Ups with large capacity battery?

[MTM98290]

We have a off grid system that occassionally runs out of sun in winter. After a week or more of low production they system has shut down for a short time.

We use a cheap 450va APC ups to keep internet connected for a while after the system goes offline. This works well and does give me the ability to see that the system is offline. This works just fine to feed my 10w internet draw for a while.

I have seen bigger ups like the 1500w versions which would be 3.33x more capacity in theory, but that still doesn't amount to enough capacity to ride out the darkest periods.

Are there any low cost ups options that I am missing? I will be adding 1k more in panels as soon as I can, but that likely won't be finished before the weakest solar weeks come.

We were hoping to have the auto start generator setup to fix the issue but that also may not happen soon enough either. Adding batteries is not an option at this point.

Adding a simple ups type system could be a great stopgap measure for this winter.
I have seen inverters that plug into the wall and will switch to battery power when power turns off. Does anybody have a recommendation for an inexpensive small inverter of this type? I am picturing hooking it to a gel battery as will not see many cycles and will not called on more than 2-4 times in winter. The inverter would not need to be pure sinewave as it just feeds 2 ac-dc converters that use a total of 240w a day.

I would likely just use a 12v system for this as I don't want or need more than one battery.

Thanks for any ideas or advice.

 

[SamDeleted]

I have seen bigger ups like the 1500w versions which would be 3.33x more capacity in theory, but that still doesn't amount to enough capacity to ride out the darkest periods.

Have you considered just adding extra battery capacity to your UPSs ?

If you're handy with stuff its a pretty simple job

, small UPS's are normally either 12v or 24v , all you have to do is cut/splice into the cables and wire in bigger separate gel batteries , not hard at all


All it would cost is the price of a few cheap gel batteries and a little bit of cable

 

[SamDeleted]

feeds 2 ac-dc converters that use a total of 240wH a day

240watt/h ÷ 12v = 20amp/h

So you need about 20ah worth of 12v gel battery for each day you'd like to have back up power for

A 55ah(660w) gel battery would be plenty

 

[MTM98290]

240watt/h ÷ 12v = 20amp/h

So you need about 20ah worth of 12v gel battery for each day you'd like to have back up power for

A 55ah(660w) gel battery would be plenty

Yes you are correct 240watt/hour a day.

The charger built in to the ups charges at about 20watts. Will 20w of charging charge a big 12v battery without burning up?

It seems that these parts may only be capable of the short term intermittent use that the small built in battery requires, or maybe I am overthinking it. APC calls the unit sealed but I'm pretty sure it has recessed screws on the bottom.

 

[PunchySunshine]

It's older, but I love this guy:

 

[Solarcabin Channel]

Most of the newer power stations have UPS capability.

 

[MTM98290]

Most of the newer power stations have UPS capability.

When you say power station do you mean like an ecoflow? Those sort of solutions are nice but not in my budget. I am thinking more like an AGM batt on a ups inverter or external to my current ups.

 

[Shimmy]

I would strongly recommend inventorying your equipment and its power supply configurations. For a ~10W load, if you can keep it simple with DC only life will be much better than using a standard AC ups. A 12V/100Ah battery might run your system for days. You can just put a charger with a timer to run a few hours every day, and disable it on cloudier days.

 

[MTM98290]

It's older, but I love this guy:

That is a neat project, but I could spend less time and money and have a generator set up before I could get all of the necessary items for such a build. 7s9p at 1900mah would be roughly 13.3 ah at 27V?

 

[Shimmy]

When you say power station do you mean like an ecoflow? Those sort of solutions are nice but not in my budget. I am thinking more like an AGM batt on an ups inverter or external to my current ups.

I'm an engineer and wanted the same thing to work because it is completely logical for your use case (and mine). It can be done, but just going for regulated outputs via DC-DC converters is so much less stressful. The idle consumption of the APC UPSs are also a lot more than I would have expected.

 

[MTM98290]

I would strongly recommend inventorying your equipment and its power supply configurations. For a ~10W load, if you can keep it simple with DC only life will be much better than using a standard AC ups. A 12V/100Ah battery might run your system for days. You can just put a charger with a timer to run a few hours every day, and disable it on cloudier days.

The required POE injector is 24V the router is 5v. I would either need to boost convert 12V to 24 or use a 24v system. 5v is easy.

I could plug a battery tender into a wifi switch plug which is hooked to the battery. Then boost convert to 24v for poe and 5v for router. Seems bulletproof if the trickle charger won't mind 10w being pulled while it is hooked up.

 

[Solarcabin Channel]

When you say power station do you mean like an ecoflow? Those sort of solutions are nice but not in my budget. I am thinking more like an AGM batt on a ups inverter or external to my current ups.

What is your budget and I will look around?

 

[MTM98290]

I'm an engineer and wanted the same thing to work because it is completely logical for your use case (and mine). It can be done, but just going for regulated outputs via DC-DC converters is so much less stressful. The idle consumption of the APC UPSs are also a lot more than I would have expected.

do you have an Idea how much idle consumption? This does make sense because when I did the math on the battery capacity and how long it should keep things going it looked as though I should get more on time than it provides in actual use.

Can I just use cheap finned aluminum converters from amazon and have an accurate enough regulation?

Could I use the Growatt dry contact to kick on the trickle charger above a certain voltage? I think it can be configured that way but I would have to read through the manual again.

If I can use dry contact for this I could use a Shelly 2 wifi module to kick on the trickle charger and also be able to control it when the voltage is high enough to allow it.

 

[MTM98290]

What is your budget and I will look around?

Currently my budget is very low. The reason is that if I surpass about $200 I might as well just buy what I need to get the backup generator in place. I have the generator and propane tank. I would need to bury wire and connect to AC input on Growatt. We get lots of snow and i would need to build a structure to house the generator as it is portable and must be secured and out of the weather. I can buy a jobsite tool chest and add ventilation and build a small pitched roof. Boxes of this size are about $700 new so I need to find a used one.

 

[Solarcabin Channel]

Currently my budget is very low. The reason is that if I surpass about $200 I might as well just buy what I need to get the backup generator in place. I have the generator and propane tank. I would need to bury wire and connect to AC input on Growatt. We get lots of snow and i would need to build a structure to house the generator as it is portable and must be secured and out of the weather. I can buy a jobsite tool chest and add ventilation and build a small pitched roof. Boxes of this size are about $700 new so I need to find a used one.

What exactly do you need to run off the UPS and how many watts total?

 

[SamDeleted]

The charger built in to the ups charges at about 20watts. Will 20w of charging charge a big 12v battery without burning up?

It's a good question !

I have done it many times before, it has never been an issue . It was an issue with old fashioned chargers, if hooked up to too larger battery, the big battery would demand more than the charger was designed to output , and because the charger has no current limits it would 'overload' and burn out.... It is not an issue with a ups , they will only charge at the rate they are happy with



The only problem is that the slow charge rate is not great for your gel batteries , this will result in reduced lifespan - not a huge concern if you are only cycling 4/5 times a year


This could be solved by an additional small external 12v charger used to supplement up to a suitable charge rate

 

[SamDeleted]

I'm an engineer and wanted the same thing to work because it is completely logical for your use case (and mine). It can be done, but just going for regulated outputs via DC-DC converters is so much less stressful. The idle consumption of the APC UPSs are also a lot more than I would have expected.

Yea good point , OPs internet router is DC , (12v most probably) , he could run it directly off DC from a battery ,

And then just continuously charge the battery while AC power is available

Essentially making a simple seamless DC ups

 

[Shimmy]

The required POE injector is 24V the router is 5v. I would either need to boost convert 12V to 24 or use a 24v system. 5v is easy.

What router? Most POE routers have an alternate power method.

My personal challenge is that I have a 48-port POE router that covers access points, cameras, and other stuff... and doing a 48V supply has issues. (Ubiquiti USW-48-Pro) I also have a few other devices that are a little tricky to work with, along with about 400W total average power consumption.

 

[MTM98290]

Yea good point , OPs internet router is DC , (12v most probably) , he could run it directly off DC from a battery ,

And then just continuously charge the battery while AC power is available

Essentially making a simple seamless DC ups

Router is 5v usb powered. Very easy to get that. POE for internet reciever is 24v.

 

[Shimmy]

do you have an Idea how much idle consumption?

Hard to say, but somewhere between 10-70W average for mine.

Can I just use cheap finned aluminum converters from amazon and have an accurate enough regulation?

No direct experience, but others have done 24:12V converters and @Will Prowse has some videos on them. Something for 10-20W should be easy.

Could I use the Growatt dry contact to kick on the trickle charger above a certain voltage? I think it can be configured that way but I would have to read through the manual again.

If I can use dry contact for this I could use a Shelly 2 wifi module to kick on the trickle charger and also be able to control it when the voltage is high enough to allow it.

I would go the Shelly route personally; mix in scheduled charging and state of the system.