Buck boost vs pwm

I really appreciate your desire to save money. This is indeed an economical module and will work, to a point.

But this is not a battery charger. It will shorten battery life and ruining your cost savings. A quality lead-acid battery charger has multiple states, so it knows when to charge fast, when to top off, and when to leave the battery alone.

Conventional wisdom (urban legend?) was that you put a constant 14.5V on a lead-acid battery and it takes care of itself. That was the thinking in the 1940s, but is not your best strategy for battery life. The best approach and best chargers have three different stages with different voltages. See:


When you compare the cost of electronics to the cost of batteries, virtually always, it makes sense to spend more on electronics to squeeze more life out of batteries.

I thought the stickies here learn us that charging with ONE charge setpoint only is the most effective way of charging lead acid or lithium , if you plan to discharge your battery on a daily basis, even if you have an advanced quality MPPT charger you set bulk=absorb=float.

I think I have made a mistake and copy/paste a stepup above. Here is a buck-boost

Here is another one

The buck or a buck-boost is only one component to a battery management system.
A much more complex feedback circuit is (among other things) is needed to get the
functions needed. The other problem I noted with these low price converters, is a
lack of higher voltage or power capability. good luck, Bruce Roe

This varys depending on your batteries, usage and PV. If you have a balanced system, you can use a 3 stage charge. If you are short on PV, you need to use the max smoke (bulk=Abs=float) method.

Thanks for your answers Bruce & Mike.

Without any feedback circuit, will the use of such a buck-boost converter as chargecontroller with one voltage setpoint, benefit the charging proses comparing to the use of a simple PWM chargecontroller set to bulk=absorb=float , using 18v-21v panel and charging 12v lead acid.

What wasn't mentioned is that panels are current sources. Buck converters try to control the output voltage. This means if the buck converter tries to draw more than the panel can supply, panel voltage goes into a death spiral. Buck boost converters are even worse at that. I do use modified buck converters that hold the panel voltage constant and feed the output into a cheap $4 PWM. A cheap $10 solution to use al ow cost high voltage grid tie panel on a 12V battery at near the performance of a MPPT.