battery voltage

[Ampman354]

Just wondering but is it possible to step-up the voltage of a 12v batter bank using transformers.  In doing this you would free the batteries used to increase voltage, so that they could be used to increase the Amp/hours.  If this not possible please explain, because my simple mind doesn't see why not.

[drdongle]

Firstly the only to step up a DC voltage is with an inverter ( DC to AC) or with a converter ( DC to DC). With either method you have losses ( all conversions have inherent and unavoidable inefficiencys ( theres no free lunch)). So lets say your going to step the 12 VDC to 120 VDC if your convert can handle 10 amps input ( at 12v)you will get a maximum of 1 amp out at 120 V (theoretical max) however as the process is inefficient ( imperfect) there is some loss so actual out put may be only .85 amps at 120 V.

Simple rule of thump is 12 V x10 amps+ 120 watts ( input ) out put will be 120V x 1 amp+ 120 watts - .15% ( for inefficiency)= .85 amps. some systems will be even less efficient running as low as 70%. The output ( VxA =Watts)will always be less than the total input.

[Ampman354]

I understand that there will be losses and of course if you start with 10 amps you'll go down to 1amp or so, in that situation.  Just wanting to know if it where possible to step up the voltage right away.

[Bruce S]

There are some simple ways using simple circuits. Do a Google for voltage multipliers and you should come up with some simple Cap & diode circuits; these you can use to bring the voltage up to just about any amount. HOwever they will still be DC you'll then need to build a circuit that makes what is called a MSW of modified sine wave, to get something the AC side will like. A somewhat easier way to get this would be to pick up an old battery backup unit, find the circuit that controls the alarm senseing flip it to be always on, make sure the batteries are all set and you're all set.

Still a whole bunch of losses though. I don't run anything more than a deep freezer on my little unit and anything with a startup Cap pops the inline breaker.

Cheers!

Bruce S

[finnsawyer]

The voltage multipliers only work with an ac source.  So he will have to convert the dc voltage to ac first.  Transformers, of course also require ac.  Note that with the transformers the ac will be cleaned up some due to the transformer's inductances.

[wooferhound]

DO NOT input a DC voltage to a transformer

A transformer is a Short Circuit to a DC Voltage

you may let out the magic smoke

from the battery and the transformer . . .

[Bruce S]

Should've included a small pic that works.

I go get to these heavy transformers when the destruction guys go clearing out offices.

This is one that I have had for some time.

Radio-Shack ( if you find one who has an employee that's been around awhile and knows how to look on their shelves.

Does use a power transformer unusual way but...

Also output voltage is of course dependant on input and values should be adjusted to power requirements.

Also this doesn't output the power you're possibly looking for , but does work.

Bruce S

[ibedonc]

you could use a BUCK-BOOST converter to setup the dc to another dc voltage

google on that

or look at projects @ www.redevices.com

[Dreadstar]

First things to consider in what you said.

take a 48vdc bank using 4 110ah 12vdc sla batteries and rewire it to 12vdc to get 440ah total capacity.

Either way you do it will net you exactly the same amount of available power.

with a 48vdc 110ah bank you have 5280watt/hours with a 12 volt 440ah bank you have 5280watt/hours.

There are dc/dc converters that you can buy/build to take 48volts and get 12 volts out for 12volt apps. and vice/versa.

But you will have less line loss if you have a 48volt bank over a 12volt bank since your amps will be dropped 1/4.

[ghurd]

Powerstream (.com) makes DC/DC units.

Good quality, great prices, etc.  IMHO

We have been using one for 4(?) years, 24 to 12V, not 24/7, but a lot of abuse with the elements, etc.  1/3rd the cost and a better product than the previous item we used.

Not related to them

G-