Battery charger

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#1
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Hi,
I have replaced battery of my UPS and now I have a working 12V 7.2AH SLA battery.

It would damage if it is not charged over a period.

so I decide to make a DC 12V UPS for my wifi router that's rated 9V .6A. It will automatically switch to battery supply in absence of main supply.

I found a wall adapter that gives me clean 12V and max current limit is 1.5A.

I found this circuit on net http://www.techelex.com/2010/12/mini-ups-system.html

which i do not trust 100%

as I read at few other places that 12V battery needs 13.8 V to charge and my 7.2AH battery should be charged only at AH/10 e.g. .72A current.

Can my adapter 1.5A provide enough current to .6A router + .72A battery charger =1.32A?

I really do not want to buy more stuffs here (I got thing that I need for the circuit i mentioned before) but I do not want a fire in my house too (This setup will usually be running 24/7 and mostly unmonitored).

Please let me know your valuable suggestions.

Thanks,
K

Another reference is http://www.talkingelectronics.com/projects/BatteryCharger-12vSLA/BatteryCharger-12vSLA.html

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If the adapter output is only 12 volts, the battery will not charge properly.

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mikericetga wrote:
If the adapter output is only 12 volts, the battery will not charge properly.

thanks, but what do i do can i step it up by couple of volts?

Regards,
K

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You can step up your wall adapter. So you will need to build a step up regulator.
Your wall adapter is rated to 1.5A as you said you need 0.72A plus the regulator, suppose 80% efficiency, you are ok.

Here in brazil there some really bad wall adapter, non regulated output, they don't support the current rated in their specifications.

Google battery charger, there are some simple ckts...

Regards,

Bruno Muswieck

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Will this work for you (shameless promotion)
http://ki0bk.no-ip.com/~PWRgate/...
You will need a 13.8v supply (radio shack perhaps) and a 9v regulator on the output.