Is it safe to connect a battery in series to wall via adapter?

I have an AC adapter which gives me 10 vDC from the wall (220 volts). I've measured the adapter and it outputs 10 vDC. I have a 3 volt battery. I would like to connect in series to get 13 vDC.

  1. Is this possible?
  2. Is this safe? If not, what can go wrong?
  • \$\begingroup\$ You have it backwards. Batteries in series add voltages. Batteries in parallel add capacity/current. So you will be placing 10V across the 3V battery which will not end well. Adding the battery in series should work but I wouldn't recommend it. \$\endgroup\$ – I. Wolfe Jan 9 '15 at 14:08
  • \$\begingroup\$ Edited. I understand. Thanks. \$\endgroup\$ – Pointo Senshi Jan 9 '15 at 14:11

You do NOT want to connect the battery in parallel with the wall adapter. The battery will most likely explode.

It sounds like what you are asking is if you could wire them in SERIES. I.E. 10V + 3V = 13V. You could do this for some simple experimentation as long as the current of your load is much less than the rating of the battery or the wall adapter. However in the long run this is to be discouraged and you should obtain the wall adapter that gives you the voltage that you need.

You could also consider buying or building a switch mode up converter that takes your 10V up to 13V.


You could make a set up like this, assuming the battery was rechargeable and you set the circuit up as a float charger. Connecting the battery in parallel wouldn't give you 13 volts anyhow. connecting in parallel adds current, not voltage.

  • 1
    \$\begingroup\$ You should not recommend it to be OK to parallel a 3V battery to a 10V wall adapter. \$\endgroup\$ – Michael Karas Jan 9 '15 at 14:09
  • \$\begingroup\$ If the battery is rechargeable, and you build a float charge circuit, it works okay. the float charge circuit allows the battery to supply power to the circuit while being charged, and the battery is protected from potential overcharging by the circuit.Is there any specific reason why this wouldn't work? \$\endgroup\$ – Delta1X Jan 9 '15 at 14:15
  • \$\begingroup\$ Yeah such circuit could be built to supply to a circuit that operates at the voltage of the battery. But that is far off from where the OP is trying to go to get 13V. \$\endgroup\$ – Michael Karas Jan 9 '15 at 14:24

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