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Old 01-11-2017, 09:06 PM   #21
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Everything everyone here said is correct. To try and get some use out of the battery that came with your unit the battery that you bought is correct to pair up with what you have. For $67 you have doubled the battery capacity in your unit. With a little care, by the time these 2 die you will know much more about what your battery power needs are. Then spend the money for true deep cycles if you do a lot of boondocking. BTW thanks for the SAMs club tip. I'll be heading there in the morning to see what they have left. Jay
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Old 01-11-2017, 09:49 PM   #22
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In the two battery photos you have shown, the RC in minutes may be the same but the internals are very different (note the different MCA numbers).

That means the internal battery resistance is also different and they will not charge/discharge in a balanced way.
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Old 01-11-2017, 10:01 PM   #23
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Great information again.

wow, those batteries are NOT cheap Lou! *LOL* But if they last 6 yrs+? Well worth the money indeed. Again, upfront costs could save a lot if you can afford to go that way. Since I "inherited" the Interstate with the new camper, I had to go with that. Just could NOT find anyone around here that carried Interstate and got tired of monkeying around with it.

When these two batteries die, I'm probably going to go with 6V Golf Cart batteries. I've heard nothing bad about them. Or? Hey, maybe a killer 12V like you pointed out Lou. Thanks all.
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Old 01-11-2017, 10:02 PM   #24
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Totally! Thanks.
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Old 01-12-2017, 01:23 AM   #25
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Your batteries will work just fine together with a difference in MCA of 15 amps.
MCA is the measurement of amps available at 32 degrees and CCA is the measurement of amps available at zero degrees.
The CCA and reserve capacity are the exactly the same so the batteries are basically identical in structure.
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Old 01-12-2017, 05:33 AM   #26
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Quote:
Originally Posted by Herk7769 View Post
CCA is cold cranking amps (0 degrees) and only useful for starting boat engines when cold out.
MCA is Marine Cranking Amps (32 degrees) and only useful for starting boat engines when slightly warmer.

The real number that is important on that cheap battery that pertains to your RV is the RC (Reserve Capacity). RC is the number of MINUTES that your fully charged battery will last at 80 degrees when discharged at 25 amps.

To convert RC to AmpHours (the measure that is important in storage batteries used in RVs) you need to convert by multiplying RC by 0.4167.

AH rating is based on the delivery of amps for 20 hours (the 20 hour rating); so a 100AH battery will deliver 5 amps for 20 hours. Discounting something called the Peukert Effect; at 20 amps your 100AH battery will last 5 hours; etc ...

Thus your Group 24 battery has 140 minutes x 0.4167 or 58.3 Amp Hours.

Most cheap OEM Group 24 batteries (like my DC-24 Dekas) have a 75AH rating.

A true deep cycle in Group 24 (like a Trojan - Trojan 24TMX Heavy Duty 12V Battery) will have 85 AH of capacity.

Same physical size and group, but radically different performance.
Many thanks for the information. Im not currently looking for a battery for my truck or my 5er but you certainly gave me the information I need when I begin looking for one!
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Old 01-12-2017, 11:52 AM   #27
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Excellent attachments.

Quote:
Originally Posted by Herk7769 View Post
If wired properly (current path resistance into and out of each battery is the same - see diagram) they should age together gracefully.

If wired with both charge/discharge wires on the same battery or different length interconnecting cables, the different inter-battery resistance will cause one battery to work harder than the other and fail first. The lower resistance battery will provide more of the load and recharge faster than the "slacker" on the battery with higher resistance.
I almost missed the two attachments! After reading those, it now makes much more sense to me. Thank you so much!
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Old 01-12-2017, 05:17 PM   #28
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Originally Posted by boondocking View Post
Your batteries will work just fine together with a difference in MCA of 15 amps.
MCA is the measurement of amps available at 32 degrees and CCA is the measurement of amps available at zero degrees.
The CCA and reserve capacity are the exactly the same so the batteries are basically identical in structure.
When discussing internal battery resistance, believe it or not, even very small differences in construction matter. Different manufacturers use thicker or thinner plates; various waffling patterns (or even no pattern); based on their particular designed purpose and manufacturing process in the same Group footprint.

"Basically the same" in this particular context is unfortunately meaningless.

Will this difference be a factor in the short run (year or so)?; probably not. However over the course of a few hundred charge/discharge cycles, one battery, lower in resistance, will be overworked and fail before the other.
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Old 01-12-2017, 05:54 PM   #29
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You can believe what you like, but I beg to differ.

The CCA of the two batteries is the same.
The Reserve Capacity is the same.
They are the same size/group..
The difference in MCA is 15 amps, which is a very small difference.

So they are basically the same and should function together without one failing sooner than the other.
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Old 01-14-2017, 05:24 PM   #30
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In batteries you sometimes get what you pay for, I bet that the Sam's battery will pull the Interstate battery down to its level. I don't think one will necessarily die before the other one but a cheap battery will pull a good battery down to its level. What I think you have is two new batteries but not being equal, those two batteries will equalize and I think you will end up with two Energizer batteries but I could be wrong. I brought four 6 volt batteries from Sam's one time and two were bad.


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Old 01-14-2017, 05:51 PM   #31
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If the two batteries last 2 or more years, that's not going to be a bad investment overall. I got the Sam's Energizer battery for $72.03 (tax and core charge). Later when both are beyond use, I'll go with 6V Golf Cart batteries. But? 2 yrs from now, battery technology could be way improved. I remain optimistic.
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Old 01-14-2017, 06:50 PM   #32
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I also purchased a trickle charge cord to run from the bedside out to the batteries for when we are plugged in..
Little confused by this statement. If you are referring to plugged in while camping, they should both be charged by the Converter in the RV when plugged in if wired correctly in parallel.
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Old 01-14-2017, 07:25 PM   #33
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Quote:
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If the two batteries last 2 or more years, that's not going to be a bad investment overall. I got the Sam's Energizer battery for $72.03 (tax and core charge). Later when both are beyond use, I'll go with 6V Golf Cart batteries. But? 2 yrs from now, battery technology could be way improved. I remain optimistic.

Sounds like a good deal to me and if taking care of they may last longer. I like Trojans 6 volt batteries but hey everybody is different, you buy what you like and what you can afford.


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Old 01-15-2017, 12:19 AM   #34
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Little confused by this statement. If you are referring to plugged in while camping, they should both be charged by the Converter in the RV when plugged in if wired correctly in parallel.
Flybob. I contacted the dealer where I bought the Rockwood Mini Lite 2019S. I asked if the house battery is also charged (trickle or float, whatever you want to call it) when I'm plugged into 30 amp service at an RV Park. They said yes, the house battery is being charged while I'm driving my truck AND when I'm plugged into 30 amp shore power at and RV campsite. So? I'm figuring, there must be some converter/inverter (sorry I'm ignorant on the terms) that is also charging the battery while plugged in to shore power. That was a sub statement to my earlier question about mixing brands of batteries on my camper.

So from all the comments I read, VERY much appreciated everyone, I have concluded that:

1. Since the batteries (Energizer & Interstate) are rated the same, Group 24, Marine/RV, CCA, RC, and with only one very small difference in MCA (15amps)
2. Both are very new, within months of purchase.
3. Both will be connected in parallel.

I should be good to go. "quote from Jodi Foster in CONTACT".
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Old 01-15-2017, 01:51 AM   #35
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When it comes time to replace one of the batteries I suggest you replace both with a pair of true deep cycle batteries, not marine (aka dual purpose) batteries. There are arguments for a pair of 6v in series and arguments in favor of the 12v parallel approach. (I do the latter but have other purposes for the batteries when not camping.) Whatever approach you choose, make sure they're deep cycle, not dual purpose.
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Old 01-15-2017, 07:06 AM   #36
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Battery life is best when some standards are used.

The 6v golf cart batt ( use a matched pair) will actually be the best choice for most folks .

The pair will have a good 20 hour rate, as there is less insulation between plates ( needed for 12v) and may weigh more , and its the lead that counts.

For long life the WLA (wet lead acid ) batt should be discharged less than 50% and then quickly recharged , at least to 100% , many batt mfg now go to about 110% for best recharge.

The question then becomes how do you know when 50% is gone and after recharge 100%+ is reached.

The answer is a SOC meter . SOC is "state of charge" , think of it as your batts gas gauge.

With tender loving care a set of house batts can get about 6 years of service , but the hard part is the 100%+ REFILL IF NOT AT A POWER SOURCE.

For dedicated boon dockers a good sized solar system is a great help, IF you don't mind parking out of the shade.

There are many SOC meters, Bogart makes a good not too expensive unit.

home - Bogart Engineering
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Old 01-15-2017, 09:10 AM   #37
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Free Education regarding RV electrical system: The 12volt Side of Life (Part 1)


BTW, the OP's "two different" batteries are probably the same as they are both made by Johnson controls.
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Old 01-15-2017, 09:43 AM   #38
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The pair will have a good 20 hour rate, as there is less insulation between plates ( needed for 12v) and may weigh more , and its the lead that counts.
I think you meant "less insulation overall between cells", leaving more room IN each cell for more lead. In a 12 volt battery, there are 6 cells that require case material (insulation) between each other. In a 6 volt battery there are only 3, thus more room in each cell for lead in the same footprint (though to be fair with less internal bracing that "wall" is thicker in a 6 volt battery for strength).

Between plates there is only electrolyte and a thin non-conductive but porous separator (called an envelope in this graphic).
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Old 01-15-2017, 02:41 PM   #39
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Yes more lead more amp hours.

In the past folks have broken open true deep cycle batts and have seen that the plates are usually shorter than in a start batt.

This is so any flaking off a plate will have room to fall and not short out plates.
Deep discharges and high recharge rates are hard on the batt set.

Start batts have no need for this as their very thin plates do not handle a deep discharge at all well.

Leave the dome light on a couple of times and a new start batt will be required .
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Old 01-17-2017, 03:39 AM   #40
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Install a battery switch w/ A or B. This will allow for age differences.....


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