Quick (bulk) Charge vs CC/CV (balance) charge?

[sonnetg]

Hello,
Is there any harm done by charging your batteries using cheap chinese chargers for a quick charge? I currently use 36V (10S4P) packs, which does not have any built-in BMS (pack is home made). I normally charge these packs with iCharger 1010 to balance charge, but it takes much longer to charge than the bulk 4A/36volt li-ion charger, which I bought from Luna Cycles.

With the Bulk charger, I notice the packs are not charged evenly, and often the ( new Samsung 25R) cells can be off by 0.05 Volts. While this is not really an issue, but am I damaging the cells in the long run?

I also notice many users here use Power Supply to bulk charge, which obviously does not have the CC/CV charge algorithms. So what is the difference between using a cheap bulk charger/power supply vs using a decent charger like iCharger or a top of the line charger like Grin Satiator?

Has anyone here have experience using both methods of charging? Would it be worth investing in a high end charger like the Satiator? Or I should be ok with using cheap chinese chargers to bulk charge?

Any feedback would be greatly appreciated.

Thank you

 

[Alan B]

A good supply for charging (like the LED power supplies) has CC/CV just like a charger. What it doesn't have is automatic shutoff, which is not critical if the voltage is properly regulated.

 

[Jon NCal]

Why is the 4A charger faster than the icharger, which should be able to do 7A?

 

[sonnetg]

Why is the 4A charger faster than the icharger, which should be able to do 7A?

I haven't pushed the iCharger over 5A, but given these chinese chargers specs, I doubt it is 4A. It could be more. I notice the 110V power cord slightly heats up on the chinese charger. My 10Ahr battery charges up withing an hour, but the iCharger takes almost 1.5 hr or more to charge. I suppose it could be due to CC/CV (trickle charge?) phase, but I am not sure. Most of these cheap chargers may not even have the CC/CV phase built in, but I could be wrong. I wouldn't be surprise if these cheap chargers are nothing more than a power supply.

I am really planning on investing in a Grin Satiator, but it is not cheap. Wonder if it would be worth investing in on of these fancy chargers...

 

[Jon NCal]

If your cells are not balancing, it's best to use the balance charger. The reason it takes longer is that the amperage tapers down as the voltage gets close to the end voltage. On the icharger screen you can see the real time voltage and amperage, as well as the cumulative watt hours. You would probably see over the last 15-20 minutes of charge there is not a lot of watt hours going in. It will shut off when your preset low amperage level is reached.

I believe the cheap 4A charger also has a setting for the low amperage limit it will shut off at.

The Satiator is not going to be able to balance charge, so what's the advantage?

 

[danielrlee]

CC/CV is neither a 'function' or 'feature' that has to be built in, but more circumstance of the way a regulated power supply works. When a battery has taken enough energy to reach the termination voltage of a charger/power supply, the charger no longer needs to sink the same amount of current into the battery to maintain the voltage, so the current automatically tapers to zero at which point the charge is complete.

 

[flat tire]

Most bulk chargers are actually CC / CV. That has nothing to do with balancing, which just makes each cell the same as the other cells.

I didn't balance my pack for the first couple dozen rides, didn't have any issues. I always balance charge now just because I have a fast charger (i3010b) and it's easy.

 

[Alan B]

Most power supplies are not CC. They are CV of course. Supplies do have protection for overcurrent, but it is generally a hiccup mode for short protection which is not useful for charging batteries. They will usually deliver more current than their ratings into a battery (not a short), and fail when they overheat. Only supplies that can safely limit their current are suitable for charging.

Often folks take a CV supply and modify the circuit to add a CC feature.

 

[sonnetg]

Ok...just to be clear, I am not really concerned about balancing the pack during each and every quick charge. I usually use the icharger once every few months to fully balance charge the pack. Theoretically, these cells should self balance (These cells were all new and of the same batch), but after few months of usage, the cells do get unbalanced when using the bulk charger. I can see the individual cell clusters deviate up to 0.1 volts. That is when I balance the pack using iCharger 1010. It works fine for another month or so before it gets out of balance again. The cells are a year old, but haven't seen much usage. Probably 50-60 cycles or so.

I am not sure whether the 0.1v deviance of some cells clusters would fall under normal wear or tear, or if this is indicative of something not right in my setup.

As for trickle charge, I see no indication of the generic luna cycle charger cooling down even when the pack reaches 41 volts. Normally on my iCharger, I can see the current drop to trickle charge and the power supply alsos cool down significantly when the pack reached 41 volts, but that's not the case with my generic bulk charger.

The luna cycles charger output is also 42 volts, so maybe it needs to hit 42 volts to trickle charge? I normally dont charge the the pack over 41 volt, so maybe my cheap charger never reaches the CC or trickle charge stage. I think that may be it...time to invest in a charger which can limit the charge to 90%. I think I just answered my own question

Thank you..

 

[Alan B]

A CC CV charger won't enter CV mode until it reaches end voltage, until then it will be CC.

When you interrupt a CC charger early you are not allowing balancing to occur.

0.1 volt imbalance is huge. You mention a 0.5V difference, which is very large. My lipo packs are much better balanced than that after a year of bulk charging and no balancing. Are you sure these are good cells?

If you want to bulk charge to 41V then get set up for that - adjust it or get a 41V supply. Don't interrupt a bulk charge early on a regular basis. Your charge state will be way below 41V for one thing.

 

[sonnetg]

A CC CV charger won't enter CV mode until it reaches end voltage, until then it will be CC.

When you interrupt a CC charger early you are not allowing balancing to occur.

0.1 volt imbalance is huge. You mention a 0.5V difference, which is very large. My lipo packs are much better balanced than that after a year of bulk charging and no balancing. Are you sure these are good cells?

If you want to bulk charge to 41V then get set up for that - adjust it or get a 41V supply. Don't interrupt a bulk charge early on a regular basis. Your charge state will be way below 41V for one thing.

Yeah...it makes perfect sense. I am not sure why these cells are getting out of balance. Even a 42 volt charger should charge all the cells evenly up to 41 volts, but that is not the case with these cells. After a month of using the bulk charger, some cells charge fast up to 4.1 volts, while few other clusters are still at 4.0 volts. Charging with an iCharger fixes this and I can get a good balanced charge using a bulk charger for a month or so before the balance gets out of whack again. Maybe some cells were damaged while soldering the leads or balance wires, but i really dont know for sure.

I think i will shop around for chargers which can limit the charger output. It's doesn't have to be a satiator, but 36 volt chargers can be hard to find. I need to shop around a bit. Hopefully that will help getting a good even charge even with a bulk charger. I will update the forum if thats help address this issue.

Thank you,

PS: I meant 0.05 volts, not 0.5 volts. I edited my first post now. Thanks for catching this..

 

[Alan B]

0.05 is a lot, but not a problem.

Balance charging once per month is frequent, but not a big problem to do.

I would use a Meanwell LED supply for your project. Either the 320 or 240 watt versions. They are adjustable for current and voltage. They are high quality, potted, silent and UL listed. HLG series. They come in various voltages, and have a range of adjustability.

They generally have 5 year warranty.

HLG-320H and HLG-240H are 320 watt and 240 watt models

Both are available in 42V models that are adjustable to lower voltage

 

[sonnetg]

Thanks Alan, but I am looking for a 41 volt bulk charger. I have looked at various sources, but my options seem to be very limited. I think the best option would be to invest in a Satiator in the long run. Meanwhile I can use the iCharger 1010 for the time being.

Hopefully charging the cells at 4.1V would help double the life of my pack.

Cheers,

 

[Alan B]

The Satiator is an Excellent choice. It has wonderful readouts and great user adjustability.

But exactly how is it different from an LED supply?

If you are using the reprogrammability or the data the Satiator provides, these are advantages. Cheap bulk chargers don't have these features, so I presume you aren't seeking them.

If you think the Satiator works differently as a charger, that is not the case. The Satiator continues to output voltage after it says "charge complete". Exactly like an LED supply does. This is to allow the BMS to balance the cells. The Satiator is designed with the assumption there is a BMS on the battery. Regular bulk chargers shut off after the charge current tapers off.

The Satiator is a pushbutton/display adjustable CC CV supply with a good user interface. The LED supplies are screwdriver adjustable, over a smaller range, at less than half the cost, with longer warranty.

I have and use all these systems.

I also have a few of the cheap bulk chargers. So far 50% of my BMSBattery bulk chargers have failed, and I haven't used them that much. Zero of the LED supplies have failed, and I have more of them and use them more. Some large manufacturers use the LED supplies in their battery chargers. It is a good commodity component for this.

 

[sonnetg]

Hey Alan,

I had no idea the Meanwell power supplies were adjustable. If that is the case, I have no need for the Satiator, as most of my packs are limited to 36 Volts. The Satiator would be great if I had a wide range of batteries to charge.

Thanks for all the suggestions. I think it would be worth trying out the Meanwell power supply. Any links to reliable source would be great.

Thanks so much.

 

[Alan B]

I bought mine from PowerGate Express which has been bought by power.sager.com since then. If you search for HLG320 you'll see a few sources pop up. Compare prices.

Searching for HLG320 shows 3 pages of different voltage range models there:

https://power.sager.com/search/?Keywords=hlg320

The 42 volt model is here:

https://power.sager.com/hlg-320h-42-2525474.html#dvSpecifications

It says it adjusts from 21 to 42 volts, I have the 24V models and I don't recall the adjustment range. Download their detailed spec sheet for manufacturer's info.

The constant current is adjustable from about 50% up to the full 7.65 amps.

Like the Satiator these are not lightweight, they are alloy cases and fully potted for ip67 moisture resistance. They cool through their exterior so they get warm, but not hot, however they do need free air to stay cool. They are designed to power large scale LED lighting systems.

The two black discs on the front panel are rubber covers, there are trimpots well down inside those holes on the PC board that you can adjust for voltage and current.

I have a thread here on ES about the charger I made using three of these supplies. 1KW at 75 volts for my 18S 66V 32AH Borg. This charger puts out over 12 amps.

The 240 Watt models used to be the most watts/dollar and the least weight/watt, but they do run a bit warmer and produce less current and are about half the size and weight. They have other sizes as well but verify that any unit you are interested in has the variable voltage and constant current, some models are different.

There is also a newer 600 watt unit, last time I checked that one was both heavier and more costly per watt than some of the others, but it was new.

Make sure whatever you select produces a current level that your batteries are rated to accept. Keep well below the max charging rate for long battery pack life. I would not go over 1C and preferrably less than 0.5C.

 

[sonnetg]

Thank you Alan. Do you have a link to the thread?

If I am not mistaken, lithium charging has several charging stages, which include CC, CV and Saturation stage. Wouldn't a power supply bypass all these phases and possibly damage the cells in the long run?

I was reading the following articles on lithium charging:

http://www.digikey.com/en/articles/techzone/2012/nov/constant-voltageconstant-current-devices-optimize-li-ion-battery-charging-for-energy-harvesting

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

I suppose there aren't any long term test data available on charging lithium with a power supply. Most users seem to be more concerned on quick charge and maximum capacity rather than longevity. I might save up and invest in a Grin Saturator. The Saturator seems to have nice features which provide a good insight on battery health and charge state. Measuring SoC by voltage alone can be misleading. Monitoring the current is crucial.

 

[Alan B]

The One Kilowatt 18S Bulk Charger thread is here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=42169

I was going to build a fancy monitoring system for cell voltages, etc. into that charger but it worked so well that I never bothered to. I used it every day for years, now that I don't need to commute to work (retired) it doesn't get as much use. But it is a solid charging setup.

You may be thinking of lead acid charging which is actually more complicated than Lithium charging. Also, many of these "phases" are talking more about what is going on chemically in the cell, while the charger is just putting out CC then CV.

There are some lithium fast-charge regimens where they use a higher current early in the charge cycle at lower state of charge than the battery will safely accept at higher SOC (Tesla for example), but generally chargers just stay under the safe current for the whole cycle and avoid this complexity. This is only needed for really fast charging, and it may shorten the life of the cells. Charging at more modest current is preferred if you have the time. My regimen was to bulk charge fast at work (12A into 20AH, later a 32AH pack), and then bulk charge at home at 2 or 4 amps, and monitor the balance weekly or anytime there was any question, like a deep discharge event. Balancing once or twice per year was adequate for the packs I was using.

The only thing many bulk chargers (but not all) do is to shut completely off when the current drops below some value like 5 or 10% of the amp-hour rating of the pack. You don't want to let the pack cook for days at full charge voltage on the power supply, the current will drop to negligible levels but ideally for best life you don't want the pack sitting at the full voltage, either on the charger or just sitting. It is best for pack life to charge "just in time" and then immediately discharge the pack down to storage level.

I note that some of the new drone battery BMS's will, after a few days (or a week or two) sitting at full charge, automatically drain themselves to storage level. It is an interesting idea that we haven't seen in ebikes yet that I know of.

Cars manage their packs with more sophisticated BMS systems, and with the large battery investment they should and can. Ideally you tell the vehicle what range you need and when, and it waits and charges just enough, just in time and takes maximal advantage of the off hour rates, and has just enough above storage level to take care of your planned transportation needs plus some margin.

 

[danielrlee]

If I am not mistaken, lithium charging has several charging stages, which include CC, CV and Saturation stage. Wouldn't a power supply bypass all these phases and possibly damage the cells in the long run?

I hope this doesn't sound rude, but you have been given the answer to your question a few times already. CC/CV is not a special feature, but rather a natural phenomenon of any regulated power supply that features current limiting.

When you connect a lithium battery to a charger (or power supply), the charger will immediately sink current into the battery at whatever rate the charger is set to (CC phase). This causes the voltage of the battery to rise. As energy is stored by the battery, the voltage continues to rise until it reaches the the output voltage that the charger is set at. At this point, the charger no longer needs to sink voltage at its maximum rate to maintain this upper voltage, so it starts to taper down the current it outputs (CV phase). The current continues to taper down to zero as the voltage of the battery equalises to the output voltage of the charger. At this point no current continues to flow since there is no longer any voltage differential between the charger and the battery. It is at this point that the charge is considered complete.

If you wish to spend big money on a Satiator, please do. It is a fantastic charger that will provide you with lots of information and many years of reliable service. Do not however think that it will charge your lithium battery any differently to any other current limited regulated power supply.

 

[motomech]

Two thumbs up on the MeanWell HLG series, best money I have spent on Ebiking.
No more cheap and finicky RC balance chargers :lol:
I originaly set my HLG up w/ a high-Voltage alarm and a timer to shut it off, but removed them, as they were not needed.
All that is needed is a voltmeter to set the End of Charge value.
My 320h is way faster than a balance charger of the same rating(7 Amps @ 48 V). Balance chargers are forevercycling on/off to read the cell values.
I ck. and balance w/ Battery Medics;