Jump to content

Alternator getting very hot


Featured Posts

Firstly thanks to everyone for the time spent looking at this problem and offering advice. Hugely appreciated. So having spent a few hours on the boat today here is the update ....

 

In answer some of the questions:

  • Current being drawn on the domestic side without anything being used was around 0.05 to 0,1 amps. When the fridge kicked in it was around 3.1 amps. This all seemed about right.
  • The controller I was referring to was the MPPT solar controller and today it was putting out about 5 to 6 amps.
  • The alternator output was around 40 to 50 amps on idle.
  • At no time did the batteries seem particularly hot (hard to tell in the housing) or out of shape and I couldn't smell anything out of the ordinary.

Today I spent time taking readings and watching what was going on and nothing seemed out of the ordinary. I put the engine on and it actually got up to about 13.9 volts, but the alternator was still getting way too hot. I don't have any means of measuring the temperature but I could hold my hand on the other one without any issue but the domestic alternator was too hot to touch for more than a second.

 

So, I decided to put on two spare batteries that I had and swapped out the two brand new ones. The spares were a little old and not a perfect match but thought I would give it a go. It went straight to 14.2 volts charging .... looking better. The main thing was that after running the engine for a while the alternator was not hot at all. We then moved the boat and cruised for about 4 hours. Alternator still a normal temp and much the same temp (albeit by feel alone) as the starter one.

 

I know the batteries I put on were not great shape and so don't expect them to perform that well but does the fact that the alternator remained a normal temperature indicate that the problem lies with the new ones? I have taken one back to where I bought them and I am waiting for them to test it and get back to me.

Link to comment
Share on other sites

22 minutes ago, rgriffiths said:

Firstly thanks to everyone for the time spent looking at this problem and offering advice. Hugely appreciated. So having spent a few hours on the boat today here is the update ....

 

In answer some of the questions:

  • Current being drawn on the domestic side without anything being used was around 0.05 to 0,1 amps. When the fridge kicked in it was around 3.1 amps. This all seemed about right.
  • The controller I was referring to was the MPPT solar controller and today it was putting out about 5 to 6 amps.
  • The alternator output was around 40 to 50 amps on idle.
  • At no time did the batteries seem particularly hot (hard to tell in the housing) or out of shape and I couldn't smell anything out of the ordinary.

Today I spent time taking readings and watching what was going on and nothing seemed out of the ordinary. I put the engine on and it actually got up to about 13.9 volts, but the alternator was still getting way too hot. I don't have any means of measuring the temperature but I could hold my hand on the other one without any issue but the domestic alternator was too hot to touch for more than a second.

 

So, I decided to put on two spare batteries that I had and swapped out the two brand new ones. The spares were a little old and not a perfect match but thought I would give it a go. It went straight to 14.2 volts charging .... looking better. The main thing was that after running the engine for a while the alternator was not hot at all. We then moved the boat and cruised for about 4 hours. Alternator still a normal temp and much the same temp (albeit by feel alone) as the starter one.

 

I know the batteries I put on were not great shape and so don't expect them to perform that well but does the fact that the alternator remained a normal temperature indicate that the problem lies with the new ones? I have taken one back to where I bought them and I am waiting for them to test it and get back to me.

 

This does sound to me as though the alternator is simply working really hard charging up the (very flat) new batteries. Have you used a clamp meter to measure the current going into the new batteries while the alternator is getting so hot? What is the charge current?

 

 

Link to comment
Share on other sites

44 minutes ago, rgriffiths said:

Yes - it was around 40 to 50 amps. Very similar to when I swapped them to the old ones.

 

Ok so both sets quite discharged. 

 

Have you measured the actual temp of the alternator?

 

 

 

Link to comment
Share on other sites

And the comment about charging on idle. If this is what you are doing then its a bad idea.

 

1. The alternator speed is low so its cooling fan draws less air through the machine,

2. The alternator will not be providing the maximum charge it can.

3. There will be a lower load on the engine that there would be at a higher speed.

4. If you are  also heating water the that will take longer as well.

 

It is best to increase the revs out of gear until your ammeter stops rising and then over time and as the voltage rises you will find that you can reduce the revs so the charging current is still as high a sit will go. This will be lower than at the start because the batteries are charging up so demand less current.

  • Greenie 2
Link to comment
Share on other sites

It would be useful if you could take the two new batteries and separately charge them up using a mains powered charger for say 12 hours.  After a battery has been charged measure the voltage of that battery, then leave for 24 hours and measure the voltage again, tell us what you get.

Link to comment
Share on other sites

3 hours ago, ditchcrawler said:

But the old batteries probably came up to full charge faster due to lower capacity 

Yup. 

12 hours ago, Mike the Boilerman said:

This does sound to me as though the alternator is simply working really hard charging up the (very flat) new batteries.

Definitely. 

5 hours ago, Tony Brooks said:

And the comment about charging on idle. If this is what you are doing then its a bad idea.

 

1. The alternator speed is low so its cooling fan draws less air through the machine,

2. The alternator will not be providing the maximum charge it can.

3. There will be a lower load on the engine that there would be at a higher speed.

4. If you are  also heating water the that will take longer as well.

 

It is best to increase the revs out of gear until your ammeter stops rising and then over time and as the voltage rises you will find that you can reduce the revs so the charging current is still as high a sit will go. This will be lower than at the start because the batteries are charging up so demand less current.

All very good advice - take note :)

 

Remember that it will take anything up to 12 hours to fully charge very flat batteries. If you’re only giving the new batteries a couple of hours then they’ll still be very flat. 

Link to comment
Share on other sites

Echo the "All very good advice".

 

It is quite possible that the new batteries were completly flat from the shop as .... and I agree this was not clever ... they were not tested when purchased. However when they were installed nothing was to suggest that they were flat. Little green ball showing and reading 12.4v (from memory).

 

I agree the old batteries would come up to full charge faster due to lower capacity but they are in OK condition.

 

Still wating to hear back from the shop as to whether one of the new ones was a dud. I will update when I find out more.

8 hours ago, Chewbacka said:

It would be useful if you could take the two new batteries and separately charge them up using a mains powered charger for say 12 hours.  After a battery has been charged measure the voltage of that battery, then leave for 24 hours and measure the voltage again, tell us what you get.

I plan to do this when I get a chance. Good idea.

Link to comment
Share on other sites

11 minutes ago, rgriffiths said:

Little green ball showing and reading 12.4v (from memory).

 

Oh dear, the 'little green ball' was still showing on the last set of utterly dead batts I weighed in, having dutifully topped them up fully to the brim with tap water. I don't think I've ever seen the little green ball gone!

 

12.4v equates to about 70% SoC. 

 

Link to comment
Share on other sites

  • 4 weeks later...

So.... Just in case anyone is interested. Batteries have finally come back from being tested and they were faulty. New set on and everything is rosy. 

 

Miles of driving and removing/refitting alternator etc. But pleased to get to the bottom of it. 

 

Thanks for all the help and advice. 

 

  • Greenie 2
Link to comment
Share on other sites

7 minutes ago, rgriffiths said:

So.... Just in case anyone is interested. Batteries have finally come back from being tested and they were faulty. New set on and everything is rosy. 

 

Miles of driving and removing/refitting alternator etc. But pleased to get to the bottom of it. 

 

Thanks for all the help and advice. 

 

Thanks for coming back with the answer.

 

I'll always try and look at the simplest thing first and that is generally 'flat batteries' but the trick is then finding out why the batteries are flat.

 

Hopefully now, with careful battery maintenance, you'll have many months of trouble free electrickery.

Link to comment
Share on other sites

14 minutes ago, rgriffiths said:

So.... Just in case anyone is interested. Batteries have finally come back from being tested and they were faulty. New set on and everything is rosy. 

 

Miles of driving and removing/refitting alternator etc. But pleased to get to the bottom of it. 

 

Thanks for all the help and advice. 

 

 

Thanks for getting back with the reason. So many people don't. 

 

Did the supplier say exactly what was wrong with the batteries?

Link to comment
Share on other sites

2 minutes ago, cuthound said:

 

Thanks for getting back with the reason. So many people don't. 

 

Did the supplier say exactly what was wrong with the batteries?

Ditto

 

Even if he did not then the only logical thing that would drop the battery voltage like that and pull down the charging voltage because of high charging current would be internal short circuits although if a symptom was a very quick charge and discharge time it could have been sulphation.

Link to comment
Share on other sites

33 minutes ago, Alan de Enfield said:

but the trick is then finding out why the batteries are flat.

 

 

Exactly this. 

 

I'm sure we have all in our younger days bought a new battery for the car then found a week later the new battery runs flat too, and we tightened up the fan belt!

 

All except me that is. I never did that, oh no, deffly not, not me, never!! ???

 

 

:giggles:

Link to comment
Share on other sites

I don't know what was up with the battery but will ask when picking up the replacement. They say that they have not had to send one back in years. 

 

I did try all the simple stuff first. I just didn't expect brand new batteries to be damaged inside and lugging them around and taking them back to the shop etc etc was a real pain. 

 

Link to comment
Share on other sites

1 hour ago, Tony Brooks said:

Ditto

 

Even if he did not then the only logical thing that would drop the battery voltage like that and pull down the charging voltage because of high charging current would be internal short circuits although if a symptom was a very quick charge and discharge time it could have been sulphation.

 

Exactly, during the early days of VRSLA batteries, it was relatively common  for a plate to drop off the group bar and cause an internal short circuit. The cause of the plate falling off was electrolytic corrosion between the pure lead group bar and the lead calcium alloy plate.

 

However I haven't heard of this corrosion problem since maybe the mid 1980's.

Link to comment
Share on other sites

5 minutes ago, cuthound said:

 

Exactly, during the early days of VRSLA batteries, it was relatively common  for a plate to drop off the group bar and cause an internal short circuit. The cause of the plate falling off was electrolytic corrosion between the pure lead group bar and the lead calcium alloy plate.

 

However I haven't heard of this corrosion problem since maybe the mid 1980's.

More likely to be the lead sulphate, which takes up more space than the lead oxides it replaced rubbing through a separator or excessive build up of plate material right to the top of the sediment traps and touching the bottom of the plates on a typical boat battery.

Link to comment
Share on other sites

31 minutes ago, Tony Brooks said:

More likely to be the lead sulphate, which takes up more space than the lead oxides it replaced rubbing through a separator or excessive build up of plate material right to the top of the sediment traps and touching the bottom of the plates on a typical boat battery.

 

Very possibly, or as they were new wet cell batteries another possibility could be way too much active material squeezed into the plate pockets during manufacture. The excess falls off during the formation charge and first few charge/discharge cycles and builds up on the bottom of the battery. However it would need to be a lot to build up enough to short cells on a new battery.

Edited by cuthound
Clarification
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.