More Konion fun !

[John in CR]

Ypedal & DocBass,

What is the proper fully charged voltage for these great little green konions? The Bosch 36V chargers stop at 40.5V, which is only 4.05V per cell. This seems too conservative to me, especially since I will discharge them at only about 1C and plan to charge at only .25C or less. I tried my 36V ping charger, which cuts off charging my ping packs at 41V, but for some reason it didn't stop charging 2 paralleled Bosch packs until getting all the way to 45V or 4.5V/cell, which seems too high. I hope I didn't harm the packs, but I quickly connected a light bulb to it and brought them back down to 4.2V, which seemed more appropriate. They ran that 100W light bulb for quite a while before the voltage came down, so it's definitely not like Lifepo4 that has no capacity at the maximum voltage fresh off the charger, and almost immediately comes down to 3.4V or so.

John

 

[Ypedal]

I charge mine at 4.2v per cell *(exact same charge profile as Li Cobalt )

LVC = 3.0v per cell

8)

 

[Doctorbass]

Ypedal took words out of my mouth! :wink:

probably some makita charger just charge at 4.1V wich is like 80% of max capacity to increase their cycle life...

I know that charging lithium cells to 4.15 would save alot their cycle life compared to the little capacity that avoid... it's a good thing to charge at 4.15V.. but to do that you will need a special charger or one that you tweak..

As long as you stay between 4.200 and 3.00V they will work no problem..

Also.. in case where you accidentally go over this range, it is HIGHLY recommanded to get back to the appropriate value with LOW current even though if it's charging up to 3.00V or discharging to down to 4.200V
Ideally at C/10

By the way.. I recovered an entire dewalt pack that was totally died (every cells was at 0.1V). i charged slowly it at 200mA and i tested it and i got the lower cell at 1950mA and the higher at 2.120mAh They are incredibble..

that's the only thing that the konion doesn't do...

Doc

doc

 

[John in CR]

Thanks for the tips guys. I'll do some testing to be sure the Bosch chargers go to only the 4.05V with multiple paralleled packs to ensure I get no heat problems, since my pack alignment gives up the ventilating fan of the Bosch charger. Then after a few trial runs with manual supervision, I'll use a timer with my other chargers to top off the cells with a target of 4.15V. That should give me a simple and fairly foolproof procedure, and delay having to learn the electronics needed to modify chargers. I'll save that for next rainy season.

John

 

[MitchJi]

Hi John,

Thanks for the tips guys. I'll do some testing to be sure the Bosch chargers go to only the 4.05V with multiple paralleled packs to ensure I get no heat problems, since my pack alignment gives up the ventilating fan of the Bosch charger. Then after a few trial runs with manual supervision, I'll use a timer with my other chargers to top off the cells with a target of 4.15V. That should give me a simple and fairly foolproof procedure, and delay having to learn the electronics needed to modify chargers. I'll save that for next rainy season.

John

Ypedal took words out of my mouth! :wink:

probably some makita charger just charge at 4.1V wich is like 80% of max capacity to increase their cycle life...

I know that charging lithium cells to 4.15 would save alot their cycle life compared to the little capacity that avoid... it's a good thing to charge at 4.15V.. but to do that you will need a special charger or one that you tweak..

Doc

In addition to Doc's quotes I think Bosch probably has a good reason for going with 40.5.

The difference between 42 and 40.5 is 3.5%.

Given the fact that its a lot easier for you to go charge to 40.5 coupled with the fact that cells charged this way will probably last quite a bit longer I don't see why you its so important to get the extra 3.5%.

 

[John in CR]

Hi John,

Ypedal took words out of my mouth! :wink:

probably some makita charger just charge at 4.1V wich is like 80% of max capacity to increase their cycle life...

I know that charging lithium cells to 4.15 would save alot their cycle life compared to the little capacity that avoid... it's a good thing to charge at 4.15V.. but to do that you will need a special charger or one that you tweak..

Doc

In addition to Doc's quotes I think Bosch probably has a good reason for going with 40.5.

The difference between 42 and 40.5 is 3.5%.

Given the fact that its a lot easier for you to go charge to 40.5 coupled with the fact that cells charged this way will probably last quite a bit longer I don't see why you its so important to get the extra 3.5%.

Mitch,

As you quoted Doc saying, the difference between 41 and 42 (10s at 4.1v & 4.2v) is 20% of capacity, so 40.5 and 42 is more like 30%, not 3.5% . It's not the percentage difference in voltage, but in capacity. Doc's 20% seemed high to me, but he's the expert, so I just accepted it. For my coast-to-coast on a single charge ride I expect to need a 4-5kwh pack, so I'll be sure to fully charge to 4.2V per cell, because even just 5 or 10% gets to be pretty big numbers with that size pack. If I get Bosch on board as a sponsor, I'll probably even overcharge the packs they provide by a little bit for some extra capacity. Even at a 500W discharge, spreading it over 50+ tool packs shouldn't do much damage as a one time shot.

John

 

[pwbset]

If I get Bosch on board as a sponsor, I'll probably even overcharge the packs they provide by a little bit for some extra capacity.

For what it's worth I was running a 10s2p string of konions at 43.5-44v for a couple days... you know... just to see. I know it wasn't "smart", but they do take an overcharge without 'sploding.. or even getting that warm. If I remember right I think Doc even let one get to 4.6v once. Whee!

 

[Ypedal]

Got 2 x 36v 3ah packs built..

the 1st pack i made just had a single + and - lead, the 2nd pack i soldered double leads, this way i can connect each pack in paralell to the next one, etc.. 3ah, 6ah, 9ah, ...

 

[MitchJi]

Mitch,

As you quoted Doc saying, the difference between 41 and 42 (10s at 4.1v & 4.2v) is 20% of capacity, so 40.5 and 42 is more like 30%, not 3.5% . It's not the percentage difference in voltage, but in capacity. Doc's 20% seemed high to me, but he's the expert, so I just accepted it. For my coast-to-coast on a single charge ride I expect to need a 4-5kwh pack, so I'll be sure to fully charge to 4.2V per cell, because even just 5 or 10% gets to be pretty big numbers with that size pack.

If I get Bosch on board as a sponsor, I'll probably even overcharge the packs they provide by a little bit for some extra capacity. Even at a 500W discharge, spreading it over 50+ tool packs shouldn't do much damage as a one time shot.

John

Hi John,

Thanks for clarifying the voltage/capacity.

If you get Bosch as a sponsor I think it would make more sense to try to get them to give you a 10% or 20% bigger pack

I think seeking sponsorship from Battery Companies (A123, LG Chem, Emoli, PSI etc.) might be more likely to be successful than a Tool Company.

 

[pwbset]

this way i can connect each pack in paralell to the next one, etc.. 3ah, 6ah, 9ah, ...

Quick question (as I'm working toward a similar thing slowly). Will the wiring cause the different strings to discharge differently or wouldn't that matter so much? Wire length differences/resistances and what-not. So far I'm working toward my first 37v9ah (10s6p) pack that I'd like to series/parallel to my eventual 2nd identical pack. I'd like to be able to series 74v for my climb and parallel 37v for my 500m decent each day for the regen.

Oh.. and let me know if you've got any spares you'd be looking to sell el cheapo. I need quite a few more cells, but am pretty darn broke.

 

[Ypedal]

Bent some thick plastic " Krazy Carpet " material over a scrap of 2x4, heated with a heat gun to make it keep it's shape.. covered the cell ends.. taped.. hot glue the wires to the pack preventing failre of the spot welds at the connected cell..

 

[Ypedal]

Covered it all with a layer of thick PVC tape.. and more glue.

 

[Ypedal]

Both these packs fit perfectly into my triangle frame bag ( http://www.mec.ca ) for 36v 6ah.

This whole bike, battery included, weighs in at less than 40 lbs !!! pedals like a fluffy cloud

 

[Alex Lar]

What kind motor you have on front ?

 

[Ypedal]

That's an " eZee " , brushless, geared motor.