Brandon Sailor
I know threads have been written on this, it's one reason I immediately knew the problem when the battery on my 2017 181b wouldn't charge over 13.3v. Thought I'd put in a little write up about changing my converter. I bought the drop in replacement from bestconverter.com. It's a four stage charger, paid about $150 for it. It was easy to exchange, basically just took off the two screws that hold the panel, then the two screws that hold the lower charging unit and disconnect 5 wires. The electrical board that the large battery wires connect to from the new converter snaps out, making connecting the new wires easy. All of the connections are screwed to terminals except one wire tie. Since I needed a new battery I upgraded to a group 31 AGM. Now just need to add solar and we'll be ready to boondock some. Our trailer has been great, knock on wood this is the only problem we've had. 

Brandon
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2ty
Sometimes a poor battery will cause the converter to sit at 13.2 or so.  This is because, during charge, the voltage goes up quickly and fools the converter into entering the float stage.  This is common with batteries that have sulfated.  Another brand of replacement converters is Progressive Dynamics, they make replacement converters for a range of power centers and include converters for Lithium Iron Phosphate batteries.
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Brandon Sailor
I bought the trailer used last year, it was less than a year old. When I bought it I checked the output of the converter and it was low 13v. Figured it was a good idea to uograde it. 

Thanks
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sunvalleyjoe
I have 2 Interstate batteries and they are 4+ years old. I have checked voltage with both digital and analog voltmeter and got different readings. We have a Interstate factory outside Reno so I called them. I spoke with one of their tech and he told me 13.3 volts was plenty to keep them charged.I went thru our Retro electrical when we first got the unit and found quite a few bad spices and or connections. I worked 45+ plus years as an industrial electrical tech .Most of the equipment was either 24v or 48v dc and found many wiring issues. We have a larger tt with 4 Trojan batteries and have had more issues with them than the Interstates.Just my opinion. The WFCO seems to keep my batteries in good shape and charged.GBA!!SVJ
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Brandon Sailor
Good to know, thanks. I’m not sure why my battery died after a little less than two years. The new group 31 I bought have charging and float voltages listed on it. The charger I bought more so matches that. Hopefully that’ll help with battery life, if not I’ll do some more digging. I haven’t been hard on the battery at all, I I just chalked it up to persistent under charging. The new battery has a 3 year warranty so hopefully if I have trouble I can diagnose it and get a replacement. 
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2ty
13.3v is enough to "keep them charged", but it isn't enough to charge them in a timely manner.  Lead acid batteries also need an 'equalizing' charge periodically in order to bring up the weaker cells, remove sulphation, and re-mix the electrolyte. Equalizing is the 4th stage in charging and requires around 15v applied to an otherwise fully charged battery for a few hours (check water level afterward).
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sunvalleyjoe
one thing I overlooked was Retros grounding wiring.The original ground from battery had high resistance. I removed the ring connector and scraped the paint from the frame. I used a copper grounding lug and ran the ground thru the lug back to the converter.Also found loose wire nuts  at some of the splices they made. I prefer crimp on butt splices rather than wire nuts as vibration can loosen them. If wire nuts are used it is best to tape them.GBA!!SVJ
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