House battery while hooked up

We spent about 12 days at Fort Wilderness in the Florida July summer heat.  I checked the battery after about 5 days, and once again found it "boiled" almost dry.  Refilled and 3 days later it needed water again.

With my analog meter, I could see that it only has about 12V while being charged.  I'm wondering if that means it's on its way out, assuming that the regulator would be trying to charge it at about 13.8 VDC and that the battery won't accept the charge.  That would explain why it bubbles away constantly, never getting up to full charge.  The regulator also seems to be very warm all the time, further evidence that it's working hard.

Our previous trip (Memorial Day) resulted in an unscheduled delay of 1-2 hours in a parking lot with the refrigerator running on +12V.  That weekend we had no hookups and the house battery died very quickly.  We could not revive it until we returned home to a 120V hookup.  After charging, the battery seems to discharge much more quickly than it did last year.  I did remove it from the trailer and store it in our unheated garage over the winter.  I trickle charged it once over the winter.

Thoughts or similar experiences?

Dan,
How old is the battery?  Is it a deep-cycle battery made for RV use?

While a volt & amp meter will tell you what is happening at a specific point in time, you can only determine the "condition" of the battery by using a "specific gravity" tester.  You should be able to buy one for under $20 at any good auto supply store.  What this tells you is, based on testing a sample of the battery acid, whether or not your battery is still good or approaching the end of it's life.  It makes no difference whether or not the battery is fully charged... this tester will work even if the battery is dead.

Hope you can solve this one with a minimum of difficulty and that all is working out well with the repair of your Thetford.  :

It's an Interstate RV/Marine deep cycle, but I don't know how old it is.  Didn't get the date code last time I dug it out.

Since I posted, I read in the Magnetek manual (all 4 pages) that these are symptoms of a defective battery, especially differing amounts of lost electrolyte.

I might try the specific gravity tester, or put the $20 toward a new battery that I'll know how old it is :-)

[Chris]

Dan,
 I think you have a bad cell  Sounds like the converter is working hard accordingly.  You can take it to an auto parts store, and they will load test it for you.  
Ct..

Dan,

I'd agree with Chris that it's likely your battery has a bad cell.

Usually the top of the battery has a sticker with a bunch of years and the 12 months.  The dealer is supposed to pop out the year and month the battery is sold, so they can pro-rate the price of the battery if you return it before the warranty is through.   If you check the sticker, you might be able to see when you bought the battery.

On a related topic, the Magnetek 6300 has what I can tell from my four page brochure to be a "smart" charger.  I recollect there wasn't much detail about this in the brochure.  Usually, "smart" charging means the battery starts charing at full charge, then goes into an absorption charge, then a maintenance charge.  Seemed to me the 6300 skips the absorption phase and does a ramp down trickle charge.  My 4-page manual is buried in a folded trailer in my garage so I can't check my memory here.

Does anyone know more about the Magnetek charging system?  Seems to me if this isn't a smart charger, and I spend a lot of time on shore power while camping, I'll just cook the battery.   I wouldn't be concerned except I've seen postings elsewhere from folks wanting to disconnect the charging subsystem from the 6300 and going to something like the Trupower charger.

I use a Guest 2612 smart charger while the trailer is park  in the garage.  So far, I'm happy.  But should I be disconnecting the house battery and going to the smart charger while camping on shore power?

Jon

OK, I did some more homework. I got Harold Barre's book "Managing 12 Volts" from the library. I also checked Interstate's web site http:/www.ibsa.com/www_2001/content/products/date_codes.asp)
to learn that the battery was made 5/1995. So I guess it lasted a long time. This site has a decent explanation of the battery date codes.

I borrowed the Fluke DMM from work (which measures millivolts).

According to Barre:

OPEN CIRCUIT VOLTAGE STATE OF CHARGE
12.6 or greater 100%
12.6 - 12.6 75 - 100%
12.2 - 12.4 50 - 75%
12.0 - 12.2 25 - 50%
11.7 - 12.0 0 - 25%
11.7 or less dead

The old battery had about 12.0 volts on it, and it dipped significantly with light loads.

Although I would like to have put in 2 6V golf cart batteries as Barre recommends, I decided I didn't have time to get into that project before our week in the 1000 Islands next Saturday. There's not room, and I would probably have to mount them on the tongue.

I picked up a group 27 deep cycle marine battery at Sams Club (Stowaway 27DC-5) for $46.99 with exchange. It's only 95 AH. I was worried that it might not fit, but it fits nicely. Then I realized I could have brought the battery tray with me to check :-(

While I had the DMM, I measured the current draw for several items in the trailer:

roof fan 2A
ceiling light (1) 1.3A
flourescent bathroom light 2A
bath/fridge fan 0.75A each
refrigerator 8.5A
Thetford toilet 4A
water pump 4A (not measured, but from the label)

I didn't have time to try measure the heater fan.

The numbers above will be useful for the "Determine Your Electrical Requirements" section in Barre's book. I will attach my Excel spreadsheet once I figure out how to do so.

The new battery had a solid 12.6V as installed. I needed to add a little water and am now topping off the charge (13.76V last time I checked). No more bubbling.

Last comment- check those date codes when shopping for a battery. Of the batch at Sams, I picked the one built JUL 01. There were some as old as MAR 01. In Wal-Mart, there was one 3-00. A year and a half on the shelf!

UPDATE 8-20-2001

Good news & bad news.

The good news is that we went 7 nights on the new battery after driving 3.5 hours with the fridge on +12V.  We were conservative- 1 or 2 lights on maximum, and only when we were inside.

The bad news is that on the drive home with the fridge on +12V, the battery went so dead that the fan quit running and the test panel wouldn't work.  The battery recovered after a few hours, but I expected the Safari to be charging the battery on the way home.

Need to check some voltages with the Safari hooked up.

The battery recharged OK on 115 VAC.

Our converter is a Magnatek (7345T, I think) that the factory put in while the trailer was being built.  It recharges very rapidly when the voltage is low, then trickles.  The batteries are charge in almost no time when plugged into shore, and the rate of charge from the car is also very rapid.  It is made specifically for people who boondock and want to recharge rapidly, usually from a generator (Generac's are incompatable).
We have two 100 watt solar panels (Siemen's), and never need a generator.  
Is this the same as a smart charger?

On 8/6 we started a camping trip with fully charged battery (~1.270 specific gravity) and cold refrigerator for the UP of Michigan.  Refrigerator setting was on 6-7.  After driving about three hours and an additional 2 hours with the vehicle parked we arrived at our campsite for the first night  The battery was down to about 25% capacity and was not significantly improved the next morning by charging from the converter.  I bought a 2nd battery and box from WalMart and disconnected the original battery.  The new battery  seemed to function fine-no problems while driving and camping at a new site most every night.  But this was in the UP with cooler termperatures (~70).  On the back to Indianapolis, we camped without electricity one night, so the converter could not charge the battery.  I put the refrigerator on gas at the MAX setting to cool things as much as possible for the next day. The next morning I turned the thermostat to the 4 position.  After driving for about 4 hours with the refrigerator setting on 4, we stopped  and took a 2 hr hike at a state park.  When we returned, the van battery was dead.  I was able to start it with a jump from the original RV battery.

I concluded from this that the RV battery does not recharge from the van battery when the refrigerator is running.  To further verify this, I measured the voltage and amp output from the RV battery when the trailer was not connected to the van, when the trailer was connected to the van, and with the electrical connection made and the van running.  The results are given below

                                                        RV Battery only      RV + Van battery   RV + Van running
Fully charged RV battery (12.7v, 1.27 sg),      8.50 amps      3.80 amps      0.95 amps (-2.60  reefer in MAX                                                                                                 amps with reefer off)

Battery at 50-75% charge (12.48 v),                  9.30a, 12.1v      3.60a, 12.2 v      0.45a, 12.32v (-3.60a
reefer in MAX                                                                                             with reefer off, 12.60v)

For whatever reason, my experience is that the battery is not recharged during driving when the refrigerator is on in hot weather.  I plan to have a relay installed to prevent the van battery from draining down when the ignition is off. Based upon the information provided by others, my experience does not seem typical.  Any suggestions?

Junthank:

Check out my "reply #14" under "refer chilling". It might help. Might not.

Mack

Junthank:
I have a '99 Astro. I have yet to narrow down the problem as I have not had time.
I would recommend that you check out the site http://www.surepower.com/isolators.html on a battery isolator instead of a relay (recommended because of problems that relays may have when a bad connection is prsent). They are common in Class A and Class C models to charge the house battery. I know that one can be purchased from JC Whitney for around $70 including the wiring kit (SKU #s 07ZX7612Y & 12ZX9424R).
Please note that the later model GM products have a type CS alternator and a special isolator is required to provide feedback to the alternator. This feedback may indeed be the source of our problems. I am going to put in some larger wires from the isolator (I have yet to buy one, once again too busy) to the connector and also increase the size of the wires on the TM. Our problrm could simply be that the voltage sensing circuit on the alternator is not picking up the low voltage condition on the TM because of too much resistance  in the van's factory wiring harness.

Any one else with any experience with the type CS alternator please share it with us.
Thanks You