Another another electrical question
Submitted: Thursday, Jul 30, 2009 at 21:36
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12ian34
Sorry, i put this question in an older thread but not sure if people read the older ones or not.
If i have a 25 amp batt charger parallel to a load with a 10 amp fuse will it cause the fuse to blow because there is a 25 amp supply in the circuit or is it only a problem if i try to draw more than 10 amps; will a smaller load be okay.
I dont understand if a 25 amp charger/supply pushes out 25amps or has up to 25 amps to be drawn upon?
Not sure if this makes sense.
Reply By: Robin Miller - Thursday, Jul 30, 2009 at 21:46
Thursday, Jul 30, 2009 at 21:46
It has up to 25 amps to be drawn apon , which if the fuse is in series will blow at some stage. (I assume the fuse you refer to is on the battery side not in the chargers 240vac input (if its a mains operated charger)
AnswerID:
376873
Follow Up By: 12ian34 - Thursday, Jul 30, 2009 at 21:57
Thursday, Jul 30, 2009 at 21:57
Its a 240 AC charger. The fuses are in 12v DC circuits coming from the battery like a CD player and lights.
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Reply By: Member - Phil G (SA) - Thursday, Jul 30, 2009 at 21:58
Thursday, Jul 30, 2009 at 21:58
Your 25 amp power supply will only deliver 25 amps if the need arises. No, it doesn't "push out" 25 amps.
I expect the battery charger is protected by its own fuse.
There is no problem in putting loads of less than 10 amps behind a 10 amp fuse.
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Follow Up By: 12ian34 - Thursday, Jul 30, 2009 at 22:01
Thursday, Jul 30, 2009 at 22:01
Thanks for your help
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Reply By: techo2oz - Friday, Jul 31, 2009 at 06:57
Friday, Jul 31, 2009 at 06:57
Liken it to your normal car battery. It can supply 600 amps + but under normal conditions the fuses don't blow.
However should a fault condition develop, that is when the load tries to draw upwards of the fuse rating and it fails, thus hopefully preventing further damage and fire.
AnswerID:
376901
Reply By:- Friday, Jul 31, 2009 at 09:00
Friday, Jul 31, 2009 at 09:00
Your charger will certainly try and push out 25A whenever it is told to charge a battery AND the voltage between the charger leads is low enough which signals to the charger - full steam ahead!
Keep in mind though, the charging current only flows out the positive charger lead and comes back in through the negative charger lead. Whatever is in its path will get to 'see' the high current (i.e. the battery).
If you hook up your charger directly to the battery terminals, then all will be fine and only the battery gets to see the current.
But if you hook it up say charger 'minus' to battery 'minus' and charger 'plus' AFTER the battery line fuse, then the full charging current will flow through the battery VIA the fuse which will certainly blow a 10A fuse (during bulk charging) and the charging will stop.
Hooking the charger up in such a way only makes sense if the battery is fully charged (i.e. it won't draw a lot of charging current), AND you intend to power loads in excess of 10A.
This way you won't blow the fuse, don't discharge the battery and can run loads up to 25A powered by the charger for as long as you like (as long as you can trick the controller inside an intelligent charger to do this for you).
Hope to have all your intentions covered now.
AnswerID:
376923