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stuartw240
stuartw240

Posted: Mon Aug 31, 2015 5:15pm

Post Subject: Battery/Alternator

I am hoping for some advice! I know you will tell me that I need to provide some voltage figures etc but I thought I would pose the question and see what you thought.... We have just purchased our narrowboat Tinkerbell and been out on her a few times. I noticed first that the 3 leisure batteries were not holding a good charge for very long. After a good all day cruise they seem reasonable but then about 24 hours later the Eberspatcher heating gives a fault of insufficient battery voltage. It does seem to work OK when the engine is running though. On recent trips the front headlamp (in Braunston tunnel) dims and brightens as do the interior LED lights. Sometimes changing the engine revs makes them go brighter, but sometimes not. The fridge (12v) doesn't seem to last long before the compressor stops cutting in but the interior light works OK. (Fridge and freezer compartment seem to work fine when engine is running) Initially I assumed one or more of the leisure batteries needs replacing (I am assuming a voltage test will give me an indication) But do you think I also have a problem with the alternator - perhaps a voltage regulator? You thoughts would be welcome! Thank You!

Tony-B
Tony-B

Posted: Mon Aug 31, 2015 6:21pm

Post Subject: Battery/Alternator

You are correct, I need voltage figures but I think that you need to check the alternator drive belt is correctly tensioned. If it is slack that could cause the lamps brightening on their own. 12V compressor fridges have a safety cut-out, a bit like the Eberspacher, that shuts them down if the voltage under starting load drips below about 11.5 volts so you have two units telling you that you have flat batteries. To be sure of what is going on I will need a battery voltage reading just before you start up in the morning and again about half an hour after you shut down at the end of the day's cruise. I will also require the charging amps at first start up and just before you shut down at the end of the day and the alternator's rated output. However the fact the heater and fridge are OK for 24 hours suggests that the alternator is probably OK. As is typical when buying a second hand boat I suspect that your batteries are badly sulphated so they only have a fraction of their original capacity. One or more may also have faulty cells in them. If they do the faulty cells would normally gas more than the rest when charging and may be far drier than the good cells. If the ends of the batteries are bowed outwards it is a fair indication of bad sulphation. Without hydrometer readings for each cell plus the voltage reading I can not be certain but as a guess I think that a new set of batteries have a better than 75% chance of solving the problem. I would urge you to undertake a power audit and charging calculations (sample in the maintenance notes on www.tb-training.co.uk). I suspect just 3 x 110 Ah batteries running an electric fridge and Eberspacher for in excess of 24 hours without recharging is a bit optimistic.

stuartw240
stuartw240

Posted: Mon Aug 31, 2015 7:26pm

Post Subject: Battery/Alternator

Tony, many thanks for that, I will begin collecting information. Thanks!

stuartw240
stuartw240

Posted: Wed Sep 09, 2015 3:04pm

Post Subject: Battery/Alternator

Tony, I have some more information for you. Although not all of the figures that you asked for, the new information may help, I think! I have measured the voltage with both a digital electrical tester and also with a cheap digital voltmeter which you can plug into a ‘ cigarette lighter’ socket which I have near the electric panel. I had ‘tested’ the cigarette lighter voltmeter in my van for a few days to see that it was telling the truth, and it returned the figures I was expecting. (steady 14.5 volts whilst the engine is running and 13.3 v when switched off dropping to 12.2v or slightly below overnight – but the read out was steady. After the below testing on the boat, I returned the meter to the van and again it shows a steady reading as above.) We cruised the boat for about 4 hours on Saturday and I returned to her today. (Wednesday). The voltage on Saturday after switching off the engine was around 13.2v The voltage reading across the leisure batteries today before start-up was 11.4v I did try the batteries under load with the headlamp on and it went down to 8.5v and continued dropping to around 7.8v within 15 seconds or so. The batteries all seem topped up with water/ fluid and all connections are tight and free of corrosion. (As it happens there are 2 x 110AH and one 95AH batteries in addition to the 110AH starter battery. There seems to be a little bulging of the end walls of the battery but only very slight. The interesting bit seems to be when I start the engine. The digital voltmeter begins to show voltages ranging from 12.8v through 14.9v and occasionally 15.1v flicking through the voltages second by second. The meter seemed to get to the stage it couldn’t take anymore and the readout disappeared for a while. I tried switching on a load – the headlamp again. This seems to allow the meter a little respite as the readout returns but is still flicking through voltages between 11.8 through 14.8 several times per second. I only ran the engine for 2 minutes or so. When I stopped it the volts steadied and read 13.2v. I tried this again, - a steady voltage whilst engine off, then widely fluctuating voltage with engine running, then steady again when the engine is stopped. I checked the alternators. (sorry I don’t have exact sizes as yet) There are two. The smaller one on the port side has a small (thin) drive belt and was slightly loose but didn’t seem to be slipping. The larger alternator on the starboard side has a wide ribbed belt which is tight enough. Both alternators are adjusted close to their maximum adjustment for tension, so I will be replacing both belts quite soon. I certainly didn’t get the impression either one is slipping. No squealing and visually didn’t seem to slip. The only other thing to say is that I have a bow thruster battery in the bow, which seems to be charged by cables (quite large) coming from the stern. This seems to work OK and has been charging the (new) battery OK. I would be interested in your thoughts at this stage. To my untrained eye – the alternator seems to be providing a wide variety of voltage charge to the batteries, would that be the regulator? I haven’t discounted that the batteries need replacing.

Tony-B
Tony-B

Posted: Wed Sep 09, 2015 3:51pm

Post Subject: Battery/Alternator

I am unclear as to which voltmeter turned itself off and registered the different voltages. All digital meters work by sampling so they only show the voltage at discrete time intervals. The alternator's regulator also pulses on and off but it should be full on all the time with an open circuit battery voltage of 11.5 volts. That value is almost dead flat - hence the fast drop to 8 volts with the small 5 amp headlamp load. I would not trust any cigarette lighter style plug in meter to be accurate or to make good and ongoing contact with the circuit. I can not discount the varying readings being caused by vibrations shaking a poor contact about but they should not have gone above about 14 volts with a battery voltage of 11.5 for over an hour. I would expect the charging voltage to be closer to 13 in those conditions. I have already said that I think the batteries are faulty but can not guarantee that is the case. I did suggest hydrometer readings for the battery cells. Without accurate ammeter readings at the start and end of at least 6 hours of charging I can not really comment further but you will need a clamp type hand held ammeter or a shunted one if fixed permanently and both those cost money that could go towards new batteries. On the basis of what you have told me I am not willing to pass comment on the regulator. On balance I still feel the batteries are probably faulty aided and abetted by excess discharge and probably insufficient charging. Once the batteries are changed and ALL charging connections are checked we may be in a position to see if further investigation of the regulator is required. However that will need me to be certain about the quality of the equipment being used and the techniques employed. Any bulge in the end of a battery shows a fair degree of sulphation and therefore loss of capacity.

stuartw240
stuartw240

Posted: Wed Sep 09, 2015 9:06pm

Post Subject: Battery/Alternator

OK, Many thanks for that Tony. S

stuartw240
stuartw240

Posted: Fri Sep 25, 2015 12:00pm

Post Subject: Battery/Alternator

Hi Tony, I have some more data for you. I have a good quality multi-meter and a clamp meter which I was recommended. I have tried to describe how I have obtained the readings as folows: I replaced the three leisire batteries with 3 new 110AH Lucas sealed lead acid ones. They were all charged prior to fitting. We took the boat for a 4 hour cruise on Sunday last and (after 4 days I returned to the boat and took these readings. The leisure batteries read 12.79v prior to start up. The starter battery was 12.93v On start up the leisure batteries showed charging at 14.58v although this voltage was not steady - it was changing about once per second with a deflection of +0.05v and -0.17v over the first 10 minutes. As the engine wasmed the voltage dropped to around 14.24v still changing by 0.05 and -0.15v I added a load (12v fridge and spot light) and this brought the readings down to between 14.01v and 14.13v again not a steady reading. I turned off the engine and voltage dropped initially to 13.62v after 15 minutes to 13.07v after 30 minutes to 13.04v after 1 hour to 13.01v after 4 hours to 12.95v after 24 hours to 12.9v After 24 hours I checked further readings as follows: The clam meter around the +ve cable to the alternator showed 13.6A at idle with no load. 14A at 1500rpm with no load. 17.8A at idle with load (fridge and spot lamp). 19.5A at 1500rpm with load. I voltage drop tested the +ve and -ve cables. The -ve cable gave a reading of 0.2v The complete +ve cable gave a reading of 1.9v I tested the two 'halves of the +ve cable - the section from battery to the connection point attached to the engine was 0.2v and the section between the connection and the generator 1.9v All connections are tight. It seems to me that the voltage drop on the cable to the alternator is too high, so my next task would be to remove it and examine it. Clean (and replace if necessary) and re-fit ensuring a good connection. The current reading seems low also - do you think this can be explained by the voltage drop anomaly? Your thoughts would be welcome. Thanks again. Stuart

stuartw240
stuartw240

Posted: Fri Sep 25, 2015 12:05pm

Post Subject: Battery/Alternator

Perhaps I should add that the current readings were the highest obtained, the reading was fluctuating reasonably quickly. Also my leisure alternator seems to be the Beta original equipment. the Beta have it recorded as a 175Amp alternator but the boat manual suggests it is a 100A. i think Beta began fitting the larger alternators around the year of manufacture 2009 and so perhaps it was initially thought to be a 100A but when supplied may have been a 175A. there are no markings on it that I can see but there may be some underneath which I could check if and when I remove it! Thanks again.

Tony-B
Tony-B

Posted: Fri Sep 25, 2015 5:29pm

Post Subject: Battery/Alternator

The batteries would seem to be fully charged so one would only expect a low charging current. You are getting more than 10% of battery capacity so I doubt anything is wrong. As I explained digital meters work by sampling at discrete intervals and I would never expect an absolutely stable reading. From what you say the only thing that seems definitely wrong is the volt drop on the lead you found.

stuartw240
stuartw240

Posted: Fri Sep 25, 2015 7:21pm

Post Subject: Battery/Alternator

Thanks Tony, i will investigate that to try to improve the voltage drop. many thanks for your help and advice. Stuart

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