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G12-150 with v3 diode probs

PostPosted: Wed Oct 07, 2009 2:30 pm
by olly12383
We've had an issue on the Genie 12V-150A where the diodes have burnt out.
When this was discovered, the circuit breaker on the genny output was open.

The owner bought the machine from you about 5 years ago but it has been in storage
since then. It did work and I have personally witnessed it making 80-120A for about 4 hours.

Obviously no output load is not good for the alternator, but I was under the
impression the regulator would not allow damage to be done in this way? It
is wired in such a way that the battery sense is on the battery side of the
breaker. The reg is a V3.

Do you think that damage would be done to the alternator if the breaker
tripped, or is it possible that a diode failure could then cause the trip to

I have derated the output to 110-120A using the current limit on the reg and
the breaker is a bussman (blue sea) 150A.
We found that without current limit (full output around 180-190A) the diesel was
stalled by the alt. (but the breaker did not trip - if you look at the trip curves for these breakers they'll take about a minute to trip at 125% overload)

Incidentally, is there any reason the generator can not be run
simultaneously with the main engine which also charges the same bank (via a
split charge relay)?
I know it can fool some regulators but I was not aware that the V3 would be.

In which case How much is a new diode pack for the 150 alternator? What voltage are they
rated to?

The customer is keen to go for external diodes.
Is it possible to convert this alternator, and what would be required to do

Also he's keen to install some sort of avalanche diode across the alt output to prevent high
voltages killing the diodes again. Is this something you've done before?
Can you recommend something for this?

Thanks in advance for your help.


Re: G12-150 with v3 diode probs

PostPosted: Thu Oct 08, 2009 3:04 pm
by Coulomb
The unit was not wired according to the wiring diagram. We never put a switch, (or circuit breaker) between the output of the alternator and battery because if the switch opens when the alternator is running the diodes will almost alway blow. A snubber across the alternator terminals may prevent diode failure, but nothing is guaranteed. You can find snubbers here:

See this URL:

Keep in mind that when battery voltage is low, and the alternator is still cool it can produce 190 Amps without stalling the engine.

Get rid of the breaker and follow the wiring diagram.

You can also find the Dual Alternator Controller at the above URL. That is required to use the SARV3 on two engines.

Alternator diodes are rated at 200V. A replacement set is $169.00.

We install water cooled diodes with Genies that go into the sound enclosure because it does help cooling the enclosure. Modifying the alternator is non-trivial and requires 3 custom spacers that we make along with the water cooling assembly. You can order a Genie alternator with the remote diodes for $1359.00.

Re: G12-150 with v3 diode probs

PostPosted: Sun Oct 18, 2009 10:42 am
by olly12383
Can we buy the water cooling kit without the alternator.


Re: G12-150 with v3 diode probs

PostPosted: Mon Oct 19, 2009 11:10 am
by Coulomb
$499.00. No instructions on how to modify the alternator are included.

Re: G12-150 with v3 diode probs

PostPosted: Tue Oct 27, 2009 2:17 pm
by olly12383
Hi, are the instructions available online and/or is this easy to work out?
Does this involve installing spacers and are there AC output terminals on this modeal of alternator?
Thanks for your help.


Re: G12-150 with v3 diode probs

PostPosted: Tue Oct 27, 2009 11:46 pm
by Coulomb
There are no instructions online.

Yes spacers are required.

Yes, the alternator has AC taps.