NextStep2 regulator bulk charge issue

[lateral]

OK, so back to the real world. I do not know anyone (on my pier) that motor around to get their 0.015C reading before tying up, or at least getting to the SOC that mains charger finger hook up will get them to 100% within their preset abs time frame. Why not? Too inconvenient, too spendy, unaware they are killing their batteries?

So what is generally being agreed here is that you need to be at 100% SOC before you leave the boat or do the math so you can make provision for in absentia charging to get you there, then drop to float to counter extraneous
minor loads/age losses?

If you tie up at mooring (or anchor) then you are deficient in the ability to top up as you probably arrived late and you won't get chance until next morning sun; which constitutes another cycle? So as necessary as solar is to the moored scenario, (Mainesail), it is not as optimal as a huge alt and motorsailing home?

Getting to the 100% thing, or near, definitely requires a bit of design thought to intended use and an awareness of what you are willing to put up with.
Me, I'd rather turn the motor off an know my solar panels are doing the work.
Maybe further away from a complete charge.

Or something in the middle.

[StuM]

Originally Posted by mitiempo

I read 14.7 volts as that is what it should have been.

Bulk charging has a setpoint, in this case it should be 14.7 volts. The charger, as joh61 states, puts out all current up to its maximum as long as the battery will accept it. The only regulation at this point. The only limit is the current the battery will accept. This is a constant current stage. Once the battery reaches that voltage the charger goes into absorption, holding that voltage for a period of time, ideally several hours. During the absorption stage the batteries continue to accept a declining current.

You canna change the laws of physics , Jim!

Once again you are confusing charge voltage with battery voltage.

If the battery voltage is the same as the charge voltage, no current will flow and no further charging will take place.

In bulk the charger does not maintain the current, but is wide open until the set voltage (14.7) is reached. The battery is the determining factor, not the charger.

Again - NO!. The current is limited by the potential difference between the charge voltage and the battery voltage. That is precisely why Bulk charging starts at a low voltage.

You state " once the internal voltage (actually surface charge) of the battery gets up to 14.7 volts absorption ends". Not true.

Yes, true. Once again, when charge and battery voltage are both at 14.7V, no current can flow. It's Basic Electricity 101. No voltage difference, no current.

Absorption is a timed event and must continue until the battery is very close to fully charged.

Not necessarily - you can set many smart chargers to hold absorption voltage for either 24 hours - OR until current acceptance falls below a certain level (which indicates that the battery is approaching Absorption voltage).

When the battery hits 14.7 volts it will continue to charge with a still high but declining current as the charge is absorbed into the plates. This is the reason for a long absorption time.

Please explain how you think that current can flow when battery and charging voltage are the same.

[StuM]

Final say:

If not by slowly ramping up the voltage during Bulk, how does my Outback Flexmate control the maximum current?

And if batteries can accept any current you throw at them, why does it even have an adjustable current limit?

And note that Absorption can be set to 24 hours which makes the low current cutoff the determining factor..

[john61ct]

Originally Posted by lateral

So what is generally being agreed here is that you need to be at 100% SOC before you leave the boat or do the math so you can make provision for in absentia charging to get you there, then drop to float to counter extraneous minor loads/age losses?

No one should burn fuel just for charging once you get past 85% or so when amps has started to drop very low, too wasteful.

That's why charging should be high-amps using fuel in the morning, to the point that solar have the whole day to finish up the long tail.

And yes you should be able to let your panels run unattended. If for a period of not cycling, may want to adjust settings so they don't run such a long bulk anew every day.

[john61ct]

Originally Posted by StuM

If the battery voltage is the same as the charge voltage, no current will flow and no further charging will take place.
...
Please explain how you think that current can flow when battery and charging voltage are the same.

Battery voltage drops way lower than Vabsorb once the charge source is off, even when "resting" with no loads. THAT is your "pulling" potential difference.

All points in a circuit are at the same voltage, the differing levels average out, but the flow is still there.

At the transition from CC (bulk) to CV (absorb) the battery may be only 75% full, and still requires 2-4x or more, time at absorb than it took to get there.

Originally Posted by StuM

The current is limited by the potential difference between the charge voltage and the battery voltage. That is precisely why Bulk charging starts at a low voltage.

Sorry, that's so wrong it is bizarre. The current is HIGHEST during bulk, precisely because the voltage difference is greater. Only limiting is battery resistance and the charger's set maximum.

If the limit is the max capacity of the charger then IMO it is too small, but again, depends on upstream limits too (HP of the engine, circuit capacity on shore).

When charging (same as battery) voltage reach the Vabs setpoint, here 14.7, that is end of Bulk CC and START of Absorb CV.

Originally Posted by StuM

It's Basic Electricity 101

Yes, it absolutely is, go and read up and you'll see.

[john61ct]

Originally Posted by StuM

If not by slowly ramping up the voltage during Bulk, how does my Outback Flexmate control the maximum current?

Because they added the extra circuitry to give you that option. In the explanations above, that setpoint becomes the "max current" applies during Bulk CC, then battery resistance lowers during the hours of Absorb CV.

The charger isn't raising voltage, the battery's is naturally climbing as SoC rises.

Originally Posted by StuM

And if batteries can accept any current you throw at them, why does it even have an adjustable current limit?

No one says they accept it all, just that making even 10x what they accept available doesn't cause any harm (with lead chemistry)


As to why allow limiting, the answer (again) is

1 to keep upstream mains CBs from tripping or downstream fuses from blowing

or 2 to prevent damage to underpowered "dumb" alternators.

or 3 so as not to take too much HP away from propulsion

probably some others

Originally Posted by StuM

And note that Absorption can be set to 24 hours which makes the low current cutoff the determining factor..

Yes, as long as endCurrent isn't confused be constant loads running, (ideally measure it from a dedicated Charge Buss shunt), it is much better to use that rather than Abs timing.

[belizesailor]

Originally Posted by StuM

...
Ask Maine Sail what would happen if you allowed voltage to get high enough to send those 320A into a "small lead battery." for any length of time.

Ive got AGMs at home ashore that specify charge acceptance as "unlimited"...really would like to see that put to the test...maybe a MythBusters episode.💣

[mitiempo]

Originally Posted by StuM

Ask Maine Sail what would happen if you allowed voltage to get high enough to send those 320A into a "small lead battery." for any length of time.

All charge sources are regulated for that reason. The regulation consists of a voltage setting for absorption. Other than dumb internally regulated alternators there is a float stage as well. Any battery will accept a massive amount of current if the voltage rises much above what it should.

As far as current, Lifeline has stated that their AGM batteries will accept 5 times their capacity at the beginning of bulk.

[jackt]

Originally Posted by mitiempo

No. What they are saying is to charge at 10% of the battery bank's capacity at the 20 hour rate. This is a minimum and is what most flooded battery manufacturers suggest. There is no maximum as at a given voltage the batteries determine the current they accept.

The reason the vendor stated 14.4 volts is the same reason virtually every AC charger and solar controller is set at 14.4 absorption. It is safe. Not best but safe.

14.7 is the absorption voltage for your batteries. Battery manufacturers know what your batteries need. Charger manufacturers just play it safe.

Brilliant! Thanks!

[jackt]

Originally Posted by john61ct

The number of AH a battery holds varies depending on how fast you draw it down from 100-0%.

The standard used to compare batteries is the 20-hour rate or "C/20", and you say yours is 460AH. They got that number by drawing down at a 23A rate, to 0% SoC over 20 hours.

So the minimum size charger at .1C (1/10th of 460, rounded up) you should use is 50A.

Lower than that will likely shorten their lifespan, and certainly make charging from 50% back to full take a very long time, say ten hours.

Better to get a 100A charger, then maybe 6 hours will be enough time.

Charge at 14.7A, until "full", meaning current drop to say 10A, only then go to Float. If your charger doesn't allow this, measure manually to calibrate Abs time. Default to longer rather than shorter, gassing's no problem with FLA, just replenish more often.

Ideally hit this Full level every cycle. Missing that more than occasionally will reduce lifespan. Same with going below 50%.

Equalize/condition according to vendor specs, ideally manually, supervising in person.

"The standard used to compare batteries is the 20-hour rate or "C/20", and you say yours is 460AH. They got that number by drawing down at a 23A rate, to 0% SoC over 20 hours."

Thanks! I'm such a dufus. I had it right the first time, then I got confused (forgot) what C20 means. Duh.

Great comments!!

[jackt]

Originally Posted by StuM

No. C20 (20 hour rate) is the number of Amp hours that the battery (or bank) will deliver if fully discharged over 20 hours. That is the most commonly quoted battery capacity. In this case it is 464 Amp hours.

(And the C20 rate would be achieved with an average current of 23.2 Amps 464/20. If you draw less than 23.2 Amps on average, your batteries would deliver more than 464 Ah, if you draw more than 23.2 Amps on average, they would deliver less than 464 Ah).

10% of the C20 Amp hour rating in Amps means 10% of 464 = 46.4 Amps.

So they are saying that for the initial bulk charging phase, keep the charge current at 46.4 Amps until the charging voltage climbs to 14.7V. (Your charger does this by starting at whatever voltage is needed to push that 46.4 Amps and steadily increasing the voltage to keep the current steady at 46.4A. Once the charger has ramped up to 14.7 Volts to achieve the 46.4 Amps, it holds the voltage steady at that level and the system enters the absorption phase where the voltage is maintained and the Amps that the battery can accept decreases steadily)

Thanks! I got confused on the C20 bit. All clear! For now!

GREAT COMMENTS!!

[jackt]

Originally Posted by lateral

I am aware of increasing Voltage to Vset/constant current in bulk phase, but JackT's posts harked back to somehow setting current in absorb, which made no sense to me.
All good stuff though.
I wonder if all bat manufacturers give their capacities in terms of C20?

Thanks Lateral. My original post actually was two parts. To paraphrase:

1. Why was it that with my new Nextstep2 reg and new batts (464 Ah), that at the end of my const. voltage (14.3V) absorption phase (woefully short at only 1 hour I now know!) was current still around 20A whereas with my old NS1, after also 1 hour abs, current had dropped to < 5A as expected.

2. Why is bulk phase apparently sometimes switching "early" to absorption - before set point of 14.3 is reached, like at around 14.1 or 14.2 earlier in some tests (eg, after Christmas when I got a new 50A 3-stage smart external charger, charged them up real good at dock, went off cruising, and at anchor seem to have seen the switch early, even at 14.0??). Also some recent tests in last few months. See earlier posts around Page 2:
http://www.cruisersforum.com/forums/...-179406-2.html

I think Q1 can be put to bed (bunk?).

As for Q2. Next time I'm at dock, maybe I should charge with external smart charger (50A, 14.7), get them full, and check NS2 again, with abs time at 2 hours and abs volt at 14.7V.

Or rather, FIRST do a test with the boat engine charging - NS2 (abs set to 14.7V and 4 hours?) and engine alternator (60A max is my usual) while they are NOT fully charged?? Suggestions?

Given the batt manufac recommendation was 10% of C20 Ah rating (10% of 464) = approx 50A for bulk/absorption...is there any advantage or disadvantage in charging at 60A using boat motor (my usual revs). You guys discussed this somewhat!!! What was the conclusion?!

[jackt]

It

Originally Posted by mitiempo

There's no problem except your interpretation. You do not have to worry about each cell.

Your charger should be 10% of bank size in AH. 46.4 (rounded to 50) amps for good battery life or larger.

14.7 volts absorption for about 4 hours.

What's not to understand?

Good. all understood now. But what if I was to let alternator at normal (happy, low-ish) engine revs charge at 60A?? It's a Bosch 90A and does no more than about 60-70 happily.

[jackt]

Originally Posted by john61ct

Not saying "should" but when you can afford it, some reasons for going bigger:

House loads can grow.

Next bank may be bigger.

Next bank may be a chemistry with (much) higher acceptance rate, and shorter engine/genset runtimes possible.

Especially with Alt mods (space, mounting, belts & pulleys) best to spend that upgrade money just once.

Also why a programmable unit to fine-tune setpoints.

Funds may not permit, but if possible remember banks are consumables, most of the surrounding infrastructure may (should) be "the last one" you pay for.

That may have answered my Q as to whether to charge at 60A. And it won't do any harm, right?

[lateral]

Originally Posted by jackt

Thanks Lateral. My original post actually was two parts. To paraphrase:

1. Why was it that with my new Nextstep2 reg and new batts (464 Ah), that at the end of my const. voltage (14.3V) absorption phase (woefully short at only 1 hour I now know!) was current still around 20A whereas with my old NS1, after also 1 hour abs, current had dropped to < 5A as expected.

2. Why is bulk phase apparently sometimes switching "early" to absorption - before set point of 14.3 is reached, like at around 14.1 or 14.2 earlier in some tests (eg, after Christmas when I got a new 50A 3-stage smart external charger, charged them up real good at dock, went off cruising, and at anchor seem to have seen the switch early, even at 14.0??). Also some recent tests in last few months. See earlier posts around Page 2:
http://www.cruisersforum.com/forums/...-179406-2.html

I think Q1 can be put to bed (bunk?).

As for Q2. Next time I'm at dock, maybe I should charge with external smart charger (50A, 14.7), get them full, and check NS2 again, with abs time at 2 hours and abs volt at 14.7V.

Or rather, FIRST do a test with the boat engine charging - NS2 (abs set to 14.7V and 4 hours?) and engine alternator (60A max is my usual) while they are NOT fully charged?? Suggestions?

Given the batt manufac recommendation was 10% of C20 Ah rating (10% of 464) = approx 50A for bulk/absorption...is there any advantage or disadvantage in charging at 60A using boat motor (my usual revs). You guys discussed this somewhat!!! What was the conclusion?!

Sorry busy right now but....
You have a 95A bosch with NS2, right? Four hrs motor run is excessive
if at fast idle - poor alt cooling and waste of fuel. Not familar with NS2 settings.
No harm I would say, but you are better off with shore charger. Bat Temp sensored for now to get back to 100%.
I have similar problems, belt wearing at high charge rate, non-configurability of ext reg...blabla....mooring..etc