New lipos arrived today, but some aren't balancing correctly

[Baron]

I ordered ten lipo bricks from hobbyking, specifically these ones: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=58976
I'll be using them in a 20S2P config on my bike.

They arrived at around 3.85V per cell. I started putting them on the charger a few hours ago. So far I've gotten through four of them, two have charged/balanced perfectly but the other two have had some problems. For example, one bad pack had the following voltages:

Starting voltage:
3.80
3.81
3.84
3.80

Ending voltage:
3.98
4.03
4.09
3.97

The cells are wildly out of balance in that particular pack. Even before I charged them they were slightly unbalanced.

I'm using the balance function on my charger, an Imax B6 50W. Only charging to 4.10V rather than 4.20. I made sure that all connections are good, you can't really mess it up, there's only + and - terminals and the balance leads.

This is my first time using lipo, but i've used this charger on li-ion 18650 before (in parallel and series configs) without a problem.

So what should I do next?
Contact hobbyking and return the faulty packs?
Try to charge the low voltage cells individually, using the balance leads to isolate particular cells?
Run them through a charge/discharge cycle and see if they correct themselves?

 

[wesnewell]

Are you sure you did a balance charge? You can charge without balancing on that charger. Try to charge that pack again and make sure you use the balance charge. If it still won't balance, then it's probably a bad pack.

 

[dnmun]

balance is the storage of equal amounts of charge in each cell. the fact that your charger will not charge all of the pouches up to full charge does not mean they cannot be balanced. charging to full charge is the first step. this has not been done.

 

[Baron]

Update: I left a pack on the charger overnight and it seems to have balanced correctly. However, it took over 600 minutes. Looks like some of the packs get up to the end of their charge and take a really long time to balance. The charger is supplying 0.1 amps or less during this time so that explains why it takes so long. Does this mean they're bad packs, or is this common with lipo packs?

I'll be putting each pack through a discharge cycle so I can see if any cells really are out of balance. Anything else I should look out for? Remember, lipo noob here.

I need to have all the cells in each pack be roughly equal because I'm going to try bulk charging them with a harness, at least until I can find a better charger.

Are you sure you did a balance charge? You can charge without balancing on that charger. Try to charge that pack again and make sure you use the balance charge. If it still won't balance, then it's probably a bad pack.

Yes, I am positively using the balance charge function of the charger. Although I am using the li-ion mode rather than the lipo mode because I only want to charge to 4.10V.

 

[wesnewell]

From looking at the starting voltages I'd say it's not a well balanced pack. I'd try running a few cycles on it. If it still takes 10 hours to balance I wouldn't use it in a larger pack. A well balanced pack should balance within minutes of the end voltage, assuming the charger is balancing while it charges as does my Hyperion 1420i. Although I've got a B6, I don't use it and don't know if it balances during charge or only at the top.

 

[dnmun]

Update: I left a pack on the charger overnight and it seems to have balanced correctly. However, it took over 600 minutes. Looks like some of the packs get up to the end of their charge and take a really long time to balance. The charger is supplying 0.1 amps or less during this time so that explains why it takes so long. Does this mean they're bad packs, or is this common with lipo packs?

I'll be putting each pack through a discharge cycle so I can see if any cells really are out of balance. Anything else I should look out for? Remember, lipo noob here.

I need to have all the cells in each pack be roughly equal because I'm going to try bulk charging them with a harness, at least until I can find a better charger.

Are you sure you did a balance charge? You can charge without balancing on that charger. Try to charge that pack again and make sure you use the balance charge. If it still won't balance, then it's probably a bad pack.

Yes, I am positively using the balance charge function of the charger. Although I am using the li-ion mode rather than the lipo mode because I only want to charge to 4.10V.

set your charger to charge the pouches up to full charge @ 4.20V.

 

[Alan B]

This isn't a fast balancing charger, it takes a long time to balance a pack due to the way it works. New packs take awhile to balance and get settled in.

It will probably get faster as the pack is closer to balance to start with.

Precise balance doesn't matter much, a few millivolts doesn't make a difference. So don't be too concerned about it.

The BC168 type chargers balance much more quickly.

These are also very low cost Lipo packs, they tend to have more problems. Keep a close eye on them and cull any that misbehave, such as any that consistently take a lot longer to balance.

 

[Hillhater]

Yep, just needs more balancing. Either automatically on the charger, or manually.
#3 cell obviously had a higher SOC before you started,..

 

[Baron]

set your charger to charge the pouches up to full charge @ 4.20V.

I will try that, but most are performing perfectly charging/balancing at 4.10V. Just having a few problem packs

From looking at the starting voltages I'd say it's not a well balanced pack. I'd try running a few cycles on it. If it still takes 10 hours to balance I wouldn't use it in a larger pack. A well balanced pack should balance within minutes of the end voltage, assuming the charger is balancing while it charges as does my Hyperion 1420i. Although I've got a B6, I don't use it and don't know if it balances during charge or only at the top.

it's not a well balanced pack You can say that again. I just put a pack on the charger which had starting voltages of 3.84, 3.75, 3.84, 3.85. That low voltage cell will obviously take a lot longer to charge than the others. I expect it to be on the charger all night again...It's currently sitting at 4.09, 3.90, 4.10, 4.09 and the charger will only allow it to charge at around 0.1 amp as it balances.

Precise balance doesn't matter much, a few millivolts doesn't make a difference. So don't be too concerned about it.

I'm just hoping the individual cells actually hold the same capacity, but hobbyking just sent them to me out of balance. If I can get all the cells balanced, do a discharge test on them, and have them all come out within 0.01V of each other, then I will be a happy man. I have tested 3 good packs so far and they've passed with flying colors.

 

[Ykick]

Make some pin leads and charge each cell individually 1S through balance connector.

 

[neptronix]

Imax B6 isn't known to be the most accurate charger in the first place, but that's pretty off.
The turnigy hardcases are known to be not the best lipos either.. ( there's a reason they are so cheap )

A quality graphing charger can tell you the truth about these packs.. instead of making best guesses with questionable hardware.

Why'd you only charge to 4 volts?
Are you sure you did an actual balance charge in the first place?

 

[dogman dan]

Actually, within .1v is balanced enough in my world, although I see .05 off a lot more commonly.

I agree with the others above, mostly it's just that the first few cycles tend to need more balancing, and that charger is crazy slow. The idea to single cell charge, or discharge, can balance you up much faster. That's how I do it most of the time now. 90% of my packs will not need any balancing, so I just go after the few cells that do.

But you might have a wonky cell in one or more packs. I DO NOT BOTTOM BALANCE, but I do a LOT of my detecting shitty cells by seeing which one hits empty first. So run some cycles, and see if you find any cells with obvious under capacity. And of course, if any puff up, stink, self discharge, or get all hot when the others don't, dump them.

 

[Ykick]

btw, Here’s what I meant by “pin leads”: One of the more useful handy bits of fabrication I’ve experienced for "advanced" RC Lipo management.

Match the charger/load side to whatever connector ecosystem you use. Besides faster balancing you can do much more monitoring to detect excessive voltage sag under load, charge “bounce” = IR.

Capacities can and do vary and while not ideal I’ve found different IR’s can sometimes work in series strings.

However, the main thing I like to qualify is if I have a “leaker” cell. A cell that excessively self-discharges over a period of hours/days. Those are never good to use in any situation other than destruction porn.

If it hasn't been mentioned yet, register your warranty with HK. Then if/when you discover a dodgy cell and can provide data with a decent measurement process you stand a better chance of getting warranty replacement bricks.

I've personally had very good luck with the Turnigy 4S hardcase. I'm well over 40qty bricks in last 2-3 years and not one has been retired from service yet. Knock on cellulose...

 

[neptronix]

Actually, within .1v is balanced enough in my world, although I see .05 off a lot more commonly.

I agree with the others above, mostly it's just that the first few cycles tend to need more balancing, and that charger is crazy slow. The idea to single cell charge, or discharge, can balance you up much faster. That's how I do it most of the time now. 90% of my packs will not need any balancing, so I just go after the few cells that do.

But you might have a wonky cell in one or more packs. I DO NOT BOTTOM BALANCE, but I do a LOT of my detecting shitty cells by seeing which one hits empty first. So run some cycles, and see if you find any cells with obvious under capacity. And of course, if any puff up, stink, self discharge, or get all hot when the others don't, dump them.

.1v can be a dislabance of 10-20%, depending on where you are in the SOC.
That's a huge spread that limits your ability to discharge and charge without balancing safely.
My personal limit for a pack that will constantly remained disbalanced is more like 0.01v.

This is why i graph packs immediately upon arrival and shelf/return the ones that are underperformers. I want to get 99% of the capacity promised and no issues with bulk charging with a range of 3.5v LVC to 4.17v HVC over a long term..

There is no fun in constantly checking the balance, disassembling the pack, balancing it by hand, reassembling it, and worrying about it in the future. That makes your ebike a total pain in the ass to keep up.

This is why i am all about high cell count, high amp hour packs as well. In the event that you need to disassemble things and do balance-surgery ( which i prefer to do.. um.. NEVER ), you've got far less work to do and far less room for human error. Thus, the 8, 10, 12, and 16ah multistar packs really are the best choice.

 

[Baron]

btw, Here’s what I meant by “pin leads”: One of the more useful handy bits of fabrication I’ve experienced for "advanced" RC Lipo management.

Match the charger/load side to whatever connector ecosystem you use. Besides faster balancing you can do much more monitoring to detect excessive voltage sag under load, charge “bounce” = IR.

Capacities can and do vary and while not ideal I’ve found different IR’s can sometimes work in series strings.

However, the main thing I like to qualify is if I have a “leaker” cell. A cell that excessively self-discharges over a period of hours/days. Those are never good to use in any situation other than destruction porn.

If it hasn't been mentioned yet, register your warranty with HK. Then if/when you discover a dodgy cell and can provide data with a decent measurement process you stand a better chance of getting warranty replacement bricks.

I've personally had very good luck with the Turnigy 4S hardcase. I'm well over 40qty bricks in last 2-3 years and not one has been retired from service yet. Knock on cellulose...

I just used a similar method to isolate the low voltage cells in the unbalanced packs. Put them on the charger in single mode and got them balanced with the rest. Now the true test, to see if the packs stay in balance after a discharge.

Thanks for the help, everyone

 

[dogman dan]

Yes. .1v is at least 10%. But "in my world" 10% off does no real harm, since there is no way I'm charging to 4.2v on a non balancing charge. At worst, I'll see a cell get to 4.25v on a bulk charge. and stopping at 3.65 or so, no danger on the other end either.

But in practice, I never really see a cell get that far off, since I don't run them at 15c to 3.4v, like many do in RC use. My stuff sees perhaps 10c at worst, 5c more typical, and I'm very careful about going below 3.6v, because that does drive cells out of balance in my opinion.

For sure, I don't believe my cheap chargers, cellogs, or DVM's can measure to .01 v accurately. So I sure don't fret about .01 off.

What to really worry about, is any cell that just stubbornly goes out of balance .05v or more, every cycle, and gets worse the next cycle. That's a wonky cell. But if it drifts off .02v right away, no big deal if it doesn't continue to change. Watching my packs, some cells will just never hold the same top of charge voltage overnight as the others. But if it's small, and doesn't get bigger, it's nothing to fret about. You don't need to balance charge every night, to get that cell .02v higher every cycle. It's just a total waste of time.

 

[denver commuter]

I have 16 4s 5000mah that I use. I did not buy them all at the same time. I think I bought 9 and then bought 7 a month or two later. I run 4 packs in series and 4 in parallel for 60ish volts and 20 amps.
I have my Lyen set at 60 amps and 180 phase amps. I have seen 6100 Watts peak on the CA for a second. Voltage sag is about 2 volts under full throttle up a decent size hill.
The batteries all charge to within .002 of each other.
I say all this because I am having great success using the Turnigy hardcase 4s5000mah. As you can see I am not easy on them and they are still as good as the day they arrived. I checked them all when I got them and all were sitting right around 3.88 volts and in perfect balance.
So far they seem like a great battery for the money.
That being said I did have two positive wires break free from the battery's terminal. As soon as I get some stuff to solder aluminum I plan on fixing those two packs.
YMMV

 

[dnmun]

if just the wire came loose then you should be able to solder the wire back into the original solder with regular 60/40 solder. there should still be solder on the tab.

 

[Baron]

I got all 10 of my batteries balanced and they are performing perfectly. Strange how they were so out of balance when they shipped them to me though. Had me worried for a few days.

Semi-related, but I plan on running my batteries 20S 2P, permanently soldering the parallel packs together (see pic below). Is this safe to do? The process is this: First I'll balance charge the two 4s battery packs I'll be joining, check the voltages, then solder neg to neg, pos to pos, etc. balance wires too, thankfully they're color-coded. So in the end it will be a 10ah pack. then i'll wire 5 of these 10ah packs in series for 20s.

My main reason for doing this is because I don't have extra 4mm bullet connectors lying around to create a harness for each parallel duo pack, and I don't feel like waiting a week for them to come in the mail lol. Plus I'll gain 10 bullet connectors in the process which I'll use to create wires for the series connection/controller connection.

 

[dnmun]

I got all 10 of my batteries balanced and they are performing perfectly. Strange how they were so out of balance when they shipped them to me though. Had me worried for a few days.

Semi-related, but I plan on running my batteries 20S 2P, permanently soldering the parallel packs together (see pic below). Is this safe to do? The process is this: First I'll balance charge the two 4s battery packs I'll be joining, check the voltages, then solder neg to neg, pos to pos, etc. balance wires too, thankfully they're color-coded. So in the end it will be a 10ah pack. then i'll wire 5 of these 10ah packs in series for 20s.

My main reason for doing this is because I don't have extra 4mm bullet connectors lying around to create a harness for each parallel duo pack, and I don't feel like waiting a week for them to come in the mail lol. Plus I'll gain 10 bullet connectors in the process which I'll use to create wires for the series connection/controller connection.

batteries are shipped only partially charged with only the formation charge on them. you have to cycle them several times to get the full capacity created.

 

[mark5]

If you'll leave the balance cables separable you'll still be able to easily check cells or charge a cell on a single brick in the future. Use a parallel balancing cable to connect them together instead.

 

[dogman dan]

I've often connected the main wires like you are planning. Instead of solder, I just used a thing called a crimp sleeve, that I could get at a Lowes or Home depot store.

I leave the balance wires separate, so I can still easily check the balance of individual cells. Two schools of thought here, One is let one good cell support the weak one. my feeling was more like don't let the weak cell hammer the good one. I'd rather leave them separate at cell level, so if something is going on I know exactly which pack to get rid of.

Once I know which pack in the pair has the weakest cell, that's the one I put a low voltage monitor on if I need to discharge 100%. In fact, once I know which pack has the weakest cell, one LVM can monitor a pack that has 20 or more packs in it.

Think about it, once you know which cell, all the others don't really need monitoring. But nothing wrong with connecting the balance wires like you plan on if you feel like it. I just found no particular need to do the effort. With a cellog 8, you can check dozens of balance plugs very quickly.

 

[jimmyhackers]

is you IMAX B6 a genuine SKYRC one?

i.e when you turn it on does it say SKYRC? if not its a copy and may be suspect. i had a copy with dodgey balancing

also make you you charge current it set to above 1.2amps. you need at least 200ma per cell balancer

not quite sure how/why but i had a similar slow charge problem.... each cell can only be balanced at a max of 200mili amps. meaning once one cell is "full" it will only put max 200ish milliamps through ever other cell.

basically it was really slow then i upped the amperage then it got a little faster.

its also worth noting that when i take any of my batteries off charge and check individual cell voltages there always about 0.01-0.02v under the full 4.1v. i figure this is an inbuilt saftey thing the manufacturer put in to make sure their chargers blow up less batteries.

you can experiment with the calibration function in old imaxb6's to get this up to the desired "correct" finish voltage.
and with the new mini imax b6's you can make a new "charge profile" to finish at 4.12vs and they should finish up around the desired 4.1vs

 

[dnmun]

that is not true. if the balancing current is only 200mA then your charger will need only 200mA to balance the pack.

the reason the voltage drops after removal from the charger is because of the internal resistance of the cell to charging that creates a voltage drop from the charging voltage to cell voltage.

 

[Baron]

I've often connected the main wires like you are planning. Instead of solder, I just used a thing called a crimp sleeve, that I could get at a Lowes or Home depot store.

I leave the balance wires separate, so I can still easily check the balance of individual cells. Two schools of thought here, One is let one good cell support the weak one. my feeling was more like don't let the weak cell hammer the good one. I'd rather leave them separate at cell level, so if something is going on I know exactly which pack to get rid of.

Once I know which pack in the pair has the weakest cell, that's the one I put a low voltage monitor on if I need to discharge 100%. In fact, once I know which pack has the weakest cell, one LVM can monitor a pack that has 20 or more packs in it.

Think about it, once you know which cell, all the others don't really need monitoring. But nothing wrong with connecting the balance wires like you plan on if you feel like it. I just found no particular need to do the effort. With a cellog 8, you can check dozens of balance plugs very quickly.

I've decided to just buy more 4mm bullet connectors to create harnesses because it was taking too long to solder together all wires like in my pictures. Plus, like you described, I'd like to monitor my batteries more closely in the first few cycles to catch any duds. I'll probably leave the balance connectors separate too and just get a boat load of balancing harnesses for them.

is you IMAX B6 a genuine SKYRC one?

It may very well be a copy but it's working as intended now that the cells are balanced. I put the charging setting at the maximum 5A but the charger would only allow up to around 3A for a single 4S pack, being a 50W charger.
Now that they're balanced, most packs are done in as little as 75 minutes from empty.