brand new battery dead

I bought two new Interstate batteries this Spring and they would not hold a charge. Took them back, and after much testing, they swapped them for two good ones. No problems since.

Yes, you should have a multimeter.
If you watch the sales you can get one for free at Harbor Freight. They're not the greatest but it will do the job.

And, just because you have a new battery, it doesn't mean it's not bad.
I've bought things, including two new car batteries, that were bad.
That's probably not the case but, it can happen.

First thing.......

Check that battery cables are connected correctly and not reversed
Don't assume using color of cables...trace cable to frame to ID ground cable.

If connected backwards..swap cables then check converter 'reverse polarity' fuses ( usually 2 30A or 40A fuses on converter). Replace.

IF cables were not reversed then check that converter DC output is at least 13.2V DC with 110V AC input (no tripped circuit breaker)

If you have an inverter check for reset button or tripped circuit breaker on inverter.

Get out your voltmeter and check if the converter has 120vac in and 13.6vdc out.
If you can get your hands on a 10+ amp portable charger and put it direct on the battery it will buy some time while you sort all this out.

There might be a circuit breaker in the lead from the converted to the battery that has a little reset button on it. It could look like this.

If you have a battery disconnect, make sure it's ON. I learned the hard way that, even if plugged in, if the disconnect is OFF, my batteries won't charge.

Lyle

If all is connected properly your 12VDC battery terminals should read 12.6-7VDC when fully charged. Not having an inexpensive multimeter is no excuse. They only cost $7 to $20 from LOWES-WALMART-AMAZOn, and many auto parts stores. Northern TOOLS used to give you one for FREE with purchases back in the day. Don't know if they still do that now or not...

Without shore power ON you should be able to turn ON your trailer ceiling lights which will run from your connected battery.

When you are connected to shore power you should be able to read 13.6VDC at your battery terminals indicating your on-board converter/charger, all connections, in-line fuse, REVERSE POLARITY Fuses, are working normal.

Check to make sure you have the battery connected proper before replacing any blown fuses otherwise they will just blow again. Find the word 'NEG' or symbol '-' on the battery case and make sure the battery cable coming from the trailer frame ground is going to that terminal. Some new batteries from the same manufacturer will have their terminals on the other side of the battery and you can get them hooked up wrong for this reason. Check for the Battery Terminal ID marking first...

These are things I always look for the moment I make changes. No way will I just throw in a new battery and head for the mountains haha...

Not fun showing up with dead battery all of a sudden...

Roy Ken

If you are plugged in to CG power, your onboard charging system should be charging. If not, you can get a charger to hook up direct to the battery, to get by, until your onboard system is repaired/replaced.

Jerry

Sounds like the converter is not charging the battery. Use a volt meter to test the voltage at the battery. If your on board charging system is working correctly, it should read at least 13.4 volts. If not, you have a problem with the converter. Good luck.

Naturally thought the battery would be fully charged when we bought it was a busy week so just hooked it up.

We are hooked into campground power, even after all these years I still can be a rookie. Where would the fuse be or what would be labeled under.

can i charge it by jumping it with my truck or go by a trickle charger?