The converter in my camper was an old Magnetek 940, a ferroresonant design that did not do a good job of charging the battery. The max output voltage was 13.6v, which was not bad except for the fact that the regulation was terrible. Under a slight load it would drop down to less than 13v. As a result, the converter would take forever to fully charge the battery after a night of boondocking. For some reason, when running from the generator, the Magnetek put out very little charge current. I wanted something better.
The most bang-for-the-buck that I could find was the Progressive Dynamics PD9145, which I purchased from www.bestconverter.com. It included the Charge Wizard, which is an optional charge-control module which I think is a must buy item. With the Charge Wizard, the converter becomes a multi-stage charger that quickly replenishes a discharged battery (14.4v), then switches to maintenance charge (13.6v) then to a storage mode (13.2v) that does not boil the electrolyte from the battery. Every 21 hours it switches to 14.4v for 15 minutes to desulphate the battery and stir the electrolyte. Without the Charge Wizard, the PD9145 simply outputs 13.6v.
Above is the old converter on the right, and the new PD9145 on the left. I have the wiring connected to the new converter, with a clamp-on ammeter measuring the DC current. The Magnetek weighed probably 30 lbs, while the PD9145 weighs a fraction of that. Wow, better performance and more CCC to boot! (CCC: Cargo Carrying Capacity). The Magnetek had to be connected to a battery before it could be used to supply power, while the PD9145 does not need a battery to act as a power supply.
This project started by removing the old converter, which was behind a panel under the sink. The panel was very easy to remove, Coachmen used tiny headless nails to hold it in (a method used throughout the camper, which is in my opinion poor construction technique, but that is another story...). I disconnected three conductors, the 120v plug and four screws and it was out. I transferred the wires directly to the new converter and tested it out. Then I mounted it as in the picture below. I also mounted the Charge Wizard to the panel under the oven for easy access.
Performance is AWESOME. I put a 20 amp load (all the lights in my camper) on the battery and ran it down for one hour - about 25% of its capacity. (Group 24 deep cycle). I then connected the converter to 120v and measured 46 amps output. Once the battery came up slightly after a few minutes and the voltage stablized at 14.4v, the current began to taper off to about 20 amps. If I turned on any lights, the voltage stayed at 14.4v. Regulation was very good.
The Charge Wizard will keep the output at 14.4v for about 4 hours according to the instructions. It then automatically switches to 13.6v. After a certain time of inactivity, it will switch to a 13.2v float charge mode which the instructions calls "storage mode". This is a low enough level that the electrolyte will not boil out of the battery. The Charge Wizard has a button that allows the mode to be changed manually, and also has an LED that indicates the charge mode while connected to shore power, or indicates the battery level while running solely from the battery. Not as good as a digital display, but ok for me.
The PD9145 has a fan that is almost silent. I thought it was not working, but discovered it was running but very quiet. With a 20 amp DC output, the efficiency that I measured (within the limits of my instrument accuracy) was better than 95%, so very little heat was being generated.
Negatives: Radio-frequency interference while the unit is operating. It only affects the VHF Lo channels (3-5) on my TV set, but I am usually able to orient the antenna enough to get rid of the interference. I will also add that the interference is much less than the electrical noise from a 12v DC fan that I use sometimes. I can live with it. The only other negative is the safety ground connection. A screw terminal fitting large enough to hold 6 gauge wire is used, but a pop-rivet holds it to the chassis. Not sufficient in my opinion. I may drill it out and use a bolt, but I did not want to modify it and void the warranty.
I highly recommend the Progressive Dynamics converters, and highly recommend purchasing them from www.bestcoverter.com.