Hello all, first post here. If all goes as planned, I'll be getting a 27ft or so sailboat shorty, and I'm going to try to cool the v berth with a very small ac. The plan is to run it at night on battery power so I can at least sleep at night and get out of the worst of the Fl heat during the day as it runs on pretty much solar only. I'll be living on the boat. I do realize it's minimal, but all I need is just enough to get by for now and the v berth is very small. They also make a 2,500btu but I'll get figures on the small one first and go from there, as it may be worth moving up the the larger unit.

The unit, and specs are here:.....

https://cozywinters.com/shop/dog-ho...ze145deAtuQKRIIp3l7nshWV0bubUZ5xoCb6gQAvD_BwE

....and I'll also post the specs below.

I assume this thing will run continuous on say, 400W of solar panel in full sun but it would be nice to know as close as possible how many watts of solar it truly would take after all loss is figured in.

And of course I need to know what size (in normal deep cycle speak) and how many deep cycle batteries it will take to run the AC, say, 8rs constant.

In summary

1) How many watts to run it on panels only, draining nothing from the batteries, in full sun?

2 ) Mainly, how many/what capacity batteries to run AC 8hrs on nothing but battery? Then if you would comment, the best battery set up for my needs (cost matters) and maybe even the best place to buy the deep cycle batteries.

I have a Centech 2000w/4000peak inverter that should at least run that fine. And I just realized we'll need charge time to get the batteries ready for another nights work, so I guess we need to figure that into the system as well. Thanks so much for your help, as I have always been terrible at math, even dropped out of electronics because of that, and though I've tried, I just decided to settle with the fact, I need help for figures like this and appreciate any I can get here.



Details Specifications for the Dog House Air Conditioner Unit:

• Cooling btu: 1,400
• Cooling Capacity**: Ideal for up to 40 cu. ft. dog houses
• Volts: 120 volts
• Amps: 3
• Watts Input: 350 watts
• Thermostat: Adjusts from 32 to 90 degrees F
• Controls: Covered On/off Switch
• Unit Dimensions (unboxed): 9" x 8" x 13"
• Weight (net): 27 Lbs.
• Refrigerant: R-134A
• Noise - Inside: less than 10 decibels
• Noise - Outside: 65 decibels
• Color: Off White
• Cord Length: about 4 Feet
• 1 Year Limited Warranty

 

As the spec says 3Amp / 350W, so its going to take 350W from your inverter, and thats going to take current from your batteries, which you need to measure to be exact, then you can work out the Ah of the batteries.

 

As the spec says 3Amp / 350W, so its going to take 350W from your inverter, and thats going to take current from your batteries, which you need to measure to be exact, then you can work out the Ah of the batteries.

Thanks Dodge, Can I do that measurement before I buy anything? Or is it best to just go with ballpark figures at this point so I can have some idea of what I need to get and how well this is going to work for me before I buy anything.?

 

I'll give you some sad facts first. To make a reliable system you will need to nearly double the total system capacity for the expected load using just the expected AC power requirements. For at least some part of the daily charging/discharge cycle you will usually need to both run the system and charge batteries at the same time so the solar power input requirement must exceed the load power by the amount needed to also maintain the daily battery drain power requirement during run/charge modes. You also need a battery power reserve for at least one day of low sun power and if you are using cheaper flooded lead-acid cells you need to keep the discharge cycles shallow (>50% state of charge) to increase battery cycle life.

 

I'll give you some sad facts first. To make a reliable system you will need to nearly double the total system capacity for the expected load using just the expected AC power requirements. For at least some part of the daily charging/discharge cycle you will usually need to both run the system and charge batteries at the same time so the solar power input requirement must exceed the load power by the amount needed to also maintain the daily battery drain power requirement during run/charge modes. You also need a battery power reserve for at least one day of low sun power and if you are using cheaper flooded lead-acid cells you need to keep the discharge cycles shallow (>50% state of charge) to increase battery cycle life.

Thanks nsaspook, after looking into this over the months I did find running even a 5000BTU meant a very expensive system, the reason I went with this size ac. I guess I won't know if those sad fact are too sad or not until I get some kind of price range, and to do that I have to have figures. As far as the reliable system, I may be able to make do then add on later, so it doesn't have to be an ideal system, but won't know until I can at least get a close estimate on paper. so I can decide how far I can go with it.

Are you two saying I can't calculate this even close until I actually buy? I was hoping to get an idea of full cost before I spent money, the main reason for posting.

 

At 100% efficiency, your inverter will need to draw 30 amps at 12 volts to produce 3 amps @120 volts. Depending on the capacity of your deep discharge batteries, you are looking at a run time of between 1 and 2 hours per battery.

 

At 100% efficiency, your inverter will need to draw 30 amps at 12 volts to produce 3 amps @120 volts. Depending on the capacity of your deep discharge batteries, you are looking at a run time of between 1 and 2 hours per battery.

OK, thanks, that estimate feels right/a good start. Do these batteries get heaver with a higher capacity, is there a norm there? Also when you say depending on capacity, you are talking from what capacity and up to to what capacity?.. so I can go look at exactly what we are talking here and get some prices.

Also, I'd guess it did but to be sure, did your calculation account for compressor off time (something I forgot to mention) since it will not be running full time? It's fine if it did or did not, at least I have a starting point, and no one knows just how often it will cycle on/off.

 

OK, thanks, that estimate feels right/a good start. Do these batteries get heaver with a higher capacity, is there a norm there? Also when you say depending on capacity, you are talking from what capacity and up to to what capacity?.. so I can go look at exactly what we are talking here and get some prices.

I would avoid a 12vdc based collection/storage system if starting from scratch. A good MPPT solar controller can convert a series string of solar panel voltage of >50vdc into a battery bank (two or more 12v batteries in series) voltage of 24vdc or more with a matching AC inverter. The higher source voltages makes wire gauge current and terminal requirements to reduce voltage lose from conductor resistance reasonable for the needed power ranges.

 

I would avoid a 12vdc based collection/storage system if starting from scratch. A good MPPT solar controller can convert a series string of solar panel voltage of >50vdc into a battery bank (two or more 12v batteries in series) voltage of 24vdc or more with a matching AC inverter. The higher source voltages makes wire gauge current and terminal requirements to reduce voltage lose from conductor resistance reasonable for the needed power ranges.

Thanks, that's certainly something to consider if I can find them for as good a price as the 12v, ah for ah, maybe even better? I'm thinking the 12v may be enough less expensive because so many are sold over 24v it may be the best way to go, but not positive. I think I've narrowed it down to these unless anyone knows a better deal....right to my door too.

Well, can't post the link here, so the River looks like the best bet at $169.00 per 100AH

 

Use the golf cart cg2 batteries, you can buy at Sam's club cheaper.
Those will deep discharge and last longer than anything else.

Your putting those batteries under a lot of stress. If you go with standard 12 v deep cycle, they are going to wear out sooner than the 6v golf cart batteries.
Example
https://www.samsclub.com/sams/durac...p-size-gc2/prod3590228.ip?xid=plp_product_1_1

 

Good reviews on this one, heats and cools. 2500btu.
https://www.amazon.com/Outdoor-House-Conditioner-Heater-Combo/dp/B00LU8Z9DO

This will cool better, same price, but tradeoff, it uses more power.
But you can do it with enough batteries.
http://www.air-n-water.com/product/soleus-ky-80b.htm#resp-tabs3

several commented that it was noisy.
https://www.amazon.com/KY-80-Portable-Conditioner-Dehumidifier-Control/dp/B003E8GG3U#customerReviews

 

Read up on what is a genuine deep cycle battery.
http://www.pbase.com/mainecruising/deep_cycle_battery

 

Good reviews on this one, heats and cools. 2500btu.
https://www.amazon.com/Outdoor-House-Conditioner-Heater-Combo/dp/B00LU8Z9DO

This will cool better, same price, but tradeoff, it uses more power.
But you can do it with enough batteries.
http://www.air-n-water.com/product/soleus-ky-80b.htm#resp-tabs3

several commented that it was noisy.
https://www.amazon.com/KY-80-Portable-Conditioner-Dehumidifier-Control/dp/B003E8GG3U#customerReviews

Thanks for all the links, those were just mentioned on another help site and I had alredy heard they were everything you say they are when it comes to being good for my application. Not sure how much a Sams card is these days but I may try to find some pricing on them on the net, and see if it's worth it all in all. How in the world do I tell how many AH's those are? The capacity numbers on some off these are done in CSS or something like that and it can't be converted to AH's so how can I tell if I'm getting an equivalent of 100AH or a 35AH battery or whatever I end up needing?

On the 2,500btu unit I briefly mentioned that one in the OP, so I did consider it. Neither of them will do the whole boat so I figure I'll go small as possible, save the power, and I'm also thinking the way these cycle on and off I may uses even less power than I'm thinking...but not counting on it by any means.

Is it possible to view Sams pricing without a card?

 

I found the pricing on the 6V and the cards are pretty cheap @ $45, here is the link, and can anyone thel me what those are in AH's?

https://www.samsclub.com/sams/searc...r_search-typeahead_golf-cart-batteries-6-voit

 

You dont want to throw money away on fake deep cycles, so you need to go with golf cart for the most AH for your cash,
Duracell Golf Car Battery - Group Size GC2

• $ 93 88

Specifications
20 amp hour rate:215
5 amp hour rate:157
6 amp hour rate:156
Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purposeeep Cycle
BCI Group Size:GC2
Contents:ONE EACH
Freight Class:65
Minutes at 25 amps:395
Minutes at 75 amps:105
Terminal TypeIN
Volts:6

 

Thanks for all the links, those were just mentioned on another help site and I had alredy heard they were everything you say they are when it comes to being good for my application. Not sure how much a Sams card is these days but I may try to find some pricing on them on the net, and see if it's worth it all in all. How in the world do I tell how many AH's those are? The capacity numbers on some off these are done in CSS or something like that and it can't be converted to AH's so how can I tell if I'm getting an equivalent of 100AH or a 35AH battery or whatever I end up needing?

On the 2,500btu unit I briefly mentioned that one in the OP, so I did consider it. Neither of them will do the whole boat so I figure I'll go small as possible, save the power, and I'm also thinking the way these cycle on and off I may uses even less power than I'm thinking...but not counting on it by any means.

Is it possible to view Sams pricing without a card?

I've used the COSTCO cg6 208AH batteries for a 12v solar storage bank. They are cheap (mine were $75 each with core), reliable but easy to murder if you don't charge (over or under) and water them correctly. I would use AGM batteries instead. When my current cg6 set is shot I'm going AGM.

 

You dont want to throw money away on fake deep cycles, so you need to go with golf cart for the most AH for your cash,
Duracell Golf Car Battery - Group Size GC2

• $ 93 88

Specifications
20 amp hour rate:215
5 amp hour rate:157
6 amp hour rate:156
Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purposeeep Cycle
BCI Group Size:GC2
Contents:ONE EACH
Freight Class:65
Minutes at 25 amps:395
Minutes at 75 amps:105
Terminal TypeIN
Volts:6

Yep,missed that but just came by to post it. Can you tell me roughly what that means, or what does that say the standard AH rating is, the standard I've been using up to now?

 

I've used the COSTCO cg6 208AH batteries for a 12v solar storage bank. They are cheap (mine were $75 each with core), reliable but easy to murder if you don't charge (over or under) and water them correctly. I would use AGM batteries instead. When my current cg6 set is shot I'm going AGM.

Wow, that's a very low price compared to what I was looking at. Unless I'm reading wrong, nearly twice the AH, for half the price of Amazons? correct? Have they lasted well on your system there, if taken care of properly?

What do you think of the Sam's 6v golf cart batteries?

 

Here are specs for AGM's . What does what I made bold there mean? Does it simply mean it;'s a 100 AH battery?

Specifications

• 1 amp hour rate: 103
• 100 amp hour rate: 220
• 20 amp hour rate: 190
• 3 amp hour rate: 145
• 5 amp hour rate: 163
• 6 amp hour rate: 167.8
• 8 amp hour rate: 173.7
• Battery Electrolyte Composition: Glass Mat
• Battery End Type: Top Post
• Battery Purpose: Starting Lighting Instrumentation
• BCI Group Size: GC2
• CCA at 0 degrees F: 680
• Freight Class: 65
• MCA at 32 degrees F: 900
• Minutes at 15 amps: 718
• Minutes at 25 amps: 409
• Minutes at 5 amps: 2304
• Minutes at 50 amps: 171
• Minutes at 75 amps: 94
• Minutes at 8 amps: 1409
• Reserve Capacity: 380
• Terminal Type: SAE
• Volts: 6

 

How about a small Honda 2000 generator??

What does 20 hr mean on a battery?
You may see “20HR” on your battery and wonder what does it mean. Simply said it means 20 Hour Rate. Usually SLA Batteries are rated at 20HR. ... Lets say a SLA battery is rated at 20Ah capacity at 20HR. This basically means that the battery can discharge 1 amp per hour over a 20 hour period.

20/20 =1 amps per hour for 20 hours
200/20 =10 amps per hour for 20 hours, after that, it has no useful power left.

Basically batteries suck at delivering lots of amps for a long period of time.
Then they can wear out fast, and they cost a lot of money.
My guess, they always will suck.

What is needed is to get away from batteries to something, anything else is better.