I have a 2 cell(4.2V)/12Ah deep cycle flooded lead acid battery that i usually charge by 5V/2A smartphone charger. By using this charger it takes 200mA current for charging. Today i got my CC/CV buck converter(laptop charger as source) i set it to 4.6V/1.2A and that charged battery starts to charge at 1.2A. So how is possible that higher voltage GENERIC smartphone charger charges battery slower?
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1\$\begingroup\$ did you check how much voltage the "charger" produces when dumping current into the 4.2 volt battery? \$\endgroup\$– Andy akaMay 5, 2017 at 16:21
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\$\begingroup\$ about 4.4-4.6 V. \$\endgroup\$– RidhamMay 5, 2017 at 16:34
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\$\begingroup\$ Then you must be mistaken in your assumption about the charger taking longer. \$\endgroup\$– Andy akaMay 5, 2017 at 16:46
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\$\begingroup\$ well as i charge this battery at 100mA about 20-30 hours its reaches open circuit voltage upto 4.18v. \$\endgroup\$– RidhamMay 5, 2017 at 16:49
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1\$\begingroup\$ I'm suspecting foldback current limiting, or it could just be a poor quality USB cable. \$\endgroup\$– Jasen Слава УкраїніNov 8, 2021 at 3:27
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Edit: well, apparently this isn't the answer, according to the asker. The charger has no communications electronics in it either. Leaving it here because it is an answer to what makes chargers different, just not the right answer in this case.
In all likelihood, your smartphone charger contains active electronics designed to communicate with the smartphone and negotiate how much current can be drawn. The USB specification requires that host devices (such as your charger) output no more than 100mA unless the device on the other end requests more. Since your battery is just a dumb battery, it doesn't have the electronics to request more current, and your charger provides its default of 200mA. (few chargers actually adhere to the 100mA limit. Most go straight to 500mA, the maximum allowed in standard USB 2.0. It's odd that yours goes to 200mA, but not unbelievable.)
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\$\begingroup\$ No! charger is also dumb. it wont communicate to host devices.. it allow upto 1.87A which i check by using low resistance nichrome wire. \$\endgroup\$– RidhamMay 5, 2017 at 15:44
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\$\begingroup\$ I don't short charger, but changing resistance by nichrome wire i checked voltage drops,resistance and current. Its a ideal dumb charger. Thanks for answering. \$\endgroup\$– RidhamMay 5, 2017 at 15:46
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\$\begingroup\$ Hee hee. A smartphone with a lead-acid battery? \$\endgroup\$ Mar 19 at 15:18