Adding LifePo4 to BionX System

[GCinDC]

Wow, awesome information. I've been studying it for an hour here....

Do you get increased speed and/or torque with the additional pack? Or is it just increased range?

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.

Any idea how it monitors the energy input? The actual Amps/Ah or the voltage?
Also, when you reconnect the lipo pack to the bionx, won't there be current flow between the packs to balance out any difference in voltage?

If the charger limits amps, my plan is hosed -- I've been planning to parallel a 7s 5p (11Ah) lipo pack without a BMS by connecting it to the BionX + & - leads AND charge it ONLY with the BionX charger.

My logic to think I could is:
- Once the packs are paralleled, they'll balance each other
- Since they're paralleled, the voltage will be the same for 'each' pack
- The lipo won't be isolated, so it will accept charge (& regen) current
- The charger will shut off when the pack reaches the voltage, so it'll just take twice as long to charge a pack that's twice as big

Think it will work? Any suggestions?

I'm not crazy about pumping the lipos up to 4.2, even though I will balance them via the balance taps.
I was going to do 8s but thought that'd cause me more problems...
And I was originally going to test a 6.6Ah 8s lipo pack, but decided it'd be better to duplicate capacity as much as possible, so ordered 5 3s 2200mah lipo packs to connect in series with 5 4s 2200mah packs ($175)

Oh yeah, so did you cut the big black & red wires going to the PCBA and splice in a connecting wire to the lipo leads? Or did actually solder the lipo connecting wires to the same spot on the board?
And, on my image on page 1, the yellow charge wire going from board to the pack, does it just go to the - side of the pack, where the black must be soldered?

 

[ericslai]

I just did a simple test to test the regen. Yes, the current flows both directions between the 2 packs. The connection between the Bionx pack and the Lipo pack is not Anderson so I cannot hook up the CA to record the current on the road. I just ran it on a stand (the system is mounted on a recumbent trike).

Do you get increased speed and/or torque with the additional pack? Or is it just increased range?

My goal was range only so I have achieved that. The 36v motor is limited to 25mph max no load (350rpm).

Any idea how it monitors the energy input? The actual Amps/Ah or the voltage?
Also, when you reconnect the lipo pack to the bionx, won't there be current flow between the packs to balance out any difference in voltage?

I don't know how it monitors the energy input. My wild guess is the same as the CA with some software. If the voltages are very close to each other like .2 to .3V, the current will not be too much before the voltages become identical. When I connected the 2 packs together, I made sure that the voltage different was less than .1V.

If the charger limits amps, my plan is hosed -- I've been planning to parallel a 7s 5p (11Ah) lipo pack without a BMS by connecting it to the BionX + & - leads AND charge it ONLY with the BionX charger.

You mean the High Power charger from Bionx? My 36V charger says 2Amp only. My generic charger says 2Amp but in reality, it only consumes ~50W from the mains so it took much longer to charge the whole system. The High Power (Bionx) charger has 3 wires. Sometimes it won't start charging when I just plugged in the XLR charging connector. I had to unplug and plug in again to enable the charger. The yellow wire on the charging port must be looking for either normal temp or just connection to enable the charger.

Your logic makes sense. My 36V charger stops at 41.6V. The charging time did not change from only Bionx pack to parallel pack because my route did not change. The consumption did not change. I seldom run off course and the recumbent trike helps on the aero differences.

Maybe I have missed that. Your is a 24V LiMN or NiMH? Can you verify the cell type and model number that they are actually LiMN? I would not mix different chemistries to be on the safe side.

On the secondary side of the board, the Bionx pack's + and - wires were protruding out long enough. I just soldered a wire harness to them and run the harness out of the plastic case. I had to cut a slot at the seam to let the wires come out. Then I can plug and unplug the two packs easily. The connectors are not Anderson as I said earlier, they are 20Amp Molex free samples.

If you probe (carefully) it, you will find that the yellow is not connected to the negative of the pack I think. It has been a while. It must be connected to a thermistor or something like that. The charger will not be enabled if the yellow wire was not connected to the charger.

 

[Canis Lupus]

Question, touched upon in the previous post by ericslai:

If I have a BionX battery which charges to 41-42 volts and I plug into the BionX's battery charging slot a LifePO4 or Lith Mag battery which charges to 46-47 volts, am I inviting problems?

Looking at Ping's 36 volt batteries, they appear to charge to something around the 46 volt mark.

 

[itselectric]

I made a XLR charge port connector for one of the our Bionx customer. She had a dahon bike. Here are the picture of the XLR charge port connector:

Here is LiFePO4 battery connected to the charge port.

Here is her communication to me:

Hi Ken!

Well, I finally drained my BionX battery after 54 miles of riding on level 1 & 2 at 10 to 15 mph on flat and gentle rolling hills.

No bars are left on the control panel battery indicator. So I get off the bike and hook up the connector to the LiFePO4 battery and turn it on. Then I get on the bike and pedal a bit and on comes the power again. You are a genius!!! It works. And as you can see by the control panel and computer mileage photos 1 & 2, after 17+ miles, the battery indicator shows 4 1/2 bars. Photos 3 & 4 show the hook up to the LiFePO4 battery and I just put it on the bench so you can see, I put it into a pannier which works fine. Then when I took the LIFePO4 battery off and turned on the control panel, it showed that it recharged my original BionX battery to 4 1/2 bars. So you can unhook and ride without LiFePO4 battery and rehook it when you run out again, or just leave it hooked up and keep going.

I will let you know in a week or so what mileage I get from the LiFePO4 battery.

What else is nice about the BionX/LiFePO4 extended battery is that it keeps you at a constant speed when you are going on flat and uphills. Usually your rpm drops when you go uphill or into wind but BionX/LiFePO4 keeps you steady giving you the boost and bionic feel and that's why I like it so much.

So thanks for the connector, you should patent it and make serious $$$$!!!!

So, not only she was able double her range without any modification or opening battery, she was able get better uphill because of double amp. She currently had a PL350 20" and 38.4v 10Ah LiFePO4 battery pack. This is simplest way to get more range and doing it very safety, no modification, no opening the battery, no overcharge regen problem, warranty should be the same. In addition, she also had another eZee kit, she can use the LiFeP04 battery on both system.

Ken

 

[itselectric]

Question, touched upon in the previous post by ericslai:

If I have a BionX battery which charges to 41-42 volts and I plug into the BionX's battery charging slot a LifePO4 or Lith Mag battery which charges to 46-47 volts, am I inviting problems?

Looking at Ping's 36 volt batteries, they appear to charge to something around the 46 volt mark.

Canis:
Do you know how many cell are your ping battery. LiFePO4 cell when it is fully charge, it 3.65v each cell. Normally, a so call 36v (actually it is 38.4v) battery is make up of 12 cell. so 12 x 3.65 = 43.8v, if you have 13cell, then 13 x 3.65 = 47.45v. A fully charged so call 36v battery, should not be higher then 44v, unless it is 13cell, which is very odd. Check you charger, what does it say the output voltage?

Ken

 

[Canis Lupus]

Ken, that's a really elegant add-on pack for the BionX you've made. Well done! That's the type of set-up my OP envisaged, with all the benefits you've stated. I'm really impressed and agree with your client's comments about marketing the setup. I think you will get plenty of demand!!


Please don't let BionX dissuade or pressure you not to offer it more generally.

Question, touched upon in the previous post by ericslai:

If I have a BionX battery which charges to 41-42 volts and I plug into the BionX's battery charging slot a LifePO4 or Lith Mag battery which charges to 46-47 volts, am I inviting problems?

Looking at Ping's 36 volt batteries, they appear to charge to something around the 46 volt mark.

Canis:
Do you know how many cell are your ping battery. LiFePO4 cell when it is fully charge, it 3.65v each cell. Normally, a so call 36v (actually it is 38.4v) battery is make up of 12 cell. so 12 x 3.65 = 43.8v, if you have 13cell, then 13 x 3.65 = 47.45v. A fully charged so call 36v battery, should not be higher then 44v, unless it is 13cell, which is very odd. Check you charger, what does it say the output voltage?

Ken

Ok, the only charger I have atm is the BionX one. It says 37volt, but I remember putting the voltmeter on the battery once and it said something like 41.9 volts. I believe BionX sets the charger to cut off slightly lower than capacity to prolong overall life of the battery.

I will check with ping and the other battery makers.

What is the max voltage of the add-on battery pack you have used? Obviously, the way it is being used, ie waiting for the BionX battery to use up most of its charge first, then plugging it in, there is an initial voltage disparity between the batteries, which must be around 5-6 volts at least, maybe more.

 

[Canis Lupus]

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?

Yep, thanks for your post. It was very helpful.

 

[GCinDC]

Looking at Ping's 36 volt batteries, they appear to charge to something around the 46 volt mark.

Do you know how many cell are your ping battery. LiFePO4 cell when it is fully charge, it 3.65v each cell. Normally, a so call 36v (actually it is 38.4v) battery is make up of 12 cell. so 12 x 3.65 = 43.8v, if you have 13cell, then 13 x 3.65 = 47.45v. A fully charged so call 36v battery, should not be higher then 44v, unless it is 13cell, which is very odd. Check you charger, what does it say the output voltage?

Ken

Hi Ken, your solution is brilliant. Nice work! Is it a 12 cell LiFePo4?

Correct me if I'm wrong, but I don't think Canis has a Ping yet. He's probably looking at: http://www.pingbattery.com/servlet/the-8/36V-10AH-V2.5-LiFePO4/Detail

where it says:

Specifications:
Suitable Wattage of Motor: up to 400 Watt, 300 Watt suggested
Applications: E-Bike, Electric Bike, E-Scooter, Electric Scooter
Voltage: 36 Volts
Capacity: 10 Amp Hours
Dimension: 150x105x150 mm / 5.9x4.1x5.9 inches
Weight: 3.70 kg / 8.2 lbs
Charging Voltage: 45-46 Volts
Charging Current: <5 Amps
Rated Discharging Amperage: 10 Amps
Max Continuous Discharging Amperage: 20 Amps
Maximum Discharging Current: 40 Amps
Discharging Cut-off Protection: 25-30 Amps
Lifecycle of the whole pack: >85% capacity after 1000 cycles. Lifecycle of single cell: >85% capacity after 1500 cycles, >70% capacity after 3000 cycles. (<1C discharge rate and <1C charge rate)

 

[Canis Lupus]

Yes, that's right, I haven't taken the plunge yet, and the specs you have quoted were the ones I was referring to, in particular what you have highlighted in red. Thanks again, GCinDC.

 

[GCinDC]

Here's the approach I'm taking, from here:

I have no idea how it will work, but it's more similar to ericslai's.

- Made 11Ah 7S LiPo pack (7 x 4.2V = 29.4V) (~$235 for the cells)

Still to do:
- Parallel each 4S & 3S balance taps.
- Balance charge the 7S pack on my RC iCharger
- Splice BionX external connector to BionX battery main power leads to controller (drill hole in seam, a la ericslai)
- Hook it up and test! (and pray)
- I should probably get a watt meter to put in line to watch.

Since there will be no diodes or BMS on the lipo pack, it will receive regen current and be paralleled w/ BionX pack. My hope is that the BionX charger will charge the lipo pack as well, and that the battery will not be close to drained to compensate for the shortening of the lipo lifespan by charging it up to 4.2V.

I think I will also put a switch on the connector so they don't sit together while resting.

 

[GCinDC]

PS. This is funny.

Hi Ken! Well, I finally drained my BionX battery after 54 miles of riding on level 1 & 2 at 10 to 15 mph on flat and gentle rolling hills.

54 miles w/ the BionX alone, dragging an additional LiFePo4 pack... She's a hard core cyclist! Level 1 is like the wind at your back. :lol:

How much further did she go!?

Also, I was very happy to hear about the extra power she had going up hills.

 

[itselectric]

Here's the approach I'm taking, from here:

I have no idea how it will work, but it's more similar to ericslai's.

- Made 11Ah 7S LiPo pack (7 x 4.2V = 29.4V) (~$235 for the cells)

Still to do:
- Parallel each 4S & 3S balance taps.
- Balance charge the 7S pack on my RC iCharger
- Splice BionX external connector to BionX battery main power leads to controller (drill hole in seam, a la ericslai)
- Hook it up and test! (and pray)
- I should probably get a watt meter to put in line to watch.

Since there will be no diodes or BMS on the lipo pack, it will receive regen current and be paralleled w/ BionX pack. My hope is that the BionX charger will charge the lipo pack as well, and that the battery will not be close to drained to compensate for the shortening of the lipo lifespan by charging it up to 4.2V.

I think I will also put a switch on the connector so they don't sit together while resting.

I really DO NOT recommend to do parallel lipo with Bionx pack without the BMS, and have the regen turn on. At least put a cycleAnlyst to test and review the result first. May be i am just being too caution what I have seen so far, how someone is losing big money on this setup. The worst thing could happen is your lipo blowup in your behind instead of the circuit board. With 10 of them, you are playing with fire.

You may be able get away with PL250, may be the PL250 doesn't had as much regen current like a PL350, may be you have not encounter a big steep hill like others who blow up 4 batteries in 2 weeks. May be your lipo able take high current recharge. But just one day under certain condition, the overcharge kick in, you don't know what could happen. Are u riding this setup or your wife riding this? I would not put my love one on this.

As fast as I know the worst possible condition of regen overcharge problem that I am talking about is. The battery was being dischage 1 volt or half volt off, if the battery is fully charged, this may no happen. But if it's 1 or 2 volt drop off the voltage, going down on very steep hill, with maximum regen, it had no condition because it has not reach the 42volt limit yet, as a result, it will regen at the maximum current at 40 - 60amp. In some case, you may never hit this extreme condition. Now, do you want to put your behind on a experimental risk?

Ken

 

[GCinDC]

Thanks for your honest feedback! The truth is that my wife and I haven't been getting along well, lately...

Just kidding! Of course, I would not want such a thing. That is why I was thinking about a switch - maybe a thumb press momentary type - and that she should use it only towards the end of the trip when then Bionx is weak. I will be doing many tests before she rides it, but i was tired of theories! If the voltage jumps up a lot, I diode would solve the problem, wouldn't it?

Have you seen liveforphsyics tests on lipos? He subjects them to incredible punishment before they catch fire. Also, I have a much bigger motor (9C) on a 72V 45A controller and the max regen I do is 10A... Everyone on the forum thought 60A regen would stop them so fast they would be flying out of a canon.

Thanks!

 

[ericslai]

Hi Canis,

Question, touched upon in the previous post by ericslai:

If I have a BionX battery which charges to 41-42 volts and I plug into the BionX's battery charging slot a LifePO4 or Lith Mag battery which charges to 46-47 volts, am I inviting problems?

Looking at Ping's 36 volt batteries, they appear to charge to something around the 46 volt mark.

I would not try to put such high voltage (46-47V) on the charging port of the Bionx. As I remember, the Bionx manual recommended to switch off the console before hooking up the charger. There are ecaps on board that are 50V rated (I think).

A fully charged 12S LiFePO4 is about 43V only. Ping's charger was set higher so the cells can be balanced at higher than 3.65V, something like 3.7-3.8V to boost capacity and balancing speed. The pack voltage will drop back to the nominal voltage in a few hours once the charger has been unplugged.

 

[Canis Lupus]

Thanks for the info although I must confess to being not too much the wiser. Sorry for my thickness.

 

[itselectric]

Thanks for your honest feedback! The truth is that my wife and I haven't been getting along well, lately...Just kidding!

but i was tired of theories! If the voltage jumps up a lot, I diode would solve the problem, wouldn't it?

We should have a new topic on how to kill your wife with lithium battery on an electric bike , just kidding

It is a very expensive way to prove the theory of over charge situation that I have been mentioning. And we have blown up one Bionx battery circuit board by going down the hill. If you think about, the battery BMS cut out the power, it should have shut down the entire system. But the current keeping coming back so fast from the motor, it manage to blown up the board. If you put diode in between, it block you from getting re-charge the battery, then you might as well as go with charge port parallel method.

I recently made another XLR charge port/Anderson adptor:

I used the right angle XLR connector, you can pick this up online for about $5 - 7. It is a 4 pin male plug. The company makes these connector name Neutrik, model NC4MRX. The reason to have right angle is because if you Bionx battery is mounted the onto the frame, your legs may hit the connector. So for less then $10 of parts. You can have a battery extension solution for Bionx very quickly.

Ken

 

[mwkeefer]

GCinDC,

Your still at 10A regen but you didnt' mod R12 or adapt for variable level regen right? On a 9x7 I can see upwards of 35A durring braking in negative current, for a few seconds but as speed drops so does current... quickly.

-Mike

 

[GCinDC]

...If you think about, the battery BMS cut out the power, it should have shut down the entire system. But the current keeping coming back so fast from the motor, it manage to blown up the board. If you put diode in between, it block you from getting re-charge the battery, then you might as well as go with charge port parallel method.

I recently made another XLR charge port/Anderson adptor...

Awesome adapter. Thanks for that. $6 part, $8-15 shipping lol...

The concept with the diode would be to force all the regen current into the existing battery (which is far from dead, I've learned, btw). But I was hoping to use the existing charger for both packs in parallel, rather than get a new charger... so unless there were switches here and there, it wouldn't make sense. (and i've got balancers to attach.)

Saftely and simplicity are more important though, so the adapter method, considering the success you've found, is a better idea.

Your still at 10A regen but you didnt' mod R12 or adapt for variable level regen right? On a 9x7 I can see upwards of 35A durring braking in negative current, for a few seconds but as speed drops so does current... quickly.

[/quote]

Hi Mike, I did mod R12 and have greater peaks than 10A regen (no more than 20A though) with my 9x7, but that's another bike/setup. My wife's BionX is a 24V 250 watt system.. lol. If it can generate 40A regen I'd be very surprised. But the Watts up is in the mail, so we'll find out soon!

 

[Konnections]

A few questions for you guys who are extending Bionx with a second battery through the XLR charging port. (We're looking to keep stock Bionx battery and case intact, carrying a 2nd battery when we need to extend range)

First, why is everybody using LifePo4 vs. LiMnNi? The LiMnNi has same chemistry as stock Bionx, is about half the weight of LiFePo4, and is close in price. We're looking at this one on battery space: http://www.batteryspace.com/limnni26650battery37v12ah444wh40aratewithpcmfore-bike.aspx. 37V, 12 AH for $395. Is this a good choice or is there a better option?

Also is it better to wait until the Bionx battery runs down before plugging in the 2nd battery, or just plug the second battery in at the start of the ride? A quick answer why which is better would help this newbie understand.

It might relate to the above question, but is the Bionx charging port isolated from regen? In other words, will regen current flow back into the 2nd battery through the charging port? And if it does, is this a good thing or a bad thing?

And finally, will regen still charge the Bionx battery if the 2nd battery is hooked to the charging port?

We're getting ready to do the Death Valley Century in Oct...it's basically 20 miles flat, 30 miles with 5000 feet of climbing, and then it turns around and goes back, so we'll be depeleting the battery on the way out, but will have regen available on the way back.

Thanks for your help - Terry

 

[GCinDC]

Great questions! I hope Ken can respond to most of them!

I tried to get the same LiMn cells but was told they were available to me, but I think Ken said he could get them and build the pack. I think Lifepo4 is attractive because they're, safe, w/ built in BMS, readily available, cheap to charge and affordable... And perhaps they can overvolt the bionx? Not sure about that.

I got LiPo because they're relatively cheap, I know how to build them, and was hoping to take advantage of the power they afford. (And I was hoping the bionx charger would charge them, but I've since changed course and just got the right angle XLR to hook up to the charge port...)

My guess is that the charge port is not exposed to regen current, but even if it was, a lifepo4 with an bms would not allow it (as I understand it), and would just direct the charge to the bionx battery.

 

[itselectric]

Death Valley Centur

A few questions for you guys who are extending Bionx with a second battery through the XLR charging port. (We're looking to keep stock Bionx battery and case intact, carrying a 2nd battery when we need to extend range)

First, why is everybody using LifePo4 vs. LiMnNi? The LiMnNi has same chemistry as stock Bionx, is about half the weight of LiFePo4, and is close in price. We're looking at this one on battery space: http://www.batteryspace.com/limnni26650battery37v12ah444wh40aratewithpcmfore-bike.aspx. 37V, 12 AH for $395. Is this a good choice or is there a better option?

Also is it better to wait until the Bionx battery runs down before plugging in the 2nd battery, or just plug the second battery in at the start of the ride? A quick answer why which is better would help this newbie understand.

It might relate to the above question, but is the Bionx charging port isolated from regen? In other words, will regen current flow back into the 2nd battery through the charging port? And if it does, is this a good thing or a bad thing?

And finally, will regen still charge the Bionx battery if the 2nd battery is hooked to the charging port?

We're getting ready to do the Death Valley Century in Oct...it's basically 20 miles flat, 30 miles with 5000 feet of climbing, and then it turns around and goes back, so we'll be depeleting the battery on the way out, but will have regen available on the way back.

Thanks for your help - Terry

Terry:

Many think the lifepo4 is better, but it all depend of the requirement. We use mixture of Lifepo4 and Lipo in our day-to-day conversion bike for customers. Both LiMn and LiPo are lighter weight over lifepo4. If you wanted small pack and light weight, LiMn or Lipo is the way to go.

i can't truly comment on batteryspace product, i haven't use it. But looking at the spec, it is not bad.

I think it is better run down the first battery then plug in the 2nd battery. You will be utilize the full potential energy of each battery.

the regen cannot flow back through the charge port. That is why i have suggested to avoid over charge 2nd battery that had BMS.

The regen will be fully functional and recharge the original bionx battery, but will not charge the 2nd battery through the charge port.

GCinDC:

i tried to obtain the brand new sony/konion cell, but i was told it is very hard to get. sony had put restriction on who can carry it, this is due to last sony cell laptop on fire in the news. So i did not pursuit with it.

Yes, the Lifepo4 can take higher current, it is good to handle the over charge such as regen. But it is also restricted at the BMS, unless you have programable BMS.

I hope this answered your question.

Ken

 

[Konnections]

Thanks, Ken. One further question: Can the Bionx charger be used on LiMn or Lipo batteries? It would be easy enough to hookup a female XLR plug on the charging wires of the battery...of course that would mean charging the Bionx and the 2nd battery separately, but it would save the cost of a second charger.

 

[Canis Lupus]

Thanks, Ken. One further question: Can the Bionx charger be used on LiMn or Lipo batteries? It would be easy enough to hookup a female XLR plug on the charging wires of the battery...of course that would mean charging the Bionx and the 2nd battery separately, but it would save the cost of a second charger.

Yep, this would be an advantage of sticking with the same battery type for the second battery for the BionX system: plus, in circumstances of a tour, for example, where you needed to take a charger with you, you aren't lumbering around two of them.

Edit: One little thing to keep in mind is wet weather with this proposed addition. The charging port of the BionX battery is not designed to be weather resistant unlike the other connections with the system. Some care or additional weather protecting would probably necessary to guard the connection for outdoor, on-the-go, use.

 

[Konnections]

One little thing to keep in mind is wet weather with this proposed addition. The charging port of the BionX battery is not designed to be weather resistant unlike the other connections with the system. Some care or additional weather protecting would probably necessary to guard the connection for outdoor, on-the-go, use.

Good point - being fair weather fowl from CA, we rarely ride in the rain...our plan in this case is to put the Bionx and the spare battery in a bag on the rack...should we be concerned about temperature/airflow?

 

[GCinDC]

You might be able to charge a LiFePo4 battery w/ the BionX charger, but it won't charge it enough...

Why? The LiMn cells want to get charged up to 4.2V (for the 36V kit, that's 10 cells in series, so 10 x 4.2V = 42V... that's what your charger probably says, whereas the LiFePo4 cells only get charged up to 3.85V per cell, so for a '36V' pack, in which there are 12 cells, 12 x 3.85V = 46.2V (what ping's charger is (45-46V).

Correct me if I'm wrong, Ken!

Most LiFePo4 chargers are small though, unlike the BionX charger...