• From: Ames, IA
  • Registered: 2008-01-13
  • Posts: 9

Topic: 9V socket, LiPo battery

It's me again,

I've been doing some micro-controller development in the past.  I usually have an LDO or 7805 in-line on input from my battery source.  In this case, I have a high capacity Lithium Polymer battery that would easily fit inside the Chumby.  It lasts a long time (runs a remote aircraft for 40 minutes).  Would it be safe for me to solder a 9v connector and experiment -- it is 7.2 volts.  Thanks!

Alternatively, I may try to develop a charging circuit to go between the battery or add a vreg and fuse for safety.  I'll be interested to hear some thoughts.  Hope everyone is having fun.

-Loren

just go with it

loren1979's Website

  • From: Singapore
  • Registered: 2006-08-26
  • Posts: 188

Re: 9V socket, LiPo battery

Applying 7.2V to the chumby would not adversely affect the chumby. The internal step-down switching regulator can operate correctly down to 5.5V.

Of course, be sure to get the polarity right and obey the proper safety precautions when dealing with lithium polymer batteries, etc. etc. The chumby has an internal fuse and reverse-bias protection diode. The reverse-bias protection network can shunt a lot of short-circuit current, which could cause a fire hazard if the battery can't handle the short-circuit load.

7BAA 2E53 01C1 DCFF 497B  E7F0 9699 A303 78F0 D9B9

bunnie's Website

  • From: Ames, IA
  • Registered: 2008-01-13
  • Posts: 9

Re: 9V socket, LiPo battery

Thank you bunnie.  I appreciate the fast response and insight.  I'll take a look at the schematics to ensure proper polarity.  Charging is another arena that I'd like to tackle at some point, but in my experience LiPo generally hold a charge for quite some time.  The main goal for me is emergency battery backup.  I'll try to report back my experience (runtimes, etc).  I just want to avoid a low voltage condition, which could damage the processor.

All the best,

-Loren

just go with it

loren1979's Website

4 Reply by hoyeboye (edited by hoyeboye 2008-05-15 17:02:59)

  • From: Kansas City
  • Registered: 2008-05-01
  • Posts: 59

Re: 9V socket, LiPo battery

bunnie wrote:

Applying 7.2V to the chumby would not adversely affect the chumby. The internal step-down switching regulator can operate correctly down to 5.5V.

Not that I doubt you, bunnie, but the wiki says the chumby runs from 6.5 VDC to 14.5 VDC. If I create a battery pack that is 6 volts(which would fit better than the 9 volts I was planning), would that create any problems?

(sorry to resurrect a dead thread)
-----------------------------------------
EDIT
-----------------------------------------
Forget my prior post-I miscalculated my voltage. I'll post the info on my battery pack after I see how long it lasts.

  • From: Singapore
  • Registered: 2006-08-26
  • Posts: 188

Re: 9V socket, LiPo battery

6.5V is engineering margin :-)

There is a UVLO that will shut down the chumby when the voltage drops to under 5.5V give or take a hair. If your battery pack can actually source 6V (rock solid) you should be okay. The trouble with most battery packs is that if they are unregulated, the internal series resistance of the pack will cause some droop on the voltage. A 6V pack can easily dip to under 5.5V under high load conditions (e.g., loud bass on the speakers while rendering video and streaming wifi)...however, if you have a regulated 6V I've run the chumby at that voltage before and it's okay with that!

7BAA 2E53 01C1 DCFF 497B  E7F0 9699 A303 78F0 D9B9

bunnie's Website

6 Reply by Demon Knight (edited by Demon Knight 2008-05-19 03:56:31)

  • Registered: 2008-05-19
  • Posts: 2

Re: 9V socket, LiPo battery

Hey all,

I've found a very cheap Li-Ion battery seller on ebay. I've received my battery and although it's too large to fit inside with the casing, it does make a nice base with some velcro.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? … %26otn%3D4

Alternatively, anyone tried using 6V Receiver packs for RC models in series to produce 12V? Dimensions are:
85 x 30 x 18mm. Might be able to fit inside in bottom slit?

http://cgi.ebay.co.uk/VENOM-RACING-1600 … 286.c0.m14

  • From: North East UK
  • Registered: 2008-03-28
  • Posts: 156

Re: 9V socket, LiPo battery

Demon Knight - how long does your Chumby for on that $10 12V battery ?

quizengine's Website

  • Registered: 2008-05-19
  • Posts: 2

Re: 9V socket, LiPo battery

It lasts roughly 4 hours just playing music