EVDL Administrator via EV wrote:
I agree that a hex crimper is better, and I recommend one if you're pulling
currents upwards of 600+ amps. However, I've used a hammer crimper for
years with currents <= 400a, and have never yet had a problem.
I think the trick is to use a heavy enough hammer - I use a small sledge -
and don't be shy about it.
The main problem with cheap crimpers is that they don't control the
pressure -- *YOU* do! If you don't apply enough pressure, the crimp may
look OK, but it's no good!
To make a good crimp requires enough pressure to cold-weld the metals
together. If you cut apart the crimp, you'll find that the wires have
welded to each other. The fancy crimpers have some means to guarantee
that you produce enough pressure to do this.
If you're going to use a hammer crimper, you need to TEST each crimp
yourself. This can be done with a commercial or home-brew milli-ohmmeter
that can read down to 0.001 ohm or less.
The home-brew method is to run a high known current through the
connection, and measure the voltage drop across it. For example, use
your battery charger to deliver (say) 10 amps to a battery through your
"test" crimp connection. Use your digital multimeter to measure the
voltage drop across that connection. Then use Ohm's law (R = V/I) to
tell you the resistance.
For example, you measure a 0.1v drop at 10 amps = 0.01 ohms (a bad
crimp)! That connection would produce I^2R = 1.6 KW of heat at 400 amps!
A good crimp will be more like 0.0001 ohms. That produces a 0.001v (100
millivolt) drop at 10 amps, and only I^2R = 16 watts of heat at 400 amps.
--
Imagination is your preview of life’s coming attractions. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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