# How to attain a topping charge for a lead-acid battery?

Charging a lead-acid battery involves three stages: CC, CV, and Float. I have a charge controller which charges my battery at CC to the float voltage. I would like to add a device that would charge it via CV to full charge. (See Lead Acid Battery Charger Design Factors for description of stages.)

For example, I could attach something that would charge it, keeping it at 14.6V until the current goes down to .1A, and turn off. When this device would turn off, the charge controller would kick in, and keep it at 13.7V Float stage.

However, I cannot find a device that would do that:

1) Charge controllers that have a "Absorbtion" 14.6V stage typically have it timed,
say for 10 minutes, and then turn off regardless of the current.
2) Charge controllers that I can program to rise to 14.6V indefinitely, have no way
to tell me when their current goes low enough (other than through an LCD display).
2a) I can attach a timer to turn off such a controller after giving it enough time to
reach .1A current; however, since my system if powered by solar panels, it might
not reach .1A within that time frame on a cloudy day.
3) I can use a CC / CV power module to output 14.6V; however, that will not measure
the voltage of the battery, nor determine when the battery is fully charged.
4) I have bought several commercial chargers, such as ElProg Pulsar, capable of doing
such a charging; however, all of them require at least pushing a START button to
initiate the charge.


I have consulted with my dad, who's an electrician; however, all options have gave are either very power-consuming (e.g. involving PLC), or are not available at 12V.

I am open to buying a commercial product that would do this, if it is too complicated to make by myself. Please give some advice.

• I found SOLAR BOOST™ 3000i charger, which is capable of doing what I need if I also buy a IPN-ProRemote display, for a total of around \$350 / 30A. Hopefully I can find something cheaper than this... – Alex Jun 22 '15 at 2:34
• Have you found something cheaper since June? This should be "easy enough" if still required. – Russell McMahon Dec 29 '15 at 1:27
• Nope, haven't found anything. While I do not need it at the present moment-- if you can answer, I think it would help for everyone else, or even for me later on. – Alex Dec 29 '15 at 20:25