Conflict between Inverter and Charger

[neiloakley]

Boat currently has three batteries, and a charger that runs off the shore power.

If I install a separate inverter, what stops the battery charger sucking power from the inverter to try and charge the battery?

I know I could just turn off the battery charger when I switch over to inverter power, but is there a way of setting everything up so that I can flick my 2 way switch from 'shorepower' to 'inverter' and not need to have to remember to turn off the battery charger too?

Thanks

Neil

 

[sailorman]

dont run the charger off of the inverter will be a start

 

[prv]

is there a way of setting everything up so that I can flick my 2 way switch from 'shorepower' to 'inverter' and not need to have to remember to turn off the battery charger too?

Yes - connect the charger to the shore-power side before the switch!

You might want to do the same with the immersion heater on the hot-water tank.

Pete

 

[duncan99210]

Or just have the inverter power a single separate socket for those occassions when you need to use it.

 

[Mistroma]

Wire so that inverter can't run the charger as already mentioned. I take the feed supplying the mains sockets and run it through a switch to select either shore power or inverter. The switch is break before make and so it avoids ever feeding other kit (e.g. charger, water heater etc.) from the inverter.

This obviously still leaves the possibility of plugging in too high a load when getting AC via the inverter. Trying to boil a kettle and run an electric fire would be a bad idea. I simply manage this by knowing which items I can use without overloading the inverter. Small chargers, TV, laptops are all OK (though I actually have 12V feed for these, but sometimes use the inverter).

Not ideal but not too different from watching what you use on shore power. Boiling a kettle, running immersion heater, microwaving and having a 2kW fan heater on at the same time would be too much for most shore power systems. Just a matter of knowing the limit and keeping well below it.

 

[neiloakley]

dont run the charger off of the inverter will be a start

The inverter output will feed into the 240v bus. I'm not plugging the charger into the inverter directly

Also, I can't wire the charger before the 240v switch otherwise it wouldn't be going through the circuit breakers and reliant on the fuse in the plug!

 

[sailorman]

I have a single socket from my inverter, to only feed what is plugged into that socket

 

[neiloakley]

I'd prefer to power the entire 240v bus soni'm not restricted to where I can plug in

 

[rosssavage]

Just in the process of installing a shore/inverter/generator auto changeover system. I wanted it wired so I couldn't run the charger or water heater off the inverter, but I could run them off shore/generator.

Got a DPDT 240v coil relay. Wire the coil to the inverter output, with the two feeds to charger and heater through the two pole NC contacts. When the inverter is on, it powers the relay coil, interrupting the supply to the charger/heater.

I can now leave the inverter always on and charger/heater always on, knowing they can only be fed from shore/gennie.

 

[Mistroma]

I'd prefer to power the entire 240v bus soni'm not restricted to where I can plug in

Wanting to power the entire 240V bus is your problem as that means it will be possible to power up the charger when on the inverter.

You don't want to feed everything from the inverter and this means that you need to find the point in your 240V system where the sockets get their feed. Once you know where that is, it is pretty easy to put in a switch to swap between normal shore feed and inverter feed positions. You could use a relay system as described elsewhere to provide an automatic switchover but a manual system is simple and cheap. I use a manual system feed all 11 mains sockets on-board and it works well.

I'm assuming you only want to power 240V sockets, not other kit such as water heater and 12V charger. This is a pretty safe bet given the problems you'd have trying to power either of these from an inverter.

 

[neiloakley]

I'm assuming you only want to power 240V sockets, not other kit such as water heater and 12V charger. This is a pretty safe bet given the problems you'd have trying to power either of these from an inverter.

That's exactly the point of my post.

The battery charger is powered from the sockets. So if the inventor puts power into the sockets it's going to go to the charger. My question is how do I stop that. I will look at a DPDT relay.

 

[Mistroma]

That's exactly the point of my post.

The battery charger is powered from the sockets. So if the inventor puts power into the sockets it's going to go to the charger. My question is how do I stop that. I will look at a DPDT relay.

If you mean that your charger is plugged into a socket then you should unplug it before switching the inverter on. A DPDT relay won't help much in this case. You'd need an in-line relay box taking feed from the inverter output to the relay so that it disabled flow from the plug if the inverter was on. A bit clunky and simpler not to use a plug for the charger and wire it permanently instead.

If you just mean that it is on the same circuit then everything I've said still applies, just find a point where you can split the feed. Power to charger on once side and power to socket on the other and then install the switch or DPDT relay on that side. The relay is just another type of switch. If you can install a DPDT relay then you can install a manual make before break switch in the same manner. The relay is simply a more expensive automated method of switching.

 

[Lon nan Gruagach]

I'd prefer to power the entire 240v bus soni'm not restricted to where I can plug in

That is just like saying "get out of that without moving", you have almost painted yourself into a corner.
There is, however a few solutions:
1 install a dual bus consumer unit. one bus is shore power only and feeds the charger, the other bus is switched shore power and inverter.
2 use a 4 pole changeover switch. 2 poles switch the feed to the charger with only the shore power as an option, the other 2 poles switch everything else with shore power and inverter as options.
3 fit a contactor that is energised when there is volts on the shore power feed, this can switch the feed to the charger. yes the contactor coil will be on the unprotected side, but can be in a safe enclosure with its own fuse/ circuit breaker so no extra protection is required.

 

[prv]

Also, I can't wire the charger before the 240v switch otherwise it wouldn't be going through the circuit breakers

Well then wire things so that it does!

If you're not competent to do that, pay someone who is.

Pete

 

[GrahamM376]

That's exactly the point of my post.

The battery charger is powered from the sockets. So if the inventor puts power into the sockets it's going to go to the charger. My question is how do I stop that. I will look at a DPDT relay.

Why not just mount a switch at the side of the socket to isolate the charger?

 

[Richard10002]

The inverter output will feed into the 240v bus. I'm not plugging the charger into the inverter directly

Also, I can't wire the charger before the 240v switch otherwise it wouldn't be going through the circuit breakers and reliant on the fuse in the plug!

I have 2 sets of circuit breakers, (garage consumer units). The charger is fed from the first unit, the inverter feeds the second unit, the second unit feeds the boat 240v stuff).

It's actually more complicated than that because I have a charger and an inverter charger, but the principle is similar. My inverter charger cannot feed the backup charger.