Master Switches

On 4/26/2013 8:38 AM, Evan Ludeman wrote:
On Friday, April 26, 2013 11:28:31 AM UTC-4,


http://www.amazon.com/dp/B005KLOYO2/..._M3T1_ST1_dp_1



http://www.amazon.com/BALLISTIC-PERF...=pd_sim_auto_1

These are both Lifepo4 batteries that would be well suited for
glider usage. Note that the higher capacity battery has 8 cells
but still 13.2V nominal voltage. Obviously, inside are two of the
first kind batteries connected in parallel. This has to do with
the standard cell (3.3V, 7,000mah) they are using, makes sense to
me.



Herb

Herb: No! Much better off with a battery pack that includes current
limiting protection. These are starting batteries. There are
several good looking 9 - 12 AH LFP battery packs available now that
include in-the-pack battery management. Over charge protection,
under charge protection, cell balancing and over current protection
(all somewhere between "really good ideas" and "essential" for safe
LFP use). It remains to be seen how well these systems work over the
long haul. Technology is still a little young to say for certain
imo. Vendors include K2, Bioenno, Starck. If you choose to go any
of these routes, get the spec sheets, ask questions, do some
diligence.

I agree with Evan: these are totally unsuited for glider use. In
addition to the concerns he noted, also note that this particular 4-cell
unit has only 2.3 Amp hours! Beware of Li batteries offered for
"powersports" use: they often are rated by _equivalent_ lead-acid
numbers batteries, but they are ration only the cranking amps ability,
no the actual low current amp hour capacity.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz