Battery utilization question

New_Climber
New_Climber Registered Users Posts: 12 ✭
in Solar Beginners Corner #1
Hello, New here and VERY new to solar. I am still reading though the posts with great information...

One thing I was hoping you could clear up as I am looking at my own solar design...like I said I have much more to read.

I see many people using T-105 Trojan Batteries...Looking at the specs of the T-105 on the Trojan web page, many us 225ah in their calculation...

Where do they get this number?? Is it the "20Hr rate AH" number" at 225ah??

Also, I understand that we only want to discharge a battery to 50%. So you would take 50% of the rated AH's....BUT if you are using a 12v battery setup, would you not be able to double the given AH's of a 6v battery being you need to put 2 of these in series to get your 12V???

So wouldn't 2-6v T-105's get you a total of 450ah of which you would only want to utilize down to 225ah total??

Thanks for the help...and this site has some GREAT information... sometimes it is information overload...
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Battery utilization question
    Where do they get this number?? Is it the "20Hr rate AH" number" at 225ah??

    Yes

    Also, I understand that we only want to discharge a battery to 50%. So you would take 50% of the rated AH's....BUT if you are using a 12v battery setup, would you not be able to double the given AH's of a 6v battery being you need to put 2 of these in series to get your 12V???

    So wouldn't 2-6v T-105's get you a total of 450ah of which you would only want to utilize down to 225ah total??

    Batteries in parallel, amps add, you you would have 6V @ 450A

    Batteries in series, VOLTS adds up, so you have 12v @ 225A
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  • drew4justice
    drew4justice Solar Expert Posts: 36 ✭
    #3
    Re: Battery utilization question

    Hi. I'm fairly new as well, and I usually only open my mouth to change feet, but I'll give it a whirl...

    As I understand it you divide the given aH by the rate of time, so in this case 225/20 = 11.25, so you could essentially pull out 11.25amps, per hour, for 20 hours before the battery is considered discharged.

    Given two batteries, the aH capacity doubles only when you parallel like batteries, but the voltage stays the same. In this case the voltage would remain 6v, the aH capacity is now 450. If you series them together, you double the voltage, but the aH stays the same. Now you'd have 12v, 225aH.

    I have 4 t-105's in series for a total of 24v @ 225aH. If I want to increase my aH, I cannot simply add one more battery in parallel to an existing battery, I'd need to buy 4 more, connect them in series, then parallel the two 24v strings together. I would then end up with 24v @ 450aH.
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  • New_Climber
    New_Climber Registered Users Posts: 12 ✭
    #4
    Re: Battery utilization question

    Thanks guys....

    I forgot all about parallel vs series calculations....makes all the sense in the world now...
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