Inverter Efficiency

[DBK]

While you guys are chatting this through ......Therefore an inverter utilised only to charge 36v battery for my clip on handcycle to wheelchair battery would need to be ..........w? We have 2 x 90ah batteries and 150w of solar.

Have a look at the charger spec, it may mention a current figure*. Multiply this by 36 then double the result to be safe, quadruple to be even safer. At a guess a 500W pure sine inverter will probably be sufficient.

* Look for the output spec, something like 36V 2.5A.

 

[autorouter]

If you have one single load like the fridge that is on 24/7, then it would be worth getting a small inverter dedicated just for that purpose. You can get a very efficient 150 watt PSW inverter , and since it will be drawing less than 10 amps it can be plugged into a cigarette-lighter socket, so no wiring surgery required. Once you're happy with it, you can wire it in permanently, of course, for better reliability.

I bought mine from Conrad in Germany (a shop like Maplins), it is beer-can size and shape. Can't find it now, but something like this would do.

Buy Dometic Group Inverter SinePower DSP 212 150 W 12 V DC - 230 V AC | Conrad Electronic

Top %brandid% Selection | Order easily now: Dometic Group Inverter SinePower DSP 212 150 W 12 V DC - 230 V AC | Fast delivery | Reasonable prices

www.conrad.com

 

[Neil Bedwin]

While you guys are chatting this through ......Therefore an inverter utilised only to charge 36v battery for my clip on handcycle to wheelchair battery would need to be ..........w? We have 2 x 90ah batteries and 150w of solar.

I charged two eBike batteries (15ah and 13ah @ 36v) at the same time off a 600watt inverter. If I do one at a time the cooling fan in the inverter does not even come on.

 

[Misterg]

Victron and Sterling (and possibly others) make inverters with a sleep or eco mode where they draw very little power in standby and automatically kick into action when a load appears on the 240V side. There seem to have been mixed experiences as to whether the eco mode will work with domestic fridges (whether the inverter kicks in before the fridge decides it has a power fault).

Others have found that you need a very well designed inverter of ~1kW capacity to deal with the startup load of the compressor on even small domestic fridges. The Victron inverters seem to deal with startup loads better than most, and people report success using the Victron 12/500 inverter with the ultra-efficient A++ fridges like this:

Amazon product ASIN B01MY162BX
but 800w or 1kw inverters seem to be more typical. Many have discovered that cheaper inverters from ebay/amazon/etc. that appear to be similarly rated simply don't work with fridges.

Do your research before buying - absolutely loads of information here and here

 

[Richard n Ann]

I would look at rewiring the fridge thermostat to switch the inverter on and off directly, probably through a relay or contactor. That would save a lot of stand by power ?

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[hilldweller]

I would look at rewiring the fridge thermostat to switch the inverter on and off directly, probably through a relay or contactor. That would save a lot of stand by power ?

Thereby converting a 240V fridge to a 12V fridge. Nice bit of lateral thinking there. Totally compartmentalised cooling solution.

 

[StitchesnFluff]

Thank you all for your help . 600w pure sine appears the answer.

 

[Servo]

As tested ?

 

[HandyAndy]

This has just popped up on my YouTube feed... Interesting but also in depth and on topic for this discussion

 

[Wissel]

I have the same 240v fridge in my van as in the above post, plus had the same 12/500 Victron inverter. It worked great for the months it was running and together, the fridge and inverter used less power than my last Vitrifrigo 12v compressor fridge.

I've since bought a larger inverter, the Victron Phoenix Smart 2000VA (1600w) with the intention of having it on all the time. But like you I'm a little concerned about the efficiency at low draw.

I should have the new electrics (bit of a rebuild going on at the mo) and inverter testing within a week (I hope) and as my setup accurately measures the current to and from the battery separately, I should be able to let you know how efficiently it works at different loads. So if you can hold on a week....

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[MANGOFORTH]

I can wait!! Awesome

 

[HandyAndy]

efficiency curves of the victron range are available on the net.

https://www.victronenergy.com/upload/documents/Output-rating-operating-temperature-and-efficiency.pdf

Page 3

 

[Wissel]

efficiency curves of the victron range are available on the net.

https://www.victronenergy.com/upload/documents/Output-rating-operating-temperature-and-efficiency.pdf

Page 3

Don't think that data is available for my one?

Couldn't find it anyway - Victron Phoenix Smart 2000VA

It's a newer model than the ones tested in the PDF you linked too. Hoping it's even more efficient.

 

[Charlie9038]

As a fridge engineer i would not recommend a domestic fridge freezer for a motorhome as they can switch off below 15 degrees ambient temperature. Ok if your above that but when it gets colder here you run the risk of it not working properly. Check out climate class on google most fridges are sn rated these days.