Li ion battery charger with multiple charge points - Page 1
Forum section: electronics / projects

author: rakeshm55
author_rank: Regular Contributor
timestamp: May 29, 2012, 05:40:46 pm
content: Hi,In one of my application I need to meet the following requirement for charging 10 Li ion batteries simultaneously.Requirement -Single cell Li ion charger 3.7VChannels - 10Charge current - 1A.Charge Mode - CC-CVIndication - LED (Charging , and Done) for each channelInput Voltage - 230V ACI have only worked with Linear chargers (Li ion )before .Here should I use a Linear or Switching type?? Considering the thermal management etc.I have never worked with 230V before will I get plug in modules which can handle the 10A current rating.... Will a PC SMPS do the trick for 5V high current o/p from line??Can any one suggest a suitable cabinet for such a designAny suggestions are welcome

author: T4P
author_rank: Super Contributor
timestamp: May 29, 2012, 06:33:15 pm
content: Of course switching ...You should use 12V as input voltage but ah well

author: rakeshm55
author_rank: Regular Contributor
timestamp: May 30, 2012, 04:58:48 am
content: I have seen many of Battery chargers and Battery fuel guages have Thermistors for temperature monitorWhy do we use an NTC (thermistors) when charging battery???Is it to monitor the charger IC temp or battery pack temp or just surrounding temperature....

author: T4P
author_rank: Super Contributor
timestamp: May 30, 2012, 08:48:45 am
content: Quote from: rakeshm55 on May 30, 2012, 04:58:48 amI probably think the NTC is in series with the battery so when it's charging it's resistance goes down and then near completion the NTC resistance goes high ...or it can be in parallel and goes to a comparator that when it begins charging the resistance of the battery is low so the NTC doesn't heat up but when the battery goes high the current starts pass through the NTC because of ohms law ( electrons simply follow the lowest resistance path )

author: Rerouter
author_rank: Super Contributor
timestamp: May 30, 2012, 09:13:00 am
content: being how they are li-ion cells, i would imagine the NTC thermistors would be to monitor the temperature, going to a comparitor with a significant hysteresis so that it resets and tries to continue but only once the cell has cooled back down, say tied to the enable pin of the charge controller,to keep the costs down i would probably chase 10 seperate charge controller chips, as single cell cargers are far cheaper than dual cell ones, also helps for seperate temperature regulationas for using an ATX PC Power supply, yes your generic unit should be capable of 10A at 5V, but have a look on the label on the side, and whatever value it says for 5V times it by 0.7, as you want overhead and sometimes 5V ratings can be a little fudged, e.g peak rating, to hotwire "most" ATX supplies, on the 20/24 pin big plug, use a paperclip or a piece of wire to bridge between the green wire and any black, that should get it capable of running in a way you can test it with,other suggestion would probably be to use a 13A fuse on your 5V tie in, (keep you from hurting the supply) and a 1.5A per charge controller (stop you from hurting a chip or cell), as playing with a hotwired supply carries the significant risk of a short,also when running of a atx supply of unknown origin, make sure your charge controller can handle 6.5V max, though very very rare i have seen ramp up peaks that high in some supplies,

author: T4P
author_rank: Super Contributor
timestamp: May 30, 2012, 12:57:30 pm
content: One Hung Low comes to mindi have seen some come with the standard OHL 'package' i.e no inductors or just those badcaps