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

Fri Sep 16 13:55:14 UTC 2011

There comes a point where expensive technology is replaced with simple
solutions.  The world uses LIPO batteries on a daily basis with out knowing
it. These batteries are in your phones, they are in toys, they are in
laptops, they are in tools.  We work with them on a daily basis.  These
problems are not hard to solve.

Understand, this is a 4 amp hour LIPO. While 9v power sources that exceed 4
amps are not unheard of, most people only have wall wart power supplies that
rarely exceed the hundreds of milliamps.  What is the danger of trickle
charging a LIPO that has internal balancing?  Consult your laptop.

Yes, LIPO fires are serious and real.  They are also not going to happen
here.  Seriously.

As far as other Lithium Ion Batteries, such as A123 (aka Lithium Iron
Phosphate), they need balancing, too.  Not to mention, the original lithium
ion batteries were even MORE volatile than LIPO.  LIPO is a lesser volatile
battery chemistry than other Lithium Ion technologies.

Seriously, 9v wall wart + this pack = done deal.
On Sep 15, 2011 11:43 PM, "Steven Nelson" <teamkiss2001 at gmail.com> wrote:
> The wise builder should invest in a proper Smart balancing charger before
> using Lithium technology and you should remove the batteries from your
> precious machine when charging. Also Lithium Ion or A123 packs have been
> proven to be safer than the LiPoly types even under very severe
conditions.
> Being cheep with Lithium battery technology can be expensive on a bad day.
> Definitely read all reviews before investing in these battery systems...
> This is great technology but you have to treat it different (more
> respect) than most other battery types to prevent problems with some of
the
> cells. Other than that these baby's should impress you with their
> perfomance. I've seen them do amazing things for their size and weight..
>
> On Wed, Sep 14, 2011 at 6:54 PM, Corey McGuire <coreyfro at coreyfro.com
>wrote:
>
>> You folks are absolutely correct and I was unclear.
>>
>> These batteries are rated to be charged at 1C, which is in the product
>> description. What this means is, the battery must be charged at a rate
that
>> is equal to or less than the capacity of the battery, so less than 4
amps.
>>
>> As a rule of thumb, all LIPO's are usually charged at 1C or less. This
>> means, no matter the capacity, you do not want to charge a LIPO battery
at
>> such a rate that an empty battery would be charged in less than an hour.
>>
>> Sorry about not mentioning that.
>>
>> To understand how the circuitry in this battery works, we need to
>> understand how this battery was designed to be used. This battery is
meant
>> to be a drop in replacement for a transmitter battery. The transmitter
can
>> recharge the battery when wall power is provided. The transmitter then
>> trickle charges a 6 cell NIMH pack over two leads.
>>
>> This battery is meant to do exactly that. It is meant to replace a
>> bonehead simple NIMH pack in a transmitter in an off the shelf fashion.
>>
>> So, how would one safely use this pack? Trickle charge it at 9V at less
>> than an amp. It will take all night to charge, but it should charge
safely.
>> On Wed, Sep 14, 2011 at 1:59 PM, Taylor Alexander <tlalexander at gmail.com
>wrote:
>>
>>>
>>>
>>>
>>>> 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.
>>>>>>
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>>>>>>
>>>>>
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>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Everything should be made as simple as possible, but no simpler -
Albert
>>>> Einstein <http://en.wikipedia.org/wiki/Albert_Einstein>
>>>> Simplicity is the ultimate sophistication - Leonardo Da Vinci<
http://en.wikipedia.org/wiki/Leonardo_Da_Vinci>
>>>> Perfection is reached not when there is nothing left to add, but when
>>>> there is nothing left to take away - Antoine de Saint Exupéry<
http://en.wikipedia.org/wiki/Antoine_de_Saint_Exup%C3%A9ry>
>>>> Keep It Simple Stupid - Kelly Johnson<
http://en.wikipedia.org/wiki/Clarence_Johnson>
>>>>
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>>>>
>>>
>>
>>
>> --
>> Everything should be made as simple as possible, but no simpler - Albert
>> Einstein <http://en.wikipedia.org/wiki/Albert_Einstein>
>> Simplicity is the ultimate sophistication - Leonardo Da Vinci<
http://en.wikipedia.org/wiki/Leonardo_Da_Vinci>
>> Perfection is reached not when there is nothing left to add, but when
there
>> is nothing left to take away - Antoine de Saint Exupéry<
http://en.wikipedia.org/wiki/Antoine_de_Saint_Exup%C3%A9ry>
>> Keep It Simple Stupid - Kelly Johnson<
http://en.wikipedia.org/wiki/Clarence_Johnson>
>>
>> --
>> 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.
>>
>
>
>
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