15kWh of batteries this should be easy. It'll be about $12-15k with solar charge controller, Victron inverter, smart shunt, and misc parts.
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Huntindog
Phoenix AZ
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I have three 15K ACs. In Phoenix AZ, I would not want any less cooling capacity.
What mini split setup would I need?
Huntindog
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spoon059
Just north of D.C.
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Huntindog wrote:I have three 15K ACs. In Phoenix AZ, I would not want any less cooling capacity.
What mini split setup would I need?
Pretty sure you are mocking me ( ![[emoticon]](https://forums.goodsamclub.com/sharedcontent/cfb/images/wink.gif "wink") ) but I've talked to a couple people that have mini-splits in an RV, my parents have one in a multi-room addition they added to their house and I've read and watched a bunch of videos on them. The mini-splits are vastly more efficient than the roof top AC units in RVs. They aren't trying to blow cold air through inefficient and hot ceiling vent systems, they use a moving fan head to blow air throughout a space.
If your camper is big enough, or if you close doors, you may find that 2 mini-splits would work wonders in your camper. Looking at the cost of adding a second rooftop AC to a trailer (about $1200 MSRP), you can buy a DIY mini-split for about half that price.
From what I've experienced and read, the mini-split cools the space MUCH more efficiently, much more quickly, much more inexpensively and much more quietly.
Or, if you are happy with your 3 rooftop AC units, fantastic for you. Personnally I know that I can cool (and heat... its a heat pump) better, for less money, be more comfortable, hold a steady temperature, get much better dehumidification and do it for less money (initially and in energy used throughout its life time) using a mini-split than using rooftop ACs and propane furnace.
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Itinerant1
Itinerant
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Gdetrailer wrote:pianotuna wrote:Gdetrailer wrote: No matter what "batteries" you use, they all need to be recharged as soon as possible, Lithiums are not immune to this and are not an exception if you want to get the most life for the money you spend.
I thought this was there main claim to fame???
Lithiums do a much better job than FLA, AGM or gel, but they are not 100% immune to some degradation if you continually allow them to sit in a partial discharge.
Some of the claim to fame is the not to charge to 100% in order to store them. Reality is you don't really control the charge, the BMS does that. Allow them to store at too low of a charge and you take a chance the BMS will disconnect (BMS has low voltage disconnect built in and most BMS once that is tripped are not able to be reconnected) and now you have an expensive door stop. The Lithium battery pack will have a bit more capacity built in, often about 10% more capacity, but you typically cannot use that capacity due to BMS. The BMS stops you from charging or discharging more than 90% of the battery, good quality BMS will prevent you from using more that extra capacity. Basically that extra capacity is reserved for the BMS and also not allow battery to fall out of normal and stable state of charge range.
I have had some small Lithium batteries swell after being stored in a partial discharge state (inactive for 6 months or more and were not charged until the BMS stopped charging before storing).
The bms is the safe guard for the battery or more likely the cells within the battery.
A properly setup system has the charging device set to stop charging before the bms needs to interact. That's like saying my emergency brakes stop my truck no need to use the brake pedal while operating the truck.
LVD is also part of the bms which does protect the cells/ battery what quality battery manufacturer doesn't allow charging to wake the bms up when it meets their parameters?
Why buy a lfp battery if you're just going to store it, stay with dead lead and buy another cheap replacement when you kill it.
Small lithium batteries are not large lfp batteries, while your experience in lithium maybe useful my 6.5+ years seems to differ slightly using lfp setup fulltime everyday.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.
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time2roll
Southern California
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pianotuna wrote:Gdetrailer wrote: No matter what "batteries" you use, they all need to be recharged as soon as possible, Lithiums are not immune to this and are not an exception if you want to get the most life for the money you spend.
I thought this was their main claim to fame??? Don't panic. The statement is not true for any practical use.
Storage at 30% to 70% is less wear than being used. No charge asap is needed.
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valhalla360
No paticular place.
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time2roll wrote:pianotuna wrote:Gdetrailer wrote: No matter what "batteries" you use, they all need to be recharged as soon as possible, Lithiums are not immune to this and are not an exception if you want to get the most life for the money you spend.
I thought this was their main claim to fame??? Don't panic. The statement is not true for any practical use.
Storage at 30% to 70% is less wear than being used. No charge asap is needed.
This is consistent with my understanding.
- Lead Acid (which includes AGM & Gel) are happiest sitting at 100% charge.
- Lithium are happies at a mid level of charge. Taking it to 100% for a short period to get all the capacity is OK but leaving it sitting at 100% for long periods is not ideal.
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