Fechter's Mini Meanwell Limiter Board

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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Mon Jan 30, 2012 1:59 pm

wineboyrider wrote:So if I had two 15amp :D :D :D PC psu in series at the 12v connector that should give me a 25v lipo charger capable of 15 amps....! :D :D :D

Correct. Make sure that the ground (case) of the supplies are not connected, it may be that the negative output is connected to the case, I am not sure but good to look out for (measure with a multimeter) as it is easi to bolt both to a metal frame, then if you connect the first +12V output to the next negative output, you may short out the first supply...
(That is why Neil has all supplies on an insulating mat)
NOTE that this gives you a fixed 24V supply, not a battery charger unless you add current limit! PC supplies normally do not have a good current limit from itself...
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Re: Fechter's Mini Meanwell Limiter Board

Postby NeilP » Mon Jan 30, 2012 2:15 pm

wineboyrider wrote:So if I had two 15amp :D :D :D PC psu in series at the 12v connector that should give me a 25v lipo charger capable of 15 amps....! :D :D :D


Almost Cor..the insulating mat is to stop all the bare wires from shorting out on the metal bench.

My supplies have all been hacked inside..traces cut on the PCB's to isolate the negative line from the chassis. All out mains plugs here are earthed, which would put the negative line on the output side common to all supplies via the chassis and earth.

So yes, a pair of PC supplies would give you about 15 amps...jsut depends on the output the 12v line would put out. if you can get more, go for 5 of them on the 5 volt line


Either search my posts for PC supply type threads, or google for PC PSU mods..not a lot to it

cor wrote:, it may be that the negative output is connected to the case, I am not sure but good to look out for (measure with a multimeter) as it is easi to bolt both to a metal frame, then if you connect the first +12V output to the next negative output, you may short out the first supply...


Yes, at least in UK, the negative black output line is common to the case.

cor wrote:NOTE that this gives you a fixed 24V supply, not a battery charger unless you add current limit! PC supplies normally do not have a good current limit from itself...


You can sometimes getaway with not having a current limiting source. I have had limited success doing it ..but often you end up chasing the supplies along the line..as you power one up, another drops out...I have a huge stack of dead PC PSU..30 or more..and have probably zapped a good few..10 or so at least.

That is why my current setup includes a current limited meanwell...current limiting as well as fine voltage adjustment

Will try and find the correct threads in a moment
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Re: Fechter's Mini Meanwell Limiter Board

Postby NeilP » Mon Jan 30, 2012 2:23 pm

here are a few threads to get you going...have had a quick look,, only one has a bit of info on which wire does what and how to start them up...green to black

viewtopic.php?f=14&t=25298

viewtopic.php?f=14&t=28632

viewtopic.php?f=14&t=28891

What you also need to do is open up each one, remove the pcb from the case, then cut and remove any trace that is connecting any electrical part of the board to the mounting posts.

Follow each trace and see if you are isolating any parts by cutting the traces. if so then solder jumper wires across the breaks you have made..keeping the mounting post corners free of connection to the negative line
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Tue Jan 31, 2012 1:02 am

NeilP wrote:Almost Cor..the insulating mat is to stop all the bare wires from shorting out on the metal bench.

Ah, you already took care of the cases=ground. Good.
NeilP wrote:So yes, a pair of PC supplies would give you about 15 amps...jsut depends on the output the 12v line would put out. if you can get more, go for 5 of them on the 5 volt line

That would likely give you 25V, 30A or something like that.
NeilP wrote:You can sometimes getaway with not having a current limiting source. I have had limited success doing it ..but often you end up chasing the supplies along the line..as you power one up, another drops out...I have a huge stack of dead PC PSU..30 or more..and have probably zapped a good few..10 or so at least.

Yes, PC supplies are not so well regulated, so the voltage varies quite a bit with load - this "soft" behavior helps in cases of overload as in battery charging.
However, the simplest way to use PC supplies (or other fixed power supply) and charge a pack with them is to set the supplies to the maximum charge voltage by tuning the output voltage if possible or by combining different voltages - for PC supplies you can choose from 12V, 5V and 3.3V and with multiple supplies you can make a lot of combinations, for example to charge a 4s LiPoly pack (up to 17V max if it is well balanced and each cell goes to 4.25V) you can add the 12V from one supply to the 5V from another supply (usually you cannot combine the voltages from the *same* supply as they are tied together at the negative side) or use 3 supplies for more current: place 2 12V supplies in parallel to double their current and add the 5V from the third supply.
Note that if you can't get the right voltage then you can create a voltage a little higher and add heavy duty low voltage diodes in series to drop the voltage by about 0.8V for each (silicium) diode.
Note also that the 12V supplies might not be the exact same voltage and so they might not share the current evenly.
Also, to charge a pack that is quite empty and has a low internal resistance, the voltage of the charger will need to drop. Power supplies do not like this, they try to deliver all they have, overheat and die.
One simple way to solve this if the voltage difference between your pack and power supplies is no more than 15V is to place a few car headlights between the supply and the battery. Incandescent bulbs are pretty good current limiters and a typical 55W headlight will give you a current between 4 and 5A over a wide range of voltages, probably from lower than 8V to above 15V. So, to limit a PC supply setup to a max of 15A you wire 3 headlights in parallel between the string of supplies and the pack. No more blown supplies and the headlights give a visual indication of the charging progress: first bright, then slowly extinguishing while the pack comes up in voltage (charge). When the current drops below 1 or 1/2A then the charging is done.
If you can scrounge a couple headlights from a junkyard (or from your garage) then you only need to wire them in and off you go. No modern electronics required ;-)
Last edited by cor on Tue Jan 31, 2012 1:11 am, edited 1 time in total.
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Re: Fechter's Mini Meanwell Limiter Board

Postby fechter » Tue Jan 31, 2012 1:09 am

BTW, the mini limiter board should work with most PC power supplies as they are very similar to the Meanwells. The hard part will be finding the OVP pin equivalent spot to tie in the feedback line. There seems to be a million different varieties of PC supply, but they are all similar.
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Re: Fechter's Mini Meanwell Limiter Board

Postby wineboyrider » Tue Jan 31, 2012 9:04 am

I have been charging my 6s scooter with my ping chargers, which are set to 45 volts. Is this a problem? I know I can't overcharge the lipo batteries, but I am monitoring the cell charge level with a cell log.
8) 8) 8)
I think I'll just use the power supplies I have as a power supply for my hyperion.....
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Re: Fechter's Mini Meanwell Limiter Board

Postby Ykick » Tue Jan 31, 2012 9:10 am

wineboyrider wrote:I have been charging my 6s scooter with my ping chargers, which are set to 45 volts. Is this a problem? I know I can't overcharge the lipo batteries, but I am monitoring the cell charge level with a cell log.
8) 8) 8)
I think I'll just use the power supplies I have as a power supply for my hyperion.....


I hope you mean 2qty 6S in series for 12S? Other wise you'd be charging each cell to 7.5V.

If 12S, you're only getting to 3.75V/cell so that's not gonna be much of a charge. I try to do my 12S around 49-50V.

Perhaps I missed something you're not talking RC Lipo?
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Re: Fechter's Mini Meanwell Limiter Board

Postby wineboyrider » Tue Jan 31, 2012 10:25 am

Ykick wrote:
wineboyrider wrote:I have been charging my 6s scooter with my ping chargers, which are set to 45 volts. Is this a problem? I know I can't overcharge the lipo batteries, but I am monitoring the cell charge level with a cell log.
8) 8) 8)
I think I'll just use the power supplies I have as a power supply for my hyperion.....


I hope you mean 2qty 6S in series for 12S? Other wise you'd be charging each cell to 7.5V.

If 12S, you're only getting to 3.75V/cell so that's not gonna be much of a charge. I try to do my 12S around 49-50V.

Perhaps I missed something you're not talking RC Lipo?

What I have done a couple of times is charge my 6s lipo with my 36v lifepo4 charger while watching the cells on my cell log monitor. I'm still alive and I know the voltage is higher than the lipo so I need to monitor them closely, but what I really want to know is if there is a problem with it other than over charging my lipos which could be easy to do with a higher voltage charger. I have a turnigy watt meter in line with it to monitor the wh, watts, amps etc...?
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Re: Fechter's Mini Meanwell Limiter Board

Postby Ykick » Tue Jan 31, 2012 10:34 am

wineboyrider wrote:
Ykick wrote:
wineboyrider wrote:I have been charging my 6s scooter with my ping chargers, which are set to 45 volts. Is this a problem? I know I can't overcharge the lipo batteries, but I am monitoring the cell charge level with a cell log.
8) 8) 8)
I think I'll just use the power supplies I have as a power supply for my hyperion.....


I hope you mean 2qty 6S in series for 12S? Other wise you'd be charging each cell to 7.5V.

If 12S, you're only getting to 3.75V/cell so that's not gonna be much of a charge. I try to do my 12S around 49-50V.

Perhaps I missed something you're not talking RC Lipo?

What I have done a couple of times is charge my 6s lipo with my 36v lifepo4 charger while watching the cells on my cell log monitor. I'm still alive and I know the voltage is higher than the lipo so I need to monitor them closely, but what I really want to know is if there is a problem with it other than over charging my lipos which could be easy to do with a higher voltage charger. I have a turnigy watt meter in line with it to monitor the wh, watts, amps etc...?


As long as you don't forget or pass out from too much Wine, that does work. But if you forget, holy smokes! Did you ever rig up an off timer for AC power? That could be a last line of defense but using this setup as described is risking Lipo over voltage, IMO.
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Re: Fechter's Mini Meanwell Limiter Board

Postby wineboyrider » Tue Jan 31, 2012 10:57 am

I remember seeing your post on this. I bought 2 ezip scooters for $150.0 on cl and I want to keep one pretty much stock on 6s lipo for the kids to ride. I know the lipos can charge easily 1c and since I have my ebikes running on 36v lifepo4 and 12s and 10s lipo mostly is buy a 600w charger for opportunity charging when I'm traveling. The 600w charger I could also use when we go to the park and ride the scoots so we can get some extra rides out of them. There is an electrical outlet at the park where we ride that I know is live so I'm hoping to kill 2 birds with one stone. I also plan on buying a regular 2 amp charger from BMSbattery.com set to 24.5v so I can keep the 24v scoot ready to go when the kids get out of school....?
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Tue Jan 31, 2012 4:08 pm

wineboyrider wrote:I also plan on buying a regular 2 amp charger from BMSbattery.com set to 24.5v so I can keep the 24v scoot ready to go when the kids get out of school....?

Hi Wineboy,
That would be very adviseable.
Even when you *plan* to watch careful while charging the 25V pack with the 36V charger, the charger will take an hour to replenish an empty battery (BTW, are you running a BMS or voltage monitor? Discharging the LiPoly too far is equally destructive to the cells as overcharging them) so it is like watching paint dry and you might get distracted at some point, or an emergency happens and you come back to a cooked (on fire?) pack...
BTW, where did you get your 36V charger? I have a 8s pack and need about 34V charger while I only have 48V units. Turning them down to 34V is OK but they do not go much lower or start hiccuping, so I can't charge an empty pack with those.
Last edited by cor on Wed Feb 01, 2012 2:20 am, edited 1 time in total.
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Re: Fechter's Mini Meanwell Limiter Board

Postby fechter » Tue Jan 31, 2012 9:49 pm

As long as Lipo cells are well balanced, it should work OK to just set the maximum voltage of the charger to 4.15v / cell or maybe a little lower if you want to be safer. Once the cells reach that voltage, the current will drop to near zero essentially stopping the charging process. The charger could stay on for a really long time without overcharging any of the cells.
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Re: Fechter's Mini Meanwell Limiter Board

Postby wineboyrider » Wed Feb 01, 2012 8:52 am

cor wrote:
wineboyrider wrote:I also plan on buying a regular 2 amp charger from BMSbattery.com set to 24.5v so I can keep the 24v scoot ready to go when the kids get out of school....?

Hi Wineboy,
That would be very adviseable.
Even when you *plan* to watch careful while charging the 25V pack with the 36V charger, the charger will take an hour to replenish an empty battery (BTW, are you running a BMS or voltage monitor? Discharging the LiPoly too far is equally destructive to the cells as overcharging them) so it is like watching paint dry and you might get distracted at some point, or an emergency happens and you come back to a cooked (on fire?) pack...
BTW, where did you get your 36V charger? I have a 8s pack and need about 34V charger while I only have 48V units. Turning them down to 34V is OK but they do not go much lower or start hiccuping, so I can't charge an empty pack with those.

I have 2 36v chargers from ping. They both can adjust up or down just like the BMS battery ones (I suppose). The 2.5 amp ping chargers are great in that I ca adjust them for 10s lipo or 12s lipo (62v max I think). :D
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Wed Feb 01, 2012 6:33 pm

wineboyrider wrote:I have 2 36v chargers from ping. They both can adjust up or down just like the BMS battery ones (I suppose). The 2.5 amp ping chargers are great in that I ca adjust them for 10s lipo or 12s lipo (62v max I think). :D

Sounds good. I guess they can't adjust down to 24.5V for the other bike?

Thanks for the reference - I asked around at work and an IT guy told me that he was getting rid of 2 drawers of laptop chargers, except the newer ones.
Fine with me - I rummaged around and came up with a 15V Toshiba charger and a 19V HP charger. In series that is 34V, exactly what I need.
I know that these supplies are already current limited and will handle overload reasonable well, so I think I have found my "charger" for free ;-)
Now I only need to build a BMS and a Charge Controller to throttle back the current once a cell gets around 4.25V (LiPo pack). Zephyr sounds good, though I have not seen a schematic of the charge control part yet.
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Re: Fechter's Mini Meanwell Limiter Board

Postby fechter » Thu Feb 02, 2012 9:26 am

I'm reviewing the design of the mini limiter board now.

It looks like by adding 2 resistors and a transistor, I can make an interface for CellLogs or HVC boards that will drop the charge current to zero when active. These parts can be left off the board for those who don't need this function.

Does this sound like a useful feature?

Another thing I'd like to test is to replace the output diode with a red LED and see if it is bright enough to see. This would provide the diode function needed in addition to indicating when the limiter was active. My guess is the LED would light up during bulk charge getting gradually dimmer as the pack approaches the CV point, then go out. This would give a visual indication of when the pack was done.
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Re: Fechter's Mini Meanwell Limiter Board

Postby wineboyrider » Thu Feb 02, 2012 9:48 am

cor wrote:
wineboyrider wrote:I have 2 36v chargers from ping. They both can adjust up or down just like the BMS battery ones (I suppose). The 2.5 amp ping chargers are great in that I ca adjust them for 10s lipo or 12s lipo (62v max I think). :D

Sounds good. I guess they can't adjust down to 24.5V for the other bike?

Thanks for the reference - I asked around at work and an IT guy told me that he was getting rid of 2 drawers of laptop chargers, except the newer ones.
Fine with me - I rummaged around and came up with a 15V Toshiba charger and a 19V HP charger. In series that is 34V, exactly what I need.
I know that these supplies are already current limited and will handle overload reasonable well, so I think I have found my "charger" for free ;-)
Now I only need to build a BMS and a Charge Controller to throttle back the current once a cell gets around 4.25V (LiPo pack). Zephyr sounds good, though I have not seen a schematic of the charge control part yet.

Actually I think the 24v charger is different as I tried to trim the voltage down and the lowest I got was 34volts. But, other ES members say the BMS battery chargers can be trimmed (adjusted) up or down? Since I want a faster opportunity charger anyways and the price is right I decided to go ahead and order one set for 24.5v. :D :D
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Re: Fechter's Mini Meanwell Limiter Board

Postby NeilP » Thu Feb 02, 2012 10:36 am

fechter wrote:It looks like by adding 2 resistors and a transistor, I can make an interface for CellLogs or HVC boards that will drop the charge current to zero when active. These parts can be left off the board for those who don't need this function.

Does this sound like a useful feature?



Useful, yes, I have jus ordered a pair of Cell Logs, so using them instead of building extra in to the circuit would be a good thing. Just to be clear, this is a re design of the single pot or the three pot board?
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Re: Fechter's Mini Meanwell Limiter Board

Postby teklektik » Thu Feb 02, 2012 11:19 am

fechter wrote:... It looks like by adding 2 resistors and a transistor, I can make an interface for CellLogs or HVC boards that will drop the charge current to zero when active. These parts can be left off the board for those who don't need this function.

Does this sound like a useful feature?

You betcha. Please also arrange for a free pad to pick up Vcc to facilitate twin lead hookup to outboard opto(s).

Also - many different flavors of DIY HVC circuits always seem to end up with a tiny annoying 'glue board' with little but some limiting resistors and paralleled optos. To minimize the PITA factor, I would gladly pay to get a three channel isolator board modeled to be driven with the CellLog alarm interface with maybe a standard 9 pin pcb balancer connector for 3 alarms and FMM limiter hookup. This is an embarrassingly simple board but it would provide a quickie plug and play solution where alarm isolation is an issue.
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Re: Fechter's Mini Meanwell Limiter Board

Postby fechter » Thu Feb 02, 2012 3:27 pm

teklektik wrote:Does this sound like a useful feature?
You betcha. Please also arrange for a free pad to pick up Vcc to facilitate twin lead hookup to outboard opto(s).



The CellLog and most HVC boards pull to ground when active, so I will have a ground pad and the HVC line is pulled up by a resistor (to 12v).

I have a layout for the CellLog isolator board. As you say, it is very simple. The real trick is to power on/off more than one at a time. To do this, a small multi-pole switch seems to be the easiest. A 4P switch could power 3 CellLogs and use the 4th pole to turn on the controller power for example. This is an entirely separate project though.
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Re: Fechter's Mini Meanwell Limiter Board

Postby teklektik » Thu Feb 02, 2012 4:33 pm

fechter wrote:The CellLog and most HVC boards pull to ground when active, so I will have a ground pad and the HVC line is pulled up by a resistor (to 12v).

Good - it wasn't clear what you meant by 'when active' (asserted low) so I was looking at an outboard Vcc+pull-up rather than onboard pull-up. I forgot the ground reference anyway, so you're still at two pads: signal and gnd.

fechter wrote:I have a layout for the CellLog isolator board. As you say, it is very simple. The real trick is to power on/off more than one at a time. To do this, a small multi-pole switch seems to be the easiest. A 4P switch could power 3 CellLogs and use the 4th pole to turn on the controller power for example.

Hmmm, I think you had more in mind than I did for this board - I was just going after the isolation and was leaving the CellLog power, etc to the DIYer because of packaging/use case variations.

For instance, in my case I have an onboard CellLog with each 8s2p Headway pack and CellLog alarm leads running out from the pack balance charger connector. The CellLog on/off business is in the pack. Adding a simple isolator to the multi-pack balance charger would allow it to slave a MW bulk charger + your new limiter. (To make this more idiot-proof, the existing CellLog switch in the pack could be paralleled with two jumpered pins in the balance cable M/F connectors so the CellLog would power up whenever the pack was connected to the balance charger.)

In another thread recently, a poster had gutted and mounted Vphreak charger boards as part of a combined bulk/balance charger. With everything already exposed, he could use this isolator board to pick up the Vphreak green 'charge complete' LEDs directly w/o using CellLogs at all.

I think this may be a case where 'less is more' but as long as it's all optional board population, it looks good :) .
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Thu Feb 02, 2012 6:10 pm

I plan to have the monitors switch off with the key switch (I made a little circuit with an opto), the only thing I see is that the cheaper copy of the celllog called BVM-8s does not seem to have an upper voltage limit, only a low voltage alarm and a cell-to-cell maximum delta alarm.
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Re: Fechter's Mini Meanwell Limiter Board

Postby Degull » Thu Feb 02, 2012 6:41 pm

fechter wrote:I'm reviewing the design of the mini limiter board now.

It looks like by adding 2 resistors and a transistor, I can make an interface for CellLogs or HVC boards that will drop the charge current to zero when active. These parts can be left off the board for those who don't need this function.

Does this sound like a useful feature?

Another thing I'd like to test is to replace the output diode with a red LED and see if it is bright enough to see. This would provide the diode function needed in addition to indicating when the limiter was active. My guess is the LED would light up during bulk charge getting gradually dimmer as the pack approaches the CV point, then go out. This would give a visual indication of when the pack was done.


You are taking an already useful board and making it better! Both those features would a great addition and well worth any wait!
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Thu Feb 02, 2012 7:15 pm

Hi Richard,
Lets do a quick calculation of the current through the LED-as-diode:
Suppose this is a 48V supply charging a 12s LiPo pack (so the supply is set to 51 for 4.25V per cell) and the pack is charging away at 4V per cell (48V).
The voltage divider for the OVP in the NES-350-48 is 44k Ohm fixed and a 2k + 1k pot. That means that the current through the LED must make up the difference between the 44k resistor at 48V output and at 51V output - this is the current at that point of charging.
The voltage across the resistor is 2.5V less than the output, so the current is (48-2.5)/44k respectively (51-2.5)/44k or 1034 and 1102uA, the difference being 68uA. I am not sure how bright a red LED is at this current level, but I doubt that it is more than a faint glow, hard to detect in daylight. It is two orders of magnitude smaller than typical LED current.

Also note that the LED will be OFF (zero current) while the charger is still blasting away at max current, only has reached its max voltage set point.
It may be easier and better to indicate end-of-charge when the output from the opamp falls below a specific voltage.
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Re: Fechter's Mini Meanwell Limiter Board

Postby fechter » Thu Feb 02, 2012 9:57 pm

Thanks for running the math on that. I can see that approach won't work.

What would work is to just drive the LED off the output of the op amp through a resistor. When limiting starts, the output of the op amp will be 2.5v plus about .6v for the diode, plenty to drive a LED. This will only take one extra resistor and the LED, both of which could be optional.
"One test is worth a thousand opinions"
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Re: Fechter's Mini Meanwell Limiter Board

Postby cor » Fri Feb 03, 2012 12:33 am

Correct. And instead of fading off while the charging is catching up to the max voltage set point, the output of the opamp stays at 2.5 + 0.6V as long as it is limiting the charge current, no matter the output voltage (if you have no or only little resistance between opamp and OVP point). Once the current limit is lifted because the pack has reached the max charger voltage and the charger starts tapering off, also the LED starts fading because the opamp output is representative of the current (amp'ed shunt voltage) so if you give the opamp a moderate gain as for example suggested by S.B.D. here:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=36114&start=45#p528393
then you will see the LED not completely go off as soon as the current limit ends, but instead it will slowly fade with the current falling, for example it is at max brightness when the opamp output is 3.1V (for example representing 7A as with a NES-350-48) and extinguish when the charge current falls to about 3A (1.3V on opamp output)
Of course you can add one more resistor from LED to +Vcc and have the LED stay on a little longer, for example extinguish completely by the time the output current goes to zero. This pull-up also helps with the max current sourcing capability of the opamp. Luckily super-bright LEDs only need a few mA.
To get this effect, at the moment that the opamp output hits 0V you want the resisor divider from opamp via LED to +Vcc to present about 1.3V on the LED, so if the Vcc is 12V and you use a 1k resistor to drive the LED then you want about 8k2 to +Vcc. This last resistor is essentially a current source that continuously injects 10.7V/8k2 = 1.3mA into the LED. The opamp can add to it (when limiting it will be about (3.1-1.3)V/1k = 1.8mA sourced) or subtract from it, at 0V output the opamp is sinking all of the 1.3mA so there is nothing left for the LED.
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