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Twin WS500 install high voltage and not syncing.

So I ran the boat for the first time with the new setup, and have a few issues I need some guidance resolving.

Twin WS500’s running the 80A stock Denso Alternators on Yanmar 6LPs.

I have LTO lithium batteries, so I only have the bulk and float modes programmed everything else set to zeros.  Target voltage is 15V and it seems the batteries are getting there but with the batteries close to 15V my engine (alternator?) voltage got as high as 16.1v at one point on the master Alternator, the slave was lower at 15.4v.  Running at 2800 RPM.

So is this normal or is it a problem?  why are both alternators not putting out the same voltage?

The batteries can handle 16.2v and maybe a bit more, but some of the electronics, like my very expensive Wetsounds amps cannot handle anything over 15.6v.

Also when the WS500 is connected to the NMEA network it is causing my engine interfaces to shutdown NEMA output, and also my Garmin autopilot display and two GMI20 displays also shut down.  It might be an instancing issue and I plan to test that when next at the boat.

The Garmin “unit voltage” at 14.6 should be battery voltage of 14.9-15.0, the Garmin power cable has quite a bit of voltage drop because of the tiny power wires they used.



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When both WS500s are connected together via CANBus they will "sync" and basically treat your system as one big alternator.  This means that both alternator fields will be driven to the same output.  You can verify that the WS500s are in sync mode by the LED indicators status on the front of the WS500 case.  See excerpt below.

If they are synced and you are still experiencing a variance between the 2 units it could be a couple of things

  • lead lengths
  • alternator temperatures and manufacturing variations
  • length of runs to the batteries

If they are not synced you will need to set the addresses and configuration to get them to talk to each other.  The manuals can be found here:


Here is an excerpt from the WS500 user manual for reference


In applications where the WS500 is taking commands from a BMS or from another WS500 alternator
regulator, such as a twin engine application, where two alternators are being used to charge the
same battery bank, the WS500 may be placed in a sync (or slave) mode, where its operation is
being guided by another device. When the regulator defers to another in this mode, it will indicate
that it acting as a slave by flashing yellowish orange on the LED

Hi Rick,

The leads to the alternator, basically just the field wire, are different by 36" or so. All the positive and negative leads are landed in the same place.  The positive and negative cables from the engines are also about the same.

You didn't say why the alternator voltage could be so much higher than the set point.

I will double check for the orange light but pretty sure it was on, the master has the priority set to 100 the slave to 70.

I had sent you a couple of emails also but figured you might be at the Newport show or out of town or something.



And as your LTO batteries run such a high voltage I might consider a B2B converter on your important electronics.