Project to charge an old server UPS using a Solar Panel - Possible?

[TwistedHelixis]

I have a few old Dell UPS and wondered if it would be possible to charge them using a Solar Panel.

 

Could I get a Solar panel, a good 12v to 240v inverter and then plug that in the AC input on the APC?

[hallb15]

In a word, no.

 

The batteries in the UPS are DC. The UPS takes the AC mains input and rectifies it to DC to charge the batteries. So you would be trying to convert DC from the solar panel to AC to DC which is a very inefficient way of doing things and you would need a very large solar panel to get anything usable out of it.

You could connect the solar panel directly to the DC side of the rectifier built into the UPS, but that would require some electronics knowledge and detailed schematics of the Dell UPS. An interesting project though...

[PotNoodleTech]

Not without literally ripping it apart and rewring it all.

 

The UPS is designed to charge from 240v only. Trying to lob 12v into it somewhere is only going to end in a fire.

[mavhc]

Reuse the individual cells from the batteries in a solar panel charger perhaps

[synaesthesia]

Depending on what the end use is, it's likely to be far better & more efficient grabbing a load of 18650 batteries from laptops to make a similar sized & slightly more powerful/usable battery pack.

[mavhc]

Weirdly if you want to buy li-ion batteries the cheapest way is to get one that's on wheels.

 

Anyway, https://www.photonicuniverse.com/en/how-to-choose/solar-charge-controller/

[bald_pig]

What's the end goal? It would be fairly trivial to charge the batteries directly from the solar panel, but you would need a very bright day, as you actually need about 14v to charge a 12v lead acid battery.

 

I wouldn't bother with an inverter, as @hallb15 said, the losses from inverting 12v dc to 240v ac, only to go back to 12v dc is wasteful.

 

Of course, I'd only recommend doing this if you are competent with electronics, as boiled or shorted batteries are not fun!

[IrritableTech]

My shed runs on eight old UPS batteries (and 140 lithium ion 18650s) all charged by solar. I use them with invertors for a few items but generally try to plug in low voltage things to cut down on wastage.

 

You don't need a bright day to charge batteries, just the right amount of solar panels configured to output the right voltage, pointing in the right direction. Take a look at my system on Jan 1st this year... 100 watts of panels only producing 30watts at their peak was enough to float 136 amp hours of lead acid batteries.

 

 

Like @bald_pig asks - what is the idea?

[bald_pig]

My shed runs on eight old UPS batteries (and 140 lithium ion 18650s) all charged by solar. I use them with invertors for a few items but generally try to plug in low voltage things to cut down on wastage.

 

You don't need a bright day to charge batteries, just the right amount of solar panels configured to output the right voltage, pointing in the right direction. Take a look at my system on Jan 1st this year... 100 watts of panels only producing 30watts at their peak was enough to float 136 amp hours of lead acid batteries.

 

 

Like @bald_pig asks - what is the idea?

I know you don't need a bright day with the right setup, I was going with the OP saying a 12v solar panel, with multiple it would be easy but I get the impression this is meant to be a cheap/free project

[TwistedHelixis]

I know you don't need a bright day with the right setup, I was going with the OP saying a 12v solar panel, with multiple it would be easy but I get the impression this is meant to be a cheap/free project

 

Does not need to be cheap or free but I don't want to get pre built setup, when I am sure it must be possible to build this myself.

 

What's the end goal?

I have two end goals.

 

1. I would like to be able to power a fridge for a short while in the event of a zombie apocalypse :0). I would like the option to be able to power either a 240v fridge or a 12v camping fridge.

 

2. To see if I can and to learn how it would be done.

[IrritableTech]

Does not need to be cheap or free but I don't want to get pre built setup, when I am sure it must be possible to build this myself.

 

 

I have two end goals.

 

1. I would like to be able to power a fridge for a short while in the event of a zombie apocalypse :0). I would like the option to be able to power either a 240v fridge or a 12v camping fridge.

 

2. To see if I can and to learn how it would be done.

 

Ok. Your UPS is probably a modified sine wave inverter, and sadly a fridge compressor won’t run very well or efficiently on MSW. So straight away the UPS might not be the best solution as is.

 

You could probably charge the batteries within it without any real issues, but you’d be best off solar charging the batteries to a lower level to ensure you don’t fry the inbuilt charger.

 

Most UPS’s I’ve used are setup as 24 volt systems - two batteries in series. This is because it’s generally a little more efficient to boost and invert higher dc voltages (boosting ten times 24-240 rather than twenty times 12-240).

 

So as you can tell I’m not sure the UPS is the best solution - unless that’s all you have.

 

How big is your solar panel? What is it’s open circuit voltage (the voltage under sun when no load is connected), what is the maximum power point (the voltage where it actually can produce its full rated power) and what is it’s closed circuit current? You’ll need to consider these to buy a suitable charge controller.

 

Buy some fuses. Fuse your battery and your loads. Fuses are to protect your wire, not your appliance so rate them accordingly.

 

A twelve volt system with a small solar panel will keep a camping fridge running for a while in the summer. Then once your comfortable you can expand ;-)

[southhamster]

Does not need to be cheap or free but I don't want to get pre built setup, when I am sure it must be possible to build this myself.

 

 

I have two end goals.

 

1. I would like to be able to power a fridge for a short while in the event of a zombie apocalypse :0). I would like the option to be able to power either a 240v fridge or a 12v camping fridge.

 

2. To see if I can and to learn how it would be done.

Unfortunately fridges are a difficult one. Very high start current and over 24 hours will use quite a lot of power. Some with electronic controls may not be happy running from a (cheap) stepped sine wave inverter. Pure sine wave inverters with a decent transient capacity like Victron are expensive. A smaller peltier 12 volt fridge might be more practical but they aren't terribly efficient either. Remember lead acid batteries can only use 50-80% of rated capacity.

[mavhc]

Look into the camping/boating power scene, they mostly have this figured out.