[Noisebridge-discuss] [HBRobotics] High density 2S LIPO with Charge/Discharge cutoffs - Brainless Battery Pack?

[Jake]

It looks like it DOES contain a charging control circuit after all:

"..automatically cutoff once the pack drops to 2.85v per cell ensuring the
  battery will not be damaged if you accidentally leave your transmitter
  switched on. The voltage protection circuit will also restrict charging
  to 4.2v per cell ensuring the pack can never be over charged."

http://www.hobbyking.com/hobbyking/store/__19481__Turnigy_4000mAh_Spektrum_DX8_Intelligent_Transmitter_Pack..html

-jake

> For all intents and purposes, a 9v DC source should be all that is 
> needed to charge this pack.

I don't know specifics, but I'm inclined to believe that isn't the case. 
The protection circuits are only there to prevent overcurrent and 
over/under voltage conditions. They don't do any charge current regulating 
and I'm pretty sure LiPo cells want that. At least, I do know that even 
though all of Sparkfun's single cell battery packs have protection 
circuits, they always say you need a lipo charge circuit and I've never 
heard anything about charging a LiPo off straight DC. Given how handy that 
would be, I'm inclined to believe I would have heard something about that.

So like I said, I don't know anything for sure, but if you don't either,
then there's probably more to it. Either way its something you should
definitely be sure of before trying.

-Taylor

> As long as you only need to provide 7.4 volts at 8 amps, you should be
> fine.  This pack only has two leads.  That's for voltage in and out.  No
> LIPO charging equipment required.  My expectation is that there is some
> circuitry in the pack that does this for you.
>
> On Wed, Sep 14, 2011 at 11:04 AM, William Garrido <
> blackspartan117 at gmail.com> wrote:
>
>> Nice! This would be great to drive my motors. I doubt my charger for 
LiPo
>> would work, anyone know if a small LiPo charger for 2S? I have my
>> chargers embedded on my robot.
>>
>> Or even my MC, would get rid of the need for a stepup! Too bad its not
>> 6AH.
>>
>>
>> On Wed, Sep 14, 2011 at 10:10 AM, Corey McGuire <coreyfro at 
coreyfro.com>wrote:
>>
>>> Need to replace NICAD/NIMH packs, but are afraid of the complexity of
>>> LIPO or added charger cost?  This pack might fit your bill.
>>>
>>>
>>> 
http://www.hobbyking.com/hobbyking/store/__19481__Turnigy_4000mAh_Spektrum_DX8_Intelligent_Transmitter_Pack..html
>>>
>>> Sparkfun and other places have single cells that have such cutoff
>>> circuitry to protect your single cell from being charged too high or
>>> discharged too low, but this is the first 2S solution I've seen. 2S 
LIPO is
>>> a sweet spot because it nearly perfectly matches the voltage 
characteristics
>>> of 6 Cell NICAD/NIMH packs, which are common everywhere.  This could 
be a
>>> drop in replacement for such needs.
>>>
>>> One draw back, it appears to provide only 8 amps of current.  This is, 
no
>>> doubt, because the circuit that regulates charge is in line with 
whatever
>>> you plug it in to.
>>>
>>> --
>>> You received this message because you are subscribed to the Google 
Groups
>>> "HomeBrew Robotics Club" group.
>>> To post to this group, send email to hbrobotics at googlegroups.com.
>>> To unsubscribe from this group, send email to
>>> hbrobotics+unsubscribe at googlegroups.com.
>>> For more options, visit this group at
>>> http://groups.google.com/group/hbrobotics?hl=en.