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neil.ervin 11-02-2004 07:48 PM

Can't get batteries charged -- why not?
Iíve been questioning my batteries. I have 2 Group 24 batteries on my new 2005 25í Safari. This weekend was my third trip out. Its delivery was in early August. Iíve not been able to get the batteries charged up on any trip. I checked the tow plug with a Teckonsa tester. There is 12V current from the tow vehicle. My multimeter readings are all with the battery disconnect switch (near door) in STORE mode.

We started home with the airstream meter (near stove) battery reading at 3/8. After driving 3.5 hours home it read 1 / 2 (multimeter said 12.27V). I hooked up the trailer to household 120V and 18 hours later the airstream meter read 5/8 (multimeter said 13.01V).

Shouldnít the batteries charge to a greater level, either during the trip home or by the 18 hours on the converter charger?

Three hours after the 18 hours of converter charging I tested each cell while the airstream meter (75 degrees) read 5/8:
1.100. 1.100, 1.110, 1.125, 1.090, 1.090 battery 1
1.100, 1.100, 1.100, 1.125, 1.100, 1.100 battery 2
the multimeter read 12.80v.

Can anyone help me? I need full batteries because I camp without hookups.

markdoane 11-02-2004 08:09 PM


The voltage reading doesn't match your specific gravity. At 12.80v you are 100% charged, but the specific gravity shows less than 0%.
I think your batteries need to be 'equalized' with a high voltage charge, to stir up the electrolyte and give you a more accurate specific gravity reading.
Have you needed to add water to any of the cells?
Conventional wisdom is that the cells should be within 0.050 specific gravity. Yours are 0.035, but until you get the electrolyte mixed I wouldn't put a lot of trust in the numbers.

See this brief description:

Without knowing the ah rating of your batteries and the charge rate of your converter, It just might be that you need to charge longer and recalibrate your voltmeter. That's the best case scenario.

overlander63 11-02-2004 09:16 PM

I will try to add to what Don has already said. 1.275 SHOULD be almost fully charged, if for some reason it is not, you may have a problem with the batteries. That said, when you are driving along, recharging your trailer batteries with your tow vehicle's alternator, you are charging maybe 40 amps into the two batteries, or 20 amps per hour per battery.

Imagine two milk jugs, which contain, say, 500 ounces each, and fill them at the rate of 20 ounces per hour, how long will it take to fill both milk jugs?
This is a bit of an oversimplification, but I think you can see why after a 3.5 hour drive home they are not fully charged. You have only restored 70 amps capacity per battery. And that is if everything is perfect.
Now, on to testing your batteries. If you don't have a deep-cycle battery charger, it would be a good idea to invest in one, they are not expensive, and will save you from having to plug your trailer in just to charge them. If you don't want to get a charger, take your batteries to a friendly repair shop and ask them to slow charge them both, at least overnight, and preferable for 24 hours. After charging for 24 hours, bring them home, and let them sit for another 24 hours (probably the hardest part, not messing with them.) After the 24 hours, check the specific gravity of each cell, they should all read around 1.275 or above. If you have one cell significantly lower than the rest, that cell is bad, and the battery must be replaced. If all the cells read low, like in your original post, the battery is probably sulfated, and may still have to be replaced.
Also, I am not sure if you are aware, but the further you drain your batteries, the greater the chance that they may not "come back" when recharged. The opinion hereabouts is to let them get no more than 50% discharged before recharging them.

neil.ervin 11-03-2004 06:58 AM

I forhot to mention that just before this trip the unit sat in storage for 2 months and when I brought the unit home, the batteries were dead.

markdoane 11-03-2004 08:07 AM

It's possible the baterry is sulfated. Lead sulfate is formed when batteries discharge. As the batteries sit while discharged, the lead sulfate crystallizes and becomes harder to re-dissolve during charging. Again, the only possible recovery method is to apply a boost or equalizing charge.

Like Terry said, you need to get a good deep cycle battery charger. Some chargers have an 'equalizing' charge rate. You should charge the batteries at a rate equal to at least 10% of the ah rate of the batteries to insure longest life. If the two batteries total 200ah, you should charge them at 20a. I don't think your converter was putting out an adequate charge rate.

stephen.s1 11-03-2004 08:18 AM

Another observation/suggestion. For longish term storage turn off your master switch. The batteries should not be dead after 60 days. Something was probably drawing 'em down. As a boondocker, you should really investigate solar charging. One 75 watt panel, in the direct sun, peaks our 2 120 AH batteries. Our next trailer will have room on the roof for 2 100 watt panels.

74Argosy24MH 11-03-2004 08:27 AM


Originally Posted by neil.ervin
We started home with the airstream meter (near stove) battery reading at 3/8. After driving 3.5 hours home it read 1 / 2 (multimeter said 12.27V)

Unless you have a really heavy charge line (and a good ground) it will take a long, long time for the batteries to charge off the tow vehicle. A 12 or 14 ga. wire 30 ft. long is sort of like filling Terry's jugs with windshield washer tubing.


neil.ervin 11-03-2004 04:11 PM

FYI, I always place battery disconnect switch in STORE mode while in storage.

Batteries shouldn't go dead in 60 days? I would prefer not but I'm hearing from different sources that they can and do go dead quickly. Maybe it has to do with the 110+ temperatures here in Sun City, AZ.

I intend to install solar. Does it still work while the disconnect switch is in STORE mode?

But for now, what is the correct thing to do? Take batteries off and have them charged at battery store?

What brand/size charger to buy? I believe my two group 24 batteries (deep cycle) are rated at 80 amps each.

Desulfinate? I understand the SolarBoost controller is good for desulfination. However the new airstreams are prewired for only InterMountain controllers. Your thoughts?

Thanks for your help.

rseagle 11-03-2004 04:27 PM

Hi Neil,

I use a 12v Power Pulse Desulfator by Pulse Tech. See the attached link where I bought mine.


markdoane 11-03-2004 04:38 PM

I would take the batteries to a battery service shop, explain the problem to them, and see what they recommend. That will get you on the road again and tell you if the batteries are recoverable.

Do not buy a charger until you are sure what and how you plan to do the solar panels. I don't have solar, but I find it hard to believe that A/S would prewire for something that is brand specific, like Solar Boost vs Intermountain. I thought Intermountain was just a re-seller.

Anyway, if you plan to put in a well designed solar system, the money you spend now on a charger might be wasted.

john hd 11-03-2004 07:21 PM

don't store your batteries in the trailer.

get some forklift quick disconnects and take them home with you.

60 days is a long time for batteries with no attention, not to mention your lp gas detector will drain them no matter what position you place the switch.


john hd 11-03-2004 08:34 PM

as requested...
here is a site with the disconnects


davidz71 11-03-2004 09:39 PM

I have found that charging from the alternator through the charge cable to the trailer is pretty much worthless (on my trailer that is). I have driven for several hours after using lights heavily and there is not that much change in the battery charging. I wouldn't rely on it to charge your batteries.

I have had excellent results with the small 1 watt and even the 4 watt BatteryMinders which hook up to an AC outlet. When it is not hooked up then the 5 watt PulseTech Solargizer solar panel charger takes care of the job. My two group 27 Delco Voyager batteries are about 4 years old with no problems.

If you have access to AC buy the 1 watt BatteryMinder from, plug it in and let it do its work. Check your battery water level first of course. If you can't plug in and the trailer is outside then you also have the option of the PulseTech solar charger (also comes in 10 watt model but more expensive) or the BatteryMinder solar unit from the source mentioned above. All these units have multistage charging and desulfating mode. When you eventually go to a large solar panel or panels, use the other units for charging other batteries or hook them up to your vehicles from time to time.

I unplug my Magnetek converter after it has been charging the batteries when plugged into shorepower for a few hours because I worry about that type of unit boiling water out of my sealed batteries. I'm not worried about the BatteryMinders because of their type of charging.

Taking batteries out of the trailer is a PITA so I just don't do it other than to check the battery posts to make sure they are clean and properly coated with that red stuff available from Walmart.

jordandvm 11-04-2004 12:58 PM


Originally Posted by rseagle
Hi Neil,

I use a 12v Power Pulse Desulfator by Pulse Tech. See the attached link where I bought mine.


Just how big of a problem is "Sulfation" with batteries. Their claim is if you get their product, your battery will last 3X longer.........meaning 9 years instead of 3 years?????
Here are their claims:
Make Your Battery Last 3 Times Longer !
Rejuvenate that dead battery you thought was no good
Keep your battery charged and virtually free of power robbing sulfation

Has it really made a difference in your batteries, Bob?

davidz71 11-04-2004 07:33 PM

Sulphur buildup is what kills many a battery. If the charger you have "shakes" the plates with pulses then it knocks the buildup off and allows it to be mixed with the battery acid. Some batteries are so coated they give the impression that they are bad and this is why the companies claim it can rejuvenate batteries. Of course, if you have a dead cell then nothing is going to help.

neil.ervin 11-10-2004 04:11 PM

Here's an update.

I took batteries to Interstate. They brought the batteries back to life: one 12.96v, the other 13.09v.

I called airstream. Yes, the LP detector bypasses the battery disconnect switch. I have a feeling that more than that bypasses the switch, like the carbon monixide detector.

This coming Monday I am having solar installed. One Kyocera EC80 panel on the roof and one on the ground (so I can point it at the sun). Included will be a Heliotrope controller with pulse desulfinization and HTTP (or HPPT) capability. I wanted a solarboost 2000 but they are larger physically and might not fit into allowed space.

The Airstrean solar pre-wiring is for a $400+ Specialty Concepts controller. My dealer doesn't even use them. They install a $100 controller, but were willing to order the $400+ controller.

The reason the detector(s) bypass the disconnect switch is that it is the LAW. Seems strange to force folks to have their detectors active while the unit is in storage, thus causing the batteries to die. So I would assume that most folks are now disconnecting the black negative battery wire when storing their (newer) units for more than a couple of weeks.

Now to decide if I need to buy a Honda 2000 generator for those cloudy days while out camping...............

Everyone, thanks for your help.

jcanavera 11-10-2004 04:29 PM


Originally Posted by jordandvm
Has it really made a difference in your batteries, Bob?

I have used a pulse charger for years when I had Ni-Cad rechargable batteries for my cell phone. It gave a few more months of life to batteries that could not hold a charge. New batteries had much more life.

I can say that the technology is valid.


markdoane 11-10-2004 05:12 PM


Glad everything worked out ok. Be sure to post a picture of your PV panels when you get them.

neil.ervin 11-11-2004 05:43 PM

Let's try some math to bring my understanding up to date.

I have two Group 24 batteries, a total of 160 amp/hours. I believe they are rated at 80 amps each. Assume they are depleted 30% or about 50 amps.

I've heard that a tow vehicle's alternator will charge at the rate of 65-80 amps per hour. True/false? If so, then the 50 amps of charge to bring bastteries full should take less than an hour. True/false?

A trailer converter puts out about 8 amps/hour, thus would take 6.2 hours to charge the 50 amps. True/false?

A battery charger, say one rated for 15 amps/hour, could charge the 50 amps in 3.3 hours. True/false?


markdoane 11-11-2004 06:48 PM


All are false. How much information do you want, and do you want something technical, or just the generally accepted guidelines without a lot of fuss.

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