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Battery Back-Up to freezers


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Computer/ server UPS?  (will be expensive.) 

When I kept marine fish I allways had a petrol generator around in case of emergency but it was so useful I kept it once the fish had gone.

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Living in the sticks and having fairly regular power cuts, we have a small Honda petrol generator - life saver, if a bit of an investment initially.

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1 hour ago, Scrumbag said:

Hi folks,

Question, has anyone got a solution for battery back up for Freezers?

Best wishes,

Scrummy

Generator is a simple solution but auto-start is a complexity so if you're not at home when the power cuts you could have no benefit without.  If you do want battery back-up have a look at marine inverters,  typical set-up in boat uses around 200-300 Amp-hour of leisure batteries and an inverter (Mastervolt and Victron are the best but expensive,  Sterling Power are adequate).  Auto switch over to batteries is easy to achieve (and battery charging is simple when the mains is on.

https://www.victronenergy.com/inverters-chargers

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How much power does you freezer consume (i.e the watts on the rating plate), and how long would you anticipate it needing to run on batteries?

Also is it a chest freezer or an upright because chest freezers keep their temperature longer because the cold air stays inside the box whereas with an upright, every time the door is opened the cold air 

Only then can you work out what size of battery pack you'll need

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Sorry folks, should have given a bit of context.

Our freezers are in a garage which has a communal electricity supply for the block. Occasionally the circuit breaker for the Garage gets tripped and it doesn't get reset until the estate manager / porter does their rounds on a Monday morning. So even a few extra hours of power would get the freezers through a weekend and less risk of loss.

So, thoughts welcome.

Scrummy 

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35 minutes ago, Scrumbag said:

Sorry folks, should have given a bit of context.

Our freezers are in a garage which has a communal electricity supply for the block. Occasionally the circuit breaker for the Garage gets tripped and it doesn't get reset until the estate manager / porter does their rounds on a Monday morning. So even a few extra hours of power would get the freezers through a weekend and less risk of loss.

So, thoughts welcome.

Scrummy 

doesn't sound like a generator is an option.   What's the current consumption from the rating plate(s) ?  The best way to work out the energy used would be to get one of those cheap plug-in energy monitors (https://www.amazon.co.uk/Decdeal-Electricity-Consumption-Analyzer-AC230V-250V/dp/B07QZYPQ4M/ref=sr_1_9?crid=36UT71OG4BIY8&dchild=1&keywords=energy+monitor&qid=1627893024&sprefix=energy+monitoring%2Caps%2C165&sr=8-9)   and see what the typical drain is over a weekend.  From that it's straight forward to work out the battery capacity you require.

A good time to do it would be a warm summer's day - most draw on power

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Basic ups system  . Two sockets needed one for charging battery system and one to power the fridge and relay . Big enough relay contacts rated for amps draw of fridge . Wiring shows relay de- energised as in 240 volt fail  . 240 volts come back on and relay energises and breaks dc power to inverter and the output of the inverter . Charger now tops up the battery. Should be able to get gear from caravan shop or electronic catalogue RS COMPONENTS 

3B281094-38B6-47EC-A256-9B35577C8FFF.jpeg

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Richiew, do you have any formal qualifications for promoting that home-brew solution?  It's unsafe.

  • no fusing
  • neutral link between inverter & incoming mains may well trip the RCD at the dis-board
  • Incorrect choice of relay, in event of failure, could result in a back-feed of 240V AC exported out of the premises putting persons at risk of death
  • there are regulations regarding auto switching systems connected to incoming mains services

Please don't use this drawing.   I am a fully qualified electrical engineer (not a sparky),  this is not safe.

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It’s only for basic understanding . Fusing in the plug s not good enough ?? . Of course real made equipment has lots of safety devices solid state switches fly back current diodes thyristors etc  . Buy a purpose made bit of kit . 
Could run fridge off the inverter fed from batteries and 240 v charger as a straight through unit then don’t need relay and no problem s with mixing supplies?? How’s that idea 

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56 minutes ago, Richiew said:

It’s only for basic understanding . Fusing in the plug s not good enough ?? . Of course real made equipment has lots of safety devices solid state switches fly back current diodes thyristors etc  . Buy a purpose made bit of kit . 
Could run fridge off the inverter fed from batteries and 240 v charger as a straight through unit then don’t need relay and no problem s with mixing supplies?? How’s that idea 

No mate it isn't at all.   Purpose made kit meets necessary design criteria for circuit interruption and protection.

Your 2nd suggestion could work and could be safe but would be quite inefficient.  There are purpose made inverter/chargers that can do, in principle, what you suggest but this can be an expensive solution.

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