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rgleason · 16-01-2019, 08:45

C-Rate of .2C is in AH, such as .2 x 200ah (battery capacity) = 40ah

Now, this raises an interesting point. We cannot really set the Balmar regulators to charge at .2C There is a % of Field current setting that can be adjusted, but it is normally 65% for bulk and 65% for absorption. This is an indirect way of measuring current I think.

We could use the Belt Manager adjustments through trial and error to set the maximum Current the alternator outputs, but after those two settings there is no other way to adjust CC.

or Al Thomaston's VSR Regulator that actually measures and controls current.

john61ct · 16-01-2019, 10:00

Please do not hijack this thread.

Nothing here has to do with Balmar, any other conventional VR or really even alternator charging specifically.

When thomasow's "new SAR" is released and hard information is available about how it implements this "not new" type of charging algorithm, then

**that** should be the only actual charging device discussed in this thread,

I've just been posting about others simply to illustrate that such profiles are **not** new, and other such examples would be welcome.

Meantime, this thread is for discussing that type of charging as a general idea. Nothing discussed here should be taken as is to pertain to anything you want to implement in the near future.

Sheer gedanken, thought experiments, may not be possible, and even if it is, practical implementation issues are not relevant to the discussion.

Any specific numbers are just examples, feel free to plug in your own WAG, wherever you want to pull them from 8-)

_______
So, a recap of this "different but not new" charging logic:

Regulator explicitly controls current, adjusting "live" during the charge cycle.

CC only, no need for CV, zero AHT (yes absorb hold time).

Minimizing loss of AH capacity, so voltage setpoint varies depending on C rate.

Minimizing any hit to longevity due to higher than 3.4Vpc voltages.

And (maybe) also such impact due to high currents, minimizing charge times when that's the only reason ICE is running.

And again, if all this just sound nuts to you, you think it's not worth discussing, nothing constructive to contribute etc, please just move along and ignore the thread.

Putting words in my mouth, then other people discussing that "straw man", hardly clarifies anything.

john61ct · 16-01-2019, 10:13

Quote:

Originally Posted by rgleason

Al Thompson's regulator appears to be gone now. The VSR Alternator Regulator Schematics and CAD files appear to be gone, the onedrive is empty, so how does on get a PCB made?

No longer FOSS, gone proprietary / commercial.

> reduce the C-rate gradually as the battery gets fuller, such that the battery does not get hotter due to increased resistance, and so that the ending 13.88v point is at a greater %SOC than if I were to simply charge at some fixed CC (ah) up to 13.88v, I would do that.

That number may be higher or lower. I think as long as getting within 90-95% of some "theoretical / vendor" Full definition - as measured by load testing - that's likely "high enough". The lower end of that range being more conducive to extending longevity, each owner making a WAG trade-off without any real hard data.

> why isn't a user programmable regulator available for this?

Not much market. Hopefully enough for Al's device to ship for a while so we can experiment at the bleeding edge.

Or just use the Balmar, and trade off the two factors - longevity vs run-time - as you see fit. But OT here.

john61ct · 16-01-2019, 10:32

Quote:

Originally Posted by tanglewood

You can't apply 7a at 3.50v. You get to pick one or the other, but not both. What you could do is apply current up to 7a, and until the voltage reaches 3.50v. That's a classic CC charge up to some cutoff voltage.

Yes fundamental here is that voltage is being allowed to incrementally rise only as the current is being reduced **by the regulator**.

In conventional terms, imagine using two separate chargers. One is for bulk, at high amps, get up to say 3.49 and stop.

Then a lower current charger is used, allowed to continue adding to SoC, but now at lower amps. But still CC only, charge To a setpoint and stop.

Because lower amps at a given voltage does get to a much higher SoC, the voltage setpoint needs to be lowered as that higher SoC is achieved (Cpt Pat's caution)

At no point is the battery resistance the factor that lowers current, that would be CV/Absorb, here not relevant.

> why not run at 7a until voltage hits 3.55, and wait until acceptance current drops to .1A? It places you at the same end point.

Sure but that is the conventional algorithm, even though very rarely actually used in practice, egg timers attempting to sometimes-approximate endAmps is the norm.

In any case, CV-based stop-charging is off-topic here, please.

And in all questions of longevity vs charge profiles, there is no hard data, if that ends the discussion for you, no worries. . .

john61ct · 16-01-2019, 10:42

Quote:

Originally Posted by rgleason

AHT= AmpHours Trailing

No, Absorb Hold Time.

Most decent charge sources have the ability to at least influence that variable, if not directly set it.

Huge thread discussing Victron's less direct variables, noelex very au fait and critical thereof.

Ending Absorb via directly setting an endAmps setpoint, e.g. .005C, is only available when the regulator coordinates with an ammeter/shunt BM measuring at the bank. As I said, rare, so AHT is used as a proxy, and must change with conditions.

Hence my goal of eliminating CV completely, since with LFP getting to 100% Full is not a desirable goal anyway.

The per-cell stuff is just an artifact of example CC-only chargers I came across, irrelevant to the central idea here, worthy of its own thread one day.

john61ct · 16-01-2019, 10:57

Quote:

Originally Posted by rgleason

It seems to me this is what a good BMS should be responsible for, keeping the cells top or bottom balanced.

Answered over here
http://www.cruisersforum.com/forums/...27#post2804027

john61ct · 16-01-2019, 11:06

Quote:

Originally Posted by Q Xopa

Its not a far stretch to extrapolate that the cell manufacturers specified 'nominal' max charge isnt a magic number. Where above that rate its damaging and below that rate no damage occurs.

The same may be said for some other factors like range of SOC per cycle. Probably for similar reasons, heat etc.

Yes, even if the resources were devoted to research optimizing for longevity, there are way too many variables to provide black & white rules. Everything is greyscale, factors being traded off, judgment calls by each owner.

The rough guideline for big expensive lead banks "don't go under 50%" is indeed similar to the best that could be hoped for wrt LFP longevity.

Plus, that research is not being funded anyway afaict. . .

tanglewood · 16-01-2019, 17:50

OK, carry on talking to yourself, since any feedback other than "wow, that's great" seems off limits.

rgleason · 17-01-2019, 04:21

It seems to me that the idea is pretty clear, and it needs to be tried on a bank of lifepo to see if it makes any difference or perhaps to see if it can be done

After looking at Tanglewood's graph it does look like it will work.

tanglewood · 17-01-2019, 08:06

Quote:

Originally Posted by rgleason

It seems to me that the idea is pretty clear, and it needs to be tried on a bank of lifepo to see if it makes any difference or perhaps to see if it can be done

After looking at Tanglewood's graph it does look like it will work.

You can do it. I just don't think everyone understands how the circuit will respond to some of the description given, due to lack of electrical knowledge and battery experience. It's really more a question of what benefit it provides over other simpler and readily available approaches. See attached showing what has been proposed, and how it compares to another approach (I'm not allowed to say CV in this thread, so I'll just refer to it as the "other" approach).

So what advantage is there to the red line vs the yellow line? Both end at the same SOC. Both have the same fast charge rate through most of the charge cycle. Both incrementally reduce current as the target SOC point is approached. Both stay under whatever you consider to be a max voltage.

The proposed advantage is longer battery life. But based on what? Why? I just don't know why you would go to the bother without something more than an uninformed, baseless belief that it's better. There is just as much evidence and science to suggest that blue cables will extend battery life. Speaking of which, my LA bank is on year 11 and it has blue cables. Holy crap, I think we are on to something here......

rgleason · 17-01-2019, 10:13

Yes, this result of this "conceptual" routine is "unknown" at this point. It needs to be tested to determine the results.

Tanglewood your alternative approach shown nicely in Yellow, simply maintains 3550 milivolts until the same state of charge is reached.

It is unknown and unproven which approach will result in more cycles or less time, however I believe that the yellow routine you've shown, which maintains 3550 milivolts, would result in shorter charge times and fewer cycles.

It would be nice to be able to quantify the extent of these differences.

What I've learned is that there are two reasonable ways to reach higher SOC and that at 200ah Lifepo4 battery may have a larger usable range than I indicated in the Sizing Alternators for Lifepo thread. However utilizing that full range may result in somewhat shorter lifes/cycles.

It would be helpful to know how many cycles are lost maintaining a steady 3550 miliivolts for some duration (something that JohnCt61 will not do, due to his belief that it shortens battery life).

Which way to test? Cart before the Horse?
After testing, to determine what the differences in cycles are, the next problem would be getting a regulator that will follow the conceptual routing. On the other hand perhaps the best way to test is to actually have an alternator regulator that will follow this routine and record what happens in practice.

tanglewood · 17-01-2019, 11:24

Quote:

Originally Posted by rgleason

It is unknown and unproven which approach will result in more cycles or less time, however I believe that the yellow routine you've shown, which maintains 3550 milivolts, would result in shorter charge times and fewer cycles.

Shorter charge times - Yes. That's demonstrable.

Fewer cycles - Nothing in the literature to suggest it would make any difference, so purely imaginary at this point. If someone knows of anything credible to suggest otherwise, I'm (and probably others are) all ears. Or if someone truly believes, have at it with some tests to demonstrate and add to the literature and knowledge base.

john61ct · 17-01-2019, 11:49

Quote:

Originally Posted by rgleason

It would be helpful to know how many cycles are lost maintaining a steady 3550 miliivolts for some duration (something that JohnCt61 will not do, due to his belief that it shortens battery life)

Again, please stop twisting my words.

I am not opposed to CV charging in principle, and as you've seen, simple voltage alone is not the only factor.

Actually proving how these factors affect longevity, is not realistic without big money funding long-term research.

Now, again (and again), I have stated this thread is about this charging CC only idea.

**Please** take these more-general topic derails elsewhere!

Edit: here you go http://www.cruisersforum.com/forums/...rs-212766.html

just copy and paste quotes from here or other threads

And you guys keep it on track or not, as you see fit