Archive for August 18th, 2009

NiMH AA Pack Discharge Test: Tenergy RTU 2.3 Ah

Here’s a quartet of discharge tests for a new set of Tenergy Ready-to-Use cells. It’s the same one that produced the green and red traces in that post. It looks as though it still has a weak cell, but it’s not too far off of the others.

Tenergy RTU Pack A Tests - Aug 2009

Tenergy RTU Pack A Tests - Aug 2009

The lower black trace is after sitting around for a few days, the others are hot off a 4C charger. I think the black trace is more representative of the long-term voltage.

The two middle traces are essentially identical: same charging method, same discharging method.

The blue trace is at 100 mA (C/23); the others are at 500 mA (C/4.6). The cells don’t produce much more energy at the lower rate and, at 1.8 Ah, are still well below their 2.3 Ah rating.

The difference in voltages between the green and blue traces most likely has more to do with the relatively skinny wires and crappy spring-loaded stainless-steel battery connections. The current varies by 400 mA and a mere 0.5 Ω between the battery and the voltage measurement would account for the entire difference.