36V HEADWAYS (signalab bms) + 22V LIPO (booster pack) WIRING

[BRICKTOP]

Hi Everyone, I dont post often however I spend alot of time browsing the forums. Probably too much time, I would say its an actual obssession these days

Ive got 36v headway pack with a ping signalab bms v2.5. Ive also got a 22V 6s turnigy nanotech 8000mah that I would like to wire in series with my headways as a "booster" pack.

I understand I may need to wire a schottky diode in place to prevent damage to my bms in the event of the bms cutting power. Ive been looking around all over for a clear explanation on how exactly to wire a schottky diode but to be honest im a bit clueless and probally have read many clear explanations but just too stupid to realise.

these are the diodes I plan to use http://www.sourcingmap.com/40cpq100-type-150v-40a-power-switching-fast-recovery-rectifier-diode-p-147280.html?currency=GBP&utm_source=google&utm_medium=froogle&utm_campaign=ukfroogle

I drew this little picture of where im guessing the schottky diode needs to go after what ive read throughout the day (yep ive been reading about these shitty diodes all day). Please can anyone tell me if this looks correct and if its the best way to do it. Or have I actually gone mad?

BATTERY WIRING.png

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[BRICKTOP]

Can anyone help me??

Ive been reading this thread by fechter: http://endless-sphere.com/forums/viewto ... =16&t=1312

Many lithium battery packs contain an integrated battery management system (BMS) that controls charging, protects against overdischarge (low voltage), and protects against over current during discharge. "Duct tape", Ping, DeWalt and many others have a battery management system.

When attempting to put packs containing a BMS in series, there is a potential problem. If the BMS ever trips and goes open due to an overcurrent, the transistor switch in the BMS will be exposed to the full voltage of all the packs combined, possibly taking over the rated voltage for the part and causing destruction.

The way to avoid this problem is to place diodes across each pack's output terminals to keep the voltage from going higher than the BMS was designed for.

If one pack trips, the diode will conduct, allowing voltage from the other pack to pass to the controller. The tripped pack will not "see" more than its own voltage, plus the voltage drop in the diode.

For a typical 36v pack, you'd want to use something like a 50 volt, 50amp rated diode.

Since the diode is only working when a pack trips, low losses are not very important and you can use just about any diode with a high enough rating. Note the diodes are placed across the battery in the normally non-conducting direction.

fechters diagram:

bms packs.png

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Now looking at fechters diagram, im guessing I have the diode in the correct place?? But do I need a diode on the lipo brick aswell?

I suppose my question is "how do you wire two batterys in series when one has a BMS and the other one doesnt?"

[BRICKTOP]

ANYONE???

[DAND214]

I don't get the reason for the diode. I would be concerned about blowing up your controller and maybe overdischargeing the LiPo.
36v what AH is the headway? If it's much higher than the LiPo it will still be going when the LiPo is dead and gone.

Most controllers have 63v caps inside unless set for higher voltages. A 6s lipo hot off charger is 25v a 36v LiFe will be 40v plus, so that can damage your controller.

I'm sure others will step in as soon as they can.

Dan

[BRICKTOP]

Hi dand214,

Im using a 36-72v crystalyte analogue controller so shouldnt have any problems around 65v. Also the headways are 16ah cells. My plan is to attach a low voltage alarm to the LIPO so I can disconnect it when its approaching empty. Would that be sufficient protection plugging a voltage alarm on the lipo and manually disconnecting it when it beeps?

I believe the reason for needing the diode is to prevent damage to the BMS in the event of the BMS cutting out due to lvc or exceeding max amp draw. ???


Heres my story, I started out with a 48v headway pack in the triangle of my frame (cannondale badboy), however after 25 (fun) miles I decided the frame was just too light and weak too hold an 8 kg battery and the torque arms were awkward and I didn't have much faith in them. So I decided I needed another frame,one made of steel, however there's not many frames out there that are made of steel, have disc brake mounts, and that fit a 48v 16ah headway battery in the frame. Hence why I have now reduced the size of the headway pack down to 36v.Now it fits into quite alot of bike frames with an open triangle design.

I dont want to go all LIPO as ive already spent a fortune on parts for this project, and theres no way I can justify spending more money on batteries at this time, and also I really dont want the hassle of managing a load of LIPO. I like the headways and signalab Bms as its plug and play, I can set it on the charger and walk away. And using a BMC V2T hub motor the 36v 16ah headways should achieve around 20mph and 30 mile range im guessing, which is pretty decent.

However, I would also like the option to be able to plug in a turnigy nanotech 8000mah (that I already own) too boost my voltage and make some of those miles more fun/ help on the hills etc. I understand that 65v is quite a high voltage for a bmc motor however I also have a cycle analyst and plan on limiting amps to around 15- 20 amps to keep overall wattage below the recommended 1500w. Alternatively I could split a 6s 8ah Lipo pack and reconfigure the cells to make a 3s 16ah 12v pack and series that with my 36vheadway, or alternatively I actually have two LIPO bricks, would it be better to parallel my lipos for 16ah then connect in series to the 36v 16ah headway?

Basically my project was a failure due to my choice of bike frame, and now im just trying to get something working with the parts I have (as I have alot of parts), and not spend anymore money until I get some actual use out of my bike. Is what I want to do feasible? And what would you guys do in my position? Buy a car? LoL

[dnmun]

i would not connect a lipo pack in series with lifepo4. you need protection for any lipo pack too. both charging and discharging. even more than with lifepo4 since they just die, not ignite when overcharged.

[999zip999]

Take your time and find an old steel mtb with good componets. If you look on craigslist you might find what you need. I build a card board box to make sure it fits in the frame when you go looking. And run it at 48v

[999zip999]

Dlb post ?

[BRICKTOP]

I plan on disconnecting the LIPO pack for charging. Also I would be fitting a low voltage alarm onto the LIPO pack and disconecting it at 3.3v per cell. And I dont plan on overcharging it or over discharging it, and ill be buying a decent balancing charger. I thought there was a few people on these forums using LIPO boost packs in series with Ping batterys? DNMUM... Would the low voltage alarm and a decent balancing charger be enough protection for the LIPO?

Also I did the whole cardboard box idea, and I was searching for a steel frame with disc brakes and room in the triangle for 48v headway for probally the last nine month (not constantly lol). I have since give up and decided I cannot fit more than 36v into the frame. This opened up my choice of frames alot! I have just recently won an auction on ebay for a 20" steel frame "On One 456 Summer Season". Will fit the 36v headway nicely.

I would be happy at 48v as I did test it at that voltage in the cannondale at it was plenty fast. Im not sure ill be happy at 36v. Is there really no way for me to use one of these 6s LiPo in series? I dont mind reconfiguring the pack also, as im pretty handy with a soldering iron. Maybe turn it into a 3s 16ah pack and wire that in series with the 36v 16ah headway for 48v 16ah?

I dont understand why this is such a bad idea.

[dnmun]

the lipo is much higher C rate in series, so the BMS on the lifepo4 would be shutting down with the higher current surges. if you can prevent the lipo cells from overcharging, or over discharging, might as well try it.

you don't need to worry about putting diodes in parallel with the packs, and especially not in series.

[999zip999]

Winerboy does a Ping & lipo combo. That's all the help I can give.

[999zip999]

How about 36v in the triangle and 12v on the rear rack. I just love 48v or more.

[BRICKTOP]

yeah I dont think 36v will be enough, especially since ive already experienced the power at 48v

I thought I could put the 12 headway cells in the frame (2 rows of 6) for 36v, then I was gonna stuff the controller in an under seat saddlebag type thing. There is also room in that bag to nicely fit alongside the controller a 6s lipo brick that I would of plugged in until it ran out then continued on 36v till the headways were done. From reading around the forums I thought there was more people using "booster" packs in this way. Maybe I was wrong and this is just a bad idea

Anyways Ive been messing around with the HEADWAY cells today and pulled off all the plastic blocks from the cells. Ive actually reconfigured the cells to a row of six in the middle with a rows of 5 on each side. So its 3 cells wide and 6 cells long but ive kind of staggered them so its not as wide as 3 cells, and definately not as wide as 3 cells using the headway building blocks. Originally I didnt want to go more than 2 cells wide (84mm in blocks) to not affect pedalling, but its only increased my pack size by 30mm, to 114mm wide now, from 84mm before, so not too bad. Pedalling might be a little bow legged but to be honest at 48v it doesnt take much pedalling

So it looks like im back to using the 16s 48v headways with signalab 2.5 BMS. Thanks for everyone wo gave thier input. If theres anyone who reads this who is actaully using a LIPO "booster pack" with thier pings/headways Id love to hear how thats going for you. Ive got 2 x 6s turnigy nanotechs 8000 mah that I dont really have any use for atm. Maybe ill make a lightweight pack to use in place of the headways for when I dont need the distance. 45v 8ah. And only 2 kilo instead of 8kg.

[999zip999]

How many amps you going to run it at ?

[fechter]

The diodes you selected look dandy. Normally the diodes don't do anything. If the BMS trips on LVC or overcurrent, the diode prevents it from getting 'charged' in reverse from the other pack and destroying the BMS. Hopefully hitting LVC doesn't happen very often. If you're really sure the BMS will never trip, you don't need the diodes. If the lipo pack doesn't have a BMS, it doesn't need a diode.

Both packs should have some kind of voltage monitoring.

[BRICKTOP]

999zip999... Im using a Crystalyte 25A controller, and im using a cycle analyst also so could limit the amps if I decided to increase voltage as I understand these motors can be problematic over 1500w.

Thanks Fechter, thats exactly what I was looking for. Although Im pretty certain my BMS wont trip, I cant be 100% certain. I would like to be certain that if it does trip, it will definately come back on

I see no reason why not too wire the diode in for protection as its serves no function under normal operation anyway and its like a 2 min job soldering it when you know how and then atleast its there if its needed. My only problem now is I dont exactly know how The problem I have is I need to join 2 wires to the diode but its got 3 pins. Ive never wired a diode like this before but Im guessing it must be wired in a certain direction also.

Fechter, did you take a look at my schematic "battery wiring". I understand now I only need 1 diode, but is it connected in the correct place in my circuit diagram. Or better yet, would it be possible for you to draw me a quick sketch in paint and post it up, just a picture of a 3 pin diode and perhaps label the pins (where they connect to) for me so I can be 100% im not doing something stupid. It would be mucho appreciated.

Im thinking I may use it 48v with the headways for a while but if everything goes smoothly there, I may attemp reconfiguring a 22v 6s1p 8ah lipo so it becomes a 12v 3s2p 16ah lipo. That could be a nice little boost pack for around 60-65v. Although being a 16ah boost pack would make the diode crucial.

[fechter]

Your diagram has the diode in the right place.
Here's the datasheet: http://www.vishay.com/docs/94210/94210.pdf

You would connect the two outer pins to each other with a jumper wire to put the two internal diodes in parallel. Then your main connections go to the center pin and the two outer pins. I'll try to make a drawing of this, but if you look at the datasheet, you should be able to see how it goes.

[BRICKTOP]

Thanks Fechter, thats awesome, its explained all my questions.

Ive just shrink wrapped my headway cells with 60mm heatshrink and next im thinking I may stick them all together with something, im thinking maybe silicone. My ebike project has had to take a back seat this last week but im keen to get on and ill make a post with some pics when its a little more completed so everyone can check out my creation

Thanks again to everyone who commented.

[Secret1511]

Thanks Fechter, thats awesome, its explained all my questions.

Ive just shrink wrapped my headway cells with 60mm heatshrink and next im thinking I may stick them all together with something, im thinking maybe silicone. My ebike project has had to take a back seat this last week but im keen to get on and ill make a post with some pics when its a little more completed so everyone can check out my creation

Thanks again to everyone who commented.

I late reaction, but did it work???