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Power Inverters
I was thinking of installing a power inverter on my tractor. I know 1 horsepower is equivalent to 750 Watts. Does that mean a 2000 watt power inverter would run a 2 horsepower electric motor? Do these inverters work?
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Power Inverters
You'd need an allowance for losses and I think AC motors are maybe around 90% efficient. The inverter would have to be able to handle the start up surge, which would be greater than current for the rated HP. Most motors have surge ratings.
Sure inverters work, solar power folks run their entire houses off them. A 2hp motor would be far beyond a tractor's alternator's capacity and would draw down the battery pretty fast.
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Power Inverters
I sure could used some help on this subject. The office complex we leased last year has a Best 5.3KVA UPS system hirewired into our electical service for the server room.
Age is unknown but the batteries died (bone dry). Since I could get deep cycle marine batteries with same specs at Walmart (except they are not spill proof) for about $450 less guess what we did?
Since these are not spill proof and the UPS is located in a utility area we just left the front cover off and now have the 48 volt pack (4x12v)sitting in front of the unit with the cables connected the same. Actually I went back and got 115 AH batteries instead of the standard 75 AH rating.
My question has more to do with the charger. Now that we are thinking outside of the box  we could build another 48 volt bank and connect it in parallel with the first bank to double our run time.
Will the charger handle this is our question? If the extra load on the 48 volt charger will only mean it will take twice as long to recharge in the event of power outage that is fine? If it could make the charger exceed its rated output and kill the charger then adding the second bank would be a big no no?
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Power Inverters
Realman, Walmart carries one for about $80-90 that is good for 700 W cont or 1400 W surge that you just clip to your battery post. If it did what you wanted you could then hardwire it and have it with you at all times if you could get it mounted where no rain could get on it. It would be nice when you were broke down on the back 40/400 ect and could look up 2 or 3 banks of 250 watt work lamps.
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Power Inverters
I'm not sure there's an easy answer for the charger question but maybe others have some experience. Two batteries in parallel would half the load resistance. In theory that may blow the charger. However, the charger may have a limiter, or high loads may drag down the output voltage. It might be good to contact the charger manufacturer and get their recommendation.
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After a lot of research and talking with US Battery it seems like charging in parallel only means the charge is split between the batteries there for increasing the time required to bring the batteries to a full charge. I guess lead-acid batteries are not of much interest to most as long as their car starts. Actually I found learning about deep cycle batteries to be interesting. The typical deep cycle battery is good for about 300 recharging cycles and only reach full output ability after 20-50 cycles. That means most will die of old age before they ever reach full potential. I am glad people are not that way.
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Power Inverters
watts= volts x amps
you want to run a blender thru an inverter
the blender draws 4.0 amps (info on blender dataplate)
it is a 120vac blender (off your kitchen counter)
it will take 480 watts of power use it (120 x 4.0)
that is ....once it's up and running
surge wattage may be 6.0 - 8.0 amps
as it's running you throw a frog in there
will "bog down" and draw a bit more before it levels out
when buying inverters go big
2 batteries at 6volts in series will be a better 12v source than 1 at 12v
most of these terms are general
good luck, have fun
-ao
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I have another question related to my first one. In checking I learned it was OK to install another 48 volt battery pack in parallel so I purchased 4 more identical deep cycle batteries and all dated Mar 04. In initially charging each one on a 12-volt charger before connecting them to make the 48-volt pack I noticed something that I do not understand. On one battery the charger will taper down to 2 amps, two will taper to 3 amps and one will only taper down to 4 amps. Can someone explain this? Batteries connected in series need to be identically in function.
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I've heard that batteries may not come up to full charge unless they're changed for 24 hours at a trickle rate after higher rate charging. Could be that the minimum charge rates would even out if the packs were trickle charged.
Manufacturing differences could result in varying maximum internal resistance but I wouldn't know how much variation to expect. The different minimum charge rates may affect the amp-hour rating rather than the initial voltage/current delivered. If so then one battery with lower capacity in a series connection would reduce the time a backup pack would support the system rather than the voltage/current delivered initially. It's all speculation on my part. Somebody who knows batteries may have something more definite to say.
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What you are seeing is a natural variance between battery cells. It should not cause you a problem in most applications, but for very critical applications it is important to "balance" the batteries for voltage and discharge capacity. The only way to do this is to discharge the battery to measure it directly. For the critical applications you match the cells with similar performance.
You might see a problem ONLY if you run these slightly mismatched batteries completely flat. In that case, the battery with the lowest AH capacity will go flat first while the others still supply power and that can reverse charge and damage the flat (0.0 VDC)cell. This should not be a problem if the UPS stops working at something on the order of 40 VDC and that will make sure that none of the cells are reverse charged. But, if the UPS can run until the batteries quit, then battery damage is a possiblility.
BTW, a fully discharged cell does not mean 0 VDC, it means something on the order of 1.65 volts per cell. Each 12 V battery has 6 cells and should not go below about 9.8 VDC at full discharge. If you take a battery below this voltage it can be damaged. Using balanced batteries will assure that you don't damage one battery of the four you have in series if you do a full discharge on occasion.
Running batteries in parallel to get more AH capacity is generally not a problem. The parallel batteries will accept or discharge current based on their voltages and will tend to balance each other out. So, if you have two batteries in parallel and battery 1 has a higher voltage than battery 2, it will provide the most current when required and take the least current upon charging until the other cell (battery 2) catches up. This process will automatically go back and forth during charge and discharge and you don't have to monitor it. Any imbalance will also correct itself as the higher voltage battery (1) charges the lower voltage battery (#2) until they are the same voltage and current stops flowing between the two.
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Gas Generator Weather Protecti
03-10-2004, 19:47 
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