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Leisure batteries not charging, maybe alternator broken?


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Hi we have a sticky problem with our batteries – I’ve very much bottomed out my very limited knowledge and understanding, so looking for advice and recommendations.
[TL:DR] Batteries not charging from the engine, new batteres didn't solve, engine sluggish to start, no raised charging voltage with enging running, maybe alternator broken?
Here’s the more detailed version:
Our set up had a single alternator on our diesel engine, 1 starter battery, 3x 130 AH sealed lead leisure batteries in parallel, a solar system, a relatively recently installed 240v inverter. I don’t really know anything about how it is all wired up and as far as I can tel we have no “battery charger” – everything is just wired into the alternator I think.
We are live aboard continuous cruisers and we use little power – no fridge or tv or anything heavy. But sometimes we use laptops off the inverter.
Here’s what happened:
Our leisure batteries dropped to about 11v (because it’s our first autumn and we didn’t monitor them enough or know how low they could go)
They stopped holding charge and didn’t seem to be charging from running the engine (at one point they reached 11.8v from around 3 hours running the engine in idle then dropped back to 11.2 within a couple of hours). During this time we had no problem getting poer out of them – all lights and water pump and so on seemed just fine.
We figured we had fried them though and so we have replaced them (with 2 x 90 ah AGM batteries). These read 12.5 v on the volt meter when we installed them
The Starter battery shows 12.2v on a voltmeter.
When I start up the engine the voltage on the dial in our control panel (next to the throttle) drops to 11.5v then kicks back up to about 12v ish and stays there (it used to go up to about 14.5v). The yellow charging light beside out ignition never goes out (which it used to when we revved high) – it flickers at low revs and is steady at full revs. The engine is much more sluggish to start than it used to be – though the weather is colder now…
Using the volt meter with the engine running I now get 12.2 volts on all batteries, starter and leisure.
Weirdly the voltage of my leisure batteries started to drop…. I turned off the engine!
Without the engine running the voltmeter and solar controller both now showed about 12.3v for the leisure batteries.
Yesterday with a bit of sun the solar charged up our leisure batteries so the voltage displayed on the solar controller showed 13v.
I think our alternator is NOT charging anything, and maybe charge is draining into the system somehow… but I don’t know electrics really at all…
I don’t know what to do next… and I’m pretty worried we are going to fry our new expensive batteries because we can’t charge them.
We are using as little power as we can get away with and hoping we can get it fixed sooooon… any and all help, advice and recommendations super welcome!

Hppy to supply any extra info or photos that might help.

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1. You should never charge at idle, without an ammeter for modern engines  about 1200 to 1500 rpm. If it's an air-cooled Lister there are probably other problems to solve re the revs.

 

2. With a single alternator you must have some type of charge splitting between the engine and domestic bank. The falling voltage while the engine is running suggest to me that the engine battery may have an internal short that drains the domestic bank when the charge splitter joins the two banks, so what type of charge splitter do you have? Photo if you don't know what it is.

 

3. As long as the alternator drive belt is in good order and correctly tensioned, I suspect you may well be correct about a faulty alternator.

  • Greenie 1
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Hi Tony,

Thanks for replying

1. So I think I have said idle when I mean something else - I just mean that the prop wasn't engaged, I had the engine running at fairly high revs (I dont have a rev counter so dont know exacly). We have a water cooled kubota (we have skin tanks)

 

2. Ah ok, then yes we mush have one - I will see if I can work out where and what the charge splitter is when I'm back at the boat and try to take some photos. Could such a short develop? As I dont think its always had this problem.

 

3. I will check the tension - do you have any advice how I tell if it is correct? the belt seems in good order to me.

 

Thanks again, I'll try and investigate what our system is in more detail.

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14 minutes ago, Wandering Lark said:

Hi Tony,

Thanks for replying

1. So I think I have said idle when I mean something else - I just mean that the prop wasn't engaged, I had the engine running at fairly high revs (I dont have a rev counter so dont know exacly). We have a water cooled kubota (we have skin tanks)

 

2. Ah ok, then yes we mush have one - I will see if I can work out where and what the charge splitter is when I'm back at the boat and try to take some photos. Could such a short develop? As I dont think its always had this problem.

 

3. I will check the tension - do you have any advice how I tell if it is correct? the belt seems in good order to me.

 

Thanks again, I'll try and investigate what our system is in more detail.

 

1. Fine, that is as it should be.

 

2. Yes, all batteries will develop internal shorts when they get old enough and have shed enough plate material. They will do it faster if you abuse them with deep discharges and attempt fast recharging.

 

3. Ordinary V belt - about 10 mm deflection in the middle of the longest run under moderate finger pressure.

 

Wide, flat polly V belt - use a tension gauge is the correct way, but many tighten it until they can just twist the belt through 90 degrees in the centre if the longest run.                  

Edited by Tony Brooks
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4 minutes ago, Tony Brooks said:

 

1. Fine, that is as it should be.

 

2. Yes, all batteries will develop internal shorts when they get old enough and have shed enough plate material. They will do it faster if you abuse them with deep discharges and attempt fast recharging.

 

3. Ordinary V belt - about 100 mm deflection in the middle of the longest run under moderate finger pressure.

 

Wide, flat polly V belt - use a tension gauge is the correct way, but many tighten it until they can just twist the belt through 90 degrees in the centre if the longest run.                  

10mm was intended Tony?

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Thanks for all your help. I just took my alternator to a workshop here where they bench tested it and the alternator is totally fine. It turns out they supplied it only 1.5 years ago - I wonder if the previous owner had trouble that they never bottomed out.

From here what do you think our next steps should be? Tracing all the wiring and looking for corroded contacts? Replacing the starter battery? We are still limping by with solar and ultra low battery electrical usage so any help much appreciated!

 

Edited by Wandering Lark
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Before we can go any further, you really need to answer the question about the type of charge splitter I asked within half an hour of your original question. A photo will go  along way to help identify it.

 

The wiring for different type of charge splitters is different, so we can't work out a likely fail point until we know what you have.

 

Right, now the guessing begins.

 

Single alternator boat in London probably means an elderly boat that may well have an ancient split charge diode. Charging to both battery banks pass through diodes, so not only does that cause a loss of charging voltage, but also one failed diode would prevent one bank charging and two would prevent both banks charging. Ditto loose or dirty connections or terminals at the diode.

 

A split charge relay or a VSR has the alternator connected directly to one bank, so in that case a failure only prevents the other bank charging.

 

Split charge diodes have three thick battery cables connected to them

A split charge relay has two thick cables and two thin ones.

A Voltage sensitive relay has tow thick cables and one thin cable.

 

I am discounting the possibility you may have an Alternator to Battery charger fitted because they are newish and expensive.

 

I don't think that you have identified the alternator. Some have more wires on them than others, all of which are required for correct operation. Can we please have a photo of the alternator, especially the end with the wires on?

 

Finally, if this is a newish boat, you may have a big multi-pin connector in the wiring harness that runs from engine to control panel. They are notorious for playing up and giving all sorts of odd symptoms.

 

 

 

 

 

 

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Since both batteries (engine and leisure) aren’t being charged, I think we can discount a spilt charge issue. The alternator warning light is staying on, that means the alternator isn’t working.

 

The drop in leisure battery voltage might be due to the split charge system connecting the batteries together when the engine is running - the starter battery taking a bit of charge from the leisure batteries.

 

You say the alternator checks out fine on the bench, so that leaves the wiring. We need a photo of the wiring connections on the alternator, and the alternator generally so that the experts can identify it. There are two main types of alternator, with different wiring, so we need to know which type it is.

 

Armed with that we can advise what voltages should be present on the alternator terminals and you can check it out with a meter.

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8 minutes ago, nicknorman said:

Since both batteries (engine and leisure) aren’t being charged, I think we can discount a spilt charge issue. The alternator warning light is staying on, that means the alternator isn’t working.

 

The drop in leisure battery voltage might be due to the split charge system connecting the batteries together when the engine is running - the starter battery taking a bit of charge from the leisure batteries.

 

You say the alternator checks out fine on the bench, so that leaves the wiring. We need a photo of the wiring connections on the alternator, and the alternator generally so that the experts can identify it. There are two main types of alternator, with different wiring, so we need to know which type it is.

 

Armed with that we can advise what voltages should be present on the alternator terminals and you can check it out with a meter.

 

I think that you may be wrong there if it's a split charge diode. If both diodes are open circuit then no charge can get to the batteries and if the alternator energises there may well be enough voltage/current to illuminate the warning lamp from the field diodes and flowing back through the light to try to charge that batteries via the ignition switch - flowing backwards to the normal way.

 

I am assuming the warning lamp has a decent bulb in it and not a grain of wheat or an LED so photo of warning lamp as well.

Edited by Tony Brooks
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33 minutes ago, Tony Brooks said:

 

I think that you may be wrong there if it's a split charge diode. If both diodes are open circuit then no charge can get to the batteries and if the alternator energises there may well be enough voltage/current to illuminate the warning lamp from the field diodes and flowing back through the light to try to charge that batteries via the ignition switch - flowing backwards to the normal way.

 

I am assuming the warning lamp has a decent bulb in it and not a grain of wheat or an LED so photo of warning lamp as well.

I suppose that is possible, but with only a couple of volts across a 12v bulb it’s going to be extremely dim. If the lamp is  bright before starting, then goes very dim with the engine running, this would support your hypothesis.

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Almost every alternator I bench test works. Even the ones with worn out brushes and burnt slip rings. The light flickering suggests that. When I test an alternator I always visually inspect the brushes. It is amazing how often the disturbance of removing and transporting the thing will shake another ten minutes out of it. What type of alternator is it?

  • Greenie 1
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38 minutes ago, Tony Brooks said:

Tempted to suggest it may be a self drilling ACR :giggles:

Well you say that, but....

If a slip ring gets a bit of oil or fuel contamination then, counter intuitively, it wears out rapidly. The rings themselves turn into a copper wire wool looking stuff that is obviously conductive and has little fires that melt brush holders. A127 is very prone to it since the slip ring is unshielded and anything getting in from above will find its way there. 

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HI All - thanks for staying on the trail - I took some photos the other day so here they are - I'm not sure if they show what you are asking for so let me know if not and I'll take more this evening.

Thats frustrating that the Alternator may be burned out dispire the bench test saying its not - I thought I had ruled that out - I know he didnt visually inspect anything just put it into his machine and checked the readouts.

The search continues.

O

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My boat was built in the mid to late 80's so indeed it is fairly old-ish.

this last picture is taken from above the switch showing whats inside the cabinet behind it.

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Not the photo  that would have allowed us to identify the alternator, that is why I asked for a photo of the end where the wires attach. It looks a bit like an A127 but as I can't see the wire end nor read the numbers on that label so I can't be sure. If it is an A127 then take note of what SirNIbble said about brushes. Once we can see the wire end, we can tell you if you can check the brushes.

 

The charge spitting is done by a B1, B2, Both and off manual switch and they are normally tolerably reliable but they too have "brushes" rubbing on a brass or copper ring, be it that the "brushes" are bent bits of bronze.  If it is not set to BOTH then one battery bank, the other, or neither would charge. I can see a small wire associated with that switch, and some of that type of switch made provision for turning the alternator off as the switch is moved. I don't think your alternator would allow that without modification so that wire may be unused or a feed for something else. If the switch is worn, it might cause odd charging symptoms, but it is also likely to get hot when starting and smell - often a bit fishy.

 

I also asked for a photo of the warning lamp because some cheaper types are not suitable for most alternators.

 

Let's have the photo of the wire end of the alternator and the warning lamp, then we might be able to advise further.

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Hi All - I havent refitted the alternator yet - bit pressed for time at the mo, but once I do I'll try the hand turning tip.

In the meantime here are photos of the lamp

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and here are photos of the plug end of the alternator and the block that would normally be plugged into it. Also clearer photos of the lables.

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The yellow lamp almost certainly has a grain of wheat bulb in it, they often do not pass enough current to energise the alternator  and for some reason the blades have been badly bent - I don't know why. Do this test after trying  what Sir N said, although I think the alternator looks nearly new.

 

Refit the lamp.

 

Turn ignition on and make sure the lamp illuminates. Do not start the engine.

 

Pull the black plug out of the alternator. The lamp should go out. If it does not then There is something wrong with the wiring.

Run a new cable from the bulb to the alternator. Use the small blade on the alternator but make sure the terminals are tight at both ends.

 

If the light did go out, refit the plug.

Start and  run the engine at about 1200 rpm and then join the two terminals on the wires that are connected to the warning lamp. I hope the battery voltage will jump up, and the engine come under load. If it does, then it's charging, so get a new warning lamp with a removable bulb. Other versions of that lamp that cost a little more use a 1.5 watt bulb. They will usually do. Anything up to about 4 or 5 watts will do. See below*

 

I would take the three wires out of the plug so  you can make sure they are tight o the blades, There is a hint that they are loose and have been overheated. On NO ACCOUNT allow one of the large terminals to tough the alternator body, if you do, you will get a big spark. Personally I would put both thick cables into an eye terminal and fit it to the B+ stud, it's a far better connection, but get it charging first.

 

* Normally one would make a temporary connection between the B+ and the small blade on that alternator, but with the plug it is likely to be easier to do it at the warning light end.

Edited by Tony Brooks
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  • 3 weeks later...

Hi All,

Appologies for the dissapearing act - I got extremely busy with work and had to stop focusing on this.

I have though reffitted the alternator and weirdly everything worked again! So I suspect that the fault was with the connections in the plug at the back of the alternator. Today I jimmied the alternator arround to adjust the belt tension and the problem returned, then when I switched off the engine, jimmied the plug and wires about, restarted the engine, the problem resolved.

 

So hopefully thats the issue  -I'm going to do some reading as I dont know what B+ etc refer to, then run through Tony's suggestions to try and isolate the problem propperly and then attempt to make the connections more seccure as you suggest above with eye terminals.

But in the meantime I seem to be able to charge the batteries so the immediet problem is resolved... Now to try and work out why the engine is running so hot...(its one thing after another at the moment)

Thanks again, I'll let you know how I get on as I keep tinkering with this issue.

Oliver

 

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A typical alternate, but not so much very modern ones, have up to five terminals. A large one (often marked B+) is the main positive output terminal that in some way runs to the battery +.  They may or may not have another large one (often marked B-) that is the connection to the negative battery terminal. If there is not one then the case is the negative charging connection.

 

A small one where the warning lamp connects, this is usually referred to as D+ but may have other markings on the alternator case.

 

It may or may not have another similarly sized one that is often marked W that feeds pulses to a rev counter if it is connected.

 

Finally there is often a 6mm blade hidden down a small rectangular hole. This is for a radio suppressor. The suppressor these days is often a small rectangular plastic box connected to this terminal  but for boat use you can ignore both the terminal and the suppressor.

 

Unless we can see the back of the alternator we can't give more specific advice.

 

 

 

 

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12 minutes ago, Tony Brooks said:

A typical alternate, but not so much very modern ones, have up to five terminals. A large one (often marked B+) is the main positive output terminal that in some way runs to the battery +.  They may or may not have another large one (often marked B-) that is the connection to the negative battery terminal. If there is not one then the case is the negative charging connection.

 

A small one where the warning lamp connects, this is usually referred to as D+ but may have other markings on the alternator case.

 

It may or may not have another similarly sized one that is often marked W that feeds pulses to a rev counter if it is connected.

 

Finally there is often a 6mm blade hidden down a small rectangular hole. This is for a radio suppressor. The suppressor these days is often a small rectangular plastic box connected to this terminal  but for boat use you can ignore both the terminal and the suppressor.

 

Unless we can see the back of the alternator we can't give more specific advice.

 

 

 

 

I wonder if its one of these

Lucas/Bosch Alternator Plug

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