Using both the Balmar instructions for the MC-614 regulator and some very helpful drawings, pictures, and advice from Farron, I installed the Balmar regulator, the Iskra brush box supplied by Beta, and triple-checked all wiring and connections. Nonetheless, there is a problem.
At idle, my shunt in the negative path to the house bank reports -1.7A when I would expect zero at worst and more probably some small amount of charging. Battery voltage (and alternator output voltage since they are directly connected) is 13.7 V and the MC-614 reports a Cv "target" of 14.3 V and a 96% field output. That doesn't seems to be being actually done by the alternator, for whatever reason. Also, my tach, now routed through the MC-614 as recommended, drifts upward to ~4000 RPM when the engine is very clearly running nearer to 600 or 700 RPM.
When I give a bit of throttle to reach 1200-1300 RPM, the tach does come back to that realistic value, my meter says +12 A of charging, and the alternator is driving the battery voltage to 16 V! And the charging alarm and light are ablaze, as appropriate, since the Balmar 15.2 maximum is exceeded. The MC-614 reports 0% field output, even though the alternator is, in reality, (over)charging up a storm!
At ~1500 RPM, more of the same. The tach looks the real RPM, my meter says +41 A of charging, and alternator output/battery voltage is 17.7 V! Once again, the charging alarm and light are ablaze, as appropriate, since the Balmar 15.2 maximum is exceeded and the MC-614 reports 0% field output, even though the alternator is, in reality, (over)charging up a storm!
Yet another check of the MC-614 settings and all wiring turned up no errors, though something is very clearly wrong. Nothing was on or drawing power in the boat during all of this. Shore charging to batteries works perfectly and shunt/meter readings during shore charging make perfect sense, so I guess the batteries (and shunt wiring) are fine.
Please, suggestions of what to check next are most welcome! Clearly cannot go sailing this way!
Lots more checking and measurements today but no new insights or errors found, so the problem persists. To get moving, I put the original internal regulator back in the Iskra, reconnected the panel light wire to D+, and made sure the tach line was routed back to the panel, and everything works as original. That means realistic tach readings at all times and predictable, although still way suboptimal, charging behavior. Suboptimal because the internal regulator runs charging at about 13.5 V and my Odyssey batteries really want about 14.6 V for bulk and absorption
Thinking more about the strange behavior with the MC-614 running, is it really correct in that case that there should be no connection to D+ and the panel light wire runs only to the designated MC-614 terminal? And why was tach behavior when routed through the MC-614 so wonky when the tach works fine when directly connected to alternator W? I don't find any Balmar programming or other guidance past the in and out terminal connections.
Will be calling both Beta NC and Balmar tomorrow!
Also, tried to edit my first post, below, to include a better picture and to correct that my idle RPM is really more like 800 RPM.
After quadruple-checking all connections and settings, I have reinstalled the brush box and a replacement MC-614 sent to me by Balmar. But the strange behavior remains. Above about 1000 RPM, the alternator output is way too high a voltage even though the MC-614 reports driving 0 percent field output.
Since this is now two regulators with different build batch dates and firmware revisions, it feels like there might be something wrong with the brush box since things seem to get into some unhelpful positive feedback loop where the field voltage is as high as the alternator output voltage, both way above any reasonable battery voltage.
Any suggestions for what to check or try next would be very welcome!
Turns out that the brush box was the culprit. Even though the internal tab was cut off as supplied, as it it supposed to be, it could nonetheless make contact with the internal D+ supply (used by the standard fixed regulator) and so the alternator was effectively running away. With a replacement brush box of the newer design (internal tab not connected to either of the brush connections), things began working as would normally be expected.
A shout-out to both Farron at Beta USA and to Dale at Balmar for the great help tracking it down and getting it fixed. Both companies are great to work with and another great reason to buy their products. Thank you!
