Discuss 240v to 12v, Charger + Inverter idea => feedback weclome in the DIY Electrical Forum area at ElectriciansForums.net

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mascip

DIY
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60
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London
Hi there,

for a friend's boat, he has constant access to 240v shore power (and a galvanic isolator), but still wants batteries for whenever shore power stops working, or if he wants to go and cruise for a day or two. He needs a charger to keep the batteries topped up, and an inverter for getting 240v power from the batteries.

There are several solutions out there, but the most important thing is that inverter and shore power must never be connected together, which would kill the inverter. There are a few possible solutions out there, including:
- inverter with "automatic pass through" when shore power is connected
- combi charger-inverter, which handles this best but it's bulky, and if it fails you lose both charger and inverter
- charger to batteries, and then inverter connected to batteries only. Then everything connected on the inverter (disadvantage: if using more power than the charger can charge, the batteries could go flat)

In my friend's case, he already has an inverter but it doesn't do "automatic pass through". My idea for him is simple:

A two way switch which either takes power from the shore, or from the inverter, and feeds it to the fuse box. This would ensure that the sockets always get power from either power source, and that inverter and shore power never get connected together. And the charger would be connected separately, from shore power.


Feedback would be very nice. Are there disadvantages to this approach? Caveats? A better idea?
 

amlu

Electrician's Arms
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1,407
Location
wild east london
Hi there,
A two way switch which either takes power from the shore, or from the inverter, and feeds it to the fuse box. This would ensure that the sockets always get power from either power source, and that inverter and shore power never get connected together. And the charger would be connected separately, from shore power.

Feedback would be very nice. Are there disadvantages to this approach? Caveats? A better idea?
this arrangement is commonly used when there is a generator as a backup power. There are proper switches too:
https://www.tlc-direct.co.uk/Main_Index/Distribution_and_Switchgear_Index/Change_Over_Switches/index.html

another idea will be a big 12v charger/power supply on the shore, with big 12v cable going to the boat, feeding the batteries and powering the inverter...
 
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