sasko1980
New Member
Hi,
I have a LR 155-20 Hitachi alternator, and there are some doubts how to connect L and R terminals (Tshape connector).
Alternator is N-type , meaning "negative earth"
BAT + = goes to the battery (+)
E = goes to ground (earth), battery (-)
L = stands for LAMP connection
R = sense
In Yanmar service manuals sheme(pic1.jpg) for B-type panel the L is connected to LAMP ( 12v 3W) and to ignition switch.
In the electrical meaning "L" goes to the +12V.
For the R , is connected also from alternator to the ignition switch.
In the electrical meaning "R" goes to the +12V.

In some posts from other users and other forums they say that the R shuold be connnected directly to the battery(+) to sense the batterys voltage and to adjust the internal regulator. In simple words : when the battery voltage is low there is need to charge from alternator, and when it reaches the full battery voltage the charging is stopped ?? Is this correct?
If all this is correct, then you could connect the R wire from the alternator to a battery switch common terminal ( Perko, Seadog).
When you select the desired battery , for example, BAT1, the alternator would sense thru R wire the batterys voltage.
The same is with switch on battery BAT2.
For BOTH connection it will sense the average volts from the two batteries.
NEVER CHANGE THE BATTERY SWITH TO OFF WHEN THE MOTOR ( ALTERNATOR) RUNNING!
If you wish I could upload a sheme for connection.
My problem/question is :
The alternators manual for Hitachi LR155-20 says that the LAMP for the L connection should be 12v, 3 Watts.
On the boats panel there are 3 led diodes. Red led diode is for alternator's Charge lamp.
Is diode and its elelctric circle capable for exiting the alternator, or it has to be a 12v 3W lamp(bulb) to work ????
Is there some resistor involved in led diode circle ???
On my boat there is nothing connected to the (T shape) L and R terminals, the T shape connector is missing.
So I need a good advice to connect those L and R terminals. I would't want to burn the alternator.
If anyone who has a Hitachi LR 155-20 connected, and working, could help resolve the doubt???
P.S. If there is a need to post some more info , please be open to ask.
BR Sasko
I have a LR 155-20 Hitachi alternator, and there are some doubts how to connect L and R terminals (Tshape connector).
Alternator is N-type , meaning "negative earth"
BAT + = goes to the battery (+)
E = goes to ground (earth), battery (-)
L = stands for LAMP connection
R = sense
In Yanmar service manuals sheme(pic1.jpg) for B-type panel the L is connected to LAMP ( 12v 3W) and to ignition switch.
In the electrical meaning "L" goes to the +12V.
For the R , is connected also from alternator to the ignition switch.
In the electrical meaning "R" goes to the +12V.

In some posts from other users and other forums they say that the R shuold be connnected directly to the battery(+) to sense the batterys voltage and to adjust the internal regulator. In simple words : when the battery voltage is low there is need to charge from alternator, and when it reaches the full battery voltage the charging is stopped ?? Is this correct?
If all this is correct, then you could connect the R wire from the alternator to a battery switch common terminal ( Perko, Seadog).
When you select the desired battery , for example, BAT1, the alternator would sense thru R wire the batterys voltage.
The same is with switch on battery BAT2.
For BOTH connection it will sense the average volts from the two batteries.
NEVER CHANGE THE BATTERY SWITH TO OFF WHEN THE MOTOR ( ALTERNATOR) RUNNING!
If you wish I could upload a sheme for connection.
My problem/question is :
The alternators manual for Hitachi LR155-20 says that the LAMP for the L connection should be 12v, 3 Watts.
On the boats panel there are 3 led diodes. Red led diode is for alternator's Charge lamp.
Is diode and its elelctric circle capable for exiting the alternator, or it has to be a 12v 3W lamp(bulb) to work ????
Is there some resistor involved in led diode circle ???
On my boat there is nothing connected to the (T shape) L and R terminals, the T shape connector is missing.
So I need a good advice to connect those L and R terminals. I would't want to burn the alternator.
If anyone who has a Hitachi LR 155-20 connected, and working, could help resolve the doubt???
P.S. If there is a need to post some more info , please be open to ask.
BR Sasko