MC-614 regulator setting question

[Jd1]

I searched high and low but couldn't find an answer to this question (which I find strange) so here it is:
Balmar MC-614 regulator controlling a Ballmar 200A alternator feeding a lithium battery bank.
I would like to feed as much current into the bank as possible in the shortest time so I figure I would play with the bulk charge settings. I have set bv (bulk voltage) to 14.4 and b1c (bulk time) to 6 hrs (to be tweaked later). The part I don't understand is field threshold, bulk to absorption or fba. Factory default is 65%.
If I want to cram as much current into the batteries without going to absorption, do I want to increase the percentage set point or decrease it ?
The manual says that raising fba shortens the calculated bulk charge time but I am having problems interpreting how calculated bulk charge time relates to actual bulk charging time.
I could really use a bit of interpretation for these settings.

Thanks !

[Dsanduril]

My understanding (subject to being completely wrong), the MC-614 looks at the current field value and voltages and estimates how long it will take for the field to drop to the FbA setting. In bulk you would expect the field to be at 100% (with deductions for temperature, etc.). As the field value starts dropping so does the charge rate, the calculated bulk charge time is the time from now until the field current drops to the FbA setting. So, setting it lower will extend the time spent in the "bulk" mode. Again, could be entirely wrong.

[Jd1]

Thanks Dsandruil. I have adjusted the fba value down to 10% and will see what happens in real life.
I have also tried moving the sense wire to different locations and both battery banks but the crux of the matter is that one sense line for two battery banks is not the greatest. I might haver to hobble along with less than optimal charging (which is what I originally expected) until the lead acid bank dies a natural death, to be replaced by a new lithium bank.
Interesting side comment - even though the mc-614 has a parameter for maximum voltage that only goes as high as 15.6V, I saw 18V from the alternator when the sense wire was on the lithium bank and it was disconnected from the alternator as it was full. Good thing I had no instruments or radios powered up

[autumnbreeze27]

What keeps your alternator from frying when your lithium battery high voltage cuts out?

my mc-614 settings are way different than yours, much more conservative.

[Jd1]

Originally Posted by autumnbreeze27

What keeps your alternator from frying when your lithium battery high voltage cuts out?

my mc-614 settings are way different than yours, much more conservative.

I currently have two battery banks - one is lithium and the second one is traditional flooded lead acid. The lead acid bank is connected all the time so there is still a load on the alternator when the lithium bank disconnects. It would be just as easy to shut down the alternator field just prior to an over charge condition if there wasn't another bank there.

Sorry for leaving that bit out. It wasn't required info in regards to the original question but I should have mentioned it when I mentioned the 18V reading.

[mbartosch]

Originally Posted by Jd1

Interesting side comment - even though the mc-614 has a parameter for maximum voltage that only goes as high as 15.6V, I saw 18V from the alternator when the sense wire was on the lithium bank and it was disconnected from the alternator as it was full. Good thing I had no instruments or radios powered up

You really should not do that (connecting the sense wire to the Lithium bank in a way that cutoff will "hide" the sense wire from alternator output).
If your cutoff is open your regulator sees only resting voltage of the Lithium bank and not the output of the regulator. It then thinks "hmm, it's too low, let's ramp up field" which increases output voltage of the alternator. However, this increased voltage is not seen on the sense wire - leading to even increased output.

You are lucky no more harm was done, it could have fried a lot of things!

[Jd1]

Originally Posted by mbartosch

You really should not do that (connecting the sense wire to the Lithium bank in a way that cutoff will "hide" the sense wire from alternator output).
If your cutoff is open your regulator sees only resting voltage of the Lithium bank and not the output of the regulator. It then thinks "hmm, it's too low, let's ramp up field" which increases output voltage of the alternator. However, this increased voltage is not seen on the sense wire - leading to even increased output.

You are lucky no more harm was done, it could have fried a lot of things!

Yeah, hindsight is 20/20 I figured that alternator output was limited to the maximum voltage setting on the MC-614 which it obviously is not. Makes me wonder what that setting is for then.
.... and yes, I was lucky

[autumnbreeze27]

what keeps the lead acid battery from siphoning power off your lithium battery when they aren't being charged?

[Jd1]

Originally Posted by autumnbreeze27

what keeps the lead acid battery from siphoning power off your lithium battery when they aren't being charged?

The alternator feeds a FET isolator (similar to a diode isolator but without the voltage drop) and the battery banks are supplied from separate outputs of the isolator.