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REC and WS500 User Forum

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Tachometer shut off?

New installation of WS500 seems to be working well. Simple installation on a Jason 35' with a single alternator on a Beta28. Tachometer is driven by alternator.

When batteries are full the WS500 shuts down, as expected. But this also shuts down the tachometer, presumably because no current is being sent to the alternator field.

What is the best, or most practical, way to keep the tachometer working when the batteries are full? Is there a config setting that allows a very small but continuous current to the field?

Thanks, Randall. s/y Velic. Whangarei, NZ

If you tacho stops this means there are NO amps produced by the alternator.
The WS500 does do the best things for your battery, IF full stop charging.

In the standard lifepo4 profile when batteries are full the regulator goes into float mode.
In float mode, the regulator will keep the shunt at zero map.

As example:
If your load(navigation fridge etc) on board use 5amp.
The alternator will produce 5 amp, this 5 amps goes to your load.
zero amp goes to the battery.

If you tacho stops, try to switch on more load.

MORE than one charger in the system for example SOLAR?
If you have solar in your system, with higher voltage settings, your solar will give this 5 amp to your load.
This means the alternator gives 0 amp, this means NO tacho.
If this is the case, reprogram your solar, or switch off your solar.

The Issue with Solar and external alternator controllers I see with all brands external alternator controllers.
Probably in the future these different chargers will work better together through CAN protocol.

Some additional information.
When a charge controller, (solar or alternator) goes from Bulk voltage to Float voltage,the voltage need to go down.
Depend on size off battery and load amps are use it take some time till the float voltage is reached.
If the Float voltage is set too low it will take very long before this voltage is reached.

At this time the alternator is not producing amps, with the standard settings.
You can program that after Bulk, and BEFORE entering float, the shunt is keep at -2 amp for example.
This will discharge the batteries a bit, and voltage will go down to the float voltage.

You can program this with CPO, see manual.
example: $CPO:7 -2,120,13.36,0@
In this example, the ws500, keeps the shunt at -2amp for 2 hour, till 13.36 is reached.

After 2 hour it goes to the float setting from 13,.36V

In example from the 5 amp load.
2 amp comes out off the battery
3 amps comes out off the alternator.

Also with this if solar produce amps, the alternator will NOT produce amps.

The goal from regulator in CPO mode is -2amp, if solar charge at this time the alternator stopped.

Again program lower voltage in your solar.

Hope this info helps you,




That is helpful. The house batts are 450 a/h of AGM. I do have 100 watts solar panels. MPPT controller set to default AGM profile. I will test turning loads on, turning solar off. Simple boat, not many optional loads available. But SSB does consume 2 amps at idle. If that works then test if I can lower MPPT voltage, maybe but it's not a very sophisticated solar controller.



Hi all,

I have the same problem as Rand, but I have a different setup.

I'm running on LiFePo4 and when the BMS send the command to the WS500 on the Featured-IN white cable, the WS500 stop working and goes in float mode, for LiFePo4 is ZERO Amp produce. This is perfect, but as for Rand the tachometer stop working.

So I think that this is not the right way to manage the tachometer, I think it is almost the same for other BMS.
Is there any other solutions to have the tachometer always ON?

Or if not possible, what if I set the $CPF-LimitAmps to 2(for example), does the WS500 run in floating only 2Amps to my batteries until the Featured-IN back to normal status?


Max s/y Y2K

There is an mode for this called "Tach mode", search it up in the manual.

I have set minimum field to 3% and this works perfect.

But be careful as this could potentially overcharge the battery. So far I have not had an problem with this.



Yeah I remember very well that parameter ($SCT), even the advice not to overcharged the battery.
Yeah, I'll test immediately tomorrow.
Thank you so much for your help.


Start with 1%, then 2% etc until you get an reading.

The minimum field% will even be active during the 30 sec default startup sequence of the WS500.

I would not bother about RPM readings on Ide as this usually requires even more Field%.


I had a new engine installed this past winter, and I’m now experiencing my yacht bouncing around along with the current bouncing too.  I’ve checked connections, and everything appears solid, but now I wonder if this is related to what others are seeing.  I haven’t updated to the new firmware yet, and I need to take a look at my settings to see where I left things last year.

hello Massimiliano,
If your tacho stops, your batteries are probably full, there fore the alternator stop charging, because this is the best for the batterer.
See my explanation above.

In most cases program the CPO settings works very nice. (see explanation in above, answer to Randy.)
In your case the BMS switch to float by signal on feature in .
I will ask Wakespeed, when the bms trigger the feature in, Or the regulator goes to next charge step, OR straight to float.
If the regulator goes to next charge step, CPO setting will work for you.
(If the regulator goes straight to float, maybe Wakespeed like to consider to change this)

You maybe you will see a briefly stopped tacho, depend on the amount off amp your system is using.
If more load like fridges, light are on the quicker the alternator will reduce amps again, the quicker the tacho works.

Your suggestion:
Making the CPF higher will probably not work, because, battery is full and will not accept amps.
I think it is better when battery is full, to discharge the battery a little is better. This is done with the CPO settings.

SCT ""Tach Min Field setting"", I test this setting, but it is difficult as technician to do this for a customer, because the correct setting can only be made with lots off testing. This testing is very time consuming.

Every alternator and tacho will be different. Some tachos need very less off AC input to work correctly, other tachos need a higher AC input before start working.
If you use this setting, do plenty off testing with different settings AND also with different engine RPM's
I prefer the CPO, instead off SCT ""Tach Min Field setting"" which seams to work very good in many installs I did.




To Eboat,
Your setup can be different as the one from Randy, it is better to start your own thread, dicribe your setup, psot your settings, if possible with a testlog file. Then it is easier to answer what is wrong or not wrong in your system.

Hi Ben,
Thanks for your answer.
I'm not trying yet the $SCT test, I'll do in a couple of days.

>you said: "If your tacho stops, your batteries are probably full, there fore the alternator stop charging,
>>because this is the best for the batterer."

It is not true for my installation, exactly for the reason that the LiFePo4 is better not to charge at 100%, I stop the WS500 with the futured-IN cable at 80% of SOC and I configured to start to charge again under 65% of SOC.
So if I motor sail for a long period, and it happend in past unfortunately, I cannot stay without the Tachometer for so long period, but at the same time I don't have the battery always fully charged.

I'll test again your solution, but I think that the regulator with the featured-IN cable triggered go to float mode... well I need to test.




Hi Ben,  my setup is actually similar to Max’s.  I have a Rec Active BMS controlling the alternator via CAN bus.  When the charge gets to about 98% the tach starts bouncing, as does the charge current.  I upgraded the firmware this morning, as it appeared that the latest stable release was meant to sort out communication issues over CAN, however the behaviour hasn’t changed.  I will give the field percentage solution a go and see what happens.  I can always run my fridge on high to balance the load.