LV2 Battery Pack!
Summary:
In the long run, we plan on using commercially availble Lithium Ion battery packs with on board charge controllers - called "smart batteries" - for LV2. We've chosen this so that we don't have to start on a charging system from scratch as there are many IC solutions for the charging smart batteries. In the short run we may need to use primary Lithiums since the charger will take time to develop.
Some documents:
PrimaryVsSecondaryDiscussion (which is better?)
See the Battery Chemistry Comparison and Selection document in PDF and Word formats for our decisions on the battery pack.
We'll use a CAN node to to communicate battery state of charge to the FC as well as hold the battery charging IC.
Power Consumption by circuit:
- FC: PS: 14mA
- FC: PS+MOPS: 465mA
- FC: PS+MOPS+PCMCIA: 509mA
- FC: PS+MOPS+PCMCIA+SanDISK: 516mA
- FC: PS+MOPS+PCMCIA+SanDISK+Lucent Receive:
- FC: PS+MOPS+PCMCIA+SanDISK+Lucent Transmit:
Battery Chemistry Links:
- Panasonic Overview of Li-Ion Batteries.
Smart Battery System (SBS) & the System Management Bus (SMB)
- Nice overview: http://www.semiconductors.philips.com/publications/content/file_380.html
- Smart Battery Implementation forum: http://www.sbs-forum.org/
- System Management Bus! http://www.smbus.org/
- Broad intro to Smart Batteries: http://www.nexergy.com/Reflib/Smart_Battery_970127.html
Touches on battery self-protection, factors influencing the selection of interface bus protocol, etc. Written in Jan-97, so it may be obsolete by now. I'll know as soon as I do more research. :-) - Smart Battery-related White Papers: http://www.semtech.com/developer/techpap.html
I've yet to read through most of these, so their applicability to our cause is still unknown.
Ready-Made Solutions were discovered in a fit of web-browsing. As it turns out, reference designs for Smart Battery set-ups are available from a number of sources:
- PIC Microchip peddles their "PICREF-5," an "SMBus level-3 battery charger/selector reference design based on the PIC 16C73A." The Microchip website makes available the sales blurb, schematic, etc. from their Reference Designs page.
- Linear Technology offers a single-chip Smart Battery charger controller, which could be used to further simplify the PIC-based reference design.
LiIon/LiPo links:
- http://www.cheapbatterypacks.com/ - "iRate 2600" 4.6 x 56 x 90 mm @ 2600 mAHr, 3.7 V, 52 g, $22.50
- Video of battery failure: http://mywebpages.comcast.net/tedcooper/LiExplosion.mpg
- Discussion of ?LiPo safety: http://www.rcgroups.com/forums/showthread.php?t=209187