6v battery life/charging concerns

[ibosket]

In August 2018 I had my Airstream dealer replace my stock twin 12V wet batteries with twin 6V AGM, convinced that this would increase long-term battery life for dry camping (2017 FC 23FB). The original 12V capacity was waning quickly under normal use, and initially the 6V was significantly greater. However, after one year the 6Vs have also begun to lose capacity quickly and makes me question the $700.00 pricetag. While traveling without the Airstream in May of this year, we left the trailer in our driveway with the fully-charged batteries in storage mode for about six weeks. When we returned the batteries were completely discharged - nothing registered on the monitor when turned back on. Since then they seem to have lost even more capacity. I understand that fully discharging these batteries is bad for them, but thought that fairly new units were supposed to hold their charge longer without use. We tend to be pretty careful with usage while dry camping, making efforts to sustain battery life - but we seem to be right back in the same place we were at with the 12V. Would a better converter help with this? Are we overcharging our batteries while hooked up? Some advice would be appreciated. Thank you.

[GMFL]

$700.00 is a lot of cheddar for (2) 6volt AMG batteries. Storage mode does not remove all loads form the batteries. Things like CO/Propane detectors still draw power. 6 weeks is a long time to leave batteries unattended and the total discharge probably did significant damage.
A 4stage converter charger would do a GREAT job of maintaining and keeping your batteries healthy.

[jftompkins]

Originally Posted by ibosket

In August 2018 I had my Airstream dealer replace my stock twin 12V wet batteries with twin 6V AGM, convinced that this would increase long-term battery life for dry camping (2017 FC 23FB). The original 12V capacity was waning quickly under normal use, and initially the 6V was significantly greater. However, after one year the 6Vs have also begun to lose capacity quickly and makes me question the $700.00 pricetag. While traveling without the Airstream in May of this year, we left the trailer in our driveway with the fully-charged batteries in storage mode for about six weeks. When we returned the batteries were completely discharged - nothing registered on the monitor when turned back on. Since then they seem to have lost even more capacity. I understand that fully discharging these batteries is bad for them, but thought that fairly new units were supposed to hold their charge longer without use. We tend to be pretty careful with usage while dry camping, making efforts to sustain battery life - but we seem to be right back in the same place we were at with the 12V. Would a better converter help with this? Are we overcharging our batteries while hooked up? Some advice would be appreciated. Thank you.

A few thoughts on my 2017FC22FB ...Am estimating based on my 6V AGM - you have a total 220 AH (110 Ah useable). As stated above the propane detector draws amps in Store at about .1 amps (my guess-estimate) or about 2.4 Ah/day x 42 days = 101 Ah just for detector. There may be a few other parasitic loads along with batt loss of charge in storage ( AGM better than wet cell)....so with another .1amp somewhere you could go to 0% over 6 weeks. Agree on the 4 stage converter (Which I did as well PD4655VL) - plugged in to maintain to float charge. I have been using a 5 Watt solar maintainer to protect batt in storage (I put a on/off switch on propane detector - unhook hoses in storage for safety) to slow the draw down. As some have stated a batt cutoff switch a good option to solve parasitic loads.

[uncle_bob]

Hi

First off, there is nothing magic about 6V vs 12V batteries. The only basic change you get is maybe 10% more capacity. Indeed specific 6V batteries from specific manufacturers can do a pretty good job if properly cared for. Trojan T-105's are one example. They are flooded cells so they do need attention ....

Simply put, a 220AH battery will out last a 200AH (or 180AH) battery by a little bit. Few of us measure battery usage accurately enough to see a 10% or 20% improvement. I certainly would not pay $700 for a 20% improvement.

Often what happens is people go from not paying any attention at all to paying a lot of attention to their batteries. Watching how your batteries are used (and caring for them) *does* make a big improvement in how long they last.

Price wise AGM vs flooded has always been a big debate. AGM eliminates water loss (sort of) and does indeed eliminate stratification in the cell. Both issues *can* be taken care of on a flooded cell. At $700 for a 110AH (usable) battery set, you are essentially at the same cost as a lithium battery with almost the same usable capacity. I don't know of anybody who would call lithium batteries cheap ....

Take a lead acid (any type) down to zero and leave it there for weeks .... not a good idea. I suspect that there were other events that also took the battery into "no go" land. As noted above, you need to understand the parasitic loads on the battery when in storage.

When operating off grid, you need to understand the active loads you are putting on the battery. If you are relying on battery voltage as an indicator of charge level, it's not a simple 1:1 relation. There is a temperature effect that can "move" the magic voltages quite a bit. You also need to be careful about loads (or charging) on the battery when measuring the voltage.

What to do:

1) Get a full disconnect switch installed so you can properly store the trailer.
2) Return your in warranty batteries to a battery dealer and have them checked. If they are not up to spec, get a refund or a replacement ( = I don't know how your battery warranty works)
3) Study up on the loads in *your* trailer. This may involve measuring them. If your fridge pulls 1A running on propane, that's 24AH per day. If your parasitic loads pull 1/4A that's 6AH per day. With nothing else at all running, you are using 30AH a day. That's a max run time of <4 days on 220AH lead acid's to the 50% "stop using" point. Is't very easy to add another 30AH a day to those numbers ....
4) Plug in to shore power for at least 24 hours before you go off grid to be *sure* the batteries are topped off. You may get away with less, but better to be sure.

If you really want a significant improvement in off grid days and the stuff above isn't getting you there, you need more battery. That's like 2X or 4X more not another 10%. If you are willing to spend the money, that can be done with lithiums or other ways.

Yes, this could go on. There are lots of threads here on the forum to dive into on various bits and pieces of this puzzle.

Bob

[SGandMT]

To piggyback on ibosket's situation, I am in a similar one. In addition to replacing the 12v with new AGM's 2 years ago, I added 300w of solar, too. Thought we were pretty well set-up for boondocking, however, on a recent night when the temps dipped into the 30's in Tahoe, the batteries barely made it through the night with running the furnace. The dealer told me the furnace is a big draw, so maybe I am just ignorant, but it seems to me that having the ability to run the furnace when it's cold would be an essential function that our set-up should be able to accommodate. So either I am misunderstanding the situation, or I am concerned I have a problem, and would appreciate any guidance.

[drbrick]

Batteries need attending trickle charge and cannot go 6 weeks on "Store Mode" as stated above. We run 2- Trojan T-105s with 200w solar to keep them charged during the winter lay-up on Vancouver Island. If you store indoors you will need a 110v trickle charge to keep them alive. Sorry to say if your batteries flatlined they're dead....

Does not matter what kind of batteries you use they ALL have limited usable power and require some sort of recharging process - i.e. solar, generator etc while boondocking.

[uncle_bob]

Originally Posted by SGandMT

To piggyback on ibosket's situation, I am in a similar one. In addition to replacing the 12v with new AGM's 2 years ago, I added 300w of solar, too. Thought we were pretty well set-up for boondocking, however, on a recent night when the temps dipped into the 30's in Tahoe, the batteries barely made it through the night with running the furnace. The dealer told me the furnace is a big draw, so maybe I am just ignorant, but it seems to me that having the ability to run the furnace when it's cold would be an essential function that our set-up should be able to accommodate. So either I am misunderstanding the situation, or I am concerned I have a problem, and would appreciate any guidance.

Hi

Indeed the furnace in most trailers *is* a big draw. Getting one night on the batteries is pretty typical on a stock trailer.

As delivered, my trailer was good for maybe 2 days off grid and a bit less than that in the cold. Adding up the various drains (loads) on the trailer and comparing that to the battery capacity .... yup that's how it worked out.

If you are going to be off grid on batteries you need to be aware of what your loads are. It's no different than watching the propane or water. There's only so much there and you *can* run it dry pretty quick. A proper shunt based battery monitor like the Victron BMV-712 might help you with this, but it does not change the "finite" nature of the resource.

Water also limits your off grid time. If you both need long hot showers every morning, you may not make it more than a couple days on a tank. The thing about water - it's very obvious as you use it. With battery, not quite so obvious without something like the 712.

For us, 400AH (usable) of lithium batteries combined with 4 solar panels on the roof turned out to be the "right" answer. Yes it cost a bit. So did the AS . We now can reasonably expect to go for two weeks off grid.

Best guess is that water will get us before the batteries do. You might not want to sit next to us in a restaurant after two weeks though ..... Not all AS models come with the same size tanks so this will be more of a limit on smaller trailers.

Indeed if it's really cold, propane would knock us down from the two week mark. The issue of pipes freezing tends to keep us from spending a lot of days out in sub-freezing temps ....

RV's (all of them) are targeted at a "typical user". I don't know of any common ones (= ones you have seen more than one of) that are set up for weeks off grid. Typical users apparently don't do that. They hang around the KOA on shore power most of the time or they are out for a weekend at the park in August. If it's more than that, they bring a cheap / lightweight inverter generator.

Bob

[pcskier]

Originally Posted by uncle_bob

You might not want to sit next to us in a restaurant after two weeks though ..... Bob

It really wasn’t that bad :-)

[JohnTF]

" I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. "

Lord Kelvin

Get some metering , loads - both DC Direct Current & AC Alternating Current .

https://www.google.com/search?q=watt...hrome&ie=UTF-8

I bought the WattMeter about $20 for AC and Powerwerks about the same for DC .
If you want the warrantee life - you have to use measuring of both your loads & battery usage ---- and they have to match , so the reason you HAVE TO measure .

If you know of a better source - please post , or even just any good source ?
https://batteryuniversity.com/

My last battery bank 4 x Trojan L16s running air-conditioning , furnace in MN winters radios , color TV , lights , full time RVing lasted about 13 yrs. under those loads , never more than 50% discharge , solar = 80% , generator = 20% for 13 yrs. - I caused/contributed the end , by not keeping a charge [ self discharge rate ] could no longer maintain the battery for at least through the winter - there discharge rate would no longer keep then charge for a few months , so they froze .

Know your loads - then see what you have to change , to make it work .
save battery's early end , lean not to give then a premature end ;(

[SGandMT]

Originally Posted by uncle_bob

Hi

Indeed the furnace in most trailers *is* a big draw. Getting one night on the batteries is pretty typical on a stock trailer.

As delivered, my trailer was good for maybe 2 days off grid and a bit less than that in the cold. Adding up the various drains (loads) on the trailer and comparing that to the battery capacity .... yup that's how it worked out.

If you are going to be off grid on batteries you need to be aware of what your loads are. It's no different than watching the propane or water. There's only so much there and you *can* run it dry pretty quick. A proper shunt based battery monitor like the Victron BMV-712 might help you with this, but it does not change the "finite" nature of the resource.

Water also limits your off grid time. If you both need long hot showers every morning, you may not make it more than a couple days on a tank. The thing about water - it's very obvious as you use it. With battery, not quite so obvious without something like the 712.

For us, 400AH (usable) of lithium batteries combined with 4 solar panels on the roof turned out to be the "right" answer. Yes it cost a bit. So did the AS . We now can reasonably expect to go for two weeks off grid.

Best guess is that water will get us before the batteries do. You might not want to sit next to us in a restaurant after two weeks though ..... Not all AS models come with the same size tanks so this will be more of a limit on smaller trailers.

Indeed if it's really cold, propane would knock us down from the two week mark. The issue of pipes freezing tends to keep us from spending a lot of days out in sub-freezing temps ....

RV's (all of them) are targeted at a "typical user". I don't know of any common ones (= ones you have seen more than one of) that are set up for weeks off grid. Typical users apparently don't do that. They hang around the KOA on shore power most of the time or they are out for a weekend at the park in August. If it's more than that, they bring a cheap / lightweight inverter generator.

Bob

Thanks, Bob. I have been told that the Lithiums don't work very well (or much at all) in the cold. Have you experienced this? I am hesitant to solve one problem only to create another.

[uncle_bob]

Originally Posted by pcskier

It really wasn’t that bad :-)

Hi

I was only up to about 10 days at that point

Bob

[uncle_bob]

Originally Posted by SGandMT

Thanks, Bob. I have been told that the Lithiums don't work very well (or much at all) in the cold. Have you experienced this? I am hesitant to solve one problem only to create another.

Hi

Lithiums don't like to be charged when the battery is below freezing. The BMS on something like the BB's stops the charge process automatically. All batteries loose capacity at cold temperatures. Lithiums are no different than any other batteries in that respect. You will not get as many amp hours of discharge when they are cold.

The key thing here is that it's battery temperature that matters. What the Weather Channel thinks is not the deciding factor. Based on watching the temperature probe on my batteries, they can be anywhere from 5 to 10 degrees warmer on a cold morning than the weather forecast (or my watch) seems to think they should be. That's not surprising, they are big and massive. They don't heat up or cool off very fast.

Since *charging* is the issue, the same big ball in the sky that runs the solar panels also does it's thing for the battery temperature. By the time that the sun is up enough to do some good, the 28 degrees last night is 38 degrees this morning. The batteries will be warming up rather than cooling off ....

So, have I noticed it? Sure. Do I watch what's going on? Of course. I also have two batteries indoors in addition to the two in the battery box. If things get really nutty, I have the ability to isolate the outdoor set and monitor them separately from the indoor set. So far (in two camping seasons), I have never needed to use the isolation setup.

=========

If you look at how batteries are rated, their "life" is spec'd to the 80% capacity point. We pretty much *never* look at battery life that way. I have yet to see a post from somebody who set up to *measure* capacity on their X year old batteries. We use them until they die completely ( = won't hold a charge for 10 minutes .....). That's way past the 80% point.

I don't have a problem with using *anything* for as long as it does what you need it to do. That's only common sense. If your batteries are doing what you need them to do, keep using them !!! The only point is that different measures will give different life numbers.

If lithiums run for 3,000 or 5,000 cycles to the 80% point. There is no way to know how long they will run to the "death" point. We just don't have the data and manufacturers (of all batteries) simply don't test them to that point. Will any of us live long enough (or more relevant own a specific RV long enough) to *get* that data? Check back in 2,5,10,50,100 years

Bob