Switching from leisure battery dc supply to a 240 v ac- 12v dc power supply to feed a load ( fridge )

[osman]

Ok here’s a question can anybody tell me why I can or cannot connect the negative supply of my 12 v power supply to my fridge to the vans general negative .
to make sense of this to anyone reading hopefully !!!
i basically want to install a switch that switches over my fridge from my leisure battery to its own power supply . Instead of laboriously unplugging it and hooking it up to its power supply everytime I’m hooked up to 240 v … here’s a diagram of the switch circuit .

 

[Dellmassive]

yes . . . that will work ok.


+++

or you can just hard wire your PSU/Charger direct to the leisure battery.

that way on battery the fridge will run.

then when on EHU, the fridge will be powered from the charger ., . . . and the battery will also be charged at the same time.


so . . . is your 240v 12vdc fridge PSU? ( is it a PSU or charger? )



++++++++++++


example:

just wire this up and plug it in.

12V VICTRON ENERGY 15A 7 STAGE SMART BATTERY CHARGER WITH BLUETOOTH CONTROL - Alpha Batteries

Smart 7 Stage Bluetooth Control Charger by Victron

www.alpha-batteries.co.uk

 

[Dellmassive]

if you go for your switch idea as per your OP. . .


you need a 3way switch with a contact rating over the fridge power draw.


so what fridge and what's the power?

++++++++

example:


on-off-on

dpdt

https://amzn.to/3HRUOZr

you can use both sides of the switch to increase the power flow over the switch to stop heating.



..

 

[osman]

It’s a regular 240 v power supply with a 14.7 v out the fridge can pull 5 amps
this is the switch I've got
On off on

 

[Pete C]

As Dell says, you can just hardwire both to the load, that’s what we have done. No switching required.
As long as your power supply is a battery charger.

Pete

 

[Dellmassive]

Got a pic of the power supply?

As Pete says if it's a plain PSU you will have to use the switch method.

If you swap the PSU for charger....then fit and forget with no switching.

(Appart from switching the fridge off when not needed to stop it draining the battery flat.)

 

[osman]

Ok I think I need to explain that I already have the fridge wired to my leisure system … eg when I’m connected to 240 it’s being powered by the charger and the battery is getting charged . Maybe what I’m doing is pointless . But I’m trying to separate my fridge from the whole leisure system when I’m on 240 . I can all ready do this simply unplugging and re plugging … I just thought a switch would be cool.
i suppose I’m thînking of allowing my charging system to be free from the fridge load whilst I’m on 240 hu now if that’s nonsensical so be it .. maybe it’s stupid .. it just made sense to me to have anything that can run on its own 240 supply run on it instead of using the charging system .

 

[Salty Spuds]

As Dell says, you can just hardwire both to the load, that’s what we have done. No switching required.
As long as your power supply is a battery charger.

Pete

Exactly wot he said^^^^^^KISS!

 

[T6Jay]

I just thought a switch would be cool

'Desire is the root of all suffering' - The Buddha

 

[osman]

'Desire is the root of all suffering' - The Buddha

Agreed

 

[Salty Spuds]

… I just thought a switch would be cool.

Until you forget to switch it over, and then your beer isn’t & your milk is yogurt.
Don’t overthink it.

 

[osman]

Ok I’ve just seen an old post from 2020 where I asked the question regarding fridge on its own power supply or not whilst hooked up and dell replied that it would reduce the wear and tear on the 12 v charging system … this is my motivation I guess .. also if I’m just trying to get my leisure battery nice and topped up and healthy whilst hooked up to 240 ….why not give the charging system a break from that damn fridge ? Particularly on a very hot day inside a hot van !!
Am I mad ? why does this make sense to me …

 

[Dellmassive]

@osman

a few Q&A`s may help to clarify things. . . . .


++++++++++

when your on EHU . . . how does the leisure battery get charged? - PMS?.. charger? .. nothing?

do you have a dc-dc charger? for engine charging of the LB.

do you have a way of charging the starter ( appart from the engine?)

 

[osman]

@osman

a few Q&A`s may help to clarify things. . . . .


++++++++++

when your on EHU . . . how does the leisure battery get charged? - PMS?.. charger? .. nothing?

do you have a dc-dc charger? for engine charging of the LB.

do you have a way of charging the starter ( appart from the engine?)

On ehu i have a charger
Yes dc dc charger so lb gets charged by engine.
No the starter battery only charges via engine .

So basically unless I’m doing a good run regularly the leisure battery is often getting flat eg I’m at the local beach a short drive away …

So I have some stuff in fridge … I want to charge up the leisure battery but I don’t want the fridge gobbling up the power whilst I’m charging …. So I run the fridge off it’s own power supply temporarily .
Voilà … does that make sense ?
I won’t start on about solar yet … lol

 

[Dellmassive]

Ok.

Any idea on what size the EHU charger is?

If you had a big enough EHU battery charger I could do both....

Assuming if the fridge is gobling up power then the charger may be under rated nformyou setup. (Ie run all loads plus provide full rate battery charging)

Either way..... If you want to fit the switch. That will work. As you indicated above.

Post some pics if you can.

 

[osman]

Ok.

Any idea on what size the EHU charger is?

If you had a big enough EHU battery charger I could do both....

Assuming if the fridge is gobling up power then the charger may be under rated nformyou setup. (Ie run all loads plus provide full rate battery charging)

Either way..... If you want to fit the switch. That will work. As you indicated above.

Post some pics if you can.

I’ll post some pics of my finished set up shortly I think what I’m doing should be good for my needs , I don’t think the fridge is taking too much power from the ehu charger I just don’t see the point in having it use it when It has its own supply . It’s unlikely I’ll ever need to move the fridge so the charger can stay in the van .. I just switch back and forth as required .
May not be what most people want but it makes sense to me .

 

[CAB]

On ehu i have a charger
Yes dc dc charger so lb gets charged by engine.
No the starter battery only charges via engine .

So basically unless I’m doing a good run regularly the leisure battery is often getting flat eg I’m at the local beach a short drive away …

So I have some stuff in fridge … I want to charge up the leisure battery but I don’t want the fridge gobbling up the power whilst I’m charging …. So I run the fridge off it’s own power supply temporarily .
Voilà … does that make sense ?
I won’t start on about solar yet … lol

Sorry if this sounds like a daft question, but,

Fridge's own supply?

Does it have its own battery?

If you mean a separate charger to run it, isn't that just run off the 240v anyway?

So aren't you taking the same amount of power, just bypassing the battery?

If there is a separate battery then I can see the argument, if not then aren't you just shuffling everything around?

 

[Alster]

I think he’s trying to reduce the load on the ehu charger by giving the fridge it’s own 12v power supply via a 240v psu. @osman feel free to jump in if I’m wrong (it has been known!)

 

[osman]

I think he’s trying to reduce the load on the ehu charger by giving the fridge it’s own 12v power supply via a 240v psu. @osman feel free to jump in if I’m wrong (it has been known!)

Bang on !

 

[osman]

Sorry if this sounds like a daft question, but,

Fridge's own supply?

Does it have its own battery?

If you mean a separate charger to run it, isn't that just run off the 240v anyway?

So aren't you taking the same amount of power, just bypassing the battery?

If there is a separate battery then I can see the argument, if not then aren't you just shuffling everything around?

Yes but I’m bypassing the charger so it can concentrate on doing what I want it do