Adding LifePo4 to BionX System

Hi Tech heads, I need some informed opinion about the possibility of extending my BionX's systems range with another battery without being extorted into buying one of their over priced batteries - $1300 new, $800 reconditioned (not including postage).

On the V Voltage forum this (see quote below) was proposed as a fairly straight forward solution but there was little follow up. For all I know it ruined the system and the members there haven't been back to report on the foul up.

The BionX battery I have is still very good with plenty of life in it, as far as I can tell. So I don't want to do anything too radical to the existing set up. The following seems fairly elegant, leaving the existing system as is which will serve my purposes most of the time, but will allow me, if it is safe, to extend the range when I have the need via the simple method of plugging the additional battery into the charging slot of the BionX battery.

What do others think. Do you see foresee complications by using the following method:

.... Bought a LiFePo4 36 V 20 amp pack (about $450)which charges to 41-42 volts like the Bionx, and a male XLR plug. Pin 2 is neg., pin 4 positive. Put the supplementary pack on a rear carrier. I Run it with AWG#14 wire, via a spst switch and a 0-10amp ammeter on the aerobars. All features on the console work the same, and the regen motors charge both batteries simultaneously. Of course you've got to use 2 different chargers to charge both packs at the same time with the SPST switch off. This set-up triples the riding range of my Standard 36 volt Bionx battery. It's a lot cheaper than purchasing a new Bionx battery.

http://visforvoltage.org/forum/7804-bionx-battery#comment-45583

Click to expand...

Naturally, I don't want to ruin the system I have, but if others who know about e-systems here, think it is a fairly safe to thing to do, I don't know mind trying it, although I won't be holding anyone responsible but myself should it not work.

PS. I realise ItzElectric have posted a method here via some alterations to the BionX battery case to allow for more batteries. I would be interested in this if my existing BionX battery was dead or close enough dead, but it is still good, and for the most part the system as is serves my purposes without the need for additional battery capacity. For now, I don't want to go down that major change to the system - perhaps later when the BionX battery is no longer practical. This alternative method, quoted above, seems to fit better with an existing system where the battery is still good, as long as it doesn't cause any damage, which is the point of my post, to enquire whether it might.

Any informed opinions would be appreciated, especially from those who are familiar with the wiring set up inside the BionX case. If it helps, I will open up the case and post some pics.

Kalimera Canis Lupus,

I'm thinking of doing a similar thing (but using LiPo on a 250PL). Here's a photo I just took:


The biggest issue, according to Ken at ItsElectric, is the LiFePo4 BMS. When he replaced the battery with a lifepo4, the board burned because the lifepo4 BMS wouldn't accept the regen current. I'm not sure this will be an issue for you, if you already have a battery there that can take the current. In fact, I wonder if your new battery will just be charging the old one... Batteries wired in parallel will constantly be balancing themselves, as far as I understand... So the lifepo4 will come hot off the charger at 40V? Is the Bionx LiMn? The lifepo4 may sag more under load. Not sure...

For me, I can't decide where to wire in the battery. The lipo can handle the regen, and it doesn't have a BMS... And the old battery is okay, but doesn't have quite the range or power we need.

Maybe we should ask Ken where he wired his extra batteries? Straight to the board, or only to the charge port...

Coming out of the battery, there's a yellow wire. I have no idea what that is!

Lonely forum for BionX users tho!

Yasu GCinDC,

Yes, BionX's battery is Lith Mag. I was thinking of buying an additional Lith Mag to match as the extra battery instead of LifePO4. Maybe I could use BionX's charger for that battery.

I did wonder whether the second battery would act to recharge the BionX battery. If so, that would present an inefficiency in the usage of the second battery.

Yep, it's a bit lonely for BionX users, although there are few to help. Can't say I blame them as a whole. BionX generally is for the technically challenged who don't want to tinker too much - like me. I'm feeling more adventurous than I was some time ago, and if I was buying now, I would go for a different system which puts a few more demands on my technical abilities but gives greater flexibility and performance in return, as well as saving some money.

I inquired to BMZ about an LiMn battery to match my existing but was told they don't deal in small quantities. That said, I really don't see a reason why the same pack couldn't be built custom.

Does your charger say 42V max? If so, it's gotta be 10s.

My charger does 29.4V max/7 cells = 4.2V/cell. The quantity of the cells would then determine the Ah.

I don't know much more about LiMn, the charge discharge range.

I decided to use lipo because it's relatively cheap, but I'm not going to charge each cell to 4.2V!

I don't think LiFePo4 can be charged at a high C rate (regen), and they typically have the BMS...

So anyway, for you, I'd guess the most important thing is to identify the circuit diagram - to protect the batteries and ensure efficiency, and then the voltage/charging solution.

I don't necessarily see why charging the LiMn battery would be inefficient, if it was 'hooked up' to the lifepo4 halfway through a ride. But I don't have a clue about that.

Actually, as long you as you have the LiMn in place to receive regen current, the lifepo4 could be isolated (not connected to the LiMn) to provide power only. Regen would just recharge the LiMn. Discharge only provided by lifepo4. Make sense?

figure out what burns on the lifepo4 BMS. if it is the charge FET overheating or overvolting on the bemf then maybe upgrade to irfb4110.

maybe figure out some way to turn off regen if the BMS shuts down the charging FET, by monitoring the signal to the gate drive maybe.

dnmun said:

figure out what burns on the lifepo4 BMS. if it is the charge FET overheating or overvolting on the bemf then maybe upgrade to irfb4110.

maybe figure out some way to turn off regen if the BMS shuts down the charging FET, by monitoring the signal to the gate drive maybe.

Click to expand...

Hey Dennis! Thanks for replying! What have YOU been up to?

Ken said that the BionX board blew when used with lifepo4 (& bms), NOT the bms... He said that the lifepo4 bms prevented? the regen charge and the charge had nowhere else to go so it overloaded the bionx board. (that said, does the board in my picture above look familiar? I'd thought the bionX CONTROLLER is in the wheel itself, which makes me wonder what the one inside the battery case is. maybe it's a separate board for certain functions? or does it look like a full fledged controller?

Ken DID mention turning off regen either by the console or by attaching a magnet to ebrake line... But regen is so integral to the system, it seems like it would be such a shame...

Canis Lupus said:

Hi Tech heads, I need some informed opinion about the possibility of extending my BionX's systems range with another battery without being extorted into buying one of their over priced batteries - $1300 new, $800 reconditioned (not including postage).

On the V Voltage forum this (see quote below) was proposed as a fairly straight forward solution but there was little follow up. For all I know it ruined the system and the members there haven't been back to report on the foul up.

The BionX battery I have is still very good with plenty of life in it, as far as I can tell. So I don't want to do anything too radical to the existing set up. The following seems fairly elegant, leaving the existing system as is which will serve my purposes most of the time, but will allow me, if it is safe, to extend the range when I have the need via the simple method of plugging the additional battery into the charging slot of the BionX battery.

What do others think. Do you see foresee complications by using the following method:

.... Bought a LiFePo4 36 V 20 amp pack (about $450)which charges to 41-42 volts like the Bionx, and a male XLR plug. Pin 2 is neg., pin 4 positive. Put the supplementary pack on a rear carrier. I Run it with AWG#14 wire, via a spst switch and a 0-10amp ammeter on the aerobars. All features on the console work the same, and the regen motors charge both batteries simultaneously. Of course you've got to use 2 different chargers to charge both packs at the same time with the SPST switch off. This set-up triples the riding range of my Standard 36 volt Bionx battery. It's a lot cheaper than purchasing a new Bionx battery.

http://visforvoltage.org/forum/7804-bionx-battery#comment-45583

Click to expand...

Naturally, I don't want to ruin the system I have, but if others who know about e-systems here, think it is a fairly safe to thing to do, I don't know mind trying it, although I won't be holding anyone responsible but myself should it not work.

PS. I realise ItzElectric have posted a method here via some alterations to the BionX battery case to allow for more batteries. I would be interested in this if my existing BionX battery was dead or close enough dead, but it is still good, and for the most part the system as is serves my purposes without the need for additional battery capacity. For now, I don't want to go down that major change to the system - perhaps later when the BionX battery is no longer practical. This alternative method, quoted above, seems to fit better with an existing system where the battery is still good, as long as it doesn't cause any damage, which is the point of my post, to enquire whether it might.

Any informed opinions would be appreciated, especially from those who are familiar with the wiring set up inside the BionX case. If it helps, I will open up the case and post some pics.

Click to expand...

I should have completed the posting on the bionx battery hack topic.
You can replace any battery that you like (within 36 – 38v). It will work; we ever replace it with SLA battery for testing purpose.

We later discovered that the Binox will allow unlimited regen. I mean completely open. If you are go down a long steep hill, the amount of current could be as high as 60amp coming back from the motor. Most of the lithium battery that had BMS or PCM will reject and trip the overcharge condition and shut down the battery. When this happen, you still have current come back from motor that had no place to go, except blow up the circuit board.

We tried to use voltage clamp to clamp down the voltage around 42.5v and turn it into heat. After we review the setup and understanding the unlimited re-gen, we will end up with a giant heatshink.

The battery was used in Bionx system are sony konion US18650V lithium manganese cell. Bionx had figure this cell will be able take high current for re-charge (just like A123), they have designed the battery without BMS or re-gen limit. DoctorBass will be able explain better then I can. But the sony lithium manganese had a special property, that doesn’t require balancing and can be overcharge.

So we started more research found another manufacturer bike that use bionx system was having the same problem. We worked with them for awhile, they manage to fix this problem with bionx’s help. If you look at version of a bionx console. The latest production version is 2.7 for I2C. However, if you have a console version 2.9, this special console that was re-programmed by Bionx. It will stop re-gen after 42volt. The special console cannot be obtained through normal channel. Now does anyone know how to clone and re-flash a regular console onto version 2.9. This re-gen problem will goes aways.
So, you have a few options to replacement battery

- Pack a battery using same cell as bionx (u can’t get the cell through normal channel)
- Use one of the lifepo4 battery but disable your regen function
- Or use one battery to charge your old dead bionx battery, so when it regen, the regen current goes to old battery. This can be done through the bionx charge port. But you are carry double weight.
- If you have backdoor bionx connection, obain I2C console version 2.9, or clone the console if you able to get one of v2.9 console.

Ken

I have the PL36 version but I don't know the firmware version. In my riding areas, there are not many hills around. Therefore, I just tap the + and - out of the PCB and parallel to a 10S 10Ah Lipo from Batteryspace. At home, I charge the Lipo with a generic charger. At work, I charge the Bionx with the Bionx charger. Since they are paralleled, both packs will get full charge. Warning: this solution is not for everyone. Your situation will be different.

ericslai said:

I have the PL36 version but I don't know the firmware version. In my riding areas, there are not many hills around. Therefore, I just tap the + and - out of the PCB and parallel to a 10S 10Ah Lipo from Batteryspace. At home, I charge the Lipo with a generic charger. At work, I charge the Bionx with the Bionx charger. Since they are paralleled, both packs will get full charge. Warning: this solution is not for everyone. Your situation will be different.

Click to expand...

Awesome. Thanks for sharing! Couple of questions:

So did you drill a hole in the case and solder the lipo leads to the board? where the bionx battery is soldered to? Or did you splice them and run taps out for a lipo that you can then disconnect?

Any way of monitoring the voltage on the lipos? Or balancing the lipos?

Does the lipo add noticeably more power, or just more range?

Hi Ken, Thanks for the response!

- Pack a battery using same cell as bionx (u can’t get the cell through normal channel)

Click to expand...

Do you sell LiMn packs in the bionx config? Could you do 7s ?

- Or use one battery to charge your old dead bionx battery, so when it regen, the regen current goes to old battery. This can be done through the bionx charge port. But you are carry double weight.

Click to expand...

You use the charge port because it's isolated from the regen current? If the additional battery were connected to the PCB + & -, it would be subjected to full regen current, is that right?

ericslai, i've been thinking about using 8s lipo w/ the 7s limn bionx, just because i've been afraid of overcharging the lipos. it sounds like you don't use regen much, or not high current from steep hills. have you ever seen the cells go out of balance? how long have you had the setup.

sorry for the million questions!

ericslai said:

I have the PL36 version but I don't know the firmware version. In my riding areas, there are not many hills around. Therefore, I just tap the + and - out of the PCB and parallel to a 10S 10Ah Lipo from Batteryspace. At home, I charge the Lipo with a generic charger. At work, I charge the Bionx with the Bionx charger. Since they are paralleled, both packs will get full charge. Warning: this solution is not for everyone. Your situation will be different.

Click to expand...

I'd be interested to read your method of running them in parrallel, whether you have altered the wiring in the case or doing it via the charging plug.

Judging from Ken's post, it seems there is no complications with BionX's regeneration feature using the charging port to plug in an extra battery. Using this method of adding the additional battery, it also seems to have the effect of charging the BionX battery rather than supplying current directly to the motor from the second battery. My understanding of charging a battery from a battery is that there is an energy loss in that process.

I also wonder, if that is the extent of the second battery's role whether, under circumstances of high power drain of the BionX battery, the recharging by the second battery would keep up with the draining of the BionX battery. If there is no direct current going to the motor from the second battery, then it would be possible to drain the BionX battery while still having the second battery holding charge, perhaps quite a bit of charge. You'd have to wait a little while for the second battery to recharge the BionX battery before having power available. You would be effectively recharging on the run. Does this sound correct?


I don't know if this helps anyone but here is a link to some Lith Mag packs which are reasonably priced, 36 volt: http://www.batteryspace.com/37V---88.8V-LiMnNi-Battery-Packs.aspx. You will find some 24 volt packs on the same site.

GCinDC said:

Hi Ken, Thanks for the response!

- Pack a battery using same cell as bionx (u can’t get the cell through normal channel)

Click to expand...

Do you sell LiMn packs in the bionx config? Could you do 7s ?
sorry for the million questions!

Click to expand...

Greg:

I am in the process of getting some SONY US18650VT rated 1600mAh cell, which is almost the same as original Bionx cell. I like to experiment how much over charge this cell will takes, and how it possible without the balancing. I am waiting to confirm if the supplier had them in stock. I am plan to get 150 cell, enough for me to make two Bionx replacement batteries, and a few left over that I will try to blow it up.

I am also getting Sanyo high rated cell with 2600mAh. The sony cell will take 60 cell to make a 37v 9.6ah, with this cell I can construct 37v 10.4 with only 40 cell.

yes, I can sell you some cell, but I just waiting for the stock confirmation. On other hand, DoctorBass should have access to a lot of of the same sony cell, he should be able supply you too.

Ken

GCinDC,

So did you drill a hole in the case and solder the lipo leads to the board? where the bionx battery is soldered to? Or did you splice them and run taps out for a lipo that you can then disconnect?

Click to expand...

Yes I soldered to the + and - wires that go from the Bionx battery to the PCB. I had to drill the case to let the parallel wires to come out at the seam. I installed a connector on the parallel wires so I can connect the new Lipo pack easily. The added 10S 37V Lipo has a BMS built-in so I charge it thru the BMS. http://www.batteryspace.com/highpow...7v10ah370wh40adrainrateafireretardantbag.aspx

I have not checked the Lipo's individual voltages yet. When I measure the pack voltages, they were exactly the same because of the parallel wiring. I have used this setup for 2-3 years now.

itselectric said:

I am in the process of getting some SONY US18650VT rated 1600mAh cell, which is almost the same as original Bionx cell.

Click to expand...

That's awesome, Ken. I will be very curious to hear how this goes!

I spent a lot of time online looking for diagrams to show canis lupus (and learn myself) what happens when packs are paralleled. I never found what I was looking for. I thought they try to balance themselves. But I kept reading how one should never parallel batteries with different chemistries. Otherwise they can get into a vicious cycle of charging discharging themselves. Or something like that.

Ken, if I recall, you fried the board when you REPLACED the bionx with a lifepo4 with a bms.

What ericslai has done is very interesting... He's paralleled the bionx with a lipo -- which is high discharge, moderately high charge, i think -- but the lipo has a bms which "Prevents 37V Li-Ion Battery pack from over charge". So most of the regen current can go into the original bionx.

ericslai, you say you've had this for several years??? wow, i thought bms's for lipo were the holy grail... i've seen that site but never noticed all that lipo stuff. even a fuel gauge! that's awesome!

A smart charger (albeit 1.0A) for $27... sheesh!

So Canis Lupus, this has to be a good solution for you! Study about paralleling packs. It would be very bad to parallel SLA & LiMn, but lipo and LiMn seem more similar... I think a key thing to understand is that when the voltages are the same, neither pack will charge the other. As soon as the discharging happens, whichever voltage starts decreasing more will likely pull some current from the higher pack in an attempt to stay in balance. Whether the lower packs acts as a 'load' or current bottleneck I don't know...

But who can argue with a ericslai 2-3 years of use!

ericslai said:

GCinDC,

So did you drill a hole in the case and solder the lipo leads to the board? where the bionx battery is soldered to? Or did you splice them and run taps out for a lipo that you can then disconnect?

Click to expand...

Yes I soldered to the + and - wires that go from the Bionx battery to the PCB. I had to drill the case to let the parallel wires to come out at the seam. I installed a connector on the parallel wires so I can connect the new Lipo pack easily. The added 10S 37V Lipo has a BMS built-in so I charge it thru the BMS. http://www.batteryspace.com/highpow...7v10ah370wh40adrainrateafireretardantbag.aspx

I have not checked the Lipo's individual voltages yet. When I measure the pack voltages, they were exactly the same because of the parallel wiring. I have used this setup for 2-3 years now.

Click to expand...

Ericslai:
Could you or have you plug a CycleAnlasyt in between your lipo battery and the Bionx PCB board. Are you seeing any negative amp coming from the PCB to lipo battery?

You have a high discharge rated battery, that may have avoided the problem. But it also depends how the BMS was programmed in the factor. Weather it will actually takes 40amp charge rate.

There are certain lithium battery/BMS will not accept reverse charge to battery. A good example is PING battery. You cannot regen to recharge the battery through the discharge connection. The could be avoided the problem I was having. I guess I would have put a diode to block the regen going into battery. It will turn into the a lot heat.

There are also another setting with bionx that can low the regen current, i can't remember the exact setting right now. This may also avoided the blow up by over charge.

If you only going a small down hill, it may have been avoided.

In my pass experience and working with a professional electric bike manufacturer who had these problem, they were almost crying. One customer was able to blow up three battery pack circuit board in 2 week time. The same story, fully charge the battery, start the day by go down a steep hill with highest level of regen. They keep replacing the battery pack under warranty. So they gave up using other brand of battery, they are now use only the the Binox battery aka Sony US18650V cell.

Ken

I have a newish PL350 Bionx system, with no battery. I would like to run it on my Ping battery, as a "discharge only" type setup. How can I disable the regen, and where do I connect my "Ping out" leads to? I got the bike for 100 dollars as they were fed up with Bionx and didn't want to buy a new battery (understandable), and I took off the system because it was a nice Devinci Vancouver bike to ride as a normal bike...

they were almost crying. One customer was able to blow up three battery pack circuit board in 2 week time. The same story, fully charge the battery, start the day by go down a steep hill with highest level of regen. They keep replacing the battery pack under warranty.

Click to expand...

Hi Ken, Interesting story. But the battery replaced under warranty was NOT the original bionx battery though, was it? It was probably a lifepo4 with a bms, no? I wonder if the old (even dead) LiMn battery was there, if the board would have blown... It seems to me that if that is kept, it can absorb all the regen charge, esp if it's blocked by a bms.

I've been thinking about using lipo WITHOUT a bms - I use it now actually on my bike (see sig). My max regen current seems to be 8A, but the CA shows peak regen of 18A!

I'm very surprised if you get 60A regen off the bionx!

I wonder if I could test this with a multimeter. I should be able to run wires onto the + and - terminals on the board and ... oh, nevermind, I could just measure voltage, and that'll be the same as the diagnostic console... I was hoping I could switch it to measure amps too, but the multimeter can only measure max 10A, and it would have to be in line w/ circuit, not simply across poles... nevermind!

I have a CA but no idea how I would wire that...

chvidgov.bc.ca said:

I have a newish PL350 Bionx system, with no battery. I would like to run it on my Ping battery, as a "discharge only" type setup. How can I disable the regen, and where do I connect my "Ping out" leads to? I got the bike for 100 dollars as they were fed up with Bionx and didn't want to buy a new battery (understandable), and I took off the system because it was a nice Devinci Vancouver bike to ride as a normal bike...

Click to expand...

No battery or a dead battery?
Battery case w/ board inside?

No battery/no battery case or board from battery case...

chvidgov.bc.ca said:

No battery/no battery case or board from battery case...

Click to expand...

Considering all the electronics inside my battery case pictured above, if you want to ride the bike - as opposed to conducting a science experiment - I'd suggest you get yourself a new battery, controller, and throttle, and just use the wheel like doc. have you seen his post? It'd be a shame to discard the console, but this is uncharted territory! And being a closed system not easy to mod...

GCinDC said:

they were almost crying. One customer was able to blow up three battery pack circuit board in 2 week time. The same story, fully charge the battery, start the day by go down a steep hill with highest level of regen. They keep replacing the battery pack under warranty.

Click to expand...

Hi Ken, Interesting story. But the battery replaced under warranty was NOT the original bionx battery though, was it? It was probably a lifepo4 with a bms, no? I wonder if the old (even dead) LiMn battery was there, if the board would have blown... It seems to me that if that is kept, it can absorb all the regen charge, esp if it's blocked by a bms.

Click to expand...

The story that I have mentioned, was not using Bionx battery, it was lithium magnese cell (yes similar type as Bionx). it has its own BMS. They re-programmed the BMS a few time, still could not manage the re-gen overcharge. Until Bionx step in, they created a new version of I2C console version 2.9 (you can't get this). This new version of console stop the re-gen at certain voltage or amp.

GCinDC said:

I'm very surprised if you get 60A regen off the bionx!

Click to expand...

I could be wrong with the actual number, because I was not the one that witness it, but remember, bionx did not put any limited condition in the re-gen/recharge, the bionx battery will just take whatever current that through at it. To my surprised, these Bionx or Sony cell is an amazing product, that Bionx had figured it out the best way to use them, and for a long time ago. My friend Bob who help me on this project had reverse-engineering the most of circuit board, he kept tell me how good the bionx design was.

GCinDC said:

I have a CA but no idea how I would wire that...

Click to expand...

You need create t-connector or pigtail bewteen the motor trailer wire and to the battery mounting bracket.

Ken

Hi Ken,

Could you or have you plug a CycleAnlasyt in between your lipo battery and the Bionx PCB board. Are you seeing any negative amp coming from the PCB to lipo battery?

You have a high discharge rated battery, that may have avoided the problem. But it also depends how the BMS was programmed in the factor. Weather it will actually takes 40amp charge rate.

There are certain lithium battery/BMS will not accept reverse charge to battery. A good example is PING battery. You cannot regen to recharge the battery through the discharge connection. The could be avoided the problem I was having. I guess I would have put a diode to block the regen going into battery. It will turn into the a lot heat.

There are also another setting with bionx that can low the regen current, i can't remember the exact setting right now. This may also avoided the blow up by over charge.

If you only going a small down hill, it may have been avoided.

Click to expand...

I have not tried to measure the regen current to either pack. It may be a good weekend project.
http://www.batteryspace.com/pcmwith...i-ionbatterypackat40alimitpcm-l10s30-062.aspx

ericslai said:

I have not tried to measure the regen current to either pack. It may be a good weekend project.

Click to expand...

ericslai, I keep thinking about this amazing solution you've come up with. How did you do it? Did you have help? Are you an EE? I searched and searched for BionX modification storys, but yours is one of the few successes I've ever heard of. I think the world would be very curious!

Hi ericslai :
how do you charge both batteries ?
Do you charge them separately with two chargers or both using original Bionx charger thru XLR ?
What is your charging time ?
THX for an answer.

I forgot to test the regen in the last weekend but I will try this week.

ericslai, I keep thinking about this amazing solution you've come up with. How did you do it? Did you have help? Are you an EE? I searched and searched for BionX modification storys, but yours is one of the few successes I've ever heard of. I think the world would be very curious!

Click to expand...

I am an ME but have studied EE and computing, 4 courses of MCSE. A few jobs before the current one, I designed and helped manufacturing rechargeable products such as camcorder and power drill battery packs so I know a few basic principles of rechargeable battery (NiMH and NiCd) pack constructions. Like most Bionx users, I was not happy with the capacity. The fuel gauge is not accurate enough so I opened the plastic case and peeked a bit. There are red and black thick gauge wires that feed to the PCBA. These are the output and input of the battery pack that I tapped to with the Lipo pack. I did the hacking myself.

how do you charge both batteries ?
Do you charge them separately with two chargers or both using original Bionx charger thru XLR ?
What is your charging time ?

Click to expand...

I have to charge the system at work and at home (less than 19 miles each way). So I use the Hi-Power (from Bionx) charger at work. It charges through the XLR charging port of the Bionx pack. Normally it takes 3 hours to finish charging, the charger will shut down.
At home, I charge it with a generic 2A charger but I don't like the full charge voltage which was set too high so I use a timer to shut down the charger. This is always done at home so I set the charging time to be 6 hours. The end voltage is about 41.2-41.5V. I consider that is good enough. The Lipo pack came with a Tamaya type charging connector so I charge the whole system with that.

Since both packs' output + and - are tied together, they are paralleled as one big pack in terms of capacity. The difference is the charge input. Bionx's controller monitors the energy input so the fuel gauge will show full when charging is complete vs the un-monitored Lipo pack. After the system has been fully charged at home with the generic charger, the Bionx fuel gauge will show no juice left! This is not a problem since I know the system's voltage is at 41.2-41.5V by measuring each pack's voltage. I did not get 2 Bionx chargers because of cost.

I tied the two packs at the output side because the LiMn does not need to be balanced at all. Each cell (cell group) is almost identical in terms of charging and discharging characteristics. The Lipo pack has a built-in BMS to monitor charge and discharge. During discharging, the Bionx will treat the whole battery pack as a 20Ah pack. During charging, the whole pack will get a full charge from either charger.

Please DON'T mix NiMH or NiCd this way. These cells need to be monitored with the negative delta V method for safe charging. Their self discharge characteristics will ruin the parallel packs if they were tied together for too long. They can be paralleled for discharge BUT they MUST be charged separately with appropriate chargers and discharged through diodes.