Leisure battery/fridge question

fisherman

fisherman

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In a campervan, which I bought so no knowledge of wiring detail. It has a solar panel, MPPT controller, and something that clicks regularly down near the start battery when the sun is out.
On hols, with only the waeco fridge on, the battery would be dead an hour after the sun went. The fridge would start up in the morning with even minimal light on the panel. Avon 631, can't find if it's deep cycle or not, I disconnected it and after 24 hours it shows 13.2 volts.
I threw a sheet over the panel, turned everything on, the fridge draws 6A as described on the spec, without it there is a 0.3A drain. Where's my leccy going? The panel will handle the fridge and a peltier cold box at 48w no problem.
 
Have you got a VSR or similar battery charging device being used to split the charge to two batteries ?
 
If battery shows 13.2 volt no load, turn on fridge and watch the voltage, it should fall slowly, if it falls rapidly you are surface charging the attery, you need to bench charge, or replace battery. If voltage remains the same the fridge is supplied from alt battery.

Brian
 
Avon are reasonable budget battery but I wouldn't want to run down past 50% very often. Is is 631 or actually 635?

What size is the panel? Needs to be 120W to keep up with fridge and cold box together unless fridge is clever power efficient type. Check battery voltage at start and end of day with everything off.

The 0.3A draw is probably the VSR being held closed.
 
Fridge def from leisure bat, as tested the A draw between terminal and cable when it fired up. Bat is kept charged by the panel. Yes the panel is enough for fridge and cold box, 10A in all. VSR is the click on the start battery end. Yes I checked the bat over 24 hours disconnected, dropped to 13.2v. After 7 mins of fridge the bat seems to have settled at 12.46-12.49v, still 12.48v after 11mins. Van has not been driven for days. Panel is covered over. So could be surface charge...?

edit 12.5 now, battery is 681.
 
Perversely, after 30 mins the bat is at 12.51v. When I checked it in the early hours on hols it was down to 9v. Only difference is when fridge gets down to temp it cycles on and off. Working fine, freezes water in the ice box.
 
fisherman said:
Perversely, after 30 mins the bat is at 12.51v. When I checked it in the early hours on hols it was down to 9v. Only difference is when fridge gets down to temp it cycles on and off. Working fine, freezes water in the ice box.
Click to expand...

You do not appear to have a problem, probably under charged battery at first , now charged up, but 12.4 / 12.5 volt would be okay with fridge running, if you see 12 / 12.1 with fridge on you need to charge.

Brian

rian
 
If you are measuring 9V on the house battery, and it is happening regularly then I think your house battery may be scrap - if not now, then very soon.

Fridges are very power hungry, you said it draws 6A but dependent on how cold you set it, how good the insulation is, and how efficient the condenser etc. it will be cycling on and off all day (and night) and will probably come out somewhere around 0,85 kWh in a 24 hour period (12v, 6A, approx 50% duty cycle). The solar needs to be able to generate this energy during daylight hours (obviously). The battery is effectively a buffer which stores the energy and releases it over a 24hr period to meet the demands of all the electrical gear. A panel providing an average of 48W will need to run for 17 hours
to provide 0,85 kWh ... I don't know where your van is, but 17 hours of useable sunshine seems a bit optimistic.

The 0,3A that is going astray could be a car alarm, the electrical control panel or any other camper-van related goodies (gas heating?). Camper vans tend not to have a seperate battery isolator like boats - at least the ones I've used didn't - they also tend to be set up for mains hook-up.

For comparison, I need 0.8 kWh a day to sit at anchor and do nothing (fridge, lights, some electronics), I have 300W of solar panels, a 370Ah battery bank, the boat is in the Adriatic - in summer. With this arrangement, the batteries cycle between 90% (dawn) and 100% and are fully charged in 2-5 hours of daylight dependent on intensity.

It would be a good idea to do a power budget and check the optimal solar panel size and battery size for your intended use and location - before you replace the battery.

PS: Check and see if your fridge is 230V/12V/Gas .... if it can run on gas then the solar and battery requirements will be drastically reduced.
 
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Fridge is 12/24v. I have ample power in the sunshine, or even on a dull day, so the battery only comes in at night. Soon as it's light the fridge fires up from the panel and the battery comes up to 13v+. Just in the dark it seems to go quickly. I will run the fridge tonight and see if I can log the voltage drop. Fridge is definitely 6A, I put a tester in the circuit, how cold it is set just dictates time fired up. On test today it was running constantly having been just turned on.
If the battery is OK I will double up in parallel.
 
If you can run a fridge drawing 6 A from a single battery I think you are doing well. My fridge draws 3-4 A from 3x 120 Ah batteries, voltage usually down to 12.4v first thing. When we only had 2 x 120Ah the voltage was often 12.0v first thing.
 
fisherman said:
Fridge is 12/24v. I have ample power in the sunshine, or even on a dull day, so the battery only comes in at night. Soon as it's light the fridge fires up from the panel and the battery comes up to 13v+. Just in the dark it seems to go quickly. I will run the fridge tonight and see if I can log the voltage drop. Fridge is definitely 6A, I put a tester in the circuit, how cold it is set just dictates time fired up. On test today it was running constantly having been just turned on.
If the battery is OK I will double up in parallel.
Click to expand...

Probably need to find out what the MPPT controller is actually delivering.

The MPPT when working will pull the voltage up to 13V+ (bulk, absorb, float etc.) at the battery terminals, this doesn't mean it will effectively charge the battery though if the fridge and other loads are still drawing current, just getting it from the solar panels instead of the battery - what is left over will go into the battery, which could just be a trickle charge.

Warning: Fag Packet Calculations - numbers are approximate Just as an example, a typical fully charged 100Ah sealed lead acid "liesure" battery in theory holds 1.2 kWh (roughly 100Ah x 12v).

If an attached fridge draws 6A all night (10 Hours) ... then you have 10 hours x 12v x 6A = 0,72 kWh

The fridge would drain 60% of the total battery capacity overnight (0,72/1,2 x 100).

The next day, the solar system would need to replace this energy 0,72 kWh plus continue to run all the electrics, and if the fridge is still running for the remaining 14 hours of daylight then the solar system needs to deliver 0,72kWh (to recharge the batteries) + 1 kWh (14hours x 12v x 6A to run the fridge) ... making 1,72 kWh in total during 14 hours of daylight - you'd need about 350W of solar panels and a good sunny day to get that kind of return. To deliver 1,72 kWh in 14 hours, the MPPT would need to be pushing out approx 10A for the entire 14 hours.

Regularly discharging a lead acid battery to 40% capacity is borderline for battery life - and extending the night by a few hours will put the battery well into a state where it could be permanently damaged.

Battery voltage is not a great indicator of charge level, I trashed 2 house batteries in 5 years before biting the bullet and installing a decent electrical system. I tried to estimate charge level by voltage but often woke up in the morning with no fridge and a flat battery - needless to say, the batteries didn't last long.

If you can manage it, get a shunt based battery monitor, do a power budget and adjust panel/battery capacity accordingly. It pays in the long run.
 
Last edited:
fisherman said:
Fridge is 12/24v. I have ample power in the sunshine, or even on a dull day, so the battery only comes in at night. Soon as it's light the fridge fires up from the panel and the battery comes up to 13v+. Just in the dark it seems to go quickly. I will run the fridge tonight and see if I can log the voltage drop. Fridge is definitely 6A, I put a tester in the circuit, how cold it is set just dictates time fired up. On test today it was running constantly having been just turned on.
If the battery is OK I will double up in parallel.
Click to expand...

If the panel is large enough, battery voltage should be 14v+ when bulk charging. Battery charging and discharging quickly, would indicate knackered battery.
 
on a similar note , i have now fitted my isotherm ge80 compressor fridge ( previous post ) and wondered if there was any easy way to check the hourly power consumption . i know ican measure the amps drawn when it kicks in but wondered if there was any instrument i could fit that records the amps used ?
 
What you want is an amp/hr meter, the ones we use at work though are not cheap, about £150 and not sure they will work on 12v though
 
Thanks perfect - ordered . now i should be able to accurately calculate how much i need to increase my solar charging capacity.
 
Baggywrinkle said:
If you are measuring 9V on the house battery, and it is happening regularly then I think your house battery may be scrap - if not now, then very soon.

Fridges are very power hungry, you said it draws 6A but dependent on how cold you set it, how good the insulation is, and how efficient the condenser etc. it will be cycling on and off all day (and night) and will probably come out somewhere around 0,85 kWh in a 24 hour period (12v, 6A, approx 50% duty cycle). The solar needs to be able to generate this energy during daylight hours (obviously). The battery is effectively a buffer which stores the energy and releases it over a 24hr period to meet the demands of all the electrical gear. A panel providing an average of 48W will need to run for 17 hours
to provide 0,85 kWh ... I don't know where your van is, but 17 hours of useable sunshine seems a bit optimistic.

The 0,3A that is going astray could be a car alarm, the electrical control panel or any other camper-van related goodies (gas heating?). Camper vans tend not to have a seperate battery isolator like boats - at least the ones I've used didn't - they also tend to be set up for mains hook-up.

For comparison, I need 0.8 kWh a day to sit at anchor and do nothing (fridge, lights, some electronics), I have 300W of solar panels, a 370Ah battery bank, the boat is in the Adriatic - in summer. With this arrangement, the batteries cycle between 90% (dawn) and 100% and are fully charged in 2-5 hours of daylight dependent on intensity.

It would be a good idea to do a power budget and check the optimal solar panel size and battery size for your intended use and location - before you replace the battery.

PS: Check and see if your fridge is 230V/12V/Gas .... if it can run on gas then the solar and battery requirements will be drastically reduced.
Click to expand...
I would be very very careful about running a multi power fridge (absorption type) using gas on a boat. These absorption type fridges are fine in camper vans and caravans where there will be a permanently open low level vent to allow the flame exhaust to safely vent, but on a boat with the hull sealed at low level the heavy exhaust fumes can sink into the boat, as can LPG gas leaks. The consequence of insufficient oxygen to the flame, albeit small can still allow lethal CO to build up.
 
superheat6k said:
I would be very very careful about running a multi power fridge (absorption type) using gas on a boat. These absorption type fridges are fine in camper vans and caravans where there will be a permanently open low level vent to allow the flame exhaust to safely vent, but on a boat with the hull sealed at low level the heavy exhaust fumes can sink into the boat, as can LPG gas leaks. The consequence of insufficient oxygen to the flame, albeit small can still allow lethal CO to build up.
Click to expand...

The OP was talking about his camper van - which is why I mentioned gas. I agree ... gas fridge on a boat = very bad idea for exactly the reasons you describe. I certainly wouldn't suggest putting a gas fridge on a boat and I hope no-one else interpreted my post as suggesting it.
 
Just to make sure the Waeco fridge is a compressor type which clearly cycles off and on once down to temp. If it is a peltier type then ditch it. Likewise the peltier cooler you referred to. The Waeco certainly the smaller ones draw around 4.5 amps when running so should average about 1.5 amps. (more when set as a freezer in hot weather) My waeco has a battery low voltage cut off which has in fact 2 settings of high and low for cut off at a reasonably high voltage like 12.5 volts or a low at 11.5 v (not sure of exact volts)
I am guessing that OP has this facility working as fridge does cut off. Certainly a cheap volt meter from China wired in would give you a convenient way to check battery performance.
I would want to have separate battery for the fridge and lights etc from that used for engine starting just like on a boat.
This would require a VSR to provide auto charging and isolation.
Avoid like the plague the 3 way gas 240v 12v fridges if you want to run on 12v they just use too much current.
Ultimately OP will just have to sort out the 12v arrangements in the van and set it up in a way that suits him. ol'will
 
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