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On lead-acid batteries, there is a parameter called "maximum initial current" which is generally written on it. I have added some pictures of it at the end of the question. My confusion is how to interpret it? Is it:

  1. The battery can demand more but I should maintain constant current below that limit.

OR

  1. The battery will never draw more than that current. So, just use a power supply (of course with appropiate voltage rating) which will be able to handle that maximum current.

I think it is number 1 but I need some expert opinion.

Edit: I have an SLA charger which is rated 1A for fast charging and 0.5A for slow charging. (there is a toggle switch for these two modes). Now suppose I have a battery with max current rating 0.33A. Should I use the battery with the charger?

If number 1 is ture then I think I sould not use it but if number 2 is true, then I should be able to use it.

enter image description here enter image description here enter image description here

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You're correct, you should limit the charge current to the specified initial current, even if the battery could draw more. Above the initial current spec the battery could be damaged, or outgas dangerous amounts of flammable hydrogen gas, or it could even explode. With a high enough charge voltage you can nearly always get the battery to take more current than the recommended initial current, so it's important to have a current limiting function.

Most commercial chargers will limit the charge voltage to a fairly safe value, as during charging the battery impedance rises and prevents dangerous current [if you respect the max charge voltage], but there are lots of sub-standard cheap chargers out there.

From Battery University a great site for battery knowledge:

Lead acid batteries should be charged in three stages, which are 1 constant-current charge, 2 topping charge and [3] float charge. The constant-current charge applies the bulk of the charge and takes up roughly half of the required charge time; the topping charge continues at a lower charge current and provides saturation, and the float charge compensates for the loss caused by self-discharge. enter image description here

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  • \$\begingroup\$ So, suppose my battery specifies 2.3A max initial current. I should use any battery charger which is rated below 2.3A right (eg: 2A or 1A)? And never above that limit (eg: 5A charger)? I hope that I am able to express my confusion. Suppose in phone chargres, I can use 2A supply for a 1A phone because the phone will never draw more than 1A even if the charger power rating allows it. But it is not the same for battery charging. Am I right? \$\endgroup\$ Aug 5 '19 at 20:18
  • \$\begingroup\$ I have a SLA charger which is rated 1A for fast charging and 0.5A for slow charging. Now suppose I have a battery with max current rating 0.33A. Should I use the battery with the charger? \$\endgroup\$ Aug 5 '19 at 20:21
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    \$\begingroup\$ You're probably OK, because most lead acid chargers limit the maximum voltage to a point where it would be hard to get a dangerous current into the battery. (The internal impedance rises making it harder to push more current.) The way you get damage is by pushing higher current with a higher than max rated voltage. However, to be 100% safe you should either monitor the current or use a charger rated for less than the initial current rating of the battery. \$\endgroup\$
    – John D
    Aug 5 '19 at 20:42

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