Saturday, 30 January 2016

Jubilee gets a new alternator (and a diesel top-up)

By way of a break from relentless alternator argy-bargy here's a shot from this morning as the Jules Fuels boat prepares to untie and call on us, as arranged, to sell us some diesel. I like to keep topped up during the cold weather in order to minimise the amount of condensation in the tank.

So, back to the alternator. Yesterday afternoon, as a result of a conversation Jan had on Facebook, Tim Casentieri turned up with a brand new alternator for me! I had paid over the phone while Tim had been at Electrostart in Daventry; then he and his wife, Roberta, drove over to see us and help me install it.

Well, Tim actually did the installing; Jan supplied coffee and I passed over various tools as required. Tim preserved the "bolt-on" regulator as per the original setup. When I started the engine my current meter didn't show a big increase in the charging current over what it had been when running on the engine alternator alone. I put that down to the fact that the batteries were already well charged. Time was getting on, so Tim and Roberta left and I continued to think about the Sterling ABC and whether that was helping or hindering. I still don't really know.

There is at least one good thing the Sterling device does, which is to limit the charging voltage to 14.4V to keep the sealed lead-acid batteries happy.

Here is a poor photo of the back of the new alternator, taken after I'd replaced all the deck boards and just before we drove home (oops!)

This morning I disconnected the Transpo regulator and started the engine. It seemed to work as before (but the feed to the "L" terminal was taken from the engine battery side of things - not how it should be). As a better test of the alternator's capability I switched on the inverter and plugged in a 800W toaster. I was pleased to hear the engine note drop; when I consulted the current meter I saw it reading about 33A. Good. (The inverter supply doesn't go through the current meter's shunt, so the reading doesn't reflect the power consumed/supplied.)

Then I reconnected the Transpo and performed the same test. Same result. The alternator stayed gratifyingly cool throughout. After lunch I winded Jubilee and we returned to Thrupp Wharf Marina. During the journey I noted that the battery voltage stayed at 14.3V the whole time. I seem to remember that, in the past, the voltage would sometimes be 14.4V and sometimes 13.7V. This, presumably, was when alternators and Sterling ABC were all working properly. Now I am really suspicious of the ABC, but don't know how to test it.

Dave Ward's advice to me is to ditch it altogether, separating the two charging systems (engine alternator/battery and domestic alternator/battery bank). I am inclined to think that might be the best thing to do, but I have some time to consider the options before returning to the boat.


Nev Wells said...

Hi John,

Glad you got it sorted.... one thing you don't want is a question on the charging circuit, especially if it has the potential to cause a fire? It got me thinking the last part about having a dedicated alternator for the start and one for the leisure batts. I have never owned a boat that had any more than 1 alternator. I can understand having a larger alternator charges the leisures up quicker (?) and having two alternators means both starter and leisures are charged at the same time. However I have a smart bank on Percy and it seems to do a decent job of monitoring the start battery and disconnecting the charge to it when it has what it needs then directing all the charge to the leisure batts. Seems simple to me and it works well this way and only needs the one alternator 70 amp on Percy IIRC (I also have the option of emergency connect to start the engine by adding the leisures to the starter if needed. Two alternators = more belts or do the run off the same belt and more load on the engine when both alternators are charging. I must be missing a crucial point ?

Halfie said...

Well, Nev, it might be slightly premature to say it's sorted, but we're getting there. The two alternators run from separate belts. You're right, there is more load on the engine when both sets of batteries are charging, but the starter battery supplies only the starter motor and the bilge pump. It recharges very quickly and is kept fully charged for most of its long life. The Sterling device is meant to utilise some of the "spare" capacity of the engine alternator, diverting it - as in your system - to the domestic batteries.

I think the real reason for the separate "domestic" alternator on many boats is to be able to have one that can supply more current. The (original) engine alternator often runs on a V-belt which also drives the water pump; a 70A alternator must be near the limit of what that belt can cope with.

Steve Parkin said...


Regarding you comment about 70A being near the belt-driven limit.

I run a 90A Bosch alternator for the domestic batteries on Albert via an Adverc system so it is feasible to go beyond 70A with a belt. Is say "belt" but there are two v-belts driven, because of the traditional engine, via a large drive pulley system. Belt "wrap around" on the alternator pulley has been a recent issue (check out this technical term) so I recently reduced the drive ratio and fitted a slightly large diameter at the alternator end. I would't want to go above 90A unless I had a more "meaty" engine than the Ruston 2YWM.

The engine start battery is supplied by a separate 35A Lucas alternator through standard belts and without any battery management.

Further details on:

Best wishes, Steve

Nev Wells said...

I am starting to get alternator envy !!

I have three 135am/h leisure batteries and I reliably put about 10% per hour into them when charging - this was the same as on Waterlily with much the same battery/alternator set up 70amp alternator and about 400amp hour batteries. i guess there is a calc there somewhere.

I type this with guilt as I know I do not carry a spare belt - and we all know what that means ! Even more foolish when i was held up for a day on holiday a couple of years ago for the want of a spare belt...

Nev Wells said...

.... sorry to hijack the comments but I have just read Steve's blog (not sure why I have not got Alberts blog on my blog roll, and no way to leave a comment on Steve's blog) very interesting and some food for thought and checking of how my set up performs compared to Alberts. Interested to know where the optimal RPM of an alternator is calculated/found?

Halfie said...

Steve, I see that your 90A alternator is driven by two V-belts, not just the one as in my engine alternator. That halves the load on each belt; in addition, your alternator doesn't share the belts with a water pump, which would reduce the wraparound. That's why I suspect that a single V-belt driving a 70A alternator and a water pump might not want to do too much more. The domestic alternator is driven by a flat multi-grooved belt which must be the equivalent of at least three standard V-belts. I was interested to read that you sacrificed a little alternator RPM in the interests of extra wraparound, but I think you said that you don't think it has affected the charging. Could I make a plea, with Nev, that you enable comments on your blog? There have been several occasions in the past where I would have left a comment had I been able to. Oh - the garage you mentioned. I must have walked right past it when looking for somewhere to ask about testing my (dead) alternator! We were moored at Old Wolverton when all this happened.

Nev, one of the links Dave Ward kindly sent me was this very useful one
to some Prestolite info. Here, for this Prestolite AVI128 alternator (the one which died) it says that "the ALTERNATOR MUST EXCEED 1200 RPM to start charging: “Cut in speed.”" I think this refers to the point at which the alternator starts to supply enough current to energise the field coil and so start working properly. I think the basic principle is the faster the better, but don't take my word for it. This reminds me - I ought to measure the two pulley sizes to be able to calculate the alternator speed for a given engine speed (as Steve has done on Albert).

John Lomax said...

Hi - Glad to read you now have a working alternator.

With regard to whether you decide to ditch the sterling ABC or not Dave Wards clarification that you have the alternator to battery controller rather than the advanced regulator was very useful . This got me interested so i looked at the Sterling website. Put simply it acts like a phantom load, causing the alternator with its standard regulator to produce output current and then the ABC puts this current out at higher voltage steps so that it can charge the battery. On the domestic bank the in built control electronics cause the same multi step charging as an advanced regulator, but without any physical mods to the alternator. This means that if you compare graphs of output current and voltage delivered by the alternator over time for the ABC fitted and working and set properly (eg output voltage needs to be set according to battery type) against standard regulator you see faster and more complete charging. Faster because the ABC sustains the charge current for longer. More complete because a standard regulator stops charging when the battery is only at 80% of its rated capacity. (the ABC also has a separate output to the starter battery but not multi stage)

Because the ABC makes the alternator work harder it will generate more heat for than standard mode (it may not get to a higher temperature than in standard reg mode, but it would run warmer longer). In any event, assuming the ABC temp sensors are attached to the alternator, they cause the ABC to shut down leaving a standard alternator/regulator set up and a high alternator temp warning comes on.

Overall, given how it operates it is hard to see the ABC as the culprit in failure of your old alternator and it is very likely it still works, if it doesn't you are in standard mode as you are now. It would be worth discussing this with the technical guys at Sterling if you plan to reconnect the ABC.

As Dave suggests you could ditch the ABC as long as you can live with the reduced charging performance. If you had say 3 x 110 amp hour domestic bank and you run long enough to 'fully charge to 80%' you would have the equivalent of 3 x 110 x 0.8 ie 264 max amp hours available, as only the top 50% of capacity of a battery is useable the useable capacity from the bank would be from 264 down to 165 (call it 100 amp hours) whereas properly fully charged (ABC working) useable capacity would be 330 - 165 (ie 165 amp hours). Also reduced capacity will mean deeper cycling and shorten battery y life.

When i had a similar alternator failure on Jay 2 last year I went down the 'ditch the smart regulator' route for the sake of simplicity and getting a working alternator, i certainly experience the loss of available capacity but this is OK for my current cruising , i can live with the reduced capacity for a few weeks until i get back to my mooring/landline when my victron gets me back to 100% charge. The time may come when i want to get back to smart charging and i will consider an ABC as an alternative to testing /reinstalling my alphapro.

You asked how to tell if the ABC is working? I believe the unit has indicator lights which show the status. A more definitive test would involve measuring output voltage and current for ABC which would show the multi stage profile.

Whichever way you decide to go I hope this helps (apologies if you knew all this already)

Halfie said...

John, thanks very much for this. Despite the LEDs lighting up as normal on the Sterling device I'm not sure if it's working. I think you're right - I'd have to measure voltage and current over time to see if it's doing what it should.

Since fitting the replacement alternator I haven't really run the engine much, and not with the domestic batteries needing much charge.

As you say, the better charged the batteries the more the available amp hours. I am continuing to reduce my demands on the batteries - I can now recharge the laptop from a small DC-DC converter without having to run the inverter. We don't have a TV; our lights are all LEDs. The next thing to sort out is the fridge. This is currently a mains fridge requiring the inverter to be on all the time while cruising. A 12V fridge should, I think, be more efficient (but costs a small fortune!). I have started a small modification which I will post about shortly.