Batteries: what did I do wrong?

[Jammer]

Originally Posted by lewster

The experience of others differs greatly. Vinnie's got it right! When properly charged (and this is extremely important with any battery), quality AGM batteries like Lifelines will far outlast liquid lead acid types. I have several clients with very large battery banks in motor homes that are approaching 10 years and still show above 95% capacity. I have many more that are at least 7 years old and still more over 5 years.

Flooded deep cycle batteries can approach this age also if cared for.

Different batteries need different, very specific charging profiles to be properly charged. They also need temperature compensation (there's that phrase again) to keep the charging voltage within the acceptable range that is dictated by the ambient temperature. Nothing kills a battery faster than putting a constant 13.6 VDC (as with the original converter found in new Airstreams) into a battery that regardless of the temperature of that battery. Hotter batteries need less voltage to charge and conversely, colder batteries need more.

Also, a battery is never fully charged by 13.6 VDC. Most need at least 14.2VDC for a bulk and absorption charge and a float charge of 13.2 VDC. Some liquid cells need as high as 14.6 VDC for bulk and absorption charging and 13.4 for float. It varies by battery type and battery manufacturer…..AND BY TEMPERATURE!

Lewster is absolutely correct on all these points.

Single-stage converters will require 24-48 hours to fully charge a battery at 75 degrees. At lower temperatures it will take longer, below 50 degrees the battery will never be fully charged, below 20 degrees very little charging will take place even if the battery is almost discharged.

Multi-stage converters that are not temperature compensated will work fine around 70-85 degrees but will exit the charge cycle prematurely at lower temperatures leaving a partially charged battery.

You can't really understand what's going on with your batteries unless you are able to measure voltage, temperature, and charge and discharge current. It also helps to measure specific gravity particularly if voltage is not known accurately or there is a problem with a particular cell.

[CA_Tallguy]

You can get some decent juice from your tow vehicle with upgraded wiring. In order to get a full charge, however, you'd need to get a unit such as this CTEK D250S to regulate and boost the voltage....

Amazon.com: CTEK 56-677 Battery Charger: Automotive

I don't know to much about the CTEK but it sounds great and you can even expand it and use it for MPPT solar charge control.

Other "battery to battery" chargers are sold by Balmar (probably most popular), Xantrex Echo Charge (seem to think it is made by Balmar), and Sterling/Promariner

Although simply upgrading to heavier wiring might help voltage get back to your batteries, I wouldn't do that without having some sort of way to disconnect batteries when the alternator isn't running. The devices listed above should provide that function along with boosting/regulation.

[BeachHouse]

It is fascinating to read all of this discussion. It was my plan to replace the factory converter with a three stage unit when the batteries need to be replaced. Ours are about 4 years old and have always been continuously connected to shore power (except while towing) with the store switch in the on position. I check the water occasionally, but it has never been low. We don't boondock except at the occasional Walmart so the batteries don't hardly ever get used. I am realizing from this discussion that we are doing it wrong, though now scared to change what we are doing since it seems to be working. The PO said he changed the batteries when they were about 6 years old. He kept it continually connected to shore power and rarely used the trailer. Is it just that we really aren't using the batteries that make this work for us?

[almcate]

Battery education charges on, and maybe a short-term resolution is in sight. My first misconception I got straight from the AS manual indicating that TV power thru the umbilical would charge the battery. Which apparently it does, but a superficial charge that looks like a full charge on the Green-Yellow-Red monitor. When I would pull into a park site with full hookups where I dutifully put the batteries into store to avoid overcharging (noting that continuous bulk charge was damaging to my batteries). Since it only looked like I had fully charged the battery, when coming to a site without power, I would see a dramatic drop within hours or on subsequent days after running the generator for an hour or two. Seems like 4-5 hours of "green" was all I could get out of my batteries before I'd have to run the generator. My conclusion was I must have ruined my batteries somehow as they weren't holding a charge. Which brings me to Pismo Beach North campground and a trip to Pismo Coast RV Service to replace my batteries.
First they check the batteries and both are in good condition. Huh? Tho continuous bulk charge is not a good thing, the tech tells me a couple days of charging with shore power through the converter is what is needed to get the battery bulk charge after which moving from Use to Store and a trickle charger over 24 hours should bring a battery up to full charge. Yes, a 3-stage converter makes it much more convenient and he'll be happy to replace if I decide (even does house calls).
So at this point, new batteries not needed, no money spent, and I'll see if the suggested routine of mixing a couple days shorepower charge and a day of trickle charge finally gives me fully charged batteries that can last for more than five hours. Tech points out that since I'm mostly on shorepower and only off-grid here and there, solar isn't going to be a salvation. The 3-stage would be more convenient and that may still be in the cards if the charging routine suggested doesn't work out. I'll follow up when we get to shorepower again next week.

[mstephens]

Add me to the "battery uninformed." I too thought the TV was charging our TT batteries with a few hours driving.

We just got back from a 3 day boondock at Mohave Preserve. Ok, I had new batteries at the start and don't know the actual voltage at the beginning. After 2 nights and 3 days, we drove 3 hours home. I decided to measure the voltage. It was 12.02V in STORE mode when we got home. I now see that's pretty low. Too low even.

We have the trailer in a covered storage lot, so I will have to bring it home to charge the batts. From 12.02V how long should the standard Airstream (2012) system take?

[lewster]

Originally Posted by mstephens

Add me to the "battery uninformed." I too thought the TV was charging our TT batteries with a few hours driving.

We just got back from a 3 day boondock at Mohave Preserve. Ok, I had new batteries at the start and don't know the actual voltage at the beginning. After 2 nights and 3 days, we drove 3 hours home. I decided to measure the voltage. It was 12.02V in STORE mode when we got home. I now see that's pretty low. Too low even.

We have the trailer in a covered storage lot, so I will have to bring it home to charge the batts. From 12.02V how long should the standard Airstream (2012) system take?

If you have the OEM single voltage battery burner of a converter (can you tell what I think of them????) then it is probably a 55 amp unit. Assuming that your batteries are a pair of Interstate group 24 liquid lead acid types with a total capacity of about 160 amp/hours, and you have depleted them to a remaining capacity of about 40%, I would think that you need close to 100 amp/hours of charge to bring them back to full (if you call a constant voltage charge 'full'.

Your batteries will never see the manufacturers recommended bulk and absorption charge of 14.4-14.6VDC to get really full…..but I digress!

Probably 2-3 hours ……………….should bring you 'close'.

[rodsterinfl]

Each of us have our lessons to learn. I posted my battery/charger journey here:

http://www.airforums.com/forums/f449...le-109317.html

I updated the charger/converter with a compatible upgrade unit from progressive dynamics.

[idroba]

mstephans: Typical charge current from your TV will be in the 4 to 6 amp range. My new Grand Cherokee and 2014 FC 20' sometimes hits 10 or 11 amps but not for very long. Three hours of lets say 6 amps is giving you 18 amp hours of charge total. If your batteries are half discharged (pair of original #24's) they would need about 75 amp hours to bring back, so you can see that a 3 hour drive won't do it. It also sounds like your batteries were discharged a lot lower than 50%.

How long to charge on the original converter/charger plugged into grid power? My best guess would be 24 to 36 hours, considering a lot of guesstimate factors.

As you can see from this thread, there is nothing simple about batteries, their charge rate, discharge rate, how long they may last, how to store them and on and on. We like simple solutions to complex problems, but with batteries I am afraid there are none.

[mstephens]

Thanks Lew. Good info and very useful.

We're odd ducks. We've had our trailer 2 years, and have done LOTS of trips, but this was the first boondocking we've done. We're trying to see if this is something we want more of or less of. We have no charger or genny. I'd say we were pretty well underprepared! Ha Ha. I figured the car would charge us right back up when we moved to the second site.

Yes, I have the stock AS "burner".

Rodster - that's a good looking unit. Happy with it? I came across this one today also: PowerMax Boondocker Converters

Do I dare assume that if you have a nice 3-stage converter and you plug in a genny, the world is good? Or, are there yet more lessons to learn?

Always something new to learn.

[lewster]

……snip'

Do I dare assume that if you have a nice 3-stage converter and you plug in a genny, the world is good? Or, are there yet more lessons to learn?

Always something new to learn.[/QUOTE]

That would work. It's what I call the 'quick and dirty' solution boondocking battery maintenance