Re: NimH battery chargers that charge cells individually?
- From: Steve Giannoni <casagiannoni@xxxxxxxxxxxxx>
- Date: Thu, 10 May 2007 08:11:15 -0400
Circuit and a photo of homade assemby built under a high shelf in
utility room :
http://share.shutterfly.com/action/pictures?a=67b0de21b3299c0984d3&sid=0QcsWTNs5asXTg
120 V AC is fed directly to the cells charging in series, through a
full wave rectifier bridge. Current is limited by the two, 1 mF
capacitors that are switched in parallel or series by the DPDT switch,
each half position indicated by the corresponding "P" and "S". The
neon lamp is just to indicate current flow but also adds a bit more to
the total charging current. The capacitors run "cold" since they are
purely reactive. An equivalent resistor would cook along at about 10
watts. The fuse in the hot leg is very important to prevent a fire
hazard and should be as small and fast acting as possible. The cells
must be in the series configuration. The capacitors must be the non
polarized type and rated at least 200 volts. The ones available from
Radio Shack are the metal film type. The 100 ohm resistor is to
protect the switch contacts and capacitors from the potential surge
when switching from the S to the P position. The rectifier bridge
diodes must have a high peak inverse voltage rating. The ones
available from Radio Shack are 1 Amp 400 PIV. The P position charging
about 80 mA is for the first 24 hours or so, then switch to the S
position for ongoing trickle charging at about 20 mA. Since
essentially all the series voltage drop is across the capacitance and
neon lamp with it's 33K ballast resistor, the charging current will be
constant and essentially independent of the number of cells charging
in series, even if the output is shorted. The fuse and the series
battery holder are outside the photo, and power in is the line from
the lower right while the line to the battery holder is at the upper
left. The Neon ballast resistor is indicated as 22K in the circuit but
33K is more typically correct and will depend on the lamp rating. TAKE
CARE OF THE INHERENT SHOCK HAZARD OF THIS CIRCUIT ! THERE IS NO
ISOLATION FROM FULL LINE VOLTAGE. WITH THE CELLS REMOVED, THE VOLTAGE
AT THE HOLDER CONTACTS INSTANTLY BECOMES FULL 120 V RECTIFIED DC. KEEP
OUT OF THE REACH OF KIDS AND PETS, AND AWAY FROM WATER. USE THIS
CIRCUIT AT YOUR OWN RISK ! The circuit assumes 120 VAC 60 Hz and other
supplies will require adjustments in the component ratings.
On Wed, 09 May 2007 06:16:53 -0700, Daniel Prince
<neutrino1@xxxxxxxxx> wrote:
Of all the NiMh battery chargers that charge cells individually on.
the market, in your opinion, which one is the best if money is no
object?
Which one is the best value for the money?
What is the lowest cost one that does an acceptable job?
Thank you in advance for all replies.
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- NimH battery chargers that charge cells individually?
- From: Daniel Prince
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