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School me on batteries


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Right now we have 4 6 volt house batteries, I'm not sure what the amp hours on them are, I do know they are only a year old.

Moon asked me today if we could replace the four 6 volts with four 12 volts. I had to tell her that I am just not sure.

I will be the first person to tell you that electricity scares the living hell out of me (I stuck a fork in an outlet when I was 3, it left a lasting impression) and tampering with anything to do with it makes me nervous....

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First test is whether you have room for twice your current footprint of the 4-6 volts? Next, is the coach chassis capable of carrying the extra weight where your 6 volts are now? Last, do you have an inverter; what amp size?

 

Jerry

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At only a year old is there a reason you are considering changing them out? They are barely broken in. Are you trying to add capacity? Personally, I would go with 6 x 6v cells rather than going with 4 x 12v. Of course... I don't know which 12v's you are considering buying. Like Jerry said though.. 12v'rs will take up quite a bit more floor space. Weights should be fairly comperable.

 

That being said, I wouldn't just add 2 new 6v cells to my existing bank. I would do a complete changeout.

 

I would say too though that not all 6v "deep cycle" batteries are created equal.

 

Knowing exactly what type, brand, and ah capacity of your current bank would be helpful.

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For most practical purposes, lead battery tech is a very mature entity. What your looking for is amp hours at 12 volts. 4-6 volts @ 200AH in series / parallel is going to give you 400 AH @ 12 volts (probably what you have in there now). 4 - 12 volts @ 100 AH is going to give you 400 AH.

 

Power for lbs / volume will be about the same. As Yarome says in #3 really need more info. / what your trying to do.

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I happen to prefer to use paired, 6V batteries, but as others have said, you have about the same either way, depending upon just what 6V you have now. As Bill says the technology is pretty well developed and isn't changing a lot at present although other battery technology is likely soon going to replace the flooded cells that you have now, it has not yet done so and for most the cost of changing is not warranted.

 

To give you a rough idea of what we are talking of, if you look at your batteries, the top of a battery has one cap for each battery cell. A 6V battery has three caps, indicating 3 separate cells while a 12V battery has 6 caps which indicates 6 separate cells, but of roughly half the size. In a flooded cell battery the physical size is somewhat indicative of the capacity. In any such battery you get approximately 2V of power for each cell that is connected in series. The 6V battery is that because the 3 cells are connected to add up to total 6V while the 12V battery has 6 smaller cells that connect to add up to 12V. When you have 6V batteries in an RV they are wired to connect 2 batteries in series pairs, making then essentially into one battery that is physically in two battery cases. The means that effectively you now have 4 batteries that are connected in pairs to add up to the equal of 2 very large 12V batteries. The two pairs are like the tank size and mean the quantity of electrical power they contain.

 

If we ignore the more technical design parameters and electrical theory issues, with your batteries you get an amount of power that is roughly based upon the space the batteries occupied, much like a gas tank has a number of gallons of fuel depending upon it's physical size. For most of us, the difference in actual use between 4 batteries of 6V that are connected in series pairs will get very nearly the same amount of electrical power as would 4 smaller 12V batteries that are connected in parallel. If we assume that all batteries are in about the same condition and quality, they have very close to the same capacity.

 

You will see many very long threads discussing the value of one over the other, but for the vast majority of owners it has only a very small impact. We who are electrically educated love to debate the design differences, but the user seldom sees enough difference to justify changing.

 

Your question makes me wonder if you are running short of battery power? That makes me wonder if you check your battery electrolyte levels regularly and add distilled water to them to keep them at proper level? Batteries should last for at least 3 years if they are properly maintained and not overly discharged.

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Yo Bear, you ask "if we could replace the four 6 volts with four 12 volts"

 

ANSWER IS DEFINITELY YES

 

Provided you have the physical space and can handle the weight (probably can if you can handle what you have)

 

CONSIDERATIONS:

 

1) If energy storage (total amp hours at 12 volts for RV use) capacity is a concern (sure is for me I dry camp a lot) consider this. Batteries store energy and the more energy in Amp Hours stored the more you can power loads before the batteries need to be recharged..........

 

In Series voltage is additive but Amp Hours or CCA is NOT. Two six volt batteries, each of say 200 amp hours, in series still yields only 200 amp hours of stored

energy, but at 12 volts. You have 12 volts BUT THE AMP HOURS OF STORED ENERGY IS NO GREATER THEN ONE BATTERY

 

In Parallel Voltage stays the same but Amp Hours and CCA DOES ADD. Two 12 volt batteries in parallel, each of 200 Amp Hours, yields 400 Amp Hours at 12 volts

 

2) WHY CHANGE if your batteries are good, its pretty expensive to change them UNLESS you just absolutely MUST have more Amp Hours of energy storage

 

NOTE: You have to compare apples to apple and oranges to oranges here. 6 Volt true deep cycle golf cart batteries are fairly common and available and reasonably priced. If you go with 12 volts THEY DO MAKE 12 VOLT TRUE DEEP CYCLE BATTERIES that are pretty much the same quality and type and design as their 6 volt counterparts. HOWEVER a so called and sold as RV/Marine Battery IS NOT the same as what I call a true deep cycle golf cart battery, they are a sort of quasi or semi deep cycle battery. For long slow typically lower current DEEP discharges like in an RV dry camped, I highly recommend a true deep cycle golf cart type of battery over a semi deep cycle sold as RV/Marine 12 volt batteries sold at Wally World.

 

 

SUMMARY yes you can change, but why??????? Unless you must have more amp hours and if so you have TO MAKE A WISE AND SIMILAR COMPARISON. If you trade out 6 volt true deep cycle batteries Id use true deep cycle 12 volt batteries (Triojan and others make them) instead of RV/Marine AND YOU HAVE TO LOOK AT TOTAL AMP HOURS. All batteries are not created equal and those 12 volt true deep cycle aren't cheap.

 

I currently have four six volt true deep cycle golf cart batteries in series/parallel which totals 460 Amp Hours. When they ever crap out if I want more energy I may upgrade to say Trojan T-125 (bigger then the classic T-105) but I doubt I will go the 12 volt route, Depends on cost and amp hours available at the time but the 6 volt (like T-105) are so much more common and readily available then 12 volt true deep cycle are. Shops around here stock T-105 but if you ask for T-125 or 12 volt THEY LOOK AT YOU FUNNY LOL have to order them !!!!!!!!!!!!

 

Other considerations are AGM like Optima or Lifeline etc, but I will let others go down that road

 

John T

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There are different types of lead acid batteries too. If your batteries have removable caps that allow you to add water then they are called FLAs (flooded lead acid batteries) This are the most common type. It requires monthly checking the water levels and filling with distilled water if necessary. If you forget and the plates become exposed to the air as the water evaporates then the batteries will sulfate and suffer irreversible damage. Sealed maintenance free AGM (absorbed glass mat) batteries are available, and though convenient thy cost 2-3 times the price of FLAs. Their advantages other than never needing water) are that they outgas much less than FLAs so don't typically need to b in a vented battery box and can be put in relatively inaccessible areas in odd positions. There is also gel cell batteries but they are not used much anymore. The thing to remember about gel cells is that though they have similar characteristics to AGMs they need different charging rates and charge voltage profiles. Remember to choose a deep cycle battery as opposed to a starting battery or even a hybrid "marine or RV battery," for longer life and deeper discharge cycles.

 

Chip

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PS in my post above I mentioned typical 6 volt true deep cycle golf cart FLA batteries and talked about a range of maybe 200 to 230 Amp Hours. If you shop and compare 12 volt true deep cycle batteries (made but less common) you will see DIFFERENT Amp Hour ratings on those units, so just dont forget when it comes to figuring your total amp hours of energy storage (the purpose of your house batteries) to take all that into account and what I told you about how series and parallel configurations add together. Apples to Apples and oranges to oranges remember.



John T


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She was looking at trying to get more amp hours. I pointed out today that what we really should be looking at is supplemental power such as solar and wind. She's always liked the idea of wind power, so next weekend we're going to go check out a 600 watt wind turbine at Frys.....Expect more questions.... :)

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Bear and Moon, you state as I assumed "She was looking at trying to get more amp hours."

 

All you have to do is compute the total amp hours you have now (series parallel same as I have, mine total 460 AH) at 12 volts, and if you go with four new 12 volt batteries all connected in parallel, the Amp Hours is the sum of the four individual 12 volt batteries AH's. An easy calculation. Of course, I still advise true deep cycle golf cart type of batteries (Trojan makes them 12 volt but they aren't cheap) NOT semi deep cycle like the cheaper RV/Marine batteries sold at Wally World. The 6 volt are so readily available while the 12 volt (true deep cycle) may have to be special ordered you know.

 

Havin fun yet???

 

John T

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Just a comment which is based on my experience and my opinion.

 

You want to fully utilize solar capabilities in an RV before considering installation of wind generation equipment. That is, unless you are in a fixed location with special circumstances.

 

I would never recommend putting on wind first. Do solar first, then supplement with wind, as necessary. IF you find you are in areas that provide enough wind to make it worthwhile.

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You may not be getting fully charged batteries ( I assume short life is the reason for your looking for a plan "B".) Be sure that you have a multistage charger to give the batteries the best charge they can take.

 

I had to replace the 2 house batteries when I bought my used MH. a few months later I discovered that my converter was one of the older dumb ones but was able to upgrade with a charge wizard. after 2 full days charging with the upgraded converter it FINALLY came off the 14.8 VDC charge and dropped to the normal 13.6. it only took 2 months to degrade the new batteries. check your converter!

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Stuck my finger in an open lamp socket while holding onto the metal frame of my crib at 4 years of age. Have not trusted electrcicty since.

 

Now that there is funny. :lol: I had my first brush with electricity at age 8. It was an hour long drive home in a thunderstorm. 15 minutes in, our car hood gets hit with lightening and blows out the radio and dash lights. Mama yells back, "don't touch anything metal! It can kill you!!". The car kept going but it was the longest 45 minutes of my life staring down at the metal clasp of my seat-belt over my lap and just knowing I was going to die. :blink:

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Bear and Moon

 

Stuck my finger in an open lamp socket while holding onto the metal frame of my crib at 4 years of age. Have not trusted electrcicty since.

Yeah, I did the same thing with a Bobby-Pin and a wall outlet at three years old. I was always more advanced than my peers, from what I'm told...

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With 4 normal sized golf cart batteries you have about 420 amp hours.

You gain nothing switching to 12 volt batteries and will likely lose a few amp hours if size is the same.

Golf cart batteries are true deep cycle batteries. That means they are built to be discharged and recharged. While there are deep cycle 12 volt batteries, most are what they call both, starting and deep cycle. Not perfect for either.

We boondock often with our RV but our real use of batteries is on our boat. We anchor out about 100 days a year and have for the past 30 years. We live on batteries, using solar which is limited by space and direction on a boat and a generator. The last time we had shore power during this time was 9 years ago.

Every year I look for ways to improve and lessen generator use.

Here is some of the things I have found.

If you live off grid, every amp hour is important. Look at the energy use of everything you use. A tv for example will have a big difference by mfg for the same size tv.

Have a means of monitoring your house batteries. This is the most important thing I can suggest if you want long life from your batteries.

No battery can survive being deeply discharged. That includes deep cycle batteries. They can survive longer but any battery should not be discharged more than 50% if you want long life. I expect to get at least 8 years on my batteries and have gone longer in my motorhome. I change them more often in our boat because where I boat it is remote and the ability to replace them is very limited.

You need to monitor your batteries.

Something like this: http://www.anchorexpress.com/xantrex-linklite-battery-monitor-84-2030-00

It monitors by using amp hours. You tell it your amp hour capacity of your battery bank (in this case 420 amps) and its automatic from there.

You fully charge your batteries. It records the amps use and the amps charged. it shows how many amp hours you have left so recharging when you get 50% discharged is easy. It also tells you what your amp hour usage is at any given moment. It will also tell your voltage.

Voltage to determine your battery condition is pretty useless when the batteries are in use. For it to be meaningful the batteries have to be at rest for several hours. That means no charge or discharge. Impossible when you are living in your rig.

Want to test that? Put a volt meter on your battery bank, note the voltage. Now turn something on like a tv or even a light. Note the voltage drop. Your battery didn't lose all that voltage immediately and the reading is useless to determine the true battery condition.

Being able to see the actual amp hour usage at any given time will show you what the actual use is on anything you leave on. And after a while you will know what the normal usage is and you will know if something is on drawing amps.

In attrition to being the best battery to use in a house bank, it will be the cheapest also. The best bang for your buck. Sams or Costco have good prices. I have used them for many years. If you happen to live near a Rural King store they often have them on sale for $69. They are Interstate batteries with their name on them. http://www.ruralking.com/find-store/

For many years we had a boat in Michigan and Florida. Also a motorhome. So we have been doing this on 3 rigs for a long time. I am still in the learning mode and every year try to improve our battery performance.

We do not live without the comforts. We just practice good energy management. Not a bad thing to do even at home.

On our boat and RV, we have an inverter/charger. All are now a 2000W inverter with a 100 amp charger. I almost never use the inverter for anything that draws a lot of amps because it takes longer using the genny to charge than it does to simply start the genny. It also charges the battery while doing so which is necessary most days anyway. May make coffee in the morning if we are anchored near another boat so the genny doesn't bother them.

Having a large charger is important if you want to limit the genny time.

While I have a large genny on the boat and motorhome a Honda EU 2000 will run the charger if nothing else is on. You can also get a smaller inverter/charger. A 1000 inverter with a 50 amp charger is available.

I have a Yamaha 2400 amp generator as backup on the boat. It has just enough more capacity to easily run the 100 amp charger and other small things. It is a bit heavier than the Honda 2000 but is as quiet as the Honda. I have had good success with both and still have my Honda.

Long winded I know but this isn't a simple subject and no one thing will answer all the questions and solve all the problems.

Personally we live aboard with 4 golf cart batteries on our boat. We have a full size refrigerator that does not run on gas. It runs on batteries or 120 volt power all the time. I never use the 110 volt side because when the genny is running the charger is supplying the voltage to the batteries. We have a 32 inch tv with satellite reception. It is our biggest draw. Even more then the fridge. The RV is better for battery management because the fridge runs on gas when off grid.

With no sun we still only need to run the genny a max of 2 hours a day and never discharge the house bank below 50%.

One other thing I do to limit genny time is never try to fully charge the batteries. Any good charger cuts back when the batteries are about 90% full. At that point the generator isn't doing much to charge your batteries and I shut it down. You see all of this on the Link. No guess work involved.

Hope this helps.

I can also adjust my charger to charge less if necessary. I use Xantrex inverter/charger but others are available. Some have the Link system built in.

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Doug

 

Thanks for an excellent writeup. An lot of folks think that they can discharge their lead acid batteries far below 50% SOC and wonder why the battery suite fails. We have sufficient solar and LFP battery suite so that we have not used genny except to make sure it works and only hooked into line power once in two years. Power management is necessary when boondocking.

Reed and Elaine

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Jack Mayer's advice to maximize your solar before moving to wind is good advice. I've done both solar and wind and solar is far more desirable unless you like noise and vibration. Wind generators do work at night and in the shade but lots of trees block the wind as well as the sun.; and at night, of course, most of us want to sleep.

 

If you have enough room for all the solar you need then, by all means, don't even look at wind. It will require a lot more maintenance and attention. Just having a heavy load on a long lever, all by itself, can present issues.

 

I'll stack solar panels on the bed when I'm traveling and arrange them around my rig on the ground long before I'd move to wind again.

 

YMMV, of course, :D

 

WDR

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Doug

 

Thanks for an excellent writeup. An lot of folks think that they can discharge their lead acid batteries far below 50% SOC and wonder why the battery suite fails. We have sufficient solar and LFP battery suite so that we have not used genny except to make sure it works and only hooked into line power once in two years. Power management is necessary when boondocking.

Reed and Elaine

Thank you.

I hope to get to the point on our boat you now enjoy. A boat is different at anchor you are at the mercy of the wind and its direction. It is difficult to change the panels so you are faced with them flat on the deck. Ideal for overhead sun but not so good otherwise. I have seen 35 amps in perfect conditions but that is rare.

I have added 50% more panels that will be on an angle so I have to be pointed in the proper direction for them to be much use. I have noticed I am pointed East in the morning and West in the afternoon a good share of the time. Ideal when that happens.

Also I increased the house bank by 50%. I have noticed many days I have a complete charge and the solar cuts back to avoid overcharging. I hope to capture this wasted amps.

As I mentioned I am always trying to improve. That is this years attempt. Another thing I have noticed in the area I boat, June and July provides more amps of solar than Aug. and Sept. There is a slight haze in the air that you wouldn't notice but the solar panels do.

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I have noticed many days I have a complete charge and the solar cuts back to avoid overcharging. I hope to capture this wasted amps.

 

This is the balance point I look for with my solar system; fully charged by around mid-day/noon. Amps after that can be used for charging up the trolling motor battery (if we're camped on a lake) or my scooter batteries... laptops, tablets, your next door neighbor (!)... :)

 

This gives the system extra time in marginal conditions to get the battery bank up to full charge; on those days I might not let the neighbor plug his charger into my system. :P

 

WDR

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Solar isn't used extensively in the marine environment. More on sailboats than powerboats because of room restraints and the inability to direct the panels to the sun. There is a lot more to learn from the RV environment.

It is surprising how much in common both have to each other.

Doing both I do see this.

Good discussion.

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dmcb

 

Great post good basic info, FWIW and to add just a bit heres my take:

 

My four 6 Volt Golf Cart Batteries total 460 AH, you can have more or less depending on the choice of batteries of course. The 6 volt Trojan family range from the classic T-105 to T-125 and I think they also make a T-145, each of which has a higher AH rating. In general, the more lead and more acid corresponds to more weight and more AH. I was at Rural King the other day and checked out those $89 batteries and as I best recall (slept since lol) and as one would expect, their AH rating was less then the more expensive batteries listed above, like the old saying, you get what you pay for. Now if they had the AH rating of say the Trojan T-125 or equivalent, but were only $89, then Id take a closer look at them lol. I forget their exact rating, but as I best recall it was less then the numbers I quoted above.

 

The so called RV/Marine 12 volt batteries sold at Wally World are semi or quasi deep cycle as they are designed to be able to start a hefty outboard (like a conventional auto starting battery) PLUS power say a Trolling Motor which is more typical of a Deep Cycle Battery. For typical slower less amp deep draw down loads such as in an RV, I recommend a true Deep Cycle battery instead of the Combination RV/Marine quasi deep cycle. Trojan makes a true deep cycle 12 volt battery (have to order) but they are expensive and far less common and typical then a 6 volt deep cycle golf cart battery which are so readily available. That's why I would opt for a 6 volt instead of going the 12 volt route, even though AH's are additive when you parallel batteries unlike the 6 volt series connection.

 

Those Xantrex Battery Monitors are priced all over the range from like $169 to over $300

 

http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=xantrex+battery+monitor&_pgn=2&_skc=50&rt=nc

 

 

I also don't like to go over any 50% battery discharge before I recharge them. A Deep Cycle only has a certain number of "Life Cycles" and if its kept fairly well charged versus a deep draw down followed by a recharge (a Life Cycle) you aren't really using up so many of its rated Life Cycles which extends its lifetime. I figure if you have adequate solar capacity, a smart 3/4 stage Solar Charge Controller, and a smart 120 VAC 3/4 stage charger (what I have), and run the Equalization or Desulphation Cycles as required, you don't actually use up many of the batterys Life Cycles and you may get 7 to 10 years out of a set??? My buddy got like 8 years.

 

Indeed if you correctly angle the solar panels WOW you can see the meter increase dramatically. Although I have the ability to tilt mine, I have adequate capacity so I don't usually have to fool with it.

 

Very fun chat

 

John T

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you may get 7 to 10 years out of a set??? My buddy got like 8 years.

 

There is a major difference between your $90 deep cycles and your $130+ deep cycles. Even with similar ah capacities. If you take them apart you might see that many of the less expensive types use a rather thin pressed mesh plate rather than the thicker solid plates. But neither here nor there.. with a good quality deep cycle battery 7-10 years is not at all unreasonable. My first set of T-105's I ran for 11 years and got passed along to the new owner... my second set of T-105's I ran for 9 years and as of New Years they were still in use 2 1/2 years after the fact. With the lifeline AGM's I'm running now I would expect to get at least 10 years out of them. We'll see....

 

I don't have any scientific proof, but my perception is that true deep cycle batteries tend to last longer when they are regularly exercised. Throughout... mine have been used pretty much on a daily basis and my target discharge SOC has always been around 80% between charge cycles. 70% every now and again doesn't bother me, but I could probably count on one hand the number of times my banks have ever gotten down to 50%.

 

Not to say that the $90 jobs aren't worthwhile. They have their place. For someone that only used them a few times a year, the investment is minimal, they don't have to "baby" them, and if they get 3-5 seasons out of them it doesn't hurt much if they give up the ghost. In the meantime, they have some pretty decent ah's on tap. That's a win in my book.

 

For full timers though, I think most would be pretty disappointed if they are expecting to get true deep cycle performance and life cycles out of the box store GC batteries. I wouldn't be surprised if there was a notable decrease in performance after 3 years and wouldn't expect them to make it past 5. You really DO get what you pay for, and in the long haul, you'll get much more bang for your buck springing for the Trojans or other similar. Ie. $130 for a Trojan @ 10 years vs. $90 for a box store GC @ most 5 years X2.

 

JMHO

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Rural King does have the larger GC batteries. They are the same in length and width but higher. Of course they weigh more and cost more.

For me in all the years I have been using GC batteries, I have always bought the cheaper ones, usually at Sams. I have mentioned my life with them.

For years I used them in a boat in Michigan, a boat in Florida, and my motorhome.

I do not use them full time and maybe they wouldn't last like they do for me the way I use them.

Another thing I have noticed about batteries. And this flies in the face of expert opinions.

I will take my boat again because it sits the longest with out charging. I fully charge and disconnect the battery cable. It sits for over 8 months every year without a charge and they are always charged more than 50% when I return. When I have checked they have been about 75% but I seldom check. They are 9 years old this year and still in good condition but its time to change. Also I am adding 2 more and all batteries should be changed at the same time.

The truck I leave in Michigan sits at least 7 months with no charge. Temps here this winter reached 40 below zero. Diesel truck started right up. Batteries in my previous truck lasted 9 years. It was also a diesel. It started right up in the spring. I left it while on the boat and they were dead and would not take a charge.

My Ford diesel in Florida got 11 years with the same treatment. No charge and sit 7 months. It started when I returned in the fall but failed one day. It started hard once and wouldn't start again. I would usually change them before they died but these lasted so long I wanted to see just how long.

Btw, if your counting months, the difference is motorhome use when I am not home either place. These times vary a couple of weeks year by year.

I don't remove them from anything either. So much for removing and storing in a warm place.

If a battery is charged cold won't hurt them. If you use them when its cold you won't get the performance from them but the cold when stored will not harm them.

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