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Old 12-14-2017, 06:59 AM   #1
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Determining Amp-hour capacity of a battery bank

Aloha all!

Thanks in advance for your input.

I have a new to me 2007 National Pacifica qs40c. Yesterday I installed 4 shiny new Crown CR-235 6 Volt Batteries (spec sheet attached). They are wired 2 each in a series and the two sets of 2 in parallel.

Now I want to program my Xantrex Freedom 2000 W Inverter/Charger. I have to set the Amp-hours of the battery bank.

I'm thinking because I have 2 each in a series (so that it's 12 volt), and the manufacturer rates them as 235 amp batteries (20 hours) that I have 470 amp hours total at 12 volt. If there are any experts watching, please share your thoughts. I want to get every last amp into these batteries!
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File Type: pdf CR-235 PowerSheet_D06235_0213.pdf (799.6 KB, 62 views)
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Old 12-14-2017, 07:06 AM   #2
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Originally Posted by KimoJames View Post
I'm thinking because I have 2 each in a series (so that it's 12 volt), and the manufacturer rates them as 235 amp batteries (20 hours) that I have 470 amp hours total at 12 volt.
Correct.
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Old 12-14-2017, 07:28 AM   #3
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Correct
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Old 12-14-2017, 08:09 AM   #4
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^x2
Batteries in series, voltage adds, current (amps) remains the same.
In parallel, voltage remains the same and Current adds.
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Old 12-14-2017, 08:40 AM   #5
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400 or 600

Thank you Mark and Twinboat!

So now I realize that my options for setting the Xantrex with the basic remote panel that was installed, seem fixed. I can either go with 400, which seems like I would loose the top 15% of my battery capacity (which is where I want to operate w/ solar), or 600 which seems like runs the risk of overcharging/boiling/not good. Are those assumptions correct?

I've read the manuals for the xantrex and the remote and neither offers a hint that customizing might be possible. Can it be done with the basic remote panel? Or, do the upgraded remotes (1000 & 2000) offer the ability to input the exact amp-hours?

Any thoughts would be appreciated.
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Old 12-14-2017, 08:59 AM   #6
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I believe using the 600 AH setting, over the 400 A setting, just extends the absorbsion charge time. If I recall its about a half hour longer. With solar you can just leave it at 400 AH and let the panel controller handle the rest.

Just looked at the specs, the 600 AH setting adds an hour to the 2 hour absorbsion charge for 400 AH banks, making it 3 hours. The only other choice is 1 hour for less the 200 AH.
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Old 12-14-2017, 11:00 PM   #7
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Don't forget to get the voltage sheet from Crown for those batteries so you can set the charger voltages for absorption and float for your new battery's. I was kind of surprised how low the default voltages were on my Magnum compared to what the battery manufacturer recommended. I heard the crowns required even more voltage than my Duracell's. I will be replacing them with Crowns in the next few weeks, once I get the trimetric installed and usable.
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Old 12-15-2017, 09:36 AM   #8
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... I was kind of surprised how low the default voltages were on my Magnum compared to what the battery manufacturer recommended. ...
Sounds like most need adjustment

https://handybobsolar.wordpress.com/...ging-puzzle-2/
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Old 12-15-2017, 10:38 AM   #9
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xantrex adjustable voltage?

I've been all through the xantrex manual and remote manual and they have fixed voltages. 14.4 for acceptance and 13.5 for float. Crown says 14.5 but I think even that is low if you really wast to get all of your amps in the batteries.

When I add solar, I'll have a controller and then I'll be in control.

Anyone ever figured out how to up the charging voltage on a xantrex 2000 Watt Inverter/Charger?

Thanks,

James
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Old 12-15-2017, 03:54 PM   #10
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Set it for 600 , that way you will be sure to fully charge the batteries. I charge my batteries at 15 volts , and the float is set to 13.2. You should also use the remote battery temperature sensor. This will automatically adjust the charging voltage on the inverter to prevent over/ undercharging of the bank.
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Old 12-15-2017, 04:07 PM   #11
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I just let my midnight solar controller fed by 1500w of panels handle most all the charging needs. Its better and more configurable.
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Old 12-15-2017, 04:41 PM   #12
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Those total AH values have little effect on the Xantrex performance. It's mostly a matter of displaying reasonably accurate percentages of charge remaining. Probably some minor effect on the bulk & absorption time, but probably not very significant in the big scheme of things. It will always fully charge the batteries (eventually), whether you say there is 1 AH or 1000. The batteries will always accept what amps they can use, and the charger will always provide them. That's pretty much the definition of absorption charging (aka acceptance charging - what the battery will accept).
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Old 12-15-2017, 05:12 PM   #13
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Those total AH values have little effect on the Xantrex performance. It's mostly a matter of displaying reasonably accurate percentages of charge remaining. Probably some minor effect on the bulk & absorption time, but probably not very significant in the big scheme of things. It will always fully charge the batteries (eventually), whether you say there is 1 AH or 1000. The batteries will always accept what amps they can use, and the charger will always provide them. That's pretty much the definition of absorption charging (aka acceptance charging - what the battery will accept).
Setting it to 600 AH adds an hour to absorbsion charge. That's 50 % longer then the 400 AH setting of 2 hours.
That's a minor, insignificant effect ?
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Old 12-15-2017, 05:44 PM   #14
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effect

I set the xantrex to 600 and fired up the generator. It's 8kw diesel onan that puts out 30 amps. It ran 90 minutes before it went to float. Almost no bulk time so basically 90 minutes of acceptance.

I'd still love to know how to adjust the charging voltage on the xantrex. I think it's just not possible.

Great ideas and input from everyone. Much appreciated!

James
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