90-120 watt constant power draw with nothing on?

[birty]

When I'm out and about in my Elddis Crusader Zephyr and staying off-grid, I use a Bluetti power station along with an extra battery to keep things ticking over. I plug it into the caravan's mains using the 3-pin adapter into the power station—pretty much like you'd do at home to a standard plug.

I've noticed something odd though: even with the caravan's mains power switched off, the Bluetti still seems to be drawing around 90–120 watts constantly. 🤔

Does anyone know what might be causing that, or if there's a way to stop it? I could just switch the power station off, but ideally I'd like to keep my 5G router running, which only uses about 10–20 watts.

Any thoughts or advice would be much appreciated—thanks in advance!

 

[littlebasher]

The fridge will work independently to the 12V system when running on mains, probably that

 

[birty]

Hi, thank you for replying, I can confirm that the lights on the fridge are also off, it also does the same when the fridge running on gas overnight and all electric items are off, someone suggested that when on mains it may be trickle charging the leisure battery? Does this sound feasible? I would have thought once a battery was full it would stop charging?

 

[birdman101]

Would say it is the Battery main reason. If the Battery shows 12.6 volts fully charged,switch the charger off and see if the current draw stops.

 

[birty]

I just asked AI the question and got this might have answered my own question.! Same answer as you Birdman101 thank you! Presume to switch it off I just do at fuse board?

“That constant 90–120 W draw, even with everything in the caravan “off,” is almost certainly the built-in charger working to keep your leisure battery topped up — and those watts aren’t all going into the battery.

Here’s what’s likely happening:

1. The charger is always on when you’re on mains

• Many caravan power systems energise the charger automatically when hooked up to 230 V, even if you’ve turned off lights, sockets, and other appliances.
• The charger itself consumes power just to run — older or non-smart chargers can use 50–100 W even when the battery is full.

2. Float charging still draws a bit

• When your battery is full, a modern smart charger drops into a “float” mode at ~13.6 V, which should use only a handful of watts.
• If your system is older or basic, it may hold the battery at a higher voltage and waste power as heat.

3. Other always-on bits

Even with “everything off,” you’ll still have:

• Control panel electronics
• 12 V relays for fridge changeover
• Any fitted alarms or trackers
• Possibly a mains RCD/MCB board indicator light

If you want to prove it’s the charger:

1. Plug in the caravan to your portable power station as normal.
2. Switch off or unplug the charger at its breaker or fuse (often marked “Battery Charger” or “Converter”).
3. Watch the wattage — if it drops massively, you’ve found the culprit.

If that’s the case and you want to save your portable power station capacity, you can:

• Only charge the leisure battery periodically instead of continuously.
• Replace the charger with a modern multi-stage smart charger, which may idle at <5 W when not actively charging.

 

[otherclive]

I just asked AI the question and got this might have answered my own question.! Same answer as you Birdman101 thank you! Presume to switch it off I just do at fuse board?

“That constant 90–120 W draw, even with everything in the caravan “off,” is almost certainly the built-in charger working to keep your leisure battery topped up — and those watts aren’t all going into the battery.

Here’s what’s likely happening:

1. The charger is always on when you’re on mains

• Many caravan power systems energise the charger automatically when hooked up to 230 V, even if you’ve turned off lights, sockets, and other appliances.
• The charger itself consumes power just to run — older or non-smart chargers can use 50–100 W even when the battery is full.

2. Float charging still draws a bit

• When your battery is full, a modern smart charger drops into a “float” mode at ~13.6 V, which should use only a handful of watts.
• If your system is older or basic, it may hold the battery at a higher voltage and waste power as heat.

3. Other always-on bits

Even with “everything off,” you’ll still have:

• Control panel electronics
• 12 V relays for fridge changeover
• Any fitted alarms or trackers
• Possibly a mains RCD/MCB board indicator light

If you want to prove it’s the charger:

1. Plug in the caravan to your portable power station as normal.
2. Switch off or unplug the charger at its breaker or fuse (often marked “Battery Charger” or “Converter”).
3. Watch the wattage — if it drops massively, you’ve found the culprit.

If that’s the case and you want to save your portable power station capacity, you can:

• Only charge the leisure battery periodically instead of continuously.
• Replace the charger with a modern multi-stage smart charger, which may idle at <5 W when not actively charging.

Wow, which AI are you using, that’s seems a very comprehensive response. Surely not the normal AI from Google. Interested to hear how it works out. How was your question phrased?

 

[birty]

Used ChatGPT 5 (just been released)

Question 1
Will a leisure battery in a caravan continuously trickle charge when the caravan is connected to mains?

Answer 1
That depends on how your caravan’s electrical system is set up — they’re not all wired the same way.

In most modern caravans:

• Yes, the leisure battery will generally receive a continuous “float” or trickle charge whenever you’re plugged into mains via the caravan’s built-in charger.
• The charger isn’t pushing full power all the time — instead, it tops the battery up to full and then maintains it at a safe voltage (usually around 13.5–13.8V), so it’s more of a maintenance charge than a constant heavy charge.

However, there are exceptions:

• Older caravans (or some budget models) may have a simple charger that only works when you manually switch it on.
• Some setups only charge the battery when the 12V system is switched to “van use” rather than “car use.”
• If the charger is faulty, disconnected, or bypassed, you might get no charging at all from mains.

If you want to be sure, the easiest test is to plug the caravan into mains, wait a few minutes, and measure the battery voltage:

• If it rises to somewhere between 13.5–14.4V, it’s charging.
• If it stays around 12.6–12.8V and doesn’t budge, the charger isn’t active.

If you like, I can explain how to check whether your caravan has a smart charger or just a basic one — that can affect battery lifespan quite a bit.

Question 2
I use a portable power station and it is always using about 90-120watts despite all electrical appliances being switched off in the caravan working

Answer 2
That constant 90–120 W draw, even with everything in the caravan “off,” is almost certainly the built-in charger working to keep your leisure battery topped up — and those watts aren’t all going into the battery.

Here’s what’s likely happening:

1. The charger is always on when you’re on mains

• Many caravan power systems energise the charger automatically when hooked up to 230 V, even if you’ve turned off lights, sockets, and other appliances.
• The charger itself consumes power just to run — older or non-smart chargers can use 50–100 W even when the battery is full.

2. Float charging still draws a bit

• When your battery is full, a modern smart charger drops into a “float” mode at ~13.6 V, which should use only a handful of watts.
• If your system is older or basic, it may hold the battery at a higher voltage and waste power as heat.

3. Other always-on bits

Even with “everything off,” you’ll still have:

• Control panel electronics
• 12 V relays for fridge changeover
• Any fitted alarms or trackers
• Possibly a mains RCD/MCB board indicator light

If you want to prove it’s the charger:

1. Plug in the caravan to your portable power station as normal.
2. Switch off or unplug the charger at its breaker or fuse (often marked “Battery Charger” or “Converter”).
3. Watch the wattage — if it drops massively, you’ve found the culprit.

If that’s the case and you want to save your portable power station capacity, you can:

• Only charge the leisure battery periodically instead of continuously.
• Replace the charger with a modern multi-stage smart charger, which may idle at <5 W when not actively charging.

I can walk you through finding the charger in your caravan and checking whether it’s a modern smart unit or an older constant-draw type. That’ll tell us if you’re burning unnecessary watts.

 

[otherclive]

Used ChatGPT 5 (just been released)

Question 1
Will a leisure battery in a caravan continuously trickle charge when the caravan is connected to mains?

Answer 1
That depends on how your caravan’s electrical system is set up — they’re not all wired the same way.

In most modern caravans:

• Yes, the leisure battery will generally receive a continuous “float” or trickle charge whenever you’re plugged into mains via the caravan’s built-in charger.
• The charger isn’t pushing full power all the time — instead, it tops the battery up to full and then maintains it at a safe voltage (usually around 13.5–13.8V), so it’s more of a maintenance charge than a constant heavy charge.

However, there are exceptions:

• Older caravans (or some budget models) may have a simple charger that only works when you manually switch it on.
• Some setups only charge the battery when the 12V system is switched to “van use” rather than “car use.”
• If the charger is faulty, disconnected, or bypassed, you might get no charging at all from mains.

If you want to be sure, the easiest test is to plug the caravan into mains, wait a few minutes, and measure the battery voltage:

• If it rises to somewhere between 13.5–14.4V, it’s charging.
• If it stays around 12.6–12.8V and doesn’t budge, the charger isn’t active.

If you like, I can explain how to check whether your caravan has a smart charger or just a basic one — that can affect battery lifespan quite a bit.

Question 2
I use a portable power station and it is always using about 90-120watts despite all electrical appliances being switched off in the caravan working

Answer 2
That constant 90–120 W draw, even with everything in the caravan “off,” is almost certainly the built-in charger working to keep your leisure battery topped up — and those watts aren’t all going into the battery.

Here’s what’s likely happening:

1. The charger is always on when you’re on mains

• Many caravan power systems energise the charger automatically when hooked up to 230 V, even if you’ve turned off lights, sockets, and other appliances.
• The charger itself consumes power just to run — older or non-smart chargers can use 50–100 W even when the battery is full.

2. Float charging still draws a bit

• When your battery is full, a modern smart charger drops into a “float” mode at ~13.6 V, which should use only a handful of watts.
• If your system is older or basic, it may hold the battery at a higher voltage and waste power as heat.

3. Other always-on bits

Even with “everything off,” you’ll still have:

• Control panel electronics
• 12 V relays for fridge changeover
• Any fitted alarms or trackers
• Possibly a mains RCD/MCB board indicator light

If you want to prove it’s the charger:

1. Plug in the caravan to your portable power station as normal.
2. Switch off or unplug the charger at its breaker or fuse (often marked “Battery Charger” or “Converter”).
3. Watch the wattage — if it drops massively, you’ve found the culprit.

If that’s the case and you want to save your portable power station capacity, you can:

• Only charge the leisure battery periodically instead of continuously.
• Replace the charger with a modern multi-stage smart charger, which may idle at <5 W when not actively charging.

I can walk you through finding the charger in your caravan and checking whether it’s a modern smart unit or an older constant-draw type. That’ll tell us if you’re burning unnecessary watts.

Awesome. Thank you.

 

[ProfJohnL]

My initial thought when 90 to 120W was mentioned was that's about what a fridge would consume, but that would not be continuous as the thermostat would interrupt, power from time to time. and it would be a more consistent value as its a resistive element. Battery charging was my second thought, but even then 90 to 120W is a far too much of a power drain when the battery is full. Even an older (i.e. not "smart") charger was running I would be very suspicious if it drew that much power in standby.

There are not many mains appliances in a caravan, and none of them should draw mains power when switched off by their own controls, so I'd suggest switching off every mains appliance you can, and if possible unplug them, then check powe units power consumption again. It should be zero. If it's not then it menas there is a problem with some items somewhere in the caravan and it needs to be checked out.

Hopefully there will be no power consumption, at which point reconnect or switch on each mains item appliance and check the consumption until you find the one that causes this parasitic power draw. then you'll know which item it is and you can decide what's to be done.

 

[birty]

Thank you ProfJohnL,

I was just going to flick off the one that says Charger/Fridge here but wasn’t sure.

 

[birty]

 

[RogerL]

My initial thought when 90 to 120W was mentioned was that's about what a fridge would consume, but that would not be continuous as the thermostat would interrupt, power from time to time. and it would be a more consistent value as its a resistive element. Battery charging was my second thought, but even then 90 to 120W is a far too much of a power drain when the battery is full. Even an older (i.e. not "smart") charger was running I would be very suspicious if it drew that much power in standby.

There are not many mains appliances in a caravan, and none of them should draw mains power when switched off by their own controls, so I'd suggest switching off every mains appliance you can, and if possible unplug them, then check powe units power consumption again. It should be zero. If it's not then it menas there is a problem with some items somewhere in the caravan and it needs to be checked out.

Hopefully there will be no power consumption, at which point reconnect or switch on each mains item appliance and check the consumption until you find the one that causes this parasitic power draw. then you'll know which item it is and you can decide what's to be done.

Older battery chargers, aka onboard power supplies, would often be rated at 10A - which is of course nominally 120w - some of which were decidely not smart and continued generating power and or heat even when the battery was full - or at least as full as a 13.8v float charge could get it

 

[ProfJohnL]

Older battery chargers, aka onboard power supplies, would often be rated at 10A - which is of course nominally 120w - some of which were decidely not smart and continued generating power and or heat even when the battery was full - or at least as full as a 13.8v float charge could get it

Yes, but that is only partly true.

A power supply or charger will only consume as much power as it delivers to its load. The are known as constant power devices. Granted there are some inefficiencies but they are usually only around 10% or less for modern SMPS units and could be 20% for old linear transformers. I doubt this is the sole cause of birty's problem.

 

[Buckman]

I think Prof hit the nail on the head as the fridge will still draw 12v even though it is on gas. One of the main reasons why the 12v needs to be switched off when caravan is in storage.

 

[GUMPY]

I think Prof hit the nail on the head as the fridge will still draw 12v even though it is on gas. One of the main reasons why the 12v needs to be switched off when caravan is in storage.

On mine the 12v is still connected to the fridge control panel even with the master switch by the door off.

 

[Buckman]

On mine the 12v is still connected to the fridge control panel even with the master switch by the door off.

The master switch should be turned off, but the 12v also needs to be turned off. Two different switches.

 

[ProfJohnL]

The problem Birty has is not with any 12V appliance in the caravan, but with a power draw on the mains 230V ac system, thus the comments at #14 -#15 & #16 are not relevant to my previous comments.

I was just going to flick off the one that says Charger/Fridge here but wasn’t sure.

I think your on the right track. If you switch all the MCB's off (Charger/fridge, Heater Boiler and Sockets) that should isolate all mains appliances from your Bluetti power station. If it doesn't it means someone has messed about with the mains electrics wiring and you would need to get that repaired.

However assuming all the MCB's do isolate the circuits, try turning each one on, and see which of the circuits causes the power draw.

 

[Hutch]

The master switch should be turned off, but the 12v also needs to be turned off. Two different switches.

Not so, on my Coachman, with Master, and 12 volts switched off, 12 volt power is still at the fridge, aerial booster, radio( even with the front removed and to the entrance light via the alarm system.
So when I leave the van in storage I have to pull the relevant fuses, to leave just 12 volt to the alarm system.

 

[Buckman]

The problem Birty has is not with any 12V appliance in the caravan, but with a power draw on the mains 230V ac system, thus the comments at #14 -#15 & #16 are not relevant to my previous comments.

I think your on the right track. If you switch all the MCB's off (Charger/fridge, Heater Boiler and Sockets) that should isolate all mains appliances from your Bluetti power station. If it doesn't it means someone has messed about with the mains electrics wiring and you would need to get that repaired.

However assuming all the MCB's do isolate the circuits, try turning each one on, and see which of the circuits causes the power draw.

If the draw is while off grid, how will that help?

 

[Buckman]

Not so, on my Coachman, with Master, and 12 volts switched off, 12 volt power is still at the fridge, aerial booster, radio( even with the front removed and to the entrance light via the alarm system.
So when I leave the van in storage I have to pull the relevant fuses, to leave just 12 volt to the alarm system.

Doesn't seem right?

 

[Hutch]

Doesn't seem right?

I know, but that's the way it is, even looked at the wiring diagrams.

 

[Buckman]

I know, but that's the way it is, even looked at the wiring diagrams.

Sadly the consumer has to accept these drawbacks.

 

[ProfJohnL]

If the draw is while off grid, how will that help?

The OP told us in #1 that he is using a Bluetti connected to his EHU. You may not know, but a Bluetti in this context is a battery powered 230v ac inverter system commonly known as a "power station" They come in different sizes and different makes (Ecoflow is another increasingly common brand). They can be recharged by solar, 12V or mains power. They usually have quite comprehensive power usage information, which is how he knows there is a 90 to 120W power draw.

Birty is using his Bluetti as a source of 230V ac for his caravan whilst of grid.