Hi guys i recently found my old Energie Station (german brand name form Einhell) which was a 50 Ah sealed Pb gel battery with a charger and some cigarette lighter outlets. I want to do a little water camping trip in the summer and wanted a small reliable energy source for charging my phone and cameras. the Pb battery is dead and now the question arose to replace it witch 18650 cells. I have a few 2p4s packs and 3 of them have the exactly same size a the pb battery.
My question is if i use the 2p4s cells and connect them in parallel i get 10v if they are completely (2,5v) per cell empty and 16,8 completely charged (4,2V per cell).
For a cigarette lighter output both is wrong. I also want to be able to charge everything off a 12v outlet at camp stations or my car.
My idea is to use one stepup converter so get 16,8V for charging to the bms and one boost buck converter to get 12 v to the outlets maybe also two one for each outlet.
is there an easier option or are my thoughts correct. I will put fuses in front of the outlets so hopefully only the will blow up in case of an overload or short. Charging is no problem because the cells already have a bms fitted to them
thanks for your help
Albach
edit 1
one further question i found the cells (cgr18650CG from panasonic) original data-sheet (http://www.meircell.co.il/files/Panasonic CGR18650CG.pdf) which specifies a 430mA continuous discharge current but also shows the discharge characteristics with 4.3 amps per cell on some onlinestores they specify them as 10 A cells but down in the specification max continuous discharge current is given at 430 mA
edit 2
i know that the original device (medical monitor) drains the whole 2p4s pack in 1 hour so it has to draw 10A corresponds to 5 A per cell
My question is if i use the 2p4s cells and connect them in parallel i get 10v if they are completely (2,5v) per cell empty and 16,8 completely charged (4,2V per cell).
For a cigarette lighter output both is wrong. I also want to be able to charge everything off a 12v outlet at camp stations or my car.
My idea is to use one stepup converter so get 16,8V for charging to the bms and one boost buck converter to get 12 v to the outlets maybe also two one for each outlet.
is there an easier option or are my thoughts correct. I will put fuses in front of the outlets so hopefully only the will blow up in case of an overload or short. Charging is no problem because the cells already have a bms fitted to them
thanks for your help
Albach
edit 1
one further question i found the cells (cgr18650CG from panasonic) original data-sheet (http://www.meircell.co.il/files/Panasonic CGR18650CG.pdf) which specifies a 430mA continuous discharge current but also shows the discharge characteristics with 4.3 amps per cell on some onlinestores they specify them as 10 A cells but down in the specification max continuous discharge current is given at 430 mA
edit 2
i know that the original device (medical monitor) drains the whole 2p4s pack in 1 hour so it has to draw 10A corresponds to 5 A per cell