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2 alts better than 1


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#11 lateral

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Posted 22 April 2019 - 10:49 PM

Makes sense. Thats why I have forced ext air.

It get away from  a hot rated expensive alt.

And I have a 3GM capable of second alt but whats the point, battery dictates acceptance.

Once you have spare current capacity no point. ie over the 85% shoulder part of curve.

 

A stash of belts green stripes, a  quality auto ext regulated spare alt & i'm good at this stage.

Custom belt tensioner I fabbed.

 

Although I suspect IT is right. But my whole setup cost a third of a Balmar.

Strictly DIY tho, cant see a pro staking their reputation on it.

 

4.5 hours motoring from barrier from 12.4V  got me to 6A tail current.

Batteries at 12.83V rested 48hrs later.

.


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#12 Crazyhorse

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Posted 23 April 2019 - 08:43 AM

Everyone is entitled to their own opinions of course. All I can say is that if your batts are very low, and your regulator pushes your alt to over 100 amps for a long period - say 5 hours or more - the alt will melt, or the belt will fail.
If the output is short term, or the temp compensation cuts the alt back, then you’ll likely get away with this setup, but your charge time will be extended over what’s possible.
Many people do run those 120a alts on one belt, and have no issues, as they dont make them charge large banks from a low level. But the day you do, you can be in trouble.


Quite agree (as the pages in here from our alternator past issues will attest!). Charging up as I type (again..in the fog). Started at 12.2v from last night (no wind). RPM 1600 and in 12 minutes have bought the voltage up to 14.5v on 240ah SLA and one 80ah start battery currently all charging in parallel. Currently doing 28.4 amps. Exhaust temp 31deg alternator rose to 44 now back to 39deg. One thing I have learnt is that the alternator has to spin at a high speed or won't cool properly. Still intend to fit a blower to it running off a thermal switch. I don't think this setup is really beyond most people who would be able to swap a starter motor or do an oil change? I wish yanmar produced big end pulleys with the provision for 2 belts and unfortunately I have never heard of any after market kit that bolts onto the existing fly wheel, the whole thing needs to be replaced. However, seems to work so long as the system is given a good charge up before running the anchor windlass and even then, don't run it continuously but in short runs. Heat gets to 55deg c when pulling up the pic!
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#13 lateral

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Posted 23 April 2019 - 09:21 AM

From what I understand:

Current is the only indicator of charge acceptance/ SOC whilst charging.

Bulk = increasing voltage, constant current, Absorb= constant voltage Vset decreasing current. Bulk is usually over quickly.

Time at bulk to Vset  only indicates how flat your batteries were.

240Ahr batteries at 0.01C indicator means a tail current of 2.4A for 100%.( Probably < 0.01C to holy grail!)

How long is it going to take to get your acceptance to that rate?

Otherwise you are doing a partial soc charging.

Which LA batteries don't like.

Correct me if I'm wrong.


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#14 Ladyhawk

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Posted 23 April 2019 - 09:55 AM

That's what I understand as well, less than 100% charging causes sulfation in FLA's. The most common reason for the premature destruction of FLA's on a boat.


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#15 Dtwo

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Posted 23 April 2019 - 10:17 AM

I wish yanmar produced big end pulleys with the provision for 2 belts and unfortunately I have never heard of any after market kit that bolts onto the existing fly wheel, the whole thing needs to be replaced. 

 

I would imagine that Yanmar would not be keen to put that much load on the front end of the crank. Unless the engine is designed to take that load, it isn't going to last long if you start swinging on the front of it.


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#16 Knot Me... maybe

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Posted 23 April 2019 - 10:36 AM

Govt Depts are very inefficient and are always looking for ways to get more money in to cover the cost of those inefficiencies. This thread clearly shows many boats mirror Govt Depts in being horrendously inefficient and are being run on the 'must have more' theory. 

 

Why not put the same effort into looking at savings and efficiencies, that is where the biggest gains will be found.


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#17 Bad Kitty

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Posted 23 April 2019 - 11:29 AM

This was all very amusing till you threaten my expresso machine KM, bugger off!


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#18 Knot Me... maybe

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Posted 23 April 2019 - 12:16 PM

This was all very amusing till you threaten my expresso machine KM, bugger off!

:D  Your machine is quite safe, coffee is an life essential so you're OK..... sort of.

While the coffee machine is in the bearable zone, just, it is just as easy to make quality coffee without chewing amps.

 

Is it a 12V or off a genny?


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#19 Bad Kitty

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Posted 23 April 2019 - 01:27 PM

240, but the inverter runs it happily.
Li Ion batteries have made a big difference to the boats usability.
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#20 Island Time

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Posted 23 April 2019 - 02:28 PM

This is what Balmar says about belt sizing;

 

"Ensure that the belt or belts driving the alternator are capable of handling the alternator’s horsepower load. As a rule, a single 3/8" belt is capable of supporting up to 80 amps@12 volts, and a single 1/2" belt can support 100-amp@12-volts. Dual belts will typically support alternator outputs of up to 300+ amps/12 volts. Driving an alternator on an undersized belt will substantially increase the risk of belt slippage and premature belt failure. All 24-volt Balmar alternators require a minimum of dual 1/2” belts for optimal performance. Balmar offers a wide selection of AltMount serpentine pulley kits for marine diesel engines. Visit the Balmar website for more information and application charts"

 

Not far from what I said before


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