parallax power supply 7345ru parts PWM

[Cstoliker]

My 7345 is not charging the coach batteries but does supply 12power to all accessories. The transformer, fan and relays work fine.
Think i need a PWM circuit for it. Contacted PP tec support and they seamed more interested in selling me an upgraded replacement unit rather then parts to fix this one. Anyone know of a way to get a PWM for this? (Charging controller)
It's a retrofit from an original Magnetek 6345 wich was serviceable. Parts were available and the schematic is even available online. Unfortunately the 7345RU has non of theses things except for a "flow chart" and "installation instructions".

Or even if someone know enough about these to tell me how bypass the PWM and get full output to batteries. I'm not going to leave it plugged in but I'd be nice to be able to charge my batteries in a couple hours running off generator..

[pnichols]

MEX,

As you may be aware, even Einstein was confused. The best he could do about understanding Quantum Entanglement was to call it "spooky".

Very similar to the situation as to why the Parllax 7345 won't hold ~13.8 volts while delivering 45 amps.

[KJINTF]

Sorry I don't really understand the question
There should be 5 resisters in parallel
the right side is a trace that goes to Q13
the left side is a top side trace "+"

Hope this is of some help

Check out the linked thread for Sal's modification there is a schematic JPEG attached to one of the repsonses toward the end of the thread. It's a Partial fix at best at best not really worth the effort IMHO

[Cstoliker]

Kjintf:
This is a photo from the under side of the resistor pack. Tested continuity from right side to nearest point an it's ok.
The left side however I'd NOT connected to the connection on the lower left (circled).
Should here be a connection there? If not I don't see where the resistor pack should connect to.

[Cstoliker]

Salvo.
Can you please enlighten us as to the mod you did on the 7345.

Is the a way to ge the 7345 to to go into full output by way of bypassing,modifying or tricking the sence circuit? Perhaps something that could be installed on a switch as "turbo mode" or something..


Yea I know it could fry the batteries, but if I could get 14 volts to em for an hour it would be great.

[MEXICOWANDERER]

DON'T-CHA JUST LOVE CONFUSED ENGINEERING?

[BFL13]

"I would prefer a 7345 output stage that kept the voltage on it's output terminals very close to 13.8 volts with 45 amps flowing ... like some in this thread say that certain other RV power supplies will do."

Phil, you missed my earlier point.

What happens so far as I have seen, is that the charger is only at max VA for an instant. All during the time it is at constant amps, both battery and charger voltages are rising till converter voltage reaches the high set point where it trips over to letting amps taper.

It does not put out full amps while at full voltage except for that one instant at the top of the rise. EG Vector 40a trips at 13.9v so at that moment it is at 556w. Just before that it was at 40a and 13.8v = 552w. Just after that, voltage keeps rising but amps fall, so you see 14.1 and 38a say, =536w

I have seen on here that people like Salvo expect the charger to be at full VA right from the start and the theory is that the PD converter can't do that while the others can. I don't have a killawatt to measure the actual VA draw of the charger for the whole of Stage 1. I don't know how it keeps its own voltage ahead of rising batt voltage as shown in the ugly graph earlier. All I know how to do is multiply the output amps by the charger voltage, so that is where I get the max only for a moment at the top.

[pnichols]

The drop in the 7345's output with each LED being turned is not important in itself ... it's just an indication of a less than desirable overall output stage voltage control design and performance, IMHO.

I would prefer a 7345 output stage that kept the voltage on it's output terminals very close to 13.8 volts with 45 amps flowing ... like some in this thread say that certain other RV power supplies will do.

For instance in my situation, charging of my AGM batteries would be even faster with my non-boost-voltage 7345 if it's output would, say, remain no lower than 13.7 volts when dumping 40 amps into my AGM batteries. Remember ... I'm talking about voltage right on the 7345's terminals that it's manufacturer had control of via it's design.

Keeping voltage drop (sag) low between the 7345's terminals and the batteries' terminals is a whole other situation and is completely under my control and is my responsibility to take care of. I just want the 7345 to do it's thing a bit better without me having to spend a bunch of additional $$$ to replace it.

I may have to do what MEX and Don do - use a simple single-stage high voltage charger that I already own in parallel with the 7345 in order to get some high currents dumping into the AGM batteries during the early stages of their charging. I have plenty of other things to spend our money on besides replacement of a 7345 that is supposed to be almost adequate for my wheel chair deep cycle battery bank.

[Salvo]

Again, that's just an IR drop within the converter. The converter has a series resistance of about 4 mohm that's outside of the regulation loop. 4 mohmn is on the high side, so in addition to wiring and trace losses, there may also be an emi filter involved.

If the 73xx has a similar internal line drop, then Phil should be seeing a drop of 0.004 ohm * 0.2A = 0.8 mV drop at the converter when turning on a led light. That's extremely insignificant.

Sal

BFL13 wrote:
The Paramode 4455, a follow up to the 7355 in the product line, has these voltage curves which show the sag under load.

https://bestconverter.3dcartstores.com/assets/images/Parallax/4400/4455%20Voltage%20Curves.pdf

[pnichols]

KJINTF wrote:
Too many chores today, fishing tomorrow ...

I hear ya!

We're right now staying with the BIL in his house right on a little bay just off Puget Sound. The DW brought in a 16 lb. salmon last night for a quick fish after last night's dinner - we'll BBQ some steaks off it late this afternoon before trying for some more this evening. The boat's hooked up to the dock right out in front.

We're DEFINITELY not camping now ... the RV is back in CA with the converter hooked up to the AGM batteries ... hopefully not boiling out any H2O from them in the CA heat.

[KJINTF]

Happy to do a test later - maybe Sunday

Too many chores today, fishing tomorrow - Highest priority right now a Pack Rat that needs to be eliminated

Have a few 4 digit and a 6 digit DVM that should see what happens

[pnichols]

KJINTF wrote:
There might be another reason for what you're seeing - Just guessing

My converter is about 6 years old and has always acted that way. It can deliver high currents ... the only issue is that when it's doing this the voltage on it's terminals is below 13.8 volts (maybe up to 3/10 ths of a volt below at times). 3/10 ths is a lot when trying to bring up my AGM batteries during early stages of their charging.

My quick and dirty LED light sag test, IMHO, even more dramatically illustrates my 7345's sloppy, or non-existant, voltage control ability. Dropping 1/100 th of a volt lower with every LED I turn on seems strange to me - but this in itself is not really important. It's the few tenths of a volt drop during boost stage battery charging that is most important.

I wish someone else here would use a four-place digital voltmeter (a three-place meter does not have enough resolution) on their 7345's terminals while turning ON one LED light at a time to check how closely the output circuit can maintain output voltage under very small incrementally increasing LED currents.

[pnichols]

BFL13 .... thanks.

Then I stand corrected (again) ... modern Chinese manufacturing costs can in fact deliver chargers to the U.S. RV market that at the same time deliver both high currents and non-sagging high voltages ... that us retired folks probably can afford. :C

(So far however, my AGM RV batteries don't require that combination.)

[KJINTF]

pnichols

There might be another reason for what you're seeing - Just guessing

Over the years I've had many dozens of them apart - most showed issues with voltage regulation under a load - all had the resister network issue we discussed and the small cap defective, many had the large front end caps defective - Just guessing here yours might be in the same boat - Just guessing......

How old is your converter?
Can you get it to give you full current at the specified voltage?
Try loading the battery with an inverter and some 100wat bulbs or similar

Like you I have LEDS the only way for me to draw lots of current is the compressed air system or the inverter with bogus loads like 100watt bulbs, which are no loner available

[BFL13]

Off-topic warning----

"By the way, do you have data yet proving that other (reasonably priced) RV chargers in their boost modes in fact are holding 14.XX terminal voltages under heavy currents?"

I posted that they all do except for the PDs, which taper right away so you get 75 from an 80 and then the 75 tapers a bit before going into the big taper once the battery gets up, same as the others do.

The difference is the others hold constant amps at their current limit rating (or a few more amps than that if on short fat wire)

I have posted several ugly graphs showing this for my Vectors, Paramode, and now my PowerMax. Others have posted graphs showing their Iotas and WFCO (when behaving)

However, careful wording is required. The constant amps Stage 1, is when the battery voltage is rising from 12.x to 14.x and the charger is keeping ahead of that by 0.2 or 0.4 volts to maintain the spread.

Once the charger's voltage reaches threshold set point, that voltage is held (except with the Vector) but amps then taper so watts fall off. The highest watts is just before amps taper, when charger voltage has just reached its max and amps are still at current limit. One minute later, amps have fallen so VA is lower. I have observed this using my Vector with a watt meter going, where its draw fell off quickly. This is what allows you to use your gen for something else after amps taper enough.

The Vector exception is that amps taper when batt voltage reaches 13.9 so that is the max watts point. But after that, while amps taper, voltage keeps rising to 14.6 or so.(but VA keeps declining) This keeps the amps up higher while still tapering within the battery natural acceptance rate at the voltage.

Iota converter gets to 14.8 with the initial stage and that gets battery to 14.6, which is the trigger for converter voltage to drop to 14.2 and hold there while amps taper. This is supposed to be more gentle than staying at 14.8 till batts are full.

Not going to fight with tinypic to show all my graphs again, but will add one if I can do it with no hassle 😞

OK here is one showing the charger holding "100 amps" (actually a bit more) in Stage 1. This charger is set to hold the absorption voltage constant after it gets there, and the battery eventually catches up.
-------------
Camping again in cooler temps, so this time I used Mark's temp comp table that says 14.7v is 15.17v at 42F. I set the voltage on the 100amper at 15.2v and charged away to see what happens.

Bank of 458AH (four 6s) est 15% down so calling it 389AH full, and was at 53% start based on Trimetric AH count and battery "morning voltage"
26% charging rate so tapering at 66% SOC is about right. At 23% rate it tapers at more like 72%.

(charger voltage "hunts" a bit at the high end so I showed the range up and down to represent that--it is a rapid action on the voltmeter. Seems to be how it works, so no problem, just a curiosity. )

[MEXICOWANDERER]

CHEAPNESS

MEET THE KING!

ME!

I use the word as a compliment. Anyone can throw money at a problem, or better yet pay someone else to throw money at a problem while they "go to the club".

I wasn't joking nor was I sarcastic when I recommended the Harbor Freight 10-amp charger. It will add 18 amps charge rate when the batteries are low. Try that with any other $29.99 on the market.

Meanwhile anyone else who gets offended at my use of the word cheap can get out of my tree-house club meeting for AUTHENTIC cheapskates.