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bdeianov:

--- Quote from: EEVblog on March 04, 2021, 12:00:15 am ---
--- Quote from: bd139 on March 03, 2021, 09:23:25 pm ---Or just stuff a diode in series.  :-//

--- End quote ---

That's what the manual tells you to do.
Unfortunately no external sense to compensate for the drop.

--- End quote ---

I was curious what the E36312A / E36313A supplies do, which do have remote sense. Turns out they have the same note in the manual. They further show the sense line connected before the diode, so they still can't compensate for the diode drop.
Berni:
Same thing is recommended for the rack mount system PSUs 6621A, 6622A,6623A, 6624A,6627A



But i have feed voltage back into one of these supplies and it behaved nicely. If you try to pull the output voltage above what it is set to it simply starts sinking current to keep it in regulation. I have even used it as a "battery simulator" on a power bank and it was perfectly happy both providing current and sinking current. The sinking ability appeared to be limited by the channels maximum rating. So if you had a 60V 1A channel it would sink up to 1A of current before the voltage goes out of regulation. All this is done in analog circuitry and works well. So yes it does sink current but it would just slowly discharge the battery.

However the manual there talks about OVP specifically. This is a feature that is off by default and you have to manually turn on using a button. I have not tested that, but i would assume it does the usual sinking up to the channel maximum, but if you shove in more current that the channel can handle then the voltage starts to rise, eventually hitting the (likely in hardware) OVP trip point. At this point it would make sense for the PSU to fire off a SCR across the output to short it out in a last ditch attempt to keep the voltage from rising too high.

Most other PSUs have an internal pre-load resistor across the output that is behind the current sense shunt. This resistor mostly being there to discharge capacitors and help the linear regulator be more stable. So as a result most PSUs do have sinking capability but only in the 10s of miliamps (depends on the voltage)
2N3055:
Problem here is specifically in crowbar circuit. PSU that are more than one quadrant, or have active down programmer have current limit and won't be damaged. Most of the PSU are specced for parallel mode, and if they are, they are designed to back fed the voltage.  Problem is only if crowbar circuit fires, or you reverse voltage, and that only if outside source (battery) can source too much current ( which decent sized SLA or LiIon or LiPO can) so there is damage.

Bottom line, we all on occasion charge batteries on those lab PSU, but they are not meant to do so...
If I do, I put big Schottky diode in series and raise voltage 0.5V. That's close enough for charging.
Or I could put in mosfet protection reverse voltage circuit  and not worry about voltage drop at all. That one could be put in a small box with cables on and you just grab charging cables and connect battery...
It's just I don't do this often enough  to be bothered to make one...
tautech:
If a lab PSU isn't safe to charge any battery it's not worth the scrap metal it's made from !  :P

At power loss it should default to output OFF unless it has an option to override this.
OVP need also be selectable and enabled as necessary where instead of blowing fuses it should trigger the output to OFF.

None is magic and are standard features in some PSU's.
Bud:
Those rack mountable HP power supplies "can" sink current but that was not meant to serve as electronic load, and their operator's manuals say that. Current sink feature was meant for programmable testing, such as evaluating Load's regulation and transient response. A program would run via GPIB, making the power supply change voltage fast. When such changes go from higher voltage to lower voltage , the power supply has to be able to sink current from charged capacitors on the Load side.
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