Bulk charging A123 LifePo4 and Konion Li-Ion packs

[jerrysimon]

Bulk charging DIY A123 LiFePO4 and Konion Li-Ion packs

NOTE this post covers DIY battery packs not commercial ready built batteries where you should use the recommended charger ONLY

As you know I have been building A123 packs using nominal 3.3V (3.6V max), 2.3Ah capacity cells for a while. I usually make these into 6s1p packs and then series them together to make a small 12s1p pack for my small flat 5.25 mile commute trip, then charging again at work.

I also now have some Li-Ion Konion cells with a nominal 3.7V (4.2V max), 1.5Ah capacity. These I have been building into 5s2p packs again then serializing them together for a 10s2p pack giving a slightly higher 3Ah pack. I also have a 10s4p pack as well.

The reason I split the pack is because I have no BMS and for easy occasional balancing use a cheap RC balance charger for the 5s and 6s split packs.

My experience with no BMS is these cells remain in balance quite well balancing the A123s after maybe every 3 months of daily use. The Konions have not gone out of balance since I built and started using them almost 6 months ago. Both these cell types are also highly stable and safe even if they get damaged.

Anyway for bulk charging (i.e. when the packs are connected together in their 10s and 12s configs) I use cheap 36V plastic block chargers.

The problem I have had was that the Li-Ion need 42V (10 * 4.2V) chargers and the A123 43.2V (12*3.6V) chargers. This means two different chargers. Also for some reason I have always used the lead acid 41/44v floating/equal point chargers for the A123 which is what was recommended when these first came out. Although this should take the A123 cells to 3.6V each in practice they often end up slightly out of balance because of it. Once used for a short bit the cells tend to come down quickly to around 3.4V and are balanced.

Anyway after reading this thread on endless-phere

Endless-sphere.com • View topic - A123 capacity vs charge voltage (and other effects)

I have tried using the Li-Ion charger on my A123 cells and carefully monitoring the current as it dropped during charging until the green light lit and it seems to actually charge them better i.e. they better balanced after charging albeit only to 3.4V/cells. According to the thread linked above you only lose about 50-60mAh and I confirmed this during my test charge.

I guess the other way round i.e. using the A123 charger to charge the Li-Ion packs would have resulted in excessive charge/cell and thus failure of cells.

This now has the advantage that I can use one type of charger for both pack types

Just thought I would post this for those of you that use the A123, 12s packs. It seems to me "so far" that for these A123, 12s packs its worth bulk charging them with a Li-Ion charger.

Jerry

 

[Joneser]

Hi Jerry

Could you please give me some guidance on charging the A123's?

I have the Turnigy charger balancer - am I right in thinking that this charges and balances at the same time but will only do 1 x 6 pack at a time via the white multi connector things?

And that your 'cheap' charger does both packs at the same time via the Deans connector?

My Forzatec Lifepo4 5Ah battery and charger has arrived and I'm hoping the charger will also be ok for the A123's. I have added Deans connectors to the Forzatec battery and charger.

Do I connect it like this?



What is that 3 pin charger mains connector? Can I just switch it for a standard kettle cable?

Hope you / Dave can help!

Thanks
Joneser

 

[Deleted member 4366]

Whatever you do, make sure that you disconnect the two packs out of series before charging with the lipo charger. I don't know exactly which lipo charger you've got, but for most of them they have both power and balance leads that need to be connected.They charge through the power leads and valance through the balance connector. You should read the instructions because it's important that you set the right type of cells, the charge voltage and current. You can charge both packs at the same time if you take them out of series and use a balance board to charge them in parallel.

It looks like that photo shows correct connection. Make sure that the cells are balanced before charging like that. You can use a voltmeter on the multi-pin connector to check the cell voltages. I can't help on that three-pin plug. I've not seem it before. check that the charger's for 230v and not 120v. It might have a switch.

 

[Joneser]

Whatever you do, make sure that you disconnect the two packs out of series before charging with the lipo charger. I don't know exactly which lipo charger you've got, but for most of them they have both power and balance leads that need to be connected.They charge through the power leads and valance through the balance connector. You should read the instructions because it's important that you set the right type of cells, the charge voltage and current. You can charge both packs at the same time if you take them out of series and use a balance board to charge them in parallel.

It looks like that photo shows correct connection. Make sure that the cells are balanced before charging like that. You can use a voltmeter on the multi-pin connector to check the cell voltages. I can't help on that three-pin plug. I've not seem it before. check that the charger's for 230v and not 120v. It might have a switch.

Thanks Dave

Just to remind you that the Forzatec charger came with the Forzatec Lifepo4 battery which has its own PCM (is this the same as BMS?). The charger however is labelled as Li-ion hence I thought the relevance to Jerry's post.

The charger has a switch - 220 or 110 Volts.
The charger output is stated as 43.8VDC, 3Amps.
The power lead 3 pin plug states AW105, 10A, 250V

What do you think?

Many thanks
Joneser

 

[jerrysimon]

Dave's post is very relevant.

On my Li-Ion chargers I lowered the voltage from 43.8V to 41.0V (I could open them up and adjust a voltage pot) which equated to just over 3.4V/cell. This is perfect for my Li-Ion Konion also without a BMS as their 10s (2 * 5s2p packs) works out at 4.1V/cell. I guess I should have mentioned that!

With the A123 cells however the charger kicking out 43.8V would equate to 3.65V/cell for the 12s A123 pack. A123 cells max out at 3.6V so its a little high but would probably work. I lowered it because I find the A123s remain better balanced at full charge if you lower the voltage to 3.4V/cell with very little loss in capacity as per the endless sphere post.

Of course that would probably not be appropriate for your other Forzatec pack which obviously uses the PCM/BMS to set the correct voltage for each cell. Because of that I would be tempted to use a separate cheap bulk charger for the A123 not the Forzatec. You don't want to open it up and start messing about with it!

As Dave says its also important that you balance both the 6s1p A123 packs before you connect them together in series. Also make sure you only use the bulk charger when the two 6s1p packs are reconnected connected back up in their 12s config. Putting 41V or 43.8V through the 20.5/21.6V 6s A123 pack would ruin the cells!

After checking the charger mains voltage is correct, as per Dave's reply, that plug looks like it can easily be changed for a regular UK three pin providing its clear from the wires when you cut it off which are live, neutral and earth. Of course that will give you a second fuse in the plug as well as I think those chargers have a built in removable fuse in the charger shell as well.

Ps I hate trying to explain this in a post. Its much easier/safer to be there in person to show you how

Regards

Jerry

 

[Joneser]

Thanks Jerry, yes I wish you could be here to show me. However, assuming you're not passing through South Norwood anytime soon, could I ask the following to be sure about things:

1) The way I am connecting the 6s1p A123 packs is in series, right? As per photo above? I don't have connectors to connect them in parallel. So I need to buy a cheap bulk charger. I guess I can find the one you have on another post.
2) In the meantime does the Turnigy charge and balance at the same time (or is the charge and balance a separate process)? Can I use this until my bulk charger arrives (does it just take twice as long because of doing 6 at a time)?
3) Jerry I thought you found the A123's lasted a year without balancing, but you then did it every 3 months ish which stretched lifetime considerably - so I don't understand the emphasis in your post above about balancing before connecting in series? Or do you mean its best to balance them for first use?
4) I assume 220V is ok with our UK mains.
Thanks again
Joneser

ps Dave, you mentioned instructions - nothing I have ordered from China has come with instructions so far! In fact both the Forzatec and A123 batteries arrived with Li-ion labelling and warnings. That confused me as I understand Lifepo4 are safer so why would they want to cause alarm and potentially jeopardise postage? Its odd.

 

[Joneser]

This charger look ok?
36v Battery Charger for Powabyke Electric Scooter Bike UK STOCK | eBay

 

[Deleted member 4366]

The instructions come with the lipo charger. Most people wouldn't know what to do without them because there's lots of settings.

The 36v charger looks OK, but what's wrong with the one you've already got?. To add to what Jerry said: If you open the case, you'll find a blue block somewhere near a corner with a screw adjuster in the top. You turn the screw to adjust the voltage until it reaches 42v.

PCM I think stands for Printed Circuit Module. There's no way of knowing what it does without examining it. It'll probably controls charging max voltage and discharging minimum voltage, but might not do any bleeding or balancing. some do, some don't.

The Turnigy will balance at the same time as charging as long as you connect the balance leads, otherwise it'll bulk charge.

You need to balance your cells before bulk-charging in case they're out of balance. Say half were at 3.0v and others at 3.4v. By the time the whole pack is 42v, half would end up at least .2v over-charged, but in practice they rise rapidly when full, so probably would go as high as 5v before the overall 42v was reached. You can check them before balancing. They might already be balanced, but if they're not, you have to do it.

I told you that your connections are right for bulk charging. With some lipo chargers, you get a small balance board with multiple connectors, so you can do two or more packs at the same time. As I said, one day you will forget to break your series connection, so you'll see a connector vapourise.

 

[jerrysimon]

You could use that linked charger (I have been using those for 3+ years) but I suspect it has a equal /floating charging voltage of 44.5V/41.5V which I find overcharged the A123s slightly at full charge and they get out of balance.

Yes I did use and abuse the cells for the first year (after balancing them at the beginning which is very important as Dave states) but I lost two cells. Balancing every 3-6 months will extend the life plus of course not running them flat every ride.

As Dave states I guess you could open up the alloy cased charger and turn the voltage down a touch which would then serve as a charger for both packs, assuming the lower voltage will work with the Forzatec batteries internal circuit.

Regards

Jerry

 

[Joneser]

Right, Woohoo! I have a working Q75 electric bike - just did a few circles in the garden.

I haven't sorted the charging / balancing business yet though.

I have connected the 6S A123's to the Turnigy and the screen shows
Life Balance 3.4A 19.8V(6S)

I expected it to do something when I connected the battery but nothing happened.
Is it balancing or have I missed something?
How long does it take?

Thanks in advance
Joneser

 

[jerrysimon]

Usually on mine you hold down the start button it then checks the cell count and once ok asks to continue and then you push start again and it starts to balance.

Once started then pressing one of the other status button alternates the screen to see individual cell voltages as it balances and current being applied. This can take as long at 2 hours depending on the existing battery charged state/capacity.

Jerry

 

[Joneser]

You could use that linked charger (I have been using those for 3+ years) but I suspect it has a equal /floating charging voltage of 44.5V/41.5V which I find overcharged the A123s slightly at full charge and they get out of balance.

Regards

Jerry

Thanks Jerry
The charger has arrived and I have checked it with my multi meter and it shows 41.3 to 41.5 Volts. I'm not sure what equal / floating means. Does my reading confirm what you suspected? I assume this is ok to use as long as I balance them every now and again (please see my balance query request too! sorry just noticed you have already responded thanks!)
Many thanks
Joneser

 

[Joneser]

Usually on mine you hold down the start button it then checks the cell count and once ok asks to continue and then you push start again and it starts to balance.

Once started then pressing one of the other status button alternates the screen to see individual cell voltages as it balances and current being applied. This can take as long at 2 hours depending on the existing battery charged state/capacity.

Jerry

Oh ****. It comes up with a CONNECTION BREAK message. Have tried both 6S packs - same message. Connection appears sound.
Am I supposed to have the battery power cable connected at the same time?

UPDATE - I have connected the power leads and it now seems to be working. Don't seem to be able to find individual cell voltages though. It shows 2.5A and a voltage reading slowly going up, now at 20.87.
Joneser

 

[Deleted member 4366]

Yes, it charges through the power cables.

You should read the instructions. There's lots of settings and adjustments. You have to get it right.

 

[Joneser]

OK so in order to balance it has to charge so both need to be connected.
The Turnigy did not come with any instructions so I'm trying to find stuff out on the internet.
Maybe I should not even be trying this. Its not ideal so I appreciate your help.

So the Turnigy is now showing 0.5A and 21.42V so I guess its drawing less current as the pack reaches balance / full charge.

 

[averhamdave]

Press the + button whilst its charging and it will change to a screen showing you individual cell voltages. Press it again to return to the screen you are looking at. Good budget charger the Turnigy Accucell

 

[jerrysimon]

Yep both balance lead and main charge lead need to be connected.

The bulk charger voltage of 41.3/41.5 is fine. It won't take the cells up to 3.6V max i.e. 43.2V and full 2.3Ah capacity but will be close around 2.2Ah and on the plus side the cells will remain better balanced for longer (providing you don't run it flat every ride) and survive more life cycles.

As stated its worth still checking the cells every few months to check cell voltages are consistent and then using the balance charger on each 6s pack if necessary.

I use one of these for quickly checking cell voltage via the balance plug.

Cell-Log 8M Cell Voltage Monitor 2-8S Lipo ( UK Warehouse)

There are alternatives which are cheaper but I like these.

These 2.3Ah packs provide a very economic battery providing your regular ride distance is short or flat enough not to drain it down to less than around 0.5Ah. Having said that as stated I abused it for over a year before I lost a couple of cells.


Regards

Jerry

 

[Joneser]

Thanks for the tip Jerry

I am so pleased at the moment as I've been chipping away at this project which has been difficult because of no prior experience or expertise (and full time job + 2 young kids) and here is a milestone:

I don't know if I could have done it without Jerry and Dave's advice and willingness to share their work and knowledge. Thank you!

A summary of what this is:

Q75 front hub motor with 12S A123 batteries and KU63 controller stored in the waterproof Topek saddlebag.

(I am not using the S06P controller yet as it did not work, presumably because I have not fitted the PAS yet.)

I have not fitted the brake sensors yet but I am tempted not to bother as the motor is small and I can't think the risk is of any significance.

I have taken the bike for a short run up a local incredibly steep hill and it does the job. I think the motor is quite slow (fine for steep hills) so no benefit for travelling at speed. The free wheel is fine and the bike without power feels just as it did before the conversion. It is now 16Kg. My commute is just over 10 miles and I only intend to use the motor for the very hilly bits which are about 2.5 miles.

I am really looking forward to trying this out on the full commute tomorrow.

ps its a shame its a little noisy. I'd like to try a Tongxin to compare qualities

 

[jerrysimon]

Glad you are pleased with the conversion. For me this forum has always been about sharing and when I joined it four years ago like you I was on a steep learning curve. Many on here are simply returning the help they received when first starting out.

Re cutouts I only use cutout brakes because I have cruise control i.e. hold the throttle for more than 20s or so and it remains on. The brake cutout then kills the cruise control though you can also blip the throttle to kill cruise control. Its not ideal but I like this function.

For lower powered motors you can pretty much stop the motor with brakes even if it did not switch off. I would probably always have a kill switch within reach though which on my Brompton is attached to the front bag and kills all power. I also like it as I use it before I plug the battery into the controller and I don't then get a spark, switching on after I have done that.

The Tongxins are pretty much silent which I always liked though once you ride your ebike for a while quite frankly you won't care if people hear the motor or not!

If you plug in a watt meter you can test your commute to see how much capacity you use on your commute and if necessary, like I do keep a charger at work to charge before the trip home to ensure you don't exhaust the battery.

Regards

Jerry

 

[Joneser]

Jerry
Yes I am going to add a switch. I already have the watt meter but couldn't quite squeeze it into the saddle bag. Some details still to work out!
Will let you know how I get on tomorrow.
Joneser