Hello,
We have often mains shortage in my village and i want to use (create? preferably buy?) 12V ups i.e. continues 12V supply, mainly for an arduino+enet shield, a router modem and in rare occasion a ~1A siren. I bought a 9AH sla battery snd a 'smart' charger but am disappointed that the charger's fan runs non stop and also that it loads the battery by ~70mA when disconnected from mains. Also, its notice states that it should be disconnected from the battery when its full where i need a system with no human intervention. Has someone a reliable solution?. Btw, i already have a good solution for a stable 12V (and 7.5V for ino) out of a Vbat in the range of 10-15V.
Many thanks in advance!

 

There are smart "maintenance" chargers with no fan that can be continuously connected to the battery and go to a low trickle-charge when the battery is full.
What is the charger brand, and its maximum charge rate?

 

Thanks you Crutschow for your reply!
The brand is bought on Ali Express. Attached pics and the 'user manual' of the charger. Something else odd about this device is that it measures internally the battery's temperature(!)

 

The charger looks to be properly designed.

The battery voltage is affected by temperature, so that's why it measures the temperature.

If the charge voltage in the float mode is about 13.5V (measured after 12 hours of being in that mode) than you can leave the charger connected all the time, but if the fan being on is a problem, then you will likely need to go with a charger than has no fan.

 

Ok, I did find charger w/o fans by looking with the keyword "maintenance" that you've suggested.
I understand that the charging params depends upon the ambiant temp of where the battery is being charged but it seems to me that this temp may largely deviate from that measured inside the charger.

Thanks again for your help. I will buy another one more suitable to my 9AH battery and with no fan. Ill be happy to hear from you a recommendation for a reliable one

 

Ill be happy to hear from you a recommendation for a reliable one

Unfortunately I'm not that familiar with particular brands to recommend one.

 

Solar? If it's just for backup, a small solar panel (5 to 10 watts) and a $10 PWM charge controller should keep the battery topped up.

 

Here is what i bought for a 9AH battery. This one is hopefully w/o fan