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12V or 24v ?
By gblass1, Section Newbies Posted on Sun Oct 04, 2009 at 06:34:08 AM MST
Need help understanding this.

Hi All
I'm trying to understand the difference between using a 12 or 24 volt system. I found this online calculator http://www.theinverterstore.com/tips.php (scroll to the bottom of the page) that gives you runtime for a given load based on your battery amp hours and voltage. Ok here is were I get lost, if I put in a load of 1000 watts and a battery bank with 900 amp hours (4 Trojan T-105's) it gives me a run time of 4.5 hours at 12v and 9 hours at 24v. I thought amp hours were amp hours.
What am I missing ?
Thanks
George

12V or 24v ? | 4 comments (4 topical)

Re: 12V or 24v ? (3.00 / 0) (#1)
by Flux on Sun Oct 04, 2009 at 07:01:57 AM MST

Amp hours are just that.

For a given capacity in Ah you can get so many amps for a given time.

Power is volts x amps so for a given power load you can get twice as many watt hours of energy from a 24v system compared with a 12v one.

You can look it at it the other way and you need half the current for the same power on a 24v system. This means that for the same energy store your 24v battery can have half the Ah capacity of a 12v one.

Think of it this way, if you have 2 12v batteries of 100Ah capacity and you connect them in series you have 24v at 100Ah. If you connect them in parallel then you have 200Ah at 12v. Neglecting other minor factors they store the same energy.

Flux

Re: 12V or 24v ? (3.00 / 0) (#2)
by snake on Sun Oct 04, 2009 at 11:33:10 AM MST

hi,i dont know if that will help.so,for example if i have 2 12v 100A/H battery and i connect them in series,the voltage will combine and give 24v and the amps will remain the same,100A/H, in terms of watts,I x V =2400W

now lets take the same battery and connect them in parallel,so,the voltage will remain the same,12v whereas the amps will double,200A/H and the power will be, IxV=2400W

you can see that the power in both configuration remain the same.the only difference in 12v and 24v setup is that there is less power loss in a 24v setup than in a 12v setup.

Re: 12V or 24v ? (3.00 / 0) (#3)
by RP on Sun Oct 04, 2009 at 01:32:32 PM MST

The premise of the question is flawed.

4 T-105s wired in series-parallel for 12v is a 450amp hour bank at 12 volts (not 900 amp hours)

4 T-105s wired in series for 24v is a 225 amp hour bank at 24 volts.

both of these would store 5.4KW hours.

Re: 12V or 24v ? (3.00 / 0) (#4)
by kurt on Sun Oct 04, 2009 at 03:51:59 PM MST

i think you are getting messed up because that calculator does not ask you how many batteries you have at what amp hour rating and voltage each it only asks total amp hours of the battery bank and bank voltage the amp hours of a set of batteries can change depending on how you hook up the individual batteries up for the voltage you want to create your battery bank but your watt-hours will always be the same. is that clear as mud for you???

IRC inst.
just a personal rant carry on.

12V or 24v ? | 4 comments (4 topical)

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