charge voltage?

Discussion in 'General Electronics Chat' started by grehe, Apr 5, 2013.

  1. grehe

    Thread Starter New Member

    Dec 3, 2012
    Hi, I have a cheapo car battery charger that reads 16.5v. But when hooked up to the battery, it charges upto 13.2v max.

    The articles on say float charge for lead-acid batteries should be around 13.2v charge voltage. What does charge voltage mean?

    Basically, I want to know if I should keep the battery at 13.2v or should I lower the charger to 13.2v (using diodes) before I hook it up to the battery. Which is the correct way to measure this?


    PS. I got that "new thread error msg" please change title to: "Correct charge voltage measurement?" or whatever you think is more suitable.
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    The 'cheapo' battery charger has a cheapo output. Without a load(a battery) connected the voltage rises to a higher level than it is capable of putting out when doing actual charging work. The battery never sees the 16 volts you are measuring, it becomes a lower voltage the instant you connect the load to the charger.
  3. JohnInTX


    Jun 26, 2012
    For a standard car battery, the charging voltage, measured after the battery is fully charged, should run at about 13.8 Volts when its on the charger. That's what the charging voltage in a typical car is set to and is safe for a continuous charge (like you have when the car is running).

    For out of the car smart chargers, the voltage gets higher to complete the charge then shuts off to keep the cells from out gassing and eventually running dry.

    Agreed. It sounds like the charge regulation is marginal at best. OK for trickling up the battery but not a real long term solution.
    Last edited: Apr 5, 2013
  4. grehe

    Thread Starter New Member

    Dec 3, 2012
    Thanks for the replies, I was confused and thought the 13.2v was in reference to open circuit voltage of the charger. Now I know better.

    I agree, the charger sux. Once I understand more about batteries, I'll try and make my own. I searched and seems like this forum already have a few threads about making one.