Hello everybody,
This message started out as a question to the group last night, but I
figured out what I was doing wrong as I was writing the message. I thought
I would pass it along just in case it could help others.
While checking up on my car's charging last night, I noticed that the
relatively newly-installed DC-DC converter was making a soft "tick" noise
every 10 seconds or so. I thought that was really strange because it was
supposed to be off when the key was off and the car wasn't being driven.
I put a volt meter across its inputs and watched the voltage climb to around
100V. At that point, the converter would click on and the voltage would
quickly fall. Climb again to 100V and repeat.
At first, I was perplexed, until I opened up my high-voltage box and saw the
pre-charge resistor. I had installed the DC-DC converter positive input on
the output of the main contactor. Since the main contactor comes on with
the key, I thought it worked great to turn on the converter also. However,
I forgot about the pre-charge resistor and its job of keeping the contactor
output at pack voltage.
Bottom-line, I had caused two issues. First, the DC Converter was
continually draining off charge from the pre-charge resistor, so my battery
pack was being drained when I wasn't expecting it and stressing my
pre-charge resistor with constant current flow. Second, the pre-charge
resistor wasn't getting to do its job of keeping the controller caps charged
up so I wouldn't have a high current inrush when the contactor was
activated.
I now have a solid-state relay on order to have a separate enable switch for
the DC-DC converter off the key switch (without a pre-charge resistor!).
Until then, I have the manual disconnect off whenever I'm not driving the
car. No sense draining the pack and continuously switching the converter on
and off needlessly.
Reading through Mike Brown's "Convert It" book, he clearly goes over this.
I obviously missed that fine detail the first time!
I will obviously do the same thing for the new heater I'm getting ready to
install.
I know that many people have two contactors between the battery and the
motor controller. So far, I only have the one. I know that I'm missing an
element that could be a key safety factor if the main contactor welds
closed. I'm trying to figure out where I would put the second one. They
are big!
I hope this helps some other person with less experience avoid this mistake.
Mike
_______________________________________________
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This message started out as a question to the group last night, but I
figured out what I was doing wrong as I was writing the message. I thought
I would pass it along just in case it could help others.
While checking up on my car's charging last night, I noticed that the
relatively newly-installed DC-DC converter was making a soft "tick" noise
every 10 seconds or so. I thought that was really strange because it was
supposed to be off when the key was off and the car wasn't being driven.
I put a volt meter across its inputs and watched the voltage climb to around
100V. At that point, the converter would click on and the voltage would
quickly fall. Climb again to 100V and repeat.
At first, I was perplexed, until I opened up my high-voltage box and saw the
pre-charge resistor. I had installed the DC-DC converter positive input on
the output of the main contactor. Since the main contactor comes on with
the key, I thought it worked great to turn on the converter also. However,
I forgot about the pre-charge resistor and its job of keeping the contactor
output at pack voltage.
Bottom-line, I had caused two issues. First, the DC Converter was
continually draining off charge from the pre-charge resistor, so my battery
pack was being drained when I wasn't expecting it and stressing my
pre-charge resistor with constant current flow. Second, the pre-charge
resistor wasn't getting to do its job of keeping the controller caps charged
up so I wouldn't have a high current inrush when the contactor was
activated.
I now have a solid-state relay on order to have a separate enable switch for
the DC-DC converter off the key switch (without a pre-charge resistor!).
Until then, I have the manual disconnect off whenever I'm not driving the
car. No sense draining the pack and continuously switching the converter on
and off needlessly.
Reading through Mike Brown's "Convert It" book, he clearly goes over this.
I obviously missed that fine detail the first time!
I will obviously do the same thing for the new heater I'm getting ready to
install.
I know that many people have two contactors between the battery and the
motor controller. So far, I only have the one. I know that I'm missing an
element that could be a key safety factor if the main contactor welds
closed. I'm trying to figure out where I would put the second one. They
are big!
I hope this helps some other person with less experience avoid this mistake.
Mike
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev