Rpm reading when ‘float’

[Sjoerd Ooms]

Hello Al

For over a year happy now with the regulator.
Charge the battery now in a few hours while in the past after a few days I was depending on shore power to get the batt full again.

Only Isis is that when reaching float the amp meter does not give any reading or a fluctuating one (500-1000 rpm several times a second)

I have dip 8 on ‘ON’
Version is I think 1.0.0
Is there an improvement in the newer versions?
(I don’t want to fix if it ain’t broken)
Also heen using more than generator can deliver (negative on amp meter) I get a too high fluctuating reading.

Any suggestions? Not very important but nice to be fixed.

Thanks in advance
Sjoerd

[Al Thomason]

Hi,

Setting the alternators field drive level so they will continue to drive a tach but at the same time not overcharge the batteries is a hard line to walk. (DIP #8 Tach Mode: You must have the Gen 2 regulator, as DIP 8 means something different on the GEN3 regulators). When Tach Mode is enabled by default the regulator will monitor the Stator line until it is able to see a stable signal and derive the RPMs itself. The assumption is if the stator signal is sufficient to let the VSR Alternator Regulator derive RPMs, most likely any external tachometer will also be able to.

But that is not always true, as you have seen.

So, there is another option that lets you define the field drive level. Using the $SCT: command will let you fix a minimal field drive % to one that gives you a stable reading even during Float mode. In practice you can monitor the alternator AST status string looking to see what the field drive % is now during float, then try increasing that a % or two at a time until things are indeed stable. But be careful, too high of a value will prevent the regulator from keeping Vfloat down to a point where the battery is not being charged. And as an additional test (err, difficulty), the field value needed to drive the tac at low engine RPMs may well be different then high RPMs. So once you settle on a value, make sure to look at both low and high RPMs and make sure nothing is going wrong with your float charging...


Not sure I understand what you mean by: "... using more than generator can deliver (negative on amp meter) I get a too high fluctuating reading. " Can you elaborate? Could it be the belt is slipping?

Not much has changed in the tachometer code over the years. The most recent release (1.3.0) does have improved internal time measurement, and give a more stable RPM reading internally (via the AST string), but that will not impact how an external tach meter works...

Hope this helps some, these alt driven tach meters are a big issue I know. Maybe sometime can take a special focus to see if something can be done to fully SOLVE it once and for all... Ideas anyone?

-al-



Viking Star
45' Monk Sr. / McQueen
mvVikingStar.blogspot.com

[S]

Hello All,

Indeed a matter of RTFM(better)
I was looking in the wrong dip setting table.
Dip 8 in V3 is small alternator which is in my case 'ON' as well.

Checking the SCT I see tach = 0

I will change to 1 and monitor if ok now.

Thanks for your helpfully answer.

Kr Sjoerd

[Al Thomason]

No worries.  let us know how it works out!