BLM1 Battery Tests - Clone Wars Episode II

Started Mar 29, 2005 | Discussions thread
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Jim Attfield Veteran Member • Posts: 3,930
BLM1 Battery Tests - Clone Wars Episode II

Following on from my test of the PS-BLM1 clone (which you can find in this thread http://forums.dpreview.com/forums/read.asp?forum=1022&message=12803121 ) I have just completed testing the second clone which I refer to as the 'WT-BLM1', currently sold by SterlingTek.com (amongst others) on ebaY.

Disclaimer: findings for personal use only - if your E-1 blows up you'll have to find someone else to blame

Results of battery test on SterlingTek.com WT-BLM1 clone as follows:

Some comments:

The circuitry is not at the at battery ends, but is on a PCB sandwiched between the cells and the bottom of the pack. This is a good location for the temperature controlled charge gut-off. Compared to the PS-BLM-1 the circuit board is very flimsy, as is the whole case assembly. The cell welds are fewer and poorer, the metal straps thinner and narrower.

There is no indication of the manufacturer of the actual cells however they are recent and clearly marked as 1300mAh, I am astonished that this battery can be marked as a 1560mAh item, and to sell it as a 1700mAh item is just laughable, not to mention deceitful.

The control board incorporates an SE666 battery voltage monitor IC as in the PS-BLM1 which is supposed to cut the pack off completely at about 5.6 volts thus protecting the cells from over-discharge - mine didn't!

The voltage monitor controls what I believe to be a MOSFET power switch to cut off the cells to prevent over-discharge. On this pack, this failed completely, the voltage oscillating between 5.4 and 4.8 volts for a few seconds then continuing to discharge until manually cut off by me at 3 volts.

There is no polyfuse, or any other type I can identify, therefore no protection at all against short circuits and potential venting or explosion.

Charge control is via an ordinary 10K resistor rather than a proper thermistor.

The capacity test shows just over 1200mAh. I should point out that I discharge at around 0.15C instead of 0.1C (i.e. 180mA or so rather than 130mA) for an accelerated time curve. Manufacturers capacities are usually stated at 0.1C discharge rate so I have no problem believing this would achieve the cell's rated 1300mAh but to suggest that these are 1700mAh (or even 1560mAh) is just a joke. The curve covers around 405 minutes.

In summary, this is one to avoid at all costs. Construction is poor, charge control is poor, protection is non-existent and over-discharge protection is questionable (failed on my sample). Get the PS-BLM1 instead, it lacks a few mAh capacity in comparison but more than makes up for it in other areas.

Jim

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