Onboard mains battery charger giving 15.8v Repair or replace?

[skyflyer]

A few months ago I bought my first boat as sole owner, having previously owned a one third share in another - both US built Catalinas

I have what i guess is their “standard’ arrangement of the time (1996) namely two batteries, each 180Ah and a "1-Both-2-off" rotary switch with a "Fly-Tec 20-3" mains powered charger.

The previous owner never went near shore power (well almost never) so when we connected everything and looked at voltages, I noticed that the charger is “unwell”!
It delivers 15.8V to the batteries which is way too much. I think the charging regime from the Fly-Tec is supposed to give about 14.8v initially then reducing to a lower voltage and eventually even a lower float charge. (this seems to be the 'norm' for wet lead acid batteries elsewhere, anyway)

So - is a replacement needed, or is this likely to be repairable - I feel probably not!

Perhaps more to the point, technology has moved on a lot in the intervening 20-or-so years since the Fly-Tec was state of the art, (it was probably designed in the early 90's) and this leads to several questions:

1) is a 20 Amp charger still what’s needed. More Amps = more $, so maybe a modern charger will do the same job on lower amps. Or maybe I need more Amps?
I know the 10% rule, but don't understand if this applies to the total battery capacity (as a bank) or each individual battery, if charging one at a time?

2) Should I be charging both batteries together, or one at a time. If one at a time would a VSR (Voltage Sensing Relay) be a good idea so that one battery gets charged before the other (I suspect not because surely the output voltage of the charger will trigger the relay, no matter how flat the battery, and both will end up being charged together anyway)

3) On my old (shared) boat the set up - rightly or wrongly - was that the engine alternator charged only battery 1 and the shore charger only battery 2 and if you wanted to cross charge you needed to set the rotary switch to ‘Both’. Is this normal? Is this something I would benefit from changing?

4) The biggest power draw (if engine not running) is probably refrigeration when its hot or the diesel heater in the evening if its cold. The boat is kept on a swinging mooring and so we plug in whenever we can get alongside but often go for two or three days using battery only. There’s normally some motoring to help keep the batteries topped up and we have an Adverc modifying the alternator output but its probably accurate to say that the battery of a sailing yacht will still rarely reach full charge through motoring alone. I am aware that battery life is extended by keeping the battery as fully charged as possible and not left in a state of discharge for extended periods of time, so a smart mains charger that fully charges the batteries as fast as is practical would seem to be sensible. Thoughts on that?


Other threads here speak highly of the Ctek M300 which is a 20 amp charger.

Grateful - as always - for others thoughts and input on this.

Thanks

 

[Hadenough]

Check out you batteries first. If they are OK and you charger is lowish tech find a good spark to re-build it. My, written off by Victron, 30 year old charger / inverter was rebuilt for £170 by a magician in Portsmouth. Still going strong three years later.

 

[lpdsn]

A few months ago I bought my first boat as sole owner, having previously owned a one third share in another - both US built Catalinas

I have what i guess is their “standard’ arrangement of the time (1996) namely two batteries, each 180Ah and a "1-Both-2-off" rotary switch with a "Fly-Tec 20-3" mains powered charger.

The previous owner never went near shore power (well almost never) so when we connected everything and looked at voltages, I noticed that the charger is “unwell”!
It delivers 15.8V to the batteries which is way too much. I think the charging regime from the Fly-Tec is supposed to give about 14.8v initially then reducing to a lower voltage and eventually even a lower float charge. (this seems to be the 'norm' for wet lead acid batteries elsewhere, anyway)

So - is a replacement needed, or is this likely to be repairable - I feel probably not!

Perhaps more to the point, technology has moved on a lot in the intervening 20-or-so years since the Fly-Tec was state of the art, (it was probably designed in the early 90's) and this leads to several questions:

1) is a 20 Amp charger still what’s needed. More Amps = more $, so maybe a modern charger will do the same job on lower amps. Or maybe I need more Amps?
I know the 10% rule, but don't understand if this applies to the total battery capacity (as a bank) or each individual battery, if charging one at a time?

2) Should I be charging both batteries together, or one at a time. If one at a time would a VSR (Voltage Sensing Relay) be a good idea so that one battery gets charged before the other (I suspect not because surely the output voltage of the charger will trigger the relay, no matter how flat the battery, and both will end up being charged together anyway)

3) On my old (shared) boat the set up - rightly or wrongly - was that the engine alternator charged only battery 1 and the shore charger only battery 2 and if you wanted to cross charge you needed to set the rotary switch to ‘Both’. Is this normal? Is this something I would benefit from changing?

4) The biggest power draw (if engine not running) is probably refrigeration when its hot or the diesel heater in the evening if its cold. The boat is kept on a swinging mooring and so we plug in whenever we can get alongside but often go for two or three days using battery only. There’s normally some motoring to help keep the batteries topped up and we have an Adverc modifying the alternator output but its probably accurate to say that the battery of a sailing yacht will still rarely reach full charge through motoring alone. I am aware that battery life is extended by keeping the battery as fully charged as possible and not left in a state of discharge for extended periods of time, so a smart mains charger that fully charges the batteries as fast as is practical would seem to be sensible. Thoughts on that?


Other threads here speak highly of the Ctek M300 which is a 20 amp charger.

Grateful - as always - for others thoughts and input on this.

Thanks

How are you measuring the value of 15.8V? Is it measured at the batteries? Are the battery terminals getting hot at this stage? Smart chargers do really ramp up the voltage in the constant current phase - not seen mine at 15.8V but I've seen 15.5.

20A is a measure of the maximum current your unit can deliver. Higher voltages allow it to keep putting higher current into the batteries to charge them quicker. Not sure what you mean by charging with less Amps - it'll just mean it'll take longer to charge. It sounds like you're running the batteries quite low, so you'll want to charge them quickly when alongside. (Diesel heater is probably by far the biggest drain - my battery monitor says 7 - 10A, whereas the fridge is about 3A 50% of the time).

If it were my boat, I'd make a single 360Ah domestic bank and fit a much smaller dedicated engine battery, but there's plenty of threads on that topic.

I also have to disagree about not being able to fully charge from the engine - I fitted a Sterling AtoB charger and it certainly does top them up (and it has separate outputs for engine & domestic batteries). The equivalent Adverc unit should do the same.

Worth monitoring the voltages with a multi-meter. And the temperature is crucial. Make sure the batteries aren't over-heating (and of course the water is topped up).

For the cost, if the current unit really is really buggered, you may as well get a new Sterling unit or equivalent.

 

[Gwylan]

I'd look at the batteries first - see how long they take to 'run down' to a resting voltage of about 12,3v.
The little table in the back of my boat file tells me that that should be about 50% capacity.

If that time seems unreasonably short [the time does depend on the load applied] then its probably the battery that is at fault.
I have found a 12v 50 watt halogen lamp wired across the battery is a good way of testing the capacity of the battery.

12v @ 50watts will amount to about 4Ah. So how ever many hours it takes for the battery to run down times 4 will give you a pretty good idea of what 50% of the capacity of the battery is. Good clue if it all goes dim in 4 hours, without the need for big maths!

Contrary to some opinions expressed around here, they [batteries] do not last for ever.

 

[skyflyer]

Both batteries are brand new (at end of September), replaced as a condition of my purchase as the old ones were not holding their charge. The boat was lifted out in early November and batteries have not been charged since. I visited on New Years Eve and voltages (measured by Adverc battery monitor as well as the mickymouse inbuilt voltmeter) were in the high 12 v range. So I don't think the batteries are faulty.

Even if they were I don't see how 15.8V is coming from anywhere but the charger itself. If the battery voltage is 10v, 12v or 13 v when 'static' but the voltage rises to 15.8v when the charger is energised, it has to be the charger, surely? If not, can someone explain the physics behind that?

My, written off by Victron, 30 year old charger / inverter was rebuilt for £170 by a magician in Portsmouth. Still going strong three years later.

Is your magician also still going strong? If so, can I have contact details please!

How are you measuring the value of 15.8V? Is it measured at the batteries? Are the battery terminals getting hot at this stage

Measured by battery monitor so should be very accurate. At 15.8v I don't plan to leave it running long enough to ALLOW the battery to get hot or else I'll be buying two more!

Dedicated engine battery is a longer term project - for the moment I need to get this sorted out

I also have to disagree about not being able to fully charge from the engine

That is simply a function of how long you run the engine for, nothing more. Without an advanced charger you will never get them above 70% no matter how long you run the engine because of the way a standard alternator is temperature compensated and the decrease in charging current as the battery charges up. With a smart charger you can, but you still need to run it for a certain length of time.

Basically I think I have already done the diagnosing and the charger is faulty. The real qustion is what to replace it with or whether it can be economically repaired

 

[VicS]

Basically I think I have already done the diagnosing and the charger is faulty. The real qustion is what to replace it with or whether it can be economically repaired

The Ctek you mentioned earlier would be a good choice (actually 25 amps ITYWF) I don't think I have ever seen any serious criticism of Ctek chargers.

The 10% rule you mention applies to the battery or bank you are charging, not to the total installed unless you want to charge the whole lot in one hit.

A VSR would enable both batteries to be charged from a single output charger but they would be paralleled once the priority battery is sufficiently charged for the voltage to have risen above the set value. With a VSR there might be something to gain from a larger charger

The VSR would similarly control the charging from the alternator


The alternative of course is dual output charger.

 

[William_H]

I find it hard to believe that you have 15.8 volts at the battery. Perhaps you should check at the actual battery terminal. Any difference between the battery monitor volt meter and actual terminal voltage could indicate some resistance. Bad switch or wire.
In theory 15.8 volts at the battery means either the battery is very fully charged and gassing or is faulty. Usually the battery will take a large current at this voltage which will tend to pull down the chargers voltage a bit at least. So the question is how much current is going into the battery (s) at this voltage. Does it switch to lower voltage and current at some point?
My opinion is that provided you don't leave the charger on 24/7 that it will be very suitable for short term charging at the marina. ie for a few hours while you are present. That voltage if it is correct will give you as much charge for a short term as possible. All that assuming that it is giving 15.8 volts and so a high charge current.
Yes you should charge on both position ie both batteries at once. More current so more total charge quicker.
good luck olewill

 

[charles_reed]

Basically I think I have already done the diagnosing and the charger is faulty. The real qustion is what to replace it with or whether it can be economically repaired

This is the simple question the OP is asking and the nagging by the panel, suggesting he's incompetent, is understandably galling.
My experience is that trying to repair a charger (though theoretically possible) is so difficult to find a repairer and so expensive when you've found him as to make it a waste of time, hwl, and energy.
The CTek charger does appear to be very good - when I last had to replace mine it was on the short-list only beaten to purchase by Stering selling off obsolescent stock with 3 outlets.
With rather fewer AH battery bank (330AH) I found my first 8 amp one (FF380 in 1990) inadequate but better than a trickle charger.
My 2nd 40 amp one was ideal and the current 20 amp one would struggle if I didn't have 328w of PV panel and a BZ500 MPPT controller @ 37N to augment it.
There is a good case to be made for each battery bank to have its own dedicated charger - which I'll not go into here.

 

[skyflyer]

I find it hard to believe that you have 15.8 volts at the battery. Perhaps you should check at the actual battery terminal. Any difference between the battery monitor volt meter and actual terminal voltage could indicate some resistance. Bad switch or wire.
In theory 15.8 volts at the battery means either the battery is very fully charged and gassing or is faulty. Usually the battery will take a large current at this voltage which will tend to pull down the chargers voltage a bit at least. So the question is how much current is going into the battery (s) at this voltage. Does it switch to lower voltage and current at some point?
My opinion is that provided you don't leave the charger on 24/7 that it will be very suitable for short term charging at the marina. ie for a few hours while you are present. That voltage if it is correct will give you as much charge for a short term as possible. All that assuming that it is giving 15.8 volts and so a high charge current.
Yes you should charge on both position ie both batteries at once. More current so more total charge quicker.
good luck olewill

Thanks olewill - I had wondered if I could use it short-term on that basis and you seem to be thinking on the same lines as me. What I don't quite understand about chargers is how they work; I thought a charger (of the vintage that mine is) was essentially a transformer with a voltage regulator attached to it programmed to deliver certain voltages for certain lengths of time. The manual for the charger, which I have now found says that for wet lead acid, which it was set for, this will be between 14.5v at highest reducing to 13.3v at lowest float charge. The open circuit voltage is between 14.6 and 14.8v to "compensate for voltage drop in wires" - I don't think its very sophisticated therefore!

The current, as I understand it, will vary as the battery charges up, steadily reducing.

My understanding of battery charging is to use the analogy that electricity is water, current is the volume flow, voltage is the pressure and the battery is represented by a balloon or bladder. If you increase the pressure the bladder fills quicker, but as it fills it develops its own "back-pressure" (the battery's own voltage) so eventually the pressure in the bladder balances the pressure in the hose and no more water will flow. As that point is approached the flow (current) reduces to zero. (To make the analogy even more accurate we can say the bladder has some tiny pinholes in it, allowing leakage (self discharge) so in practice a tiny flow (current) is needed continuously (float charge) to keep it topped up.

If the pressure is increased too much the bladder will burst. If the pressure is too low the bladder will fill to the same pressure but the flow will not be sufficient to fill it fully.

Perhaps thats an over-simplification, but I think its a reasonable model. Evidently it is theoretically possible to build a charger that varies the voltage as required to produce a certain current flow, but the one I have certainly isn't that sophisticated, so, reading the instructions, i don't THINK it is increasing the voltage to compensate for resistance at bad connections, but until I next visit the boat (4hrs drive away!) I cannot check whether the battery monitor takes its voltage from the battery terminals or from the back of the power distribution switch panel where the battery cables arrive.

However i take the point that its probably not worth repairing but before discarding it check all cables and connections to be sure.

Regarding a replacement, the charger at present is sited in an external locker on a bulkhead at the rear of the galley so it is powered up by a switch on the electrical panel. Does anyone know if the CTEK will power up in this way or is there a start switch or button on the unit that needs to be pressed each time. Obviously i could re-locate a new charger in the same compartment as the batteries but that would mean a lot or re-cabling and if there ever was gassing I don't think its a good idea to have an electrical device in the same locker!

 

[Vara]

My Ctek is turned on and off at the power supply, I don't touch the unit itself.

 

[rob2]

I wonder whether you have the instrucions for the charger? It's interesting that C-tek chargers use a 15.8V input for desulphating. Perhaps the charger is doing this initially until a satisfactory load characteristic is achieved to proceed with normal charging. I believe a short time on the high voltage is used to test whether the battery is ready to charge, so it would be the standard starting voltage.

Rob.

 

[ghostlymoron]

My heart says "repair", my head says " replace ".

A few months ago I bought my first boat as sole owner, having previously owned a one third share in another - both US built Catalinas

I have what i guess is their “standard’ arrangement of the time (1996) namely two batteries, each 180Ah and a "1-Both-2-off" rotary switch with a "Fly-Tec 20-3" mains powered charger.

The previous owner never went near shore power (well almost never) so when we connected everything and looked at voltages, I noticed that the charger is “unwell”!
It delivers 15.8V to the batteries which is way too much. I think the charging regime from the Fly-Tec is supposed to give about 14.8v initially then reducing to a lower voltage and eventually even a lower float charge. (this seems to be the 'norm' for wet lead acid batteries elsewhere, anyway)

So - is a replacement needed, or is this likely to be repairable - I feel probably not!

Perhaps more to the point, technology has moved on a lot in the intervening 20-or-so years since the Fly-Tec was state of the art, (it was probably designed in the early 90's) and this leads to several questions:

1) is a 20 Amp charger still what’s needed. More Amps = more $, so maybe a modern charger will do the same job on lower amps. Or maybe I need more Amps?
I know the 10% rule, but don't understand if this applies to the total battery capacity (as a bank) or each individual battery, if charging one at a time?

2) Should I be charging both batteries together, or one at a time. If one at a time would a VSR (Voltage Sensing Relay) be a good idea so that one battery gets charged before the other (I suspect not because surely the output voltage of the charger will trigger the relay, no matter how flat the battery, and both will end up being charged together anyway)

3) On my old (shared) boat the set up - rightly or wrongly - was that the engine alternator charged only battery 1 and the shore charger only battery 2 and if you wanted to cross charge you needed to set the rotary switch to ‘Both’. Is this normal? Is this something I would benefit from changing?

4) The biggest power draw (if engine not running) is probably refrigeration when its hot or the diesel heater in the evening if its cold. The boat is kept on a swinging mooring and so we plug in whenever we can get alongside but often go for two or three days using battery only. There’s normally some motoring to help keep the batteries topped up and we have an Adverc modifying the alternator output but its probably accurate to say that the battery of a sailing yacht will still rarely reach full charge through motoring alone. I am aware that battery life is extended by keeping the battery as fully charged as possible and not left in a state of discharge for extended periods of time, so a smart mains charger that fully charges the batteries as fast as is practical would seem to be sensible. Thoughts on that?


Other threads here speak highly of the Ctek M300 which is a 20 amp charger.

Grateful - as always - for others thoughts and input on this.

Thanks

 

[nimbusgb]

Stupid question but is the onboard charger rated for 220/240v in?

If it was a US boat .........

 

[Vara]

I wonder whether you have the instrucions for the charger? It's interesting that C-tek chargers use a 15.8V input for desulphating. Perhaps the charger is doing this initially until a satisfactory load characteristic is achieved to proceed with normal charging. I believe a short time on the high voltage is used to test whether the battery is ready to charge, so it would be the standard starting voltage.

Rob.

http://www.ctek-chargers.com.au/uploads/3/6/2/9/3629451/4107_m300_en.pdf

 

[ianj99]

If the charger has temperature compensation, it is possible the charging voltage could reach 15.8v if its below zero on board.

 

[skyflyer]

The link to instructions posted above is for the C-tek. The link to the instructions for the broken charger is here http://promariner.com/wp-content/uploads/2013/06/Flyback-PromaticManual.pdf which you will see is dated 1997, but the boat was built in1996 and I am willing to bet the charger was designed back in the early 90s.

It is set for 240v (boat was imported to UK new). The instructions state quite clearly that it is a 3 stage process, and nowhere does it feature anything as sophisticated as temperature compensation, 15.8v or a desulphation stage as such!

I am not prepared to risk leaving it charging on 15.8V for more than an hour or so (to find out if the voltage drops), because I believe that will probably boil the battery.

Grateful as I am for people trying to help by "re-diagnosing" the issue I think its pretty clear that the charger is the problem and it needs replacement if it cannot be economically repaired so my original questions about a suitable replacement and charging regimes, amperage etc, still stand!

Thanks anyway though - lots of useful intel coming through one way or the other!

 

[Paul8f]

I wonder whether you have the instrucions for the charger? It's interesting that C-tek chargers use a 15.8V input for desulphating. Perhaps the charger is doing this initially until a satisfactory load characteristic is achieved to proceed with normal charging. I believe a short time on the high voltage is used to test whether the battery is ready to charge, so it would be the standard starting voltage.

Rob.

Sorry to revisit an old thread here, but Rob2 could be correct about the desulphating. Some CTEK chargers have a Recondition function that applies 15.8v to a 12v battery after the Absorption and Analyze charging stages have completed. Recond. is an optional step that should only be done once per year on any one battery. It's up to the user to manually turn this feature off - if it's left on, the next battery that you charge will also get the reconditioning (or rejuvenator step). A silly design if you ask me, as you could be unintentionally over-gassing all your batteries without realizing it.

I had a CTEK MXS 7.0 charger with such a feature. The charger had a 5 year warranty and died after about a year and a half. Always felt that it worked a bit hot, but hey I got my re-fund in the end.

 

[RichardS]

Sorry to revisit an old thread here, but Rob2 could be correct about the desulphating. Some CTEK chargers have a Recondition function that applies 15.8v to a 12v battery after the Absorption and Analyze charging stages have completed. Recond. is an optional step that should only be done once per year on any one battery. It's up to the user to manually turn this feature off - if it's left on, the next battery that you charge will also get the reconditioning (or rejuvenator step). A silly design if you ask me, as you could be unintentionally over-gassing all your batteries without realizing it.

I had a CTEK MXS 7.0 charger with such a feature. The charger had a 5 year warranty and died after about a year and a half. Always felt that it worked a bit hot, but hey I got my re-fund in the end.

That's simply not correct I'm afraid. The Ctek recondition function has to be deliberately selected by several presses of the start button. One press of the start button starts the charger in normal charge mode and the "nomal" light comes on. The "recond" light does not light up unless you keep pressing to select recondition.

I can't imagine how anyone could accidentally select recondition mode or inadvertently leave it in this mode unless they intended to do so.

Richard

 

[skyflyer]

Also you seem to have missed in my posts the the fact that I didnt have a C-tek charger and the charger I did have wasnt that sophisticated!

In the end i replaced it with a new Pro_nautic which is a badged Stirling (or the other way round, who knows) as they gave a decent discount as it was a 'trade-in' of a previous model of theirs.

Interestingly a few months ago the temp sensor of my Adverc 'smart charger' alternator controller failed and I got charging voltages of 15.4v from the engine. Adverc very helpful on the phone and immediately pointed me to the failed item (about £4 to replace) which when 'failed' makes the charger think its arctic conditions and ramps up the volts!

 

[Paul8f]

One press of the start button starts the charger in normal charge mode and the "nomal" light comes on. The "recond" light does not light up unless you keep pressing to select recondition.

I guess it depends on the charger model. My model would remember if it was last used in Recond mode, and automatically select it when plugged in again. The charger ramping up the o/p voltage to compensate for cold temperature (or thinking that it was cold) as Skyflyer said makes most sense as an explanation for the 15.8v.

Paul.