Cheap Backup Option for running Modem during Powercut?

Anyone knows any cheap backup option to run wifi modem during powercuts?? I have frequent powercuts and I want to use some method to run my modem even during powercuts?

I was thinking to buy a UPS battery of 7AH and run modem directly since the modem requires 12V and 0.5A. Any one knows how much Backup it will give if I use it?

Or any option cheap option under Rs.1000 to give atleast 2hr backup?

Thank you.

Imho, UPS is a bad choice if you have long outages (over 15 mins) as it will kill the battery in no time.

Recommendations:
1. There are portable mini inverters with inbuild 12V 7Ah battery available online (~50 watt) for ~1.5 k. They have rated backup of 3 hours and are designed for long outages.

2. You can also buy a mini solar powered inverter for close to 2 k.

Hi,

I do not intend to buy a UPS as I already have a double battery UPS.

I meant using a UPS battery directly to run a modem i.e. via DC connection.

hey check this out

Source


i found small inverter with small battery

you can contact ppl at india mart for new models available

buying guide

Source

Shivam15 said:

Hi,

I do not intend to buy a UPS as I already have a double battery UPS.

I meant using a UPS battery directly to run a modem i.e. via DC connection.

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7 Ah will last more than 5 hrs easily. How do you plan to charge it though ?

^^ I have a small charger thing to charge battery.

Also, do you know how much Ampere comes out from a 7AH battery? Because our modem requires 0.5A only.

Get CFL inverter , you can easily get 3-4 hours back up on Modem with CFL inverter costing around 2k

Shivam15 said:

^^ I have a small charger thing to charge battery.

Also, do you know how much Ampere comes out from a 7AH battery? Because our modem requires 0.5A only.

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The current draw will be 0.5 A.

Only thing to ensure is that the voltage should match.

So I have been pondering over this for a while and I came across a seemingly good solution. The problem with the traditional PC UPS is that it simply does DC --> AC --> DC leading to significant and un-necessary losses. As @Shivam15 mentioned earlier, using a 12V battery without the un-necessary DC --> AC --> DC conversions is a much efficient solution.

I came across this power supply with UPS function -- https://www.meanwell-web.com/en-gb/ac-dc-enclosed-power-supply-with-ups-function-psc--60a--c
Costs Rs 1200 + tax, its a 60W power supply and probably is more than required for many of your use cases, but there is a 35W variant too which is probably cheaper.

Anyway this device also comes with a 1.5 A battery charger which means we can use higher capacity batteries, maybe a 12 AH battery. This would require a bit of DIY as you would need to procure the different connectors, casing etc, and even though it might be a bit more expensive, it's would be much more efficient and hence a much higher backup time.

Based on rough calculations, I think we could get maybe around 8-10 hour backup with a modem and a router connected. Will keep the post updated as I make more progress. As of now I have just procured the power supplies.

you still will be doing DC --> AC --> DC . so no change but yes rather than say 500W regular UPS, you now have capacity of 60W so the losses will also reduce to that extent.

On the other do keep in mind that if you change battery the charger coming with this UPS circuit might not be powerful enough to charge your bigger battery, which will spoil your whole plan.

@ijsa How would it be doing DC --> AC --> DC? I'm confused, the only conversion is AC --> DC while the AC power supply is available.
The device I mentioned gives 12V DC output which you can use to directly power the modems and routers. It is basically a DC power supply with UPS function and battery charging circuitry.

This is not something taken out from a regular UPS, please refer to the data sheet and you will know. It can supply 1.5 A charging current which is good enough for a 12 AH battery from what I read.

Source

Most of the modem/ routers I have seen, use adaptor with 5V DC output, so if your router/ modem requires 12V DC input then it is good.

And please check charging current again for 12AH 12V battery....... what I read 1.8A required for 7AH battery.

Your normal inverter would work. Just get a electrician to wire your socket (near modem) to inverter.

ijsa said:

Most of the modem/ routers I have seen, use adaptor with 5V DC output, so if your router/ modem requires 12V DC input then it is good.

And please check charging current again for 12AH 12V battery....... what I read 1.8A required for 7AH battery.

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Well, almost all my devices are rated at 12V DC, I think I have one which needs 9V but then it works with 12V as well. I haven't recently come across many devices which needs 5V, even if you need one, I think a simple step down converter would do and DC-DC step down is much more efficient from what I could see.

Regarding the charge current for a lead acid battery, when operating in a floating or standby mode, something around 10-30% of its capacity works. For cycling mode, it's higher.

So for 12 AH battery it can be 1.2 to 3.6 A or so. The only difference being it would take a bit longer to charge, plus for extending battery life the lesser the C rate the better.

I felt for a 12 AH battery, charging at around 1.5A seems like a good balance.