parallax power supply 7345ru parts PWM

BFL13 wrote:
The 7355 in ours is 10 years old and still going strong. Great converter for when on shore power, but a slow battery charger due to the 13.8v and a long wire.

There is no charging circuit; the batts are just exposed to the 13.8 and you get whatever current the "spread" allows between batt voltage and 13.8--ie not much.

To get full current from the 7355 you can run it as a supply to batteries that are on an inverter which is running a big load. I ran a test of that where the inverter was drawing 90a from the batts as seen on the Trimetric. Used the 7355 with short fat wires to the batts and Trimetric showed minus 34a instead of minus 90a. This shows the 7355 was doing 56a. In its normal location on longer fat wire, with normal battery charging, I see 35 to 40a at most that tapers quickly.

For fast charging to keep gen time down I use higher amp, higher voltage chargers. (Phil, lots of them will do constant amps in bulk while the batts will accept them. PowerMax, Vector/B&D, Paramode, WFCO, Iota all will.

Interesting comments above!

Your mention of a long wire is spot-on. Winniebago installed my 7345 via about 8 feet (estimated - not measured) of 8 gauge wire, so the drop along it while topping up our 200 AH AGM battery bank can be as great as 0.2 to 0.3 volts, which of course gets added to the unfortunate output output sag of the 7345. Slight decreases in what a charging battery sees being forced onto it's terminals from a power supply can really slow down it's charging rate at certain points in the battery's charging cycle. I've fit samples of larger wire sizes into the terminals of the 7345 and found that it's terminals can probably take a wire as large as 2 gauge, so I should replace the 8 guage run between it and the batteries with a 2 guage run "one of these days". (My AGM batteries have, for almost 7 years now, reduced the urgency in doing this.)

Your comments on "forcing" a 7355 to full current output through use of an inverter to really drag on the main battery bank is enlightening. That means that the 73XX family of converters can indeed actually supply their full advertised current if conditions are right. Unfortunately, a partially discharged RV battery bank sitting at 12.1 volts isn't going to get/take that kind of current because of, as you say, too small of a voltage spread (difference) between 12.1 volts and 13.8 volts. That's the real reason that multi-stage chargers do better at charging than fixed 13.8 volt converters ... because of the high voltage range that's available on the multi-stage units. Also, that's why the Parallax 73XXT converters would have, in my opinion, made way better converters for motorhome use. It's too bad that Parallax discontinued that model line.

So .... regarding (affordable) chargers being able to supply full advertised current while maintaining full advertised voltage on their terminals .... are you saying, for example, that a 55 amp PD charger will measure around 14.4 volts right on it's terminals while a current meter is simultaneously reading 55 amps flowing out of it? If so, I apologize for my skepticism and will update my knowledge base. I might even have to revisit purchasing of a temperature compensating Paramode RV charger ... assuming of course that it can maintain full current at full voltage. ;)