Why can i not slow charge a lead acid battery?

Other Hardware General Electronics
15

cjdelphi:

calvingloster:

majenko:

calvingloster:
if you had to charge a battery in 3 stages like they say you must how can u know when one stage must be finished and the next stage must start? by measuring the battery voltage? but how do you do that when the battery is on charge? will you not measure the charging units voltage? or must you first unplug the battery from the charger and then measure the voltage then decide what stage it should be on?

The battery voltage varies all the time you are charging. As I mentioned earlier the power supply's voltage is variable, so the voltage at any one point in time will be the charge voltage. You can measure this at any time while charging quite happily.

ok so for example if i have a flat battery, it measures 10volts and i put a 14v charger on this battery and try and measure the batteries voltage with the charger on i will not get 10volts. so how can you know what the batteries voltage is while it is on charge??

2 ways.

  1. Supply 14.2v, as the battery nears 14.2v the current significantly drops and just floats, but this is constant voltage or cv, 14.2v.

  2. Supply say 19v dc, regulate it for cv, then the current draw will be in the amps region, now we limit the current to say 500ma via circuitry or a simple resistor. This then leaves you with a problem as you need to stop the charge, check the battery voltage, the enable charging again.... setting it to 14.2v and walking away is as easy as it gets.

Why can I not just limit the voltage to 14.2volts and the current to a 20th of the battery capacity right from the beginning? Then I don't have to change a thing? For the bulk charge it will charge at 300mA at 14.2volts and the topping charge will charge at 14.2volts at 300mA? Why can this not be done?

For the bulk charge you supply max volts and max amps, but why can you not do a slow bulk charge? Supply a voltage and a current that is required for the topping charge. This is obviously much lower and might cause the bulk charge to take longer but it's more convenient cause you don't have to change anything? Is this not possible?