Camper van electrics issues

Rob1960

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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
 
Two or three things, battery on its way out, pwm control unit instead of MPPT, s panel not working.
My electric fridge draws 250mA and will run no bother on 2 90 ah old type l acids, but i do have 200w solar running through a votronic mppt regulator.
Have the battery tested for load, and if nackered fit a lead carbon which wont require any changes to the system.
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Running a 12V compressor fridge off a 70Ah battery will never be very successful I think. No matter what your current problem is (bad battery, bad connection, etc.), I think a bit of a rethink is needed to really be able to enjoy your travels.
people's ideas vary of course, but having to turn off the fridge overnight is a pain (and if you have meats in the fridge or a freezer compartment, you are taking on a health risk, especially in the summertime, IMO).
The solar may be rated to put in 5.35A max, but that was will be happening very rarely and you are probably looking at 2-3A average during the day. I kno you said the fridge is the only electricsl device, but what about the basic things? AI presume you also do other stuff in your van, so that 70Ah battery will be running lights, water pump, phone charging maybe, etc as well as running the fridge?
I would say a battery at least twice the size as a minimum is needed to have a safe environment for the perishables.
 
If that 6 amps every hour plugged in is correct it uses more than my Waeco (48a per 24h) I can run 2.5 days with no charge going in on 200ah lifepo4. You will need more battery storage and a way of replacing what you use each day. I too am not a fan of turning off the fridge at night but I always have a lot in the freezer
 
Nabsim said:
If that 6 amps every hour plugged in is correct it uses more than my Waeco (48a per 24h) I can run 2.5 days with no charge going in on 200ah lifepo4. You will need more battery storage and a way of replacing what you use each day. I too am not a fan of turning off the fridge at night but I always have a lot in the freezer
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It is a decent make of Fridge, so I would think that 6A is the running power when on, but will have a reasonable on/off duty cycle and maybe average around 1.5-2.0Ah/per hour similar to yours (and also mine - For my 240V Fridge/Freezer I use 45Ah per day plus inverter overhead so around 50Ah).

You see quite a few people saying "I can run my compressor fridge all weekend on my single battery" and that gives quite a misleading impression to others as what those people don't say is that they start off with a full battery, load up the fridge with frozen bottles of water, turn off the fridge overnight and don't use it on the Sunday as they are on their way home (so actually only running the fridge for around 12 hours in total :) )
 
Rob1960 said:
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
Click to expand...
Auto electrician to sort your power outage, from my experience T5.1, a 12v compressor fridge will use less amps per day. I would suggest 200 w of solar on the roof, because the panel output can be a lot less than quoted, can you double up your habitation battery capacity, 80ah x 2 will fit under both front seats, with some careful attention and shimming of drivers seat. 🙂
 
As above, my guess is your battery and solar is not up to the job, because of this the battery is getting hammered and because of this it's now knackered. Take a voltmeter and check the voltage AT THE BATTERY TERMINALS while the fridge is running, when it reaches 11.5v stop discharging unless it's lithium or lead carbon.
Oh and Yes, your control system is almost certainly closing down when the voltage reaches a critical low voltage.
 
merl said:
As above, my guess is your battery and solar is not up to the job, because of this the battery is getting hammered and because of this it's now knackered. Take a voltmeter and check the voltage AT THE BATTERY TERMINALS while the fridge is running, when it reaches 11.5v stop discharging unless it's lithium or lead carbon.
Oh and Yes, your control system is almost certainly closing down when the voltage reaches a critical low voltage.
Click to expand...
Ah. That reminds me ....
If this was a typical VW T5 "professional" conversion, the DC cabling to the compressor fridge will be undersized. So what happens is the compressor kicks in, creating a inrush current draw up to 10 times the actual running power; The voltage drop on the undersized cable will increase to such an extent that the fridge reports low voltage and will not start despite the battery being no where near depleted.

It is not unusual for a leisure battery to be at 12.4V and a fridge refusing to start up due to low voltage issues. So one key thing to check is the gauge of the fridge cabling. Depending on the distance of the cable run from Battery to Fridge, it should be an absolute minimum of 4mm2 and potentially upto 10mm2. Too many installers just look at the fridge specs, see the current when running (e.g. 6A) and get cable that can support 6A, and not cable that can deal with the voltage drop when 60A+ is demanded.
(I used to speak to multiple people at every VW Show I was at who had this problem.)

If the cable is undersized and the fridge is cutting out prematurely, it might be the case that the battery is still reasonably healthy in fact. But even if it is OK, it is still woefully undersized to run a compressor fridge off-grid for any significant duration.
 
lol. can't remember if I have 15a or 20a thin wall marine cable to my fridge, may even be some of the 25a I had. Fused of course but a lot bigger than I needed just for the volt drop
 
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