Very cool, Russell. Thanks! -Pete On Aug 21, 2013, at 2:28 AM, RussellMc wrote: > Aim: Know what's out there. >=20 > Short: You don't buy no ugly truck / beautiful battery. >=20 > Owls are not what they seem. Eneloops may not be either. >=20 > Longer: >=20 > Numerous sellers on our top NZ national auction site offer "Sanyo Eneloop= " > AA rechargeable batteries. My general experience with AA rechargeable > batteries lead me to expect that the chance of getting genuine batteries > from this source would be uncerian and may be low or zero. >=20 > I was accordingly delighted to find a local retailer selling of 'all thin= gs > computer related' genuine [tm] Aa Eneloop batteries of the latest version > at a price slightly below the lowest price offered on the local auction > site. >=20 > This was not 'an offer too good to be true' as the reseller has massive > buying power, an all Asian staff and AFAUK Asian owners so probably very > good access to low cost sources. It was however an offer to be looked at > sideways - somewhat suspect. >=20 > I bought some batteries. > Sanyo HR-3UTGB - the lates AA Eneloops. 2000 mAh nominal. >=3D 1900 > mAhguaranteed. 1800 full discharge cycles. 70% charge retention at 5 > years (I > think the claim is). > Usefully - a significantly higher discharge voltage at a given load and > state of charge compared to typical AA NimH. > What's not to like. >=20 > I weighed the cells. > All were in the 24.5 - 25 gram range. > I Mickey-Mouse recalibrated the two separate digital scales I was using - > one with 0.01g resolution. > Sanyo says "about 27 grams. Well - maybe there has been process improveme= nt > since they were 1st produced and they has managed to improve capacity and > reduce mass accordingly. >=20 > Sanyo provide a nice set of discharge curves - 400 mA 2000 mA and 4000 > mAdischarge currents after charge at 2A to -10 > mV delta-V and with 1 hour rest. > \ > I charged the cells fully. Hmmm - more top up needed than I'd have expect= ed > for LSDs of this lifetime, but maybe the initial dropoff is faster at fir= st. > This bending over backwards was getting uncomfortable. >=20 > I did a series of discharge charge cycles and semi-randomly sampled cell > voltages along the way as I walked past. Charge at 1A or 2A, discharge at > 1A 2A and 400 mA . I settled fown to 400 mA discharge with varying charge > rates. I'd expect higher capacity slightly when charge current is lower, > but may be they don't work that way. >=20 > Initial capacity was below minimum guaranteed. > Maybe they take a few cycles to come up to capacity, as happens. > I did a rest and retop on some cycles to give them a 2nd chance. Still lo= w. >=20 > I'm still not a vast number of cycles in. but std NimH will have settled > down by now. Capacities in a 1900 mAh minimum battery are 1847, 1868, 185= 3, > 1845 mAh. >=20 > BUT the icing on the cake - or the missing icing, was the discharge curve= .. >=20 > The attached diagram shows Sanyo's curves at 400/2000/4000 mA discharge a= nd > the red dots are what I see at 40 mA discharge over various cycles. > An undergraduate (and most other people) would have a fit of joy if they > could ever get their red curce and red dots to match up as these do. > The problem is, the blue curve is the one that the red dots SHOULD fit. > Very naughty. This is a typical enough NimH discharge curve. > An Eneloop would need to be loaded 5 times more heavily to get down to > these voltages. >=20 > Might I be wrong? > Of course. >=20 > Am I wrong. > Very very unlikely >=20 > I'll be doing some more definitive tests. If results do not miraculously > change I'll be talking to the reseller, to start. > I anticipate a fraught series of discussions. >=20 >=20 > Russell >=20 >=20 >=20 > See attached "DS Battery Sanyo Eneloop HR-3UTGB AA 1900-2000 mAh discharg= e > curves - with some plotted points at 1A & 2A charge and 400 mA > discharge_w496_J60f.jpg" > Please excuse quality loss due to compression. > Please excuse any other lack of quality ... :-). > --=20 > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .