24 V DC to AC Inverter

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dmanda24

dmanda24

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I have some 24V dc to ac inverters they are sinewave inverters, not rectified sine like most cheap inverters, they were used to power cellphone sites, they have automatic transfer, and a whole bunch of other whistles. anyway they are just occupying space and I was thinking of installing the smaller one (4000 W) to the Van, and putting in and extra battery with a double pole double throw switch for being able to put the batteries in parallel for charging and in series for using the inverter. Any recommendations or precautions. Are there any implications on the alternator for adding another battery? All advice is welcomed
 
You will need to get (or rather, should get) a battery isolator to charge the second battery off the alternator. It's basically 2 big diodes, mounted in one heat sink. It has three posts. One for the alternator, a second for the battery A, and a third for battery B. You should also jump up a size or two on your alternator, since a typical stock one will self-destruct trying to charge two batteries if you run them pretty low while using the inverter before starting the engine.
 
dereckbc said:
Just curious what brand and model are they?
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Exeltech, and the model im not quite sure since its a module assembly it has 4 mx100 power modules, a control card a transfer switch card an alarm card, I know they are pretty expensive, I looked it up when I got them, but I don't remember anymore, I was planning on getting some solar panels to hook them up to the house, but haven't done it yet, maybe this year, hurricane season is upon us.
 
Couple of notes to yourself in addition to the isolation diodes.

  • The wire or cable to the inverter will need to be very large and kept short as possible to prevent voltage drop at 24 VDC. If you pull the full 4000 watts will translate to 170 amps @ 24 VDC
  • The other problem will be battery capacity and battery life. Auto batteries are not made for this purpose. Auto batteries are made for short burst of current to start a car, not prolonged deep discharges. The other issue is capacity. If you use a auto battery they are in the range of 45 to 60 AH or about 500 to 700 watt-hours. That isn't much time when connected to a 4000 Watt inverter, and running a skill saw off of it. You could find yourself needing a jumpstart at the end of the day when it is time to go home.
  • Last point the two batteries will need to be exact make and models to be series and/or paralleled.
 
dereckbc said:
Couple of notes to yourself in addition to the isolation diodes.

  • The wire or cable to the inverter will need to be very large and kept short as possible to prevent voltage drop at 24 VDC. If you pull the full 4000 watts will translate to 170 amps @ 24 VDC
  • The other problem will be battery capacity and battery life. Auto batteries are not made for this purpose. Auto batteries are made for short burst of current to start a car, not prolonged deep discharges. The other issue is capacity. If you use a auto battery they are in the range of 45 to 60 AH or about 500 to 700 watt-hours. That isn't much time when connected to a 4000 Watt inverter, and running a skill saw off of it. You could find yourself needing a jumpstart at the end of the day when it is time to go home.
  • Last point the two batteries will need to be exact make and models to be series and/or paralleled.
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What would you say the max recommended wattage for this kind of set up would be?
There are four modules to the inverter I can take one or two out and make it 3 or 2 kw
 
dmanda24 said:
Exeltech, and the model im not quite sure since its a module assembly it has 4 mx100 power modules, a control card a transfer switch card an alarm card, I know they are pretty expensive, I looked it up when I got them, but I don't remember anymore, I was planning on getting some solar panels to hook them up to the house, but haven't done it yet, maybe this year, hurricane season is upon us.
Click to expand...

I was about to say these are a heck of a lot better inverters used in solar PV apps. The stuff they make is pure junk.

If you do use them in a solar PV system you are talking some huge expense to take advantage of these monster inverters like 4 to 8 KW solar array, and if used off-grid and 4000 AH batteries @ 24 VDC is around $50K plus that much more in solar panels. Only problem is I doubt the inverters could be used in grid tied systems because they do not have the capability to sync with the POCO or auto shut-off in the event of power failure. So you could probale only use them in off-grid app.
 
id sell them off to a place that buys telecom equipment and use the proceeds to purchase the correct inverter for your application (and you'll probably have a ton of $ left over too)
 
dereckbc said:
I was about to say these are a heck of a lot better inverters used in solar PV apps. The stuff they make is pure junk.

If you do use them in a solar PV system you are talking some huge expense to take advantage of these monster inverters like 4 to 8 KW solar array, and if used off-grid and 4000 AH batteries @ 24 VDC is around $50K plus that much more in solar panels. Only problem is I doubt the inverters could be used in grid tied systems because they do not have the capability to sync with the POCO or auto shut-off in the event of power failure. So you could probale only use them in off-grid app.
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You can connect them to your house grid, since it has an automatic transfer switch, but you cannot use them while the power is on to put power back on the grid and sell power to the POCO since as you said it does not have the avility to sinc with the grid.
 
wireguru said:
id sell them off to a place that buys telecom equipment and use the proceeds to purchase the correct inverter for your application (and you'll probably have a ton of $ left over too)
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probably the best thing to do, but not sure who would buy used equipment
 
dmanda24 said:
probably the best thing to do, but not sure who would buy used equipment
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eBay that crap. There's enough people experimenting with home-brew solar right now, the time is right to sell it on the open market like that. The demand is great right now, is what I'm trying to say.
 
dmanda24 said:
would I still need the DPDT switch?
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Yep. Need a diagram? :grin:


dmanda24 said:
What would you say the max recommended wattage for this kind of set up would be?
There are four modules to the inverter I can take one or two out and make it 3 or 2 kw
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That's not necessary. The inverter will only use what it must to produce the current you're trying to get from it.
(This ignores losses and inefficiencies, of course)

If you use 2kw, it'll pull half of the 170a anyway; the extra modules won't change that. I'd rather have them in for starting current, short-term peak demands, and reliability.

There should be no issue with jump-starting at the end of the day because, as Derek said, you should use matching batteries, and they should be independent of the vehicle's electrical system.

Since you can't charge at 12v and use at 24v at the same time anyway, you won't be able to use the inverter while recharging from a vehicle. Why not just make it an independent 24v system with a 24v plug-in charger?

You should definitely use deep-cycle batteries. Nobody says you can only use two, remember. If you find you don't get enough run-time with one pair of batteries, add a second pair, wiring them in parallel-series.

Truck parts and accessory stores have a lot of pre-made battery cabling. I've seen cable assemblies with two, three, and four battery clamps. The wire was larger than anything you'll find at the Pep Boys, NAPA, Auto Zone, or Advance.
 
LarryFine said:
Since you can't charge at 12v and use at 24v at the same time anyway, you won't be able to use the inverter while recharging from a vehicle. Why not just make it an independent 24v system with a 24v plug-in charger?
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got a diagram? j/k what do you mean by a 24V plug-in charger? A DC-DC converter??
 
dmanda24 said:
got a diagram? j/k what do you mean by a 24V plug-in charger? A DC-DC converter??
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No, a 24v charger that runs on 120vac. If there's power at a jobsite, charge it up. Otherwise, wait until you get home and plug it in there.

An alternative is to find a 24v alternator with built-in regulator, and find a way to mount and drive it from your engine.
 
Ya know if you really want an inverter for your vehicle, you would be much beeter off just buying a 12 inverter. Then you can just run the vehicle while using the inverter and not have to jury rig a thing.

How much you want for the thing? I got an application for one.
 
wireguru said:
id sell them off to a place that buys telecom equipment and use the proceeds to purchase the correct inverter for your application (and you'll probably have a ton of $ left over too)
Click to expand...

Do you know of a place where I can sell this?
 
i know of a guy who deals in surplus cell site equipment, i bought some network gear off him one time. I can try to dig out his contact info, but no guarantees as it was a couple years ago.
 
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