Yes, yes, yes. Battery backup system notes. Server notes. As I have stated in my previous notes, there is no shortage of lithium-ion battery backup packs that can be used to power network switch and router devices. But those are only useful in places that have frequent power outages. For our place that only has a power outage of 2 hours once every 1-2 years on average, that is not going to be an efficient system. No, we need a system that instead runs off of alkaline batteries. So let’s see. Is there such a system you can buy on the Internet? The sort answer appears to be no. If you want to get a good system that works to your precise specifications, you should build one yourself.
20170611/DuckDuckGo D battery ac dc backup power supply
Build a battery backup out of 2 x AA NiMh rechargeable batteries for an alarm clock. The circuit uses a DC input jack.
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Again, I reiterate, because this is important! I searched for this and found it, that means it’s important!
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NiCd and NiMh batteries can be charged in series. However, make sure you properly limit and regulate the voltage if you do this.
20170611/https://www.allaboutcircuits.com/projects/battery-backup-power-supplies/
20170611/DuckDuckGo build AA DC battery backup power
20170611/https://raspberrypi.stackexchange.com/questions/1360/how-do-i-build-a-ups-like-battery-backup-system
MUPS, Mini UPS & Power Sensor? You can buy just that and it takes in AA batteries? Cool. But it costs $120! Not cool.
20170611/DuckDuckGo mini ups and power sensor
20170611/https://avtech.com/Products/Sensors/MUPS.htm#features-specifications
The good news is that such a circuit should be relatively simple and easy to build. Basically, on the input end, you have your output from your 12 V DC power supply that is powered from 110-120 V AC. That is connected to your circuit with a diode to prevent your battery power from backfeeding into the DC power supply. Next, for my particular configuration will come some capacitors that get charged from DC input power and can also power the output. The purpose of this is to provide a smooth current switching operating when DC power goes out. Basically, this takes the place of the rechargable batteries in the previously mentioned circuit designs. Additionally, a relay is added into the circuit, powered by the batteries, that detects when DC power input is not functional and switches on to provide the battery power to the circuit as proper. Why a relay? I was thinking using a transistor, but maybe transistors can’t handle 12 V?
Importantly, the speed of the power switch device is critical in determining the needed capacity of the buffer capacitors.
Finally, on the output end, you have a switched-mode power supply to power your electronics, so even when the battery runs low, the electronics will still get the same input voltage. Oh, also importantly, you need to make sure you buy the right DC jacks to connect with your electronics, and for convenience, I would recommend using a single power system and multiple DC jacks to power our separate network hardware pieces like both the router and the cable modem.
Oh yeah, and what else does this circuit do? When the batteries are too weak to provide enough power, the relay can be disengaged to prevent further battery discharge. Oh wait, do we need a switched mode power supply to power the relay too? Also, I thought the switched mode power supply itself prevents further drain when the batteries are below 10%, so such fancies are not needed. Okay, maybe you’re right.