April to now -- dead battery?

dtake it back where you bought it (if possible).

They should be able tgo load test it and do something accordingly.

If a person has not bought a bad battery in their life they are either young or lucky.

How long was it setting on the shelf before you bought it?
As someone pointed out; They really do build a bad battery on
occasion. Always save your receipt. Take it back. They should replace it no problem. I would bet it is shorted internally. It
happens.

dougrainer wrote:
1. Did your "new" battery start the APU? Does your APU require a 12 volt battery to start it?
2. APU's(gensets) do NOT have a charge circuit. The battery charge is part of the Trailer Power Converter. So, if the battery was low and had enough to start the genset, but the Trailer Power Converter is either defective or the fuse is blown, that means your battery was not receiving a charge and the APU would draw it down as well as anything running in the trailer
3. Slow recharge the battery and then have it load tested. The odds are the battery is OK and the problem is in your Trailer charge system. Doug

1: The battery is on an entry level TT, so there is no APU. I did look into having one installed, and it would have been upwards of $4500 (including fab work to flip the axles and a metal cage for it and a 55 gallon gasoline tank for it.) Instead, I'm using a portable (if you are willing to stretch that word) generator -- a Yamaha 3000iSE to provide power.

2: I checked the 55 amp converter (Parallax Power 7100) while the genset was on, and was getting the normal 13.6 or so volts. It is a single stage battery-boiler (and I plan to trade in the TT eventually, so don't feel like upgrading it), so I watch the water levels and add distilled water when needed. Of course, this doesn't mean that the battery is getting 13.6 volts under load, but that's my tests at the battery terminals.

3: I'm just going to use the dead battery for the core charge. I need more ampere-hours, so I might as well buy two six volt golf cart jars anyway.

I probably should have just pulled the battery and had it sit at home on a Battery Minder, but three months is a bit quick for a battery to sing its swan song.

Long term, the TT is going to get replaced by a motorhome of some type, so I'm not really worried about it, but was surprised to have something go from fully charged to toast in three months, in 90 degree heat.

Something to think about
How hot or cold was it while in the storage place?
Looks like you are from Texas so I venture a guess it's not from -30F weather we have up north, low temps with a very cold discharged battery spells trouble. They tend to freeze solid and crack what a mess they make. Now maybe in Texas it got 130F in the storage area that too is not a good thing for the battery

1. Did your "new" battery start the APU? Does your APU require a 12 volt battery to start it?
2. APU's(gensets) do NOT have a charge circuit. The battery charge is part of the Trailer Power Converter. So, if the battery was low and had enough to start the genset, but the Trailer Power Converter is either defective or the fuse is blown, that means your battery was not receiving a charge and the APU would draw it down as well as anything running in the trailer
3. Slow recharge the battery and then have it load tested. The odds are the battery is OK and the problem is in your Trailer charge system. Doug

mlts22 wrote:
I'll have to doublecheck the brand when I swing by there again. Maybe covered under warranty, assuming I find the receipt..

I was hoping you were going to say 'Walmart'. I would think it would be covered...that's too young.

here is a quote from an article I found at http://rvroadtrip.us/library/12v_system.php "Inactivity can be extremely harmful to a battery. It is a bad idea to buy new batteries and "save" them for later. Either buy them when you need them, or keep them on a continual trickle charge. The best thing to do if you buy them is to use them." It maybe at some point the battery may have been discharged below 11.57VDC and permanent damage may have happend.
Hope this helps some.

I cant seem to get this url link thing to work, can't cut & past

I'll have to doublecheck the brand when I swing by there again. Maybe covered under warranty, assuming I find the receipt.

In any case, time to go shopping for a pair of six volt golf cart AGMs.

What brand of battery?

Well, I had 3 batteries fail me in the last year, Two of them showed evidence of a shorted cell or two.. One just lost capacity and would no longer start the motor.. Check that, it was 4 batteries (I forgot the car) and two that just lost capacity.

How old were the batteries that failed you?