Two things I didn't know about my batteries and one thing I still don't know

[PEJ]

Ok so I knew I had a small problem with the port side starting battery bank but I could link it to the starboard to get it going. After a run port starts up OK.

Pulling up to the fuel berth I didn't do a brilliant job, the back end was too far out so I gave it a bit of stern thruster and port reverse. The stern thruster stopped working and the port engine died. Oh great just what I need as I am trying to tie up!

Any road up, it transpires that the port side starters must be the ones that drive the stern thuster and what little charge I had was exhausted when I turned them on and with less than 10V going to it the EDC shut the port engine down. Wish I had known would happen this before I hit the stern thruster!

Now I suspect that one of the batteries is duff - any tips on how to find which one it is? Does the dodgy one get hot?

 

[sarabande]

you have a multimeter handy ?

A failed or failing battery can just die without getting hot. The only real way in the absence of a clever discharge meter or spec gravity tester is to charge them up, leave them for 24 hours, and see what the readings are at the end of the period.

If you could safely arrange a small load such as a cabin light to come off the bank, that would show a dodgy battery by dropping its voltage even more clearly.

 

[BartW]

disconnecty the battery's after charging,
any battery showing a voltage lower then 12,3 volt is bad,

a more accurate test you can do with a battery tester, like this:
http://www.tecmate-int.com/ENG/d_battery_testers.php

(you have to disconnect at least one side of each battery for testing)
this tester will show you a figure "State Of Health" 0...100%

I replaced my domestic battery's in spring last year,
but half way this season I noticed that capacity was lower then before,

with the tester I could diagnose that one battery was bad, and all other were SOH 100%

 

[dj43]

Had similar problem this year, ended up replacing all of them, thought was if one had gone other,s were sure to follow and would be in the most inconvenient time they were less than three years old, new one,s have a three year warranty so if they don,t last untill then hopefully will be replaced

 

[Jurgen]

Just had the same problem, went over to the Folly on Saturday, came back after lunch and dead as a door nail.

Thank goodness for Seastart lol.

Just need to see which is the dud so thanks for the advice

 

[Deleted User YDKXO]

I'd be a little concerned about the alternator charging that particular battery bank. It seems odd to me that a battery, even a failing one, that was receiving charge from an engine alternator would drop so low in voltage that the engine electronic control would shut the engine down and yes I realise that the stern thruster was in use at the time. Just worth checking the output from the alternator as well

 

[tinkicker0]

The only sure way is to use a heavy discharge meter to test each one. It is entirely possible for a battery to show a healthy voltage, but sag horribly when put under load. In other words you may have volts, but not amps.

 

[gjgm]

Not sure if was scientific or not, but I put meter across and turned the engine. The Ok dropped a bit V;the knackered one collapsed.
Well, at least that is the one I replaced and I haven't had a problem since changing that one.

 

[PEJ]

So, I've got a lot of stuff in the lazerette and most of it on the port side battery box - or so I thought. The box I could see said starboard on the label so I cleared the stuff off the the other box ( including the bow cushions and a carpet with the outboard preventing them from coming out ) only to find the label on that one said starboard as well!

So not only do I not know which one is dud I don't even know which box to look in!

 

[rafiki_]

B

So, I've got a lot of stuff in the lazerette and most of it on the port side battery box - or so I thought. The box I could see said starboard on the label so I cleared the stuff off the the other box ( including the bow cushions and a carpet with the outboard preventing them from coming out ) only to find the label on that one said starboard as well!

So not only do I not know which one is dud I don't even know which box to look in!

Your new Maplins multimeter will sort this out for you. Just check the voltages, the dud will be significantly lower than the others.

 

[PEJ]

Thanks for the advice chaps.

I didn't have my multimeter with me today nor a helper to turn the keys. I'll try again tomorrow with both. At least I can get at them now.