Using boost and buck modules together

[Adhith]

hello everyone..
I'm planning to make a batterypack of 4S2P configuration along with a BMS.and I want it to be charged using a 12V DC adapter. I also understand that the battery should be charged first in  CC mode and then CV mode. Since i use a 12V charger I'm suppose charge with 4.2 X 4 = 16.8 V with the help of a boost module. Unfortunately I can't find a CC, CV boost module instead could only find a CC, CV buck module. so I'm planning to first use a boost module with only CV mode to get the 16.8V or higher and then fed as the input for the CC, CV buck module to finally use it as the charging source for the batteries. MY question is that would this arrangement works or not??

[adras]

How about one of these?

https://www.aliexpress.com/item/100W-Automatic-Boost-Buck-Converter-CC-CV-5-30V-To-1-25-30V-8A-5V-12V/32709807663.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10344_10342_10343_10340_10341_10193_10194_10304_10307_10060_10302_10155_10154_10056_10055_10054_10059_10534_10533_10532_100031_10099_10338_10339_10103_10102_10052_10053_10107_10050_10142_10051_10320_10321_10322_10084_10083_10080_10082_10081_10177_10110_10111_10112_10113_10114_10180_10312_10313_10314_10184_10319_10078_10079_10073_10186-10050,searchweb201603_14,ppcSwitch_5&btsid=162eeccf-d7fc-4f2b-99aa-3c426959fb20&algo_expid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99-1&algo_pvid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99

https://www.aliexpress.com/item/10A-DC-DC-Boost-Converter-CC-CV-10-32V-Step-up-to-10-60v-12v-24v/32737645216.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10344_10342_10343_10340_10341_10193_10194_10304_10307_10060_10302_10155_10154_10056_10055_10054_10059_10534_10533_10532_100031_10099_10338_10339_10103_10102_10052_10053_10107_10050_10142_10051_10320_10321_10322_10084_10083_10080_10082_10081_10177_10110_10111_10112_10113_10114_10180_10312_10313_10314_10184_10319_10078_10079_10073_10186,searchweb201603_14,ppcSwitch_5&btsid=162eeccf-d7fc-4f2b-99aa-3c426959fb20&algo_expid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99-0&algo_pvid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99

[Adhith]

How about one of these?

https://www.aliexpress.com/item/100W-Automatic-Boost-Buck-Converter-CC-CV-5-30V-To-1-25-30V-8A-5V-12V/32709807663.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10344_10342_10343_10340_10341_10193_10194_10304_10307_10060_10302_10155_10154_10056_10055_10054_10059_10534_10533_10532_100031_10099_10338_10339_10103_10102_10052_10053_10107_10050_10142_10051_10320_10321_10322_10084_10083_10080_10082_10081_10177_10110_10111_10112_10113_10114_10180_10312_10313_10314_10184_10319_10078_10079_10073_10186-10050,searchweb201603_14,ppcSwitch_5&btsid=162eeccf-d7fc-4f2b-99aa-3c426959fb20&algo_expid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99-1&algo_pvid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99

https://www.aliexpress.com/item/10A-DC-DC-Boost-Converter-CC-CV-10-32V-Step-up-to-10-60v-12v-24v/32737645216.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10068_10344_10342_10343_10340_10341_10193_10194_10304_10307_10060_10302_10155_10154_10056_10055_10054_10059_10534_10533_10532_100031_10099_10338_10339_10103_10102_10052_10053_10107_10050_10142_10051_10320_10321_10322_10084_10083_10080_10082_10081_10177_10110_10111_10112_10113_10114_10180_10312_10313_10314_10184_10319_10078_10079_10073_10186,searchweb201603_14,ppcSwitch_5&btsid=162eeccf-d7fc-4f2b-99aa-3c426959fb20&algo_expid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99-0&algo_pvid=cbc722fd-66fc-4b06-a1c0-6c0a5a002e99

Thank you very much for your suggestion, but actually I'm looking for a smaller module that could be fitted inside my project. Could you have any other resources for a much smaller module??

[adras]

I've never seen anything else. I think the size of those modules comes from the heatsinks. And I think those are mandatory when dealing with such high currents. Does somebody else know something?

Edit You shouldn't use one of these modules to charge your battery pack. At least not alone, you need a balancer. As I said in your other topic, cells connected in serial need to be balance charged.

[Adhith]

I've never seen anything else. I think the size of those modules comes from the heatsinks. And I think those are mandatory when dealing with such high currents. Does somebody else know something?

Edit You shouldn't use one of these modules to charge your battery pack. At least not alone, you need a balancer. As I said in your other topic, cells connected in serial need to be balance charged.

yes I'm aware of the fact of balancing and I'm using a BMS with a balance option. I think the heat sink makes its an appropriate one for more than 5A, but my project would hardly consumes arround 4A and i think this module is little over rated for my project. I have both boost (with CV mode) and a buck (with CC & CV mode) with me right now so thought of using them together but I'm still doubting whether it works or not

[adras]

Which BMS are you using?

Try the search terms "buck boost cv cc" on ebay, aliexpress, those are the ones I used

[Adhith]

Which BMS are you using?

Try the search terms "buck boost cv cc" on ebay, aliexpress, those are the ones I used

I have attached a pic of the BMS that I'm using. Let me check on buck boost cv cc. Thank you again for your help

[james_s]

I highly recommend using a proper charger to charge Li-ion batteries unless you know exactly what you're doing. The batteries are notorious for bursting into flames if abused, and the margin between fully charged and on fire is often a few hundred millivolts.

[Adhith]

I highly recommend using a proper charger to charge Li-ion batteries unless you know exactly what you're doing. The batteries are notorious for bursting into flames if abused, and the margin between fully charged and on fire is often a few hundred millivolts.

Thank you for warning me in advance james. I would really consider your suggestion. The reason that I'm not going for a proper charger was to make it portable and more convenient to carry around. What if I provide the input voltage 1 or 2 Milli volts lesser than the full charge voltage and thus avoiding the margin of risk of fully charged and on fire??