Battery Charger While Storage

[uncle_bob]

Originally Posted by 68 Overlander

Certainly not what we see but some truth in the voltage part and that is why not many recommend Parallax in the aftermarket that have experience with the high voltage that overcharges batteries. We see >55 amps in dual batteries in 200 AH range all the time. The "typical Airstream" has had a 55 amp converter/charger for at least 15 years. They used Parallax exclusively until they changed this year for the WFCO 8955 PEC (30 amp service) and 9855 Deck mount on the 50 amp service models (Using the 8930/50 distribution panel that is separate) Parallax told us Airstream didn't want to pay for the higher cost of North American steel so they changed to WFCO. I believe them on that one and that is why you might have the WFCO if your Airstream is new.
Your battery bank (internal resistance) controls the amperage (current) going to your batteries. Always remember that it's the resistance in the battery that controls current/amperage into the batteries. It's not the converter except...(raising the voltage does help force more current via higher voltage for a period of time if the resistance is higher. Some like PD are 4 hours, others like Boondocker are now 2 hours but it needs to be about 14.2 to 14.7 or you will have slower charging for the first few hours.
It is true the current will taper in all cases as the battery charges and the resistance builds.
Further, if you ever hear your batteries gassing, that is usually a good thing as long as it doesn't continue more than a few hours.
The problem with continuous high voltage, especially during storage above 13.2 is that they never stop gassing. 13.6 is as high as I would use in the normal absorbtion mode (depending on battery manufacture) but it needs to drop back after a couple days if your are storing the batteries. The desulfation cycle will kick in and keep them from building stratification that leads to sulfation
When I hear somebody wanting a slow charge, it really means not a complete charge unless there is some bulk/boost voltage in the 14.4/14.8 range. You want '"some" gassing to get a full charge. It doesn't mean leave them at that voltage forever, just for a few hours periodically.
With AGM, All current and voltages are virtually the same but the desufation cycle is ignored by AGM betteries. Don't worry whether or not it has it. It doesn't do much but certainly doesn't hurt it.
Finally, don't confuse desulfation with equalization. Completely different.
Oh, and if you have a single battery with only 80-100 AH, don't worry about it. It won't make a difference with a 35 amp converter or a 75 amp converter. It's only going to take what it can and the rest is not used. Most people buy to large of a unit and I tell them if they ask.
If you are a rock star and run a bunch of amps in your AS, get the 100 amp unit but upgrade the cable to your batteries!!!!

Hi

Well, the 30 to 35A out of a 55 to 60A charger / converter was indeed from a "well known brand". It's what a number of other people have measured on the same or similar gear. There is a thread digging into that "mystery" in far more detail here on the forum. It gets into the voltage measurements and all the current numbers.

Swapping that out for a different (*way* more expensive) model / brand produced 60A into the exact same wires and exact same 400 AH of lithium batteries. Since everything else was same / same, it's pretty tough to decide that the converter was not the limiting factor. Indeed the device now runs at 80A, but that's with slightly different wiring so not exact same/same.

Bob

[abqdor]

Great thread with a lot of useful information. I'm still struggling with battery maintenance. I've already replaced one of the Interstate batteries, due to a dead cell and the other one is two years old. We keep the trailer at home, so I keep it on shore power. When at home, I keep it in the "store mode" with a 1.5 amp float charger connected, thinking that this keeps the factory installed AS converter out of the loop which few people seem to like.

When connected to shore power, the batteries read 13.6 volts which I don't think is a true reading of the batteries because when I disconnect shore power, the batteries read 11.9 volts.

Would a different float charger that was higher than the current 1.5 amps be better? I see some of the posts maintaining their batteries with 800ma and some using 5 amp chargers. What am I doing wrong?

[Bill M.]

If the batteries are at 11.9 you are not putting enough charge into the batteries. When I store our trailer I connect the trailer to a timer and give it power for 1 hour per day. Enough for the stock converter to keep it powered and does not dry out the batteries.

[68 Overlander]

Originally Posted by abqdor

Great thread with a lot of useful information. I'm still struggling with battery maintenance. I've already replaced one of the Interstate batteries, due to a dead cell and the other one is two years old. We keep the trailer at home, so I keep it on shore power. When at home, I keep it in the "store mode" with a 1.5 amp float charger connected, thinking that this keeps the factory installed AS converter out of the loop which few people seem to like.

When connected to shore power, the batteries read 13.6 volts which I don't think is a true reading of the batteries because when I disconnect shore power, the batteries read 11.9 volts.

Would a different float charger that was higher than the current 1.5 amps be better? I see some of the posts maintaining their batteries with 800ma and some using 5 amp chargers. What am I doing wrong?

Based on your comment, your 2 year old battery is likely preying on your new battery. 11.9 is below 50% SOC and it would have been best to replace both of them. I use 6 months as a rule for mixing new and old batteries in the same bank. Not saying it can't be longer but I've seen shorter lifespan when doing so. You should be floating around 13.2 and after removing the charge, your rested open circuit voltage should be at least 12.7, usually a little higher. Since you have power where you store your Airstream, upgrading to a 4 stage converter will not only make your batteries last longer, but prevent the need for a trickle charger.

[DKB_SATX]

Originally Posted by abqdor

Great thread with a lot of useful information. I'm still struggling with battery maintenance. I've already replaced one of the Interstate batteries, due to a dead cell and the other one is two years old. We keep the trailer at home, so I keep it on shore power. When at home, I keep it in the "store mode" with a 1.5 amp float charger connected, thinking that this keeps the factory installed AS converter out of the loop which few people seem to like.

When connected to shore power, the batteries read 13.6 volts which I don't think is a true reading of the batteries because when I disconnect shore power, the batteries read 11.9 volts.

Would a different float charger that was higher than the current 1.5 amps be better? I see some of the posts maintaining their batteries with 800ma and some using 5 amp chargers. What am I doing wrong?

2 things.

1) Except in very limited cases, you should replaced paired batteries in pairs. The battery with a dead cell was causing your charging system to abuse the battery that still had all 6 cells, so its life was shortened after the other battery's life ended.

2) When you disconnect shore power, unless you have some huge load on the batteries at that time (more than your trailer should be able to put on them) you should see way over 12v. The no-load resting voltage on fully-charged lead-acid batteries should be about 12.7v and 11.9v is essentially dead.

[uncle_bob]

Hi

+1 on replacing batteries all at the same time. Batteries really don't like running in parallel. It works (and manufacturers say it's ok). By far it works best with identical batteries ( same age / same number of cycles / same brand / same model / same temperature ...).

Bob

[gypsydad]

My advise: Get new batteries and a 4 stage converter. My opinion from experience: You will be much happier when you finally bite the bullet and get this done.

Batteries: I had good luck when I went to AGM's few years ago on my 2014 25'AS. I just switched to 6V Trojans with my 28', after going thru 2 new sets of 12V Interstates in 1.5 years....They hold charge very long time compared to the 12V's I had been using. I found 2-new 6V Trojan wet cells cost me $135/each and they fit in my box no problem. Not sure about your battery box, so you might check size. Many people get less expensive 6V batteries at Sams or Costco which they also have had good luck with also.

Converters: check out bestconverters.com and talk with Randy. Both the Progressive Dynamics and the Boondocker are rated pretty high by users here on the Forum. Read the technical specs on how they work and how they maintain batteries on the website. Good luck!

[delrossa]

There is no need to get wrapped around the axle about this. You can get a simple battery disconnect from Amazon. It is simple to install. I have attached a picture. Once it is installed you can disconnect your batteries with a simple twist of the knob.
I purchased the Battery Maintainer for around $80. The battery maintainer actually desulfates the batteries. The Battery Maintainer after charging goes into a float mode.
I have two of these and they work great. It comes with a plug that you can permanently install so when you are not using your Airstream all you have to do is turn off the batteries via the disconnect switch, plug in the charger and walk away.
Works great.
On the charger there are symbols that show the mode and charge condition of the batteries.
Good luck.

[JJTX]

Originally Posted by abqdor

Great thread with a lot of useful information. I'm still struggling with battery maintenance. I've already replaced one of the Interstate batteries, due to a dead cell and the other one is two years old. We keep the trailer at home, so I keep it on shore power. When at home, I keep it in the "store mode" with a 1.5 amp float charger connected, thinking that this keeps the factory installed AS converter out of the loop which few people seem to like.

When connected to shore power, the batteries read 13.6 volts which I don't think is a true reading of the batteries because when I disconnect shore power, the batteries read 11.9 volts.

Would a different float charger that was higher than the current 1.5 amps be better? I see some of the posts maintaining their batteries with 800ma and some using 5 amp chargers. What am I doing wrong?

I would not leave any RV connected to shore power for long periods of time when not in use. Not unless you install a different battery charging system that does not keep putting out several amps .

A battery only needs milliamps once it reaches a target voltage. Any more than that over long term, cooks the battery and damages it. Smart chargers will hold the voltage where it needs to be and no more.

I would use a simple 2-4amp smart charger, like i Mentioned and clip the charger leads to the battery and use that to top it off when storing the RV.

Google BATTERY TENDER.

[HowieE]

Originally Posted by gypsydad

Batteries: I had good luck when I went to AGM's few years ago on my 2014 25'AS. I just switched to 6V Trojans with my 28', after going thru 2 new sets of 12V Interstates in 1.5 years....They hold charge very long time compared to the 12V's I had been using. I found 2-new 6V Trojan wet cells cost me $135/each and they fit in my box no problem. Not sure about your battery box, so you might check size. Many people get less expensive 6V batteries at Sams or Costco which they also have had good luck with also.

How does the total amp hours of 2 6 volt batteries wired in series compare to that of 2 12 volt s in parallel?

[delrossa]

The battery maintainer that I purchased is the Battery Minder. Tried to change it in my original post but couldn’t.

[JJTX]

Originally Posted by delrossa

The battery maintainer that I purchased is the Battery Minder. Tried to change it in my original post but couldn’t.

Dont get me started about the post locking here.. Oye!

[Mattirs]

Originally Posted by HowieE

How does the total amp hours of 2 6 volt batteries wired in series compare to that of 2 12 volt s in parallel?

In series the volts add up, amps stay the same e.g. two 100 amp 6 volt batteries in series equals
100 amps @ 12 volts.

In parallel the amps add, the volts stay the same Two 50 amp 12 volt batteries in parallel equals
100 amps @ 12 volts.

Series volts add
Parallel amps add

Thanks
Matti

[HowieE]

In parallel the amps add, the volts stay the same Two 50 amp 12 volt batteries in parallel equals
100 amps @ 12 volts.
[/QUOTE]


I accept the description of series and parallel connection but now have to ask.


If you can get 6 volt and 12 volt batteries of the same physical size, to fit in the battery boxes. Why would anyone have ever gone to 12 volt batteries in parallel?

[abqdor]

OK, so I've learned a few things:

1). I should have replaced both batteries when a cell went bad in one of them....makes perfect sense, but I questioned the guy at Interstate about this and he said it wasn't necessary.

2). Now that I need to replace both batteries, I should consider 6 volt batteries as a replacement. Many seem to think this is a better way to go, provided they will fit in the battery box.

3). Maybe get a battery disconnect switch, but I thought that the "store mode" switch inside the trailer took the converter out of the system and only left me with parasitic draw, like detectors, therefore making a disconnect switch unnecessary. And if I do need a battery disconnect switch, do I need just one for the positive lead?

4). If I've done all of the above, a smart charger, even if it is in the milliamp range will suffice to keep good batteries maintained.

5). And finally, I should consider a 4 stage converter to replace the factory single stage converter. This I will probably save to last and work on the other items first.

What a great forum!!!

[Mattirs]

Originally Posted by HowieE

In parallel the amps add, the volts stay the same Two 50 amp 12 volt batteries in parallel equals
100 amps @ 12 volts.

I accept the description of series and parallel connection but now have to ask.


If you can get 6 volt and 12 volt batteries of the same physical size, to fit in the battery boxes. Why would anyone have ever gone to 12 volt batteries in parallel?[/QUOTE]

Two 12 volt are generally cheaper than two 6 volt batteries, plus if one 12 volt battery goes bad you still have 12 volt power with 1/2 the amps.
If a 6 volt battery goes bad you now have the same amount of amps at 6 volts that are useless in a 12 volt system.

Me, I am just cheap.

Matti

[gypsydad]

Originally Posted by Mattirs

I accept the description of series and parallel connection but now have to ask.


If you can get 6 volt and 12 volt batteries of the same physical size, to fit in the battery boxes. Why would anyone have ever gone to 12 volt batteries in parallel?

Two 12 volt are generally cheaper than two 6 volt batteries, plus if one 12 volt battery goes bad you still have 12 volt power with 1/2 the amps.
If a 6 volt battery goes bad you now have the same amount of amps at 6 volts that are useless in a 12 volt system.

Me, I am just cheap.

Matti[/QUOTE]

Not an expert here, but I believe the 6V "golf cart" deep cycle batteries are built with "stronger/thicker" internal cells, which deliver consistent voltage/amperage while not depleting as fast as the "Interstate" type 12V batteries...hat come with the AS. you can get these at Costco or Sams at pretty similar pricing to 12V's, from what I have seen. I think the 12V wetcells can deliver reasonable service when maintained, but their internal composition is not same as the 6V golf cart types...I know the 6V are very heavy and a bit bigger than the 12V's. there are some folks here that know the difference much better, but that's my 2cents...if money is no object, I would consider the Li batteries..I am told they will deliver stead voltage till they are totally depleted to about 5%, and then charge back up to full charge...and life span is 30 years?? For me, I am trying the 6V recommendations I have read hear and after talking with several AS owners.

[rmkrum]

I can attest to the weight of those Sam’s Club golf cart batteries. Pulled and replaced mine after bolting down my battery box on Wednesday. Back is still aching. There is a lot of lead in those things. I’m darn glad I bought a sturdy, purpose built golf cart battery lift strap before I tried this...I’m not getting any younger or stronger!

[uncle_bob]

Hi

Just as with 12V batteries, there is are a wide range of 6V batteries. Some are made well, others ... not so much.

With two 12V batteries wired in parallel, the most common fault (cell short) likely takes out both batteries. With 6V batteries, the same fault takes out the stack. Either way, you are off to buy a new pair of batteries. You very much want a matched set.

Bob