Altenator or battery?

[Mouldylocks]

Hello - apologies if I am asking for an answer 100s provided! I have currently a flat (and trashed!!) starter battery. Its done, finished, we shall not see her again.... I am wondering why it has failed though, and thinking of my alternator. Before I buy a new starter battery, does anyone have any troubleshooting steps I can take to see if my alternator has packed it in as well (and is the reason to the failure!).

 

AS a sidenote, I am currently relying on a jump from my leisure rig to start my engine as I am in the middle of a cruise back to my home river(s)... Could anyone advise on how long this is an option for until I risk damaging my leisure batteries?

 

Thanks so much

[MtB]

9 minutes ago, Mouldylocks said:

Hello - apologies if I am asking for an answer 100s provided! I have currently a flat (and trashed!!) starter battery. Its done, finished, we shall not see her again.... I am wondering why it has failed though, and thinking of my alternator. Before I buy a new starter battery, does anyone have any troubleshooting steps I can take to see if my alternator has packed it in as well (and is the reason to the failure!).

 

AS a sidenote, I am currently relying on a jump from my leisure rig to start my engine as I am in the middle of a cruise back to my home river(s)... Could anyone advise on how long this is an option for until I risk damaging my leisure batteries?

 

Thanks so much

 

Welcome Goldiedocks.

 

Yes. After disconnecting your expired starter batt and insulating the terminals (or just turning OFF the isolator switch if it has a separate one of its own), start the engine and measure the voltage on the terminals of your leisure bank. If it is less than about 13.0v then the alternator is probably goosed and your domestic bank will be heading the same way as the starter batt unless you fix it pronto. If it is up above say 13.5V then the alt is prolly fine. 

 

This all assumes you have just one alt. Lots of more modern boats have two so all bets are off. Or more accurately, your leisure bank is not at risk as it has its own separate charge source. 

 

What engine do you have?

 

 

 

 

[Jen-in-Wellies]

Welcome to the forum. A couple of questions.

Do you have a multimeter?

Do you have an alternator warning light? If so, what is it doing with the engine off and with ignition off? Engine running?

[Mouldylocks]

Hello! My leisure batteries are charged from a totally separate solar setup, I have been monitoring them closely and reducing use on the days that I do a jump, they seem to be fine, holding 13/13.1v through the night and then up to 13.7 when the solar is soaking up the light that is about in the day. I haven't disconnected the expired starter yet, when I took a reading last was only boosting the goosed (love this term!) starter from around 11v to say... 12ish, but hardly v! On a car I would have expected that it would have boosted more even with a battery that has died? That was with a full tighten on the belt as well. My engine is a lister SR2 and not sure what the alternator is but can investigate more. 

1 minute ago, MtB said:

 

Welcome Goldiedocks.

 

Yes. After disconnecting your expired starter batt and insulating the terminals (or just turning OFF the isolator switch if it has a separate one of its own), start the engine and measure the voltage on the terminals of your leisure bank. If it is less than about 13.0v then the alternator is probably goosed and your domestic bank will be heading the same way as the starter batt unless you fix it pronto. If it is up above say 13.5V then the alt is prolly fine. 

 

This all assumes you have just one alt. Lots of more modern boats have two so all bets are off. Or more accurately, your leisure bank is not at risk as it has its own separate charge source. 

 

What engine do you have?

 

 

 

 

 

[Mouldylocks]

6 minutes ago, Jen-in-Wellies said:

Welcome to the forum. A couple of questions.

Do you have a multimeter?

Do you have an alternator warning light? If so, what is it doing with the engine off and with ignition off? Engine running?

 

Hello thanks for the welcome - yes I do have a multimeter. I dont have any warning lights that I can see (as in I don't think that they exist!).

[MtB]

12 minutes ago, Mouldylocks said:

I dont have any warning lights

 

This is highly unlikely. 

 

Again, what engine? 

 

 

 

(Or post a photo of it please, if you don't know!)

[Tonka]

5 minutes ago, MtB said:

 

This is highly unlikely. 

 

Again, what engine? 

 

 

 

(Or post a photo of it please, if you don't know!)

He said Lister SR2

[MtB]

4 minutes ago, Tonka said:

He said Lister SR2

 

Weird, this only just showed up for me!

 

So a single alternator then...

 

Need the results to to tests I suggested then

 

 

[Jen-in-Wellies]

32 minutes ago, Mouldylocks said:

 

Hello thanks for the welcome - yes I do have a multimeter. I dont have any warning lights that I can see (as in I don't think that they exist!).

It's possible some one has put in a low value, high power resistor to do one of the jobs of an alternator warning light, but why any one would want to do that and not have the information the light can provide is beyond me.

[Tony Brooks]

Welcome

 

Just now, Tonka said:

He said Lister SR2

 

So camshaft driven at half engine speed unless it has been modified with idler shaft and pulleys or someone has managed to get a very larger engine pulley onto it. That is not a good start.  The engine will need to be revving fairly fast to get a sensible alternator output. Idle will not do for battery charging.

 

As it seems this is a single alternator engine, the problem might be a faulty charge splitter the OP knows nothing about.

 

I would leave all well alone and connect the meter (20V DC) to the pos and neg start battery terminal clamps. Then start and rev the engine. The meter should jump up to at least 13V it the alternator has output. That does not mean all is well, but it is a good start. No jump up the check the alternator drive belt and conclude a faulty alternator.

 

Note - the alternator almost certainly needs a warning lamp for it to energise, but it just might use a rising oil pressure switch to energise it. no one can tell without inspecting the boat - unless you know what to look for.

 

Let's assume the voltage does jump up and you fit a new battery. Start and rev the engine, and you should see a voltage of around 14V, keep the engine running and eventually the voltage should rise to14.2.to 14.4 volts. If you do all is probably OK with the alternator. If not, then suspect an alternator or wiring fault - like no warning lamp.

 

I fear that you are well on your way to ruining the domestic battery as well. The solar should reach that magic 14+ volts at the end of a bright day, if not you are definitely undercharging them, although in the morning, before dawn I find 13V unbelievable. A fully charged  lead acid battery after an overnight discharge should never show more than 12.8V

 

A photo of the alternator will help us idetify it.

 

 

 

 

 

 

 

4 minutes ago, Jen-in-Wellies said:

It's possible some one has put in a low value, high power resistor to do one of the jobs of an alternator warning light, but why any one would want to do that and not have the information the light can provide is beyond me.

 

Definatley, but does the OP have an ignition switch or just a push button start button. The boat is probably old enough to have suffered any peoples' attention.

[bizzard]

If you can reach the engines decompressors and start button at the same time use them, they will lessen the load on the batteries and starter motor, especially in this colder weather when the oil is thicker.

Edited October 14, 2024 by bizzard

[Paul C]

I have a "suite" of 3 meters which I use to check batteries: multimeter; DC clamp ammeter; and battery tester (Topdon Artibattery 101). The multimeter, reading voltage settings, is convenient to answer a basic "is it being charged or not?" question. The ammeter shows how much charge (and discharge) there is; and the battery tester can (theoretically) show battery capacity and state of charge. 

 

Regarding jumping from the leisure batteries, the answer is, so long as you can put back in the energy that you used in starting, then you'll be fine indefinitely. I am trusting that its a setup with an alternator as well as solar.

[Tony Brooks]

I had another thought, being an SR Lister with the camshaft driven alternator. Assuming the alternator drive has not been modified, they may not be revving the engine enough to energise the alternator, and in that case the charge light would not go out. That opens the possibility that the OP thinks the charge lamp is an ignition on warning lamp. If this is the case, it would explain a flat engine start battery.