is the convertor supposed to charge the batteries?

Snowman

Thanks for the offer - but no thanks

I have a few of them laying around as museum pieces
Technology has come a long ways
Increasing the operating frequency (60hz to over 100Khz) greatly reduces the amount of iron aka weight needed for similar or in most cases vastly improved performance

KJINTF wrote:
Please do not toss that 7300 series in the trash
Happy to pay shipping costs to get it here
Can always use another bench power supply

Want a Magnatek ferro one? Heavy, so probably not worth shipping?

13.4 volts at 55 amperes makes for a plenty large enough power supply for hotel loads.

Depending on how much boondocking is involved, a 2nd unit designed for multi-stage battery charging could be added. Being autonomous it's output, 100% of it would be directed at battery recharging. For power pedestal hopping, one of these multi-stage "smart" chargers may be enough to maintain a flooded battery at 100% charge. Simply because the ORIGINAL converter has the duty of hotel loads.

As far as heavy cycled extended boondocking that subject has been covered in detail. An Iota or Boondocker model battery charger with adjustable bulk charge voltage limit, and time spent at that limit should help a lot.

And by the way, for the record only SOME of the Magnetek converters used a charging bleed resistor. The later models did not. And the original issue was and is a converter that was factory rated to have a charge maintenance limit of 13.8 volts but in one way or another far exceeded that value.

The WFCO 55 amp unit that was gifted to me is doing a fine job maintaining a rock solid 13.75 volts. Just what I wanted and wildly different than what the factory literature said it would do. Any idiot who would place a 55C ceramic resistor within 1/4" of an equally tall electrolytic capacitor speaks ill of the responsible party - WFCO. Wonder how more little delights these converter chargers possess? Like thermistors incapable of hot re-starts. "Ooooooo you're not posed to do dat....what you mean flicker power outage?" I guess being around Lambda and Sola too many years has spoiled me.

IMHO rig hotel load power supply should be independent of rig battery recharging duties. Utterly isolated from one another. I am seeing more and more high duty solid state DC relays that can serve to switch battery power to hotel power in and out according to need. My rig is going to get one, and yes the relay heat sink is going to be purely convection cooled. The hotel circuit does not include the inverter feed.

Please do not toss that 7300 series in the trash
Happy to pay shipping costs to get it here
Can always use another bench power supply

KJINTF wrote:
I agree the OP has a problem

Which could be the 7300, btw 7300 series do NOT have 50watt ceramic resisters.
That converter can easily be tested and quickly be repaired if defective. Check the 120Vac input and that it outputs 13.6Vdc under a load. If under a load the voltage drops check the 25Vdc 2,700ufd cap under the heat sink and the four current sense resisters. <$5.00 in parts and at most 15 minutes you will be back in business with a nice single stage 13.6Vdc power supply. Lost count on how many of them I've repaired over the years - they make really nice 12Vdc bench supplies.

If not worried about charging your batteries from a generator in a short time the 7300 series is a good single stage converter - just keep an eye on the water level.

That's refreshing ... a voice of reason. Yes, RV converters can charge and keep charged, an RV's batteries.

However, the first converter in our new RV did fail and have to be replaced with a second converter under the RV's warranty. It failed in an unusual way - which may be what the OP is experiencing. Our RV's original Parallax 7345 converter still output 13.8 volts, by at only a very low current load - enough to run some stuff in the RV up to a total current load of around 8 amps. More load than that and the bad converter's output voltage would begin to drop - so much so that the RV batteries were not getting charged - just like the OP's situation.

Our second Parallax 7345 converter has supplied 12 volt power and taken care of our RV's 200 amp hour AGM battery bank just fine for around seven years. Here's some comments explaining why and how:

1) Our eight-year-old AGM batteries are to be floated at 13.5-13.8 volts ... NOT 13.2 volts. It says so right on their label.

2) Our Parallax 7345 output is 13.8 volts ... not 13.6 volts.

3) Our AGM batteries can be boost-charged at 14.4-14.8 volts ... but don't have to be if you don't need the shortest charge times possible.

4) Our Parallax 7345 does not inject noise onto the TV, the computer, or the radio.

5) We generator-charge with the 7345 for around five hours per tankful and can get away with it because the very small generator we use is so quiet and low-frequency sounding.

6) If we must generator-charge quickly or more thoroughly, I use both the Parallax converter plus a cheap Sears 120V battery charger together at the same time with the small generator for a couple of hours to bring the AGM batteries up closer to 90% in just a couple of hours.

7) The no-longer-available Parallax 73XXT series double stage converters seemed excellent for my needs ... too bad you can't get them anymore.

8) I do keep our AGM batteries on the converter for months at a time whenever the RV is in storage ... so the AGM batteries are kept at full charge.

9) The engine alternator easily brings the AGM batteries back to very close to 100% with 5-6 hours of driving. I can see this on the permanent ammeter, as it's current flow into the batteries reading shows a value of zero.

10) We do not drycamp days on end without some driving time between campsites, so on long RV excursions the batteries do periodically get a full charge.

IMHO, the Parallax 13.8 volt converters are not a junk piece of RV equipment (their price is up there right along with other power supplies), they just are not the best for liquid acid RV batteries if the user doesn't know how the converter and batteries are to be used together.

Hi, Anon,

In that case, what is (are) the charging voltages of the 7300? If they are anything less than 14.4 volts, then a better charging source is preferable.

Think about it. Solar controllers do not offer a 13.6v absorption charge, like so many converters do. Neither do portable "smart" chargers. So why does a converter limit charging to only 13.6 volts? It can't be for the sake of the batteries.

thanks all

jrnymn7 wrote:
If it's only to be used as a converter, wouldn't a switching power supply work well for this application? And how many amps max are needed at any given time?

http://www.12voltpowersupplies.us/

Anon, are your batteries and converter close to one another, or far apart like with so many factory installs?

If they're far apart, may I recommend using a power supply as a converter. Charging from the other end of the rig means needing long heavy cable between converter and batts.

they are next to each other. thanks

VintageRacer wrote:
To answer your question, in most installations the converter is used to provide the 12v power to the accessories and lights in the RV and to charge the house battery. If there is no 120VAC power available, the house battery supplies the 12V power. If there is 120VAC available the converter turns on, supplies the power and charges the battery.

I side with those who recommend replacing the old transformer style Parallax with a modern multi-stage converter. The small separate charger can be a good idea for keeping a float charge on the batteries but it's normally too small to achieve the rapid recharge that you want in an RV that may only have power for a couple of hours a day.

Brian

Hi, Brian,

Did you happen to look at the units I linked to? Do you believe these are too small to provide anything over a float charge?

The only thing limiting the size of charger is the wiring to the batteries and the batteries themselves. There is nothing limiting the OP from using a 'larger' charger, next to the batteries, and therefore there is no reason to use a 'small' charger, capable of only floating the batteries.

Let's say the batteries can easily handle a 75 amp charge current. This would require a short length of say 2-4 awg between charger and batteries. But to carry that 75 amps over a much longer distance, would require perhaps 1 or 2 '00'. But if the max draw OFF the batteries is say 30 amps max, at any given time, then the long factory cabling from the batteries to the 12v panel can be a lesser gauge than required to handle 75 amps.

The wiring throughout the rig would be, therefore, limiting the re-charge current to much less than 75 amps, but it would easily handle the 30 amps from the batteries to the 12v distribution area.

A simple (and less expensive) solution:

Install a decent little power supply next to the batteries, as BFL suggested, and have two separate 120v - 12v 'converters' (in other words, power supplies), providing two separate functions; one to charge at a much more reasonable rate, and one to provide real time power.

I agree the OP has a problem

Which could be the 7300, btw 7300 series do NOT have 50watt ceramic resisters.
That converter can easily be tested and quickly be repaired if defective. Check the 120Vac input and that it outputs 13.6Vdc under a load. If under a load the voltage drops check the 25Vdc 2,700ufd cap under the heat sink and the four current sense resisters. <$5.00 in parts and at most 15 minutes you will be back in business with a nice single stage 13.6Vdc power supply. Lost count on how many of them I've repaired over the years - they make really nice 12Vdc bench supplies.

If not worried about charging your batteries from a generator in a short time the 7300 series is a good single stage converter - just keep an eye on the water level.