Home » Public Forums » GMCnet » Ductless minisplit and batteries instead of genset.
| Ductless minisplit and batteries instead of genset. [message #368832] |
Sat, 19 February 2022 07:36  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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I'm thinking about it. The math keeps getting better.
There are a bunch of 120V ductless minisplit heat pumps that will fit in the generator compartment (mine is currently empty)
The vandweller kids are doing the math in youtube videos - the 12,000 btu ductless pulls 700 watts for initial cool down and 200-300 watts to maintain.
THat comes to around 700amps worth or battery (discharged to 50%) and half that if i go with lithium. (I currently have 500 amps worth of flooded batteries to use up)
Who else has gone down this road?
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Ductless minisplit and batteries instead of genset. [message #368833 is a reply to message #368832] |
Sat, 19 February 2022 08:31  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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For day time use you will be at full 12,000 for 8 hours minimum. And may be up around 80F inside with sun load. For reference 17,500 plus a 15,000 roof top are needed in the deep south most find. 1 unit does fine at night.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Ductless minisplit and batteries instead of genset. [message #368835 is a reply to message #368833] |
Sat, 19 February 2022 09:09 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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JohnL455 wrote on Sat, 19 February 2022 08:31For day time use you will be at full 12,000 for 8 hours minimum. And may be up around 80F inside with sun load. For reference 17,500 plus a 15,000 roof top are needed in the deep south most find. 1 unit does fine at night.
Yup. I live in NC. But we avoid subjecting ourselves to too much Southern heat- mountains or go north. Also, we don't spend much time inside the camper unless we're moving, and then we could add the dash air.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| [GMCnet] Re: Ductless minisplit and batteries instead of genset. [message #368836 is a reply to message #368832] |
Sat, 19 February 2022 10:37 |
Marsh Wilkes
Messages: 155
Registered: January 2004
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Hi Dave,
I haven't spoken of it in years and have forgotten many of the details, but
I went all the way
down that road, design wise, about 15 years ago, it's a very interesting
concept! Although there
have been minor improvements in AC efficiency, they have a very optimistic
way of rating minisplits.
That's not the point however, there are several major considerations for
such a system, namely load,
load, load, battery capacity and battery charging. There is a reason 2 roof
units will barely cool a GMC
in the sun in the South East. Not to be a naysayer, but the system you have
mentioned would probably
offer reasonable battery capacity, cooling a typical GMC on a 79 degreed day
in full shade. If you are well
versed in psychrometrics you can do the calculations yourself. The system I
designed took several MAJOR
DESIGN ELEMENTS to make it workable. It took major upgrades in thermal
insulation for which there is not room
in a conventional GMC (and still have headroom), the design required moving
the floor below the aluminum framing
to gain space and flooring with aluminum to gain space for floor insulation.
That much of the project I completed before
running out of time and money. The design also added foam roof insulation on
the outside, again for headroom, and also
very special window treatment! The other MAJOR element was battery charging,
for that I came up with an AC Delco 24 volt
bus alternator capable of 9 KW output! Even that was complex in that it
required a variable speed drive to both prevent over speeding
the alternator at high engine speed and being able to charge at idle. I
actually found a company that built such a drive. The system would
have provided full Air Conditioning in any environment and other electrical
needs, with a maximum of two 30 minute coach engine idling
times a day!
It wouldn't be terribly difficult to try out your idea and it would be
interesting to see the results. I don't have any more time right now, but if
you are interested in discussing it, private email me and I will give you my
cell #, my email address can be found under properties of this message.
Marsh (rarely post anymore) Wilkes
Perry Florida
-----Original Message-----
From: dave silva
Sent: Saturday, February 19, 2022 8:36 AM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Ductless minisplit and batteries instead of genset.
I'm thinking about it. The math keeps getting better.
There are a bunch of 120V ductless minisplit heat pumps that will fit in the
generator compartment (mine is currently empty)
The vandweller kids are doing the math in youtube videos - the 12,000 btu
ductless pulls 700 watts for initial cool down and 200-300 watts to
maintain.
THat comes to around 700amps worth or battery (discharged to 50%) and half
that if i go with lithium. (I currently have 500 amps worth of flooded
batteries to use up)
Who else has gone down this road?
--
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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GMCnet mailing list
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| Re: [GMCnet] Re: Ductless minisplit and batteries instead of genset. [message #368842 is a reply to message #368836] |
Sat, 19 February 2022 15:06 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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I'm not looking for a major R&D project but....
A 13,000 BTU roof air cools the coach pretty when parked. So a 12,000 btu minisplit should be close (and this is a 23-footer)
I suppose i'd keep the roof air until i was sure. And we'd also have the dash air.
The big change in the last few years is the efficiency (300-800 watts) and the falling price batteries. -now comparable to flooded.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| [GMCnet] Re: Ductless minisplit and batteries instead of genset. [message #368843 is a reply to message #368842] |
Sat, 19 February 2022 15:54 |
johnd01
Messages: 354
Registered: July 2017
Location: Sacrameot
Karma: -1
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I have looked into this as well. Adding solar panels to shade the coach
would help as well as provide generation. I figured it would be possible to
add 8 72 cell PV panels with up to 400 DCW nameplate rating. 8x400 = 3200
watts DC. you might get 2000 watts in full sun but would probably reduce
heat load by almost as much as 1000 watts would cool. I do not see the
system working with lead acid batteries. There are at least 2 RVs on
youtube that have gone all eclectic. No propane or genset with
residential refrigerators. Both sites used a soft start for the AC unit.
On Sat, Feb 19, 2022 at 1:07 PM dave silva wrote:
> I'm not looking for a major R&D project but....
>
> A 13,000 BTU roof air cools the coach pretty when parked. So a 12,000
> btu minisplit should be close (and this is a 23-footer)
>
> I suppose i'd keep the roof air until i was sure. And we'd also have the
> dash air.
>
> The big change in the last few years is the efficiency (300-800 watts) and
> the falling price batteries. -now comparable to flooded.
> --
> Dave & Ellen Silva
> Hertford, NC
>
> 76 Birchaven, 1-ton and other stuff
>
> Currently planning the Great american Road Trip Summer 2021
>
> It's gonna take a lot of Adderall to get this thing right.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
--
*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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| [GMCnet] Re: Ductless minisplit and batteries instead of genset. [message #368844 is a reply to message #368842] |
Sat, 19 February 2022 15:49 |
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Several have done this successfully by removing everything on the roof and
covering it with solar panels. This gives about 2400 watts of potential
solar power to run a 12000 btu, 110v mini split that resides in place of
the propane tank.
Owners report that the benefit of a shaded roof helps immensely and is
sufficient for comfort year round in southern climates such as Florida and
central Texas. Other than electric heat is required on occasion seasonally.
bdub
On Sat, Feb 19, 2022 at 3:07 PM dave silva wrote:
> I'm not looking for a major R&D project but....
>
> A 13,000 BTU roof air cools the coach pretty when parked. So a 12,000
> btu minisplit should be close (and this is a 23-footer)
>
> I suppose i'd keep the roof air until i was sure. And we'd also have the
> dash air.
>
> The big change in the last few years is the efficiency (300-800 watts) and
> the falling price batteries. -now comparable to flooded.
> --
> Dave & Ellen Silva
> Hertford, NC
>
> 76 Birchaven, 1-ton and other stuff
>
> Currently planning the Great american Road Trip Summer 2021
>
> It's gonna take a lot of Adderall to get this thing right.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
_______________________________________________
GMCnet mailing list
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bdub
bdub.net
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| [GMCnet] Re: Ductless minisplit and batteries instead of genset. [message #368846 is a reply to message #368845] |
Sat, 19 February 2022 19:28 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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I’d love to see pictures or a write up of solar on our coaches. I have been considering buying a flexible panel and adhering it to the roof. 1 or 2 to keep the batteries topped up. Then in time maybe a 200 ah lithium battery to keep the lights on, but that means rewiring and an alternator gizmatchy.
I’d also considered a rigid panel on the storage pod as I’ve seen here.
Larry Davick
1976 Palm Beach
Fremont California
> On Feb 19, 2022, at 4:16 PM, Matt Colie wrote:
>
> Billy Massey wrote on Sat, 19 February 2022 16:49
>> Several have done this successfully by removing everything on the roof and covering it with solar panels. This gives about 2400 watts of
>> potential solar power to run a 12000 btu, 110v mini split that resides in place of the propane tank.
>> Owners report that the benefit of a shaded roof helps immensely and is sufficient for comfort year round in southern climates such as Florida and
>> central Texas. Other than electric heat is required on occasion seasonally.
>>
>> bdub
>
> This has a better chance than many might suspect. The panels are isolated from and shade the roof at the same time. It would seem to be very similar
> in function to the "Tropical Roof" used on some Landrovers in hot - sunny locations.
>
> If you have not seen one, this is a second roof separated from the first by an air gap of an inch or so. I was told by the owner that it makes an
> amazing difference when shade is needed.
>
> Matt
> --
> Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Near DTW - Twixt A2 and Detroit
> _______________________________________________
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Ductless minisplit and batteries instead of genset. [message #368851 is a reply to message #368832] |
Sun, 20 February 2022 07:11 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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There's three parts to this project:
- converting hvac to minisplit
- running it on batteries
- charging those batteries.
It's all about how the coach gets used. My plan is for to be a lot of traveling and not so much camping in the woods or extended boondocking.
SO if the load is 300-800 watts it can be maintained and charged from the alternator.
It can also be charged/run from a cheap 1200 watt generator which only weighs 50lb and can be stashed in the roof box.
With all of that worked out i can convert the batteries to lithium and add solar panels as needed.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Ductless minisplit and batteries instead of genset. [message #368856 is a reply to message #368851] |
Sun, 20 February 2022 09:54 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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David,
There are some that are making that system work. But from what I see, it is a hobby- something that you do because you want to and like to tinker and learn. The ones I know of are for sure spending massive amounts of time and money.
LifePo4 batteries are dropping in price, but still to get to the stage you are talking from what I have seen
Others will take thousands of $$$. And those that do go that route it is a constantly evolving tech and process. I know a few that have a bench of $1000’s of obsolete inverters, panels, charge
Controllers, ect…. As
The expand,
Tweak and perfect their systems.
But look for what Riley Gibson of florida has done, and there are
Others. A few mounted on bumper and use smaller generator too.
There are pro’s and con’s…
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Ductless minisplit and batteries instead of genset. [message #368857 is a reply to message #368851] |
Sun, 20 February 2022 10:00 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Your wattage
Load seems low. Even for a mini-split. The main thing is 120v mini-splits are
More limited to the 240v you normally see.
Long term also is concerning for vibration and road travel, but one will never be able to really know if the mini-splits can handle
Roads over time.
Charging with an alternator that gets into those wattages are always concerning to me. Our coaches rely on that motor to get us around and if an alternator or belts fail. You have to have a solution to keep going. Currently belts and alternators in our coach are readily available and easy to maintain and inexpensive. I remember my friend’s bus alternator going out and costing him $500.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Ductless minisplit and batteries instead of genset. [message #368871 is a reply to message #368857] |
Mon, 21 February 2022 07:33 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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lqqkatjon wrote on Sun, 20 February 2022 10:00
Your wattage
Load seems low. Even for a mini-split. The main thing is 120v mini-splits are
More limited to the 240v you normally see.
Long term also is concerning for vibration and road travel, but one will never be able to really know if the mini-splits can handle
Roads over time.
Charging with an alternator that gets into those wattages are always concerning to me. Our coaches rely on that motor to get us around and if an alternator or belts fail. You have to have a solution to keep going. Currently belts and alternators in our coach are readily available and easy to maintain and inexpensive. I remember my friend’s bus alternator going out and costing him $500.
Pretty confident in the wattage numbers. The three ton system in my house only drew 7 amps running (1500 watts 240VAC)
I am curious about alternator load. Maybe run the system off the batteries and have the alternator provide steady charging amps in the 40-50 amp range?
The load on the belt should not be an issue, simalar to the load on the AC compressor belt
Losing a belt should be a non-problem if i have a 400amp battery bank and a switch and who pays someone to replace a fan belt?
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Ductless minisplit and batteries instead of genset. [message #368874 is a reply to message #368871] |
Mon, 21 February 2022 08:12 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
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I guess I was assuming needing to go to a serpentine belt at 250 amps alternator.
I know many struggle with a 100 amp and a stock belt. Usually 100 amp folks end up jumping and going to a double belt pully.
Riley Gibson has a nice mini-split setup. But he has massive money and lots of time installing everything.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Ductless minisplit and batteries instead of genset. [message #368881 is a reply to message #368874] |
Mon, 21 February 2022 14:43 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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lqqkatjon wrote on Mon, 21 February 2022 08:12I guess I was assuming needing to go to a serpentine belt at 250 amps alternator.
I know many struggle with a 100 amp and a stock belt. Usually 100 amp folks end up jumping and going to a double belt pully.
Riley Gibson has a nice mini-split setup. But he has massive money and lots of time installing everything.
100 amp alternator -- 1200 watts. The minisplit needs a peak of 7-800 and a continuous 200-300. Rather than put surge loads on the alternator i run it through a 30 amp charge controller and run the HVAC off the batteries. i think that should keep from freaking out the alternator.
The big unkwnown is how the outdoor unit will tolerate the vibration.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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