2 alternators...

Submitted: Saturday, Oct 06, 2007 at 16:51
ThreadID: 50297 Views:3538 Replies:3 FollowUps:8
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Hi, sort of an OT one, but it has bugged me for a while so I thought I'd ask here....

If you have a boat with twin engines, and each has the same alternators, are they happy to run in parallel for extended periods, or should they be kept separate most of the time, and only switched together in a 'jump start' type situation. Both engines would have totally separate starter batteries etc, but the house batteries need to be charged from somewhere....best to keep it from just one of the alternators (but can be chosen between both), or just have it all hooked up in parallel for maximum charge..?

Cheers Andrew
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Reply By: BennyGU - Saturday, Oct 06, 2007 at 18:27

Saturday, Oct 06, 2007 at 18:27
The easiest thing to do mate might be to go down to the local chandelery (distance I know:)) but there a lot of very easy smart charge circuts that offer linkages as well as the on/off for each battery in the circut.

Having a look in my BLA catalouge there is a mob called BEP Marine that make a smart battery management system for twin engines and can manage up to two start batteries and a house battery bank.

"The Voltage sensitive relay unit will direct the charge from the port and starboard engine to the port and starboard start batteries respectively then to the house battery bank. This can, when directed (both start batteries are charged) give a combined charge to the house battery bank until the voltage regulators of both engines control the charge. This system will also allow the house battery to be charged if steaming on one engine"

so I believe from the above that yes both are happy to run in parrallel.

The BLA part number is 113686 (max 50Amp charge) or 113687 (max 90 Amp charge). For 90amp advertised price is $482.00

They can be bought online through Northside Marine (North Brisbane) online store. Link below. Highly reccomended lot, used to be a store rat.

http://www.bla.com.au/index.php?fn=productGroupView&dId=73&id=2172&eId=730&sId=8f129ce1a9c34ff81b5ad089864f8aaf

(tried putting it in a link but it didnt like me)

Ben
AnswerID: 265322

Follow Up By: Member - andrew B (Kununurra) - Saturday, Oct 06, 2007 at 18:33

Saturday, Oct 06, 2007 at 18:33
Thanks for that Ben, looks like a good system (better than a few manual isolater switches!)

Cheers Andrew
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Follow Up By: BennyGU - Saturday, Oct 06, 2007 at 21:30

Saturday, Oct 06, 2007 at 21:30
Evening Andrew,

I just noticed that you've got LPG on your 2.8 GU. My 2.8 is going in for a chip and zorst next week and I was wondering how you found the LPG in terms of power/torque increases and economy.

Ben
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Follow Up By: Member - andrew B (Kununurra) - Sunday, Oct 07, 2007 at 07:18

Sunday, Oct 07, 2007 at 07:18
Gday Ben. The gas was good while it worked, but I have an issue with the converter, it seems that our LPG has an oily residue that affected a certain batch of these, of which I have one. (covered under warrenty, but there is no LPG installers in town, and the nest town is quite a way so I haven't got it fixed yet!

The power increase on mine was 14% (dyno), and is much more 'driveable'. (not as many gear changes). The fuel usage in volume remained the same, went from 14l/100k strait diesel to about 11ld, 3lgas/100km, si a saving of about $1.80 per 100km. At that rate, it should pay for itself in about 80,000km (after wa and national rebate). The car probably wont last that long, but if you consider you have also got a performance mod a bit like a chip (possibly not as much power increase though), an extra 28 litres of fuel (about half the extra capacity of an $800.00 long range tank) I think it has paid for itself quite quickly.

With the trouble mine is giving at the moment, In a way I would have prefered to go down the same lines as Lucy did, with a much simpler system, but you can tweak my kit quite a bit if you live near an installer. (lovato's) Ther is another sophisticated system out there that you can plug your mobile phone into and have it tuned remotely, but they were about an extra $1000.00 when I was looking around for one.

If you are considering it, but still getting the exhaust done next week, it may pay to get the exhaust modified so that the tank will fit at a later date, the tank goes where the big mufler is, sorry, have no photo's of mine at work.

Cheers Andrew
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Follow Up By: BennyGU - Sunday, Oct 07, 2007 at 09:28

Sunday, Oct 07, 2007 at 09:28
Thanks Andrew,
My upgrade is getting done by Taipan XP near the Gold Coast who are agents for diesel/gas Australia. I was on the phone to them this morning and they will reroute the exhaust slightly so that I can have room for a lpg cylinder in the future with little fuss and no extra moolah as the Vortex muffler is tiny compared to the bloody crate sized thing under there now.

The expected figures post DPChip and 3" Vortex exhaust are 128kw and 355Nm, so with a 4.7 diffs I should be able to outrun a 3.0l GU with little hassle. I have also blocked my EGR (about 4 years ago) and I have found this is possibly one of the best things a little diesel such as ours could have done. Brought the turbo on 300rpm earlier instantly, no more black smoke, 0.5l/100km better fuel economy and the engine oil is so much cleaner it aint funny.

If you want the instructions and a drawing of the blocking plate sent to your email address let me know.

Ben
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FollowupID: 527335

Reply By: Member - Olcoolone (S.A) - Saturday, Oct 06, 2007 at 18:48

Saturday, Oct 06, 2007 at 18:48
Andrew, it all depends on what type of alternators you have and the way they control charging/output if you want to isolate one alternator or the other.

Most alternators will work OK in parallel aslong as the voltage out put of each one is the same.

With the new vehicles comming on the market whereby the alternator is controlled by the engine ecu you will not be able to run twin alternators as the engine ecu will detect a fault.

The new Holden Commodores have a charging voltage of 16.7 volts so even fitting a second battery may be an issue.

Alot of high demand vehicles like ambulances have twin set ups.

If you requirer higher current output sometimes using twin alternators is better than one large one, as the current increasers with a single alternator so does noise and the signal /voltage becomes dirty causing interferance in electronic gear.

If you want higher current output from SOME standard alternators you can look at changing the windings from a star to a delta configeration, with a star winding you get a higher voltage and lower current and with the delta winding you get a higher current with a lower voltage.

Its all abit of give and take depending what you want.

Regards Richard




AnswerID: 265326

Follow Up By: furph - Saturday, Oct 06, 2007 at 19:27

Saturday, Oct 06, 2007 at 19:27
Richard.
Is that correct "new Holden Commodores " have a charging voltage of 16.7v.
I am led to believe the optimum for a flooded 12v. wet cell battery was 15.0v max. charge, 13.6v. float.
Anything above 16.0v. becomes an "equalizing" charge, not recommended as a nomal charge rate.
My small 5a. 240v. unregulated charger at 15.0v. soon boils the battery dry.
furph
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FollowupID: 527263

Follow Up By: Member - Olcoolone (S.A) - Saturday, Oct 06, 2007 at 19:43

Saturday, Oct 06, 2007 at 19:43
Opps just read my post again and it should of read charging upto 16.7 volts, th VE's use a calciume battery and yes they are having problems with them.

Regards Richard
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FollowupID: 527268

Follow Up By: Member - andrew B (Kununurra) - Sunday, Oct 07, 2007 at 07:21

Sunday, Oct 07, 2007 at 07:21
Thanks for that Richard, the kiss principle seems to be the best bet, Either a fully automated system or simple switches may be the go, with a switch between 2 house batteries so they can be charged by an engine each...
Cheers Andrew
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FollowupID: 527309

Reply By: Philip A - Saturday, Oct 06, 2007 at 21:57

Saturday, Oct 06, 2007 at 21:57
I have two alternators on my 3.9 Range Rover.
I run 2 completely separate circuits,one for the starting battery, and one for the AGM for the fridge/winch etc.
To equalise the load I have fed my spots from the second .
This way you avoid any electronics and the AGM charges much faster, maybe 2 hours to 90% and another 4 to 100% from 11volts on my 95AH.
You also know immediately of any system problems. eg my starting battery is dying and I could tell by the output of alternator 1 being down. The megapulse is delaying the inevitable for a while.
Regards Philip A
AnswerID: 265350

Follow Up By: Member - andrew B (Kununurra) - Sunday, Oct 07, 2007 at 07:25

Sunday, Oct 07, 2007 at 07:25
Gday Phillip. I am hoping (one day!) to buy the ultimate offroad vehicle (big boat), which will have 2 alternaters and 2 engines. Both will have starter batteries and be stand alone, but there will be a 3rd battery(S) for the 'house'. I was thinking down the same lines as you with keeping them totally seperate, so that the diagnosis of a problem with either battery or alternator is easy to find and doesn't mask or kill the other unit if there is a problem.

Unles 6 lucky numbers come up in the near future, I have a bit of time to plan a system...a megapulse may be a good investment one day...

Cheers Andrew
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FollowupID: 527310

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