New batteries to flat in 2 hours...?

Hazymoonshine

Hazymoonshine

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I brought my 'new to me' Moody 346 home today, having first put 2 brand new fully charged 110Ah batteries in to replace those on board. Motored off from Brighton and 2hrs later was rather alarmed to see the rev counter falling slowly. Finally twigged as other services failed that the batteries were not being charged...but what a fast rate of discharge. Thankfully we kept motoring and brought her into Portsmouth. But what is going on?

Interestingly we had initially set off on batt 1&2, but I selected batt 1 to try and save what little was left in 2. I was very surprised to see 2 had been recharged to 12v indicated an hour later.

Boat is fitted with a Sterling mains battery charger/conditioner. We had noticed previously that on shore power the lights were very dim and had assumed a problem with the old batteries - hence replacement.

I am wondering whether something is shorting, the batteries are wired incorrectly or the Sterling system is somehow draining the batteries?

Hopefully these symptoms fit a picture for someone - so far I am rather bemused by it all.

Best wishes
 
This is complex and possibly has a couple of causes.

Unless someone else comes in with the answer, I'll talk to you tomorrow. The rev. counter should not be affected by battery voltage unless there is a major fault in the system. 12 volts is nowhere near fully charged. 14.4 would be nearer the mark and if you've one of Charlie's gadgets 16.1 should be expected as a charging voltage - but NOT a battery voltage - sorry, that might confuse.

Until tomorrow

Steve Cronin
 
[ QUOTE ]
The rev. counter should not be affected by battery voltage unless there is a major fault in the system

[/ QUOTE ] If two fully charged batteries are virtually discharged in 2 hours there is a major fault surely?

Surprising though that there was no evidence of overheating wiring (or worse!)

Looking forward to your explanations tomorrow.
 
14.4 would be what I would expect from a charging voltage. A fully charged battery I would expect to read around 13.6. If your batteries are charging at 16 volts I would stand well back.
 
Got to get back to basics for this but basically suggest either the batteries are no good or more likely you aren't charging. You've got to reduce the number of unknowns. Suggest you get the batteries checked first, take them to someone with a proper tester, they may need to be charged with a conventional charger first.
You need to see a charging voltage of at least 13.8 volts and no more than 14.5v with the engine running, measure right of the battery terminals. If you can borrow an clamp on DC ammeter do so look for a charging current on each battery this will vary considerably depending on the state of charge of the batteries. You need to check for usage, you can do this with a convention ammeter set to at least 10A. Don't run the engine for this, take a battery terminal off and clip + to battery+ and - to the cable and look for current draw, don't try running anything heavy on current like windlass or starter or thruster.
 
[ QUOTE ]
basically suggest either the batteries are no good or more likely you aren't charging. You've got to reduce the number of unknowns. Suggest you get the batteries checked first, take them to someone with a proper tester, they may need to be charged with a conventional charger first

[/ QUOTE ] He did say "Two brand new fully charged batteries"!
 
If two fully charged 110 AH batteries are flat after 2 hours then you have a massive current drain somewhere
Something would need to be pulling about 100 amps, thats a huge load and its difficult to believe that is occuring, any sort of short that is causing that sort of current draw would cause a lot of heat and you would surely notice the smoke and smell?
Just a thought, but I wonder if the batteries are actually flat - seems more likely to me there is a bad connection somewhere - maybe in the battery switch or earth. You mentioned that when on shore power with the Sterling charger the lights were dim - the lights should be bright even if no batteries are connected so that would also indicate a connection problem.
 
I recently had to get my Advec fixed because it was charging at 16v ~ you could smell the batteries from 10' away. It now charges at 14.4v and when the batteries are at rest they read 13.5v.

BTW the problem turned out to be my changing from a Yanmar 2GM to the new 3YM ~ different type of alternator that needed an extra relay adding into the line to stop it discharging the batteries when the engine was switched off, appearently without the relay it burnt out a bit in the Advec "brain".

Peter.
 
The new batteries both had their green 'lights' showing when bought and yes, I was worried about heat if they were discharging so fast. Having once had a battery boil in a helicopter I have always been wary of batteries! Despite regular checking no significant heat generation was apparent - but the engine space was pretty hot anyway after 2 hours of running.

It has been suggested that it might be a short within the alternator, which would accord with the rev counter slowly falling to zero over a couple of hours and a high discharge rate. Not sure that explains the inability of shore power to make the lights work properly though....I assumed that was something to do with the charger and beyond my knowledge.

Thanks

H
 
Firt thing I'd do is check for dirty/high resistance connections.
As a bad connection passes current, it heats up, the resistance increases, giving the impression that the voltage is dropping, also prevents the batteries charging properly.
Clean and tighten all connections.
 
Further to my brief comment of last night...

Just to get things clear, could you tell me the following:-

Is the starter motor connected to only one of the batteries or is it connected to the whole system after the 1, 1+2, 2, switch? Not necessarily relevant to your current problem but it will indicate as to whether your batteries are charged by the Sterling in parallel with each other or seperately as that and many other makes of charger are able to accomplish. Incidentally, a boat like yours would be better served if it had an entirely seperate battery for the engine start from that (or those - your total capacity of 220 Ah is barely adequate for a 35footer's domestics alone) used for the domestic supply. !X85Ah starter and a total capacity of 360Ah for domestics would be a better proposition. Split charged via a low loss diode (I'm not a fan of VSRs - an old contentive bone here!) and fed by an intelligently regulated alternator (You have already mentioned the only name I would contemplate in this respect)

Did you buy these new batteries, install them and move off without a period of connection to the mains charger? If so, then you have to take into account that batteries stored on the shelves of suppliers are usually only partly charged and require a couple of periods of charge & discharge to bring them up to full capacity.

You say that when the Sterling mains charger was powering the domestics the interior lights were dim. Was there a period when you tried the lights with the charger connected and switched on but the batteries disconnected? If it was and they were bright then it isn't the charger - incidentally DON'T do this too often - the open voltage at initial start-up of a smart charger is in excess of 16volts as part of an initial "battery plate cleaning" feature.

The apparent re-energisation "to 12 volts" of one of the batteries is quite normal in new lead acid batteries after a period of moderate discharge. It's to do with the consolidation and purification of the lead in the plates.

Healthy batteries immediately after coming off a correctly set up charging system can be measured at 14.4 volts or thereabouts but will settle to around 13.9 after a period of standing and hold most of this for a very long time. The actual charging voltage will be around 16 volts. Don't be alarmed, some solar panels output at 18.5 volts when not connected to a battery.

Seems to me on initial consideration that you started out with only partly charged batteries - the initial engine start- was it quick for this wouldn't help if you were slowly starting from the domestics - and that something discharged the rest - were they TOTALLY flat when you arrived at destination?

Before we go into WHAT was causing the discharge -assuming that the batteries are not faulty - get them load tested first - you need to address the basics and as others have said, CONNECTIONS are all important. On a new-to-me boat I'd always run through them all, cleaning and greasing as I went.
Is the earth return strap in good condition on the return from the engine to the batteries for example.

The more I think about it though and it's very difficult to be certain without seeing the installation, it would appear that the problem is most likely to be in the alternator where if part of the diode rectifier has become conductive in both directions then it will short the battery. Alternatively, "Terminal W" where the rev-counter gets it's input from is connected to one end of each field winding. This could be shorting out inside the rev-counter or even in the interconnecting wiring. Since this connection and the alternator charge lead remain connected to the battery when the engine is not running although the power to the rev-counter circuit board IS, a failure here would still result in a discharge, even when the mains charger was connected. If you had a diode splitter charging into two seperate battery banks, such a discharge path would be illiminated as current from either bank could not flow backwards across the splitter.

Don't start the engine but disconnect the charge lead from the alternator and leave the Sterling mains charger attached. If the lights come up bright, then the charger ISN'T your problem and the alternator or rev-counter with associated connections probably IS. If, when you pull the lead off of terminal W, everthing is Ok then the rev-counter is the problem. However this is the least likely IMO. I would put my money on the rectifier array in the alternator (is it the original on an elderly T80?) but as I said initially, you have a complex problem and without seeing it, none of us can be certain.

Steve Cronin
 
A very quick way of doing this is to try to start the engine, first on 1 then on 2. If it starts happily, your batteries are reasonably charged - and you're looking for a wiring fault on your 'domestics' distribution: either earth or supply.

If the engine doesn't turn over in either case, you don't know what the problem is, so you've got to eliminate the suspects from you enquiries. Disconnect each battery completely and check the voltage across its terminals with a digital voltmeter.

If the voltage is over 12.5, it should have turned the engine over, so there's a wiring fault.

If the voltage is below 12, you've got a battery/charging/discharging problem.

This may be long slow discharge over time (something left switched on? bilge pump permanently running?) plus lack of charging, or it may be a gross discharge bigger than the charge rate. If the latter, there would have been heating somewhere. Eliminate these possibilities by connecting your battery via a (big enough capacity) ammeter and look for the discharge, first with everything switched off, then switching things on one at a time.

Boring detail, takes time, but the cost of decent little V/A meter is much less than an hour of the electrician's time!

If you've got the time, that is . . . .
 
Steve,

I am going down to my boat tomorrow night and will be in a much better position to answer your questions once I have had a good look. Thank you very much for taking the time to help with this, I really appreciate it. I hope others get as much benefit from your wisdom as I am.

Unfortunately the boat is now on a swinging mooring so I will not be able to check the system with shore power. That said, when we did switch on the lights the batteries were connected throughout; everything just got dimmer and weaker - even the lights on the Sterling until eventually we gave up.

Assuming the batteries were shot I anticipated having to replace them soon. Shortly thereafter I had the engine serviced and the engineer reckoned he needed to reposition the alternator to ensure the belt was properly tensioned. Arrived at the boat yesterday morning and she started first time. I assumed the alternator was now charging properly and the batteries were back in condition. Switched off, went off for 30 minutes, came back, switched on, drove the boat out of the lock to the re-fuelling jetty and off again. Running perhaps for 20 minutes.

Came to start and not enough power to turn the engine over...if it had been a car with a single battery I would have assumed a dead cell. With a determination to press home I dealt with the symptoms, not the problem and popped into the chandlers to buy two new batteries (thinking at least they would hold their charge, so worth replacing and have done with it).

Once we knew we had a problem it seemed as though the rev counter was somehow indicating the battery strength..slowly falling over a period of time. 2200 to 1800rpm everything else was fine, then we noticed all other instrument dimming and switched them off. The rev counter stabilised at 1200 for about 30 minutes then continued its path to 0.

I don't have enough experience with this to make assumptions, but there did appear a correlation between rev counter and battery state. I thought I would take the alternator off and get it checked - at least that can eliminate one major component.

I will report back on the wiring set up tomorrow. I will also make provision for an 85Ah engine start battery. I'm not facing the same situation again!

Thank you

H
 
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