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Old 07-30-2018, 01:33 AM   #1
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Lifeline amp hours

Hi all. My first post. Sorry for the stupidity of this question but I have a hard time with this stuff.

Ok here goes.

I understand that when two Lifeline GPL-4CT batteries are wired in series this creates 12v but the amp hours remain at 220. My question, with the understanding that you should only discharge a battery to 50%, is do I only have 110 amp hours at my disposal, or do I have the full 220? Thanks in advance for the clarification.
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Old 07-30-2018, 01:40 AM   #2
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Some (hopefully useful) Airstream videos here:
https://www.youtube.com/c/journeymanvideos
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Old 07-30-2018, 06:34 AM   #3
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Two twelve volt batteries in series gives you 24 volts. Two 12 volt batteries in parallel gives you 12 volts.
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Old 07-30-2018, 07:28 AM   #4
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some basic info>
https://www.batterystuff.com/kb/arti...-tutorial.html
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Old 07-30-2018, 07:43 AM   #5
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These are good batteries. The Lifelines are good for 1100 cycles if discharged to 50%. Interestingly, they are good for 500 cycles if discharged to 100%. That said, I think these can be taken down to 25-28% safely with little harm in an emergency. Do not do that with a standard 12v lead acid battery or you will kill it.

Milage may vary.
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Old 07-30-2018, 10:14 AM   #6
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We are talking about two 6-volt batteries here, per the OP, just to get everyone on the same page:

http://lifelinebatteries.com/product...eries/gpl-4ct/

https://www.amazon.com/Lifeline-Mari.../dp/B0029XJ1U6

FAQ: http://lifelinebatteries.com/faq-items/
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Old 07-30-2018, 10:21 AM   #7
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Quote:
Originally Posted by thiel View Post
110
Are you sure about this? I though Amp Hours were additive.

2 batteries x 220 Amp Hours ea. = 440 total Amp Hours x .5 discharge = 220 Amp Hours available above 50% discharge limit?

Thanks,

Peter

PS -- edit -- see later posts -- at 12-volts your 110 is probably correct? Sorry to be an electrical dunce!

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Old 07-30-2018, 10:25 AM   #8
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Quote:
Originally Posted by OTRA15 View Post
Are you sure about this? I though Amp Hours were additive.


2 batteries x 220 Amp Hours ea = 440 total Amp Hours x .5 discharge = 220 available?


Thanks,

Peter
Amp-hours are additive in parallel setups (2x 12v batteries in parallel still puts out only 12v but 2x the amp-hours.)

VOLTAGE is additive in series setups (2x 6v batteries in series put out 12v but at the same amp-hour capacity of one battery.)
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Old 07-30-2018, 10:39 AM   #9
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. . . OK . . . at 12 volts . . . [vs. 6]

Thanks, David.

"Sparky"


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Old 07-30-2018, 11:04 AM   #10
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Hi

The next layer to this onion is - how do you *know* you are at 50%?

If you are at 70F, there is a magic voltage on a resting battery that should equate to about 50% charge. Take the batteries up to hot (like full summer sun) or down to cold (like overnight in the fall) and those voltages change by a half volt or more. Now what you *think* is 50% is either much higher or much lower capacity.

One answer would be to have a chart and a temperature probe. Look up the temperature each time you guess the battery's state .... any takers on that idea? ... nope didn't think so

Another answer is to put on a charge monitor that measures current in and out of the battery. That will give you a much more accurate idea of where you are. Without that, it's very hard to *know* how kind ( or nasty) you are treating your batteries.

Next down this road, the 220 AH number isn't quite as definite as we make it out to be. In most cases for lead acid's it's based on a 20 hour discharge rate. Crank things up to a higher rate and the capacity plummets. Get the batteries cold and the capacity drops a lot (independent of the magic voltages changing).

Charging the batteries isn't quite as quick as we like to think it is. Getting a lead acid up to full charge takes a *long* time. You get to 80% fairly quickly, the other 20% .... wait a day ... If you are only running down to 50%, the distance from 50 to 80 is very different than 50 to 100.

So yes, it's not simple. There are a lot of twists and turns. It's amazingly easy to think you are babying your batteries when you are being pretty brutal to them.

Bob
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Old 07-30-2018, 11:06 AM   #11
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Originally Posted by OTRA15 View Post
. . . OK . . . at 12 volts . . . [vs. 6]

Thanks, David.

"Sparky"


Right... it's a conservation of energy thing. The ENERGY measurement is watt-hours:


6V batteries have about 220 amp-hours at 6V, so each battery stores about 220x6 = 1320 watt-hours. So, either way you hook the batteries up, you'll get a total of 2640 watt-hours:

6v x (220+220) amp-hours = 2640 watt-hours (parallel, at 6v)
(6v + 6v) x 220 amp-hours = 2640 watt-hours (series, at 12v)

And no laws of physics were violated in this demonstration.
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Old 07-30-2018, 11:25 AM   #12
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Great question. I keep pondering what is the best battery replacement for our needs. Our Interstates provide about 70 amp-hours at 50% and cost around $150 for two batteries. The Lifeline GPL-4CT are around $650-$700 for two and provide about 110 amp-hours at 50%. So more than four times the cost for 57% increase in capacity. It may seem like not a great trade but the 57% increase in capacity satisfies your needs then it is a great improvement that’s $4000+ less than going to Lithium. Arguably the Lifelines are a better battery than the Interstates. If you are going with solar there are other advantages to going with Lithium that should be considered in the equation. The two Lifelines are also 40# heavier than the Interstates so if tongue weight and/or TV payload is an issue, then you have to reconsider the 12v option or Lithium which is much lighter.

Summertime is not an issue but we spent last winter in the Southwest and were continually monitoring the state of our Interstates, even after I replaced them with new. Using our furnace (fan motor) really sucks the life out of them and we supplemented our heat with a Little Buddy which has its own issues ranging from moisture to singing our dog’s tail. Even while living like meisers we were at 50% by bedtime. Finding the right cost-effective battery solution is a tough one.
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Old 07-30-2018, 11:31 AM   #13
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Hi

..... ummm ..... errrr .....

Modern lithium's with built in BMS systems run a bit under $1,000 delivered on a 100AH battery. That gives you 100AH of *usable* capacity. Lithium's work a bit differently than lead acid's. You will be getting 3 to 5X the number of charge cycles on them, even at 100% discharge vs lead acid. All that going to make it pretty tough to cost justify a similar usable capacity lead acid setup at $650 to $700.

Bob
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Old 07-30-2018, 11:52 AM   #14
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Quote:
Originally Posted by uncle_bob View Post
Hi

..... ummm ..... errrr .....

Modern lithium's with built in BMS systems run a bit under $1,000 delivered on a 100AH battery. That gives you 100AH of *usable* capacity. Lithium's work a bit differently than lead acid's. You will be getting 3 to 5X the number of charge cycles on them, even at 100% discharge vs lead acid. All that going to make it pretty tough to cost justify a similar usable capacity lead acid setup at $650 to $700.

Bob
Ahh dang, I need another cup of coffee! Iíve recently been looking at 300 and 400 amp-hour Lithiumís. For equivalent capacity batteries the price comparison is much more favorable. Now, whereís my creamer...😎
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Old 07-30-2018, 12:09 PM   #15
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Hi

The point often made - you don't *have* to go up to the fancy 6V's. You *can* stick with whatever is on sale this week at the local retail outlet. In that case, the price delta is quite a bit greater.

Another point - people rarely stop at the "just buy one" stage. There's room for two Lithium's .... buy two . While you are at it, buy this and buy that to make things even better. It is *very* easy to spiral out of control on a Lithium project .... I have data on this .... ( and there's exhaustive details in several threads here and there ....)

Bob
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Old 07-30-2018, 12:43 PM   #16
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Yes, bob, plenty of lithium threads, but the reason we never considered them is because you can't charge them in below-freezing weather, right? Seems like a real weak link in the chain for active trailer campers who may end up dry camping in their aluminum tent in cold weather.

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Old 07-30-2018, 02:15 PM   #17
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Thanks for clearing that up for me Thiel and to everyone else who responded. I donít even own an Airstream yet but Iím already worried about battery management.

By the end of the year Iíll have put in an order for my tow vehicle. The plan then is to purchase an Airstream within 18 months. The model I have chosen is the 23cbb Flying Cloud. We are a family of four with two children aged 7 & 1.

Iíve taken our 7 year old camping many times since the age of 4. Camped in Yosemite, Lassen, Mojave, Joshua Tree, Death Valley, Craters Of The Moon, Yellowstone, Grand Canyon, Bryce Canyon , Grand Teton, along the coast of California and amongst the redwood trees. The wife doesnít like to camp AT ALL.

She however very much likes the idea of an Airstream, as I do. We would like to get out there before our 7 year thinks we are lame.

After looking at many other trailers we knew the only one for us would be an Airstream. Many of the other trailers look tacky and the interiors match a Sears catalogue from 1977. Iím originally from Europe and the difference in trailer quality and aesthetics is astounding. Donít get me wrong there is a lot of crap over there as well but in general they seem like they where designed and built for this century.

But then you have Airstream. In my book it doesnít get any better. Ideally I always like to buy right the first time, even if I have to wait longer for financial reasons.

Which brings me back to batteries. My Walter Mitty side would like to pick up our trailer and rush over to AMSolar and have them install 4 solar panels and 300ah of lithium but at 6g or 7g plus labor ( would that double the price?) Iím not sure that would be feasible in the beginning unless I sell an organ. On the other hand I can imagine the look the boss would give me after we have been airstreaming it without hookups for 4 days and we canít turn the furnace on because we have no battery. Her eyes would say ďwe spent all this money and we have no power in this tin canĒ.

All first world problems for sure and Iím thankful that we can even consider buying an Airstream in the near future. One thing at a time. Sorry for the ramble.
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Old 07-30-2018, 02:43 PM   #18
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Yes, bob, plenty of lithium threads, but the reason we never considered them is because you can't charge them in below-freezing weather, right? Seems like a real weak link in the chain for active trailer campers who may end up dry camping in their aluminum tent in cold weather.

Hi

Charging with the battery below freezing is cut out by the BMS. Discharge below some lower temperature is also cut out. We went with two batteries "indoors" and two in the battery compartment to minimize those issues.

Any battery system is going to be "challenged" at sub-freezing temperatures. Capacity of all of them drops in the cold. Lithiums drop a bit less than lead acid's. I'm not quite sure of a "pure battery" camping scenario where that would be a big deal for me.

Of course, the plumbing system on your typical airstream also has cold issues. My belief is that the same "sub freezing for days" that will stop you camping due to water issues is the same thing that will get you in trouble with charging lithium's. Dipping below 32 at night and warming up in the day ... that works for both systems.

If you store the trailer in the winter where it gets *really* cold, you would need to pull the lithium's in the winter. They are lighter than lead acid's so slightly less hassle. If it gets cold enough to pull lithium's, you likely would be doing the same for lead acid's. They freeze / rupture if it's cold enough. Just how cold depends a lot on their state of charge.

No magic bullet, it's more things to consider when it's cold ....

My conclusion was that the hassle of condensation, worrying about freezing, setting up to winterize ..... all that will stop my adventuring at a point before the lithiums would become a limiter. Storage wise, in enclosed storage where I live .... they can sit out all winter .... The one year in twenty when it gets crazy cold ... I'll go pull them.

Bob
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Old 07-30-2018, 03:18 PM   #19
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Thanks. Our Airstream is stored out back all winter, and the batteries are kept charged, with careful monitoring. Thus the plain old OEM lead acids work for us, even in very cold weather. Just like car batteries do fine.

Your earlier point about getting new ones on sale is well taken.

If it ain’t broken, keep it simple, Stu . . .

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Old 07-30-2018, 03:24 PM   #20
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Hi

If you store the trailer in the winter where it gets *really* cold, you would need to pull the lithium's in the winter. They are lighter than lead acid's so slightly less hassle. If it gets cold enough to pull lithium's, you likely would be doing the same for lead acid's. They freeze / rupture if it's cold enough. Just how cold depends a lot on their state of charge.

Bob
I never pull my batteries and the last set of Lifelines lasted 9 years. I expect this set to last the same. I can't be bothered to pull batteries and don't expect that lithium will be with the cold weather where I live. If I have to worry about the temperature then I'm out.

The 50% rule isn't a big deal since my circuit is designed to handle it and my solar system can recharge it by mid afternoon. Even after 4 days of solid rain it's not an issue. Just size your system according to your needs.

At least my lead acid batteries can be recycled and don't involve child labour. Let's me sleep at night for those with a conscience.
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