Yanmar 44HP Hitachi alternator sensing voltage question

[Goudurix]

After premature death of my Mastervolt AGM house bank (2 x 90Ah parallel) I will replace with Deka gel batteries (yes I read a lot of the posts on flooded-agm-gel) since last winter I moved the house bank from the engine compartment to a cabin location and I don't want any acid leaks nor H2 gasses in the cabin.

I started thinking about the premature death of those 2 AGM's since I thought I cared for them well (mastervolt IvoSmart 35 Amp dock charger set to AGM) since my usual pattern is daytrips and dock recharge every night and only 1 longer cruising trip with both dock charging or alternator charging on anchor.

I started to suspect the alternator charging...

Setup: 4 years ago I threw out the diode splitter and went to 1 cranking battery (flooded) and the 2 parallel AGM's as house bank. I connected the charging wires from the alternator directly to the house bank.
Balmar echo charger channels a charge to the cranking battery whenever (charging) voltage of the house bank is >13V.

My questions:
The standard Hitachi alternator (70 Amp) (was workshop tested) is still wired via the original harness.
I thought it was fully internally sensed (machine sensed) but looking at this thread:

What's the R connection for on a Yanmar / Hitachi alternator?

It seems it does have an external sensing wire connection and I now possibly have a dubious situation:

- alternator regulator charging the house bank
- sensing wire still connected to the ignition switch and hence with the cranking battery (apparently before removing the diode splitter it did sense cranking battery voltage without any voltage drop?)

I guess that in this case, with cranking battery at full voltage, I am charging my house bank at too high a voltage hence "boiling" the AGM's?

Since I want to avoid doing the same with the new gel house bank...

Thanks for your advice,

Jan

[bauer965]

Yes, that voltage sense connection is there just for that purpose.
In some wiring configs, you don't necessarily need it, in others, which is similar to mine, you do.
You want to directly sense the battery you are directly charging (in your case, your house). Your echo-thing will take care of the start battery.

[Goudurix]

http://i50.photobucket.com/albums/f3...iregulator.jpg

Looking at above diagram, I guess in my situation (wanting to sense voltage at the house bank for alternator charging, and with the engine contact switch still harnessed to the cranking battery) I would have to switch a relay with the contact key switch, which then switches both the charging lamp and the sensing voltage point to the house bank +?

Please techies...your advice?

Jan

[Goudurix]

Really really hoping to "lure" MainSail to answer....

I am really in doubt. Given the fact that I want to charge (and keep happiliy alive) gel batteries I guess I will need to install and externally regulated altrnated with smart charger (like Balmar)

Jan

[Goudurix]

No further advice received.

I took action and wired to contacct switch to a 12V relay, which then switches the house battery + to the alternators sense wire ("R") and also the charge lamp.
In this way the alternator's regulator senses the voltage of the house bank I am charging and the Charge warning lamp circuit can still function normally, and I keep house bank and cranking battery + completely separated.

This works (of course). I get 14.2 V out of the alternator.

Now I have to check what happens on longer motoring trips, since I also replaced the dead AGM's by 2 Deka 100Ah gels batteries, and I don't want to overcharge these on coninuous 14.2 V.

In the end I guess I would better install ASAP a Balmar alternator withsmart external regulator to optimally treat the house bank gels.

Jan

[Maine Sail]

Keep in mind that these alternators have a regulator that internally temp compensates the absorption voltage downward as the alternator heats up. This can lead to chronic undercharging especially with banks that demand lots of current like AGM and GEL that cause the alts to run hot...

I have one Hitachi 60A alt on a customers boat that I can measure pumping out 65-67A when cold, at not much over fast idle. The voltage climbs towards 14.3V. This is pumping out in excess of its face value rating when cold.

However, as this alt heats up, the absorption voltage quickly begins to get reduced to the point where the batteries are seeing less than float voltage and the alt is putting peanuts into the bank due to the lowered target voltage. This internal temp compensation is a self protective feature to the alt but a bank destroying feature to the batteries. It can lead to chronic under charging if you have no other means.

For charging large cycling banks these alternators are often woefully insufficient due to this internal temp compensation feature. They are ideally designed to recharge a battery from a starting load not to charge cycling banks.

With an external regulator it would cut the field current/voltage to cool the alt but the target absorption voltage would remain the same. With these Hitachi alts the voltage gets reduced and less voltage at the battery means less accepted current to the battery bank. Still cools the alt but goes about it by reducing the voltage the regulator regulates rather than reducing the field or current output. With a reduced voltage the alt pumps out less current the alt can then cool. Problem is you are essentially trying to charge a large bank of batteries on a float voltage.

Very often this little blurb in the Yanmar alt specs is over looked:

LR160-741

Regulated Voltage 14.4 +/- 0.3V (at 20°C, voltage gradient, -0.01V/1°C)


This means that at 20°C or 68°F the regulator is operating at the target voltage of 14.4V. Great! But here's the rub. The alt WILL NOT stay at 20°C/68°F for more than a few seconds after start up if actually trying to charge batteries.....


These internal regs begin reducing alternator voltage from 14.4V by -0.01V for every 1°C change in alternator temperature above 20°C/68°F. It took me a while to get this confirmed, calls to Yanmar resulted in NADA, and finally, some calls to Hitachi, answered my question and confirmed this spec.

If not careful one could mistake the low battery terminal voltage for voltage drop but when you measure the back of the alt, and it is only at 13.4V, as I have many times, that answers it...

It is easy to see how with an alt temp of 190°F the alternator is now pumping out 1.22V less than 14.4V or just 13.18V if we go by the specs...... I do find the specs on these alts to be pretty sloppy..... 14.4V +/- 0.3V for example means 14.1V (-0.3V) to 14.7V (+0.3V) is where your initial 20°C/68°F target voltage could be..

[Goudurix]

Hi Maine Sails,

thanks for your detailed answer.

Mine is the LR-180-03 Hitachi rated at 80W though I never see it pump out more than 12-18 Amps on the charge amp monitor...but this monitor is probably faulty it is the original analog amp meter in the electric panel and I have to tap it to make it work "a bit".
Now that I've invested in the expensive gels i'd better install a good trustworthy battery monitor system.

Indeed last night after finishing the gel battery install and rewiring the alternator, I ran the engine for 5 minutes and measured 14.3 V both at the house bank and at the sensing voltage input.

I remember when checking occasionally in the past, with a "hot" engine, to see often voltages like 13.8-13.9V. The engine room is cooled however with an engine compartment extractor/blower.

For the moment I am rather scared to overcharge the gel's if 14.3V on long engine runs but evenso it could be true that when "on the hook" (this is only few times/year) I will undercharge a well depleted house bank with the temp compensation.

Given your remarks on the temp compensation of the Hitachi, and the fact that I would better use a "smart" externally regulated alternator, I suppose it is better to replace the Hitachi by something like Balmar 60-type alternator and one of their external charge regulators ASAP?

By coincidence tonight we will do a motoring trip to go and watch a fireworks festival taking place on the beach so I'll use the occasion to check de alternator charge voltages.

Thanks,

Jan

[Goudurix]

Mainsail,

how can I simply shut down the alternator without damaging it, with a running engine?

E.g. when I have to motor for a long time, house bank is full and I would like to avoid overcharging the gel house bank?

=> simply by interrupting the anternator to battery positive charge wire?
=> by putting the sense wire R to ground?
=> by leaving the sensing wire R open (I thought this is a no-go...?)

Jan

[pbiJim]

Originally Posted by Goudurix

Mainsail,

how can I simply shut down the alternator without damaging it, with a running engine?

E.g. when I have to motor for a long time, house bank is full and I would like to avoid overcharging the gel house bank?

=> simply by interrupting the anternator to battery positive charge wire?
=> by putting the sense wire R to ground?
=> by leaving the sensing wire R open (I thought this is a no-go...?)

Jan

I don't know that specific alternator, but generally speaking on most alternators:
#1 will destroy the regulator.
#2 will probably make the alternator put out full power available.
#3 response will vary with regulator type.

[Goudurix]

Hi PbiJim,

looking at the typical diagram of an internally regulated alternator I guess it would be opening the filed wire connection so that the rotor does not get energized (neither at startup by the cranking battery nor by the alternators own staor current once that kicks in).

But that is internal in the alternator it would mean opening up the alternator, if my assumption here is right.

Jan

[smac999]

you could shut the engine off, interrupt the pos between alt and batteries. and restart engine. just don't disconnect while engine running.

3 may or may not work. it might work with shutting engine off, disconnecting, and restarting. if you just pull it with engine running the alt is already engergized and may just continue working.

[Goudurix]

Smac999,

will the field rotor not still be energized upon restart even when disconnecting the BAT connection during engine standstill?

Jan

[Maine Sail]

Originally Posted by Goudurix

Smac999,

will the field rotor not still be energized upon restart even when disconnecting the BAT connection during engine standstill?

Jan

It will but with no load there is little possibility to make the diodes go pop....


The best course of action is to either interrupt the B+ to the regulator. If that is not easy or doable due to it being internally regulated then interrupting the field circuit is the next best option.

Interrupting B+ of the regulator shuts the alternator off..

Interrupting B+ of the alternator, when loaded, can blow the diodes.

[Goudurix]

Maine Sail,

2 questions:

1) could you relate that to the diagram of the Hitachi alternator:

http://i50.photobucket.com/albums/f3...iregulator.jpg

BAT+ comes directly out of the diodes

BAT+ to the regulator is both R (the voltage sensing wire) and L which is in the charge lamp circuit. Both are switched in with the key switch but I thought that is was also a NO-GO blowing the alternator to switch the key swith to OFF (on top when doing so the alarm trial sound goes off).

Of course I might switch out L and R voltage somewhere else independent of the key start switch.

2) if the above is correct,I guess I still have to switch it off with the engine NOT running, then restart the engine?

Thanks for your reply.

Jan