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Author Topic: Inverters 12 or 24 volt?  (Read 4619 times)
scanzel
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« on: December 18, 2007, 12:10:40 PM »

I'm still trying to make a decision on a 12 or 24 volt inverter. I presently have 8, 100 ah AGM batteries that are brand new. Got them for free. My coach will have 12 volt lighting and a 12v Proheat with some 12v hot water toe kick heaters. My appliances will be a microwave, house type refrig 18 cf, stove has spark ignition and the other basic 120 ac appliances coffee maker etc. My biggest concern is when dry camping to have enough power and not to run the generator for long periods, 9kw Kohler. I am also seriously looking at 4, 85 watt solar panels coupled to a charge controller. Air will be 2, Carrier low profile roof tops. If I go to either 12 or 24 volt inverter to convert to 120ac where do I get my 12 volts from for 12V devices. Do I need separate battery bank or do you tap of of the inverter bank. Still confused here. What are the rest of you using and what is your set up. I realize that generator is need for air but if air is not need I still need to run the rest etc.
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Steve Canzellarini
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« Reply #1 on: December 18, 2007, 12:25:30 PM »

Hi,
The only real issue between 12 and 24 volt in your case is the wire size you'd use between your batteries and your inverter- it'd have to be quite a bit heavier for a 12 volt inverter than for a 24, but that's about the only practical difference these days.  Since the rest of your coach will be 12 volts, I can't imagine why, for the sake of some lighter gauge wire between the battery and inverter, you'd even consider complicating things horribly by going to a 12/24 volt system.  There's no good reason!  You've pretty much already answered your question with your questions... if you go 24 volts then getting 12 for everything else is a hassle involving more battery banks, more alternators, more chargers, etc.  Keep it all 12 and you'll keep things simple, which in a bus, is a good thing!  All you'd basically need is a separate battery to start your engine, and your 12 volt "house" bank of AGM's for the inverter and everything else.  Mostly people are forced into 12/24 volt systems when their coach came to them as a 24 volt system.  Then the choice is to either do the complicated dual system or rewire the coach for 12 only, which is difficult at best.  But if going in to it you already have a 12 volt system... there you are!
Cheers
« Last Edit: December 18, 2007, 12:29:34 PM by boogiethecat » Logged

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« Reply #2 on: December 18, 2007, 12:50:11 PM »

   Our MC-8 is 24 volt. When we were ready to purchase na inverter, we went with 12 volts.  We have alot of 12 volt "stuff" (water pumps, ProHeat, lights, radios, cellphone chargers, etc) If we had went with a 24 volt inverter, we would have had to purchase an equalizer to draw 12 volts and keep batteries equal. Equalizer= more $$$ and one more thing to possibly fail.
    If you plan to run a roof air off the inverter while underway, you will probably have to go to a 24 volt inverter to get one with enough output for the AC.  Just our way, YMMV  Jack
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« Reply #3 on: December 18, 2007, 01:17:17 PM »

I went with a 24 volt inverter for a couple of reasons.  One, the inverter battery bank can be used to start the bus.  The solenoid that ties the battery banks together for charging also ties them together for starting, if needed.  The other is that my bus has a 250 or so amp 24 volt alternator.  Keeping everything 24 volt means my house batteries charge off that big alternator, and my inverter will run off the alternator - with batteries connected, of course - while driving.  I pull 12 volts off the 'low' batter of the house bank and have a 100 amp Vanner equalizer to keep the batteries balanced.  These can be very expensive, but I found mine on eBay for around $150 new.  They're often available used for reasonable price.  I balanced that against adding another alternator (12 volt) for the house bank.  To me, the simplest, most streamlined system was 24 volts for the big items (alternator and inverter) and the smaller 12 volt loads being taken care of by the equalizer.

David
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prevost82
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« Reply #4 on: December 18, 2007, 02:55:13 PM »

I rewired the whole bus to 12v and install a second 150 amp alt for the 1200 AH house batteries, the existing 100 amp alt for the coach. I have 2-trace 2412 inverters (one for each leg) going to a Blue Sea 8086 Distribution Panel. It's a 50 amp service
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Chaz
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« Reply #5 on: December 18, 2007, 02:59:44 PM »

WOW, if you ever come across another Vanner equalizer, or even another brand that is good, for that kind of money Dave, keep your old buddy Chaz   Grin  in mind!!!! I need to get 12v off my 24v system.
  I was talking to Jerry L. and he definitely said that is the way to go. But for the price of a new one, I'll go with an inverter/converter whatever. They are mighty proud of those equalizers!!!
  I also understand that 24v is the way to go, but until I get 12v from somewhere, I'm not liking it much.  Undecided
   Chaz
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« Reply #6 on: December 18, 2007, 04:16:13 PM »

There is no right or best way to do this. Only the best way for you. After talking with many people I went with the 24V system. I use a selector switch to crosstie the house and bus battery's together. This allows me to use my Trace DR3624 to run the roof air as I travel. Also if the bus battery's are low I can start with the house battery's.
 The price of the Vanner equalizer is a consideration, but that is how I get my 12 volts. It seemed like the right thing to do at the time. Still does for that matter.
 I also use some 24 volt lighting in the bus, if it is home type with a transformer just throw the transformer out!! Some things are available in 24 volt and appear to be of better quality than the 12V. I have a 24 volt water pump and 24V macerator pump. Rope light is also available in 24 volt. I'm sure there are other items that are available in 24V.
 Check all the options and take the route that makes most sense to you!!
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« Reply #7 on: December 18, 2007, 07:08:44 PM »

Glad to hear there are several 24v options! But my stereo is 12v.  Undecided  (along with fans, lights, pump, etc. that I already have.) Guess I'll have to just watch for awhile and see if I need to cut my losses.
 Thanx,
    Chaz
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« Reply #8 on: December 18, 2007, 07:35:18 PM »

My coach system is 24v, but the house system is 12v.  Is there anyway to run the AC of the engine though a 12v inverter.  Is having a separate 24v inverter dedicated to the AC through the coach batteries over-complicating things?
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captain ron
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« Reply #9 on: December 18, 2007, 08:09:43 PM »

12 volt is easier to find stuff for when in a pinch, most 24 volt stuff has to be ordered. I eventually want to convert everything over to 12 volt. Every thing is cheaper too. Also 24 volt is a little more work to set up as far as battery banks go as you will have to group batteries together in 2s if your using 12 volt batteries or 4s if using 6 volt. Also look at the cost of batteries and the amount of cable needed to hook up your bank. But as stated there is no right or wrong way just the best way for you and your needs.
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lyndon
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« Reply #10 on: December 18, 2007, 09:03:33 PM »

We are looking at the same issues regarding 12 or 24, too, and currently leaning toward 24 V. for several of the reasons mentioned. I did not think getting 12 from 24 would be much of an problem, though, but I see some food for thought in this thread.

My question is, why not use one or more DC to DC converters for 12 V. gadgets? Wouldn't that be much cheaper than an equalizer? Are there efficiency issues with converters?

Don
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Don
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« Reply #11 on: December 19, 2007, 05:17:13 AM »

My coach system is 24v, but the house system is 12v.  Is there anyway to run the AC of the engine though a 12v inverter.  Is having a separate 24v inverter dedicated to the AC through the coach batteries over-complicating things?

   There a couple problems with running an AC through a 12 volt inverter. One is that the largest 12 volt inverter I have seen is 2500 watt (2500 watt divided by 12 volts equals 208.3 amps). This means your alternator has to be putting out at least 208.3 amps all the time. the other factor is that I was told 2500 watt is marginal for running an AC.
   The 24 volt inverters are usually 3600 or 4000 watts (30 or 33 amps @ 120 volts)  Jack
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« Reply #12 on: December 19, 2007, 05:59:36 AM »

Jack is on the right track here, but his numbers might be a bit off. The alternator would only have to put out that kind of power if the A/C actually required 2500 watts continuous (which is 20 amps). I think most rooftop A/Cs will typically require under 13 amps of 120v, so your alternator would need to put out about 130 amps continuous. A little less than Jack's numbers, but still significant for a 12v setup, regardless.

If you have a 24v bus, with a large 24v alternator, I highly recommend you use that to your advantage, and insalll a 24v house system with 24v inverter and crossover relay for charging house batteries off the bus alternator. 12v can be had from the system for as little as $10 with a 24v-12v converter off ebay. More $$ if you go fancier with an equalizer, but the choice is up to you. Personally, I use a converter for my 12v needs.

craig
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« Reply #13 on: December 19, 2007, 06:12:17 AM »

You are right the 12V items are more available. The 24V items I use that are critical are the water pump and macerator pump. The rope light has to be ordered but 24V bulbs are widely available.  I keep a spare of each pump in the bus, some people have a spare plumbed right into their systems!! When I replace one (very seldom, the 24V last a long time) I start watching Ebay for a replacement. I use the Parmax pump with quick disconnect. I can usually get one for $50/60.
 Also the 12V and 24V fuse blocks are very close to each other and I left a loop of wire, so in a worse case scenario I could  change the wire from the 24 to 12V block. No big deal.
 When I looked into this the general consensus was the equalizer was a better option than the converters. So not being an electrician or electrical engineer I just followed the herd. Gumpy is a smart guy, if he would have been posting back then I would probobly have a converter!
 Another advantage to this is with a 24V house system crosstied to the bus system, when I get someplace the house batteries are fully charged.
« Last Edit: December 19, 2007, 06:17:29 AM by jjrbus » Logged

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captain ron
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« Reply #14 on: December 19, 2007, 07:00:52 AM »

   There a couple problems with running an AC through a 12 volt inverter. One is that the largest 12 volt inverter I have seen is 2500 watt (2500 watt divided by 12 volts equals 208.3 amps). This means your alternator has to be putting out at least 208.3 amps all the time. the other factor is that I was told 2500 watt is marginal for running an AC.
   The 24 volt inverters are usually 3600 or 4000 watts (30 or 33 amps @ 120 volts)  Jack

I have a 12 volt inverter that is 5000 watts it's not one of those fancy expensive ones like most of you use but it's been great for me for the past 4 years. I as'so now have a 12 volt alt. mounted ready for use.
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