240V compressor fridge not starting at night

[chrispierre01]

Hello!

So I bought in 2021 a Renault Traffic that had been converted to a small motorhome by the previous owner in 2020.

• The electrical setup includes a 12V auxiliary- gel battery which is charged via a solar panel (and its controller) as well as Citrix- ct Battery combiner (connected to 12v starter battery).
• The 12V auxiliary battery powers various LED lights, USB sockets, 12V cigarette lighter, and an inverter which powers a 240V compressor fridge. There are usually no other devices connected on the 240V circuit.

Up until 2023 all was working correctly but since then the fridge has problems turning on (mostly during the night) and it sets off the low-voltage alarm on the inverter. I am struggling to understand the reason why suddenly the fridge is starting to have issues when all was working fine before. The fridge works fine when the engine is running or if the van is parked in the sun and the solar panel charges the battery.

Here is the specification of the equipment used:

- Battery -12V 87.9Ah Gel Dyno europe Dgy12 -80ev

- Solar controller- Victron PWM Light Charge controller 12V-10A

https://www.victronenergy.com/upload/documents/Manual-BlueSolar-PWM-Light-12-24V-Charge-Controller-EN-A4.pdf

- Inverter 240V- Victron 12/500 VA (Continuous power 400W, Surge 900W)

https://www.victronenergy.com/upload/documents/Manual-Inverter-VE.Direct-250VA-1200VA-EN-NL-FR-DE-ES-IT-.pdf

- Fridge (240V compressor type) - Bomann BS389 42L 70W 84Kwh

https://www.manua.ls/bomann/kb-389/manual.

- Battery combiner- Victron Cytrix-ct 12/24-120

https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf

I have performed some measurements on the system to understand the source of the issues:
Fridge
Whilst the fridge was connected to the inverter in the van, I measured the inrush current and the continuous operating current using a clamp multimeter.

When the fridge is running normally it has an AC current of 0.2A and a 4A inrush current giving a power rating of 46W and 920W respectively (note the fridge is rated at 70W). For me the inrush current seems very high for a mini fridge, most articles I found on the web indicate that the inrush current is 4-10 times the rated current. In this case its around 20 times higher!

Could there be an issue with the fridge causing it to have such a high inrush current?

Battery
I purchased a battery tester and connected to the auxiliary battery. According to the battery spec the CCA at 0C should 600a with an internal resistance of 5.7mOhm. According to the tester the CCA is 188, internal resistance 13.6mOhm and the SOH is 10% whilst the battery SOC is 98%.

As I understand the battery is pretty much dead- 4 years after being installed.... According to the battery spec it should last 12 years!

Is this because the previous owner installed a gel battery directly to the main battery via a Citrix - ct battery combiner rather than using a DC-DC converter that provides the correct charging regime to the gel battery (like the solar controller) ? Should I replace then this equipment?

Other thoughts I had but so far discarded as everything worked in the past

• The inverter cannot support the surge current of 920W
• The wires between the battery and the inverter are too thin and are not of the minimum required AWG to support the current surge.

I am a bit of a loss at what to do next, and if I should:

• Replace the inverter with say a Victron/800 VA (Continuous power 650W, surge 1500W)
• Replace the fridge (as its faulty)
• Change the wiring for a more suitable AWG.
• Replace the battery
• Replace the citrix ct battery combiner with a DC to DC converter such as this one: https://www.victronenergy.com/dc-dc-converters/orion-tr-smart-non-isolated

As these modifications are quite costly, I was hoping to get some advice before going any further. Thanks in advance for your support!

 

[CAB96]

Welcome to the forum.

As you say, the battery is as good as dead. Presumably the fridge has pulled it below the recommended state of charge too often.

I can't comment on the rest, someone more knowledgeable will be along shortly no doubt.

 

[Terry]

Your solar is helping the battery during daylight but come night there is not enough charge to keep the fridge going - You need a new battery!

 

[f6c]

Welcome aboard

 

[autorouter]

There's a couple of things you need to know about the battery. All lead-acid battery types (flooded, gel, AGM etc) need to be fully charged to 100% periodically, every month or so. If they are left partly discharged for long periods, the sulfate that forms during discharge starts crystallising, and can't be turned back into the plate materials (lead, lead oxide) during the charging process. So the battery gradually loses capacity. The battery charges and discharges OK, but behaves exactly like a battery with a much smaller capacity.

Also, Gel batteries need an extended absorption time. During charging, if any gases (H2, O2) are produced, they can be recombined back into water (H2O) at the plates, if enough time is available. An extended timed absorption stage, maybe several hours, is used to be sure that all the gases are recombined. Otherwise the gel electrolyte gradually loses water and the battery slowly fails.

If the battery is charged on mains hookup, then it's usually for many hours, if plugged in overnight for example. That is enough to sort out the sulfation and recombine any gases produced. However if the MH is rarely on hookup, the solar plus split charge relay may struggle to work for the necessary extended time periods to keep a Gel battery happy. Especially as there is a more or less continuous draw by the electric fridge.

So what to do? I agree that a new battery is required, but how to stop the same thing happening again? A night on mains hookup every couple of weeks would sort out the sulfation and give the gases chance to recombine to avoid water loss.

If that's not what you want to do, then more solar panels and a bigger controller would refill the batteries better, at least in the summer months. You don't say how much solar you have, but with a 10A PWM controller I imagine about 100W. I think at least 200W is required to keep a compressor fridge supplied. If you upgraded the solar to say 200W or even 300W, with an MPPT controller, that would be an alternative to hookup to keep the fridge supplied and the battery full, at least in the summer.

A more expensive but definite fix would be to get a lithium battery, which just doesn't have the sulfation problem or the recombining problem, and can be left at 50% for years without a problem. But a lithium battery would need a B2B (DC-DC Charger) because I think that Cyrix-ct VSR is probably not suitable for lithium. And maybe more solar and a new MPPT controller.

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[chrispierre01]

Thankyou for your replies!

In terms of usage of the van, it is generally parked for a long period of time (usually winter months) with the inverter/fridge turned off, but the solar panel controller and solar panel are still connected to keep the battery charged as much as possible and prevent any deep discharge. When we are out on the road it is 1-3 weeks at a time, after which we again switch the inverter and fridge off and leave parked for at least 2-3 weeks before setting off again. We have a mains plug that we can hookup but tend to be more off grid.

Would this be sufficient to keep the gel battery happy? The solar panel is rated at 200W.

In parallel, I am a little worried that with the current setup I have been over charging the auxiliary battery with a Cyrix-CT as the Gel battery will be given potentially 30A (14.5V) from the primary battery when the engine is running plus the 10A (14.5V) from the solar controller when sunny = totalling 40A. According to the gel battery spec, the maximum allowed charging current is 20A and it should having a charging regime of bulk, absorption then float (which is OK with the solar charge controller) but with the Cytrix- CT this is not the case.

Could this setup be ruining the auxiliary battery as well? I understand a DC to DC charger can help with providing the same charging regime from the main battery as per the the solar charger controller but it may still provide too much current -40A to the auxiliary battery.

Based on your feedback, it is pretty clear for me that I need to change the battery (potentially to a lithium one) and also add a BDB (DC- DC charger). But just wanted to clarify the other points regarding over charge and over voltage before making the investment

 

[Raul]

Battery is tired and too small to cope with fridge surge start up. As it discharges at night, without solar support, it hasn't got enough for several starts. It may cope with 1-2 starts after sun down, then it bogs. The inverter low voltage confirms this too.

 

[autorouter]

I'd be surprised if the battery is getting 30A from the Cyrix-CT when the engine is running. It's basically a split charge relay, so the alternator can charge both starter and leisure battery at the same time when the engine is running. Usually the charge to the leisure battery is quite disappointing, which is why people upgrade to a B2B. You could check the amps with a DC clamp meter.

Also I'm sure the 200W solar is not giving its best with a 10A PWM controller. I think upgrading the controller to an MPPT 15A or even 20A would improve the yield quite a lot, and would be a simple swap.

If you're concerned about overcharging then you could get two gel batteries, and wire them in parallel to give one big 12V battery. That pair could be charged at 40A (20A per battery), with a bonus that you could last so much longer off-grid in a spell of dull weather. If you went for the lithium option I think you would also need to remove the Cyrix-CT and upgrade to a B2B.

 

[Hoovie]

Hello!

So I bought in 2021 a Renault Traffic that had been converted to a small motorhome by the previous owner in 2020.

• The electrical setup includes a 12V auxiliary- gel battery which is charged via a solar panel (and its controller) as well as Citrix- ct Battery combiner (connected to 12v starter battery).
• The 12V auxiliary battery powers various LED lights, USB sockets, 12V cigarette lighter, and an inverter which powers a 240V compressor fridge. There are usually no other devices connected on the 240V circuit.

Up until 2023 all was working correctly but since then the fridge has problems turning on (mostly during the night) and it sets off the low-voltage alarm on the inverter. I am struggling to understand the reason why suddenly the fridge is starting to have issues when all was working fine before. The fridge works fine when the engine is running or if the van is parked in the sun and the solar panel charges the battery.

Here is the specification of the equipment used:

- Battery -12V 87.9Ah Gel Dyno europe Dgy12 -80ev

- Solar controller- Victron PWM Light Charge controller 12V-10A

https://www.victronenergy.com/upload/documents/Manual-BlueSolar-PWM-Light-12-24V-Charge-Controller-EN-A4.pdf

- Inverter 240V- Victron 12/500 VA (Continuous power 400W, Surge 900W)

https://www.victronenergy.com/upload/documents/Manual-Inverter-VE.Direct-250VA-1200VA-EN-NL-FR-DE-ES-IT-.pdf

- Fridge (240V compressor type) - Bomann BS389 42L 70W 84Kwh

https://www.manua.ls/bomann/kb-389/manual.

- Battery combiner- Victron Cytrix-ct 12/24-120

https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf

I have performed some measurements on the system to understand the source of the issues:
Fridge
Whilst the fridge was connected to the inverter in the van, I measured the inrush current and the continuous operating current using a clamp multimeter.

When the fridge is running normally it has an AC current of 0.2A and a 4A inrush current giving a power rating of 46W and 920W respectively (note the fridge is rated at 70W). For me the inrush current seems very high for a mini fridge, most articles I found on the web indicate that the inrush current is 4-10 times the rated current. In this case its around 20 times higher!

Could there be an issue with the fridge causing it to have such a high inrush current?

Just on this specific point .... The inrush current you are seeing is perfectly normal and nothing to worry about. Every single compressor fridge I have looked at and monitored have an inrush approaching that level (be they AC240V or DC12V).

Here is an example I recorded using a Victron 12/500 like you have with an AC Compressor Fridge. This video shows a peak of ~660W - I had seen higher than that also.


Also, I would have a check to see if the low voltage alarm point on the inverter is set a bit too high? When you have a momentary surge like for a fridge that only lasts 2-3 seconds, it really doesn't matter if the voltage dips lower than you might ideally like. The impact on the battery is nothing for that duration and setting the low voltage alarm to a low value might remove the issue? The default for the 12/500 is 10.9V with a shutdown of 9.3V. You could try lowering the 10.9V a tad? (probably need to connect a VE.Direct BT Dongle to change that setting via VictronConnect though).

However ... having said all this, your 12/500 Inverter is really too low a rating to run the Fridge you have due to the inrush current on compressor fridges. You will be in an overload condition each time it starts and likely get a bit of a thud and hum when it starts (the 12/500 Inverter is just a 400W device) which in itself is ok for the inverter as it is designed to cope with surges for short periods, but the overload peak is 900W which you are exceeding. I would look at switching this out for a Victron 12/800 Inverter which is rated at 1500W peak.
I ran the 12/500 fine on my fridge as per the video for a year or so as my running power and surge power was within the 12/500 capability, but your fridges compressor is more demanding. In fact, a couple of people running the same fridge as mine found the 12/500 would not always start the fridge so even this lower draw compressor was borderline on it. (At the time I bought the 12/500, the 12/800 model was MUCH more expensive. Now the difference is a lot less and I would get the 12/800 as a minimum to run a compressor fridge).

Battery
I purchased a battery tester and connected to the auxiliary battery. According to the battery spec the CCA at 0C should 600a with an internal resistance of 5.7mOhm. According to the tester the CCA is 188, internal resistance 13.6mOhm and the SOH is 10% whilst the battery SOC is 98%.

As I understand the battery is pretty much dead- 4 years after being installed.... According to the battery spec it should last 12 years!

Is this because the previous owner installed a gel battery directly to the main battery via a Citrix - ct battery combiner rather than using a DC-DC converter that provides the correct charging regime to the gel battery (like the solar controller) ? Should I replace then this equipment?

Other thoughts I had but so far discarded as everything worked in the past

• The inverter cannot support the surge current of 920W
• The wires between the battery and the inverter are too thin and are not of the minimum required AWG to support the current surge.

I am a bit of a loss at what to do next, and if I should:

• Replace the inverter with say a Victron/800 VA (Continuous power 650W, surge 1500W)

Yes, a good idea (see reply earlier)

• Replace the fridge (as its faulty)

No it isn't (see reply earlier)

• Change the wiring for a more suitable AWG.
• Replace the battery
• Replace the citrix ct battery combiner with a DC to DC converter such as this one: https://www.victronenergy.com/dc-dc-converters/orion-tr-smart-non-isolated

As these modifications are quite costly, I was hoping to get some advice before going any further. Thanks in advance for your support!

 

[chrispierre01]

I'd be surprised if the battery is getting 30A from the Cyrix-CT when the engine is running. It's basically a split charge relay, so the alternator can charge both starter and leisure battery at the same time when the engine is running. Usually the charge to the leisure battery is quite disappointing, which is why people upgrade to a B2B. You could check the amps with a DC clamp meter.

Also I'm sure the 200W solar is not giving its best with a 10A PWM controller. I think upgrading the controller to an MPPT 15A or even 20A would improve the yield quite a lot, and would be a simple swap.

If you're concerned about overcharging then you could get two gel batteries, and wire them in parallel to give one big 12V battery. That pair could be charged at 40A (20A per battery), with a bonus that you could last so much longer off-grid in a spell of dull weather. If you went for the lithium option I think you would also need to remove the Cyrix-CT and upgrade to a B2B.

So I checked the currents using a DC clamp meter. On a cloudy day with the battery at 14.09V (float mode) i was getting between 0.3A and 1A from the output of the solar controller and when I switched the engine on I was getting similar currents from the main battery, so as you mentioned there is very little charge to the leisure battery using the split charge relay.

I will look therefore look at replacing the Cyrix-CT with an Orion Tr-Smart 12/12V 18A 220W DC- DC converter to get 18A from the main battery and also upgrade the solar panel controller to an MPPT 75/15 Bluesolar to get up to 15A from the solar panels (it seems that the MPPT controllers are more efficient that the PWM ones). That should ensure that the battery gets enough current to charge sufficiently and also give the current battery the correct charge cycles.

I unplugged everything from the gel battery, and measured again the SOH with the battery tester and its coming in at 40% SOH. In comparison the starter battery is at 99% SOH even though its been in the van for over 5+ years now. So I guess a new battery is also in order.... I was looking at going for the Power Queen 100AH LiFePO4

Just on this specific point .... The inrush current you are seeing is perfectly normal and nothing to worry about. Every single compressor fridge I have looked at and monitored have an inrush approaching that level (be they AC240V or DC12V).

Here is an example I recorded using a Victron 12/500 like you have with an AC Compressor Fridge. This video shows a peak of ~660W - I had seen higher than that also.


Also, I would have a check to see if the low voltage alarm point on the inverter is set a bit too high? When you have a momentary surge like for a fridge that only lasts 2-3 seconds, it really doesn't matter if the voltage dips lower than you might ideally like. The impact on the battery is nothing for that duration and setting the low voltage alarm to a low value might remove the issue? The default for the 12/500 is 10.9V with a shutdown of 9.3V. You could try lowering the 10.9V a tad? (probably need to connect a VE.Direct BT Dongle to change that setting via VictronConnect though).

However ... having said all this, your 12/500 Inverter is really too low a rating to run the Fridge you have due to the inrush current on compressor fridges. You will be in an overload condition each time it starts and likely get a bit of a thud and hum when it starts (the 12/500 Inverter is just a 400W device) which in itself is ok for the inverter as it is designed to cope with surges for short periods, but the overload peak is 900W which you are exceeding. I would look at switching this out for a Victron 12/800 Inverter which is rated at 1500W peak.
I ran the 12/500 fine on my fridge as per the video for a year or so as my running power and surge power was within the 12/500 capability, but your fridges compressor is more demanding. In fact, a couple of people running the same fridge as mine found the 12/500 would not always start the fridge so even this lower draw compressor was borderline on it. (At the time I bought the 12/500, the 12/800 model was MUCH more expensive. Now the difference is a lot less and I would get the 12/800 as a minimum to run a compressor fridge).




Yes, a good idea (see reply earlier)

No it isn't (see reply earlier)

Yes this is a good point regarding the inverter, I did try the trick with the VictronConnect bluetooth dongle reducing the low battery alarm and reset on the inverter from 10.9V to around 9.5V and it didnt seem to make much of a difference unfortunately. I think it may have managed to get the fridge to start more times than previously but after 1 or 2 starts after dark and the voltage alarm was back on again and the fridge not starting at all until the morning.

What is strange is that has been working fine until recently, I always used to get the hum when the inverter starts with the lights flashing on startup but no overload error or low battery alarm that stopped the fridge starting up ok. Anyway I will potentially consider this upgrade as well if needed!

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[autorouter]

I will look therefore look at replacing the Cyrix-CT with an Orion Tr-Smart 12/12V 18A 220W DC- DC converter to get 18A from the main battery

Be careful not to confuse a DC-DC Converter with a DC-DC Charger. A DC-DC Converter is designed to output a steady fixed voltage, even if the input voltage varies somewhat. A DC-DC Charger is designed to take a somewhat variable DC source, and produce the correct charging profile for charging the selected type of battery. It will drop to a float voltage when fully charged to avoid overcharging. I think you should be looking at DC-DC Chargers.