Alternator not charging quickly enough

[Karen Lea Rainey]

Hi All,

 I have a problem with the alternator, I think,

To start, I checked voltage at the batteries , it was 12.63 v before starting. (All 3 batteries are pretty new and wired in series).

 

Started the Isuzu 1.2 engine after 10 seconds heating, it started straight away no problem.

The charging light comes on and stays on, it is quite bright and constant.

Immediately check the voltage at the batteries again, it's now 12.52 v,

Wait a couple of minutes, check voltage again,   it's now 12.56 v

After 10 minutes, check the voltage again,  it's  now 12.58 v

 

After 30 mins the voltage has now got to  12.68 volts.

The charging light is still brightly lit, turned the key to off for a couple of minutes which extinguishers the charging light and checked in another couple of minutes,   we've now got  12.70 v,

 

Surely the alternator isn't doing it's job or am I wrong ?

 

The alternator belt is tight with only a tiny bit of slack in it, the smaller cables to the  alternator are firmly attached as are the other cables.

 

I,m pretty sure the alternator has given up, the boat is new to me and has spent the last 8 years moored up in a marina being slowly refitted out.

I have taken some pictures of the alternator but it is difficult to get a clear picture, from what I can make out it's  an Hitachi alternator , but I cannot see any model numbers etc, can anyone tell which one it is and point me in the direction of a replacement please.

[rusty69]

Does the charge light remain on when you rev up the engine?

[Mike Hurley]

Is the engine idling or have you tried giving a burst of revs to excite the alternator?

[Karen Lea Rainey]

Yes the engine was idling, but the tickover is set quite high at the moment, that is something else I need to address in the coming weeks,

I forgot about revving the engine, so have I got it wrong, what should the voltage be around when I,m revving up a bit ?

 

[MtB]

Can you confirm the engine is running at all when you get these 12.5-something voltages? 

 

If yes, what is the charge current at 12.5-something Volts?

 

If you don't have an ammeter or clamp meter already, there is never gonna be a more appropriate time to buy one than now!

 

 

 

Edited December 5, 2018 by Mike the Boilerman
Spelling!

[Karen Lea Rainey]

The engine is running throughout the voltage recordings, the exciter charging light remained on throughout all the readings, thanks

[MtB]

Just now, Karen Lea Rainey said:

The engine is running throughout the voltage recordings, the exciter charging light remained on throughout all the readings, thanks

 

So what is the charging current?

[WotEver]

14 minutes ago, Karen Lea Rainey said:

All 3 batteries are pretty new and wired in series

Unless you have a 36V boat I would suggest that they’re wired in parallel. 

4 minutes ago, Karen Lea Rainey said:

The engine is running throughout the voltage recordings, the exciter charging light remained on throughout all the readings, thanks

Rev it. It’s quite common for alternators to not excite at tickover. 

[Karen Lea Rainey]

How do you check the charging current ? I've  only ever checked the voltage readings on the battery terminals with my   multi tester.

Rev it, I will have to do next time I'm  at the boat and check to see if the light goes out and see if the voltage goes up through excitement !!!

[MtB]

Just now, Karen Lea Rainey said:

How do you check the charging current ?

 

By reading what it says on your ammeter, or by using a clamp meter to measure the charge current in the big wire from the alternator. 

 

I suspect you have neither given your question! Buy one or the other for future use even if not this time around, I suggest.

 

And as previous posters, rev the engine. The light may well go out and remain out even when returning to tickover. 

[WotEver]

2 minutes ago, Karen Lea Rainey said:

How do you check the charging current ?

With one of these:

UNI-T UT210E True RMS AC/DC Current Mini Clamp Meters w/ Capacitance Tester

 

https://www.amazon.co.uk/dp/B00O1Q2HOQ/ref=cm_sw_r_cp_api_i_5I.bCbWCYT2AD

 

That’s assuming that the boat isn’t already equipped with an ammeter for battery monitoring. That’s a good (almost essential) monitoring device for you to fit ASAP. 

[Karen Lea Rainey]

Yes then I have an ammeter, with the pos and neg points to put on the battery terminals, to check voltage I turn it on to 20 volts for a more accurate readout.  Sounds like the thing I forgot to do was rev it, instead I expected to see a higher reading when the engine is running.

[Alan de Enfield]

3 minutes ago, Karen Lea Rainey said:

Yes then I have an ammeter, with the pos and neg points to put on the battery terminals

That's how you test voltage, you test current (amps) by pitting the test meter 'in-line', but the clamp-meter is the easiest method.

 

Make sure you buy a DC Current meter - some are DC Voltage but AC CURRENT.

[MtB]

8 minutes ago, Karen Lea Rainey said:

Yes then I have an ammeter, with the pos and neg points to put on the battery terminals, to check voltage I turn it on to 20 volts for a more accurate readout.  Sounds like the thing I forgot to do was rev it, instead I expected to see a higher reading when the engine is running.

 

I think you are still lacking an understanding of the basics, in particular the difference between voltage and current. 

 

Voltage is the difference in electrical 'pressure' between two points, e.g. a pair of battery terminals or a pair of wires. Current (measured in Amps) is the 'flow rate' of the electricity along a wire or other conductor, so an ammeter needs to be inserted into the wire to measure. Or a 'clamp meter' can approximately measure it by putting the jaws of the clamp meter around the wire (and it then determines the current by magic). 

 

 

Edited December 5, 2018 by Mike the Boilerman
Improve clarity

[system 4-50]

44 minutes ago, Mike the Boilerman said:

Current (measured in Amps) is the 'flow rate'

I've deleted my comment 'cos I was wrong!    I like this edit thing...

Edited December 5, 2018 by system 4-50

[MtB]

2 minutes ago, system 4-50 said:

rate implies time???

 

Yes. 

 

1 Amp = 1 Coulomb per second

[WotEver]

1 hour ago, Mike the Boilerman said:

a 'clamp meter' can approximately measure it by putting the jaws of the clamp meter around the wire (and it then determines the current by magic). 

I’d normally omit the ‘approximately’ from the above description as clamp meters are pretty accurate if used as per the instructions. Certainly close enough for boat use. 

[MtB]

1 minute ago, WotEver said:

I’d normally omit the ‘approximately’ from the above description as clamp meters are pretty accurate if used as per the instructions. Certainly close enough for boat use. 

 

Not in my experience!

 

 

 

Although I grant you, using them in strict accordance with the instructions simply doesn't happen in real life measuring situations.

 

[Tony Brooks]

2 hours ago, Karen Lea Rainey said:

Yes then I have an ammeter, with the pos and neg points to put on the battery terminals, to check voltage I turn it on to 20 volts for a more accurate readout.  Sounds like the thing I forgot to do was rev it, instead I expected to see a higher reading when the engine is running.

If the meter you describe has an Amps DC range plus a 10 or 20 amp DC hole to put the red lead into on no account try to use it.

 

First it will not read enough amps for starting or charging system use and secondly, perhaps of more importance, at your present state of knowledge you are very likely to cause it to omit magic smoke and it may nit be reliable after that - even for volts.

 

If you can get a clamp type DC  ammeter like the one Wotever linked to.

 

Rev the engine and give us the voltage readings you get please. take them at 1200 to 1500 RPM>

[Markinaboat]

After further research, it seems the UNI-T clamp meter is not that accurate although not sure if this applies to higher amps? Googling finds the Fluke 325 but around £150! Has anyone got anything that maybe sits between?

 

https://www.edwardes.co.uk/en/products/fluke-325-400a-600v-ac-dc-true-rms-digital-clamp-meter?utm_medium=google_shopping&utm_source=google&utm_campaign=google_shopping&gclid=EAIaIQobChMI9e_Jj7GJ3wIVBIXVCh2Y_Ax6EAQYAiABEgIGsvD_BwE

Edited December 5, 2018 by Markinaboat
add url

[Eeyore]

3 hours ago, Karen Lea Rainey said:

The engine is running throughout the voltage recordings, the exciter charging light remained on throughout all the readings, thanks

The term “exciter charging light” may be misleading for a Hitachi alternator, which commonly have separate connections for excitation and warning light. A picture showing the wiring would be useful.

[bizzard]

It might be a fake, a Lotachi instead of a Hitachi. If the warning light has always worked properly up until now its probably on the correct terminal.

[Eeyore]

Just now, bizzard said:

It might be a fake, a Lotachi instead of a Hitachi. If the warning light has always worked properly up until now its probably on the correct terminal.

I was thinking more broken/loose wiring, but accept that it could simply be a failed alternator.

[ditchcrawler]

24 minutes ago, Markinaboat said:

After further research, it seems the UNI-T clamp meter is not that accurate although not sure if this applies to higher amps? Googling finds the Fluke 325 but around £150! Has anyone got anything that maybe sits between?

 

https://www.edwardes.co.uk/en/products/fluke-325-400a-600v-ac-dc-true-rms-digital-clamp-meter?utm_medium=google_shopping&utm_source=google&utm_campaign=google_shopping&gclid=EAIaIQobChMI9e_Jj7GJ3wIVBIXVCh2Y_Ax6EAQYAiABEgIGsvD_BwE

I have 2 meters in the £30-40 range, the one at home seams is much better than the one on the boat, I am taking it with me and comparing them.

 

[WotEver]

31 minutes ago, Markinaboat said:

After further research, it seems the UNI-T clamp meter is not that accurate...

Compared to a Fluke? No, of course not. As a guide to what current is flowing where within a boat? It’s plenty good enough. 

 

A review at random (first one I found):

https://youtu.be/r7QjTEE2Sn0