uninterruptible power

Hello,

I bought a UPS (APC 10001) for my arduinos / Internet equipment (router modem and phone i/f). What I see is that most outages do restart the arduino boards and the router.

Since all the equipment can be powered from 12Vdc and less, I was thinking of replacing the ups with a 12V lead battery (?) of around 10Ah and am looking for a reliable system to have it continuously charged while there’s no outage, ideally, something actually in operation flawlessly for a long time.

Expected current out of the battery is ~2.5A

Help is most appreciate

Guy

guy_c:
Hello,

I bought a UPS (APC 10001) for my arduinos / Internet equipment (router modem and phone i/f). What I see is that most outages do restart the arduino boards and the router.

Since all the equipment can be powered from 12Vdc and less, I was thinking of replacing the ups with a 12V lead battery (?) of around 10Ah and am looking for a reliable system to have it continuously charged while there's no outage, ideally, something actually in operation flawlessly for a long time.

Expected current out of the battery is ~2.5A

Help is most appreciate

Guy

Unless you spend several thousand dollars, you have a "standby power supply". It contains a relay to switch to it's internal AC generation. Somewhere in the detail spec it should tell you the time to switch. That is why some devices re-boot when there is a power interruption.
Also, your UPS contains a perfectly usable 12 volt battery that is continuously monitored and charged. Use it!
Paul

I have a UPS built from 4 x 12V lead acid batteries in series, a 5A 50V PSU set to 52.8V (2V2 per cell) and an inverter. The batteries are floated across the supply, the power supply charges the batteries and supplies the inverter, the inverter supplies the load.

If you don't want the conversion back to mains then use a buck converter(s) to the voltages(s) you need.

You should be able to do that lot for £100 if you only want a 12V battery.

A few things to consider. Since transfer time is a concern:
"The transfer time depends on the UPS technology, and falls between zero and 12 milliseconds. The online UPSs have a zero transfer time while standby UPSs have an average of 8ms. The typical transfer times are: Standby UPS: 5-12 ms, – average 8 ms".

Next is a UPS can use any of several outputs. The preferred and slightly more expensive is a TSW (True Sine Wave) output which is what AC mains have, a true sine wave. Next is a MSW (Modified Sine Wave) output which closely resembles a square wave. Whatever your power supply is it needs to be compatible with a MSW output or whatever output your UPS has.

"Since all the equipment can be powered from 12Vdc and less, I was thinking of replacing the ups with a 12V lead battery (?) of around 10Ah and am looking for a reliable system to have it continuously charged while there's no outage, ideally, something actually in operation flawlessly for a long time.

Expected current out of the battery is ~2.5A"

With that in mind a 10 AH 12 Volt SLA battery will last about 4.0 hours. A common approach is just to place a battery tender on your battery and leave it there. During the cold winters here in NE Ohio US I leave a battery tender on my motorcycle 24/7 and maybe once a week I start and run the bike for about 15 min. The tender keeps my bike battery topped off. If you go this route shop wisely. I have seen the same 750 mA to 1.0 Amp tenders go from $20 USD or less to $99 USD for the same identical units. I have a few of the $19 ones which work just fine and I leave them connected 24/7.

You need to decide how large of a battery you want?

I use several UPS units all made by APC which serve us fine but they run less than a min during a power outage before the whole house generator is up and running. If all you want is 12 VDC I see no reason to recreate mains voltage only to reduce it to 12 VDC. Also, it doesn't hurt to place a large cap in front of your load. Especially if using a UPS and transfer time is a concern.

Ron

Do it the easy use 1 or two batteries in series and then use SEPIC converters, especially if you use 1 12V battery. Buck converts generally need some overhead voltage which you will not have with a 12V battery. 48V systems are nice but most of the buck converters from China will not work at that input voltage.

I would suggest you contact APC and ask them if what you are seeing is what they expect. Just to be sure the device is working as it should.

If you decide to go the battery route, I would suggest the purchase of a small 12V Sealed lead acid battery. Float it on a 12Volt source running from you APC. Sealed lead acid batteries are designed for this purpose. They handle being connected to 12VDC for long times then coming to life when needed.

It needn't be a big battery, only enough to bridge the short loss of the APC output. Perhaps something like This battery.

I would add fuses in the lines going to each device. Wall warts have current limiting, Batteries don't.

@JohnRob
I don’t think ill discuss this with apc. Im sure of what i say. Not only my arduinos rebiit, the touter too: ip is changed. Luckily arduinos sends me the new ip so i can update noip service.

As for 12v on apc, where is there a 12v connector??

I was thinking of a ~3A current source with a linear 15v regulator which would shutdown at, say Vbat=13.5V. the thing would be powered by a 18v laptop ps while mains are active

Bought a 'smart battery charger' capable of 6A. Will test and report results here

If you have a relay powered directly or indirectly (ac2dc converter) and you use the N.C. contacts for your backup system, when the AC goes out, the relay disengages, connecting the N.C. (WHICH IS OF COURSE OPEN when the
relay is ON), which in turn connects your battery powered backup system to whatever.
AC ON, backup system disconnected.
AC OFF , backup system connected.

guy_c:
@JohnRob
I don't think ill discuss this with apc. Im sure of what i say. Not only my arduinos rebiit, the touter too: ip is changed. Luckily arduinos sends me the new ip so i can update noip service.

As for 12v on apc, where is there a 12v connector??

For the 12V I had envisioned a simple wall wart. 120 AC in 12V dc out. Simply connect it to the sealed lead acid battery. You could also use a 6V sealed and an 6V wall wart but these seem harder to get.

JohnRob:
For the 12V I had envisioned a simple wall wart. 120 AC in 12V dc out. Simply connect it to the sealed lead acid battery. You could also use a 6V sealed and an 6V wall wart but these seem harder to get.

Assume a steady ~2A flow to my loads, the (wall wart) power supply would need to be capable of injecting this current and keep the battery full in order to dispose of it’s AH capacity. This implies a supply > 12V and may be harmful to the battery if not correctly managed. This is why I bought the “smart” or “intelligent” charger. These would be designed to allow indefinite connection to the battery. I may need perhaps, to add some shut down logic which monitors the battery voltage (during outage) and shuts down (with hysteresis) the supply to the loads below a tbd voltage