12 Volt Battery Choice

[Thane]

My trailer seems to be a battery eater. I've had three Interstate SRM-27 lead acid batteries in six years. Here is a link for an example:

http://www.interstatebatteries.com/c...ement++battery

I keep it charged and level checked and top it off with a Honda 2000 when bookdocking so it has been resonably well teken care of.

Anybody have better luck with a battery?

[cpaharley2008]

I assume they have been replaced under warranty, otherwise I'd go with AGM.

[Jim Bennett]

I am on my 4th year with my dual 6V batteries, and they appear to be holding a charge real well. I do nothing special but keep them charged as often as possible, and check acid levels once or twice a year. I do leave them in the trailer over winter, but put them on to charge once or twice over the 6-7 months.

That does seem like a way too short of life if you are caring for it.

[Thane]

Two were replaced under warranty, one died at 35 months. The trailer puts about 16.5 volts across it for charging when weak.

[hippo]

If you are near a Costco Warehouse check out their RV Batteries with 100 month warranty. Bought one in 2009 the battery would not hold a charge took it in got 100% credit for it and bought another one same size zero cost out the door.
chuck

[escape artist]

Hi: All...We're still on our original battery from '07. Are we doing something wrong Alf
escape artist N.S. of Lake Erie

[fudge_brownie]

What about your discharge level? If you frequently take your battery below 50% before recharging you will shorten battery life. With your generator I doubt this is the case but thought I would ask.

[cpaharley2008]

Originally Posted by Thane

Two were replaced under warranty, one died at 35 months. The trailer puts about 16.5 volts across it for charging when weak.

That voltage seems kind of high, I thought 14.5 was the desulfication mode and 13.6 was normal. You may be boiling away you acid.. Check your converter output spec's.

[float5]

Thane, I don't know what you mean about 16.5 and weak. We have been told that 16.5 is dangerously high. Normal when using the trailer is 13.6 as far as we find.

I don't know what low is and when someone needs to start charging with a charger though. Maybe someone can comment on that.

[cpaharley2008]

here is a chart, notice the range from 11.90 to 12.6, with 13.6-14.0 the highest for bulk or desulfication.
Here is a link for some reading also http://www.marxrv.com/12volt/12volt.htm

[float5]

Jim, thanks for the info. It is often stated that the batteries should not be allowed to fall below 80%. Just to clarify, the chart tells the state of the batteries but the accompanying article says to charge when below 80, not down at 40, as someone might think looking at the chart.

What I have also seen elsewhere is that the batteries should be down quite a bit before charging. If only down 5%, for instance, it would actually be harmful to charge at that point. In other words, topping off when unnecessary can shorten the life of the batteries.
I don't remember the scientific explanation for that but I think the layman's explanation might have been that they will get a lot of crud on them if you charge too soon!

[gbaglo]

Not sure how one would ensure one wasn't charging prematurely, unless you disconnect the battery every time you tow or plug in at camp.

baglo

[Thane]

Thanks for the Costco tip. RV and marine batteries aren't shown on their website so I'll go to the store next week to see what they have.

The battery fault was confusing. It was our second day boondocking but the battery charge was high as I charged the battery while making breakfast. With the fantastic fan and lights on, everything was fine but when the water pump was turned on the battery went dead with seconds.

I checked the battery and it was showing 9+V so I started the Honda generator and measured over 16V during the first minute or two of the charge cycle. I let it charge for an hour or so and then checked the battery voltage and specifc gravity with the generator off and all cells showed good charge.

I then turned on everything except the pump and everything was fine. I then turned off eveything and turned on the water pump and one light and within seconds the battery was dead and the propane detector low voltage warning was sounding off. The light was very dim.

I recharged the battery and repeated the process.

The battery charge is now 13.5 or so with the trailer plugged into a wall socket at home. Maybe the battery fault reduced amp flow and increased the applied voltage from the charger during the first few minutes of the charge cycle.

I checked amp flow and wire harness temperature during these events to make sure I didn't have a trailer problem. The amp rate was reasonable and the wires didn't get hot so it an internal battery problem, not a trailer problem. This was a relief as I had changed the trailer wiring quite a bit and was concerned that maybe I introduced a fault.

Thanks for the info on the other posts.

[float5]

Baglo, if you are plugging in at camp then you shouldn't need to worry about doing any extra charging. I believe that info is referring to the use of a 3-stage charger.
When a generator is introduced, however, I have no idea what that situation should entail.

You, Thane, and others who plug in at home might want to have a good look at the article Jim mentioned or other similar ones. Off of the top of my head, I seem to recall that you can cause the batteries to go dry unless you disconnect the converter or do something else to prevent that. We can have no such situation as we are in storage with no electric available and our readings are at fully charged. I expect we will only be charging in winter but many people have a habit of charging at home, which can do damage I think.

Of course, these people write these articles as if we all go around constantly testing our batteries. I note that one instruction said not to test for hours after being completely disconnected, maybe 6 hours. It is all interesting to read. Just not sure what it all means.

[gocamp]

Thane, I didn't understand what the cause was for your three batteries. Are you saying it turned out to be water pump? Thanks.

[Thane]

I dunno why my trailer eats batteries. I went through 3 batteries in six years and was interested in what sort of 12V batteries other folks are using.

The latest battery fault was just odd. I think it has an internal fault that only manifests with the high load provided by the water pump. The water pump is fine and I don't think it is the cause of my woes. Maybe I just had bad luck with the first two batteries. The third lasted 5 months past warranty.

[gocamp]

Ok I see, yes, very strange indeed then when you think about Al and his original battery from '07. Another idea is ask on other more popular rv forums. Might get more feedback there. Good luck.

[cpaharley2008]

Water pumps normally pull 5-7 amps per hour but you normally do not run them more than an hour per 24 hour period. Do you have less and other battery saving devices installed?

[GaryH]

Is your battery well fastened & not bumping around? Being jarred can shorten it's life as well. Here's a good site to answer most of your battery questions. Note that going just by the current/voltage charge is dependent on the ambient temperature.
http://www.batteryfaq.org/

[Thane]

I don't remember the amps pulled with the water pump, it wasn't much. The 12V refer also drains the battery within minutes.

The battery sits pretty snug in the stock battery box on the rear bumper. I have extra battery straps but perhaps a rubber shim on two sides would snug it up more.

We use the trailer a moderate amount and take reasonable care, so maybe a longer than 30 month warranty battery is the best I can do.