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Discussion Starter · #1 ·
Was wondering if my 28 year old Hitachi 35 Amp Alternator
(LR 135-105) would be ok for my soon to be replaced
batteries...
background: Yanmar 3 GM motor with 1 bank of 2 Group 27 batteries (about 200 amp/hrs)...soon to be replaced with 2 group 31 batteries (210- 230 amp/hrs)
batteries have usually lasted 6-7 years ...always on a mooring, never any shorepower, so it's just the
alt. and a small solar panel.
Thinking the alt. has been a little on the light side
but I do not use much power and have never had a
power problem.
Question, is the technolgy of the old alt. (internally regulated and seems to be functionally ok...thinking charging at 14.plus volts) been bypassed by something
new, better regulating charging of the batteries?
Thanks in advance,
Hugo
 

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Yes, there are several more sophisticated external regulators which could maximize the charging capacity of your alternator. However, they are expensive and, as you seem to depend on solar anyway, I'd add some solar capacity and a good little solar regulator. That would be less expensive and would ensure your new grp 31 batteries stay topped up.

Bill
 

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Hugo, the old alternator would work but the new batteries should be able to absorb current at about a 50A rate or better. So any alternator that can't supply 50A for extended periods, won't be charging them efficiently.

That means you'd get a better return on your money (probably 1/2 the engine time needed) by putting in a 75A or better alternator, preferably with an external regulator, so the combination would charge efficiently. But at a minimum, I'd increase the alternator size to feed those new batteries.

A good solar panel and charge controller (three stage) would really keep them happy.
 

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It depends on the new battery type you're getting. Are they flooded/wet cell or AGM? Thew new AGMs can soak a ridiculous amount of current during their bulk absorption phase.....to the point where your 35AMP alternator will burn out. WHile your alternator is rated at 35 amps, its not 35 amps continuous! THats peak output.
 

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Hugo

Your soon to be bank of group 31 batteries won't accept much current. If flooded only 40 or 45 amps. Even if they are Agm's they will only accept more current for a short while. Engine charging without going anywhere is terribly inefficient anyway. To improve measurably - upgrade the alt to a new one - say $200 to $600 and a good external reg - say Balmar MC-614 @ around $400 you have spent a lot of money for those times when motoring and to charge what is a pretty small battery bank. Now if you were cruising extensively and had a battery bank of 4 to 6 golf carts for a bank size of 440 to 660 AH it would be more worthwhile.

I agree with Bill - more solar with a good MPPT controller will return more for less outlay.
 

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Discussion Starter · #6 ·
Thank you all for your (always) good input/insight.
Batteries are/will be lead acid.
Was thinking about the $700.-1000. needed to upgrade
the alt/reg, but not in the cards this year, that is why I
posed the question.
For now will put into service larger solar panel I already have
don't remember size, have to check, but have to buy another
controller..3 stage sounds good as thinking my current controller
not up for the job ( MPPT but think not 3 stage, more checking).
Thought I would try Mainesail's suggestion and buy
2 US Battery #31 DCXC..but was quoted a "wholesale price" thru
business from distributor for $179. each 130 a/hr...Guess I'll be checking into Sam's Club Duracell (East. Penn.) D/C batteries. 105 a/hr $95.
Thank you all again,
Hugo
 

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Hugo,

If you have room for them, two 6-volt golf-cart batteries in series would be preferable to two 12-volt batteries in parallel. Virtually no 12-volt batteries are true deep cycle. The golf-cart batteries have thicker plates, are more robust and forgiving and have more AH capacity.

Two golf-cart batteries would give you 225-240AH capacity.

I recently found the very excellent U.S.-made Crown 235AH industrial batteries (white with red top) for under $100 each. Replaced the 8-year old T-105s in my boat. So far, so good.

Bill
 
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