My car wouldn't start, so I bought a jump starter. Basically it's a huge 12v rechargeable battery. It comes with a 12v 0.5a power supply for charging, which gets pretty warm.

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I trust this power supply as much as ehh... Well not a lot. The battery has to charge for over 48 hours, so I'd prefer to leave it charging overnight. I don't dare to with this PSU.

I've got a couple laptop power supplies, 12v, up to 2.5A. barrel jack and polarity are identical. For the usual device I'd just grab one of those, but as this is a battery the following question came to mind.

Is it safe to use a higher amp PSU on a device with a battery? Or could the charging rate of the battery be dictated by the PSU, and the battery overheat with a stronger PSU?

I do not know what type of battery is in this device, and have no intention of disassembling it to find out. It states 250A peak output, 7Ah capacity in a package of about 2.5 liters (guesstimate), but there's no labels about the type of battery.

Afaik not a duplicate as the following question doesn't cover batteries: Choosing power supply, how to get the voltage and current ratings?

  • 2
    \$\begingroup\$ I've got a couple laptop chargers ... they are power supplies... the battery chargers are built into the laptops \$\endgroup\$
    – jsotola
    Feb 9 at 17:47
  • \$\begingroup\$ This question will be closed (noy by me) if MUCH MORE information is not provided. Please provide details of the device that you are trying to charge. Did it come with that power supply. What does it weigh (may reveal battery type). || Power supply maker probably here but that does not help without device details. \$\endgroup\$
    – Russell McMahon
    Feb 10 at 6:04
  • \$\begingroup\$ @RussellMcMahon do you see a way to turn this question into one that would serve more people? \$\endgroup\$ Feb 10 at 6:30
  • \$\begingroup\$ @DaniëlvandenBerg At the moment it does not even serve you :-(. We do not know the brand or model or spec plate ratings of your jump starter. We don't know the battery technology - and while the weight and dimensions may give a clue we only have a guesstimate of volume. Would it accommodate a 7Ah 12V lead acid battery? || You could have advised brans and model and posted a picture. One the kneecappers arrive they tend to close such questions rapidly if you do not improve them. \$\endgroup\$
    – Russell McMahon
    Feb 10 at 9:17

1 Answer 1


Is it safe to use a higher amp PSU on a device with a battery?

With or without a battery in the downstream device, a more capable PSU should not be a problem.

Or could the charging rate of the battery be dictated by the PSU,

Unlikely. It will be controlled by the battery charger electronics before the battery, after the PSU. It might be limited by a puny PSU. If the charger has been designed to operate from a 500 mA PSU, you would not expect it to draw more than 500 mA, so any PSU capable of delivering at least that will be OK.

and the battery overheat with a stronger PSU?

Not if the charger is controlling the current, which you can be 99.something% confident that it is.


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