Problems with Turnigy Accucell 8150 - goes over voltage

[Peter Sternersson]

Hi!
Long time reader, first time writer (from Sweden so please be easy on my spelling and language ).

For a long story short, read the last bold lines that sums it up pretty well.

Some time ago I started two electric bicycle builds for me and my girlfriend. I finally got the last parts of the puzzle yesterday, the chargers from Hobbyking, Turnigy Accucell 8150.

My battery packs consists of 16 pcs of LiFe-cells from http://www.ev-power.eu/ 15Ah each, connected in series for 48V and 15Ah.

I couldn´t find a 16S charger, and didn´t know you could paralell charge the cells, so I built my pack as 2 8S that I can connect together to 16S when I ride, and break down to 8S for charging.

So yesterday I got my 2 chargers from Hobbyking and connected them up to the battery (batteries).
The first mistake I did was to choose "LiFe charging", so 4 cells went waaaaay high in voltage, probably frying them (no problem as I ordered extra cells so I can replace).
Stupid me thought that with the balance leads connected, the charger/BALANCER whould measure the individual cells, not allowing them to go over 3,6V.
This of course was not the case when putting the charger in "Charge" mode.

Lesson learned, so I hooked up my other battery pack (for my girlfriends bike) and set the charger in "LiFe Balance", and closely monitored the cell voltages that you can cycle through on the chargers display. One cell per charger charged a little faster than the others, and I was excited to see what was going to happen when it reached 3,6V.

And the answear was, nothing, it just kept on going, it peaked out at 3,75V before I turned it off. Same thing for both the chargers, just kept on going.

I am sure that the charger is set correctly, LiFe charge, 8S pack, 28,8V in total, and the manual says that LiFe will only charge to max 3,6V.

To sum thing up into one sentence, my new Turnigy Accucell charger does not stop at 3,6V when put in "LiFe balance", but keeps on going, over charging the cells.
Am I stupid and there is a important part I´m missing, or are the chargers both broken?

 

[amigafan2003]

lifepo4 cells can be charged up to 4.1v then they lose the surface charge and settle back down to 3.6/3.7v per cell - much like a 12v lead acid battery is charged @ 14.4v but settles down to 12.7v when fully chraged and off the charger..

3.75v peak is nothing when charging lifepo4 cells - be brave and let the charger finish charging and come back and tell us what the peak voltage is and what voltage the cells come to rest at when off the charger.

 

[dogman dan]

3.75 is what my pingbattery lifepo4 charges to. 3.65 is enough though. I've not had problems with the same charger myself, but I've never tried the lifepo4 setting. Sounds like an experiment is in order, to see where mine stop if I put lipo on there, and select lifepo4 charge.

But it does sound like your chargers take your lifepo4 higher than you'd expect them to. They should not be taking them to 4 v at all. It won't help with the balancing, but maybe you could try non balancing charge, but set the charger for 7s. If it's charging to 4v, 7s would charge 8 cells to 3.5v. But no balancing, so balancing will still be a pain, charging each cell one by one and watching it for an overcharge.

How high did the "ruined" cells get? 4v is bad, but they should still be usable. I wonder if you life setting is not programmed for lilo instead. Lilo would charge to 4.1v.

Tomorrow, I'll have a report for you on what my identical chargers do when set to lifepo4.

 

[itchynackers]

I have 2 of these chargers and they have never caused a single problem for me. But, I don't use LiFe.

 

[Peter Sternersson]

Thanks for all the replys guys!

Today I turned in my chargers and battery pack to a local RC-shop that whould charge with another 8S charger and see what happened. I am going back tomorrow to see the results.
I also got a reply from Hobbyking where they asked me if I set the peak cut off voltage to 3,6V?
I was under the impression that the top voltage was set to 3,6V when I choose the LiFe.

I have read the manual over and over again, but I cant find anywhere about a peak cut of voltage setting...?

It says on the battery specs that voltage over 3,65V will harm the battery.
Dogmans suggestion with 7S non balance charge might work, but it seems that some cells take charge much much easier than the others, so those cells will probably end up far over 3,6V while the others ends up low.

I will report tomorrow what the RC-store have to say...

 

[dogman dan]

I forgot to check out my chargers on tuesday afternoon. I'm having a bad week with my illness.

I never found any way to reprogram my lipo settings either, when I wanted to set them to slightly undercharge on the lipo charge setting.

 

[Peter Sternersson]

The RC store hadn´t had time to connect up my batteri and test it with their own chargers. Apperently my balance cables was a bit biggger than what they had so it didn´t fit without modification which they hadn´t had time to do.

So I took my chargers home with me to tinker with. I have two battery packs so I left one with the RC shop that they will test tomorrow and see if it works at all...

I have made a little video showing what happens when I try to charge, this I will send to Hobbyking, but I will post it here as well so you guys can see if I´m doing something wrong or what...

http://www.youtube.com/watch?v=YSmAsQaUGZQ

A funny thing is that on Hobbykings homepage it says that copies of the Turnigy charger has begun to show up, and that they are made of poor components and often overcharge and doesn´t balance correctly... I got my chargers in a brown, cheap cardboard box... Not the black nice box that Hobbyking show in their youtube video of the chargers...

 

[dnmun]

i just posted a lifepo4 cell to 4.6, it is holding at 3.45 right now, wanna see if it has any life left, but 4.1 is not deadly imo. bad, not deadly, but i am not an expert.

 

[Peter Sternersson]

Of course the voltage drops when you take them of the charger, but is the voltage suppose to go waaaay over what the manufacturer rates as safe? To then drop down to the nominal level?

I have never worked with batteries in this manor before so I honostly don´t know...

 

[dogman dan]

I've got some lipo charging right now using the life setting. If it stops at 3.65v, my lipo won't overcharge,

If it wants to go higher, I'll stop it at 3.68 x 7s. That would be charging my 6s lipo to just under 4.3v

Took my awhile to figure out how to get the charger to set for life. Sure you don't have it set on lilo or lipo? That would really overcharge life.

Thanks for the shove, bro, now I finally learned to set my chargers for lilo, which is supposed to make em last longer by slightly undercharging lipo.

Find user set program, press enter to get in. then get the voltage number to flash by pressing enter again. then use the middle up down buttons to get it to show lifepo4, 3.3v. It will offer lipo 3.7v , lilo 3.6v, and life 3.3v.

 

[dogman dan]

Well, my Accucell 8150 charges to 3.6v when it's set to life. But when you select life on the menu, it uses the nominal voltage of 3.3v per cell.

When you select life on your charger, does it say 3.3v?

Did you set it to 8s life? Once you choose life balance or life charge, you have a chance then to adjust the cell number. It might be default set to a higher number than 8, when set to charge with no balancing.

 

[Peter Sternersson]

Hi!

First of all I´m so happy for all your help guys, on many other forums, none mention, none forgotten, I still whouldn´t have any answears...

When I go in to "User Program" and toggle between the different lithiumoptions and choose "LiFe", it says 3,3V. All good.

It is also set to 8S when I go to charge/balance, so no fault there.
I have also calibrated the charger by holding down the "Start" and the "Dec" buttons upon power up. It was only off by 0.02V so no worries there.

I will try to get my hands on a LiPo battery and charge it as a "LiFe" and "LiPo" and see where it actualy stops.
I have a suspicion that no matter that battery type I select, it goes by the "LiPo" setting when balancing or something, maybe som copy/paste in the chip programming that gone wrong...

Also, as I mentioned before, in HKs video on the charger it comes in a fancy shiny black box with logotypes and everything, while I got mine in a cheap brown cardboard box with not a single letter on. And HK warns on their page that cheap copies of Turnigy chargers has begun to pop up, chargers that over charge and doesn´t balance correctly according to them.
Is it perhaps one of these chargers I have gotten???


Anyhow, I got pissed of yesterday evening so I ordered a large 600W 48V charger from BMSbattery, along with seperate BMS boards that will be mounted on the batteries. It will be a neater solution with a LVC on the batteries as well, something that I think my girlfriend will like, not having to check the Wattmeter all the time to see if the batteries are getting fried...

I only wish Hobbyking whould put some effort in to this, I have written to them three times describing how everything is hooked up and even posted them a video, but all I have gotten in return is "Have you set the right voltage, Sir?"

 

[amigafan2003]

http://turnigy.co.uk/downloads/accucell-8_manual.pdf

 

[Lebowski]

Anyhow, I got pissed of yesterday evening so I ordered a large 600W 48V charger from BMSbattery, along with seperate BMS boards that will be mounted on the batteries.

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=42777

 

[Peter Sternersson]

Anyhow, I got pissed of yesterday evening so I ordered a large 600W 48V charger from BMSbattery, along with seperate BMS boards that will be mounted on the batteries.

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=42777

Yeaaaahhh, I just realized that BMSbattery and their Alloy shell chargers are far from quality.

Hopefully I get some chargers that actualy work and doesn´t burn my house down at the first charge :?

 

[dogman dan]

So, we assume you bought your turnigy charger someplace else than HK? Bummer. I bet they were factory rejects that HK wouldn't buy.

 

[Peter Sternersson]

So, we assume you bought your turnigy charger someplace else than HK? Bummer. I bet they were factory rejects that HK wouldn't buy.

No no, what gave you that idea? My poor svenglish? (swedish/english) :wink:

I ordered them all directly from Hobbyking, so nothing funny there.

This evening I got hold of a Lipo 3s battery, and seriosly miss balanced it with a resistor. I connected it to the charger and selected Lipo balance at 3s, and IT WORKS LIKE A CHARM!
It holds the high cells at 4,20V ish, and the lower cell slowly climbs up in voltage.
My suspision that the charger is badly programmed seems more and more plausible...
I will test all the chargers and sell them here in Sweden as LIPO chargers for a reasonable price.

I don´t know how much you can calibrate the charger in the calibration meny (but holding down start and incline buttons upon power up), but it might work to fool the charger that its charging a Lipo to 4,2V, when its actually is charging my Life to 3,6V.
Maybe I´ll try that tomorrow, I want to ride my bike already!

 

[whatever]

maybe the 8s cells have very different internal resistances, it might be the turnigy balancing function relies on the cells having internal resistances
within some limits or maybe it uses some average or complex algorithm, do you know the internal resistances of the cells?
If one cell has a very different internal resistance maybe a resistor could be used to change the internal resistance the charger sees for that cell.

 

[DanGT86]

Did you ever get this issue figured out?

I am currently fighting the exact same problem with my accucell 8. For the time being I have used it to charge each cell one at a time and then when they are done I put it in balance mode at under 1 amp and it finishes the balance pretty well. It takes forever to balance in 8 series.

When set in 8s Life mode at high amp rate the high cells go up too quickly. I shut it down after 4v. It wont start balancing until it reaches 28.8v total and then it drops to .5amps and starts balancing. At that point the high ones come down to 3.6 and stay there for hours while the others come up slowly due to the low current. I don't think it looks at the individual cells at all until it hits 28.8v. Seems like the balance mode only works on a close to balanced pack which is pretty useless for a balance charger.

It does not balance them close enough for me to use my bulk 58.4v cut off charger without supervision. That is what I was hoping for.

When I bought it I was under the impression that the user could set the cut off voltage to any number instead of using the pre set voltages for the different chemistries. I am a little disappointed with the accucell.

I am totally new at this so I am glad to have found this thread. I was starting to think this was normal for a charger and that I would need a BMS now.

 

[dnmun]

does the charger have a balance mode charge cycle versus a 'fast' mode cycle?

i bet if you are not using the balance mode it will not cause the cells to balance and will overcharge some of the cells because the balance function is turned off.

4V is not gonna kill the cell like i said before.