Yup. 3.6 volts (lithium ion and polymer batteries like to be between 3.2 and 4.2 volts) and I recently replaced the charger board due to the charger port being damaged.
3.6 Volts isn't charged. It's not batteries "like" 4.2 Volts, it's that lithium polymer batteries under charge will show 4.2 Volts and will show between 3.7 and 3.5 Volts under use. By 3.2 Volts, the charge is on the way out.
The battery (used one or new one) is about 2 years old (they make 2 loads of batteries - 1 before the phones are released, one a few months later), so find out
why the charger board failed. That's probably where the problem is. Fix that, replace the "replaced" charger board if the problem took that one out too, then see what the battery does
after 3 full charge/discharge cycles. (It's entirely possible that you got a defective battery off the shelf, too.)
(The board that the charger port is on isn't the charger - that's a separate chip. The board that the port is on is just the board that the port [and I believe the buttons in the E4] is on.)
If you don't know the cause, you can't fix it. Just replacing parts ... any repair shop can do that. If that's all you wanted, you could have brought it into one.
Find the cause and fix it. Then replace any parts that the cause damaged.
(Mustang's idea is a good one too - there might be a short on the motherboard, preventing the battery from getting charged. "Spiking" could be a bad capacitor. If you can find the bad one, replace it. [That wold require a current setting on the multimeter, removing capacitors one by one - the ones across the rails are best to start with, unless there's one with obvious damage - and watching each one with 5 Volts applied for spiking after the current settles down [to nothing - if it's leaking, replace it]. Repair shops, except for a few good ones, don't do things like that - they just replace the motherboard, instead of a 15 cent capacitor. Replacing a SMD capacitor requires desoldering and soldering, replacing a motherboard just requires a screwdriver, which most people think they know how to use.)