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Fungus:

--- Quote from: nctnico on March 04, 2021, 10:44:13 am ---
--- Quote from: tautech on March 04, 2021, 07:34:29 am ---If a lab PSU isn't safe to charge any battery it's not worth the scrap metal it's made from !  :P

--- End quote ---
Nonsense. For charging batteries you use a battery charger which is suitable for the chemistry. A lab PSU is the wrong tool for battery charging so don't be surprised it is not 100% suitable for that purpose. The function of overvoltage protection / crow bar is to protect your potentially expensive DUT (a prototype SoC board can easely cost US $1000) against operator error or defects inside the PSU.

--- End quote ---

Battery protection modules are about $0.15 on Aliexpress: https://www.aliexpress.com/wholesale?SearchText=TP4056


SilverSolder:

--- Quote from: nctnico on March 04, 2021, 10:44:13 am ---[...] A lab PSU is the wrong tool for battery charging [...]

--- End quote ---

Is that totally fair?  -  a lab PSU is a general purpose source of power that shouldn't really care what you use it for (within reason!).  A battery charger is an application specific device.  So, I would accept that the charger is "better"...  but surely I should feel OK about connecting anything I like to my lab power supply that isn't directly insane? 

For example, the other day I was measuring the internal resistance of a bunch of NiMH cells.   My battery charger was not able to do this...  so I used my ancient lab power supply in constant current mode and measured the difference in voltage drop between two currents, differing by 200mA.   So, connecting a battery to the supply is a possible use case even if you are not charging it...   

Also, consider the use case of charging a supercap, or even a regular capacitor (massive capacitor bank in an audio amplifier, for example) and subsequently decide to lower the voltage...

Overall, it seems preferable to me that a lab supply is able to deal with these kinds of real world scenarios without the risk of self destruction.  Granted, a crowbar is always going to be an issue and probably should not be used without a fuse...  but that could also be baked in.



bdunham7:

--- Quote from: nctnico on March 04, 2021, 10:44:13 am ---Nonsense. For charging batteries you use a battery charger which is suitable for the chemistry. A lab PSU is the wrong tool for battery charging so don't be surprised it is not 100% suitable for that purpose. The function of overvoltage protection / crow bar is to protect your potentially expensive DUT (a prototype SoC board can easely cost US $1000) against operator error or defects inside the PSU.

--- End quote ---

The manual for mine specifically lists battery charging as a function and gives details on how to do it.  A 'correct' charger is optimal for routine battery charging, but people do test/repair/characterize/analyze/etc battery systems just like anything else and there are many times I'm interested in more than just charging the battery.  Other times I may need to charge an internal or odd battery in order to test something and the 'correct' charger is broken or unavailable.  It's an everyday use for me and I can't think of anything that would work better.

 It doesn't have a separate OVP, but designing an OVP should be straightforward and properly implemented it shouldn't result in damage if you connect a battery.  In non-battery situations where the OVP is there to protect your SoC from programming errors or internal control circuit failures, triggering the OVP should result in a current-limited internal short or, if the current-limiting part fails, a blown internal fuse.  Triggering the OVP while a battery is connected should result in a blown fuse.  Whether or not the PSU is capable of sinking current (mine does not) shouldn't matter much to a good OVP design.  If you don't need or want battery charging capability then it is fine to buy a PSU that 'fails' the battery test, but there isn't any inherent conflict that I can see between the two goals of protecting your SoC and not going up in flames if someone connects a battery.
nctnico:
Now try to figure out how HP never came up with the idea of having a fuse in series with the output of a PSU ^-^
exe:

--- Quote from: bd139 on March 03, 2021, 07:20:26 pm ---Disagree entirely. Crowbar is important when the following equation is true:

cost_of_load > cost_of_power_supply

A year or so ago I had what i consider to be a fairly decent quality supply (HP) blow the reference zener. This caused the output to bang itself at the collector supply voltage. You should plan for such failures.

--- End quote ---

How does a crowbar work? I assume the expensive load is also sensitive to overvoltages. In this case the crowbar should engage very fast and at voltages not so much above the set voltage. If reference circuit doesn't work,  how does the crowbar know when to trip?

If crowbar set to trip at, say, 30V, then it's already late, imho.
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