Dual Alternator update

[iangrant]

Thanks for all the posts - Well, I think I understand the wiring now, hanging upside down a lot etc.. etc..

Spent a while last evening and checked the mechanical fixing of the alternator and the wiring.

Mechanics all OK, just off to buy a fan belt to fit - Ha Ha. and a new velo alternator

Wiring -
6 Domestic batteries, 2 engine -
There is no domestic draw from engine batteries, they are completely isolated. **

The port alternator is as nature intended - wired directly as a dedicated supply to the two engine batteries.

The starboard alternator is wired through a 1-Both-2 switch with it's output connected to the common. So it is switchable 1 (engine) - 2 (domestic) or both..

So ** if it is switched to both there is an emergency domestic draw from the engine battery, or charging of both banks.

There are two sterling alternator controllers ready to be connected, but I'm reluctant to take apart the 200 quid 90 amp alternator Starboard to solder a field wire to the brushes!
I may look at the Veleo alternator replacement one with a view to connecting up proper like..

The question still arises - if I connect the two alternators i.e switch to "both" with both alternators running - will they go bang?

All great fun


Ian

 

[pvb]

I have a similar set-up on my HR. Original engine alternator only charges the engine battery. Second alternator (Prestolite 90A) feeds domestic bank (660Ah).

I'd strongly recommend you add a smart regulator to your 90A alternator - it will transform the charging of your domestic bank. Don't worry about adding a smart regulator to the other alternator, your starter batteries will be fine with the standard alternator.

Would also strongly recommend you get rid of the 1-2-Both switch. It would be much better just to wire your 90A alternator direct to the domestic bank. There wouldn't be a "bang" if you switched to Both with the engine running, but you wouldn't gain anything. The worst feature of the 1-2-Both arrangement is that it has the potential to be put in the wrong position (perhaps by a well-meaning crew) and that could leave you either with an uncharged domestic bank or, worse still, a depleted starter battery. There's no real need to be able to connect both alternators to the domestic bank because, unless you add a few more batteries, you won't be able to push more than about 90A into the domestics. Much better to keep the system as simple and foolproof as possible.

An added consideration is that if you have a smart regulator controlling your 90A alternator with the sense wire on the domestic bank, in the event that someone puts the 1-2-Both switch so that the charge output goes to the engine batteries only, the regulator may sense the lack of charge at the domestic bank and progressively increase the alternator voltage thus boiling the engine batteries. I've seen this happen on an Adverc installation when one leg of a diode splitter failed.

 

[iangrant]

Dual Alternator long update

All fixed up and working, now, mind you I did have a couple of challenges, firstly the mechanics of it, I had to remove the water pump pipe to wriggle the beastly new alternator in, then I took it out again to do the sterling bits, lesson one; read the manual first!

I read the sterling crib sheet and took the alternator apart and soldered a wire onto each brush, re-assembled and fitted it onto the brackets again (note to self, when brusing on arms gone down, retreive 13mm spanner from bilge)

Then the wiring:

Brown from sterling to D+
Big red from battery switch to B+
Black wires from sterling and engine case to earth stud
Yellow wire from sterling to ignition switch.

Reconnect water pipe mop up water in bilge, fiddle about with fan belt adjustment upside down arm gone dead etc... fire up engine - SOD ALL - NOTHING.

So I 'phone Bob at superstart he says "have you excited it"? (me thinks maybe I should show it the old alternator with no clothes on) "you need a 12 volt feed to D+"

So out with the meter and found the yellow ignition wire had 12v when switched on, perfect. (beware exciting alternator from non switchable source, that will flatten the battery)

Fire up again Bingo 14 volts, then back to the sterling sheet, measure the voltage on the brush wires sure enough one at 14 volts the other at 10. Isolate the 14v one and connect the 10V one to the sterling and all the lights go on.

I then ran the engine and got some 30 amps at tickover dropping in half amp stages as the nearly fully charged batteries said they have enough electricery thanks.

Very pleased with myself I put the kettle on (and a couple of plasters) then spent an hour or two cleaning up and doing other stuff as Tome was due to arrive later on.

About three thirty I thought I'd fire up the engine again to enjoy watching the charge rate - 60 amps on the meter sucess. Then I'm sat there wondering what exactly the funny smell was then thought it odd I could see across the saloon, stop everything maximum meltdown..

Anyway the belt was really hot (lucky I had some burn cream the blister's gone down now)

What had happened was that the fan belt had "sunk" into the pulley and the friction was just too great. So I unpacked the tools again, unbolted the pulley and removed the shim washers so the top of the belt was level with the outer edge of the pulley. Of course the bloody belts a bit too short so I can't slip it over the pully I have to undo the alternator Again, but this time the 12V B+ touches the engine case - BANG - the bump on the back of my head is gradually going down now.

Bolted back together fire up and no more belt smoke just the smell of very hot paint/resin, but I guess at 65 amps the little metal lump is bound to get a bit hot!

Saturday morning off we go to the Folly meet with two alternators both charging their respective battery banks.


Happy days, now test the towing generator.
Deploy the rope and prop on it's metal stick and it starts to turn, the regulator on the towing gen don't work 8 volts no good! So I grap the rope to recover the prop thing (note to self - practice man overboard drill) I really very nearly got pulled into the drink by it. Slowed down and pulled it in.

So I take it off the back of the boat and carefully remove the lid, putting the screws in the empty ash tray. Poking about a bit it all looked OK inside and 12Volts coming off the bridge rectifier, hmmm thinks put that back together but it's breakfast time Sunday morning and we're just off ryde Pier.

Ate a full English with enough colesterol to stop the average heart and thought enjoy the sail back, B*gger about with the gen at home later.

Back on the pontoon I pick up the empty ashtray - "where's the screws mate?" - eyes gazed down toward the bin liner dripping tea bags fag ash, banana skins etc.... "Ooooh I'll buy some new screws"

And that's sailing!

Ian