Hitachi alternator no output

[SailBelladonna]

We have a Hitachi LR155-20B which is not showing any voltage increase across the batteries with the engine running.

There are 6 leads coming from the alternator - two cables on the + stud, two cable on the earth terminal and two cables coming out the t-style connector. The t-style connector has a blue cable connected. The red cable looks like it has been cut. Should the red cable be connected and could this cause no output. The other alternator has this cable connected (it is a cat).

We have taken the alternator to a repair shop and the replaced the voltage regulator and bearings so believe it is not the alternator.

I have just wired in some lifepo4 batteries and in doing so removed a split charge diode - should the alternators be wired differently? It did trigger alarms on the engine control panel and removing the small brown wire (not the big battery wire) from the alternator +'ve solved the alarm.

[markcouz]

My blind stab is that the blue wire is rpm terminal and the red wire is field terminal which has at some point been cut intentionally to remove 2nd alt from service.

If correct you would need to investigate why this was done before reconnecting field wire.

If you are sure that a permanent load is connected to the output terminals then connect the red wire and measure if output returns.

If you power up the field without a load connected to the alt you will convert the alt to smoke.

Also before connecting test the red wire when engine switch on (harness side, not alt side) it should be 12+ if it is field wire.

[SailBelladonna]

I think you may well be correct. The original wiring had a single starter battery starting both engines. I changed the wiring so we have a starter battery in each hull. This may account for one of the alternators having the field wire cut, so that both alternators didn't feed a single starter battery? Is there are problems having two alternators work together? Looking at the wiring diagram the wire that has been cut says 'sense' - is that indicating it is the field wire.
Thank you for your response.

[Thumbs Up]

First off, there are no problems with two internally regulated alternators working together. Second, these are so cheap that there is no reason not to carry a spare. There is supposed to be a 3 watt charge indicator light on your panel. This light is wired to the L terminal of the alternator and to the switched positive of the ignition switch. If this lamp is burned out, not making contact or missing altogether your alternator will not charge. This lamp excites the field (also can be replaced with a resistor). Check your charge lamp, it is probably the problem. It must be an incandescent bulb (LED will not work).

[SailBelladonna]

Thanks - just checked the charge lamp and it turn on when I switch the ignition without starting the engine. But stays on when the engine starts. Anyone know what sense wire does?

[Thumbs Up]

Good to see that the charge lamp is working. I am assuming that you know not to disconnect the battery bank while the alternator is charging. This blows the diodes in the alternator. Could you have done this to the repaired alternator?

[markcouz]

The sense wire goes to the +ve terminal of battery bank that is being charged so that the alternator gets accurate info for voltage regulation.

[markcouz]

...Probably used for field exitation at the same time.

[Flod]

I had the exact same problem when switching to lifepo4 and removed the charge splitter. The alarm went crazy and the alt didn’t get ignited. I couldn’t figure out how to solve this so I put the charge splitter back and made it a part of the installation. Maybe not the most elegant solution but it works

[SailRN]

Originally Posted by Thumbs Up

Good to see that the charge lamp is working. I am assuming that you know not to disconnect the battery bank while the alternator is charging. This blows the diodes in the alternator. Could you have done this to the repaired alternator?

Lithium batteries typically have a Battery Management System (BMS) which do disconnect the batteries.


See

https://www.youtube.com/watch?v=jgoIocPgOug

And a good read: https://marinehowto.com/lifepo4-batteries-on-boats/


An excerpt:


The alternator for the Volvo MD2030 with 300 Amps lfp 14.6 max lasted a few hours. I believe BMS was switching on to off I to keep the lfp voltage to safe measure? Boat service replace alternator and it happens the second time? I now read your story on lfp and it explain to me why.”
Unfortunately the reader above learned the hard way. Ask yourself what happens when your alternator is in bulk charge, supplying all the current it can, and the internal BMS decides to “open circuit” or disconnect the battery from the boat? I’ll help out a bit here.
A) The alternator diodes, unless avalanche style, (rare in many existing marine alternators) but all Balmar alternators now use them, can be blown and the alternator can be rendered non-operable. Two years ago I did exactly this. Using the alternator test bench here at CMI the alternator was running at full bore charging an LFP battery. The “system” I set up had a .3A dummy load on, light bulb, to simulate a depth sounder. With the alternator running at full bore I disconnected the battery, just as an internal sealed BMS would do to protect the LFP cells. Poof went the alternator diodes and the light bulb! Worse yet the voltage transient I recorded on the “load bus” (think your navigation electronics) using a Fluke 289 was 87.2V. Ouch. Even if your alternator uses avalanche diodes, like Balmar’s do, the voltage at which they begin to protect the alternator is far too high for the vessels load bus equipment so you still need a way to protect against a load dump.

[SailBelladonna]

Originally Posted by Thumbs Up

Good to see that the charge lamp is working. I am assuming that you know not to disconnect the battery bank while the alternator is charging. This blows the diodes in the alternator. Could you have done this to the repaired alternator?

I have a sterling alternator protection device - but yes we have always kept the alternator + connected to the battery. I have got both alternators working but now have a constant alarm. Will post a picture.

[SailBelladonna]

Originally Posted by SailRN

Lithium batteries typically have a Battery Management System (BMS) which do disconnect the batteries.


See

And a good read: https://marinehowto.com/lifepo4-batteries-on-boats/


An excerpt:


The alternator for the Volvo MD2030 with 300 Amps lfp 14.6 max lasted a few hours. I believe BMS was switching on to off I to keep the lfp voltage to safe measure? Boat service replace alternator and it happens the second time? I now read your story on lfp and it explain to me why.”
Unfortunately the reader above learned the hard way. Ask yourself what happens when your alternator is in bulk charge, supplying all the current it can, and the internal BMS decides to “open circuit” or disconnect the battery from the boat? I’ll help out a bit here.
A) The alternator diodes, unless avalanche style, (rare in many existing marine alternators) but all Balmar alternators now use them, can be blown and the alternator can be rendered non-operable. Two years ago I did exactly this. Using the alternator test bench here at CMI the alternator was running at full bore charging an LFP battery. The “system” I set up had a .3A dummy load on, light bulb, to simulate a depth sounder. With the alternator running at full bore I disconnected the battery, just as an internal sealed BMS would do to protect the LFP cells. Poof went the alternator diodes and the light bulb! Worse yet the voltage transient I recorded on the “load bus” (think your navigation electronics) using a Fluke 289 was 87.2V. Ouch. Even if your alternator uses avalanche diodes, like Balmar’s do, the voltage at which they begin to protect the alternator is far too high for the vessels load bus equipment so you still need a way to protect against a load dump.

I have kept the lead acid batteries in the lifepo4 design to avoid this issue and installed a battery to battery charger so the 50Amp alternators do not run above 30A load. We have plenty of power and don't use the alternators, but they are good for backup.

[SailBelladonna]

Originally Posted by Flod

I had the exact same problem when switching to lifepo4 and removed the charge splitter. The alarm went crazy and the alt didn’t get ignited. I couldn’t figure out how to solve this so I put the charge splitter back and made it a part of the installation. Maybe not the most elegant solution but it works

Thanks - wanted to remove the split charge diode to remove points of failure, but as you suggest this may be a solution if I can't work it out with help on this forum.

[Wotname]

I can't help with the correct setup for lifepo4 batteries but I can tell you how Hitachi expects the alternator T style connector to be wired.

One wire goes to the charge light. This usually the blue (or blue/black) wire and from memory, it is vertical part of the 'T'. Its function is to provide initial excitation to the field. Once the alternator spins up and is providing an output, it becomes self exciting.

The other wire provides the sense voltage to the internal regulator. It is usually red/black (or sometimes red) and from memory, it is the 'top' of the 'T'. Often simply goes to key switch (ignition switch) positive.

See attached.

[SailBelladonna]

I have made some progress and now understand the wiring a bit more. Both alternators are working but we have a constant alarm on the control panel.

In the diagram attached our installation has the "R" cable cut. I understand this is connected internally via a 50ohm resistor anyway and the alternator works without it.

In the diagram below the "L" cable splits into two - one goes to the control panel and another to the "B+" terminal on the alternator - making it permanent live with the battery switch on. When I remove the cable between "L" and "B+" the alarm goes off (what a relief) but the alternator stops charging.



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