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what amperage

Defib

Nov 15, 2010
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Nov 15, 2010
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Hello

I am designing a basic portable power pack and I am planning on using a 12v SLA with 7Ah rating.

Basically it will, when required, need to have a cigarette charger for a cell phone plugged into it and other basic items.

What draw will the cigarette lighter charger for my phone have??

Is my selection of SLA correct??

Will it drive a 12v to 240v Waeco 150w invertor??

Please assist, I'm not tooo clued
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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The current it draws will depend on the phone. You can measure this easily if you have a multimeter. The 7Ah SLA seems entirely adequate for this.

It would drive that inverter at full power for approximately 20 minutes.
 

Defib

Nov 15, 2010
3
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Thanks for your reply

So if I use the SLA with say an inline fuse and the car cigarette charger it would be ok???
 

barathbushan

Sep 26, 2009
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There is no doubt , that a phone can be charged with your sla battery , since it consumes around 5 to 8 watts , depending on your style of charger , if you use a switched mode charger , you will get higher efficiency than a linear charger

but i wouldn't connect a 150 watt load , at 12 volts full power , the current drawn is about 12 to 13 amps , which is too high a discharge rate for a 7ah battey .which results in sulfation and shortens the battery life .
Like steve said the battery will last 20 minutes , but steve should have known that sla
batteries are not designed to discharge to less than 20 % of the capacity , as sla batteries are not regular "Cyclic" batteries .

but you can overcome this problem by connecting two same 7ah batteries in parallel , thereby increasing the capacity of the battery to 14 AH at 14 volts , then you can use your inverter to about 45 minutes
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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but i wouldn't connect a 150 watt load , at 12 volts full power , the current drawn is about 12 to 13 amps , which is too high a discharge rate for a 7ah battey .which results in sulfation and shortens the battery life .
Like steve said the battery will last 20 minutes , but steve should have known that sla
batteries are not designed to discharge to less than 20 % of the capacity , as sla batteries are not regular "Cyclic" batteries

I'm not sure that I agree with your assumptions about what I should and shouldn't know.
 
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