24vdc - Newbie Needs Help ! Funny, too !

[ti325v]

Hi Guys....
Thanks SO much for all of your suggestions.
I have looked into a solar system....four weeks in customs and the cost kills it.
I just have a BAD feeling about tapping one of the two 12v batteries....

So, unless anybody can convince me otherwise....I am going the 12 volt added alternator route....I believe it will be SIMPLE, CHEAP at less then $175 WITH the 2 additional batteries, pretty darn bullet proof....as it will simply be a car electrical system on the boat.

The pictures below show the front of the engine with the belt cover off....I think those two bolts that are holding the eye to hang the engine will be a pretty sturdy place to start bracket from... I will will post pix when its done, and the total cost.....oh, and for those of you that do not know.....it is about 4 feet long, without the gear box..... A wheezing 35 BHP, but 350 ft/lbs of torque, max rpm is 1600, prop 522 r.P.M. Weighs about 1,500 pounds !!!!
Rumored to run 25,000 hours between rebuilds !
It cost me about $6,000. Installed !

[simonmd]

Again, I love it when people ask for help and talk about 'local' specilists, etc. but don't tell us WHERE in the world you are!

I'm hopeless with electric so i'll leave that to ther experts on here but I will add that with solar panels, they are usualy mounted flat on a boat. There is no need to mount at an angle because, unlike a house, (not wishing to sound condicending) a boat MOVES! Therefore you can't be expected to turn the boat to the optimum angle for the sun to charge when at sea.

The bilge needs to be sorted ASAP, if you spring a leak at sea, you don't want to be mucking about with changing the flow etc and, most importantly, your engine won't pump the boat out if left unattenteded for any length of time. Auto pumps are available at most good boat chandlers but as you cant seem to find one i'm assuming your not in one of the main 1st world countries? If not, what about online boat accessory dealers or indeed, good old Ebay? I recently got a good self contained 750GPH auto pump for about £50 so even with a lump added on for international postage, it won't break the bank.

[boatman61]

[QUOTE=simonmd;563047]Again, I love it when people ask for help and talk about 'local' specilists, etc. but don't tell us WHERE in the world you are! QUOTE]

I believe he said he's in Vietnam....
Sorry the Solar ideas not viable... good luck with the new set-up.....

[Blue Stocking]

CarlF,

Should he perhaps widen that ratio for alternator speed. His service RPM is probably only 1200 max, which at 2.5 to 1 equates to 3000 at the alternator, where-as on a car he would be getting at least 5000RPM at the alternator. Looking at the data sheets for small case alternators shows most of the them at about 50% hot- rated output at 5000RPM.
Just a thought.

[donradcliffe]

A typical car alternator will put out about nothing at 1000 rpm, and about half its rated output at 2000 rpm. Look at the driving pulley--turn the engine over and see if it runs at more or less than the shaft rpm. Unless it runs at least twice the engine rpm, you are going to have to put a bigger pully on to drive the second alternator--maybe a double pulley.

The lifting lug bolts will make a good start for the alternator bracket, but you should tie in a third bolt which is not in line, like the one used for the alternator tensioner.

[ti325v]

Okay here are a bunch of my boat under construction....the hull planking is 1.5 to 2.5 inches thick, knot free, straight grained hardwood. The frames are 2.25 X 6 inches on 14 inch centers, The gunwale planks are 2 inches thick and 32 inches wide in places, the floor joists are 2 X 8 on 14 inch centers, the roof posts are 7 x 7 inches, knot free.....
Also a back view of my engine with gear box. A 25 meter boat in the shed next to mine...mine is only 15 meters. A model of my boat the kid next door is building for $150....
My WHOLE COMPLETE boat...15 X 4.3 meters....Engine, drive shat, prop, wiring, batteries, Masses of stainless steel to come, I would guess about 250 feet of 1.25 heavy gauge s.s. with all manner of crazy bends, anchors, toilet, pumps, tanks...EVERYTHING...with a fiberglass skin and roof.... $38,000 !!!!!
Also some other photos...my guy did the big tour boat, as well as the 30 meter frame lofting now in orange....

[boatman61]

Originally Posted by donradcliffe

A typical car alternator will put out about nothing at 1000 rpm, and about half its rated output at 2000 rpm. Look at the driving pulley--turn the engine over and see if it runs at more or less than the shaft rpm. Unless it runs at least twice the engine rpm, you are going to have to put a bigger pully on to drive the second alternator--maybe a double pulley.

The lifting lug bolts will make a good start for the alternator bracket, but you should tie in a third bolt which is not in line, like the one used for the alternator tensioner.

OK.... total non electrician here.. apart from normal day to day stuff.....
Why cant he just add extra wires to his Alternator and lead them to a 12v regulator and then to the 12v batteries.... that way 24v and 12v draw of the same source....
Maybe a gem of knowledge that I might need sometime...

[CarlF]

Agreed that he wants about 5000 RPM at the alternator for full charge rate - 3500 isn't bad and 10,000 is too fast. The 2.5:1 ratio is good for newer Yanmars that might have an upper RPM above 3000. I think it's highly likely that the current alternator is spinning at the right speed and that he should just use a similar size pulley.

TI325v - you have mighty fine karma to have that lifting bolt so well positioned. Make sure the bracket you make has oblong bolt slots to let you tweak the new alternator into perfect alignment with the current pulleys. It will probably take some trial and error. You'll know you have it right when a belt lasts more than a few hours. Remember that the shape of the pulley "V" has to fit the belt - both the wide and the narrow parts.

While I'm a great fan of solar panels for cruising sailboats, a dive boat application is really better off with alternators because the charging is done when the engine is also being used for propulsion with no measurable extra use of fuel or engine wear. If you start finding yourself running the engine just to charge, you should look again at those solar panels.

Carl

[ti325v]

here are a few more...Including a model a kid is building for $150

[boatman61]

WOW............... Real 'Lord Jim'.... Joseph Conrad stuff.... I love it

[ti325v]

Thanks all for picking up on my concern about the alternator output...Have a look....the shaft that drives the alternator is not the crankshaft and much more likely a geared up shaft to spin the existing alternator....Of course I have no way to determine little shaft RPM, no I.R. Tachometer here...but it is indeed spinning the 24V alternator up to the correct revs....any ideas if a 12 and 24 V need the same rpms ???
Again...Thanks everybody for sticking with me on this !!!!!!

[ti325v]

BRILLIANT ! Turn the crank once, see how often the little shat turns, so simple it hurts !
THANKS !!!

[sobriyah]

Hi Larry - just looking at the photos of your engine. Its not one I'm familiar with but theres a salt water cooling pump on the front and a heat exchanger on the RHS. You mentioned in one of the posts you have a radiator cap and you would have a funnel. This engine looks like its indirectly coooled. If it is, you will have a closed freshwater cooling circuit cooled by saltwater in the intercooler. Theres usually an injection bend where the saltwater from the intercooler gets injected into the exhaust manifold, just before the exhaust outlet. The exhaust then discharges through the hull, not up a funnel. I would take a good look at the exhausts on the other dive boats.

By the way, what are they using to fix the hull planking to the frames?

[simonmd]

Wow, serious looking boat, she looks like the African Queen!

[Dockhead]

Originally Posted by boatman61

Being a lazy non tech sorta guy I'd not bother with all this complex stuff.... and possible system screw-ups....
Just buy a 12v car battery and a 20w solar panel to keep it topped and dedicate it to your whatevers.....
I do this for my Tillerpilot.... its own dedicated battery seperate from anything else on the boat.... ya gorra look afta de crew..

That's the best solution. Anyway it's much better not to mix engine start with house. Put on a second 12v alternator and some 12v batteries and you're good to go.