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Sneak preview of the new χ1 LiPo battery board

PostPosted: June 9th, 2011, 12:36 pm
by amb
[Updated October 21, 2011]

NEWS: χ1 is now released and available from AMB audio shop. Please visit the official χ1 website for full information about this project.

As mentioned in a post elsewhere in this forum, MisterX and I are working on a LiPo battery board that could be fitted into the Mini³ portable amp. It's called χ1 ("chi 1").

(If you can't see the whole picture, stretch the browser window wider)
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This board increases the run-time for the Mini³ high performance edition to more than 23 hours, and the extended runtime edition to over 50 hours. It also reduces the charge time to less than 1.5 hours. Full smart-charging and protection will be included on the board. The nominal battery voltage is 7.4V (two 3.7V 600mAH cells in series). The selected LiPo battery is commonly-available and low cost (they are designed for use on RC helicopters).

To use this board, the charging circuit portion on the Mini³ must be depopulated. The two boards will be mated to each other similar to the γ1 DAC in the Hammond case, the interconnection will be pin header/receptacle through the 7812 regulator's pads on the Mini³.
The "charge" LED on the back panel is bi-color, and will glow green when charging, and turn off when charging is complete. It will glow red if there is a fault. The external wallwart specified for the χ1 is 9VDC regulated, with a current rating of 1A or higher.

The following is the current PCB layout:

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The blank board areas are actually "no fly zones" to clear the tall parts on the Mini³ board, such as the volume pot, input /output jacks, DC power jack, and electrolytic capacitors. The usable board space is essentially full.

Here is the schematic diagram:

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The selected charge management controller is Microchip MCP73864 and additional battery protection is provided by Texas Instrument UCC3911DP-3. Both are in SOIC-16 package. The battery is two series-connected 3.7V 600mAH lithium-ion polymer cells (Walkera HM-4G6-Z-37, HM-4#6-Z-34 or equivalent, for Walkera 4#3, 4#6, 4G3, 4G6 RC helicopters). These are commonly available from RC hobby retailers and online. The two cells fit perfectly in the Mini³ Hammond enclosure, where the 9V NiMH battery occupied.

The wallwart for use with the χ1 must be a regulated type, DC 9V output, rated no less than 1A load current. Note that this is different than the 15V-24V 300mA unregulated unit specified for the standard Mini³.

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 9th, 2011, 3:13 pm
by tranhieu
It's so cool you never run out of enthusiasm and creativity Ti, even though I don't own any mini3!
Btw, that name reminds me of the chi square distribution :D

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 9th, 2011, 5:07 pm
by amb
Thanks tranhieu, MisterX should get the credit for coming up with this idea, I just happen to think that it's very good.

The name has multiple entendres. It obviously follows my style of using a Greek letter and a number, but "chi" (氣, also spelled as "qi", as in qigong) is Chinese for air, but more accurately, energy or "inner force", which is rather appropriate for this board. And then the letter for chi is "χ", for MisterX! ;)

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 9th, 2011, 11:49 pm
by MisterX
Teaser pic for an idea how the two board thing looks. :geek:


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Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 12:15 am
by wotts
Very cool. I am going to have to look more into the Mini3. Thanks for sharing!

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 6:22 am
by jr41
This is too cool 8-) An awesome upgrade - thanks AMB and MisterX!

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 11:22 am
by rockcod
amb wrote:Thanks tranhieu, MisterX should get the credit for coming up with this idea, I just happen to think that it's very good.

The name has multiple entendres. It obviously follows my style of using a Greek letter and a number, but "chi" (氣, also spelled as "qi", as in qigong) is Chinese for air, but more accurately, energy or "inner force", which is rather appropriate for this board. And then the letter for chi is "χ", for MisterX! ;)


Ti & MisterX, wonderful idea!!! And Ti's explanation on "chi" is right on the spot.

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 11:47 am
by vixr
will there be any benefits beside faster charging?

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 11:53 am
by amb
vixr wrote:will there be any benefits beside faster charging?

Read my intro post above. ;)

Re: Sneak preview of the new χ1 Li-Po battery board

PostPosted: June 10th, 2011, 12:30 pm
by flynhawaiian
I was just about ready to purchase the m3 board. Glad I waited a bit. If you need a beta tester let me know :D