# Pulse charging lead acid battries effects and side effects

I am developing a solar charger which charges lead acid batteries. I would like to clear a few of doubts on this issue.

I am using IR2110 gate driver for driving 2 n-channel MOSFETs in an half bridge configuration. Should the gate to source voltage of the high side MOSFET be pulled up to my solar panel voltage in order to force current to flow through the battery?

Is it possible I can connect the output of the H bridge (which is a high current PWM signal) directly to the batteries. Or should I use some kind of smoothing LC filter to first smoothen the PWM signal? If its the latter, any mathematical data on calculating the L and C values would be very helpful.

Edit: Posted the circuit that I planned.

simulate this circuit – Schematic created using CircuitLab

Diode D3 is for preventing the MOSFET M2 from shorting the battery to ground. Diode D2 is a flyback diode used to ground negative current from the inductor.

• I can't find the link, but pulse charging isn't actually any more effective than steady current. It's just a marketing gimmick. Just because something has a patent doesn't mean it works. May 16, 2015 at 8:47
• Hi Jodes,The reason i asked is if i can pulse charge ,i will not need an LC filter to smooth-en the PWM signals,it shouldn't cause any instability during charging. May 16, 2015 at 10:05
• Unless RF emissions are a problem, you certainly don't need the 'C1' part of that LC filter; lead-acid batteries are electrically very effective capacitors. Nov 14, 2023 at 17:14

## 3 Answers

Pulse charging a lead acid battery should follow the same technique as for regular charging. Basically, ignore the fact that it is pulsing. Each pulse must have its voltage and/or current limited in the same way for a continuous charge.

Guides on how to charge a lead acid battery are below:

So the simplest way of charging a lead acid battery is to limit the charging voltage to approximately 13.8v for a 12v battery, although this may vary depending on the manufacturer, temperature etc. Also limit the current. A charging current limit of C/10 is typical safe value for car batteries. (e.g. a 100Ah battery can usually be safely charged at 10A up to 13.8v).

However, I'm not sure why you want to use an H bridge. In fact, depending on how the H-bridge is configured, your pulses will alternate between charging and shorting the battery (half bridge), or even reversing it's polarity (H-bridge) which is definitely not what you want to do.

Why on earth are you using a half/H bridge to do this? Or pulsing at all for that matter? Can you give a circuit diagram of what you were planning? (Use the circuit diagram tool in the text editing box by clicking the tiny circuit button)

• Edited my first post with a rough schematic.Please have a look May 16, 2015 at 18:08

For clarification, the circuit diagram you posted is a switching regulator. M1 is top gate, M2 is bottom gate. I assume you have feedback so you can control the gates based on the voltage at C1.

A half H would have independent connections to the load (typically a motor) to facilitate polarity reversal. The half H configuration is shown in the IR2110 data sheet.

Switching regulators typically have LC filters on the output. A lead acid battery serves as a low pass filter for a vehicle's alternator already, so maybe it's not needed... but i think i would include it. Whether it's needed really depends on how high "solar voltage" gets.

To me it's clear in case you want to build a synchronous buck inverter with a current control to charge your battery. If you plan to do that you don't need D2 M2 is having that role and your software needs to control the dead time of M2.