24v solar added to existing 12v system in motorhome

mikga45
mikga45 Registered Users Posts: 17
I should be back in Greenville in a few weeks to get a old 30 to 40 year old motorhome and I will be living off the grid, compost toilet, rain water and after 2 months or less no propane. food will with in 2 months be coming from fish and game I hunt. I will stock up on canned vegetable and vitamins, multi day and some camp fruits. I will be jobless and try to find some part time work along the way for gas for the rv and internet. I will camp mostly on wildlife management hunting grounds. At 55 and no longer able to do A/C work anymore I opt for a motorhome over living in a shelter and standing in line at a soup kitchen. Will look for a good dog to warn be early of any threats of the 2 or 4 leggit kind. I will try to stay on land that has a forrest and lakes to fish, I spent 8 years in iraq and Afghanistand, let someone else have the desert for a while.

The motor homes normally come with a few batterys and a 12 v system. If it comes with a 12v refridge it would be crazy not to use it.

I was thinking of 4-t105 trojan batteries wired in series for 24v and connected to 24v solar panels from 5 to 750 watts. All depends on what is left after I buy motorhome and used motorcycle "enduro"

If the system is already wired for 12v for the existing refrige, water pump and such would it be better to just stay with the less effiecent 12 v system? If I added a 24v solar to existing I would still have to have a way to charge th truck battery and run the fridge at 12v. How to connect the 2-diffrent systems together? I will be adding a small 4 to 6 cu' freezer 120 vac.

I have not seen much info on running 12v things off of 24v system. also I will need a 45 to 60 amp mppt charger and a 2 to 2500 watt pure sine inverter. If money is short I will have to go smaller on solar. Thanks.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar added to existing 12v system in motorhome

    Running 12 Volt devices from 24 Volts requires some extra equipment. Either a DC to DC converter, an MPPT controller to charge a 12 Volt battery from the 24 Volt, a battery charger plugged in to the 120 VAC running off 24 VDC, or an entirely separate system.

    This is one of the few instances where staying with 12 VDC may make more sense. If you don't have any larger power demands that justify the 24 Volt need you can scale back easily. RVer's get along fine on 12 Volts even with a less-than-minimal lifestyle.
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    If I stayed with the 12v I would no longer need the expensive mppt controller. Should I just use 2 battery banks and run them parralel for the t-105 batteries? Or would it make more sense to just get 2 of the higher out put trojans that are 350ah or more each? thanks

    What is alarming as well to me is the want ads and the amount of pit bulls people are getting rid of, many I would guess are running loose after being abandoned by their owners, not normally aggressive to man but very territorial and dangerous to other dogs. they dont bark much and would be a bad choice for me, i wanted a black mouth cur but might have to get a dog that can fend off a pitt bull attack, manythings to get.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar added to existing 12v system in motorhome
    mikga45 wrote: »
    If I stayed with the 12v I would no longer need the expensive mppt controller. Should I just use 2 battery banks and run them parralel for the t-105 batteries? Or would it make more sense to just get 2 of the higher out put trojans that are 350ah or more each? thanks

    Actually you probably would want the MPPT controller anyway as it means you could utilize less expensive per Watt GT style panels.

    You could use four of the T-105/GC2's as two parallel strings of two in series. This would be the least expensive battery base (the L16 series batteries cost more per Watt hour). So you'd have 440 Amp hours @ 12 Volts, and at 25% DOD roughly 1320 Watt hours.

    To charge that much you'd want 44 Amps @ 12 Volts peak current, or around a (44 * 12 / 0.77) 686 Watt array. There you see where the array will be large enough that buying the GT panels @ $1 per Watt & the MPPT controller works out to less money than 'standard' panels @ $2 per Watt with a cheaper PWM controller.
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    GT style panels? I will have to wait till I get the motor home, it will be very interesting to find away to ger 7- 100 watt panels on a class C motorhome. Who sells the panels that cheap? I need to find a mppt controller and a inverter that does not cost 700, I would like to get both for less than 500 dollars,I do need a inverter 2 to 2500 I will be using a electric skillet, convection oven for short periords of time, less that 10 mins a few times a day to cook with, I will have to do trial and error to fine ways to cook without propane, will probaly get a small wood stove for heat and vent out of roof and feed it with fresh air from outside.

    I know there will be manythings I will end up not being able to get, electri, water and heat and a good dog are important.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar added to existing 12v system in motorhome
    mikga45 wrote: »
    GT style panels?

    Panels meant for Grid Tie systems; they have Voltages that don't work well with battery systems & PWM controllers. Look at the chart here: http://www.solar-electric.com/hiposopa.html

    The lower Wattage panels (130/140 Watts) are around $2 per Watt and have a Vmp of 17-18 which is normal for 12 Volt systems. The higher Wattage panels (>200 Watts) are around $1 per Watt and have Vmp around 30 which is normal for GT systems but doesn't work well on battery systems unless you use an MPPT controller.
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    At 500 for a mppt 60 amp controller that is almost 4 times the price of a standard controller, the money you save on larger panels you would spend on shipping. I would love to have that, but don't have a 2,000 plus budget for solar. I will have to see what the motorhome and motorcycle costs and go from there. Cost wise and energy wise the mppt makes sense, If the funds are not there sometimes we have to put less efficient systems in even if we know they are a poor choice.Hanging out in the woods is far less desirable than sitting pool side with a beautiful lady with a bank account full and a new Mercedes in the drive way. :) This life time that was just not meant to me. ;) Thank you for the useful information, once I return to the states I will get started on this. I think I will opt for a 30-06 over a 338 win mag or 375 H&H. I will have a shotgun with slugs for the trailer. I might get to montana but not likly so Grizzly bear encounters are not likly. I will try to carry a 10 mm handgun on my side. in close hunting less than 100 yards the big mags tear the animals apart.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar added to existing 12v system in motorhome
    mikga45 wrote: »
    At 500 for a mppt 60 amp controller that is almost 4 times the price of a standard controller, the money you save on larger panels you would spend on shipping. I would love to have that but don't have a 2,000 plus budget for solar. I will have to see what the motorhome and motorcycle costs and go from there.

    :confused:Shipping an MPPT controller doesn't cost that much.

    Here's what a ~700 Watt array & controller would look like each way (PWM/MPPT);

    Five 140 Watt panels http://www.solar-electric.com/kyocera-kd140gx-lfbs-140-watt-polycrystalline-solar-panel.html @ $265 each = $1320
    TriStar 45 Amp PWM controller http://www.solar-electric.com/trts12vochco.html $140
    Total: $1460

    Three 240 Watt panels http://www.solar-electric.com/trina-solar-multicrystalline-240-watt-tsm-240pa05.html @ $238 each = $714
    TriStar 45 Amp MPPT controller http://www.solar-electric.com/motr45ampmps.html $405
    Total: $1119

    Difference: MPPT system $341 less. You can do a lot with $341.

    The electric cooking equipment is not a great idea off-grid because of the power demands it makes. Especially on 12 Volts. A 1500 Watt element will pull about 140 Amps from the batteries at that Voltage. This requires large wire and careful attention to connections to reduce resistance to a minimum. My suggestion would be "think propane".

    But at this point nothing is set in concrete as you don't know what resources you'll have to work with.
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    for cooking I would try to find low watt devices under 800 watt and for periors as short as possible, just a thought nothing in stone yet.Depends on the cost of propane and my ability to get a little work here and there. Battery I should be able to get locally and save on shipping they will have a core charge tho, i have no batteries here in the Philippines. :0 how much to ship the larger panels to South Carolina?
    seems like you said you needed 44 amps to charge, would the 60 amp mppt be the better choice. ? How long from when I place my order till it arrives?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 24v solar added to existing 12v system in motorhome

    I can't tell you about shipping costs as I don't work for NAWS. Not even in the same country.

    A 2kW inverter will be just under $1000 for an inexpensive but not low-quality one like Samlex/Cotek.
    http://www.solar-electric.com/sa2wa12vosiw.html (24 Volt is the same.)

    And if we go back to the 24 Volt idea the current drops to 22 Amps and you could use a MidNite Kid for that @ $285 http://www.solar-electric.com/midnite-solar-kid-controller-accessories.html $1240 less than the TriStar.

    Just giving you some equipment and pricing options to think about. You may be doing some bargain hunting.
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    With these costs, we are at 3000 plus, Way out of my budget. I will have to downsize a lot. I will know more where stand after I get a motor home. Might be cheaper to set up 2 non mppt systems, one for charging truck, refridge and water pump and one for everything else.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 24v solar added to existing 12v system in motorhome

    Yep--Do a bunch of different "paper designs first"... And cost them out (including shipping and insurance to your front door).

    Internet pricing can be nice, for for things like solar panels, a local solar installer that purchases panels by the pallets can be very cost effective too (it is not unusual for the price of a single panel to equal the cost of shipping).

    Talk with NAWS/other retailers and ask for their recommendations (after you first pencil out a couple of systems) and get their recommendations--Most all of us here are volunteers/end users and cannot make "firm" business/cost related recommendations--We are simply not in that business.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    Thanks for your help. Once I get the motor home i will be able to see existing battery banks and what size the refridge is and its wattage use for start up and run.
  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: 24v solar added to existing 12v system in motorhome
    mikga45 wrote: »
    Thanks for your help. Once I get the motor home i will be able to see existing battery banks and what size the refridge is and its wattage use for start up and run.

    Your expectations and budget are a fair bit out of kilter. Something is gona have to give mate. You cant have fridge, and cooking at less than $5K, indeed 8K is probably more realistic. For $2K you could do lighting, waterpump, laptop and tv. Roof space will be also be a limiting factor.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • mikga45
    mikga45 Registered Users Posts: 17
    Re: 24v solar added to existing 12v system in motorhome

    Yea I am starting to realize it's a lot more expensive than Imagine, good thing I have went without a lot This last few years and cooked mostly with fire and used rain water, Have lived the life style of third world country in the Philippines. Will do what I can, less is ok. After ten years America will be a strange place for me after living in the middle east for 8 years and the philippines for 2. I did go back for 2 months for traing and paper work and such for Afghanistand. 2 months in 10 year, will be a diffrent place for me.

    I use to make the impossible happen in iraq all the time, no material and than when we got it the wrong stuff. the army had heat pump condensor with shraight cool evaporators, I rigged it so they would have heat for 2 months. no mad camper has a little 1.7 cu' fridge that is 12 v i beleive and he is running it on 1-100 watt panel, it works and he might add another 100 watt panel later. it could be a little larger than that. when a refridgerator cools the box down even a large refridge draws less that 1 amp. cook7ng will be a issue the small stuff at less that 800 watts does not cook eficently. heat i will try to get a wood stove. propane in the philippines is arround 25 us dollars for a 20 lb bottle we can not afford that. we bought propane a week ago for the first time in almost a year. we received a deposit for the house we are selling. You could buy a used ford explorer for less that we are selling the house for and I will get a small amount from that only. It is what it is as they say.

    fridge problem sorta out, incase the motor home I buy does not have a good fridge. small but good enough, now to the next issue. https://www.youtube.com/watch?v=yjsQZ4q4tjE