After going through the effort to swap out the JLD-404 meter and test the new one with 3 different shunts, I finally discovered the root cause of the current measurement inaccuracy. The meter comes with the default current input setting on a 5 Amps scale. The choices are 5 amps, 1 amp or 75 mV. While being diligent to input the correct shunt value at full scale, on both meters I had left the the current input on the default setting. All I had to do was change A-Sn = 75mV. That was it!!!
Now another mystery presented itself. The old meter would always retain the recorded amp-hours, but the new meter would reset to zero every time power was turned off to the meter. I asked for my old meter back and returned the loaner/replacement. It is now installed and all is well. The current is now within 1% of the actual. A very small fudge factor in the shunt setting and it is reading spot on.
Any update on how the setup is working for you? I was thinking about going the same route but without all the electronics, just a voltage meter to tell me when to charge the pack.
ReplyDeleteCorey,
ReplyDeleteOur lithium golf cart system is still running fine. We re-charge about twice a week, typically never needing to go below 40 amp-hours, well within the safe zone (should not go below 80 amp-hours on a 100 amp-hour capacity cell). Thanks for asking.
I would not advice running a lithium pack without an amp-hour (or watt) counter. That is your gas gage, as pack voltage will not tell you the state-of-charge. You run the risk of permanently ruining individual cells that are empty before you notice a drop in the overall voltage. An inexpensive steel shunt and an amp-hour meter are well worth the cost and should be considered essential.
I never heard back from the supplier as to why the new "branded" JLD-404 meter that they sent would not remember the settings after turning off the power to it. The old one which I have back now will retain the settings for weeks.
Hope your project goes well.
Regards,
Steve
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