Help with choosing proper converter amperage

I would stay with the 60 amp unit unless you are planning to enlarge the wiring between it and the battery. Typically the manufacturers use the minimum size wire that they can get away with and the voltage drop would probably limit your charging current to less that 55 anyway.

The larger units would not cause any "issues" but would not provide any increase in value either.

Changing the charger will have no impact on adding the second AC, but if your trailer service is only 30 amps you will not be able to run both at once.

How many batteries? Do you expect a fast charge from a generator? Flooded or AGM?

No effect on the air conditioners unless you are connected on 30 amp.

You are just fine going with the 60 amp.

If you could make a diagram of how the converter is wired to the batteries in your RV, that might be helpful. If you were satisfied with the charging performance of your old converter (that is, you didn't have to spend long hours with the generator to charge the batteries on a regular basis), then 60A should be perfectly sufficient going forward.

It's hard to make specific recommendations without more information about your use, your batteries, how your particular RV is wired up (wire gauges, lengths, fuse or circuit breaker locations and values....), your generator (if any), and so forth.

Sorry I left out so much information.....

The batteries are two lead acid, I believe group 27 typical RV 12 volt batteries. They're condition?.....I'm not totally sure but I do keep them full of water and I leave the trailer plugged in all the time thinking the converter is floating them.

The trailer is a 50 amp service.

I dont know if they're large enough but I want to say the last time I checked the wiring between the batteries and the converter was pretty good size, like either 6 or 4 gauge.

I cant comment about the charging time because I really dont boondock long enough to justify using the Onan 5500 generator to try re-charging the batteries. Plus we're pretty conservative with battery usage overall. Thought about adding a couple portable solar panels to help add time out on our trips but with all the technicalities involved, thats another topic I cant seem to wrap my mind around.

The only times we will power up the generator if we need it for things like watching a movie or running specific high powered items like coffee maker or microwave, etc. I do my best to park in the shade to the AC isnt needed unless its crazy hot outside.

If it'll help I'll figure out the actual wire diagram to and from the converter and batteries and report back.

60 is fine. 30-45 would probably do it too and not be noticed. Doubt you would ever see benefit for spending on 70+.

The cost difference was only around $12-$15 per 10 amp increase over 60 amp. Thats why I was even considering.

2 group 27 batterys is going to be around 180amp-hrs.

The bulk charge should generally be limited to around 25% of the amp-hr number (45amps in your case). A little more isn't a big deal but crazy high 70-90amps, won't charge the batteries any faster and if poor design can damage the batteries.

The bigger issue for you is how will your charging happen. If you won't be boondocking and running the generator to charge...presumably, you will be plugged in for a period in excess of 12hrs. To replace 180amp-hrs in 12hrs, would require 15amps. Of course, you should never use more than 30-50% of the amp-hrs, so even that is a bit high. Going a bit bigger allows the charger to cover 12v loads while still charging the batteries, so 25-30amps should be good.

Now if you plan to start boondocking more and using the generator, putting back something in the 40-60amp range should be fine if it doesn't cost much more.

Also make sure to get a multi-stage charger. As the batteries near full, thier charging needs change and multi-stage chargers do a better job.

With 50amp power, it's probably not a big deal but a big charger can draw a lot of amps. If you are on a 30amp pedestal (no 50amp pedestal available), you may have to wait for the converter to catch up before you can run the air/con.

The additional AC unit has little bearing on battery charging since it is powered by 120V.

There is no problem having a larger amperage converter since the converter is only capable of delivering those extra amps. The battery SOC dictates how much amperage it draws from the converter. In your situation, it will not matter.

Difference between 55 and 60 is 5 amps which in slightly rounded terms is "Less than Ten Percent" In Electronics we more or less ignore "Less than 10 Percent" and consider them to be the same (There are exceptions but this is not one of them)

In short consider the 60 amp PDI to be identical to the 55 amp WFCO in all respects save quality and charge alogarithm (Much better on both) .

How to compute proper size of converter if DESIGNING an RV. (note: once someone else builds it wire sizes come into play,, So use above guide for replacements).

Add up battery 20 hour amp hour ratings (C/20 rating)

Group 24. about 70-75 (73) amp hour
Group 27 just shy of 100 (say 95
Group 29, Just over (Say 105
Group 31 130
GC-2 Pairs 210-230 depending on sub-model (note this is the capacity for the pair, also for each battery but in series you add bolts, not capacity).

Add up your battery bank.. Multiply by 0.30 (30%) and that is your ideal converter size. For a 220 AH GC2 that would be 66 Amps, So you'd use a xx60 converter.