Sargent PX300 charger power draw query

[Moped]

This is quite a good indication of a setup which maintains the battery but also takes advantage of the 'free' power from the solar....


Screenshot 2023-10-05 at 11-43-44 Monty - VRM Portal by David, on Flickr
Plugged into EHU, but the charger is on float and is drawing nothing as all the power requirements are being met by the Solar.

However .... what you could do to make it even more efficient if you have solar and EHU is have the EHU on a time clock so it only comes on later in the day for a period of time. This would let the solar work harder when it is available. If you have both EHU and Solar you would have a situation where the EHU will start working to keep the battery topped up as soon as it is dusk and maintain that until the solar wakes up, and you would never get the full capablity of the solar during the day (hence why in the screeshot above, all the solar is doing to providing just what is needed as the battery is full.

If you are looking at the cost of the electricity when the charger is active though in the example above, you could be looking at maybe 15 pence a day if you have a compressor fridge? (if you have an Absorption fridge running on AC when laid up, that is more like £1.50 a day just to run the fridge!)


(I could actually set the charger to 'storage' instead of float, which could be better for some - maybe most - setups in a situation where the motorhome is laid up unused, but in my particular config, the storage mode was not suitable)

Don’t you mean have the charger on a time clock?

When on EHU you really want it 24/7 as it runs the fridge and powers the AC sockets for toaster, kettle, microwave, electric oven, and also the heating and more. The 12v use is minimal daytime maybe the water pump only, and the heating pump and fans if cold.

You can however turn the battery charger on and off. If you are on a metered supply I can see that it may be worth turning the charger off daytime when solar is keeping the battery topped up.

However the charging voltage is lower with solar. As soon as you turn the charger on the battery voltage rises so would this not offset some of the potential metered supply savings.

And in any case are you saving only pennies rather than pounds by having the charger on a timer?

And doesn’t the constant switching on and off of the charger (or even the EHU if this was the genuine idea) affect the working life of everything and shortens it before requires a replacement?

Or do the electrics last forever regardless of the number of times they are switched on and off?

 

[wildebus]

Don’t you mean have the charger on a time clock?

It is an option worth looking at. But most CHARGERS are hard-wired and don't have that possibility for timed control. Hence why controlling the supply Into them can be the only way to automatically control their on and off times.

When on EHU you really want it 24/7 as it runs the fridge and powers the AC sockets for toaster, kettle, microwave, electric oven, and also the heating and more. The 12v use is minimal daytime maybe the water pump only, and the heating pump and fans if cold.

If you are using the motorhome, yes. You also list a whole load of things few people have. This is a motorhome or campervan, not a house. How many people have electric ovens, toasters, kettles, etc.? And again, talking about a parked up van, not campsite use.

FYI, when camping, your example of 12V precludes a whole raft of likely devices.... TV for one. 12V compressor Fridge for another, then you have chargers via USB Sockets for phone and tablet charging. they all use 12V which if you have the charger off will drain the battery even if you have EHU in. (Ignoring solar presence, as I said before).

You can however turn the battery charger on and off. If you are on a metered supply I can see that it may be worth turning the charger off daytime when solar is keeping the battery topped up.

I think you are repeating what I said there?
as far as metered supplies, if you are parked at at home, you ARE on a metered supply, are you not? Remember my post was about a van parked up unused.
not a campsite scenario.

However the charging voltage is lower with solar. As soon as you turn the charger on the battery voltage rises so would this not offset some of the potential metered supply savings.

There is an assumption that is totally incorrect. There is no reason whatsoever to state the charging voltage is lower with solar.I don't know if you meant something else, but the statement is given is wrong.

And in any case are you saving only pennies rather than pounds by having the charger on a timer?

As I said, cost of leaving the charger on 24/7 to maintain a parked up van is very little.

And doesn’t the constant switching on and off of the charger (or even the EHU if this was the genuine idea) affect the working life of everything and shortens it before requires a replacement?

Depends what you mean by constant switching on and off? Once or twice a day is not constant. Constant would be turning on and off every 10 seconds maybe.
It would be hard for most installations to have a time on the charger alone as they are hard-wired and controllwd by a physical switch or breaker. If you wanted the charger to be intermittently active, the likelyhood is you would need to cut the supply to it, and the only way for most installations to do that is a time on the EHU into the van. So yes, I did mean that as the 'genuine idea' as the alternative method is not practical for most.
Remember I was talking about a parked-up van that is not being use, not one which is in use on a campsite with EHU, and in that situation there is no need to have EHU 24/7 to run toasters, kettles, ovens, etc.

Or do the electrics last forever regardless of the number of times they are switched on and off?

The answer is yes, no, AND maybe. It all depends on the electrics. There is (was?) a famous lightbulb that has stayed on for well over 100 years. People quote that as an example of how something can last so much longer if it is just left on and not switched off when not needed. I have no doubt that lightbulb would have failed long ago if used in a normal way (when a bulb breaks, it is usually when you turn it on in my experience). But ... how much power has that bulb used when the light was NOT needed? I bet a lot more than the cost of numerous replacements?
Depending on the electronics, the mode of operation varies. Some are designed to be powered only when in use, others all the time. I have some relays in my Motorhome that are designed to outlive me!
In contrast to that lightbulb story, the SSR that drives my fridge power has an MTBF (Mean Time Before Failure) of something in the region of many millions of switching operations. That relay switches maybe 75 times a day at the most. If it switched on and off every single minute it would still on (mean) average last years and years.
The typical electrics in a motorhome is there to be used. End of. Some of it will break, especially if abused, but turning a charger on and off once a day is an irrelevance to its lifespan if it is if any recognisable quality. If I had a concern on how well a charger could cope being turned on and off on a frequent basis, I would be more concerned about leaving that charger left on unattended without supervision in a motorhome (and one reason why there are lots of inverters I would never leave running on their own).

 

[Moped]

think you are repeating what I said there?
as far as metered supplies, if you are parked at at home, you ARE on a metered supply, are you not? Remember my post was about a van parked up unused.
not a campsite scenario.

Slightly confused as where in your post did you say you were parked up on a drive?

It was a campsite EHU scenario with a metered supply as you get in many Spanish sites that I was thinking of.

If the van was indeed laid up on a drive on EHU then I agree different scenario.

And why the constant reference to 12v compressor fridge when most vans these days have 3 way absorption fridges which use around 2kw daily. Well ours does a 133 litre job.That is going to drain a 12v lead acid leisure battery in no time if that is to be relied on without the engine and alternator running. If we turn the engine off and are off grid the fridge stays in 12v mode for 10 minutes before switching to gas.

Maybe older generation vans had these but how far back is this. 15 or 20 years or more? I know our 2003 Bailey caravan had an absorption fridge which is the oldest caravan we owned before transitioning to motorhomes in 2017. We did have a portable compressor fridge which we used in our tenting days but that was an AC job and required hook up but it would also run on gas.

Not convinced a 12v compressor fridge would use just 15p worth of electric unless it was of extremely limited volume which for most off grid (or even on grid) motorhome owners would be useless unless you were prepared to make daily trips to the supermarket. Maybe every 5 or 6 days fine but daily trips! No way.

Maybe is a smaller camper van that can creep under height barriers and fit into a standard car parking space a small fridge is acceptable but not in a difficult to manoeuvre in tight spaces large Motorhome.

 

[wildebus]

Slightly confused as where in your post did you say you were parked up on a drive?

The conversation had drifted from your OP to Jacquies setup

It was a campsite EHU scenario with a metered supply as you get in many Spanish sites that I was thinking of.

If the van was indeed laid up on a drive on EHU then I agree different scenario.

And why the constant reference to 12v compressor fridge when most vans these days have 3 way absorption fridges which use around 2kw daily. Well ours does a 133 litre job.That is going to drain a 12v lead acid leisure battery in no time if that is to be relied on without the engine and alternator running. If we turn the engine off and are off grid the fridge stays in 12v mode for 10 minutes before switching to gas.

Maybe older generation vans had these but how far back is this. 15 or 20 years or more? I know our 2003 Bailey caravan had an absorption fridge which is the oldest caravan we owned before transitioning to motorhomes in 2017. We did have a portable compressor fridge which we used in our tenting days but that was an AC job and required hook up but it would also run on gas.

Older generation? haha! It is the NEWER and highest spec vans that tend to have Compressor fridges. Absorption fridges are old technology and awful for cooling.
You know just how bad your fridge is on AC - 2kWh a day? that is actually pretty good for one of those. A Compressor Fridge is way way more efficient.

Not convinced a 12v compressor fridge would use just 15p worth of electric unless it was of extremely limited volume which for most off grid (or even on grid) motorhome owners would be useless unless you were prepared to make daily trips to the supermarket. Maybe every 5 or 6 days fine but daily trips! No way.

You have never used one so will have no idea of the consumption.
My own compressor Fridge uses around 500Wh/24 hours. That works out to be around 25p worth of grid electric at 50/kWh. That rate has just gone down to around 34p/kWh I think? halve that and you get 17p And that ignores the use of solar during the day which will make the grid cost even less.
How big is my Fridge? It is a proper Fridge/Freezer with a 90L Fridge Capacity and 45L Freezer Capacity. How does that compare to yours?
EDIT: Just saw you said the size of yours ... 133L. Guess mine is bigger than yours

Maybe is a smaller camper van that can creep under height barriers and fit into a standard car parking space a small fridge is acceptable but not in a difficult to manoeuvre in tight spaces large Motorhome.

 

[jacquigem]

The conversation had drifted from your OP to Jacquies setup


Older generation? haha! It is the NEWER and highest spec vans that tend to have Compressor fridges. Absorption fridges are old technology and awful for cooling.
You know just how bad your fridge is on AC - 2kWh a day? that is actually pretty good for one of those. A Compressor Fridge is way way more efficient.


You have never used one so will have no idea of the consumption.
My own compressor Fridge uses around 500Wh/24 hours. That works out to be around 25p worth of grid electric at 50/kWh. That rate has just gone down to around 34p/kWh I think? halve that and you get 17p And that ignores the use of solar during the day which will make the grid cost even less.
How big is my Fridge? It is a proper Fridge/Freezer with a 90L Fridge Capacity and 45L Freezer Capacity. How does that compare to yours?

Yes sorry for disrupting this conversation, trying to follow it though.

 

[Moped]

OK fair enough. Agree topic had moved on.

Didn’t realise that compression fridges are fitted as original equipment to higher end vans. As they are only 2 way either 12v or AC now understand the direction of travel of the topic.

Must admit though as a part time off grid fridge user I do like the comfort of knowing the fridge runs on LPG. There are occasions when we are off grid 4 weeks in 5 and conversely the opposite.

 

[wildebus]

More and more Motorhomes are listng Compressor fridges as options alongside Lithium setups. Morelo is a good example of that. And usually on the self-conversions you find the smaller 40L-50L Compressor fridge chosen as not only are they much easier to install (no big holes in the side of the van or gas pipes to run,) they are also more space efficient, with the only space in the back taken up by the compressor, rather than a bit chunk of the entire height taken by tubing, so greater capacity in the same footprint.
In the US, you will not find a gas fridge available even as a option on the high-end coach style RVs - they are all "residential" style Fridge/Freezers.

It is important however to understand the difference - and not mix up - the compressor fridge and the basic 12V coolboxes. They are very different things.
You mentioned you had a portable compressor fridge that also ran on LPG? That is very likely NOTa compressor fridge but just a portable absorption one (I nearly got one of those to use in my first camper conversion. I can't recall the name, but it was a mainstream make and the gas bit ran off the cartridges, same as the portable stoves, so was very transportable and self-contained. The electrics part was however just as inefficient as a built-in 3-way. I still think it was a great unit, but not right for what I needed once I looked at the specs more closely).
And there are the 12V coolboxes with the fans in the lid .... incredibly power hungry and only suitable to run on mains via a transformer or plugged into vehicle when driving.
A compressor fridge is very efficient - same as the one you would have in your house kitchen (if not, replace that immediately or you will be burning hundreds of pounds worth of unnecessary electrics a year!). To give an idea of the efficiency, the average power use is the same as the typical (non-LED) fridge light in one. If that light was stuck on for a day say, it would use the same power as the actual fridge in that time

 

[Moped]

In terms of home like compressor fridges they may be specified on high end motorhomes with lithium battery banks and 500w or more of solar on the roof and air con fitted as standard and more, but for the common man who buys the mass produced motorhome factory fitted 3 way absorption rules with their 100ah leisure batteries and possibly 100w panel on the roof.

From memory the compressor top hung camping fridge I purchased was a Waiko from Towsure. Mrs Moped has said It could definitely run on gas but we always used electric. Maybe the gas setting used absorption technology. It was luxury having a family tent and being able to drink a chilled French beer on those barmy Mediterranean family holidays. Especially after the bucket of cold water technic used previously which kept things cool but never really chilled. And it also meant we could go big on fresh fruit and veg for the first time.

However it was noisy and kept us awake at night in our tent so we turned the setting down at night to extend the quiet periods between the compressor running. Even our fridge at home makes a noise when running so if they do generate noise not too sure they would be popular in the average European motorhome where the fridge can be 2m-3m from the bed.

 

[wildebus]

When you said 'Waiko', I am guessing you meant "Waeco". The fridge you had sounds very much like one of the CombiCool models - https://www.leisureshopdirect.com/outdoor/cool-boxes/gas-powered-cool-boxes. They are ALL Absorption fridges. You will not get a fridge that is both Absorption AND Compressor, and you don't get Gas Compressor Fridges.
The one I was going to get was the CombiCool RC1200 If I recall right? Now become this model - https://www.leisureshopdirect.com/o...boxes/dometic-rc1205-with-gas-canister-cradle


Noise is a common complaint with some. It is very dependant on the fridge itself. The ones I have used have always been silent and the only noise I notice is a little vibration kick when the compressor comes on, but no noise from the compressor itself (FWIW, I used to actually open the door to see the light come on to check it was actually powered up as I could never hear it )
however .... the fridge/freezer I have in the house I could not put up with in a camper or Motorhome - it is way too noisy. That replaced a Fridge/Freezer last year and that old one was very quiet, so to a degree it is pot-luck to if the fridge is noisy or not. But if it is a noisy one, it will always be noisy when running, and if it is silent, it will always be silent, so you will know within a day if a fridge is suitable or not, so power it up before installing to check.