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 | realman21502
Join Date: Jul 2003 Posts: 48 Maryland 
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2004-03-10 79497
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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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2004-03-11 79535
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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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-03-13 79765
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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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-03-13 79789
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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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-03-14 79824
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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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-03-19 80449
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. ....
Link: One of many sites with basic info.
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 | agentorange
Join Date: Feb 2004 Posts: 117 Pacific Northwest
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2004-03-20 80477
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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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-03-28 81446
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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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-03-29 81460
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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 | AC5ZO
Join Date: Jul 2003 Posts: 928 Rio Rancho, NM 87144 
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2004-03-29 81486
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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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-03-29 81497
Thanks guys. I am going to try the 24-hour trickle charge. This site really has knowledgeable members. This morning I lost a neighbor of 40 years in a house fire but I will read in more detail the post to my question. He was near the point of death from ephemera but the entire attic was involved before they knew the house was on fire. His wife lost some hair but made it out. She and a nearby son just could not get him out of a window but the fire department arrived and kept the fire from his body. If you are planning to build and like me have (or may have) mobility issues look at having an outside exit from your bedroom. Batteries are still on my mind but my day would have been better if my neighbor had had an exit door in his bedroom. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-03-30 81529
Oh man, too bad about your neighbour and it's not an easy time for you either. The exterior bedroom door idea is a good think to think about. We have a fire safety video in our Library that shows a frame house going from start to completely engulfed in about 10 minutes. The messages is that even with smoke detectors--if hear it there's no time to do anything but get out immediately. Standard houses really aren't good for many seniors and people with limited mobility.
Very good info from AC and I learned something about batteries. Maybe we'll get back to the subject. ....
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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-04-01 81807
Battery charging update. I tried the trickle charging idea and it worked. As a reminder from my post above I had 4 deep cycle identical batteries that would stop taking a charge at 2, 2, 3, and 4 amps on the charger meter.
First working with the battery that would stop taking addition charge at 4 amps I would knock off the surface voltage by using about a 500 watt load for 1-2 minutes (700 watt inverter running some lights and fan) and then trickle charge for about a day. Repeat knocking of surface voltage and to regular charge, then repeat the trickle/full charge cycles.
The first time it would still drop down to only 4 amps when fully charged. It went to 3 amps after the second set of cycles and went all the way to 2 amps after the third cycle. I will try this a few more cycles to see if it will approach Zero but first I am working to see if I can now get the two batteries that were only dropping to 3 amps down to 2 amps so I have 4 batteries stopping at the 2 amps point.
....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-02 81845
Good that the trickle charge thing helped. Somebody who knows batteries such as AC proably will weigh in on this. As far as I know you get the full effect pretty quickly and you can't expect to get all batteries to very similar charge states. Even if you do you they likely wouldn't stay there after some use. There may be further room to tinker by doing hydrometer checks on individual cells and adding a bit more acid here and there. I'm being vague here since I don't know if that'd work or be a good idea even if it did.
I would keep in mind that AC said that the application would be unlikely to damage the batteries anyway--no guarantees though. For me it'd be fun to keep experimenting with things but I would keep in mind that it might end up crafting a solution that then needed to search for a problem.
I seem to remember that this is for a computer network. My individual PC backup has a USB connection to the computer. It's supposed to backup open files and then execute a Windows shutdown when the battery supply starts getting low. Something like that also should prevent the battery mismatch problems described. ....
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 | blizzard
Join Date: Jul 2003 Posts: 282 Central Maine
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2004-04-02 81853
I believe battery chargers used for large battery banks in solar and diesel generator applications are 'smart' and have a conditioning phase where they slightly overcharge the batteries to ensure they are all as similar as possible.
I don't know if the trickle charging of individual batteries in the bank can achieve the same results, but I don't think it will hurt anything. I wonder after a number of discharge/charge cycles if the 'off' batteries revert to their original condition.
Just my 2-cents,
bliz ....
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| GaleHawkins
Join Date: Dec 2003 Posts: 44 KY
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2004-04-10 82664
As a follow-up I have not yet connected the second set of batteries for my office 5.3kVA UPS but I have been able to get all 4 conditioned by trickle charging as mentioned above to stop charging at the 2 AMP reading on the scale now when doing a full rate charge by working with them individually using a 12 volt charger. Soon I will use them to build another 48-volt pack that will be connected in parallel with the other 48-volt pack. Below is what a tech from another forum had to say about adding the second 48-volt pack in parallel. Remember all 8 batteries are new, the same brand and same specs and from Wal-Mart. :)
Other forum reply:
No, the battery charger will not exceed it limits. The added 48 v pack will not cause undue hardship, but will require slightly more than twice the time to charge. "Slightly" due to the added internal resistance of the added batteries. Run time will basically be doubled
Before you add an another set, check the batteries are not excessively "gassing", produced by excessive charging voltage. This should not be an issue due to the circuitry was designed for sealed batteries. Simple remove the cell covers, you should not see gas bubbles, maybe occasional small bubbles are OK, large and numerous bubbles, are not good, in a fully charged battery set. The room these batteries are in should have a small amount of air exchange, all open cell batteries do produce a small amount of hydrogen gas, (from first hand experience, it is explosive). As long as they are not contained in an airtight room they are safe.
....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-04-11 82710
Sounds like a good outcome and there's been decent comments all around. Maybe we've all learned something. For myself I might have guessed that hooking a charger across several batteries in parallel would increase the charge time but not the load on the charger if I though about it. It didn't occur to me at the time and now I know. It makes a lot of sense that chargers would be designed to limit current at low load resistance. ....
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