HP97 battery pack rebuild
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02-11-2016, 01:47 PM
Post: #10
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RE: HP97 battery pack rebuild
(02-11-2016 11:57 AM)Hans Brueggemann Wrote: i agree with you that longer charging times will get you more mileage. however, i managed to kill several of those battery packs over time by being "too generous" on charging times. so, i always keep charging below 120% of rated amp-hours. Actually 1,2 is the "official" factor for NiCd and NiMH for average charging rates (let's say 0,1...0,5 C). Since new high-quality batteries usually have somewhat more true capacity than nominally rated (+5...10% is quite common) and low charging rates around 0,1 C are quite relaxed, the manufacturers often state an 1,4x factor which leads to the ubiquitous "14 hours at 0,1 C" recommendation. Example: Although rated at 2450 mAh ("minimum capacity") Panasonic's HHR260SCP has an average capacity of 2600 mAh and the recommended standard charge is 260 mA (=0,1 C) for 16 (!) hours. This would translate to 24 h in the HP97. It's good to hear that you measured the 97's actual charging current. For a 2400 mAh battery, these 170 mA are merely 0,07 C. If you take a look at the manufacturers' data sheets you'll often find the statement that permanent trickle charge can be applied with 0,03...0,05 C without harming the battery. Some battery types (especially those designed for high loads and fast charge) even have no problems with a permanent 0,1 C charge. So I think in this case we can see things quite relaxed here. For hard facts simply consult the manufacturer's data sheet of the battery type actually used. Dieter |
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