Battery not staying charged

[Angoodrich]

The battery that powers the jack won't hold a charge. We bought the trailer a couple weeks ago and parked it in a temporary space at our RV park. Yesterday we plugged it in to our truck to move it to our permanent space and it died when we were lowering the jack. We were told to let it charge with our car running and we did. Still won't operate unless plugged in to our tow vehicle. Anyone know how to fix this issue or should I just take it back to where I got it for service?

[GScott]

Remove the battery (note how it is connected!) and take to someplace that can put it on a tested under load and see if it is still capable of holding a charge. If it is ok, just charge it for a day or so with a good quality charger.

[DanNJanice]

Normally, the battery(s) that run the trailer also run the jack. Are the DC appliances in the trailer working? Was the trailer plugged in to AC? If no, trailer batteries will discharge from what is called parasitic loads in a couple of weeks. Connecting the trailer to a tow vehicle for a few minutes is not enough to charge the batteries.

[GrumpyDad]

Are you leaving it connected for those "couple of weeks" or is ti disconnected (either by removing one wire or with a disconnect switch)?

Also, the battery may not have been fully charged. Especially deep cycle batteries take a lot longer to charge than most people think, which makes sense when you think they power our trailers for a lot longer than "regular" batteries too.

What kind of battery is it? Hold old is it? Does it need more water in the cells?

So many questions.