Nucular Battery Charging clarification

[bikerpete]

I've read a lot of posts covering aspects of the Nucular battery charging capability but have found it all a little scattered and for the less electronically adept (me) a little hard to extract the key take-home messages.

I don't yet have a Nucular (12F on order) so perhaps some of this will become more self explanatory when I do.

My understanding is that:
1. The Nucular can act as a complete battery bulk charge controller (but certainly not a BMS).
2. The DC input voltage needs to be below the battery voltage. Is this below the minimum, nominal or max battery voltage? And how much below is a reasonable value to aim for?
3. The power supply can be a pretty basic regulated PSU. Presumably even fairly basic over current protection is fine because the Nucular settings should keep everything correctly limited. A simple fuse could be enough?

I'm planning a 16s LiPo pack so should I be aiming for V below 2.8x16=44.8 so say 42V? Or would 3Vx16=48V be reasonable given I'm not planning draining them past 3.1-3.2V (I'll have a BMS)?

I'm aware some of my questions below relating to determining cut-off voltages etc are certainly covered in other discussions about batteries and their chemistry, but if someone could distill their knowledge here it would be great, I'm spending so much time acquiring knowledge that I've none left over to actually build!

Below are the relevant configuration sections from the Nucular Wiki:
Battery
Full charge - delta voltage relative to the maximum, at which when the controller is turns on, will reset the watt-hour consumption
I'm reading this as saying that once the battery voltage rises to this level the controller will reset Wh value. No other implication.

Supply min-max V - battery voltage range. Also used for Converter mode. For a lithium ion, it can be considered a minimum = 2.8V*S, a maximum of 4.2V*S. For LiFePO4 minimum 2.5V*S, maximum 3.6V*S.
Does this set the Max charge cutoff voltage?

Charge max - maximum battery charging current, during regeneration or in Converter mode.
Does this relate to "Battery max I" below? ie if no value specified for "Battery max I" then this value is used?

Converter
Here you can configure charging mode from the power supply through the motor. Charging through the inductor is not currently supported.

Enable - turn on the converter mode and starts charging.
Auto-Enable - automatic start of charging when the charging PSU is connected to the controller
Detection threshold - minimum voltage on phases when charger mode activates, also disables motor control.
Self explanatory I think - manual or auto charger detection, and the minimum input voltage to trigger auto detection.
Not clear about the inductor not supported part. I thought that was the whole idea, that it used the motor coil as the inductor?

Battery max I - if no value is specified, then battery settings are used, maximum battery current.
Max charge current. If not set then Charge max value is used. Not quite sure why this value is in 2 places, but there you go.

Battery min I - minimum charge current when current decreased by voltage.
This is obviously related to Current drop delta below, but I'm not sure how to determine the appropriate value? I'll be using LiPo packs for my first build.

Undercharge - voltage relative to maximum battery voltage setup, lets you to decrease full charge voltage.
Not clear how this relates to Supply min-max V? I'm thinking that the min-max is the battery rated values that are hard limits for the controller, and Undercharge is used to set the charge voltage to allow for longer life etc.?

Current drop delta - decreases charging current down to Battery min I as the battery reaches maximum voltage on specified voltage range.
A bit cryptic to me what the "specified voltage range" is? I'm thinking this is relative to the Supply min-max V in Battery section? So the delta is the amount of volts below that max V at which you want the charger to drop to CC mode and slowly top off the battery until it reaches Undercharge voltage? How best to determine this value?

Supply max I. - maximum power supply current
Supply drop U - allowable voltage drop on wires or power supply
Not clear how to use Supply drop U? Given there's nowhere to tell the controller what the nominal input supply voltage is, how does this relate to anything?

Max motor t° - limits motor temperature during charge.
Below # shows the real time values ​​of voltages and currents.
All pretty clear I think. I'm presuming that on the screen it displays real time values below these settings.

Finally, does the Nucular turn off the charging circuit when it reaches the final voltage (Battery Max V - Undercharge V) or does it just sit at the min charge current? And if it does turn off, is it possible to use an I/O to send a signal out to the PSU to turn off, or some other method?

Cheers.

 

[serious_sam]

1. The Nucular can act as a complete battery bulk charge controller (but certainly not a BMS).
2. The DC input voltage needs to be below the battery voltage. Is this below the minimum, nominal or max battery voltage? And how much below is a reasonable value to aim for?
3. The power supply can be a pretty basic regulated PSU. Presumably even fairly basic over current protection is fine because the Nucular settings should keep everything correctly limited. A simple fuse could be enough?
4. I'm planning a 16s LiPo pack so should I be aiming for V below 2.8x16=44.8 so say 42V?

1. Correct.
2. PSU voltage must be below minimum batt voltage. It really depends on how low you will run the pack. Plan for a worst case where you accidentally run down to LVC, and subtract some margin from that, say -4V.
3. Yes. Basic regulated DC. Ensure that it's current limit is above what you set in the NUC. i.e. don't pull more than it is rated for.
4. I would aim for something below your BMS LVC with margin, just in case. Otherwise if you do accidentally hit LVC you will need to find an alternative method to charge back above that voltage.

Or would 3Vx16=48V be reasonable given I'm not planning draining them past 3.1-3.2V (I'll have a BMS)?

Side note: as a general suggestion, it's a good idea not to regularly run down to your BMS LVC. Use the BMS LVC as a "I f#cked up" safety limit, rather than regularly pounding on it. Keep track of your energy consumption via NUC display, and manage your batteries accordingly using your brain instead.

For example, on a "long" ride, I will run my VTC6 cells down to about 3.0V (no load voltage). And sometimes I also run a large amount of sag (~0.4V sag per cell at low SOC - for me it's an acceptable price for pulling high power from a small pack). So my actual cell voltage might get down to ~2.6V under load in rare cases. My LVC is set to 2.5V, which allows me to run down to 2.6V under load without cutting out. But if I ever hit the 2.5V LVC, it's because I f#cked up, I'm not paying attention, and it saved my ass, OR one of my cell groups is having a problem.

If everything goes according to plan, then I monitor my energy consumption on the NUC display, and adjust my remaining ride accordingly. Haven't ever hit LVC, but good to know that it's there.

Just to be clear, I'm not suggesting that you set your LVC to 2.5V (I have no idea what current/sag you will run with LiPos). I'm just saying, consider how low you want to run your cells, take a bit off for sag (depending on your cell type and max current draw), and make your LVC somewhere just below that.

 

[john61ct]

WRT to charging

without the ability to use "some" (ideally adjustable) algorithm to determine 100% SoC - even if just HVC for a CC-only profile

and then to **terminate** charging

it is not a charger, just a boost converter like a PSU.

And I would not rely on a BMS to handle that safety-critical function, unless there is another HVC + timer based backup / failsafe in place.

Ideally it would also allow for adjustable current limiting as well, e.g. drawing from a stock automotive alternator while traveling.

 

[999zip999]

Sam how big is your pack and are you running a Bluetooth BMS that's adjustable ?

 

[serious_sam]

WRT to charging

without the ability to use "some" (ideally adjustable) algorithm to determine 100% SoC - even if just HVC for a CC-only profile

and then to **terminate** charging

it is not a charger, just a boost converter like a PSU.

No, that is your preferred terminology. Not fact.

You should stop stating your opinions as fact around here.

A charger is something that charges batteries. Full stop. Some are "smart", some are not. Just because my charger doesn't terminate at 100% SOC, doesn't make it not a charger. It just makes it less capable or less foolproof than one that does terminate or have other functionality.

 

[serious_sam]

Sam how big is your pack and are you running a Bluetooth BMS that's adjustable ?

20S5P Sony VTC6. I'm using a "generic"/adjustable 20s 50A bluetooth BMS, with upgraded mosfets, shunts, and copper, so it handles 150A easy.

The programmability is good. I like being able to check the cell voltages and temperatures. I'm not totally impressed with the precision of the balancing function though. I can only get my cells within 10mV, no matter how long I leave the balancing function active.

 

[bikerpete]

Thanks for those responses.

Finally, does the Nucular turn off the charging circuit when it reaches the final voltage (Battery Max V - Undercharge V) or does it just sit at the min charge current? And if it does turn off, is it possible to use an I/O to send a signal out to the PSU to turn off, or some other method?

So I'm reading it that No, the Nucular does not terminate charging, just sits there at float level until some-thing/one turns it off.
That's a pity.

Any suggestions on reasonably simple options to achieve charge termination ........
Perhaps I'll just set a 240V timer to slightly more than expected charge time. And a BMS as planned.
EDIT: I thought about this and realised that what I was asking for was pretty much a BMS. Lots of solutions already out there. Presumably the future Nucular BMS will tie in with this nicely.

Ideally it would also allow for adjustable current limiting as well, e.g. drawing from a stock automotive alternator while traveling.

I didn't quite follow this. The Nucular has Battery max I setting - I'd expect this is exactly what you're suggesting.
This is something I've wondered about since first posting - the supply voltage has to be lower than the battery voltage, but is there a limit to the voltage difference? Could I in fact charge a 16S 67V battery from a 12V supply (albeit probably rather slowly)? This could be very useful to me.

 

[john61ct]

A charger is something that charges batteries.

No.

A ciggie plug stuck in your dashboard will **add Ah** to a 3S pack.

Same with raw solar panels for lots of possible voltage levels.

Does not mean a charger - a proper charger - is involved anywhere

If you need to sit and watch V&A with separate instruments in order to terminate the cycle at Full

then you are not using a proper charger.

Also proper current limiting (not just latching or hiccup "current protection") is a required feature in most cases.

Present in every charger I've seen, missing in most voltage regulated sources, including alternators, DC converters, power supplies (aka rectifiers).

Very easy for a big LI battery to let out the magic smoke. . .

Old-school garage "trickle chargers" and ancient sub-par USian RV "converters" (actually PSU/rectifiers) that just keep on outputting charge forever until manually turned off

are a laughing stock if used for anything but FLA batteries, will lead to an accelerated murder of the bank.

Which is not a good thing for a charger to do.

 

[john61ct]

So I'm reading it that No, the Nucular does not terminate charging, just sits there at float level until some-thing/one turns it off.

Float level is a 3-stage "intelligent" charger dropping the voltage down to a lower level, ideally around that specified by the **lead** manufacturer.

Should only happen after 100% Full is reached, needed for long life

but completely irrelevant to (in fact in opposition to) what LI cells want for long life.

LI does not even need any CV, zero AHT is healthier than pushing ever higher up toward some arbitrary harmful vendor definition of 100% Full.


> Any suggestions on reasonably simple options to achieve charge termination

HVC terminating the cycle upstream, in most cases at the AC input.

Ideally driven by cell/group-level voltage.

A timer assumes charging always has the same current level and the same SoC starting point.

> the future Nucular BMS will tie in with this nicely

Very unlikely he would include failsafe doubling of the HVC at separate setpoints. Would be a first afaik.


> I didn't quite follow this. The Nucular has Battery max I setting

No idea, I was speaking about first principles not any specific (attempt at) implementation.

Maybe explain how / if that setting works with stopping regen when the battery is at 100% Full


> the supply voltage has to be lower than the battery voltage, but is there a limit to the voltage difference? Could I in fact charge a 16S 67V battery from a 12V supply (albeit probably rather slowly)

Yes too high a required boost usually means much lower efficiency in the conversion.

It is too **low** a difference that more often causes the boost conversion to just stop.

 

[bikerpete]

So I'm reading it that No, the Nucular does not terminate charging, just sits there at float level until some-thing/one turns it off.

Float level is a 3-stage "intelligent" charger dropping the voltage down to a lower level, ideally around that specified by the **lead** manufacturer.

Should only happen after 100% Full is reached, needed for long life
but completely irrelevant to (in fact in opposition to) what LI cells want for long life.
LI does not even need any CV, zero AHT is healthier than pushing ever higher up toward some arbitrary harmful vendor definition of 100% Full.

Thanks John. I think you understand the gist of what I'm saying - the charger/system will continue to deliver volts/amps to the battery - what it's called technically by whoever is of little interest to me.
I'm after info specific to the how the Nucular operates and how I might make it work in a manner more suited to me - plug it in, let it charge and expect it to stop when the battery is "full" as per my settings.

> Any suggestions on reasonably simple options to achieve charge termination
HVC terminating the cycle upstream, in most cases at the AC input.
Ideally driven by cell/group-level voltage.
A timer assumes charging always has the same current level and the same SoC starting point.

Yes, fine, but how do I achieve HVC termination with the Nucular?
And no, a timer assumes nothing - it's an electrical device. The dummy who sets the timer is the one making the assumptions/estimations and it's reasonably trivial for a human of modest intelligence and some experience with a particular device to make an educated estimation of how long the charge might take. "I rode for 20 mintues, pretty conservatively. In the past that's taken around 20 minutes to charge. I'll set the timer to 20 minutes".

> the future Nucular BMS will tie in with this nicely
Very unlikely he would include failsafe doubling of the HVC at separate setpoints. Would be a first afaik.

I was thinking that the BMS and the Nucular might talk to each other a bit given they are from the same developer and Nuc has CAN network. Maybe the Nuc tells the BMS to let it know when the cell groups hit the charge set point in the Nuc's settings, the BMS balances and monitors and as soon as everything hits the setpoint it tells the Nuc to shutdown. If any of that discussion fails then the BMS's own HVC would trip if the charge goes awry.
Just my logic, or illogic.

> I didn't quite follow this. The Nucular has Battery max I setting

No idea, I was speaking about first principles not any specific (attempt at) implementation.

Maybe explain how / if that setting works with stopping regen when the battery is at 100% Full

I don't know, I can't see anything definitive in the Wiki.

> the supply voltage has to be lower than the battery voltage, but is there a limit to the voltage difference? Could I in fact charge a 16S 67V battery from a 12V supply (albeit probably rather slowly)

Yes too high a required boost usually means much lower efficiency in the conversion.

It is too **low** a difference that more often causes the boost conversion to just stop.

No problem, slow and inefficient is better than nothing.

I just ordered a 3000W 42V power supply (Cisco WS-CAC-3000W) so I don't think too high voltage will be a problem with 16S given what was said above, and a bit of inefficiency wont be a big deal with that much power available to fritter away.

 

[john61ct]

Yes I have all the same questions.

Maybe the day will come that He Who Matters will consider this assist-charging functionality to be important enough to sales success to clarify things so a forum guru can write up some comprehensive HowTo cookbook documentatiin on the topic.

Or maybe the brave pioneers will muddle through and eventually figure it all out via trial and error, just take longer to get us to that desired point.

 

[bikerpete]

I pre-ordered a Nucular BMS on the assumption they'll do as good a job of it as they have the controller.

I asked, "The one feature that I'd really like to see in the BMS/Controller system is that the BMS controls the final shutdown of charge through the controller."

The response was, "We will plan this function in BMS, the determination that the charge is complete and turning off the charging."
I choose to read that in translation as "it's planned".

Sounds like a perfect topology to me - BMS monitors batteries and lets the charger (controller) know when to turn off. Each is doing what it does best.

 

[serious_sam]

does the Nucular turn off the charging circuit when it reaches the final voltage (Battery Max V - Undercharge V) or does it just sit at the min charge current?

It doesn't currently turn off, it just reduces to a "trickle" current, as per a cc/cv charge process with no cut-off.

But Vasiliy said that a timeout and some min current level for shutdown is something that he will be looking to add in the future.

 

[bikerpete]

does the Nucular turn off the charging circuit when it reaches the final voltage (Battery Max V - Undercharge V) or does it just sit at the min charge current?

It doesn't currently turn off, it just reduces to a "trickle" current, as per a cc/cv charge process with no cut-off.

But Vasiliy said that a timeout and some min current level for shutdown is something that he will be looking to add in the future.

Thanks, that's the conclusion I'd come to.
So maybe in a future upgrade, or when the BMS is released it will become a "smarter" charger.

 

[john61ct]

Just FYI, the phenomenon of amps "trailing" down after hitting the CV / Absorb setpoint

is not due to any control by a charge regulator,

but determined by the target battery's internal chemistry reactions, rising resistance etc.

Letting this continue at the CV voltage after the endAmps point, say dropping lower than 0.02C is harmful to battery longevity and increases risk of thermal runaway (boom bad!)

Personally I use 0.05C (as well as a lowered CV), and even then, only when occasionally requiring a capacity benchmark, or if top balancing.

 

[bikerpete]

Just FYI, the phenomenon of amps "trailing" down after hitting the CV / Absorb setpoint

is not due to any control by a charge regulator,

but determined by the target battery's internal chemistry reactions, rising resistance etc.

Letting this continue at the CV voltage after the endAmps point, say dropping lower than 0.02C is harmful to battery longevity and increases risk of thermal runaway (boom bad!)

Personally I use 0.05C (as well as a lowered CV), and even then, only when occasionally requiring a capacity benchmark, or if top balancing.

Roger.

That's my concern about the Nucular charger not terminating at any point.
I consider myself moderately able to be involved in managing the charging, but also significantly more interested in spending my time doing other things. Nett outcome is that I have to recognise that it's highly likely that at some stage I'll walk away from my charging battery and completely forget about it. I'd be pretty sad if I came back to a significantly damaged battery, or worse.

I think I'll be using a simple timer and some guesstimation to set a charge end point. Perhaps in future the Nucular will be capable of managing that for me more efficiently. At that point I'll likely continue using the timer, but set a bit more generously - more a last resort if the Nuc cutoff fails.

 

[dogman dan]

Link to this thing would help. Google gave me a link to a nucleus 6 charger, and some portable batteries with pictures of Einstien, Bikini test, etc on them.

Get a Satiator. Set it to do what you want, at the rate you want, and the voltage you want.

 

[j bjork]

It is about the charging trough controller function in the nucular controllers:
https://endless-sphere.com/forums/viewtopic.php?p=1532573#p1532573