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Post by ianali on Mar 29, 2021 5:58:57 GMT
When a friend started his boat last Friday, which hadn’t been run since last October, the charge voltage went up to 15.1 volts within a couple of minutes. He ran the engine for 30 minutes then turned it off. Batteries(4x 100A sealed LA) have been on float at 13.6v all winter. He put batteries back onto his battery charger and they were taking 14.7v charge. He left and returned next morning to check on them and they were back on float at 13.6v. He is intending to go back to the boat and start up again and see what charging he gets. Obviously he’s concerned at the 15.1 v he was seeing. Can anyone cast a light on this issue? Might it simply be that he needs to run the engine a while and hope the charging settles down to a normal figure? He has checked batteries for heat build up and swelling and they appeared ok. Thanks, Ian.
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Post by Telemachus on Mar 29, 2021 7:08:10 GMT
The batteries are chokka full, so in order to keep the voltage down, the alternator regulator needs to almost completely shut the alternator down. Sometimes there can be residual magnetism which means that even with zero rotor current, the alternator still produces some power. Or could be a failed field diode or faulty regulator. I would try it with some significant load on (eg tunnel light, if it is incandescent), discharge the batteries a bit and see what happens. Is there any hint of a faintly-glowing alternator warning light when the engine is running?
But as a general point, without more detail of the boat’s charging setup and where the voltage is measured, it’s difficult to be precise. For example, “the charge voltage went up...” but the charge voltage where, and measured how? Modern Beta engines (at least) have two alternators, one for engine battery and one for leisure batteries. There is a voltmeter on the panel but this shows engine battery voltage, not leisure battery voltage.
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Post by ianali on Mar 29, 2021 7:55:26 GMT
The batteries are chokka full, so in order to keep the voltage down, the alternator regulator needs to almost completely shut the alternator down. Sometimes there can be residual magnetism which means that even with zero rotor current, the alternator still produces some power. Or could be a failed field diode or faulty regulator. I would try it with some significant load on (eg tunnel light, if it is incandescent), discharge the batteries a bit and see what happens. Is there any hint of a faintly-glowing alternator warning light when the engine is running? But as a general point, without more detail of the boat’s charging setup and where the voltage is measured, it’s difficult to be precise. For example, “the charge voltage went up...” but the charge voltage where, and measured how? Modern Beta engines (at least) have two alternators, one for engine battery and one for leisure batteries. There is a voltmeter on the panel but this shows engine battery voltage, not leisure battery voltage. Thanks Nick. From memory I believe he has a Beta 38. Has twin alternators for sure. He was reading the voltage on his charger/inverter display. I did suggest he puts a load on the batteries for a few minutes prior to start up. I did wonder if with them being full they might be confusing the alternator somehow. Thanks for your better explanation. Il let you know what happens. Cheers, Ian. |
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Post by Telemachus on Mar 29, 2021 8:06:21 GMT
The batteries are chokka full, so in order to keep the voltage down, the alternator regulator needs to almost completely shut the alternator down. Sometimes there can be residual magnetism which means that even with zero rotor current, the alternator still produces some power. Or could be a failed field diode or faulty regulator. I would try it with some significant load on (eg tunnel light, if it is incandescent), discharge the batteries a bit and see what happens. Is there any hint of a faintly-glowing alternator warning light when the engine is running? But as a general point, without more detail of the boat’s charging setup and where the voltage is measured, it’s difficult to be precise. For example, “the charge voltage went up...” but the charge voltage where, and measured how? Modern Beta engines (at least) have two alternators, one for engine battery and one for leisure batteries. There is a voltmeter on the panel but this shows engine battery voltage, not leisure battery voltage. Thanks Nick. From memory I believe he has a Beta 38. Has twin alternators for sure. He was reading the voltage on his charger/inverter display. I did suggest he puts a load on the batteries for a few minutes prior to start up. I did wonder if with them being full they might be confusing the alternator somehow. Thanks for your better explanation. Il let you know what happens. Cheers, Ian. Ok fair enough. It will be interesting to know what happens with some load on. I think it is fair to say that an alternator SHOULD be able to cope with completely full batteries, so probably there is something wrong with it, but it is a question of how much of a problem that causes under normal conditions with some load from boat services. Any hint of a faintly-glowing (maybe only visible in the dark) alternator warning light points to a blown field diode inside the alternator. |
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Post by ianali on Mar 29, 2021 8:52:06 GMT
Thanks Nick. From memory I believe he has a Beta 38. Has twin alternators for sure. He was reading the voltage on his charger/inverter display. I did suggest he puts a load on the batteries for a few minutes prior to start up. I did wonder if with them being full they might be confusing the alternator somehow. Thanks for your better explanation. Il let you know what happens. Cheers, Ian. Ok fair enough. It will be interesting to know what happens with some load on. I think it is fair to say that an alternator SHOULD be able to cope with completely full batteries, so probably there is something wrong with it, but it is a question of how much of a problem that causes under normal conditions with some load from boat services. Any hint of a faintly-glowing (maybe only visible in the dark) alternator warning light points to a blown field diode inside the alternator. Thanks again Nick. Il pass this on. Should actually see him later at the marina. Hope you find yours all well and ready to go. |
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Post by ianali on Mar 29, 2021 11:35:06 GMT
So. Charging still high at around 15v. Have turned on various appliances from fridge to hair dryer. He has a BM-2 which is showing about .2 to .5 amps going in at 15v with all electric stuff turned off. Turn on appliances and the amps read as I’d expect and v drop to between 13.1 and 13. 7 depending what’s being powered. So all seems fine apart from the high reading when batteries are full. Question! As there’s virtually no amps going in at 15v does that mean it’s safe to say the batteries shouldn’t be overcharging? He knows it needs looking at, but wants to boat a bit until he finds a man to sort the problem out.
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Post by Deleted on Mar 29, 2021 11:58:20 GMT
I'd have a look at the warning lamp when running. Preferably well shaded. It might be flowing slightly as Nick suggested which would indicate a diode problem.
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Post by tonyb on Mar 29, 2021 12:57:51 GMT
Voltmeter between B+ (main pos) and d+ (warning lamp terminal) on the alternator and run engine at varying revs and with varying loads. In theory it should read zero but because the field and main diodes are usually different it may read a few 1/10ths of a volt. If it reads more then (say) 0.5V then it confirms a field diode has probably failed.
Is it by any chance a battery sensed alternator or is it fitted with an alternator controller that is battery sensing. If so there may be resistance in the sense wire or it could be disconnected. 15V seems as if it might be a fallback setting of the regulator for use when something goes wrong.
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Post by Telemachus on Mar 29, 2021 19:37:58 GMT
Ok fair enough. It will be interesting to know what happens with some load on. I think it is fair to say that an alternator SHOULD be able to cope with completely full batteries, so probably there is something wrong with it, but it is a question of how much of a problem that causes under normal conditions with some load from boat services. Any hint of a faintly-glowing (maybe only visible in the dark) alternator warning light points to a blown field diode inside the alternator. Thanks again Nick. Il pass this on. Should actually see him later at the marina. Hope you find yours all well and ready to go. Thanks, everything fine with the boat, just the shore bollard breaker had tripped or been turned off. Phew! |
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Post by Telemachus on Mar 29, 2021 19:42:28 GMT
So. Charging still high at around 15v. Have turned on various appliances from fridge to hair dryer. He has a BM-2 which is showing about .2 to .5 amps going in at 15v with all electric stuff turned off. Turn on appliances and the amps read as I’d expect and v drop to between 13.1 and 13. 7 depending what’s being powered. So all seems fine apart from the high reading when batteries are full. Question! As there’s virtually no amps going in at 15v does that mean it’s safe to say the batteries shouldn’t be overcharging? He knows it needs looking at, but wants to boat a bit until he finds a man to sort the problem out. 15v with sealed calcium rich batteries is pretty marginal. If you’d said 14.8, maybe OK. 15 might cause a bit of gassing. 1/2 an amp obviously isnt a lot but that will nearly all be going to convert the limited supply of water in the electrolyte, to hydrogen and oxygen. I wouldn’t recommend doing that for long periods, but a few hours will be OK. If he just turns on some loads all the time he is cruising, that might drop the voltage by a few 10ths and take it below gassing voltage. |
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Post by ianali on Mar 30, 2021 7:48:25 GMT
So. Charging still high at around 15v. Have turned on various appliances from fridge to hair dryer. He has a BM-2 which is showing about .2 to .5 amps going in at 15v with all electric stuff turned off. Turn on appliances and the amps read as I’d expect and v drop to between 13.1 and 13. 7 depending what’s being powered. So all seems fine apart from the high reading when batteries are full. Question! As there’s virtually no amps going in at 15v does that mean it’s safe to say the batteries shouldn’t be overcharging? He knows it needs looking at, but wants to boat a bit until he finds a man to sort the problem out. 15v with sealed calcium rich batteries is pretty marginal. If you’d said 14.8, maybe OK. 15 might cause a bit of gassing. 1/2 an amp obviously isnt a lot but that will nearly all be going to convert the limited supply of water in the electrolyte, to hydrogen and oxygen. I wouldn’t recommend doing that for long periods, but a few hours will be OK. If he just turns on some loads all the time he is cruising, that might drop the voltage by a few 10ths and take it below gassing voltage. I am going to cast my eyes over it for him today. As you know, I’m not the best at electrical work. However I know enough to pop a meter onto b and d +s and il check the wiring and grounds for good contact. I can’t do anymore so after that he said he will ring around for a proper sparky. This May take some time as I know boat people are jammed solid with work right now. |
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Post by ianali on Mar 30, 2021 11:31:51 GMT
So. Charging still high at around 15v. Have turned on various appliances from fridge to hair dryer. He has a BM-2 which is showing about .2 to .5 amps going in at 15v with all electric stuff turned off. Turn on appliances and the amps read as I’d expect and v drop to between 13.1 and 13. 7 depending what’s being powered. So all seems fine apart from the high reading when batteries are full. Question! As there’s virtually no amps going in at 15v does that mean it’s safe to say the batteries shouldn’t be overcharging? He knows it needs looking at, but wants to boat a bit until he finds a man to sort the problem out. 15v with sealed calcium rich batteries is pretty marginal. If you’d said 14.8, maybe OK. 15 might cause a bit of gassing. 1/2 an amp obviously isnt a lot but that will nearly all be going to convert the limited supply of water in the electrolyte, to hydrogen and oxygen. I wouldn’t recommend doing that for long periods, but a few hours will be OK. If he just turns on some loads all the time he is cruising, that might drop the voltage by a few 10ths and take it below gassing voltage. So I’ve had a look. Taken readings across b &d positives. Virtually reads nil, or near as damn it. This is with engine running at various rpm. It reads battery voltage with engine turned off. Back of alternator has D+. B+ both connected as expected. W terminal not used. Then it gets interesting, a green wire from alternator that goes no where? Hasn’t come away, it’s simply blanked off. And...there is no ground wire at all. The owner remembers that when it was fitted around two years ago, the sparky said no ground required as it would be ground through the alternator clamps. So thoughts please? |
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Post by Isambard Kingdom Brunel on Mar 30, 2021 11:56:04 GMT
Is there an Adverc or Sterling alternator controller hiding somewhere?The green wire could have been for that.
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Post by ianali on Mar 30, 2021 12:03:16 GMT
Is there an Adverc or Sterling alternator controller hiding somewhere?The green wire could have been for that. Thanks for suggestion but no. The green is properly blanked off, it’s never been connected. All’s been fine for year and a bit, only thing that’s been different is being on shore charge for months. But as I said, battery charger and or solar is all floating at mid 13 v as should be. I am wondering about the ground through clamp idea. I get that it should work but is a lot of aluminium that may have oxidised and lost its path ? |
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Post by Telemachus on Mar 30, 2021 13:03:15 GMT
15v with sealed calcium rich batteries is pretty marginal. If you’d said 14.8, maybe OK. 15 might cause a bit of gassing. 1/2 an amp obviously isnt a lot but that will nearly all be going to convert the limited supply of water in the electrolyte, to hydrogen and oxygen. I wouldn’t recommend doing that for long periods, but a few hours will be OK. If he just turns on some loads all the time he is cruising, that might drop the voltage by a few 10ths and take it below gassing voltage. So I’ve had a look. Taken readings across b &d positives. Virtually reads nil, or near as damn it. This is with engine running at various rpm. It reads battery voltage with engine turned off. Back of alternator has D+. B+ both connected as expected. W terminal not used. Then it gets interesting, a green wire from alternator that goes no where? Hasn’t come away, it’s simply blanked off. And...there is no ground wire at all. The owner remembers that when it was fitted around two years ago, the sparky said no ground required as it would be ground through the alternator clamps. So thoughts please? It is normal for the alternator casing and mounting brackets to act as the negative connections. You can get marine alternators with isolated negatives (requiring a separate negative connection) but these are uncommon on canal boats. Where on the alternator is the green wire connected? Although as you say, this has probably never been used. Did you confirm that the voltage directly across the batteries with that engine running, was 15 volts? Because of course a faulty measuring device is one possibility. If so I think we must conclude that the alternator regulator is faulty. |
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