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Old 02-19-2017, 11:54 AM   #1
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How many amp hours do I have?

I have two Interstate Group 24's on my 23FC FB. Dumb Question: They say 550 CCA, 690 MCA, and 140 RC. I think Cold Crank Amps are just what they can produce in short bursts. MCA, no idea. RC no idea.

How many amp hours to I have, and what do amp hours really mean? I'm doing a lot of reading but struggling with making sense of it all. Assuming batteries are fully charged (mine show about 12.8 on a meter at the terminals), how many watts can I run for how long? (Variable of course based on power usage.)

Just trying to get a better understanding of all this. Thanks in advance.
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Old 02-19-2017, 12:09 PM   #2
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The Interstate SMR-24 batteries have a spec of 84 AHr each. Since you have two and you should never deplete your batteries more than 50% if you want them to last, you have 84 AHr of usable capacity available. So if you're drawing, let's say 8.4 A from your battery, then you'll have 10 hours, and so forth.
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Old 02-19-2017, 12:28 PM   #3
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Quote:
Originally Posted by alano View Post
The Interstate SMR-24 batteries have a spec of 84 AHr each. Since you have two and you should never deplete your batteries more than 50% if you want them to last, you have 84 AHr of usable capacity available. So if you're drawing, let's say 8.4 A from your battery, then you'll have 10 hours, and so forth.
Thanks...very helpful. Why wouldn't the battery be labeled with the spec for Amp Hours? Can it be calculated using the information that is printed on the battery? EDIT...OK so I found some info that multiplying Reserve Capacity by 60% tells you the Amp Hours. I guess this is based on 80 degrees as well, and would be less in colder temps, since RC is measured at 80 degrees.

Probably the most complicated part of RV'ing....
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Old 02-19-2017, 01:00 PM   #4
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Great question, If you are going to do any dry camping (2 to 3 days) the
interstate will not holdup and a very limited warranty even the AGM they sell do not hold up, only come w/ 1yr full warranty.

After a lot of study and going thru one set of the interstate I went with LifeLine 6V AGM,
Rated Cap.
Amps Hours @ 20hr Rate 220 amps 1-6V Batteries

Minutes of Discharge
*
25 Amps 492
15 Amps 856
8 Amps 1692

All Lifeline deep cycle batteries are backed with an industry leading 5 year warranty.

2-6V LIFELINES, 440 amps
@ a 20hr rate or 1712 minutes of Discharge

Your two interstate will only give you @ a 8.4hr rate or 540 minutes of Discharge and once you go to 50% of the battery they are dead and will take you a full day to restore the battery.

AMG you can take down to 80% to 90% before you will need a complete recharge and does not hurt them.

I also change to a Boondocker BD1260C (60 Amp 4-Stage Converter/Charger) w/ Trimetric 2025RV Battery System Monitor. Got a Honda propane generator and now
NO power problem, now I can go were I want too and stay as long as I want.
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Old 02-19-2017, 01:08 PM   #5
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I think MCA is marine cranking amps. RC is reserve capacity. I don't know if/how you can relate them to amp-hours. Those specs are typically for combination or starting batteries, not "deep discharge" batteries. Make sure your batteries are rated for deep discharge RV or marine use. Typical auto starting batteries do not like to be discharged over long periods of time as in boondocking use.

Assuming your batteries are rated for deep discharge use, what Alano says is correct. You have 84 AH of useful capacity. If they are starting batteries, they won't last long boondocking in travel trailer service.

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Old 02-19-2017, 02:52 PM   #6
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Quote:
Originally Posted by dames7 View Post
If you are going to do any dry camping (2 to 3 days) the
interstate will not holdup
Well, maybe. It depends on your usage. Mine regularly last me 2-3 days and frequently more.
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Old 02-19-2017, 03:18 PM   #7
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I have a single WalMart lead acid Group 24 starting battery. I have dry-camped for 4 days using the Fantastic fans, refers, water heater and water pump (Navy shwrs) and lighting, and watched two football games and one DVD... all on that battery. (I did remove all the incandescent lamps and replace them with LED cheapies from china.)

I then recharged the battery for 3 hours using a generator, and did it again for 3 more days (although only used the tele once and the stereo a couple times for weather reports and fake-news.

BTW, that battery is 3 years old and stays on a constant charge when in storage using the OEM WFCO converter the 2008 Sport came with. (and I do not bother to have a battery monitor at all. I do check the water level every 2 months tho'.)

I keep a bottle of salt-pills handy when reading all the woes others report on their batteries and how much they fail to report their new wonder-battery "solutions" cost them.

I can replace my WallyMart battery for $84 every 3 or 4 years and be happy with that.
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Old 02-19-2017, 03:23 PM   #8
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How many amp hours do I have?

I am not aware of any AGM where going below 50% is recommended. I could be wrong but was told by several experts on this site that if you have 440 amp hours of AGM, you essentially have 220 available and they should not be discharged below 50% or they will be damaged and not last very long.

Again: AGM are still lead acid batteries, just sealed and as such should not be discharged below 50%!

Lithiums are the only batterie where discharging to 80% are considered normal operations.

Check out amsolar.com they have a great Learning/primer that explain the differences between AGM/Lithium/lead acid wet cell.

Full link below to article:
http://amsolar.com/diy-rv-solar-inst...s/edbatteries/
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Old 02-19-2017, 03:34 PM   #9
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Dames,
After more research on the actual lifeline site, they state as follows:

"What depth of discharge should be used when sizing a battery?
To get the best cycle life, the average depth of discharge should be as low as possible. Concorde recommends the average depth of discharge to be no greater than 50% of the battery’s 20 hour rating."

If you are discharging below 50% you are killing your batteries: Link below.

http://lifelinebatteries.com/faq-items/
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Old 02-19-2017, 04:07 PM   #10
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I read a lot in this forum about Lifeline AGM batteries. Just curious why Lifeline seems to be the brand of choice. I chose Crown 6 Volt batteries and they were just a tad less expensive than the comparable Lifelines. Crown has been a leader in the Golf cart world for some time and has a good reputation right up there with Trojan.

The same would be true with LifePo4 lithiums. Victron seems to be the most popular yet CALB, and Enerdel offer LifePo4 batteries for less than half the price. One may have to make a few connections, but for a couple thousand dollars I can do some work. Now the Enerdel at $1500 for 400 AMPs would not include a BMS, but do you really need one if you have a programable charger?

I'm not saying one is better than the other...just curious.


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Old 02-19-2017, 09:22 PM   #11
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The BMS does a lot more than control charging. It is the safety net to protect the battery, user and the trailer.
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Old 02-20-2017, 09:04 AM   #12
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We used our stock Interstate group 24 batteries for 3+ years, and mostly boondock. We recharged with solar or a generator when needed. They held up fine and are still being used as trolling motor batteries. After much research, last year we switched to two 220ah Lifeline 6v batteries based on the durability and added capacity. No regrets on the change.

As other have said, it is recommended never to go below 50% state of charge with either flood or AGM batteries. Also, a battery monitor was one of the best things we put in for boondocking. We installed a Trimetric 2030RV in our AS and our truck mounted camper.
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Old 02-20-2017, 09:46 AM   #13
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dames7 states:
"After a lot of study and going thru one set of the interstate I went with LifeLine 6V AGM,
Rated Cap.
Amps Hours @ 20hr Rate 220 amps 1-6V Batteries

Minutes of Discharge
*
25 Amps 492
15 Amps 856
8 Amps 1692

All Lifeline deep cycle batteries are backed with an industry leading 5 year warranty.

2-6V LIFELINES, 440 amps
@ a 20hr rate or 1712 minutes of Discharge

Your two interstate will only give you @ a 8.4hr rate or 540 minutes of Discharge and once you go to 50% of the battery they are dead and will take you a full day to restore the battery."

You only get 220 amps from two 220 amp 6 volt batteries to get 12 volts output.
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Old 02-20-2017, 09:51 AM   #14
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With proper care and feeding, My group 29 Interstates wen 5.5 years before one cell in the pair went bad.
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