Power supply interchangeability

4 posts / 0 new
Last post
Azirine
Offline
Last seen: 1 day 14 hours ago
Joined: 12/06/2021 - 22:59
Posts: 130
Power supply interchangeability

I have 2 Xtar chargers, the VP2 and SV2, which comes with power supplies with outputs 12V 1.0A and 12V 2.0A respectively. I used the 12V 2.0A power supply with the VP2 to charge 2 18650s at 1A each, and after a while they were warm to the touch (18 °C above ambient). I was alarmed and switched to the SV2 with the same 2.0A power supply, and continued to charge at 1A, and the cells cooled back down while still charging in the CC stage. What was happening when I used the VP2 with the 2.0A power supply? Did I damage my batteries?

Edited by: Azirine on 09/22/2022 - 16:47
gravelmonkey
Offline
Last seen: 12 hours 27 min ago
Joined: 08/17/2012 - 20:28
Posts: 567
Location: London, UK

If the charger is designed correctly, the current rating of the power supply shouldn’t matter.

I doubt youve damaged the cells.

VP2 review showing cells get warm.

Azirine
Offline
Last seen: 1 day 14 hours ago
Joined: 12/06/2021 - 22:59
Posts: 130

Good to know that it’s normal for the cells to get warm. With the SV2, even with 1A, the cells remained cool (only 8 °C above ambient). It’s not an accurate comparison because I’m not charging the same cells from the same voltage but still the difference is surprising.

SYZYGY
SYZYGY's picture
Offline
Last seen: 18 hours 16 min ago
Joined: 02/20/2020 - 04:47
Posts: 66
Location: usa

that amperage rating is the max current it can supply without the voltage dropping (or the supply just turning off). going higher is never a problem. going lower can be a problem if the device tries drawing more juice than the supply can give.

 

any well-designed device will have its voltage and current requirements (along with a polarity figure for barrel jacks) printed near the connector. to power it, hook up a supply with the correct voltage (and polarity) and a current rating at least as high as the device specifies.

 

so if the supply doesn't match the device:

  • supply voltage is too high: device could glitch or get permanently damaged
  • supply voltage too low: device will glitch or just not turn on (but not get damaged)
  • max current too high: no problem. the device decides what to draw
  • max current too low: device shouldn't break, but it won't work when it tries to draw too much
  • polarity reversed: device could get permanently damaged unless it has RPP