Bit of a pickle - bad battery

[sailorbenji]

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 “?

 

[Refueler]

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.

 

[sailorbenji]

It’s a common rail diesel with ECU etc I was of the belief it needs power to it constantly.

 

[sailorbenji]

So

It’s a common rail diesel with ECU etc I was of the belief it needs power to it constantly.

Blonde Moment sorry. So you mean disconnect the alternator feeds before we start engine. Just the positive to the battery I presume ?

Do we not run the risk of damaging the alternator with no load? Also any idea what the amp draw would be just running it off a battery? So I can get an idea how long it could run.

 

[Refueler]

Don't know about the ECU ... but I would suspect that battery keep ECU powered .....

But as regards alternator - damage is done when its connected and charging while engine running and you switch off alternator charge .. the sudden stop can blow the diodes in the bridge rectifier / regulator. Many modern alternators are supposed to have protection for this - but I know from my own experience - it does not always work !

But as long as alternator is switched OFF / disconnected before starting engine - then alternator will be fine.

Obviously you need to find out why your battery is gassing and high amps / low volts from alternator ... taking off and handing to Auto Electrics guy to check would be good idea ...

How long you can run the battery ???? No idea of what loads you have.

 

[sailorbenji]

Don't know about the ECU ... but I would suspect that battery keep ECU powered .....

But as regards alternator - damage is done when its connected and charging while engine running and you switch off alternator charge .. the sudden stop can blow the diodes in the bridge rectifier / regulator. Many modern alternators are supposed to have protection for this - but I know from my own experience - it does not always work !

But as long as alternator is switched OFF / disconnected before starting engine - then alternator will be fine.

Obviously you need to find out why your battery is gassing and high amps / low volts from alternator ... taking off and handing to Auto Electrics guy to check would be good idea ...

How long you can run the battery ???? No idea of what loads you have.

just the engine’s own electronics. This is a standalone engine start battery not linked to house batteries.

 

[noelex]

Take a battery from your house bank and use this as the engine battery.

 

[sailorbenji]

Thanks I thought of that but our house bank is 24V and 2 12V batteries in series so we’d lose everything if we did that

 

[bedouin]

Can you just take the +ve from the engine battery and connect that to the mid point of your 24v house? I assume your domestic bank has its own charging arrangement so you should be able to maintain that for some time. Not ideal as it would lead your domestic batteries to be unbalanced but you can sort that our later once you are safely home

 

[sailorbenji]

Can’t get to the mid point but what if I ran a positive and a negative to one battery of my 24V bank? If I multimeter across one battery I get 13.6V or so. Would that work?

Can you just take the +ve from the engine battery and connect that to the mid point of your 24v house? I assume your domestic bank has its own charging arrangement so you should be able to maintain that for some time. Not ideal as it would lead your domestic batteries to be unbalanced but you can sort that our later once you are safely home

 

[bedouin]

Yes - that is what I was meaning - use one battery of the domestic - probably safer to use the one that has the domestic -ve in case the two negatives join somewhere so take the engine +ve from the point where the -ve of the "upper" battery is connected to the +ve of the lower, and the -ve from the -ve of the lower. You would probably want to leave the alternator totally disconnected

 

[duncanmack]

So

Blonde Moment sorry. So you mean disconnect the alternator feeds before we start engine. Just the positive to the battery I presume ?

Do we not run the risk of damaging the alternator with no load? Also any idea what the amp draw would be just running it off a battery? So I can get an idea how long it could run.

IIRC current draw on a 12v common rail system is @:20AH.

 

[Ardenfour]

IIRC current draw on a 12v common rail system is @:20AH.

20Ah isn't a measure of current. In any case, the current drawn would vary between different engines. And what is a '12v common rail system'?

 

[duncanmack]

20Ah isn't a measure of current. In any case, the current drawn would vary between different engines. And what is a '12v common rail system'?

Correct. 20 amps draw. My bad.
Diesel common rail injection system. Pumps + ECU + injectors 20A
My experience is with vehicles.
Add HID headlamps and you're looking at a total current draw of 80A.
No alternator and your battery goes flat in 15 minutes.
Ok?

 

[bedouin]

I doubt if the Yanmar has electric fuel pumps

 

[noelex]

Can you just take the +ve from the engine battery and connect that to the mid point of your 24v house? I assume your domestic bank has its own charging arrangement so you should be able to maintain that for some time. Not ideal as it would lead your domestic batteries to be unbalanced but you can sort that our later once you are safely home

This is what I would do, but there are some issues. Starting the engine from this house bank will need some heavy duty cables. It is possible, but requires some electrical knowledge to sort out safely.

My suggestion would be to use one of the house batteries to run the engine. Given your 24v house bank, this will completely disable the house system, but hopefully you have back up navigation systems (phone, tablet or paper charts). Car starter batteries are available almost everywhere and hopefully this jury rig will enable you to navigate to a location where a battery like this is available. Any 12v car starter battery will be OK in a pinch.

 

[William_H]

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

 

[B27]

Buy another battery?
Possibly acquire a used battery if you are beyond the reach of car parts retailers?

I don't like these 'clever' systems with no effective backup for the engine battery.

 

[colind3782]

Buy another battery?
Possibly acquire a used battery if you are beyond the reach of car parts retailers?

I don't like these 'clever' systems with no effective backup for the engine battery.

The OP is at sea.

 

[B27]

The OP is at sea.

Literally or metaphor?