Inverter size

[Soundguy]

I am taking it easy.. you asked if it could be done.. I answered.. then you asked again. Asking questions isn't a problem.. it's when it looks like you are shopping for answers that it gets irksome.. Just about every technical based reply in this thread has concluded with virtually the same common answer. ( no you can't suck a battery flat with a standard on the shelf inverter & sucking a LA battery flat generally harms it )...

baring some creative charge pump circuitry that patG may or may not be refering to.. it would be cheaper to just get a fuel powered generator vs 'disposable' battery banks in a 'kill'em and dump'em' type circuit.

As has been stated.. if you throw a simple load on a battery.. you can zap it down to no charge differential. With a semiconductor driven circuit in the on the shelf invertors.. you simply get stuck inside 'goalpost' pre designed specification issues.

Soundguy

TAKE IT EASY I didnt ignore you.Im confused ,if i knew the answer,i wouldnt have asked the question.I asked why you could run a deepcell battery to nothing on a boatmotor[which is 12 volt]NO INVERTER and you dont hurt the battery,but you would ruin a car batteryand why cant you run it down to nothing with an inverter.If I wanted to go to college i would,but I dont need to,i got nice people here on TBN who answer my questions,sometimes even without barking.Thanks for the answers guys,im afraid to ask any more questions
ALAN

 

[patrick_g]

Soundguy, A charge pump is one such circuit that will sustain the output until there just isn't enough energy left at the input to sustain the output. It is NOT battery friendly. It is not economical (in most practical applications), or to be recommended for any "NORMAL" application without protection from over discharge. I was only answering the question... was there a way to get more out of a batt. Yes there is but it is not usually a good idea.

I personally don't understand why anyone would want to run a DC alternator off a PTO to charge a battery to run an inverter to make AC when you can just use the PTO to spin an AC generator. I had flashbacks to some of the elaborate Rube Goldberg cartoons.

You never get out of a batt nearly as much as you put in so if there is a simple way to skip the batt you may be ahead.

One project I worked on during my free lance consultant days was a battery operated portable welder. It took two 100 Ah 12 volt batts to provide enough umph to do meaningful welding. The best situation was when I connected the batts with solenoid/contactors such that the batts were in series to weld and in parallel to charge off the vehicles alternator. This was a niche product and in general was not the best choice for a welding power supply and batteries were part of the reason.

Pat

 

[schmism]

I personally don't understand why anyone would want to run a DC alternator off a PTO to charge a battery to run an inverter to make AC when you can just use the PTO to spin an AC generator. I had flashbacks to some of the elaborate Rube Goldberg cartoons.

Pat

you dont have an alternator or 2 laying around? With the pulley's that can be scrounged off of other scrap laying around, i could easly fab up a simple pully system to run at a lazy 1200 rpm or other low gas saving rpm (vs having to spin it at full 540 2400 rpm for a full size geny)

a larger 100 amp alternator can also be modified to run non-regulated for DC stick welding in the woods.... (this has been done for years in the 4wheeling world)

 

[Soundguy]

Soundguy, A charge pump is one such circuit that will sustain the output until there just isn't enough energy left at the input to sustain the output. It is NOT battery friendly. It is not economical (in most practical applications), or to be recommended for any "NORMAL" application without protection from over discharge. I was only answering the question... was there a way to get more out of a batt. Yes there is but it is not usually a good idea.

I agree completely. As you were doing.. I just kicked out an idea of how to suck the batteries dry and ruin them.. as that is what the poster obviously wants to do..

I personally don't understand why anyone would want to run a DC alternator off a PTO to charge a battery to run an inverter to make AC when you can just use the PTO to spin an AC generator. I had flashbacks to some of the elaborate Rube Goldberg cartoons..

I've seen them. Small gas engines.. or propane engines that run a low wattage alternator/genset.. that charges a lead acid (sealed ) battery, which is then hooked to an inverter. all in one very small package.. say the size of a basketball... i can't remember who makes them.. but honda comes to mind. What it gives you is a genny that has surge capability larger than the genset has.. thus it can be very small.. and have a motor the size of a weed eater to run the battery charger/dynamo. As long as you are only using the output wattage that is equal to the battery charge rate.. you won't discharge the system.. however you have the capability to get a higher load for shorter periods of time due to the storage battery.

If I remember correctly I have seen these in 2000w versions and propane... 850-1000 watt was sustainable.. and 2000w was sustainable till the battery drooped.. was quiet.. like 20 butterflies in a bucket near your head.. just a real muffled thump thump.. real fast...

A curiosity for sure.. but not something i need. For the money they cost.. I'd rather have a big beefy inverter say.. 2000w or so.. and a big battery for all the small loads.. and for the big loads just use my pto genset..

Soundguy

Soundguy

 

[patrick_g]

SoundGuy, Like it frequently does... it comes down to there is more than one right way to do something, more than one tool for a job, depends on what your mix of requirements is, depth of your pockets, and often your technical prejudices.

A couple things for sure: 1. just defeating the low volt protection is NOT a good idea on a typical off the shelf inverter if you want any reasonable batt life. 2. Charge pumps are great for systems with wide dynamic variations in input but are not magic and sure will eat batts if you have no low volt cutout.

I personally prefer a right sized solution. I'm sure their are circumstances for which the clever motor generator with battery storage and inverter able to play together in sync (like my Prius - - gas, electric, or both) is the ideal solution but I haven't had the matching problem yet.

Pat

 

[schmism]

those that are anti-inverter do relize that whole house PV and or other non-grid systems hinge around large banks of batteries and large inverters.

granted those large inverters are usually much more complex and output pure sign waveform ....

but inverters (large and small) do have there use and place

 

[patrick_g]

those that are anti-inverter do relize that whole house PV and or other non-grid systems hinge around large banks of batteries and large inverters.

granted those large inverters are usually much more complex and output pure sign waveform ....

but inverters (large and small) do have there use and place

Let me make one thing perfectly clear... An inverter is a tool/component. When analysis indicates an inverter to be the best solution (sometimes tempered by already owning 3) I go for it. I am not for or against an inverter per se, just like to pick and choose where/when they make sense.

About those PV/batt/inverter systems for whole house electrification. I have subscribed to "Home Power" magazine for years and NEVER ever saw a PV installation for a whole house that was driven by economics when the grid was there as an alternative. Only when the cost of getting the grid to a remote location was astronomical did whole house PV make economic sense. Most residential PV when the grid is available is so the user feels green.

Maybe this will change some day if electricity prices go high enough and technology improves efficiencies enough but for now PV doesn't cut it for residential power when grid is an available alternative.

I have PV "farms" on my camper and motorhome but they were a good economic decision compared to the price of a looooooong extension cord.

Pat

 

[Soundguy]

By the way.. just in case you are not aware.. I've been agreeing with your comments ont he messages in this thread. It sounds like you think my comments are somehow counter to yours.. when In fact they are inline.

soundguy

SoundGuy, Like it frequently does... it comes down to there is more than one right way to do something, more than one tool for a job, depends on what your mix of requirements is, depth of your pockets, and often your technical prejudices.

A couple things for sure: 1. just defeating the low volt protection is NOT a good idea on a typical off the shelf inverter if you want any reasonable batt life. 2. Charge pumps are great for systems with wide dynamic variations in input but are not magic and sure will eat batts if you have no low volt cutout.

I personally prefer a right sized solution. I'm sure their are circumstances for which the clever motor generator with battery storage and inverter able to play together in sync (like my Prius - - gas, electric, or both) is the ideal solution but I haven't had the matching problem yet.

Pat

 

[locknut]

I know this an older thread,but it sure is a good one and relevant to my current project.I've installed a 24V heater in my cab and it pulls 20amps on low and 25 amps on the high setting.Right now it's hooked in series to two deep cycle Group 27 batts rated at 182 reserve capacity minutes @25amps each.After reading here,it looks like a seperate charging system is going to be mandatory,even if I only use the heater for say 20-30 min at a time.

I've spotted a 1-wire 24V 50amp alt on ebay that I assume would work.I can use the mid pto under the tractor and it runs 2000 rpm.How do I make the transition from the pto shaft to the alt? Should the mount/pto shaft be electrically isolated from the tractor? And,how exactly should this be wired? Gauge required? Solenoid? Switch?

http://cgi.ebay.com/ebaymotors/24V-...7561567QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

 

[patrick_g]

Good generator buy:

All Power America Portable Generator — 6000 Surge Watts, 5000 Rated Watts, 13 HP OHV, Model# APG-3009 | 5,000 - 6,999 Watts | Northern Tool + Equipment

Also if you are thinking of running a big inverter off the battery you don't want a standard automotive starting battery. You need either the combination deep cycle/starting (marine service) or a standard deep cycle. If you use the standard deep cycle to jump something don't try to crank it right away. Let the deep cycle charge the distressed battery for a few minutes and then crank. Standard deep cycle batts are not designed for starting and can be damaged if used for that but they work well with an inverter and a standard starting battery doesn't (for very long.)

Pat