Hitachi Alternator

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Dave_Rolfe

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I have a Hitachi LR155 Alternator fitted to my Yanmar GM20 engine. I need to identify which terminal is the B+ terminal to connect a cable to. There are two main terninals on the back of the alternator. One terminal has a single red wire going to, this one has BAT cast in the alternator body next to it.The other main terminal has two wires going to it, one thick and one thin with the thick one being black. There is a third smaller terminal with a cable attached by a self tapping screw.

Which is the B+ terminal please and what are the other two. Can I connect direct to the B+ terminal or should I connect elsewhere in the loom.

Numbers on the alternator plate read LR155 -20B 129772-77200 12V 55A Hitachi
As always, thank you for your advice.
 
The BAT terminal is the same as B+. The second main terminal is the negative terminal. The smaller third connection is just an earth, which will no doubt be connected to battery negative somewhere.
 
[ QUOTE ]
The smaller third connection is just an earth, which will no doubt be connected to battery negative somewhere.


[/ QUOTE ] I'd have suggested that was the warning light connection. No?
 
[ QUOTE ]
I'd have suggested that was the warning light connection. No?

[/ QUOTE ]No, Vic, the warning light connection is one of the spade terminals.
 
Ah so there are other terminals not mentioned by the OP!

Not one for a tachometer as well is there?

I wonder why there is a thin wire on the negative as well as the main negative connection.
Why should there be a separate earth connection?
 
On the standard 55 amp alternator on the 2GM20,there are normally 2 screw terminals, BAT is +ve, E -ve, and 2 spade terminals, the inner one L to the charge lamp, and the outer one R, to the other side of the charge lamp. There is no tacho. terminal, ( R goes to the internal regulator.)
 
Thanks for the above. Any suggestions as to the capacity of the existing standard cabling to carry the alternator output. I am installing a Sterling Alternator to Battery charger and someone has suggested that the existing cabling will not be up to carrying the charge.
 
[ QUOTE ]
someone has suggested that the existing cabling will not be up to carrying the charge.

[/ QUOTE ]

What charge are you expecting ?

Brian
 
It will be carrying the max 55a charge from the alternator to the Sterling AB1290. From the Sterling unit there are large cables (2awg) to the batteries etc.
 
My understanding (and I am no electical expert at all) is that the voltage will be much higher together with the an increase in current. All I am doing is following the installation instructions but am now concerned (after what a friend said)as to whether the existing cables from the alternator to (at present) the battery switch will be up to it. Should I put heavier cable in just to be on the safe side and if so would it be best to use one cable from the B+ terminal on the alternator direct to the Sterling unit, bypassing the wiring loom connector plugs etc.or use an additional cable in this way to double up the existing cabling (I hope that makes sense)
 
RTFM! If you look at the instructions for your Alternator to Battery Charger, you'll find there's a chart giving cable sizes, according to the cable run. Follow that. If still in doubt over size, go one size larger.

Note that Mr Sterling confusingly talks about cable sizes in "mm sq", but what he means is "sq mm". Although he also says you can use two or more smaller cables, you'd be better going for single large cables - fewer potential terminal problems.
 
This cable size chart may be of interest.

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

On 12 volt systems the main consideration is usually that of volts drop on long runs. 3% is the normally accepted maximum and is the figure on which the above table is based. That is why the wiring on a boat is often much heavier than domestic wiring would be for the same current.

Looking at the chart it would seem that 6AWG may suffice if the run is short, while 4AWG will be adequate unless you have an extra ordinarily long cable run.
There is a link to a AWG to cross sectional area and diameter conversion table.

FWIW Maplin sell 4AWG cable, which they describe as "Car battery power cable", by the ½ metre. They rate it at maximum of 70A. (Cat nos BZ91Y for red and CK17T for black)

As pvb says beware of misleading terminology with cable sizes.
Cross sectional area should be in square millimetres (sq mm) for which the correct abbreviation is mm². In speech that gives rise to the expression "millimetres squared". That in turn gets abbreviated to mm sq, as is done by Charles Sterling who really should know better. However you'd be pretty dumb IMHO to translate that into millimetres square .... at least unless you are dealing with pretty heavy square conductors!

EDIT
The cable sizes from the AB1290 instructions:

WHAT CABLE TO USE IN sq mm

A charger
or inverter
up to cable
run distance .........0-1.5 mtr ...................1.5 - 4 mtr

0-25 amps ............6 mm sq ...................10 mm sq
25-45 amps .........16 mm sq ...................25 mm sq
45-85 amps .........25 mm sq ...................35 mm sq
85-125 amps .......35 mm sq ...................50 mm sq
125- 180 amps .....50 mm sq ...................70 mm sq
180-330 amps ......70 mm sq ...................90 mm sq
 
I suspect, Vic, that your advice is confusing and will conflict with Sterling's instructions. The installation instructions contain clear cable size guidelines, and these appear to be much more generous than would be the case with your 3% volt drop criterion. Also, the instructions say "Choose a cable size that can carry at least twice as much current than required. For example, if you have a 70A alternator, then use a 140A cable." I think the original poster will be better following the Sterling instructions.
 
Yes the cable sizes in Sterlings instructions are a bit more generous than suggested by the table I found. That's a useful table to make a note of though.

But are you suggesting that the recommendation in the text of Sterling's instructions means that one should double up on the current in his own table. That would be confusing and would mean using 0, 00 or even 000 AWG depending on cable run. I'd take the table at face value I think.

Another factor not mentioned is whether cables are suspended in free air or buried in a harness. I've seen some info on that but can't remember where.

I know what I'd do. I'd buy that 4awg cable from Maplin provided the cable run was not excessive.
 
[ QUOTE ]
My understanding (and I am no electical expert at all) is that the voltage will be much higher together with the an increase in current.

[/ QUOTE ]

If that was true, it would answer Global warning, free energy. You would not need to run the engine, just connect the battery to the input, and the output to the battery.

Has Sterling found out how to take say 50 amp at 13.6 volt, and give you 60 amp at 14.6 volt ??

Charge amps out should be less than than charge amps in ?

So cable is based on volt drop to extra length.

Brian
 
[ QUOTE ]
I know what I'd do. I'd buy that 4awg cable from Maplin provided the cable run was not excessive.

[/ QUOTE ]Well, AWG4 is about 21 sq mm. The original poster has a 55A alternator, and assuming a cable run of a couple of metres, Sterling's chart would suggest 35 sq mm.

It looks like Sterling's chart is based on a max 1.5% volt drop.
 
Very possibly. 3% of 12 is 0.36 so I guess you would not want to be wasting that much while splashing out on a device to boost everything to the max. Perhaps also worth connecting up its battery sensing facility.!

I had not realised there was a table of cable sizes in the instructions despite having looked at them for some reason once before.

Really a case of as you say RTFM (read the full manual ... . what did you think it meant /forums/images/graemlins/shocked.gif)

Does this gadget really do what it claims. It appears that it is claimed to do what Halcyon says it cannot. There is no connection to the field windings so the alternator is purely under the control of its own regulator yet this device is apparently boosting volts and current at the output. I must be missing something I suppose.

Looked again at the spec of the cable in Maplins catalogue with my glasses on. Not suitable for this application anyway.

I suppose one ought to be looking at tinned cable into the bargain.

Glad I manage with a 60Ah leisure battery and a small solar panel!
 
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