Camper van electrics

[Rob1960]

Hi. I wonder if anyone can help. I have a T5 fitted with a 70Ah leisure battery. I don't have a hook-up but rely on a 100W solar panel which delivers 5.35Ah at Pmax via a solar controller. The only electrical device I use is an Isotherm fridge which is 72 W and draws 6Ah off a 12v battery. I turn the fridge off overnight but have 2 issues. If I turn the fridge on when the engine isn't running, the van electrics go totally dead. They will only come back to life when I run the engine for a period. I have also noticed that if I leave the van during the day with the fridge running, I sometimes get back and same thing - electrics totally dead, even when van is parked in full sun. Clearly my panel is not generating enough power but surely the leisure battery should have enough in reserve to keep the fridge going during the day when supplemented by the panel. Also, what is happening here? There is no cutout in the system. Is the battery somehow shutting itself down? If so, this can't be doing the battery any
good.

Any suggestions? For example, can I buy a standalone solar panel to plug into the 12v socket and supplement the roof mounted panel during the day?
Thanks, Rob

 

[Harry Bloomfield]

They will only come back to life when I run the engine for a period. I have also noticed that if I leave the van during the day with the fridge running, I sometimes get back and same thing - electrics totally dead, even when van is parked in full sun. Clearly my panel is not generating enough power but surely the leisure battery should have enough in reserve to keep the fridge going during the day when supplemented by the panel. Also, what is happening here?

Usually, 12v fridges are only designed to run from the 12v, when the engine is running. When the engine is not running, they expect you to swap over to gas when parked. I suspect your fridge is itself switching off, as it spots the voltage falling under load, despite the solar panel.

 

[oldbutnotdead]

As above, run the fridge on gas when you are parked up.
Your 70Ah battery (unless brand new) is likely only holding 50 Ah.
Your solar panel delivery current- is that measured or are you just looking at data sheet?

 

[just pumps]

My 12v fridge on the boat does not need the engine running so perhaps it is how it is wired up causing the problem in the van.

Before anybody mentions gas again, some fridges are electric only!

 

[SUNRAY]

As above, run the fridge on gas when you are parked up.
Your 70Ah battery (unless brand new) is likely only holding 50 Ah.
Your solar panel delivery current- is that measured or are you just looking at data sheet?

I currently have 4 leisure batteries here ~120Ah used for portable power (such as public address systems and radio comms etc) I leave Lidl smart chargers permanently running when not in use, My ACT battery analyser is currently telling me they are all 30-45Ah, however they are something like 6-8 years old and truthfully only consider the analyser to be a guide but I have watched the reading steadily drop over the years.

 

[aesmith]

Your 70Ah battery (unless brand new) is likely only holding 50 Ah.

Unless it's a real fancy battery it will have a really short life if discharged below 50%. And without an equally fancy charger probably won't ever be fully charged. So usable capacity may be more like 30Ah.

 

[EFLImpudence]

Just to point out:

100W solar panel which delivers 5.35Ah at Pmax via a solar controller.

That is 5.35A; not 5.35Ah unless it does it for an hour. You state that is the maximum with best weather.

The only electrical device I use is an Isotherm fridge which is 72 W and draws 6Ah off a 12v battery.

Again that is 6A; not 6Ah unless it does it for an hour.

So, if perhaps not the best weather and panel only delivering 3A or even 5A, yet fridge needs 6.

 

[Rob1960]

Thanks all. I don't have an option to run the fridge on gas unfortunately. It's not the fridge which is shutting down - it's the whole electrical system. Sounds like I've knackered the battery and I need to upgrade the whole system. Trouble is the battery compartment in my conversion is incredibly tight - no room for a bigger battery or a second one.

 

[Rob1960]

As above, run the fridge on gas when you are parked up.
Your 70Ah battery (unless brand new) is likely only holding 50 Ah.
Your solar panel delivery current- is that measured or are you just looking at data sheet?

That's data sheet for the panel.

 

[JohnW2]

.... If I turn the fridge on when the engine isn't running, the van electrics go totally dead.

Pretty 'flat' battery.

They will only come back to life when I run the engine for a period. I have also noticed that if I leave the van during the day with the fridge running, I sometimes get back and same thing - electrics totally dead, even when van is parked in full sun. Clearly my panel is not generating enough power but surely the leisure battery should have enough in reserve to keep the fridge going during the day when supplemented by the panel.

Even without the solar panel, a fully-charged 70 Ah battery would run the fridge for a goof few hours.

The battery will presumably only get charged when the van's engine is running. If, with the engine not running, the fridge took 6A continuously (probably not) and if the maximum you can get from the solar panel is 5.3A, then the battery would bee gradually discharging, rather than charging, even if the solar panel were providing its 'maximum output' continuously.

How old is this battery?

Kind Regards, John

 

[cdbe]

That battery and panel can't run that fridge. You need either a compressor fridge or a gas fridge.

 

[Rob1960]

Pretty 'flat' battery.

Even without the solar panel, a fully-charged 70 Ah battery would run the fridge for a goof few hours.

The battery will presumably only get charged when the van's engine is running. If, with the engine not running, the fridge took 6A continuously (probably not) and if the maximum you can get from the solar panel is 5.3A, then the battery would bee gradually discharging, rather than charging, even if the solar panel were providing its 'maximum output' continuously.

How old is this battery?

Kind Regards, John

Hi John. It's about 3 years old. I am quite careful not to over-discharge it but the cutting out happens when I'm not in the van - I suspect in these circumstances I have inadvertently done so and probably damaged the battery as a consequence. Do failing batteries just stop delivering any power at all if overloaded. This is what slightly baffles and alarms me. If it was just tripping something then you would be able to turn off the fridge, flick the trip switch and allow the battery to recharge but the having to turn the engine on and hope that it comes back to life is alarming!

 

[JohnW2]

Hi John. It's about 3 years old. I am quite careful not to over-discharge it ...

If "[if you] turn the fridge on when the engine isn't running, the van electrics go totally dead.", the battery must (at that time) be very discharged and/or 'failing/ill' .

.... Do failing batteries just stop delivering any power at all if overloaded.

If a battery is 'failing', applying any significant load (e.g. the 6A load of your fridge) will cause the voltage to fall to a low level, in which case it's quite possible that 'everything will go dead'.

Kind Regards, John

 

[ericmark]

For boats you can't have gas as they need a vent underneath them and if fitted the boat sinks.

So they are often compressor type, which use less power and cycle on/off.

There are also fridges that use a semi conductor and a heater, they are both very inefficient, and British rules will not allow them to be used on 230 volt unless they have gas as an option, this makes them multi fuel so gets around efficiency ratings.

It seems you can have 12 volt only, but not 12/230 volt any more.

Often there is no regulation on 12 volt, it is only intended to be used while travelling between sites.

Now onto lead acid battery. The problem is charge rate, to recharge in 8 hours needs a stage charger, and with stop/start technology often the vehicle alternator switches off, so the old split charging does not work, you need a DC to DC inverter so the leasure battery is charged at 14.4 or 14.8 volt but vehicle battery at 13.8 volt, other wise the battery will never fully charge.

 

[Diver Fred]

Does your van have Battery control system (battery black box)? That could be shutting down the 'leisure' battery output if it goes below a preset voltage. It may also control how much charge is applied to the leisure until the vehicle battery is fully charged.

How does the split charge device work? Is it a relay system or a Diode system?
If it's a relay system how does it switch on? Voltage level? Ignition warning light?
If it's a diode where does the voltage sense lead connect - on the vehicle battery side of the diode or not? (FYI - there is something like half a volt drop across the diode pack which will mean, if the sense lead is not on the vehicle battery side of the diode pack, the battery(s) will never fully charge.)

edit: to clarify the FYI comment.