Battery Dead or something else I should check? - Motorhome Forums, Motorhome Discussion, Motorhome Chat

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post #1 of 11 (permalink) Old 16-09-2020, 20:50 Thread Starter
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Unhappy Battery Dead or something else I should check?

have installed an Ective Solar Panel system in my 6. month old Campervan. It is connected to an 80 Ah AGM battery. My fridge is a 12 volt fridge.

After installing the solar panels several months ago, my battery voltage never dropped below 12.50 volts overnight. This I understand is using perhaps 30% of a battery capacity, so well within the 50% target to maximise the life of my battery.

The solar panel is always active and i can see from my App for the system that when the battery is full it correctly trickle charges, sometimes only topping up the battery with 5Wh in a day, (but mostly around 50Wh), when the fridge is off.

About 3 weeks ago, we went away for the weekend with friends.
I turned on the fridge Wednesday (Day 1) sometime to let it cool down.
Thursday (Day 2) loaded it up with beer.
Friday (Day 3) kept on adding beer to it to cool beer down.
Saturday (Day 4) opened my App and looked at the info.

Day 2 minimum voltage was 10.2 V
Day 3 7.9 V
Day 4 8.4 V

Next weekend, covered the solar panels and did a test. After 7 hours of running my fridge, the battery voltage 13.1 V(no load)/13.0 V(underload) to 12.9V (no load)/12.7 V (under the load of the fridge).
The next morning before I uncovered my solar panels, the voltage came back up to 13.0 V.So assumed I cooling down all the beer used more energy than I assumed the previous weekend and there was nothing wrong. All voltages were confirm with a separate voltmeter.

This weekend, headed away for the weekend. Saturday morning notice that the minimum voltage was super low again over night (I think 6.6ish V) and I got a low voltage alarm on my heating system.
Saturday night I did a test.
Solar panels stopped generating power around 7:30pm I guess. Battery voltage was around 14.0V.
At 1am the voltage with fridge running was 12.8 V
At 3 am the voltage drop to 12.0 V. I turned the fridge off.

When the sun came up, I turned the fridge on. And Solar panels charged the battery giving it 430Wh, which is similar to what was required to fill the battery up prior to this issue.

Sunday night, I turned the Fridge off when we went to bed with 12.9 V. In the morning, turned the fridge back on (still very cold) and turned on the diesel standing heater. 60-90 secs later, the LED's started to flicker and the heater switched itself off. Minimum voltage was 6.93V. The fan of the heater and the fridge killed it .

Other possible important facts:
- On really hot sunny days, sometime I will get an over voltage alarm on my heating, but my Solar system shows max voltage was 14.82 V, so assume the voltage spike is very short
- last week a few days before we went away, the fuse between my MMPT Charge controller and battery blew. Electrics in motorhome were switched off.
- all currents are well within the capacity of the MMPT and cables. Never seen the current above 20 AMPS. MMPT is rated at 25 AMPS.
- I know I have only ever drain the battery anywhere near empty once, before i installed the solar panels. After a day and a half, the LED indicator suggested it was about 10-25% capacity. I understand a AGM should be able to cope with 100% drain about 20 times?

Can anyone suggest if there is anything I can further test? How can i do a battery load test?
Could it just be an unlucky battery that I should claim under warranty?

Any suggestions would be appreciated.

Cheers
Bryce
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post #2 of 11 (permalink) Old 16-09-2020, 21:31
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Haven't fully digested your tale of woe but are you saying your trying to power the van fridge on 12v and hoping the solar panel will maintain the battery 12v?

It won't work. The fridge will take about 20 amps and the solar panel might just put back 4 amps. That will result in a dead battery within a few hours.
The fridge needs to be on gas when not travelling.

Ray.
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post #3 of 11 (permalink) Old 16-09-2020, 22:51
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Agree totall with Ray; you SHOULD have three ways of powering your fridge;

1. Mains voltage (240 v nominally), this should be used WHENEVER POSSIBLE to prechill the fridge before a trip and during any trip where mains EHU is available,

2. 12v this is the most inefficient way of cooling the fridge, the current drain is too high for solar panels even here in the very sunny South of France at mid-day, 12v should ONLY be used while the engine is actually running and the wiring should prevent any other use of the 12v system for cooling, if not then there is a SERIOUS fault in the wiring. The 12 v is so inefficient that the fridge thermostat is bypassed while on 12 v so the fridge in theory gets colder and colder,

3. Gas, this should be used when the vehicle is on a site IF NO MAINS EHU AVAILABLE, but only if, it may require extra cooling fans for really efficient operation in hot weather but is VERY efficient at cooking the fridge down (it actually puts in about four times as much cooking power than even mains EHU. It must NEVER be used while underway cure to a serious fire risk in the event of a road traffic collision. Seen one MH burn out within 7 minutes, fortunately we were able to get the sole occupant out just before the cylinders exploded.

Please use this as fairly fundamental advice, you CANNOT operate your fridge from solar panels - they only deliver their maximum output when the sun is directly overhead - and how often does that happen each day ? Of course, there is absolutely NO charge if cloudy, raining, evening, ,orning or night in other words most of the 24/7. Our twin 85w panels + a portable 7w panel deliver just over 4.5a here at mid-day but we have recently had most days in the mid 30's....... with full sun and zero cloud and a <1% chance of rain during the day. Can you match those conditions ?
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post #4 of 11 (permalink) Old 17-09-2020, 08:45
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He states at the start, the van is fitted with a 12 volt fridge, it is popular now to fit 12 volt compressor fridges not 3 way.

They consume far less current than a 3 way absorption.

The normal consumption quoted for this type of fridge is around 260w in 24 hours.

Unfortunately I can't help with his dilemma though.

.

John

Last edited by eurajohn; 17-09-2020 at 08:50.
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post #5 of 11 (permalink) Old 17-09-2020, 19:55 Thread Starter
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Quote:
Originally Posted by eurajohn View Post
He states at the start, the van is fitted with a 12 volt fridge, it is popular now to fit 12 volt compressor fridges not 3 way.

They consume far less current than a 3 way absorption.

The normal consumption quoted for this type of fridge is around 260w in 24 hours.

Unfortunately I can't help with his dilemma though.

.
yep, you are correct, mine is rated to consume about 385Wh per 24 hours at 25 degrees. No gas, 240V. If I plug into shore power, then it charges the battery and the fridge runs off the battery still. Manufacture states 200 AH AGM battery, using 50% battery capacity, is good for 3-4 days.

I have calculated my requirements to run everything. I have over spec'd my solar panels Wattage requirements by about 100% to ensure I have enough power on rainy days. Based on the power generated in the first two months, the power generated from the panels is not the problem.

My panels can push 20 AMPs into the battery.
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post #6 of 11 (permalink) Old 17-09-2020, 19:59 Thread Starter
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Quote:
Originally Posted by Penquin View Post
Agree totall with Ray; you SHOULD have three ways of powering your fridge;

1. Mains voltage (240 v nominally), this should be used WHENEVER POSSIBLE to prechill the fridge before a trip and during any trip where mains EHU is available,

2. 12v this is the most inefficient way of cooling the fridge, the current drain is too high for solar panels even here in the very sunny South of France at mid-day, 12v should ONLY be used while the engine is actually running and the wiring should prevent any other use of the 12v system for cooling, if not then there is a SERIOUS fault in the wiring. The 12 v is so inefficient that the fridge thermostat is bypassed while on 12 v so the fridge in theory gets colder and colder,

3. Gas, this should be used when the vehicle is on a site IF NO MAINS EHU AVAILABLE, but only if, it may require extra cooling fans for really efficient operation in hot weather but is VERY efficient at cooking the fridge down (it actually puts in about four times as much cooking power than even mains EHU. It must NEVER be used while underway cure to a serious fire risk in the event of a road traffic collision. Seen one MH burn out within 7 minutes, fortunately we were able to get the sole occupant out just before the cylinders exploded.

Please use this as fairly fundamental advice, you CANNOT operate your fridge from solar panels - they only deliver their maximum output when the sun is directly overhead - and how often does that happen each day ? Of course, there is absolutely NO charge if cloudy, raining, evening, ,orning or night in other words most of the 24/7. Our twin 85w panels + a portable 7w panel deliver just over 4.5a here at mid-day but we have recently had most days in the mid 30's....... with full sun and zero cloud and a <1% chance of rain during the day. Can you match those conditions ?
My 260W panels keep my battery fully charged on a rainy day at about 20 degrees, so the battery is only needed at night. In 100% perfect conditions, my panels need no more than 2 hours to supply a full days fridge consumption. Typically the battery is fully charged by lunchtime.
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post #7 of 11 (permalink) Old 17-09-2020, 20:17
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OK but can you enlighten us as to the power of the fridge and is it ONLY 12v?

Ray.

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post #8 of 11 (permalink) Old 17-09-2020, 20:53
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Quote:
Originally Posted by raynipper View Post
OK but can you enlighten us as to the power of the fridge and is it ONLY 12v?

Ray.
Something like this Ray https://www.ludospace.com/webasto-el...4v-c2x20187462.

.

John
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post #9 of 11 (permalink) Old 17-09-2020, 21:28 Thread Starter
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12V Fridge

Quote:
Originally Posted by raynipper View Post
OK but can you enlighten us as to the power of the fridge and is it ONLY 12v?

Ray.
It's only 12V.

Isotherm CRUISE EL 85

https://www.webasto.com/fileadmin/we...idges-2017.pdf
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post #10 of 11 (permalink) Old 17-09-2020, 21:31
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OK and thanks. In that case I give up.

Ray.

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