Campbell Scientific CR7 Measurement and Control System - Manual (Page 10)

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CAUTIONARY NOTES
The typical current drain for the CR7 is
approximately 100 mA while executing and 8-10
mA quiescent. Do not allow the lead-acid
batteries (2.5 Ahr) to drop below 11.76 V as
irreversible battery damage may result.
An external battery connected to the I/O Module
+12V and ground terminals continues to power
the CR7 system even though the CR7 power
switch is off. Reverse polarity protection is NOT
provided on this connection so exercise
extreme care if connecting external power
supplies.
Damage will occur to the analog input channel
circuitry if voltages in excess of +16V are
applied for a sustained period.
A POTENTIALLY DANGEROUS situation can
result due to hydrogen gas build up if the CR7 is
housed in a gas tight enclosure and the internal
lead acid batteries are shorted or overcharged.
Hydrogen concentration levels may occur which
are capable of causing injury or equipment
damage if ignited.