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Post by Deleted on Feb 21, 2019 12:39:15 GMT
For the last 15 months I’ve managed to get away with using a single lead acid type 70ah starter battery as a leisure battery with no problems. I am always off line so rely totally on alternator charging from the engine on average 3 hours per day (depending on cruising).
This has worked out by far the cheapest solution for off line boating as 4 ‘leisure’ batteries rarely lasted more than 2 years at £500 - £600!
This morning I noticed that the charging voltage at the alternator was not the usual 14.4-14.6v and wouldn’t go above 13.0v even after a couple of hours of charging (no domestic loads connected).
When I disconnected this battery (normal engine starter battery still connected) the charge voltage started to go back up towards the normal 14v +.
I suspect that the battery I have been using for leisure purposes is the culprit rather than the alternator (which was new 5 years ago) so I intend to replace that first. However I was wondering whether this is a normal symptom of battery failure? (i.e pulls down charging voltage even after 2 hours charging)
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Post by JohnV on Feb 21, 2019 12:47:51 GMT
For the last 15 months I’ve managed to get away with using a single lead acid type 70ah starter battery as a leisure battery with no problems. I am always off line so rely totally on alternator charging from the engine on average 3 hours per day (depending on cruising). This has worked out by far the cheapest solution for off line boating as 4 ‘leisure’ batteries rarely lasted more than 2 years at £500 - £600! This morning I noticed that the charging voltage at the alternator was not the usual 14.4-14.6v and wouldn’t go above 13.0v even after a couple of hours of charging (no domestic loads connected). When I disconnected this battery (normal engine starter battery still connected) the charge voltage started to go back up towards the normal 14v +. I suspect that the battery I have been using for leisure purposes is the culprit rather than the alternator (which was new 5 years ago) so I intend to replace that first. However I was wondering whether this is a normal symptom of battery failure? (i.e pulls down charging voltage even after 2 hours charging) sounds like the leisure battery has a dud cell (short circuit) there are various things people do to try and extend the life (washing out etc) but basically it's finished. If you only got 15 months see what your guarantee date was ....... if that is going to be the average life in your hands get one with at least a 2 year guarantee eta replace as soon as poss ..... won't do the charging system any good and will cause the battery to overheat
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Post by Deleted on Feb 21, 2019 13:48:01 GMT
For the last 15 months I’ve managed to get away with using a single lead acid type 70ah starter battery as a leisure battery with no problems. I am always off line so rely totally on alternator charging from the engine on average 3 hours per day (depending on cruising). This has worked out by far the cheapest solution for off line boating as 4 ‘leisure’ batteries rarely lasted more than 2 years at £500 - £600! This morning I noticed that the charging voltage at the alternator was not the usual 14.4-14.6v and wouldn’t go above 13.0v even after a couple of hours of charging (no domestic loads connected). When I disconnected this battery (normal engine starter battery still connected) the charge voltage started to go back up towards the normal 14v +. I suspect that the battery I have been using for leisure purposes is the culprit rather than the alternator (which was new 5 years ago) so I intend to replace that first. However I was wondering whether this is a normal symptom of battery failure? (i.e pulls down charging voltage even after 2 hours charging) sounds like the leisure battery has a dud cell (short circuit) there are various things people do to try and extend the life (washing out etc) but basically it's finished. If you only got 15 months see what your guarantee date was ....... if that is going to be the average life in your hands get one with at least a 2 year guarantee eta replace as soon as poss ..... won't do the charging system any good and will cause the battery to overheat Yes. thanks John, that all makes sense. I will replace it ASAP. It did come with a 5 year guarantee but I haven’t got the cheek to try that on. and anyway, they will probably say I haven’t used it according to their spec. I’m sure it would have lasted 5 years if it had been used as a car starter battery!
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Post by Telemachus on Feb 21, 2019 14:18:46 GMT
Yes it could well be the leisure battery. If so I would expect it to get warm and fizz a lot when being charged, and shortly after charging for its voltage to fall lower than usual.
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Post by Deleted on Feb 21, 2019 14:30:28 GMT
Yes it could well be the leisure battery. If so I would expect it to get warm and fizz a lot when being charged, and shortly after charging for its voltage to fall lower than usual. Yes, what’s interesting about it is that it’s dragging the charging voltage right down when connected as if it was nearly flat, but it isn’t taking a lot of amps from the alternator! Normally if it needed a lot of charging I’d see 30 + amps plus while re- charging. It is still possible my alternator is giving out as well. I’l see what happens with the new battery first.
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Post by Telemachus on Feb 21, 2019 14:35:39 GMT
Ah well if you are seeing low voltage but not much current, it isn’t the battery. Sounds like the alternator is faulty, or maybe a bad connection somewhere between alternator and battery. When you disconnect the leisure battery the starter battery will already be virtually fully charged which is why the voltage rises despite alternator or connection woes. Check for voltage drop somewhere. Battery isolators are a favourite.
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Post by Deleted on Feb 21, 2019 14:43:44 GMT
I had a shorted cell in a Rolls traction battery (confirmed by a refractometer which showed the SG as about 1.1 with other cells between 1.24 and 1.26).
Of course most modern batteries you can't get to the electrolyte to test it but the notable thing about the failure is that the result was the battery attempted to draw much more current while charging than usual but failed to charge. And yes it got hot.
I claimed on warranty by sending them details of my findings with the refractometer and I made up a suitable charging regime rather than admit I was hitting the 430ah battery with a 130a charger.
I got replacement batteries (2 x 6v blocks) under warranty. They have lasted 7 years since then but to be fair they are now in a relaxed environment on mains electric via a truecharge 20i "the rolls royce of battery chargers" whereas when they failed it was a diesel generator running a 130a Heart interface freedom charger which is a bit of a beast and does indeed crank out 130a initially on low batteries.
So maybe I broke them or maybe they were faulty blocks.
If the battery is not drawing excess current then it seems possible its something else.
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Post by Gone on Feb 21, 2019 14:47:28 GMT
Ah well if you are seeing low voltage but not much current, it isn’t the battery. Sounds like the alternator is faulty, or maybe a bad connection somewhere between alternator and battery. When you disconnect the leisure battery the starter battery will already be virtually fully charged which is why the voltage rises despite alternator or connection woes. Check for voltage drop somewhere. Battery isolators are a favourite. Check the voltage on the back of the alternator if it’s ok and low at the battery, then as Nick says you have a bad connection.
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Post by Deleted on Feb 21, 2019 15:13:06 GMT
Ah well if you are seeing low voltage but not much current, it isn’t the battery. Sounds like the alternator is faulty, or maybe a bad connection somewhere between alternator and battery. When you disconnect the leisure battery the starter battery will already be virtually fully charged which is why the voltage rises despite alternator or connection woes. Check for voltage drop somewhere. Battery isolators are a favourite. Check the voltage on the back of the alternator if it’s ok and low at the battery, then as Nick says you have a bad connection. It’s low at the back of the alternator terminals whist the suspect ‘leisure’ battery is connected and engine running. It returns to the normal higher voltage when only the ‘good’ starter battery is connected. I did wonder about the sens wire (which goes to the bulb). but that all seems Ok. I’ll bypass the isolator switch temporarily to see if it is that. I had one go permanently closed circuit once, they do seem to be unreliable!
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Post by Deleted on Feb 21, 2019 15:14:01 GMT
I sometimes think the best emergency battery isolator is a pair of wire cutters. The switches themselves often seem to cause issues. I would not want to rely on one to definitely cut the power in the event of problems as it might weld itself closed and short out anyway.
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Post by JohnV on Feb 21, 2019 15:54:36 GMT
Yes it could well be the leisure battery. If so I would expect it to get warm and fizz a lot when being charged, and shortly after charging for its voltage to fall lower than usual. Yes, what’s interesting about it is that it’s dragging the charging voltage right down when connected as if it was nearly flat, but it isn’t taking a lot of amps from the alternator! Normally if it needed a lot of charging I’d see 30 + amps plus while re- charging. It is still possible my alternator is giving out as well. I’l see what happens with the new battery first. Just surfaced from my galley rebuild to see this post ..... as others have said this changes things
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Post by Gone on Feb 21, 2019 19:48:19 GMT
Check the voltage on the back of the alternator if it’s ok and low at the battery, then as Nick says you have a bad connection. It’s low at the back of the alternator terminals whist the suspect ‘leisure’ battery is connected and engine running. It returns to the normal higher voltage when only the ‘good’ starter battery is connected. I did wonder about the sens wire (which goes to the bulb). but that all seems Ok. I’ll bypass the isolator switch temporarily to see if it is that. I had one go permanently closed circuit once, they do seem to be unreliable! If the alternator output is low it’s either working correctly and dropping the voltage to limit the current (to a high level) or it is unable to output the rated current (power) because there is something wrong with it. How are you measuring the alternator output current? Or to be blunt are you sure the current is low? Just a thought, if you are running something like a big inverter then most of the current from the alternator will be going to the inverter and not the battery, so you need to be sure there isn’t a large load turned on. Best if you could measure the current at the alternator with a clamp meter.
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Post by Deleted on Feb 21, 2019 19:53:59 GMT
DC clamps are pretty cool toys.
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Post by Deleted on Feb 21, 2019 19:58:15 GMT
It’s low at the back of the alternator terminals whist the suspect ‘leisure’ battery is connected and engine running. It returns to the normal higher voltage when only the ‘good’ starter battery is connected. I did wonder about the sens wire (which goes to the bulb). but that all seems Ok. I’ll bypass the isolator switch temporarily to see if it is that. I had one go permanently closed circuit once, they do seem to be unreliable! If the alternator output is low it’s either working correctly and dropping the voltage to limit the current (to a high level) or it is unable to output the rated current (power) because there is something wrong with it. How are you measuring the alternator output current? Or to be blunt are you sure the current is low? Just a thought, if you are running something like a big inverter then most of the current from the alternator will be going to the inverter and not the battery, so you need to be sure there isn’t a large load turned on. Best if you could measure the current at the alternator with a clamp meter. Yes, good advice. I have no inverter, the whole circuit is very simple (like me). I used the hammer technique earlier. I used it on the isolator switch. That increased the charging voltage a bit, much to my surprise! (probably dirty contacts). Then I hit the alternator, that made things better. Probably due to shocking a stuck brush into position. I’m still going for a new battery and possibly a referbushed alternator though!
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Post by Deleted on Feb 21, 2019 19:59:52 GMT
DC clamps are pretty cool toys. I totally agre MM, the best investment I ever made on this boat...next to the missus..
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