Complex power distribution and management.

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turboICE

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Jun 15, 2005
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Well, I didn't think initially that this would be a complex topic but based on calling product manufacturers it seems either they don't want to talk about it or they don't want to document how this could be done.

I have an enclosed car hauler that I use for transporting a race car and for living space while paddocked.

Shoreline power is not always assured at all tracks and I don't have enough space for a generator.

I need a power distribution, converter, inverter set up that will work together to provide me with my 12vdc and 120vac needs whether I am using a shoreline or batteries that also will not overcharge my batteries.

My accessories are:
12vdc lamps
12vdc plugs for laptop usage and cell phone recharging
120vac flourescents inside
120vac 250w lights outside (2)
120vac refigerator (small shop type)
120vac Carrier AirV HC HP (13A,1,400W max)
Not sure yet if entertainment will be via 12vdc or 120vac or both
May or may not want a 120vac line fed arc welder

My assumption is that I should be able to use shoreline or battery power to run everything except the Carrier and welder.? My hope is that I can at least run the Carrier at low cool settings on the battery.

The components I have been looking at are:
Parallax Power Supply 500 Series Power Center for AC/DC distribution and converter
Parallax Power Supply Automatic Transfer Switch for switching between shoreline and inverter power (shoreline connected to generator input, inverter to shoreline input to give priority to the shoreline)
Tripp Lite PowerVerter RV Inverter/Charger (2,000W continuous)

This is the closest thing I have found that will help me identify a potential means to get there: http://bellsouthpwp.net/j/u/jutod/Inverter%20Page/inverter.htm

However, this leaves some unanswered questions.
I really want to have a single bank of four batteries.
I don't want to overcharge the batteries and don't know if I should use the inverter's or converter's charger.
I don't want the 12vdc distribution to go through the inverter and then back through the converter for 12vdc power.
At some point solar panels will be added as well.

Basically in the end I want to run as much as possible (except the welder) from either a shoreline or a 4 battery bank.

I am interested in all feedback, comments and suggestions.  And I will not be offended by "search newb" posts if they are accompanied by the link or search terms used as I was not able to locate an on topic post to answer my questions when I searched the forum.

Ed.
 

Karl

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Hi Ed,

Welcome to the RV Forum. We're more than happy to answer any questions you may have, and being a newbie is something we've all been at one time or another. Heck, sometimes we even revert (or so it seems). ;D

Firstly, being involved in racing myself as an official, tell me something about what type racing you do. I work summers at Road America; both for SCCA and for the track.

I'll try to answer some of your questions, and others can and will chime in with their own answers.

Shoreline power is not always assured at all tracks and I don't have enough space for a generator.

There are some generators made by Honda and others that are quite small and lightweight. You say you have space for a bank of batteries; why not for a small genset?

I really want to have a single bank of four batteries.

You can have as many or as few as you want, depending on your needs, weight limits, space, and charging capability.


I don't want to overcharge the batteries and don't know if I should use the inverter's or converter's charger.

An inverter by itself takes 12V and changes it to 120VAC. It doesn't charge batteries. If it did, you would have invented free power!! :D It sounds like the unit you mention is a combination unit that acts as an inverter when running on batteries and as a converter when operating on shore power, and thus will charge your batteries.? You can run your a/c off the inverter, but not for very long. The number of batteries and their AH capacity will determine just how long. Keep in mind that deep cycle batteries are not meant to be discharged below 50%, or their life will be shortened dramatically. I once had a wire welder that ran off a 15A circuit just fine, so you should be able to do that also. The problem you may run into is that a welder is a highly inductive device and can throw some nasty voltage spikes on the line - not good for most electronic devices. Also, there are 3-stage charge controllers that will prevent overcharging.

I don't want the 12vdc distribution to go through the inverter and then back through the converter for 12vdc power.

Don't have to. Wire the 12V devices to the batteries (with fuses, of course) and your all set. RV's have a separate 12V and 120V distribution system; you should too. Your main concern is switching between shore power and the inverter for the 120V appliances, and that should be handled by the transfer switch.

Good Luck! Now I'll turn it over to the experts ;D
 

John From Detroit

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Davison Michigan
If you wish to run the air conditioner, and possibly the arc-welder, off the batteries

1: You are going to need one BIG inverter, Tripplite makes some nice big ones

2: you are going to need some BIG batteries.  One thing you might consider is this

See if there is a Battery Rebuilder in the area (NOte: There is a reason for this) who rebulids FORK LIFT batteries

Thiese are a bit of overkill for a RV.. but they do have the OOMPH to power most welders

NOTE: you can weld at 12vdc too, not recommended by me, but possible.  and some of those fork lift batteries have ratings on the order of thousands of amp hours

I've run a multi-station radio instalation all weekend and did not use but about 10%, and that was a small one
 

turboICE

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Jun 15, 2005
Posts
10
Thank you for the responses.

Karl - I road race an ITA/PS2/ST5 prepared 240SX.  You probably know the person I bought it from down in GA - Geoff.

Using a generator adds three new problems - their cost, the space for fuel tank and people complaining about them in tight paddock space. I can locate batteries under the trailer and recharge them from solar panels later.  The solar panels will make it more expensive than the generator but the good thing is exactly when the electrical demand is greatest is when they will get the most power - sunny hot days.

I have two charging options from the items I am looking at - the batteries can be charged by the converter or inverter since they both have charging capabilities when they have shoreline power. I just need to find a way to make sure which ever I use doesn't overcharge the batteries. The AC on its lowest settings shouldn't be much more than a microwave on its highest - I just need the Ah capacity.  Welding in the paddock will be the least desirable activity in only an extreme circumstance - but the ability would be nice.

Most setups don't actually use the batteries for 12vdc when they are connected to a shoreline.  The converter generally supplies the 12vdc in that situation while charging the batteries.  The issue I am facing is the power center not knowing that its AC source is the inverter rather than a land line.  Basically I would want the converter to disable when I am on inverter AC instead of a shoreline and run 12vdc off the batteries.  Otherwise the converter would use the inverters supply to run 12vdc and also try and recharge the battery - that would be pretty much a downward spiral.

John the inverters I have been looking at are fairly large the tripplite that I like so far is 2000w continuous and 4000w surge and also will charge the batteries when connected to AC (though I don't know if I am going to use the converter or inverter to charge).

Thank you for the idea on fork lift batteries.  I do need to look into the best Ah/weight performance I can get.
 

Karl

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Ed,

ITA, huh?  240Z? you must be an expert on rust repair ;D ;D  Heard about the change of the Nationals to Brainerd? ??? Just kidding!!!

The Honda units are so quiet you can stand next to them and carry on a normal conversation and have self-contained gas tanks. Solar is certainly an alternative, but not for instantaneous power requirements. Wally (one of our Forum members) is an expert in this area and can advise accordingly, but I think your needs, "I need power and I need it now", will dictate a generator (perhaps in addition to solar).

Good inverters come with an automatic switchover to shore power when available, and will switch back to batteries when it's not.  Take the Surge ratings with a grain of salt. Usually they will only handle the surge current for 10 or 15 seconds - MAX.  A good inverter will also have battery charging capability, so the converter is not necessary.

With all due respect to John, I would recommend using standard Trojan T-105's or T-120's. They are available everywhere and if you have a problem with one, you won't have to pay an arm and a leg to, as Elvis said: "Return to Sender" ;D

 

turboICE

Member
Joined
Jun 15, 2005
Posts
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Nah 12 valve 240SX - still more than enough repair involved given that it has been in service since Bob Stretch ran it in 1997.  Always amazing how little time spent on racing is actually time spent racing.

I was looking at the run times for the self-contained gas tanks and most that are suitable in size are only 2-3 hours per tank from what I could gather.  But still worth a look especially since they will maintain a 50 watt power supply.

Of course the more I am looking into it the more I realize there is to inverters.  I need to call tripplite since they say "nominal sine" which sounds a lot more like modified sine than true or pure sine.  Also it appears that getting more than 20 watts out of one is limited.  Seems to get an inverter really up to my tasks gets much more involved and costly than a generator.

As always more thinking and planning to do.
 

Karl

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Check out the EU2000I here: http://www.hondapowerequipment.com/gensup.asp  Up to 15 hrs on a single fill. Not sure which unit you were looking at, but most gensets run much longer than 2-3 hours on a fill. It will handle your battery charging needs as well, and with a unit called the "Charge Wizard", you won't have to worry about cooking the batteries. You probably want a genset AND an inverter for use when you don't have shore power and it's too late (noise-wise) to run your genset, but I'm guessing you aren't going to be working after 10 or 11 p.m. anyway, so that may be a non-issue.

Inverters are available in many sizes from those you plug into a cigarette lighter, to 2, 3, 4KW or more units. Just do a Google search and you'll find many choices. Modified sinewave is adequate for most things except electric clocks, some microwave ovens (they do work, but not as efficiently), and a few other electronic devices. Again, probably a non-issue, but true sinewave costs roughly twice that of others. I have a 3KW modified sinewave unit, and the only things I can't run are electric clocks and an electric blanket with electronic heat control. For those I'll get a small (250 Watt) unit.
 

Ned

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The typical RV inverter is connected to shore power and the batteries.  It contains a transfer switch so when connected to shore power, the AC is passed through to the output 120VAC circuits.  When no shore power is connected, the inverter produces the output 120VAC from the batteries.  When shore power is connected, the inverter charges the batteries, usually with a 3 stage charger.  Check out Xantrex, www.xantrex.com, for a good selection of inverter/chargers.  They have both modified sine wave and true sine wave (ProSine models) and are quite common in RVs.  The web site also has a worksheet for computing your inverter and battery sizes based on your projected AC use.

From what you have told us, solar will not be sufficient to handle your AC needs.  A generator will be a necessity for those times that shore power isn't available.  Karl has mentioned the Honda units and they are very efficient and quiet.  In the larger sizes, Onan is an excellent choice but larger is noisier and more intrusive.
 

Gary RV_Wizard

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Most setups don't actually use the batteries for 12vdc when they are connected to a shoreline.  The converter generally supplies the 12vdc in that situation while charging the batteries.  The issue I am facing is the power center not knowing that its AC source is the inverter rather than a land line.  Basically I would want the converter to disable when I am on inverter AC instead of a shoreline and run 12vdc off the batteries.  Otherwise the converter would use the inverters supply to run 12vdc and also try and recharge the battery - that would be pretty much a downward spiral.

You can get an inverter either with or without a built-in charger. If you get a model with an integrated charger (Heart, Xantrex, Prosine, etc brand names) then you should remove your existing converter. The inverter/charger will handle all battery charging and it also has an integrated transfer switch to avoid conflict with shore power.  If you get an inverter without an intergated charger and switch (the ones you see advertised for under $200), then you either add a transfer switch external to it OR be your own switch and ALWAYS disconnect the inverter from your rigs AC input BEFORE plugging into shore power.  The latter is almost guarunteed to result in a failure at some point in the future, when you are some helper forgets to disconnect one or the other.

Solar power is unlikely to produce enough DC for your mid-day power needs, even if you have 100+ sq. feet of panel surface and a really bright sun directly overhead.  Think of your solar panels as a battery charging source, not a power supply in itself. You will need a substantial bank of batteries to provide the sort of ready-use power you want, probably something on the order of 1000 amp-hours. Even then, it is possible (likely?)  that the voltage will falll far enough when the compressor loads come on (fridge and a/c) that the inverter will trip its internal breaker.  When a motor/compressor starts under load, the momentary curent draw is huge, typically 2x-3x the max running draw. That brief but huge draw sends the voltage plumetting below the 11 volt shut-off on the typical converter. The only way I know  to cope with it is to add batteries in parallel so that no single battery is stressed enough to lower its voltage very far.  [There are commercial power systems that can handle this situation with short term stored energy, e.g. capacitors, but they are large and expensive]. An alternative is to have a generator auto-start when loads exceed a pre-set threshold.

A 1000 watt Honda gen-set is essentially silent at about 15 feet. Nearer than that, it is only a background hum. The 2000 watt model is probably only  a bit louder, but I haven't heard one myself to say so for sure.
 

turboICE

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Jun 15, 2005
Posts
10
To run the Carrier AirV and other accessories is looking like the EU3000is would be more appropriate.

The thing is those run times that were quoted are at 1/4 load, during a nice hot day at Summit Point it would be easy to run over 1/2 load and get less than half that run time.

Regarding inverters even the good ones with integrated chargers don't seem like they transfer automatically - the only one that explicitly states that it does is the Prosine which would run nearly the EU3000is cost before batteries.

Still recovering from the cost of the trailer as it is, my finances keep trying to remind me that racing is a hobby - looks like this will be a long drawn out upgrade process.
 
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