Vroomtattat 2nd Gear September 17, 2010 Share September 17, 2010 I'm a noobie at electrical stuff and would be glad if any expert out there can help me with this. 6 small pc fans each rated at 12V 0.12A, connected in parallel to a 12V sealed lead-acid rechargeable battery (7.2Ah). How long can the fans run? 7 hours? And what is that measuring device which can measure voltage called? Volt meter? The one which technicians use to check for connectivity or something? Where can I get one and how much is it. Heh hee . . . . sorry arhh, totally clueless when it comes to electrical. Please advise. Thank you. ↡ Advertisement Link to post Share on other sites More sharing options...
Zztensor Neutral Newbie September 17, 2010 Share September 17, 2010 I'm a noobie at electrical stuff and would be glad if any expert out there can help me with this. 6 small pc fans each rated at 12V 0.12A, connected in parallel to a 12V sealed lead-acid rechargeable battery (7.2Ah). How long can the fans run? 7 hours? And what is that measuring device which can measure voltage called? Volt meter? The one which technicians use to check for connectivity or something? Where can I get one and how much is it. Heh hee . . . . sorry arhh, totally clueless when it comes to electrical. Please advise. Thank you. Try this website for info http://www.windpowerunlimited.com/batteries/Amp_Hours.htm Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 should be 10 hrs...each draw 0.12A so 6 fan will draw 0.72A..the battery can provide 7.2A for one hr....which means drawing 0.72A....it will last 7.2/0.72 = 10 hrs... the thing is call multi meter....Sim lim tower can get very cheap 1....nothing more than SGD15-20 for a simple 1 which can measure current...DC...AC...resistant...diode etc...... Link to post Share on other sites More sharing options...
Zztensor Neutral Newbie September 17, 2010 Share September 17, 2010 should be 10 hrs...each draw 0.12A so 6 fan will draw 0.72A..the battery can provide 7.2A for one hr....which means drawing 0.72A....it will last 7.2/0.72 = 10 hrs... the thing is call multi meter....Sim lim tower can get very cheap 1....nothing more than SGD15-20 for a simple 1 which can measure current...DC...AC...resistant...diode etc...... 10 hrs is theoretical....according to tat website, actual hours will be less (see tat graph). Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 ya lar....if temperture etc etc etc all taken in....but i guess what TS need is on theory and he probably not interested up to the last seconds... Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 Thanks bro, I googled but cannot find Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 Thanks bro, so this is how you calculate. Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 ya lar....if temperture etc etc etc all taken in....but i guess what TS need is on theory and he probably not interested up to the last seconds... Wah the batt damn heavy man . . . About the size of 5 ciggy packs thia . . Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 no problem...hope my little knowledge can help u... but as what bro Zztensor mention...it is in theory...so if you are doing something critical...do put in some safety factor..... Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 Another stupid question . . . How do I connect the ends of the batt charger to the battery? Positive first or negative first. I scared later KaPOOM! Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 well..it is all lead and liquid....ha ha ha.... Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 i think is positive first follow by negative...but i am not very sure...better wait for other bros help.... Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 no problem...hope my little knowledge can help u... but as what bro Zztensor mention...it is in theory...so if you are doing something critical...do put in some safety factor..... Don't frighten me leh brudder . . . I doing this hare-brained car ventilation project . . . heh hee, jia pa boh dai ji zheo Link to post Share on other sites More sharing options...
Yeobh 4th Gear September 17, 2010 Share September 17, 2010 If you have a quality battery charger, don't worry as all have polarity protection switch. Since you are charging the battery at home ( not connected to the car system) which ever terminal you connect does not matter at all. Good luck in yr DIY Link to post Share on other sites More sharing options...
Seaweed 1st Gear September 17, 2010 Share September 17, 2010 do show post your DIY to let us look look when done leh.... Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 If you have a quality battery charger, don't worry as all have polarity protection switch. Since you are charging the battery at home ( not connected to the car system) which ever terminal you connect does not matter at all. Good luck in yr DIY Okay bro, I'll try now in the office. Link to post Share on other sites More sharing options...
Vroomtattat 2nd Gear September 17, 2010 Author Share September 17, 2010 do show post your DIY to let us look look when done leh.... See how first, if fei loh then I'll keep quiet. If it works, I will share with my MCF brudders. Actually, anyone can DIY this lah, no big deal. Link to post Share on other sites More sharing options...
Happily1986 5th Gear September 17, 2010 Share September 17, 2010 1.) Calculate impedance of each fan using input voltage = 12V and input current = 0.12A Impedance is taken to be approximately the resistance of the fan Thus R =V/I = 12V/0.12A = 100 ohm 2.) Total impedance/resistance of the 10 fans Since fans are in series, we have to utilise the parallel addition rule. 1/(total resistance) = 1/(resistance of fan 1) + 1/(resistance of fan 2) + ... + 1/(resistance of fan 10) Taking reciprocal, total resistance = 10 ohm 3.) Current flowing in parallel circuit (with all the fans connected) Current I = V/R I=1.2 Ampere 4.) Stamina of electrical setup Time = Amperage hour / (current drawn) = 7.2Ah/ 1.2A = 6 hours 5.) We cannot assume that heat generation i.e. wastage is minimal thus you should expect the stamina time to be below 6 hours. ↡ Advertisement Link to post Share on other sites More sharing options...
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