doc: Add paragraph noting differences in JST polarity

Looks like the 'standard' polarity for 3.7V lipos using JST connectors
in RC aircraft is swapped from what Spark Fun uses. Note that in the
docs to try and keep people from wrecking hardware.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/doc/altusmetrum.xsl b/doc/altusmetrum.xsl
index b2677a029ed9c66f3c33b3861fddb0382ece3ee0..aa218c5cc598fffa26f33479ecc2cc8d2816a4d6 100644 (file)
--- a/doc/altusmetrum.xsl
+++ b/doc/altusmetrum.xsl
@@ -277,6 +277,17 @@ NAR #88757, TRA #12200
       apogee and main ejection charges.  All Altus Metrum products are 
       designed for use with single-cell batteries with 3.7 volts nominal.
     </para>
+    <para>
+      The battery connectors are a standard 2-pin JST connector and
+      match batteries sold by Spark Fun. Other vendors sell similar
+      batteries for RC aircraft using mating connectors, however the
+      polarity for those is generally reversed from the batteries used
+      by Altus Metrum products. In particular, the Tenergy batteries
+      supplied for use in Featherweight flight computers are not
+      compatible with Altus Metrum flight computers or battery
+      chargers. <emphasis>Check polarity before connecting any battery
+      not purchased from Altus Metrum or Spark Fun.</emphasis>
+    </para>
     <para>
       By default, we use the unregulated output of the Li-Po battery directly
       to fire ejection charges.  This works marvelously with standard
@@ -2199,7 +2210,7 @@ NAR #88757, TRA #12200
        </listitem>
        <listitem>
          <para>
-           RF interface for battery charging, configuration, and data recovery.
+           RF interface for configuration, and data recovery.
          </para>
        </listitem>
        <listitem>