NIMH charge control [RE-wrenches]

[Steve Bell]

----- Original Message -----
From: "David Palumbo, Independent Power & Light" <ipl at sover.net>
To: "Wrenches" <RE-wrenches at topica.com>
Sent: Monday, April 02, 2001 11:56 AM
Subject: NIMH charge control [RE-wrenches]


> The following is a question posed to my web site that I do not have an
> answer. Anyone on the list who can help?
>
> "I have a siemens st-5 (5w, 12vdc) panel, and a 12vdc, 3.4 Ah NIMH battery
> pack. Do I need to be concerned with a charge controller of any type? as I
> keep adding panels, and batteries, when would a charge controller be
needed,
> and what type is optimal for NIMH cells?"
>
> Dave Palumbo

Hi Dave,

The ST-5 has a rated output @mpp of 15.6 VDC and 0.32 amps.  I do not know
how high a voltage is required to full recharge a NIMH battery, but charging
a 3.4 AH battery with a 0.32 amp charging source without a charge controller
seem like you are asking for problems. Admittedly, in warmer weather the
module voltage may well be reduced from 15.6 VDC to a voltage below the
maximum charge voltage of the battery, but what happens if the weather is
clear and cold?

Siemens claims the ST-5 losses about 0.4% voltage per degree C.  Maybe
Richard Perez and friends know what the correct charging voltage is for NIMH
batteries.

Sincerely,
Steve Bell
SunWize Technologies
sebpv at stelle.net


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