# Is there a minimum for charging current for lead acid battery?

I've recently bought a 9 V, 3 W solar panel that I wanted to use to make a small project in my balcony, then I bought a 6 V, 4000 mAh sealed lead acid battery, I want the solar panel to always charge the battery through a PWM solar charger whenever possible.

I am a beginner in electronics, because I am just still young, in highschool, but electronics is my no 1 hobby and I need someone to answer my question.

My question is very simple, after dividing watt by voltage, I will get a maximum current of the solar panel which is around 300 mA, ironically I think in my area I would get just 100 mAh, but anyway I've recently read about how to charge a lead acid battery and there is a statement I read before, that a lead acid battery is charged at current of 30% of it's capacity if I applied this rule to my 4000 mAh battery I would need a 1.2 amp to charge it in (2.4 volts per cell), is this a must or any current less than 1.2 amp can charge a lead acid battery?

• 0.3C was probably a MAXIMUM recommended rate. Lower is fine. Very low it may not be able to "bulk charge" properly (see www.batteryuniversity.com advise on lead acid charging) but your I = P/4 = 3/p = 333 mA, which is a max rate of = mA/mAh = 333/4000 =~ 8% is very acceptable. [8% = 0.08C ~= C/12] Oct 14, 2019 at 6:41
• Current is mA or amps not mAh. It does not have the "h" bit. The "h" bit makes it milli ampere hours and that's a measure of battery capacity and not what current it may deliver. Oct 14, 2019 at 7:21
• @Andyaka Thanks for your notice, I fixed it. I really sometimes mix amp and amp hours Oct 14, 2019 at 12:55