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Quick way to balance lipos

Old 01-01-2016, 10:47 PM
  #1  
smitty4980
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Default Quick way to balance lipos

I'm fairly new to battery charging and watched this video on you tube about charging a single cell in a multi cell battery to balance it quicker. It looked pretty reasonable to me until he showed how to charge any particular cell by moving his adapter to whichever cell you want to charge. Now I'm far from being an electrician but wouldn't one pin always have to be in the black wire hole? To charge the second cell wouldn't he need to make another adapter that would span three holes with the middle pin removed, and for the 3rd cell a wider adapter that would span four holes with the 2nd and 3rd pins removed?It seems like if he moved the adapter around like he shows in the video he would end up connecting positive to positive on all but the first cell. Am I missing something or is he? https://www.youtube.com/watch?v=wIbHLacozFo

Last edited by smitty4980; 01-01-2016 at 10:49 PM. Reason: Add link to video
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Old 01-01-2016, 10:52 PM
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solentlife
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No because the balance plug pairs pins to give individual cells. The outer pins give total pack voltage.

Take a multi-meter and you will see exactly what I mean.

Nigel
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Old 01-01-2016, 10:59 PM
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kyleservicetech
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I've done this myself. One big risk is getting the polarity backwards!

Before buying my two Cellpro Powerlab PL8's I made up a charger that individually charged each cell on an A123 pack to exactly 3.60 Volts DC. Still have it, still works. I've also learned to never do that again! The Cellpro charger is so much easier.

Last edited by kyleservicetech; 01-01-2016 at 11:36 PM.
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Old 01-01-2016, 11:01 PM
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Not going to even watch the video...

Fastest way to balance is to finish charge each cell separately to 4.20 v. That way you can do it at max rate of the charger for the pack.
Charge the whole pack slightly short of 4.20 v/cell.
Then one at a time peak each cell to 4.20 v.

I only know of one charger that does this automatically... and it is discontinued.
Turnigy 420 charges through the balance port , switch selectable .5 amp to 2.0 amp rate and it treats each cell as a separate battery. So... it simply stops charging each cell as it hits 4.20 v.

Everything else... (that I have seen) balances by discharge.
When the charger would stop the charge if it wasn't set to balance, it checks balance, discharges any high cell(s) and then charges again... repeat until all are 4.20 v.
The discharge is at some lower rate than the charge (often 200 ma) and just one cycle of this can add several minutes to the balance charge.

To manually change from cell to cell to peak them off... you have to make an adapter cable and plug in the balance port.
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Old 01-01-2016, 11:02 PM
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I just tried the multimeter on a three cell and you are absolutely correct. It never hurts to verify something before taking a chance and screwing something up. Thank you!
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Old 01-01-2016, 11:10 PM
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While I'm at it and there are some people in the know here, I understand the balance charge but I can't figure out what the difference is between lipo charge and fast charge. It seems like they are the same thing. Same thing with storage and discharge. What's the difference?
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Old 01-01-2016, 11:16 PM
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Fast charge (for LiPo) skips the balance at the end.
Older chargers default to no balance at the end and you have to manually tell it to balance.

Discharge will take the pack down to 3.2 v/cell... or 3.5 v/cell 9depending on the charger and how it is programmed)

Storage will charge OR discharge to the set storage voltage which is typically between 3.7v/cell and 3.8v/cell

Since different chargers label the same thing differently.... some may do it slightly different...
But this is the basic idea.
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Old 01-01-2016, 11:22 PM
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Do you always plug in the balance plug or is it only plugged in for balance charging ?
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Old 01-01-2016, 11:28 PM
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Depends on the charger.. Some will let you charge without plugging in the balance plug if not set to balance charge. Some will not.
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Old 01-02-2016, 12:27 AM
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Originally Posted by smitty4980 View Post
Do you always plug in the balance plug or is it only plugged in for balance charging ?
If you don't connect the balance lead then you lose protections for individual cell over voltage which can lead to fires.

I frequently use fast charge but always connect the balance lead.
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Old 01-02-2016, 01:40 AM
  #11  
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Thank you all! I appreciate the help. Happy new year!
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Old 01-02-2016, 01:46 AM
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Note:

The chargers that let you get away with the balance lead unplugged... might not offer any protection for a single cell being out of expected range in the mode where the balance plug being disconnected does not produce an error.

The way the charger detects if the balance plug is connected is by detecting individual cell voltages...
You already have proven that its not checking for a cell being out of tolerance low if it doesn't error out due to the balance lead being unplugged.
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Old 01-02-2016, 02:19 AM
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This is not really an area to "tinker" in without explicit knowledge. Get a good charger, suitable power supply and just follow the instructions.

I second the advice of using Cellpro/FMA products.

Power Labs actively balance from the start of charging.

From what I understand, the balance plug is only suitable up to 2 amps.

The key here is listed in that videos title "(and this is how cheap chargers work)"

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Old 01-02-2016, 02:59 AM
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I got a HiTec X4 AC/DC multi charger for Christmas. The directions tell you what to do but aren't real clear so I watched several videos on you tube which cleared up a few things. An example of that is the three modes of charging: charge, balance charge, and fast charge. I got a real good explanation of balanced charge and how it works. Charge and fast charge sound like they are the same thing although I would assume there is a difference since they are separate options. I'm using 1000mAh 3 cell/3s
11.1V lipo battery. 1C is 1.0A. To fast charge do you increase the 1.0A or is that the max that should ever be used?
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Old 01-02-2016, 03:13 AM
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That's a good charger. Fast charge just stops the charging and sounds the "done" alarm earlier. " Reduces charging time, but does not balance the cells, this mode only charges the battery to approximately 90% capacity."

Balance is what you should always use if you have the time.

Storage charge brings all cells to 3.7-3.8 volts. Often when I return from the field I throw a storage charge on the packs, not knowing when I will go out again.

1c is a safe rate and will, from what I understand, give you the best longevity from your packs.

You can check with your battery manufacturer specs. Some batteries advertise 5c-6c or more charging capabilities. I still like to stay as low as time permits.
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Old 01-02-2016, 03:36 AM
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Its also possible to store in the charger's memory different charge rate and cell count values for the "normal" vs balance charge for the chargers I have (which includes a Hitec X2-400... which doesn't have the "Fast charge" option)

That might be an option for how to use the charger... setting a higher rate on the Fast charge setting vs the normal and balance charge rates... making it a REALLY fast charge, since normally its a good idea to charge at 1C rate, but most modern LiPos can handle 2C charge rate or higher.
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Old 01-02-2016, 09:39 AM
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Originally Posted by smitty4980 View Post
While I'm at it and there are some people in the know here, I understand the balance charge but I can't figure out what the difference is between lipo charge and fast charge. It seems like they are the same thing. Same thing with storage and discharge. What's the difference?
Charge - is to 4.20V but no balancing.
Fast Charge is to slightly lower final voltage with no balancing.
Storage balances all cells to set storage level.
Discharge just discharges all cells to set voltage usually lower than storage

Nigel
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Old 01-02-2016, 02:50 PM
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Originally Posted by solentlife View Post
Charge - is to 4.20V but no balancing.
Fast Charge is to slightly lower final voltage with no balancing.
Storage balances all cells to set storage level.
Discharge just discharges all cells to set voltage usually lower than storage

Nigel
Regarding storage and discharge.

As Nigel says, 'discharge' fully discharges the battery all the way down to it's lowest safe voltage, typically around 3.5V per cell. You would normally only use that option if you wanted to discharge the battery prior to disposal.

'Storage' takes the battery to optimal storage voltage, usually in the 3.8-3.85V per cell range. It will either charge or discharge the battery to that voltage depending on if it's starting voltage on connection is lower or higher. Most chargers dont by default balance in storage mode. There isn't really much point because the battery will get balanced on the next charge cycle.
Some chargers do have the option in the setup to balance in storage mode but in my experience by default they dont balance.
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Old 01-02-2016, 08:01 PM
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Originally Posted by birdDog View Post
This is not really an area to "tinker" in without explicit knowledge. Get a good charger, suitable power supply and just follow the instructions.

I second the advice of using Cellpro/FMA products.

Power Labs actively balance from the start of charging.

From what I understand, the balance plug is only suitable up to 2 amps.
Good advice

Buy the best charger you can afford for charging these LiPo battery packs. As for me, I've got a pair of Cellpro PL8 chargers. The design of these chargers checks the voltage of the balance cable and compares that to the voltage on the power cable. If they don't match, or if anything is wrong with the voltages on the balance cables, the charger shuts down with an error.

In this day and age, with the availability of high quality balancing chargers, I'd NEVER charge any LiPo battery pack (Or A123 for that matter) without having the balancing function in place.

I'm charging my A123's at 20 Amps for a 6S2P pack. If the any one of the cells are way out of balance for some reason, these chargers default automatically to a safe charge rate of a half Amp or so. (That's happened a couple of times)

As for the Cellpro chargers balancing during the charge cycle, it's easy to prove. Take a look:

Cellpro Battery Cycling
http://www.wattflyer.com/forums/showthread.php?t=70621
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Old 01-02-2016, 08:35 PM
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I had a Zippy 4s 5000 mah pack delivered with one cell at 3.0v. I went through the warranty rigamarole with Hobby King and they sent me a new one based on submitted photographs. Being the cheap bastard that I am, I set the bad one on the Cellpro PL and just let it roll. It beeped a little then went into ______ mode. It did bring the cell back up but IIRC took about 8 hours at a very conservative charge rate.
Pack performs same as the others in that lot. I do have a note on it however. Nothing wrong with writing on your stuff.
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Old 01-09-2016, 04:32 PM
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Originally Posted by JetPlaneFlyer View Post
Regarding storage and discharge.

As Nigel says, 'discharge' fully discharges the battery all the way down to it's lowest safe voltage, typically around 3.5V per cell. You would normally only use that option if you wanted to discharge the battery prior to disposal.

'Storage' takes the battery to optimal storage voltage, usually in the 3.8-3.85V per cell range. It will either charge or discharge the battery to that voltage depending on if it's starting voltage on connection is lower or higher. Most chargers dont by default balance in storage mode. There isn't really much point because the battery will get balanced on the next charge cycle.
Some chargers do have the option in the setup to balance in storage mode but in my experience by default they dont balance.
Balance in storage mode is basically not required because the charger will be bringing each cell to storage level. In effect by default effectively balancing.

If you use the MyRCMart 3in1 ... this does same ... it brings each cell to the set voltage ... effectively creating a balanced pack.



Nigel
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Old 01-09-2016, 06:23 PM
  #22  
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FWIW Lithium batteries do not drift much contrary to what charge manufactures might tell you. Once Balanced properly at the Top or Bottom, lithium batteries do not become unbalanced anytime soon.

IN EV's with a BMS, especially those that monitor each cell voltage/temp and have Shunt Balance Boards do become unbalanced very quickly because those parasitic loads on each cell that dray power unevenly from each cell. That does not happen with your LiPo battery.

All the cells are in series, and each cell has the exact same amount of current while being charged or discharged if the Balanced Plug is not used and connected. My Golf Cart uses a 32S 80 AH. I Bottom Balance the pack initially to eliminate over discharge. I only charge to 90% to double battery cycle life. Most DIY EV folks use Bottom Balance. I find I only need to balance about every 6 months of so. But even the guys who do Top Balance do not balance very often. They turn down the voltage to limit charge to 90% SOC for the same reason Bottom Balance folks do to extend cycle life.

Point here is if you Balance with every charge will take longer because almost all LiPo or any lithium battery uses a Shunt method and to do that the Shunts operate at very low currents that get activated at the end of the charge.

If your Charger has a Fast Charge Function should not require the Balance Plug to be used. They work in the CC mode only and switch off when the total cell voltage reaches 4.2 vpc and terminates the charge. If you use 1C rate that should get you roughly to 90% SOC. By doing just that will double your cycle life. Going to 100% each time is killing your batteries.
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Old 01-09-2016, 06:35 PM
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Originally Posted by dereckbc View Post
...If your Charger has a Fast Charge Function should not require the Balance Plug to be used….
Fast charging is fine if your packs are balanced but if you do it without the balance lead attached you lose the chargers protections for any individual cell going over voltage. This is a dangerous practice and is the primary reason for many of the LiPo fires in the early days. Do this and you are back in the days before balance chargers were invented. It is really bad advice and can lead to fires. Always connect the balance lead no matter what charge mode you choose. Why would you spend money on a smart safe charger and then not use its safety features?
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Old 01-09-2016, 07:04 PM
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Actually the rate that LiPo go out of balance is related to how high your current demand is.

No 2 cells have exactly the same internal resistance. the higher the current the more that will act to unbalance the pack.

When we were using 8C and 12C packs and pushing them close to C rating we were driving the packs noticeably out of balance in just a couple of charge cycles.

With high C rating packs the now extremely small differences in internal resistance between cells and operating at an average of less then 1/4 max rated current is not driving them out of balance as rapidly.

Its still a good idea to balance on a regular basis if not every charge.
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Old 01-09-2016, 08:41 PM
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kyleservicetech
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Originally Posted by Turner View Post
Always connect the balance lead no matter what charge mode you choose. Why would you spend money on a smart safe charger and then not use its safety features?
Exactly! LiPo fires may not happen often during non-balancing charging, but if and when a LiPo battery does ignite, you'd better have it in a very safe location, outside of your home. Even if the fire is contained with a LiPo bag, there is still the considerable amount of smoke to deal with.

FYI, my Cellpro PL8's do balance the cells when in the storage mode program.
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