Guest Ferroresonant Charger

[PaulM]

I have a Guest Ferroresonant Charger (2515C) that charges 2, 125ah, size 29 batteries with one Battery on each channel. I started noticing that the #1 battery was having trouble starting the engine. Water was check monthly and was fine. It finally failed completely and had one dead/dry cell. The #2 battery is fine. I checked the voltage from the charger with the batteries disconnected and was surprised to find that the voltage was 15.9 and 15.8 respectively. Is my charger toast? If it needs replacing, I was going to get an Iota 30 w/IQ4. Is this the correct size?

Paul

[David M]

If your charger is reaching 15.9 volts then yes, its toast. Replace it before it starts destroying not only your batteries but your onboard electronics. Buy a new non-ferroresonant three stage charger with multiple terminals, one for each battery bank.

Your batteries will thank you for it.

[jdoe71]

I believe that ferroresonant chargers are "dumb" 1 stage chargers. Likely it is not defective it is just doing what it was programmed to do. We had a Promariner ferroresonant charger aka "battery boiler" that ran at 15+ volts continually, replaced it with a new 3 stage "smart" charger. Was money well spent.

[Viking Sailor]

Ferroresonant charger voltage should be checked when connected to a battery and should be around 13.8 volts. Also, multimeters have been known to be off by a few tenths of a volt.

Replacing the old ferroresonant charger with a new 3 stage charger/monitor is a very good idea.

Paul

[GordMay]

The ferroresonant charger is a simple & robust device, basically consisting of: a transformer, a capacitor, one or more diodes (rectifiers), and some wires and terminals.

The charginbg voltage of the ferroresonant charger is essentially constant throughout the charge period.. The output current, however, is limited by the battery voltage. At the beginning of the charge, the battery voltage is considerably lower than the charging voltage, and the maximum charging current flows. As the battery is recharged, its voltage increases, gradually reducing the charging current to the finish rate.

If the fault is in the transformer, the unit is not likely worth repairing.

If the problem was a failed diode, you may be able to find a reasonably-priced replacement.

However, unless the charger was very seriously overloaded, the problem is most likely in the capacitor - a $10 fix. The capacitor must be designated as a “motor-run” capacitor, not a motor-starting capacitor.

Without the capacitor, a basic ferroresonant charger changes its output (charge) voltage with variations in input voltage. The capacitor causes a current to flow, that induces a strong magnetic field in the core. The resulting "saturated field” condition then stabilizes the voltage on the winding that provides current to the rectifier diode(s). The result is a constant output voltage, even when the input voltage varies over a reasonably wide range.

Testing the Capacitor:
Connect a DC voltmeter to the output, and apply AC power to the unit.
Note the DC voltage.
Disconnect the AC power and remove one wire from the capacitor. Apply AC power and check the DC voltage.
A lack of change in measured DC voltage is a pretty good indication that the capacitor is not working.
Disconnect the AC power and substitute the new capacitor for the old one (only two wires are involved). Reapply the AC power and connect the output to both a voltmeter and a 12-volt lead-acid battery (the battery must be connected for the voltage to reach the correct value).
If the problem was the capacitor, the DC voltage at the battery will be very close to 13.5 Volts (13.2 - 13.9V), if the battery is reasonably well charged.

[Alan Wheeler]

Ferroresonant simply means it has a Transformer. Many chargers has a tranny. What sepperates the good from the bad for marine purposes (leaving regulation aside for the moment) is in the way they are Earthed. I believe Guest make a reasonable Marine FeRes. charger. Wether your one is such a charger I don't know, you don't say what model. However, three and four step chargers are certainly far superior to the old regulated chargers of yesteryear. 15.9V may not mean a faulty charger however. For a non regulated charger or even one with simple regulation i.e. trickle charge, 15.9V can be measured if no load is connected. For a more sophisticated charger, Acceptance charge can be in the 15V range and it is possible your meter is not highly accurate. If you have FLA batteries, over charging is easy to spot. They will be hot, the liquid will need constant topping up and the tops are often wet and you will hear excessive bubbling.

[GordMay]

Ferroresonant Transformers are a special type of laminated saturating transformer which provides a regulated output.*

These are sometimes known as Constant Voltage Transformers (CVTs). Using a special magnetic structure and a capacitor, ferroresonant transformers can supply a well regulated output, voltage which remains constant despite changes in input voltage and load. The ferroresonant approach relies on the square loop saturation characteristics of the tank circuit to absorb variations in average input voltage.

Older designs of ferroresonant transformers had an output with high harmonic content, leading to a distorted output waveform. Modern devices are used to construct a perfect sine wave. The ferroresonant action is a flux limiter rather than a voltage regulator, but with a fixed supply frequency it can maintain an almost constant average output voltage, even as the input voltage varies widely.

They offer high isolation (filtering), and short-circuit protection (current limitation).

Minimum maintenance is required, beyond frequent replacement of failed capacitors. Redundant capacitors, built into some units, allow several capacitors to fail between inspections, without any noticeable effect to the device's performance.

* “Ferroresonance” is a phenomenon associated with the behavior of iron cores, while operating near a point of magnetic saturation (where the core is so strongly magnetized that further increases in winding current results in little or no increase in magnetic flux). While being somewhat difficult to describe without going deep into electromagnetic theory, the ferroresonant transformer is a power transformer engineered to operate in a condition of persistent core saturation. That is, its iron core is “stuffed full” of magnetic lines of flux for a large portion of the AC cycle so that variations in supply voltage (primary winding current) have little effect on the core's magnetic flux density, which means the secondary winding outputs a nearly constant voltage despite significant variations in supply (primary winding) voltage. Normally, core saturation in a transformer results in distortion of the sine-wave shape, and the ferroresonant transformer is no exception. To combat this side effect, ferroresonant transformers have an auxiliary secondary winding paralleled with one or more capacitors, forming a resonant circuit tuned to the power supply frequency. This “tank circuit” (Resonant LC Circuit) serves as a filter to reject harmonics created by the core saturation, and provides the added benefit of storing energy in the form of AC oscillations, which is available for sustaining output winding voltage for brief periods of input voltage loss (milliseconds' worth of time, but certainly better than nothing). (see below)

[stevedave28]

To GordMay - I can see that you've done your homework! - I'm very impressed - I am a professional industrial battery and charger tech and you have a better grasp of this concept then some of the engineers I've talked to that design these chargers (LOL). One interesting thing to note that ISN'T very well known is that capacitive resistance also comes into play when the battery approaches the finish rate due to this circuit being one large feedback loop. Not an exact science either. The "ferro" portion of the name is taken from the ferrous metal core that the transformer is made from - the "resonant" portion from the resonant choke that is combined with the transformer - these ARE solid dependable chargers but not very efficient due to most using a half wave rectifier - the good ones use a full wave bridge rectifier (the previous CAN be upgraded by simply adding the proper power diodes {usually}) - at most though, they are about 60% efficient (full wave bridge rectifier) - then came SCR (silicon controlled rectifier) chargers using an IGBT (insulated gate bipolar transistor) - better efficiency at first but due to increasing SCR leakage over time (due to the component degradation of the IGBT) the accually become less efficient than the ferros (some times even the half wave ferros) - BUT they are highly configurable and allow for highly precise charge curves and specialized maintenance cycles and such - SCR chargers typically start with AC then rectify it to DC then send it through the IGBT which converts it back to AC and then finally back through a second rectifier to get DC for the output stage - note that this is an extremely simplified breakdown to show the rectification process - this is also why when a buddy brings me a high freq marine charger it turns out to be an SCR as they can simply drop out the first stage rectifier to simplify the circuit - be warned that they are considered a high frequency charger (usually 200 to 450 kHz range) but are nothing like the newer high frequency chargers (as I'll go over) - by far the most efficient charger on the market are the new high freq chargers - they are also by far the most complex - the are more configurable but as they are a new tech they are going through some major growing pains - they typically run at about 85%+ efficiency (and to note - charger efficiency is the amount of power that the battery uses compared to the ammount the the charger uses - so 85% means that the batt used 85% of the power that the charger used and some of the ones i deal with at work are 96% efficient (they are the most efficient in the world)- so ferros typically waste as much or power than the batt used to charge - the new high freq chargers typically run at 20 to 50 MHz but they are a PWM (pulse width modulation) based, switch mode power supply (same kind of power supply as in you PC) driven charger - an EXTREMELY important fact about these is that they pulse (hence the name pulse type charger though again some SCRs are too but still not the same) the current through the batt only giving it what it can absorb at the rate of absorption hence the efficiency - of all the chargers that I've worked with (and that's A LOT) Hawker and Enersys are by far the leaders (Enersys owns Hawker) - hawker has a charger (it's industrial so pricey) model lifeplus mod1c thats modular and would hands down be the best option for a land based charger if you are in the states - anywhere else and look to enersys as they are global - this charger does it all from an ionic charge cycle (patented and hands down the best on the market - when used properly it can extend the life of the batt by 20% and it works) to programable maintenance cycles to logs and even a batt ID device compatability and soon to have network capability (again - this is an industrial charger but its a smaller one designed to charge small deep cycle batts which are also known as small industrial batts) never seen them in a marine environment but i can tell you that all of the boards are conformally coated and they are the easiest to work on of all the chargers i've delt with plus have jaw-dropping circuit protection - VERY IMPORTANT for all chargers is that you never disconnect the battery while it is charging - it WILL damage the batt as well and the output rectifier and main board (typically where the micro controller is located) causing 99% of the failures I see

Now for batteries - the number one killer of a battery is temperature - anything over 110 F or under 60 F will damage your batt - the sweet spot is 77 F - when you charge pop the caps and it will allow maximum heat ventilation as well as hydrogen (extremely explosive) ventilation - lead-acid batteries use 2 volt cells and when the cell gets to approx. 2.37V it will start to gas - this is where the batt takes most of its charge and where you lose most of the water - the water evaporates, not the acid - so low water equals high acidity which will damage or disintegrate the plates - short cycling the batt will lead to acid stratification meaning the acid is settled in the bottom which disintegrates the plates from the bottom up - a battery should never be discharged more than 80% from a full charge (known as 80% DOD {depth of discharge}) as it can reverse the polarity of the plates which is irreversible - never water a dry battery - it WILL explode, literally - and never water a dead batt - now a quick pro tip if your water is below the plates on your dead batt only fill it to the top of the plates before charge - as a batt charges the plates release sulfate (SO4) swelling the water level - as you discharge it the plates absorb sulfate - this is how a lead-acid batt works (mind you that this is highly simplified) - proper water level also minimizes available airspace in the cell for hydrogen to build up minimizing the risk of hydrogen ignition as well as severity of hydrogen ignition

I'm going to stop there for now as this was about chargers but I've allowed messages from members so if you want a far more detailed breakdown of any of this then simply ask - I should probably add that I am a USAF trained electrical engineer with a strong background in chemistry to boot - smooth sailing and enjoy some waves for me as I am currently stuck in southern IL

[senormechanico]

Originally Posted by PaulM

I have a Guest Ferroresonant Charger (2515C) that charges 2, 125ah, size 29 batteries with one Battery on each channel. I started noticing that the #1 battery was having trouble starting the engine. Water was check monthly and was fine. It finally failed completely and had one dead/dry cell. The #2 battery is fine. I checked the voltage from the charger with the batteries disconnected and was surprised to find that the voltage was 15.9 and 15.8 respectively. Is my charger toast? If it needs replacing, I was going to get an Iota 30 w/IQ4. Is this the correct size?

Paul

It is not toast, it's A TOASTER ! Lead acid battery voltage under normal circumstances should never reach that voltage.
There are lots of threads here and all over the net which will tell you what you need to know.

Back in the day, those chargers were known as "The Endless Hummer"..
For those of you non old farts, that is a reference to a movie called, "The Endless Summer".

[GordMay]

Greetings and welcome aboard the CF, stevedave.

[boatpoker]

Terrific stuff from GordMay and SteveDay 28.

Let me translate for you ...... Get rid of it

[GordMay]

Originally Posted by boatpoker

Let me translate for you ...... Get rid of it

I still have an old 1980s model on my (unused, these days) test bench. Formerly used as a power supply.
Otherwise, you're right!

[hellosailor]

Hear hear! Let's wait another four months, so we can say this is a TEN YEAR OLD post and thread being replied to. Hoping the OP got it solved nine years ago. (G)

[boatpoker]

Originally Posted by hellosailor

Hear hear! Let's wait another four months, so we can say this is a TEN YEAR OLD post and thread being replied to. Hoping the OP got it solved nine years ago. (G)

What's your beef ? The info is still valid.

[foggysail]

The only thing I find interesting to add is the ferroresonant transformer is extremely sensitive to the line frequency. This can be important when the device is powered from an AC generator whose frequency might be off a few cycles and a few cycle do matter, big time.

Incidentally, ferros are also used or at least were also used in microwave ovens. In this particular case they were configured as constant current transformers rather than constant voltage. The reason for constant current in ovens is that magnetrons which are the heart of micros have a very low input resistance once the operating voltage reaches the level for the maggie to begin conduction.

The constant current transformer can output very high voltages in their attempt to provide constant current. This feature is ideal for magnetron loads.

Back to battery chargers. I highly recommend modern 3 state chargers over the ferros. The charging current is limited in both cases to (V1-V2)/Rload where Rload is the battery equivalent input resistance. V1 is source voltage and V2 battery voltage which increases as the charge increases. In a ferro, V1 is fixed so the charge current quickly diminishes. Not so with modern chargers where V1 varies depending on the state of charge...bulk, absorption and float.