Ferromagnetic charger - how to increase output voltage

[Nick F]

I have acquired an older ProMariner 80 amp charger which I want to use as a manual addition to my inverter driven charge rate when recharging from generator at anchor.

This charger is the old style simple type, massively heavy, and its output is regulated by a tricky system called "ferromagnetic resonance". (I now know because I searched online). There is a separate winding on the transformer connected to a capacitor similar to those used for single phase motor starting.

The trouble is that this charger shuts down too early, because it is designed to "float charge" - there being only a single step in its regulation method.

Here is my question:
How can I change the output so that it does not cut back at, say, 13.6V, but at, say 15.0V? Can I change the capacitance? Do I need to go higher or lower? Would a resistor in series with the capacitance give the desired effect?

Looking forward to hearing from someone from the old days when this was the state of the art!

 

[jungpeter]

Here is my question:
How can I change the output so that it does not cut back at, say, 13.6V, but at, say 15.0V? Can I change the capacitance? Do I need to go higher or lower? Would a resistor in series with the capacitance give the desired effect?

Looking forward to hearing from someone from the old days when this was the state of the art!

Oooohhhh, no. This thing's not even useful as a boat anchor any more. Do yourself an immense favor and abandon it in favor of a modern multi-stage digital charger, such as https://www.fisheriessupply.com/pro...oard-waterproof-battery-charger-2-banks/44012

This advice comes from someone definitely from the old days that has used a ferroresonant charger to hasten marine batteries towards an early death. Don't be penny wise and pound foolish-dump this relic and get a modern charger. Ferroresonant chargers haven't been state of the art since Jesus was an alter boy.

Regards,

Pete

 

[twistedtree]

I know nothing about them, but this looks interesting, if you haven't already found it. https://ustpower.com/comparing-automatic-voltage-regulation-technologies/

 

[KnotYet]

jungpeter has it right. There are good reasons those are no longer the go-to.

 

[Delta Riverat]

Yeah, heavy, inefficient and imprecise.

Did you get it for free?

 

[Comodave]

They would make a good anchor, except they intermittently float…. Get rid of it.

 

[Nick F]

. . . Do yourself an immense favor and abandon it in favor of a modern multi-stage digital charger, such as https://www.fisheriessupply.com/pro...oard-waterproof-battery-charger-2-banks/44012 . . .

Regards,

Pete

Firstly, Pete - thanks for your response.

However, a 12A charger would be of little help.

Secondly, I think that two smart chargers in parallel would make for charge control complications.

More importantly (to me) my marina has a dumpster just for electrical stuff and it has a continuous stock of junked electronic battery chargers - the fact is that they are full of electronics and have a high failure rate. Hence my desire for a low-tech backup. My boat can stand the weight and I have already manhandled it aboard.

I hope that someone can answer my original question!

 

[Nick F]

I know nothing about them, but this looks interesting, if you haven't already found it. https://ustpower.com/comparing-automatic-voltage-regulation-technologies/

Thanks for this. I see that I used the wrong name in my title - it should have been "ferroressonant" and not ferromagnetic.

 

[koliver]

Nick, I too have one of those from the old days. Since I put in a 3 stage Inverter/Charger in 2000. Since then I haven't use the old one much, but it is going back aboard until I find a replacement for the dead 3 stage.
Mine is a ProMariner, 50 amp, with a 13.8v set point.
When in use it kept my batteries up for the first 8 years I had this boat, without killing the batteries. I replaced it because I already had over 100 amps charging from my Alternators, so when on the generator, 50 amps wasted fuel by taking twice as long to charge than by running one engine, andf I wanted an inverter.
Sorry I don't have any answers for you, but I know your electrical knowledge is greater than my own, so I think you will figure this one out.

 

[BruceK]

I had one on my previous 1981 boat, it was OEM, old, and it worked. But, I never left it connected at the marina, preferring to rely on my solar to maintain the batteries via modern multistage regulators. I did use it on the hook, when there to manage it.
My concern was they can keep charging even when batts are fully charged, boiling away the electrolyte and ruining the battery. Nigel Calder supports that, but also says(? inconsistently) they charge to about 75% and then reduce to a trickle, leaving the battery undercharged and liable to sulfate and fail. He also says they cannot be used on AGM and gel types(his book predates lithium).

True they likely last longer than modern multistage chargers but these do it more efficiently,and more safely in terms of battery longevity.

 

[Nick F]

I know nothing about them, but this looks interesting, if you haven't already found it. https://ustpower.com/comparing-automatic-voltage-regulation-technologies/

Interesting link, but it did not have the answer to my question. However, I quote this from it:

"Well known for its longevity, some CVTs are found still in service after more than 40 years. Limited to single phase applications, the ferro is slowly being displaced by small electronic voltage regulators."

 

[Nick F]

I had one on my previous 1981 boat, it was OEM, old, and it worked. But, I never left it connected at the marina, preferring to rely on my solar to maintain the batteries via modern multistage regulators. I did use it on the hook, when there to manage it.
My concern was they can keep charging even when batts are fully charged, boiling away the electrolyte and ruining the battery. Nigel Calder supports that, but also says(? inconsistently) they charge to about 75% and then reduce to a trickle, leaving the battery undercharged and liable to sulfate and fail. He also says they cannot be used on AGM and gel types(his book predates lithium).

True they likely last longer than modern multistage chargers but these do it more efficiently,and more safely in terms of battery longevity.

Thanks Bruce -

I want to use it exactly as you describe (and only that way) - quote "I did use it on the hook, when there to manage it." I agree that modern controlled chargers add safety, but that is a trade off against durability of the charger - and cost.

Regards,
Nick

 

[Portage_Bay]

I agree that the old charger is not worth the trouble to install. It will cook your batteries. Been there, done that. New smart chargers are not cheap but then neither is a new set of batteries. Spend some time reading at marine how to. Specifically Installing a Marine Battery Charger and Choose Your Battery Chargers Carefully.

Regarding the 12A capacity and smart chargers in parallel. Rod Collins, the author of the above articles, says they can be combined. I went with the Sterling he wrote about in the Installing article. Purchased the 60 A model. I may be looking to up total charging to 100 A so would want to parallel a second. Rod has suffered a massive stroke and doesn't need a lot of people asking him questions so I went to Bay Marine Supply where I purchased the charger to ask about paralleling. Here is the part of their response relevant to paralleling chargers

any number of chargers, even of varying manufacturers, can always be connected in parallel to a single battery bank so long as they're all programmed appropriately for the bank and you never exceed the battery bank's maximum recommended charge rate

In other words you need a programmable charger, not just dip switches.

Regarding failure rate of smart chargers. I've had two, one in this boat and one in the previous that were installed by the previous owners many years ago and both still functioning. The ancient Pro Mariner "smart charger" in my current boat is kept mounted and ready to go as a backup. The only reason it won't be paralleled is because it is programmed by dip switches. Perhaps the reason you see so many smart chargers in the dumpster is because that is all that has been sold for a very long time?

Firstly, Pete - thanks for your response.

However, a 12A charger would be of little help.

Secondly, I think that two smart chargers in parallel would make for charge control complications.

More importantly (to me) my marina has a dumpster just for electrical stuff and it has a continuous stock of junked electronic battery chargers - the fact is that they are full of electronics and have a high failure rate. Hence my desire for a low-tech backup. My boat can stand the weight and I have already manhandled it aboard.

I hope that someone can answer my original question!

 

[koliver]

Thanks Bruce -

I want to use it exactly as you describe (and only that way) - quote "I did use it on the hook, when there to manage it." I agree that modern controlled chargers add safety, but that is a trade off against durability of the charger - and cost.

Regards,
Nick

Nick

Just to be clear, I removed my old Ferroresonant charger after 8 years because I was installing an Inverter, that also provided 100 amps of charging power and NOT because it had ever caused any battery failure. And to Bruce's point, I always left my charger on when the boat was in its slip, so, most of the time.

 

[High Wire]

A resistor would only work if there was a sense wire to determine bank voltage. The charger would sense a lower bank voltage and boost the output voltage. But then if it had that capability then it should also have a means to adjust output voltage directly.
Putting resistors or diodes in series with the full output will only lower the voltage and make it worse. Btw you won’t find a resistor that carries 80 amps anyway. Have you looked for a manual for it? Called Pro Mariner?

 

[Nick F]

A resistor would only work if there was a sense wire to determine bank voltage. The charger would sense a lower bank voltage and boost the output voltage. But then if it had that capability then it should also have a means to adjust output voltage directly.
Putting resistors or diodes in series with the full output will only lower the voltage and make it worse. Btw you won’t find a resistor that carries 80 amps anyway. Have you looked for a manual for it? Called Pro Mariner?

Thanks. I have looked for the manual, but it only tells you how to install the charger - no design details.

My idea is that the resistor, if used, would be placed in series with the capacitor (to reduce the effect of the capacitor current saturating the transformer iron ?). I guess I should measure the capacitor current to get an idea of what is flowing there.

 

[Delta Riverat]

I looked these things up last night and they are still being made by more than one company. They do have circuit boards in them now as well as the ferro resonant transformer. They all seem to be marketed to industry for recharging lift truck batteries. The motto is "recharges any battery in it capacity range in 8 hours", nice for shift changes.

They also claimed that it would not destroy batteries, so I have to think that they would avoid having too much voltage/current end of cycle.

 

[Nick F]

I looked these things up last night and they are still being made by more than one company. They do have circuit boards in them now as well as the ferro resonant transformer. They all seem to be marketed to industry for recharging lift truck batteries. The motto is "recharges any battery in it capacity range in 8 hours", nice for shift changes.

They also claimed that it would not destroy batteries, so I have to think that they would avoid having too much voltage/current end of cycle.

I suppose that one could make a "smart" (3-stage) charger using the ferroressonant principle coupled with some electronics to control the current in the extra winding. This would be a "smart" version of what I am trying to do manually.

 

[Turtle Blues]

The drawback to installing a modified piece of equipment is that you can't remove it after the fact if there is a problem (usually a fire). It can be the justification for refusing an insurance claim.
I probably have a half dozen obsolete large battery cookers on the shelf. When the shelf gets full it will worth a few bucks at the scrap yard but I can't see ever reinstalling any of them.

 

[Barking Sands]

If you dont use it dont throw it away. They make good bench power supply. I have a 50 amp one I have been using for years for testing.

 

[Choices]

The "ferro" is used to soften the AC to DC chopper circuit. Without it, a radio pretty much became useless.

Very cheap efficient charger for forklifts and golf carts. Slowly charged so not to get batteries too hot. Could easily cook bad batteries with bad cells.

If you have a golf cart use it in your garage, but it's time has past for being in a boat. There are much better solutions.

New chargers use a much faster chopping circuit to eliminate electrical and actual noise.

They have the ability to sample the battery, pumping current in, and them stopping and measuring current out, in milliseconds.

They can calculate heat into the battery through resistance and current.

These old guys, just made dc.

 

[BruceK]

Used on the hook,I used turn off my ferro resonant charger when the charge amps display dropped close to zero. A powerful charger when operating. Can`t recall brand, not Charles, the other well known old US one.
Pro Mariner is a newer brand, they make multistage chargers,but externally regulating this one sounds a bit hopeful. They were called "automatic", in a way they were, tapering charge as the battery filled but not like the modern ones. I think let it do its thing and regulate with the on/off switch.

 

[Nick F]

. . . . I think let it do its thing and regulate with the on/off switch.

Bruce - the problem is that the charger is set to cut off at a voltage that will never overcharge the battery. So, for limited period charging from the generator at anchor, if it simply "does its thing" it quickly stops charging as the battery voltage soon exceeds the "float" voltage.

What I want is a "boost" switch that removes this voltage limit (or at least increases it to, say, 15 volts). I might even put this switch on a 60 minute bathroom fan type timer.

 

[BruceK]

Bruce - the problem is that the charger is set to cut off at a voltage that will never overcharge the battery. So, for limited period charging from the generator at anchor, if it simply "does its thing" it quickly stops charging as the battery voltage soon exceeds the "float" voltage.

What I want is a "boost" switch that removes this voltage limit (or at least increases it to, say, 15 volts). I might even put this switch on a 60 minute bathroom fan type timer.

Makes sense, the ferro calls it quits too early. Better than "too late"? If you can`t get inside its head, consider a small portable multistage charger to finish the job? C-Tek is a popular brand here costing way less than a big new Pro Mariner, but then you run a genset to power a slower charger. Tried asking Pro Mariner about a way to reprogram it? Be careful it doesn`t charge too high then.

 

[Barking Sands]

-

What I want is a "boost" switch that removes this voltage limit (or at least increases it to, say, 15 volts). I might even put this switch on a 60 minute bathroom fan type timer.

Just putting that monster on a timer to charge a batt bank that is say...40% SOC in order to quickly bring the bank up to 80% seems doable? Then leave the fancy charger to complete the charge cycle if more is needed?

 

[Jc180]

The Ferroreasonant Charger design has a three winding transformer: 1) input, 2) tank with capacitor sized to drive transformer core into saturation, and 3) output winding. Being in saturation, the transformer provides a near constant output voltage over a range of input voltage.Then of course a rectifier circuit to convert output to DC. So the charger output voltage is fixed by the turns ratio of the output winding. Changing the capacitor on the tank winding will only affect saturation and not output voltage.

Anyway, a complicated first paragraph above. But the bottom line is that the charger can not be modified to increase output voltage. Can’t change the transformer output winding turns ratio. Full disclosure, I’m an electrical engineer, long retired, one of the old school, but still remember this stuff.

 

[Nick F]

The Ferroreasonant Charger design has a three winding transformer: 1) input, 2) tank with capacitor sized to drive transformer core into saturation, and 3) output winding. Being in saturation, the transformer provides a near constant output voltage over a range of input voltage.Then of course a rectifier circuit to convert output to DC. So the charger output voltage is fixed by the turns ratio of the output winding. Changing the capacitor on the tank winding will only affect saturation and not output voltage.

Anyway, a complicated first paragraph above. But the bottom line is that the charger can not be modified to increase output voltage. Can’t change the transformer output winding turns ratio. Full disclosure, I’m an electrical engineer, long retired, one of the old school, but still remember this stuff.

Jeff - thank you so much for this! Finally, an answer to my original question! I am also an engineer and understand what you say - which of course unfortunately appears to mean that I cannot do what I was hoping to do. However, I would still like to think about it a bit more.

If I open-circuit the third winding the core of the transformer will (presumably) cease to be in saturation and the control of the output voltage will cease to occur? Could this be a way to achieve what I want?

Thanks in advance for any further insights you can give me.
Nick

 

[Jc180]

Jeff - thank you so much for this! Finally, an answer to my original question! I am also an engineer and understand what you say - which of course unfortunately appears to mean that I cannot do what I was hoping to do. However, I would still like to think about it a bit more.

If I open-circuit the third winding the core of the transformer will (presumably) cease to be in saturation and the control of the output voltage will cease to occur? Could this be a way to achieve what I want?

Thanks in advance for any further insights you can give me.
Nick

You are welcome. To respond to your question: If the transformer is not in saturation, then the output is simply the turns ratio between the input to output windings. If you had a way to modulate the input voltage higher, then the output would proportionally increase.

 

[twistedtree]

It sounds like there is some sort of RC circuit that tunes the saturation point of the transformer? I ask this knowing pretty much zero about Ferro-resonate chargers.

 

[Jc180]

It sounds like there is some sort of RC circuit that tunes the saturation point of the transformer? I ask this knowing pretty much zero about Ferro-resonate chargers.

It’s actually an LC circuit, (the inductance of the winding and the capacitor), but have not attempted to get any farther into the design.