Hitachi alternator

[steffen]

HI folks,
I have a Yanmar 3GM with a Hitachi LR135-74 alternator. I load three batteries (2 * 105Ah houdehold, 1 * 80 Ah starting) through a diode bridge loosing 0,7 volts in the process.
Is there anybody who knows how to modify this specific alternator to accept a compensation diode in order to increase the outpu voltage?

Happy sailings, Steffen

 

[Chris_Stannard]

Hi Steffan,

I have the same problem, and am not yet clear on the solution. I was going to fit a smart charger. My boat currently has a relay which closes to parallel the charger when the alternator is running.
It was suggested that I should put a diode in circuit with the starter battery to stop it discharging into the household batteries if they became flat, and that this would protect the starter battery from being overcharged. The reason that ths protection is necessary is that the engine starts so easily that the starter battery is almost always fully charged anyway.
It was also stated that if I fitted a smart alternator regulator, it should have temperature sensors on the batteries and alternator to prevent them overheating.

It all makes sense but I have not got round to doing it yet. I looked at all the wiring, and thought I might need an electrician.

Hope this helps

Chris Stannard

 

[halcyon]

Chris

You have lost me a bit,

If you have a relay and it is working, it will isolate the engine battery from from domestic, thus no need for the diodes.
When you parallel the batteries, the charge current will take the least line of resistance, normally the domestic battery, until it's charge level comes up to the engine battery, at this point they will share the charge, depending on what the battery will take.
Fitting a diode will not stop overcharging the engine battery, unless you have a faulty regulator.
If your alternator is regulating around 14.5 volt, you are not going to see dramatic defferance, except to your wallat.


Brian

 

[jfkal]

I am using the same. I do not think that you can do any modifications. I got the Sterling smart charger. Works perfectly. I am getting the full rated AMP's on a discharged battery and a perfect 14.4 volts directly at the batteries. I am using diodes as well. Before I got only miserable 20 Amps charge and the batteries never got fully charged. Modification needed on Hitachi are simple. Tell them the type of alt you have since there is a seperate set of instructions for the Hitachi.

Have fun.

 

[steffen]

Hi Chris,
I am an electric engineer by origin. Thought about smart regulators and the like but decide not yet in view of the cost involved.
Most alternator can be changed simply but Hitachi hasd a build-in regulator and needs to be operated upon.
If i find something alsewhere i let you know.

Happy sailing, Steffen

 

[steffen]

Who is "them"? I tried to find an email entrance into Hitachi but did not succeed sofar.
BTW, i too have a Sterling smart changer, works a treat, doesnt need diodes since it has three plusses.
Happy sailing, Steffen

 

[oldharry]

Diodes in the charging circuit will always cause a degree of voltage drop, so reducing the rate of charge, usually not enough to matter. Smart chargers are the answer if it is a problem.

A relay will allow full charging voltage, but if one battery is substabtially down, it will draw on the other(s) until the charges balance out - not desireable for the starting battery!

The Starting battery should ALWAYS have priority, and any isolating device - whether diode or relay - should feed the domestic batteries, with the alternator directly connected to the starter battery.

 

[jfkal]

Hmm guess you mean the Sterling mains-charge,r which I use as well. The smart alternator regulator just "controls" the alt but the charging wiring is unmodified hence you still want to retain the diodes.
With "them" I meant Sterling. My apologies for not having been clearer.

 

[charles_reed]

I had an Hitachi alternator, coupled to an Adverc smart regulator, through splitting diodes. With the early version of the Adverc I originally had I had to bypass the internal regulator (no longer a problem on the latest mark).

The Hitachi, after many years of excellent service, died of overwork and has been replaced with a somewhat more rugged Lucas 90 amp marine alternator.

With my current set-up I get a peak 14.3v into the batteries from the alternator and slightly less from the wind generator/solar panel.

I'd suggest the cheapest and most direct and simple answer is to fit a smart regulator - I'd suggest the Adverc from a service and cost point of view in preference to the Sterling or TWC.
Their tel no is (44)1902 380494, speak to Trevor or Brian (being engineers they're refreshingly free from salespeak).

By the way why have separate domestic and "starter" batteries - just fit a selector switch and rotate the "spare" for your insurance. Batteries last longer, you waste less space/weight and one can be refreshingly different from run-of-the-mill dumbos ;-)

 

[steffen]

Charles,
Tks for tips.
Ref. wy starter accu?
In fact i can use any accu for everthing; i have a rail setup with 3 separator switches and a 1-2-both switch.
I normally save one from domestic consumption so i always have a fully loaded one for starting or for VHF/GPS.