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I have a power bank which accepts 12V-24V as input for charging the battery. (It aslo supports 12V-24V outputs. But this is not related to the question.)

Assume that I will charge the power bank only when it's off.

If I use the 12V power supply to charge the power bank's battery, will this cause any bad effects?

All I knew is 24V power supply charging will be faster than 12V power supply. But when I don't care about the charging speed. Does it matter?

Thanks a lot.

Edited:

The user guide says higher voltage will result in a faster charging. It also recommends 14V+ charger because of the charging speed. But I don't care of the speed. Right now, I only have 12V power supply and don't plan to buy a new one if unnecessary.

One more information: The user guide does not have this notice, but I found this notice in the selling description. It says if the charging input voltage is less than 12.8V, the battery might never be fully charged. If this is the case, I guess I am better buy a 14V+ power supply.


Added RMc: It is likely that the following applies.

  • The powerbank uses 3S LiIon batteries

  • The internal converter when charging the batteries is a buck converter

  • There is a maximum upper input current limit.

  • The output converter acts as a boost converter or linear or perhaps buck boost in some cases.

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  • \$\begingroup\$ Shouldn't have any effect ... even on charging speed if well designed. \$\endgroup\$
    – user16324
    Sep 22, 2020 at 14:46
  • \$\begingroup\$ @BrianDrummond got it. I read its user guide and it says higher voltage will result in a faster charging. It aslo recommends 14V+ charger because of the charging speed. But I don't care of the speed. Right now, I only have 12V power supply and don't plan to buy a new one if unnecessary. Thank you very much for your quick reply. I think you can make it as an answer so I can accpet it. \$\endgroup\$
    – sgon00
    Sep 22, 2020 at 14:49
  • \$\begingroup\$ The charger will control the charge rate; what type of battery and charger are you using? \$\endgroup\$
    – mbedded
    Sep 22, 2020 at 14:52
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    \$\begingroup\$ Questions on the usage of products aren't really on topic here, because there's no way to tell how they work inside. From the revised minimum voltage input it sounds like this has no voltage booster. But beyond that we have no way to know how well the charging circuit is designed, or if it was designed to optimize charging speed or cell life; one might guess the former, but this site is intended for things which can be determined based on knowable facts, not guesses. \$\endgroup\$ Sep 22, 2020 at 15:09
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    \$\begingroup\$ It's an OK question - just needs more details to make it understandable. \$\endgroup\$
    – Russell McMahon
    Sep 22, 2020 at 23:57

1 Answer 1

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Summary: It is likely that -

  • Using a 12V supply will very substantially undercharge your internal battery.
    This will lower the capacity per charge but increase the lifetime capacity and cycle life of the battery.

  • Use of a 14.8V or higher supply as recommended by the manufacturer will allow full capacity charging.


It is likely that the following applies. This is 'professional guestimate' but has a good chance of being correct or correct-enough.

  • The powerbank uses 3S LiIon batteries

  • The internal converter when charging the batteries is a buck converter

  • There is a maximum upper input current limit.

The specified 14.8 V recommended minimum Vin can be explained by the fact that each internal cell requires 4.2V to charge fully.
A competent charger would allow lowering OR raising of Vin to suit the battery (buck-boost) but the easier / cheaper solution is reduction only (buck).

If the charger can not boost voltage then Vin must be >= 3 x 4.2V + a headroom allowance. 3 x 4.2 = 12.8V.
They have allowed themselves 2V "headroom".

The statement that a higher Vin allows a greater charge rate can be explained by their being some max Iin specification. Power in max = Vin x Iin_max. More Vin = more power.
The boost converter will transform this to 19 20 24V as required.
A linear regulator or buck converter will step it down when Vbattery is > Vout.

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