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Batteries charging at 17 volts


Wakes

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Just had some repairs and service done on my Lister SR2 engine after it completely packed up and have now noticed that the batteries are reaching up to 17volts when at full throttle with the battery selector switch set to ‘both’ or position 1 (leisure batteries). If I select position 2 (starter battery) then it is around 14v as normal. 

 

Both sets of batteries have taken quite a hammering recently with the number of times the engine had been cranked prior to the repair so did wonder whether a fault had developed on one of the leisure batteries causing it to over charge? I then disconnected the batteries and checked the voltage and they were all around 13 volts. I always keep the batteries charged on shore power but it seems strange that it would register such high voltage so was thinking more likely the alternator. As far as I’m aware it wasn’t touched when the repairs were done as the injectors and fuel system were causing the original problem. Any help most appreciated.

Wakes.

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A battery fresh off change may well show 13 volts or more, even totally shot ones.  Its surface charge and no use in fault finding. You need to let them rest for several,hour or run (say) the water pump for 10 minutes or so and then take a reading.

 

17 volts at any throttle position is too high for a 12V system and I can't think of a reason why having the switch set to both would do this. I can think that if the a battery sensed alternator or something with an external advanced controller was connected to the domestic bank the if the switch was set to just the engine bank you could get a  high voltage but not if it is set to both and proper contact is made within the switch. This assumes teh1,2,both, off switch is not wired as a simple charge section switch. If it is then if there is a sense lead it may need moving to the switch rather than one battery bank. If its a machine sensed alternator then I don't see how you can get 17V without an alternator fault.

 

AS Rusty says, start checking for poor connections etc.

 

 

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7 minutes ago, Wakes said:

So it’s definitely not a damaged battery then? The alternator is ancient, looks as old as the boat, 30 odd years prob knackered. Thanks for your help guys...

If a battery is "damaged" it is likely to either suffer and internal short and when that gets bad it will pull the charging voltage down or be badly sulphated and in that case it would charge very quickly but the alternator's regulator should clamp the voltage at a safe level.

 

Apart from the fact the voltage is 14V on the engine battery I would feel its the alternator but I cant see how that can be with that 14V UNLESS the engine battery is shorting or very flay (not likely if you can start it) and thereby drawing loads of current and pulling the charging voltage down. But it would do the same with the switch set to both.

 

At present I can't give any opinion of a likely cause. It would help if we knew  if the alternator is battery or machine sensed but most are machine sensed and if it has an external controller. But even then it is still all rather odd.

 

17 volts just about might be a equalisation voltage from a solar or land line charger or an external  alternator regulator but even so it does not explain differing voltage with the switch in different positions. If anything I would expect the higher load when set to both would pull the voltage down, not push it up.

 

Where are you getting the voyage readings from. if its a multi-meter does it have a new battery in it? Flat meter batteries give all sorts of odd readings.

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3 minutes ago, Tony Brooks said:

Where are you getting the voyage readings from. if its a multi-meter does it have a new battery in it? Flat meter batteries give all sorts of odd readings.

I was going to suggest the same (I got 19v when my meter battery was flat), but I just couldn't work out how using to measure the starter battery gave the correct voltage, but measuring the leisure battery gave 17v.

 

I was even trying to work out a way that a (flat) 24v system could give 17v.

 

I'm stumped !!

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I recently connected a cheap 150w solar panel to the leisure batteries come to think of it. I only noticed the high reading this morning when I looked at the controller and noticed the reading was very high. I then looked at the displayed reading from a different 12v socket outlet and it mirrored this, as well as using a multimeter on battery with voltage only going down when I decreased the revs. I’m now wondering if this has boosted the voltage, I’m not sure how though as it would hardly have anything going through it this time of year..

Edited by Wakes
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18 minutes ago, Wakes said:

I recently connected a cheap 150w solar panel to the leisure batteries come to think of it. I only noticed the high reading this morning when I looked at the controller and noticed the reading was very high. I then looked at the displayed reading from a different 12v socket outlet and it mirrored this, as well as using a multimeter on battery with voltage only going down when I decreased the revs. I’m now wondering if this has boosted the voltage, I’m not sure how though as it would hardly have anything going through it this time of year..

Does your solar panel have controller connected between it and the battery and if so did you connect the batteries to the controller FIRST, before connecting the panel? Although the readings still make little sense If a solar controller has been fooled into thinking its connected to a 24 volt system by connecting the batteries last then you may get 17 volts from the solar. Try the measurements again now its dark or cover the panel in the morning. This is a question of eliminating possible causes one at a time so we must eliminate the solar first.

 

A solar panel off load will probably produce anything between about 21 and 35 volts or more. With the alternator charging well charged batteries then you might have been measuring solar open circuit voltage.

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Yes I also have a 12v socket with a digital reading. The solar panel came off Ebay, a cheapy probably from China which I connected myself, I don’t live on boat just wanted something simple for cruising. I will check to see if this is the cause tomorrow. The controller has never given me the amp reading as to how much charge is going into the batteries, always says 0 but does give me the battery voltage. I think it is working ok though as was off shore power last summer for couple of days and batteries stayed higher for longer. I’m not sure if I connected batteries first before panel, why would this matter? I didn’t connect a fuse in

the end as I bought the wrong fuse holder and haven’t got round to doing it yet.

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6 minutes ago, Wakes said:

Yes I also have a 12v socket with a digital reading. The solar panel came off Ebay, a cheapy probably from China which I connected myself, I don’t live on boat just wanted something simple for cruising. I will check to see if this is the cause tomorrow. The controller has never given me the amp reading as to how much charge is going into the batteries, always says 0 but does give me the battery voltage. I think it is working ok though as was off shore power last summer for couple of days and batteries stayed higher for longer. I’m not sure if I connected batteries first before panel, why would this matter? I didn’t connect a fuse in

the end as I bought the wrong fuse holder and haven’t got round to doing it yet.

Because the controller may see the solar open circuit voltage and set itself for a 24 volts system. Most controllers are dual voltage and set themselves when they see the battery voltage.

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If that is so, is it possible to unfool it so it no longer believes it’s a 24 volt system? ? Also, if the batteries are fully charged, will the controller not show any ingoing amps because of this? The bloody thing has never worked properly anyway!

Edited by Wakes
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9 minutes ago, Wakes said:

If that is so, is it possible to unfool it so it no longer believes it’s a 24 volt system? ? Also, if the batteries are fully charged, will the controller not show any ingoing amps because of this? The bloody thing has never worked properly anyway!

1. I would disconnect the panel from the controller. The disconnect the batteries from the controller, leave a few hours or longer and then reconnect the batteries first, then the controller. The longer you can leave it disconnected the better in case the "memory" is internal battery or capacitor backed.

 

2. Depends upon how accurate and how many decimal points the controller can display. With lead acid batteries it should always show a low charge unless the solar voltage is lower than battery voltage.

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17 hours ago, Tony Brooks said:

1. I would disconnect the panel from the controller. The disconnect the batteries from the controller, leave a few hours or longer and then reconnect the batteries first, then the controller. The longer you can leave it disconnected the better in case the "memory" is internal battery or capacitor backed.

 

2. Depends upon how accurate and how many decimal points the controller can display. With lead acid batteries it should always show a low charge unless the solar voltage is lower than battery voltage.

 

 

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Just disconnected the panel and controller from batteries and still exactly the same. Started the engine with only one leisure battery connected, then disconnected and tried the other on its own and still the same. Only gives out correct voltage when selector switch is on starter battery only. 

 

This is problem has only arisen since the engine was repaired. Had problem with fuel system and injectors but since the repair, engine possibly now appears to race quicker and has more power so I don’t know if this is putting more load through to the alternator? Seems strange that this problem has arisen since the engine repairs....

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I've not re-read the whole thing, but if it is a 12 volt system, and the reading is anywhere close to correct that it is charging at 17 volts, I would expect serious problems with your batteries, and quite quickly.  We had a fault on an alternator that resulted in less of an overcharge than that, and the batteries got hot and gassed heavily.  They were fairly tired anyway, but almost certainly it resulted in them having to be replaced sooner than I had hoped.

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7 minutes ago, Wakes said:

Just disconnected the panel and controller from batteries and still exactly the same. Started the engine with only one leisure battery connected, then disconnected and tried the other on its own and still the same. Only gives out correct voltage when selector switch is on starter battery only. 

 

This is problem has only arisen since the engine was repaired. Had problem with fuel system and injectors but since the repair, engine possibly now appears to race quicker and has more power so I don’t know if this is putting more load through to the alternator? Seems strange that this problem has arisen since the engine repairs....

But engine repairs means fiddling with the wires, either intentionally to get access to other bits, or accidentally........

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7 minutes ago, Wakes said:

Just disconnected the panel and controller from batteries and still exactly the same. Started the engine with only one leisure battery connected, then disconnected and tried the other on its own and still the same. Only gives out correct voltage when selector switch is on starter battery only. 

 

This is problem has only arisen since the engine was repaired. Had problem with fuel system and injectors but since the repair, engine possibly now appears to race quicker and has more power so I don’t know if this is putting more load through to the alternator? Seems strange that this problem has arisen since the engine repairs....

It just does not seem logical that the alternator connected to 'one' battery is outputting 17 volts, but connected to another battery is only outputting 13 - 14 volts

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The readings on my solar controller, 12v sockets outlet display and multimeter when the engine is running and gradually moving the throttle up, the voltage gradually increases over 17 volts except when the battery selector switch is in position 2 (starter battery only) which is normal voltage up to about 14v. Why would the alternator output higher voltage to only the leisure batteries??? 

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6 minutes ago, Wakes said:

No, I only know how to measure the battery voltage 

And you are doing that by :

 

Looking at the voltage on your solar controller &

Taking reading with a 'cigarette lighter' type plug inti a socket meter.

 

How do you know how much volt drop you have between the batteries and the '12v socket'.

You could be actually getting 24 volts at the battery and a 'few' volts volt drop down the wires to your 12v sockets.

 

you MUST use a multimeter  and test the voltage in 2 places :

 

On the output terminals of the alternator &

On the battery terminals. (Both with, and without the engine running, for both the 'leisure' battery(s) and the starter battery).

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52 minutes ago, Alan de Enfield said:

It just does not seem logical that the alternator connected to 'one' battery is outputting 17 volts, but connected to another battery is only outputting 13 - 14 volts

 

Well itakes sense to me, possibly. We have a. One or both battery switch. When one is selected, the alternator is connected by itself to just the start batt, while the voltage readings are still only being taken  from the domestic wiring. The solar is connected to domestic which is where 14v is coming from, and when both is selected on the switch, both sets of batteries are exposed to the faulty alternator 17v. 

  • Greenie 2
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1 minute ago, Mike the Boilerman said:

 

Well itakes sense to me, possibly. We have a. One or both battery switch. When one is selected, the alternator is connected by itself to just the start batt, while the voltage readings are still only being taken  from the domestic wiring. The solar is connected to domestic which is where 14v is coming from, and when both is selected on the switch, both sets of batteries are exposed to the faulty alternator 17v. 

I was thinking that but :

 

1 hour ago, Wakes said:

Started the engine with only one leisure battery connected,

 

then disconnected and tried the other on its own and still the same.

 

Only gives out correct voltage when selector switch is on starter battery only. 

I understand what you are saying.

As he is using his domestic wiring (12v socket) for testing in both occasions he is only going to show the 'domestic battery voltage' when the alternator is charging the starter battery, and is going to show the alternator voltage if the 'switch' is in 'both' position.

 

It may indicate that the alternator regulator is 'shot'.

 

We will only know if he tests in the correct places.

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