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HP 66332A Output Off but still loading source
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J-R:
OK, sorry, that explains it, I have "Option 760: Output disconnect relays".  I see Keysight's official options page calls it "DC isolation and polarity reversal relay".  User manual states "Units with option 760 have isolation and polarity reversal relays connected to the output and sense terminals."
Berni:
Ah yeah that would explain it. Mine doesn't have the relay option.
rommac100:
Ah okay that makes sense that the option 760 would allow for a complete disconnect from the circuit (neither of my units have this option). I was planning on using these power supplies for charge and discharge cycling while also doing some long term no load monitoring of some 18650 cells. I assume having a relay would prevent this long term monitoring so I might just need another multimeter to do the long term voltage measurements.
alm:

--- Quote from: rommac100 on March 01, 2023, 04:23:44 pm ---Ah okay that makes sense that the option 760 would allow for a complete disconnect from the circuit (neither of my units have this option). I was planning on using these power supplies for charge and discharge cycling while also doing some long term no load monitoring of some 18650 cells.

--- End quote ---
Check the service manual for what the option entails. It would not surprise me if option 760 just entails soldering in a few relays and passives, and changing some jumpers. But I didn't check.

Be careful hooking up those cells directly to a power supply without external protection like series diodes. If the power supply loses power, or if a voltage spike trips the overvoltage crowbar, that could result in the cells destroying the power supply. The longer you have them hooked up, the higher the chance of something like a power cut. Keep in mind that these batteries can have hundreds of amps of short-circuit current in a sufficiently low impedance load. Although I believe these supplies have an internal fuse in the crowbar circuit that might mitigate this problem. But in general I prefer to use battery charges to charge cells, and use battery simulators like this to simulate a battery.
Berni:
Last time i had to cycle batteries i combined a programmable PSU and programmable electronic load to do the job. The PSU had a diode in series, so that the battery couldn't discharge back into the PSU. I did actually blow up a PSU as part of that setup, but not because of the setup, it was just a cheep chinese piece of crap PSU that didn't have the cooling to keep up (despite having a fan and running it bellow max specs) so it blew its pass transistor, resulting in a but if a hairy situation but luckily i was dealing with lead acid.. lithium would have exploded. Got the money back for that PSU from Farnell since it was literally weeks old.

Tho i don't see why this instrument couldn't do all of it. As long as you put a fuse in series with the battery and place the battery in a metal bucket, it should be fine.

If you want to do long term monitoring on cells then you need a DMM with high impedance mode since even the input resistance of a multimeter can affect the battery over a long enugh period.
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