LiPo battery packs

[DirtyGinge]

Mark, did you mention lipo ?

Biggest problem I find with lipo is its eagerness to catch fire !!.......really easy to puncture/damage etc...should be alright thought in a metal case

When I get paid

[Magzy]

Ginge - here's a useful n00b lipo thread http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=19956

how to set it up, avoid fire (caused by overcharging)and bricking cells (caused by over using) - some useful info in there if you go down that route let us know how you get on (and take pics !)

seeing like these lipo batteries are cheap and lighter than Lifepo4 they pack a mean punch but at a cost of fire risk, setting up, maintaining and all the other overheads. It's only for experts it would seem...

[o00scorpion00o]

Mark, did you mention lipo ?

Biggest problem I find with lipo is its eagerness to catch fire !!.......really easy to puncture/damage etc...should be alright thought in a metal case

When I get paid

Lol Yes I did happen to mention Lipo once or twice! 


A lot of the guys on ES seem to have great faith in it these days, and it's even starting to appear in laptops, I think one oif the thinkpads can charge to 80% in 30 mins, I'm sure it could be done in 5 but I bet they are playing it safe!

I think they are safe enough and most problems were from over charge or discharge! But yeah, don't puncture it lol 


Mark

[o00scorpion00o]

Ginge - here's a useful n00b lipo thread http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=19956

how to set it up, avoid fire (caused by overcharging)and bricking cells (caused by over using) - some useful info in there if you go down that route let us know how you get on (and take pics !)

seeing like these lipo batteries are cheap and lighter than Lifepo4 they pack a mean punch but at a cost of fire risk, setting up, maintaining and all the other overheads. It's only for experts it would seem...

I'm still waiting for Hobby King to get the batteries!

I'll take pics when I get it all up and running which could be a few weeks yet!


Mark

[DirtyGinge]

Yup, been working with it a lot at work recently......fully charged lipo with a small tear, and its run for the door with battery in hand.......

Regarding your old pie, whats the max continuous you used to run at with your infineon ?

[o00scorpion00o]

HAHA stop trying to scare me! 

Max continuous was about 40 amps, I can't remember what the peak was!

But as I said many times before, the current drops of quickly once up to speed, though of course very long steep hill climbs saw 40 amps being sucked from the battery, poor ping!  lord knows what the phase currents were, but I think it's usually 2-2.5 times the battery current!


Mark

[DirtyGinge]

Not trying to scare you buddy, I know you know what youre at ...btu no, actually happened a lot....we had a fault with faulty batch of batteries failing at 14C, but fine at room temp...had to do a lot of dissasembly of casings etc for batch codes, then began a fight with the manufacturer

Nothing at all to do with ebikes though

[o00scorpion00o]

Haha you mean, you hope I know what I'm at 

They weren't hobby king batteries were they? What batteries were they?

[Just]

Some how the Hobby King LiFePo4 batteries are lighter and smaller them from other manufacturers... I dont' know why...

As for the performance, they put 30C limit on the continuous current - pretty good! And price is very cheap...

So, there is the catch?

P.S. the come  without BMS, just with wires from the cells for proper balancing...

[DirtyGinge]

yep, the idea is that your charger does the balancing

Nope, not hobbyking, polaroid as it goes.....

Truth is ( as the industry knows) , currenntly the only way to increase the watts per kilo is to decrease the insulation ( safety margin)

Ive dropped my li-ion before....scared me a little, but had it been lipo, would have dived out the window

[Just]

"the idea is that your charger does the balancing" - but what's about the discharge control?

Do the regular BMS manage the cells while the discharge? I mean, do the BMS protect the cells from the voltage drops when they are over-discharged?

What's purpose of the BMS while the battery is discharging?

[o00scorpion00o]

"the idea is that your charger does the balancing" - but what's about the discharge control?

Do the regular BMS manage the cells while the discharge? I mean, do the BMS protect the cells from the voltage drops when they are over-discharged?

What's purpose of the BMS while the battery is discharging?

If one cell's voltage drops too low the bms shuts off the battery to prevent that 1 cell from being destroyed!

There is not yet a good solution to LiPo bms afaik?

usually with LiPo you get cell monitors that sound an alarm to notify you that one cell has gone too low!


Mark

[Just]

Recently I've got LiFePo4 batteries from HobbyKing - 4 batteries of 4S2P 4200mA each one, connected them in serial and got a single pack of 48V4.2Ah just to try it.
In fact, with continuous current of 15A (30A in peaks), I would able to run with my bike for just about 2-3km on the flat - that's all.
The pack was  without BMS.
After I came home and checked the original battery packs, then I realized what the first cell (one, which is connected with its negative pole to the "battery ground") in each pack was over-discharged to about 1.5V-1.9V. Rest of the cells were discharged to just 3.1V. And this phenomena I met in each pack!
Is everybody know why this phenomena happened? Is it a common to happen?
In fact, just because the cells were not discharged identically and one cell was discharged deeply, the whole package shut down! frustration...
But, this pack was  without BMS...
May the same thing happen with batteries with BMS.
As for me, BMS should manage discharging of the cells as well as charging.

[Just]

If several equal cells were charged and balanced to the same voltage, why one of them should be discharged faster than others?
Why the BMS don't balance cells while the discharge process? If so, the battery might be more effective and don't shut down itself just because one over-discharged cells. If BMS manage discharge currents from the cell, then voltage drops on the all cells will be equal. This would allow to increase the battery life time (at least to increase an effective discharged capacity).
Am I wrong? If not, why nowadays BMS do not do so?

[Just]

In other devices I also paid attention that the battery, which are connected in serial, do not discharged equivalently.
Does anybody know why?