Bit of a pickle - bad battery

[Refueler]

I would suggest disconnect the alternator as discussed. Then hook up the 24 to 12v converter to charge the engine 12v battery.
However it all seems confusing to me. If you have a 24v system this is usually for the engine especially start plus anchor winch and thrusters. The 12v domestic system is run from a converter from 24v. Unless you have 2 alternators 12 and a 24. Perhaps OP is also confused. However by now he is hopefully with drama over. ol'will

To be honest - I am now not liking what I read .... a boat with mixed system ? 12V starter ... 24V domestics ?

Engine 12v battery 'fizzing' ......

How are the batterys charged at the voltages required ? 14.x V for the starter .... 28.x V for the domestics ?? I know various boats have mixed systems - but always strikes me as a recipe for errors ...

 

[VicS]

To be honest - I am now not liking what I read .... a boat with mixed system ? 12V starter ... 24V domestics ?

Engine 12v battery 'fizzing' ......

How are the batterys charged at the voltages required ? 14.x V for the starter .... 28.x V for the domestics ?? I know various boats have mixed systems - but always strikes me as a recipe for errors ...

I think you will find that a 24 volt secondary alternator is available as optional equipment for the engine in question, a Yanmar 4JH80.
Presumably this is what sailorbenji has for charging his domestic battery .

.From the Engine data sheet:

 

[PaulRainbow]

I would suggest disconnect the alternator as discussed. Then hook up the 24 to 12v converter to charge the engine 12v battery.
However it all seems confusing to me. If you have a 24v system this is usually for the engine especially start plus anchor winch and thrusters. The 12v domestic system is run from a converter from 24v. Unless you have 2 alternators 12 and a 24. Perhaps OP is also confused. However by now he is hopefully with drama over. ol'will

Using the BtoB charger is no different to using the alternator, the battery is bad so it will still get hot, presumably gassing.

 

[PaulRainbow]

Hi all.

In a bit of a pickle (at sea in very low winds as I write this).

I felt a floorboard very hot by complete chance. It’s the engine battery under there and it was at about 55 degrees case temp before I stopped the engine.

I suspect the battery has gone bad. The alternator was pushing 30 amps into it but the voltage won’t seem to go much above 13.3V.

The battery will still start the engine and it’s slowly cooling down now but I’m not sure I can run the engine for any length of time as the battery was fizzing.

We’ve got a Yanmar 4JH80 CR diesel engine, almost brand new. The belt also runs the coolant pump so I can’t just take off the belt.

Things at my disposal are

1. A lithium jump pack
2. A 24-12V 12A converter if I needed to keep the engines electrics alive somehow (presuming that would be enough)

Any good thoughts on how I might be able to get myself in a position where the engine is up and running, but the battery isn’t getting stuffed with amps it can’t take “?

If the battery still starts the engine there is a good chance that it's the alternate that's at fault.

Do you have 2 alternators ? If so, disconnect the 12v one. If you have heavy enough cable to connect the engine cable to one of the domestic batteries (as post #11 suggests) do that and disconnect the engine battery negative from the battery. If you don't have heavy enough cables, connect the biggest you have between the engine battery and one domestic battery, start the engine, then disconnect the engine battery negative.

 

[Refueler]

I think you will find that a 24 volt secondary alternator is available as optional equipment for the engine in question, a Yanmar 4JH80.
Presumably this is what sailorbenji has for charging his domestic battery .

.From the Engine data sheet:

View attachment 182623

Hi VicS ... Am aware of options ... just my head is having thoughts running around about this 24v and the start battery 'fizzing' ... then why the low 13.1v ??

Something has triggered battery failure ... gassing and 13V .....

Trying to picture this in mind .. probably just me - but for me - something doesn't add up.

 

[PaulRainbow]

Hi VicS ... Am aware of options ... just my head is having thoughts running around about this 24v and the start battery 'fizzing' ... then why the low 13.1v ??

Something has triggered battery failure ... gassing and 13V .....

Trying to picture this in mind .. probably just me - but for me - something doesn't add up.

We need to know how the batteries are being charged. One alternator or two ? One alternator and a B2B ? Or what ?

 

[Refueler]

We need to know how the batteries are being charged. One alternator or two ? One alternator and a B2B ? Or what ?

Agreed. And daft as it may seem ... I hope the 12v battery was not subjected to 24v charge !!! that would certainly warm it up and gassing ... possibly far worse !!!

 

[Rhylsailer99]

Being a diesel - it does not need alternator running with it ...

If you can disconnect the alternator so it does not charge BEFORE starting the engine ... then you should be ok ... of course this then means that all your electrics will be running just off battery with no charge maintaining them.

Would removing the wire that's needed to get the alternator working work. Its the one that goes to the ignition light not sure of its name.

 

[Sandy]

I doubt if the Yanmar has electric fuel pumps

My ancient 1 pot Yanmar had an electric fuel pump.

 

[PaulRainbow]

Would removing the wire that's needed to get the alternator working work. Its the one that goes to the ignition light not sure of its name.

Excitation wire. Disconnecting that wouldn't be a reliable option.

 

[Refueler]

Would removing the wire that's needed to get the alternator working work. Its the one that goes to the ignition light not sure of its name.

In my book - its the exciter lead .... basically excites the alternator to start producing ... it provides for Ign light because 12v flows one way when switch on ... then once alternator is working - initial 12v is opposed and wire effectively goes to zero, or as later systems - being LED it only lights one way .. no light.

 

[colind3782]

Literally or metaphor?

#1

 

[rogerthebodger]

The OP has a single 12V start/engine battery and 2 12V batteries in series for domestic.

The Op could simply connect the 12V + of the engine/starter and the engine negative feed to one to the 2 12V batteries to supply only 12 V to the engine ECU but still keep the 24V domestic supply.

Disconnect the alternator feed from the charge light will prevent the alternator from damaging the old engine start battery of the new section of the domestic any further as without the charge light connected then is no excitation current to start the alternator charging

 

[B27]

...

Disconnect the alternator feed from the charge light will prevent the alternator from damaging the old engine start battery of the new section of the domestic any further as without the charge light connected then is no excitation current to start the alternator charging

Not always true!
The warning light current does kickstart a dynamo or alternator, but if there's enough remaining magnetism in the rotor, the alternator may start up, particularly if given some revs.

 

[Refueler]

Not always true!
The warning light current does kickstart a dynamo or alternator, but if there's enough remaining magnetism in the rotor, the alternator may start up, particularly if given some revs.

Correct .... in fact - if the alternator spins fast enough - it can create enough magnetic to start the charge process. The Excitation is an addition to speed up the process.
To g'tee no charge to battery - disconnect the output from alternator BEFORE starting engine.

 

[rogerthebodger]

Not always true!
The warning light current does kickstart a dynamo or alternator, but if there's enough remaining magnetism in the rotor, the alternator may start up, particularly if given some revs.

Yes, my Honda suitcase generator is supposed to be self-exciting, but does not as it have lost any residual magnet

 

[sailorbenji]

Hi All,

Well all is well that ends well, and thank you all for the input.

The scenario is we were on passage from Anglesey to Rosneath...left the mooring under sail and had a cracking passage to Port Erin in the IoM for a bit of shelter, then good sail all the way to around 15NM south of Ailsa Craig, where we ran out of wind. By this point we had probably only used the engine for 30 minutes in total. We fired up the engine and after motoring for a couple of hours, got a "12V battery overheat" warning on our battery monitoring system and I could feel the floorboard warm with my hand....good job we have temp sensors, as otherwise this could have gone unnoticed.

I thought useful maybe to explain our system in full. Believe it or not, I do know what I'm talking about (at least somewhat), so no, we were not outputting a 24V alternator into a 12V battery or anything like that.

Our boat set up is as follows :

1. A 48V "storage bank" consisting of 4 x 24V Lithium batteries in a 2S2P configuration. This bank is charged by a 48V "smart alternator" from the engine or via a charger/inverter from shore-power.

2. A 24V "house bank" consisting of 2 x 12V 200Ah AGM batteries in a 2S configuration. This bank is constantly floated by 2 x 48->24 converters in parallel. Most of our loads run off this 24V bank (internal lighting, nav lighting, chart plotters, VHF, HF radio, winches, windlasses, furlex etc....with a few loads (NMEA2K network mainly) running off a couple of 24V-12V converters.

3. A dedicated 12V "engine start" battery consisting of 1 x 12V 63Ah AGM battery. This bank is constantly floated by a 24V-12V battery maintainer from the house bank, as well as charged by the standard Yanmar 12V alternator when engine is running.

I'll be honest and say my knowledge of how alternators work, what damage can be done running without load etc is not high.

From the monitor, I could see the engine start battery at around 14V, but with the alternator still outputting 18-22A into it, and with the battery temp (bear in mind this is measured at the terminal) north of 45 degrees, it was clear something was very amiss.

Firstly, I considered just removing the alternator belt, disabling the alternator. However, on this engine the same belt powers the cooling pump, so not an option.

I then considered using one of our 24V-12V converters to feed the engine power (it is a Yanmar 4JH80 so common rail), with battery cables removed from the alternator, and using a jump pack to get the engine started....however this would have meant running the alternator without load and I believed that might damage it....I wasn't sure if just removing the exciter wire etc was sufficient to stop any damage.

I then considered running engine in short bursts, limiting the temperature peaks, waiting for it to cool, trying again...but we had over 60NM to run and this would have taken an awfully long time as the cooling time was measured in hours and we were facing tide against.

I finally (after drifting on the current for a few hours totally becalmed close to Ailsa Craig), decided to try and tap into the "mid point" of our 24V bank. Luckily I had a couple of decent lengths of heavy duty battery cable (we relocated the inverter/charger last year and these were left over from that). After finding them, I was relieved to see they still had lugs crimped on them, as otherwise it was going to have to be some sketchy connections going on.

I had about an inch of extra length, and managed to disconnect everything from the 12V engine battery, and connect everything to one-half of our 24V bank. This did mean the alternator would be charging half of our 24V bank, but like I say, I wasn't sure of the risk of running the alternator with no output connected. Anyway, this method I'm pleased to say, worked very well..we motored for well over 6 hours, I of course kept a very keen eye on the current and voltage the alternator was putting out, but it was absolutely perfect. We of course had a slightly unbalanced 24V bank, but nothing crazy and now equalised.

This points to a very sick 12V engine start battery as being the cause of all our woes....I'm supposing, that at some point on the hard, and quite possibly after the yard winterised the engine, they left the engine breaker on....the 24-12V battery maintainer would have kept it topped up until the 24V bank reached a cut-off point (24.4V or so from memory)...then the 12V battery would have been drained, potentially very low....at some point someone has restored shore-power and the maintainer kicked back in, very slowly recharging the battery at a very low rate of 1-2A, which the battery seems to have been able to cope with. However, as soon as the alternator was charging, there's clearly been some kind of internal break-down or short.

What's surprising is the battery had absolutely no issues in cranking the engine at all, despite it's sickness.

The good news is it's a simple fix of a replacement battery, the other good news is I've learnt that there's a jury-rig method now tried and tested that can get us home.

I don't think there's anything fundamentally wrong with our set-up.

 

[Bouba]

Hi All,

Well all is well that ends well, and thank you all for the input.

The scenario is we were on passage from Anglesey to Rosneath...left the mooring under sail and had a cracking passage to Port Erin in the IoM for a bit of shelter, then good sail all the way to around 15NM south of Ailsa Craig, where we ran out of wind. By this point we had probably only used the engine for 30 minutes in total. We fired up the engine and after motoring for a couple of hours, got a "12V battery overheat" warning on our battery monitoring system and I could feel the floorboard warm with my hand....good job we have temp sensors, as otherwise this could have gone unnoticed.

I thought useful maybe to explain our system in full. Believe it or not, I do know what I'm talking about (at least somewhat), so no, we were not outputting a 24V alternator into a 12V battery or anything like that.

Our boat set up is as follows :

1. A 48V "storage bank" consisting of 4 x 24V Lithium batteries in a 2S2P configuration. This bank is charged by a 48V "smart alternator" from the engine or via a charger/inverter from shore-power.

2. A 24V "house bank" consisting of 2 x 12V 200Ah AGM batteries in a 2S configuration. This bank is constantly floated by 2 x 48->24 converters in parallel. Most of our loads run off this 24V bank (internal lighting, nav lighting, chart plotters, VHF, HF radio, winches, windlasses, furlex etc....with a few loads (NMEA2K network mainly) running off a couple of 24V-12V converters.

3. A dedicated 12V "engine start" battery consisting of 1 x 12V 63Ah AGM battery. This bank is constantly floated by a 24V-12V battery maintainer from the house bank, as well as charged by the standard Yanmar 12V alternator when engine is running.

I'll be honest and say my knowledge of how alternators work, what damage can be done running without load etc is not high.

From the monitor, I could see the engine start battery at around 14V, but with the alternator still outputting 18-22A into it, and with the battery temp (bear in mind this is measured at the terminal) north of 45 degrees, it was clear something was very amiss.

Firstly, I considered just removing the alternator belt, disabling the alternator. However, on this engine the same belt powers the cooling pump, so not an option.

I then considered using one of our 24V-12V converters to feed the engine power (it is a Yanmar 4JH80 so common rail), with battery cables removed from the alternator, and using a jump pack to get the engine started....however this would have meant running the alternator without load and I believed that might damage it....I wasn't sure if just removing the exciter wire etc was sufficient to stop any damage.

I then considered running engine in short bursts, limiting the temperature peaks, waiting for it to cool, trying again...but we had over 60NM to run and this would have taken an awfully long time as the cooling time was measured in hours and we were facing tide against.

I finally (after drifting on the current for a few hours totally becalmed close to Ailsa Craig), decided to try and tap into the "mid point" of our 24V bank. Luckily I had a couple of decent lengths of heavy duty battery cable (we relocated the inverter/charger last year and these were left over from that). After finding them, I was relieved to see they still had lugs crimped on them, as otherwise it was going to have to be some sketchy connections going on.

I had about an inch of extra length, and managed to disconnect everything from the 12V engine battery, and connect everything to one-half of our 24V bank. This did mean the alternator would be charging half of our 24V bank, but like I say, I wasn't sure of the risk of running the alternator with no output connected. Anyway, this method I'm pleased to say, worked very well..we motored for well over 6 hours, I of course kept a very keen eye on the current and voltage the alternator was putting out, but it was absolutely perfect. We of course had a slightly unbalanced 24V bank, but nothing crazy and now equalised.

This points to a very sick 12V engine start battery as being the cause of all our woes....I'm supposing, that at some point on the hard, and quite possibly after the yard winterised the engine, they left the engine breaker on....the 24-12V battery maintainer would have kept it topped up until the 24V bank reached a cut-off point (24.4V or so from memory)...then the 12V battery would have been drained, potentially very low....at some point someone has restored shore-power and the maintainer kicked back in, very slowly recharging the battery at a very low rate of 1-2A, which the battery seems to have been able to cope with. However, as soon as the alternator was charging, there's clearly been some kind of internal break-down or short.

What's surprising is the battery had absolutely no issues in cranking the engine at all, despite it's sickness.

The good news is it's a simple fix of a replacement battery, the other good news is I've learnt that there's a jury-rig method now tried and tested that can get us home.

I don't think there's anything fundamentally wrong with our set-up.

It’s surprising what a damaged battery can still do...my engine start batteries had no trouble cranking over the engine despite squirting a jet of acid out of the top. Nightmare job changing them because boatbuilders think you would rather have them out of sight .
I’m glad that you got going in the end...I had a vision of you all becalmed while the panel argued over semantics, theory and grammar. Well done

 

[sailorbenji]

It’s surprising what a damaged battery can still do...my engine start batteries had no trouble cranking over the engine despite squirting a jet of acid out of the top. Nightmare job changing them because boatbuilders think you would rather have them out of sight .
I’m glad that you got going in the end...I had a vision of you all becalmed while the panel argued over semantics, theory and grammar. Well done

Haha, indeed! It's amazing how there's no consensus on how (safely) to disconnect an alternator, or stop one generating...I suppose it's because there maybe is no single answer, and is model dependent?

Any way, like I said, all well in the end, I'm just very grateful for 2 things...firstly that we had very good battery monitoring, including temp warnings (otherwise it may, likely would, have gone unnoticed until potentially very bad things happened), and that 2, I by chance had 2 heavy duty (and reasonably long) battery cables to hand on board!

 

[Bouba]

Haha, indeed! It's amazing how there's no consensus on how (safely) to disconnect an alternator, or stop one generating...I suppose it's because there maybe is no single answer, and is model dependent?

Any way, like I said, all well in the end, I'm just very grateful for 2 things...firstly that we had very good battery monitoring, including temp warnings (otherwise it may, likely would, have gone unnoticed until potentially very bad things happened), and that 2, I by chance had 2 heavy duty (and reasonably long) battery cables to hand on board!

I didn’t want to contribute because some were definitely experts and I felt out of my depth.....and when I was about to be brave, you said you wanted to preserve your 24 v set up...so I hadn’t anything left to contribute. But my idea would have been that getting home was priority number one and everything else is sacrificed to allow that...so I would have replaced your starter battery with both your house batteries...but put them in parallel to give them enough cranking amps (assuming they were deep cycle).
However I’m no expert so I deferred to the others