Battery charging.

I have a yacht which has a US 110vac distribution system consiting of a Freedom 20 inverter/charger, seperate battery charger and a few outlets.
What is the best way to charge my batterys from a UK 240vac shore supply?

 

The best (and most simple) way to handle 240VAC shore power with a 110VAC setup is to use an isolation transformer:



Specifically, you want to pick one that has inputs of both 120 and 240 Volts, such as the following:

Isolation Transformer at Defender

 

So if I put 240vac into the isolation transformer the output will be 110vac, what happens about the frequency?

 

The frequency is not converted by an isolation transformer, unfortunately.

This is the drawback of your situation. However any resistive loads, like a toaster or hot water heater or incandescent light bulb will work just fine any any frequency. Other loads, such as AC motors, specialty electronics may not. For instance, the clock on your microwave may run slow at 50Hz if it's a 110VAC/60Hz microwave.

Your charger will handle the 50HZ power just fine. It will accept input frequencies from 45-75Hz. See the specs on the Freedom 20 here:

http://www.pyacht.com/heart-freedom-20.htm

The thing is, you have to really take a holistic look at your entire electrical system and planned usage to come up with a plan. An electrical system isn't something to add parts to ad hoc unless you are pretty sure of your goals and requirements. (an example of doing this incorrectly was Abby Sunderland's boat, the girl from CA who failed her circumnavigation attempt, largely due to her design team)

Assuming you want to have 110VAC power in the outlets, run the Freedom 20 to charge batteries and that is all, the isolation transformer is the way to go, being careful of your various electrical items that they can handle the lower frequency.

For instance... the laptop I'm writing from now has a power supply that can handle 110VAC at 50-60Hz. Many things can, like your battery charger.

So... is that all you are trying to do with your electrical system or is there much more? Do you have 110VAC appliances available in the UK? What will you plug into the outlets?

Are you from the UK? Do you plan to stay in the UK/EU (out of Caribbean and USA?) If so, you may want to simply change the entire boat over to 240VAC/50Hz. The wiring is already double the size you need and should have 3 conductors, if modern.

 

The boat will be cruising around the UK and the returning to the US, could I use something like this http://www.justgenerators.co.uk/pages/product18.htm
I would have to change the plugs to fit into the shore supplly and the socket on the boat.

 

If you are only cruising the UK, your solution looks good to me, except you need to find a much bigger one if you want to run your battery charger off it.

Here is another site with the Freedom 20's specs:

http://www.donrowe.com/inverters/freedom_inverter_charger.html


According to these specs, your charger (on bulk charge stage) will require 21 Amps at 110 VAC, or 2,310 Watts.

The power tool transformer you linked to would catch on fire immediately, since it can only put out 330 Watts.

Assuming you might want to do things other than charge the battery at the same time, you should really be getting something that can convert the voltages at 3-4KW (3000 to 4000 Watts)

If you can get all of the 10KVA through a single outlet to your boat, from this model, it might do the trick:

http://www.justgenerators.co.uk/pages/product26.htm

Though... I'm not sure it converts from 240VAC to 110VAC. It isn't clear if it does based on the link. I think the ones I showed in my first reply will work well.

You will have to spend some money if you want to run that charger. You can always re-sell the isolation transformer after your cruise of the UK when you don't need it anymore.

 

So if I use an isolation transformer, I could mount it in a waterproof box with sockets on the outside to plug the shore supply into and the boat into the other I could then stow it when not in use, as space is an issue for permanet mounting.
The boat is equipped with galvanic isolators would there be and issue with introducing a isolation transformer into the curcuit?

Thanks for the help Catbuilder