Alternator suddently not putting out voltage... help!

[jetzi]

Thank you. I ordered one of these.

 

I like the idea of permanent sensors giving me an overview of my batteries and charging system but I think this is going to take a bit of thought and there are many options. There must be some products that have multiple ammeters, voltmeters and sensors that you can place all over your electrical system and they can monitor an accurate state of your batteries and charging systems at all times.

[Nut]

41 minutes ago, Bod said:

Don't get a cheap one, many don't measure DC current via the clamp.

This one is about the best available, for boating needs.

 

Bod

this was a best seller at maplin I always had to phone head office to get more stock allocated

[alan_fincher]

19 minutes ago, ivan&alice said:

There must be some products that have multiple ammeters, voltmeters and sensors that you can place all over your electrical system and they can monitor an accurate state of your batteries and charging systems at all times.

 

Accurate current measurement requires that something is placed in line in the circuit being measured - usually a "shunt" across which a small voltage can be measured, (although having an actual ammeter actually in line is a cruder version sometimes still used).
 

By its very nature, however efficiently this achieved, it will introduce at least a small voltage drop in the circuit being measured - exactly what you don't want in an efficient charging system.

 

Therefore multiple shunts would be something you would wish to avoid.

 

The clamp meter approach to measuring current on an ad-hoc basis avoids these unwanted voltage drop points being introduced, but the readings they give are much less accurate - though usually more than accurate enough for the kind of diagnostics one is doing.

There is no reason on the other hand why you can't measure voltage at any point without introducing losses.  It is not totally unusual to have a single voltmeter with a multi-position switch to achieve this.

 

[Guest]

2 hours ago, ditchcrawler said:

Or fit something like this https://www.aliexpress.com/item/DC300V-100A-200A-400A-Hall-Effect-Coulometer-Digital-Voltmeter-Ammeter-Sensor/32918954982.html I think you will find them on ebay if you search

 

That looks good. Damn I need one now

[1st ade]

8 minutes ago, catweasel said:

Damn I need one now

No, you want one now. You've managed without, you don't need

[Guest]

15 minutes ago, 1st ade said:

No, you want one now. You've managed without, you don't need

Sorry I have already convinced myself that I can't live without one

[Murflynn]

I was sold on the Uni-T when the AA man helped me out with Home Start and used one to check my charging system.  So good I bought 2 - one for the boat, one for the car.

[Tony Brooks]

10 hours ago, ivan&alice said:

Could this occur from sulfation?

 Indirectly. Lead sulphate has a greater volume than lead oxides so the plates swell and push on the separators and case so swollen plates make it more likely that a separator could be damaged causing a short circuit. If the ends of the battery have not  bowed then sulphation can get a lot worse.

[ditchcrawler]

5 hours ago, Murflynn said:

I was sold on the Uni-T when the AA man helped me out with Home Start and used one to check my charging system.  So good I bought 2 - one for the boat, one for the car.

I have one on the boat and one at home

[jetzi]

Sorry to revive this old topic but I finally got around to putting that Uni-T clamp ammeter on my alternator out cable. The belt had worn through and so since my battery was over-flat (showing 11.9V) and I was mucking about with the alternator anyway, I thought it was a good time.

 

I started the engine (at normal idle revs - I don't have a rev counter) and quickly turned on everything I could in the boat. The voltmeter on my battery showed 13.9V. I measured the output cable which showed up as 47.3A and climbed to about 49.3A.

 

I measured what the boat was drawing at 6.3A.

 

Does this mean I only have a 50A alternator? Or would you expect a 70A to put out around 50A under these conditions?

[ditchcrawler]

2 minutes ago, ivan&alice said:

Sorry to revive this old topic but I finally got around to putting that Uni-T clamp ammeter on my alternator out cable. The belt had worn through and so since my battery was over-flat (showing 11.9V) and I was mucking about with the alternator anyway, I thought it was a good time.

 

I started the engine (at normal idle revs - I don't have a rev counter) and quickly turned on everything I could in the boat. The voltmeter on my battery showed 13.9V. I measured the output cable which showed up as 47.3A and climbed to about 49.3A.

 

I measured what the boat was drawing at 6.3A.

 

Does this mean I only have a 50A alternator? Or would you expect a 70A to put out around 50A under these conditions?

As the chap said when he repaired my old alternator and saw 100 Amps stamped on the edge "your be lucky" he was a bit old school with many years experience and I trust him. a 100 amps would be nearly 2.kKW on a single V belt

[jetzi]

1 minute ago, ditchcrawler said:

As the chap said when he repaired my old alternator and saw 100 Amps stamped on the edge "your be lucky" he was a bit old school with many years experience and I trust him. a 100 amps would be nearly 2.kKW on a single V belt

I don't know what my alternator is rated at, which is why I am so keen to see what it is putting out.

 

I suppose if it is putting out 50A that is my answer!

I found a few more things to load it up with and got the boat drawing 10A. I measured again and it says only 38A - I'm supposing because it has heated up a bit.

What number should I work on for my alternator output?

[Chewbacka]

42 minutes ago, ivan&alice said:

I don't know what my alternator is rated at, which is why I am so keen to see what it is putting out.

 

I suppose if it is putting out 50A that is my answer!

I found a few more things to load it up with and got the boat drawing 10A. I measured again and it says only 38A - I'm supposing because it has heated up a bit.

What number should I work on for my alternator output?

When it had dropped to 38A had the battery voltage risen above 13.9V?  If so it may simply be that the batteries wouldn’t take any more.  

[jetzi]

1 minute ago, Chewbacka said:

When it had dropped to 38A had the battery voltage risen above 13.9V?  If so it may simply be that the batteries wouldn’t take any more.  

No, this was a matter of minutes after the initial reading. The voltage had risen to 14.1V which is about normal while charging. I only have 1x 110Ah battery that has seen more than its fair share of abuse over the year I've owned it. I'm just aiming for it to last the winter and I'll replace it with a nice new bank of something...

[Chewbacka]

1 minute ago, ivan&alice said:

No, this was a matter of minutes after the initial reading. The voltage had risen to 14.1V which is about normal while charging. I only have 1x 110Ah battery that has seen more than its fair share of abuse over the year I've owned it. I'm just aiming for it to last the winter and I'll replace it with a nice new bank of something...

So the voltage had risen, and it’s only a single knackered battery, so it would not surprise me that the battery was now limiting the charge current. 

[ditchcrawler]

I wonder what sort of voltage differential would be required to get 70 amps into a single 12 volt battery

[jetzi]

41 minutes ago, Chewbacka said:

So the voltage had risen, and it’s only a single knackered battery, so it would not surprise me that the battery was now limiting the charge current. 

Limiting, but still charging? I wouldn't call the battery knackered, it's still serving its purpose quite adequately.

 

So do you think 50A is a fair number to expect from the alternator once I have a decent bank of batteries? Or do you think I should perform some other kind of test to see what the alternator can put out? I could for example flatten the battery and try again?

 

I really just want a figure for my electrical audit calculations - before I upgrade the bank, I want to be sure I can put the power back in. I plan to get as much solar as I need to run everything from solar for at least 9 months of the year, and I want to make sure the alternator can do the rest.

[Alan de Enfield]

6 minutes ago, ivan&alice said:

I plan to get as much solar as I need to run everything from solar for at least 9 months of the year,

Good luck with that - unless you are a very, very 'light' user of electrikery.

7 months is do-able but October - March is problematic.

[WotEver]

5 minutes ago, ivan&alice said:

So do you think 50A is a fair number to expect from the alternator once I have a decent bank of batteries? Or do you think I should perform some other kind of test to see what the alternator can put out? I could for example flatten the battery and try again?

Due to the Amphour ‘rule’ the battery will only demand a current approximately equivalent to its depth of discharge. So if your abused 110Ah battery now has a capacity of 60Ah then even if it had a DoD of 80% it would only demand 48A and only for a short time. The only way to know what your alternator can output would be to turn on lots of stuff (maybe a large inverter with a kettle plugged in?) and also run the engine a lot faster than tickover. 

[jetzi]

8 minutes ago, Alan de Enfield said:

Good luck with that - unless you are a very, very 'light' user of electrikery.

7 months is do-able but October - March is problematic.

Or a heck of a lot of solar? I hear that you can get something like 10% of the rated output for a few hours a day in the dead of winter. Perhaps 9 months is optimistic.

 

We are very, very light on electrickery at the moment, just water pumps, lights and device chargers. But once we have an inverter and our washing machine plugged in it will be a different story. And the fridge running 24/7 instead of just 2 hours a day like we do at the moment. And the Eberspaecher reconnected. It might just mean laundromats for those few months.

 

12 minutes ago, WotEver said:

Due to the Amphour ‘rule’ the battery will only demand a current approximately equivalent to its depth of discharge. So if your abused 110Ah battery now has a capacity of 60Ah then even if it had a DoD of 80% it would only demand 48A and only for a short time. The only way to know what your alternator can output would be to turn on lots of stuff (maybe a large inverter with a kettle plugged in?) and also run the engine a lot faster than tickover. 

I don't have an inverter. With the headlight, fridge, all lights, two devices charging, and shower pump running I managed to draw just over 10A. I'm guessing this won't be enough load to test the alternator then.

[Alan de Enfield]

6 minutes ago, ivan&alice said:

I hear that you can get something like 10% of the rated output for a few hours a day in the dead of winter.

I reckon getting 1% of rated output (average) for 6 hours per day would be going some.

 

If we take your '10% of output', and the commonly quoted daily usage of 100Ah then you need to be able to generate that in the short winters day (say 9:00am to 3:00pm) that would be roughly 12,000+ watts (120 x 100watt) of solar panels assuming a cloudless sky, no rain, no shade etc etc.

 

Those panels would output something in the order of 1000Ah per day in Summer.

 

I think you'd get that on a house roof, no chance on a NB

 

Solar does not work sufficiently for 5-6 months of the year.

 

Yes, you can get quick 'bursts' of good output but it is not sustained.

 

This was 18th Feb from a 170 watt 'low-light' panel

[Sir Nibble]

24 minutes ago, ivan&alice said:

Or a heck of a lot of solar? I hear that you can get something like 10% of the rated output for a few hours a day in the dead of winter. Perhaps 9 months is optimistic.

 

We are very, very light on electrickery at the moment, just water pumps, lights and device chargers. But once we have an inverter and our washing machine plugged in it will be a different story. And the fridge running 24/7 instead of just 2 hours a day like we do at the moment. And the Eberspaecher reconnected. It might just mean laundromats for those few months.

 

I don't have an inverter. With the headlight, fridge, all lights, two devices charging, and shower pump running I managed to draw just over 10A. I'm guessing this won't be enough load to test the alternator then.

Alternator output. This is only relevant if your charging performance is impaired by the alternator spending a long time on the bulk (current limited) phase of charging. The best way to load it is to get on with your plans and if no problems arise, no problem. As soon as the voltage stops rising bulk charge is over. Up until then the alternator will deliver the maximum current it is able AT THE SPEED AT WHICH IT IS BEING DRIVEN. Caps for emphasis not shouty.

[jetzi]

Well this is where I got up to with my audit. I'm thinking of buying around a 1500W inverter which I will only need to run my Hotpoint WMTF722H washing machine on a cold cycle and the missus' 1200W hairdryer. I estimated the average draw on the inverter to be 1000W while in use.

 

Being fairly pessimistic with these numbers, I estimate I'll need around 3.5kWh on a high consumption day.

 

 

The solar I'm thinking of getting is 4x 315W bifacial panels https://www.bimblesolar.com/ja315w-bifacial-solar-panel which totals an absolute maximum of 1600W.

 

The longest day of the year is 16h 40min. If I approximate the output to be an average of 50% over the day, that's 16h 40min * 800W = 13.3kW.

 

The shortest day of the year is 7h 50min. If I approximate the output to be an average of 10% over the day, that's 7h 50min * 160W = 1.25kW.

 

October is around 10h of daylight. If I approxumate the output to be an average of 25% over the day, that's 10h * 400W = 4kW.

Am I being wildly optimistic with these figures? More research is needed - but this is my start point.

[MtB]

1 hour ago, ivan&alice said:

I hear that you can get something like 10% of the rated output for a few hours a day in the dead of winter.

 

A figure only ever quoted by armchair experts who don't use solar panels on a boat, I'd suggest.

 

Alan's 1% is fsr closer to the mark. On a grey winter day in Jan I might see 0.1A at midday from my 560W of solar, at 24V.  

[Alan de Enfield]

55 minutes ago, ivan&alice said:

Well this is where I got up to with my audit. I'm thinking of buying around a 1500W inverter which I will only need to run my Hotpoint WMTF722H washing machine on a cold cycle and the missus' 1200W hairdryer. I estimated the average draw on the inverter to be 1000W while in use.

 

Being fairly pessimistic with these numbers, I estimate I'll need around 3.5kWh on a high consumption day.

 

 

The solar I'm thinking of getting is 4x 315W bifacial panels https://www.bimblesolar.com/ja315w-bifacial-solar-panel which totals an absolute maximum of 1600W.

 

The longest day of the year is 16h 40min. If I approximate the output to be an average of 50% over the day, that's 16h 40min * 800W = 13.3kW.

 

The shortest day of the year is 7h 50min. If I approximate the output to be an average of 10% over the day, that's 7h 50min * 160W = 1.25kW.

 

October is around 10h of daylight. If I approxumate the output to be an average of 25% over the day, that's 10h * 400W = 4kW.

Am I being wildly optimistic with these figures? More research is needed - but this is my start point.

 

Take out the hairdryer and the washing machine and you have the 'normal' ~100Ah per day.

 

There is a 'written' rule in boating "don't generate heat via batteries" - get Alice to cut her hair or get used to it drying naturally.