PP-7286/U Battery Charger

© Brooke Clarke 2005

PP-7286/U Battery Charger Front
PP-7286/U Battery Charger Rear
PP-7286 Charging 5590BA


If you were to take a quick look at this charger you might think that it was a boat anchor.  Lifting it's 35 pounds would tend to confirm that idea, BUT you would be wrong.  A closer look at the front panel shows a LED type digital readout, thumb wheel type switches and at the back you can see the door for the memory keep alive battery (standard 9 Volt type) and these items let you know that this five station charger is filled with digital electronics.

This charger was designed to charge the following Ni-Cad batteries: BB-505, BB-507, BB-516, BB-557, BB-590, BB-655, BB-699/PAQ-1, BB-704 and MC-1605 batteries using the fixed current for a defined time method.  It was designed to charge 6, 12, 24 or 28 Volt sealed Ni-Cad batteries, but could be used to charge any battery that can be charged using a current source, like Ni-MH, but care is needed to avoid overcharge or overheating.

The suggested settings for the BB-557 used on the TMQ-34 weather station are 100 ma for 6 hours, although the battery is marked for charging at 200 ma for 6 to 7 hours (28.8 Watt Hours). The BB-557/U is rated for 0.95 AH and has 20 each 1.2 volt cells or 22.8 Watt Hours capacity.  So the battery has about 80 % efficiency.  A C/10 current would be 100 ma and that's what's in the PP-7286 manual.

The BB-590 recomended charge is 360 ma for 6 hours (52 Watt Hours). The BB-590 is rated 1.5 Amp Hours and contains 20 Ni-Cad cells for a capacity of 36 Watt Hours.  The efficiency is about 70 %.  The battery label says to charge at 360 ma for 6 hours.  A C/10 current would be 150 ma, so they are using more like a C/4 current.

The sliding contact battery holders on the front panel are for the BB-516/U or a similar battery.  There also banana jacks for each of the 5 channels supporting any battery that can be wired to them and the optional battery tray designed for one of the above batteries.


3 May 2005 - My first attempt at charging was to connect a 5590BA using a plug that connects the two halves in series.  Set to the 700 ma range and fine adjusted to 230 ma (i.e. C/10 for the Powerizer 2.3 AH Ni-MH AA cells installed in the 5590BA.  Set the timer for 16 hours, and am now waiting.  The timer will turn off the charge sometime tonight when I'm asleep.  So far the 5590BA case is at room temp (after many hours).  Note that in a perfect world putting in C/10 for 10 hours should charge a battery fully, but because of losses the recommended charge time is 16 hours.

The run time was 8.5 hours, not the 8.8 hours expected.  Not sure why.  I think more time needed in the charger.  The starting terminal voltge at 100 ma load was about 29.3 for the 22 cells, but after the Propel charge the terminal voltage was over 30.

Starting with a 5590BA and a 20 Sub C (SC) cell pack of 3.3 AH Ni-MH batteries after 5 hours at 300 ma the 5590BA is at 103 deg F.  The pack was fully charged from a couple of charge cycles in the Propel BB-590 charger prior to being put on the PP-7286.   The idea here is to see if a C/10 charge will overheat a battery that's already charged, and it appears that it's OK. Will now test for run time.

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