Looking for 12v DC UPS

[duffbeer911]

Hi,
I'm trying to find a small UPS that has 12v output (only need about 10w) and can switch between 240v mains and a 12v supply from my charge controller.
I've had a bit of a look online and amazon but I don't want the UPS to also charge the batteries as this is done through solar.
(Basically I want to set up a modem so that when mains drops out the UPS will switch over to my solar charged batteries)

Thanks for any advice, help, links!

[Mike90250]

I dont think it exists.

UPS are all generally a Mains Backup. You would plug the wall wart for your modem into the UPS

To do what you ask, would require you butcher the UPS and purchase a solar charge controller to charge the battery with.

[Logan5]

I have a 12v UPS for our DVR, it's made by CyberPower and cost around $70. Our DVR takes 2 min's to reboot from even the slightest power loss. The 12v UPS has eliminated waiting for the reboot. We also use a 12v UPS on one of our security Displays, so even in a power outage, we can still see video from our security cameras.

[Logan5]

Adding solar complicates things greatly and will shorten your battery life.

[SunEagle]

Adding solar complicates things greatly and will shorten your battery life.

I am glad you added this post.

Some people still don't get it that using a solar / battery system is more costly than a grid tie solar pv system and adds to your work load to keep the batteries happy and safe.

[duffbeer911]

Thanks for the replies. I had seen this:
Https://www.amazon.co.uk/dp/B01K9SM7..._9TMoAbDVC2GZ4
But I thought I didnt need the battery charging component of it.

[Logan5]

https://www.amazon.co.uk/CyberPower-PR2200LCD-12V-18Ah-Battery/dp/B00G5FZJ1O/ref=sr_1_9?s=electronics&ie=UTF8&qid=1513787501&sr=1-9&keywords=cyberpower+12v+ups

[Sunking]

Super easy to do a 5th grader can build it.

12 Volt Battery Charger > Battery > 12 Volt Gizmo.

Size the battery charger large enough to charge the battery at C/10 plus the Gizmo device power. Gizmo will use AC power when available, and battery when the lights go out. That is exactly what the pros do like phone, cellular utilities, CATV military, data centers, and 911 communication centers. Difference is they use 24, 48 and 144 volt batteries.

[solardreamer]

Hi,
I'm trying to find a small UPS that has 12v output (only need about 10w) and can switch between 240v mains and a 12v supply from my charge controller.
I've had a bit of a look online and amazon but I don't want the UPS to also charge the batteries as this is done through solar.
(Basically I want to set up a modem so that when mains drops out the UPS will switch over to my solar charged batteries)

Thanks for any advice, help, links!

Not really an UPS but since you only need low power 12V and assuming your 12V solar charge controller has a controlled load output to prevent battery over-discharge then this may work:

Y-Adapter

Mains => 12 AC/DC Adapter ========================|

|=======> Modem/12V Load

Solar => Charge Controller => Load Output ========|

|
|
12V Battery

[PNPmacnab]

A device will draw power from the highest voltage available if it can supply the current. In situations like this, a diode isolating the battery is generally used. With the loss of grid power, the battery seamlessly takes over. The 12V to the server is not critical as it is regulated down to a lower voltage. You expressed the desire to not use any battery power when the grid is operating. Battery voltage can be over 14V. In that case you would have BATTERY > BUCK CONVERTER > DIODE > SERVER. The buck converter voltage would be set to just below the grid power supply voltage, say 11.5V. The battery will only power when the grid goes down. While cheap to do, I don't sense you have sufficient technical knowledge. You could easily do damage from a small error.

[Sunking]

A device will draw power from the highest voltage available if it can supply the current. In situations like this, a diode isolating the battery is generally used. With the loss of grid power, the battery seamlessly takes over. The 12V to the server is not critical as it is regulated down to a lower voltage. You expressed the desire to not use any battery power when the grid is operating. Battery voltage can be over 14V. In that case you would have BATTERY > BUCK CONVERTER > DIODE > SERVER. The buck converter voltage would be set to just below the grid power supply voltage, say 11.5V. The battery will only power when the grid goes down. While cheap to do, I don't sense you have sufficient technical knowledge. You could easily do damage from a small error.

Well you can do that if you want, but you are trying to reinvent the wheel and throw more money than need be, and make it more unreliable. Telephone companies and utilities have been doing this for 100 years and no improvements can be made. Well the only improvement you can make is what pros do, use a generator for extended outages to supply power to the charger when commercial power is OOS for extended periods

Battery Charger > Battery > Load

You set the battery charger to 13.2 to 13.8 volts depending on the battery recommended Float Voltage and you are done. So simple a kid can build it. As long as there is commercial power, the load uses AC power from the charger and the battery FLOATS. When power fails the battery is already on-line and takes over. Works exactly like a Dual Conversion UPS without the Inverter. Dual Conversion UPS are the most expensive and best UPS money can buy and used by professionals.

The only thing that needs to be figured out is how long you want the battery to last so you can size the battery and charger. As an example if the device draws 42 watts and you want 24 hours run time is 1 Kwh, so the battery needs to be 2 Kwh for 50% DOD or if using AGM 1.25 Kwh to 80% DOD. That works out to 167 AH and 100 AH respectively.

The battery charge is super simple to figure out. At C/10 is more than enough to supply the load and recharge the battery, so you are looking at 15 amp charger using a FLA battery, and 10 amp charger using AGM.

No diodes, no converters, nothing else required. Just a simple inexpensive float charger and a battery. The only way to improve it is to have a generator to plug the charger into if you want more emergency run time than the battery can provide. Want to make a UPS, add an Inverter and you have a hackers UPS. It is simple and anything else would be a down grade and just adds another egg in the basket to break down.

Most anything made to run off 12 volt battery will work from 10.5 to 14 volts. It has to do that in order to utilize the full capacity of a 12 volt battery. Only difference between that and what a telco or cell tower is they use 24, 48, and/or 144 volts. Large scale UPS uses up to 600 volt batteries.