Solar panel wattage

[The combat wombat]

I would like to fit a solar panel to my motorhome, so that we can keep the fridge running off battery power when we don't have a hookup. The fridge is a Waeco MDC65, but an older model, which has a power rating of 75W. from what I've seen, the duty cycle is about 20%, so I'm working on the assumption that it will draw 25w, or 2A.

Other electrics are water pump, gas-powered water heater and lights (soon to be replaced with LEDs). No idea what the pump draws, the water heater is about 0.250mA, Lights currently would be around 5A, but LEDs would be a lot less.

I was thinking of getting a 100w panel, connected to a 110Ah battery. Reckon that will be enough? Anyone have a similar setup? It would really only need to keep us going for 2 days.

Thanks

[pwhooftman]

75 watts 20% of the time is 6 A for about 5 hours a day = 30Ah per day (if you dont open the fridge often or its not hot outside!)
water heater 0.25A for say 4 hours = 1Ah per day
lights say 2A on Leds 3 hours a day = 6Ah per day
maybe some tv or charging your mobile = 3Ah per day, 40Ah per day in total, 80Ah for 2 days.

It's not advised to let a battery deplete more than 50%, so try to gain 25 Ah in 2 days.
100Watt panel will deliver around 50 Watts in average on peak time, 25 watts (2 amperes) in the morning & afternoon. It should be sufficient when its sunny in those 2 days, but If its cloudy or raining for 2 days, you have a problem.

My advice: run the fridge on gas. Its a very little flame, it could run on one bottle for months.

Fridges are normally wired to only run on 12V with the engine running for a reason..

[The combat wombat]

Thanks for the calculations. Unfortunately, it's a Waeco MDC-65 12v only fridge, no gas or mains option. I let it run after we left the campsite on Monday and it ran for about a day and a half before it dropped the battery below it's cut-out voltage and it was set to level 4 on the thermostat which was about halfway around. It could have been run colder, I'll need to see how cold it goes before the icebox no longer keeps the ice cubes solid!

A 100w Panel might be enough to give us two days, which is probably all we need. I'll also get the battery tested as I don't know how old it is and how much charge it is holding.

The newer version of the fridge is rated at just 45w, but we are not prepared to spend nearly £700 on a replacement. We'll make do with our Coleman extreme coolbox if we have to, as that will stay cold for 5 days without much issue, although it's on the large side and the best place to store it is in the shower!

[blizard]

We have also a MDC-65, it is a compressor fridge, far better than the gas ones. It can run also on 24v. The outside conditions (warm day)are also important of course
What kind of battery you have? A GEL or AGM you could discharge a little over 50%, but for a normal lead battery it is killing.
Wat solar charger are you going to fit? Some types have an additional dispay (like the fox) http://www.marlec.co.uk/product/fox-controllers/ so you can monitor the progress
These can also charge your starter battery and you can select all available types of batteries
This is not a MPPT charger but very good quaity PWM type.
I had this set, but changed everyting to Victron, so I sold it.

[blizard]

Please read this manual, it is for boats, but a campervan is quite the same
https://www.victronenergy.nl/upload/doc ... ted-EN.pdf

[The combat wombat]

What kind of battery you have? A GEL or AGM you could discharge a little over 50%, but for a normal lead battery it is killing.
Wat solar charger are you going to fit? Some types have an additional dispay (like the fox) http://www.marlec.co.uk/product/fox-controllers/ so you can monitor the progress
These can also charge your starter battery and you can select all available types of batteries
This is not a MPPT charger but very good quaity PWM type.
I had this set, but changed everyting to Victron, so I sold it.

I need to check the battery, as I don't know what type it is but I'm probably going to replace it anyway, as I don't think it's holding charge at the moment. It's rather difficult to tell at the moment, as someone has butchered the Power Management System and the wiring is a mess at the moment. Some stuff is wired into the leisure battery and some is wired into the starter battery, some is all wired into an inline fuse with scotch connectors, which is just unbelievable. I've ordered a new PMS and will be spending the evening and weekend tracing all the wiring and making sure that this time it's all connected properly! The replacement battery will probably be an AGM, but it depends what I can find on my budget, as I want a minimum of 110Ah and preferably higher.

I will most likely go for a 120W or 150W panel. MPPT controllers are so expensive, so I may go for a high-end PWM type instead. The dual sensing split charge relay I fitted will enable the panel to charge the starter battery, once the leisure battery is full, although I'm not sure what the controller will make of that setup.

[blizard]

Wiring in a campervan. Good to make a scheme how it is, and more important how you can improve it.
Normally only the driving electrics are hooked up on the starter battery, the rest om the additional one.
Solar charger: I have a Victron MPPT 75/15, and I"m happy with it, costs around £75, they have 5 years warranty now
Keep in mind whether you want to add more panels, you won't be forced to buy a new charger also.
And look if your build in 230v hookup charger (EBL)is suitable for the battery you are going to buy (lead, AGM or Gel)

[blizard]

The dual sensing split charge relay I fitted will enable the panel to charge the starter battery, once the leisure battery is full, although I'm not sure what the controller will make of that setup.

For that you can bypass the relay with an additional wire from the solarcharger to the starterbattery. The relay blocks power from that end. I asked the same question to Victron

[The combat wombat]

Wiring in a campervan. Good to make a scheme how it is, and more important how you can improve it.

The van came fitted with a plugin systems PMS5. Two of the fuse holders are missing and as they are soldered onto the board, can't be replaced. That was my first clue that something was wrong! Once I removed the panel, I found that someone had cut off half the wires at the back and wired them into a cluster, which appears to be connected to the starter battery. The panel also handles the 230v hookup and the wiring for the water heater was incorrect, so the neon light on the switch was always on and the switch was live in the off position, while it was off in the live position!

Normally only the driving electrics are hooked up on the starter battery, the rest om the additional one.

Yep, the only thing the starter battery should be connect to is the in-built charger in the power management system

Solar charger: I have a Victron MPPT 75/15, and I"m happy with it, costs around £75, they have 5 years warranty now
Keep in mind whether you want to add more panels, you won't be forced to buy a new charger also.
And look if your build in 230v hookup charger (EBL)is suitable for the battery you are going to buy (lead, AGM or Gel)

I'm probably going to go for a 150W panel, with that model of controller. That should be sufficient to keep the fridge going for a couple of days, without too much issue. I'm probably going to get a new AGM battery as well, but it's all down to budget. I need to correct the wiring, first, then worry about everything else. I've just bought the Sargent EC160 as this will fit in the existing hole, with only a minor amount of enlargement needed. It's not perfect, but it will at least give me a flush consumer unit as well as handle the 12v electrics and it has a built in charger when you are on a mains EHU.

The electrics shouldn't be over-complicated, I've got a multi-meter and so should be able to trace the wiring. As far as I'm aware, the 12v circuits are:
Water pump
Water heater (gas/mains powered)
Main light
Secondary lights & 12v sockets (I think they are on the same circuit)
Fridge
Toilet flush pump

If I can't get to the wiring, say on the main pump, I'll just disconnect stuff and see what stops working!

[blizard]

Ok, this Sargent EC160 is a solution of all your wiring problems, it is also a fuseboxunit I see. Good buy!
I don't see that the Sargent EC160 is capable of selecting a type of battery. If the charging voltage is to low, it will ultimately destroy a battery.
Of course this unit could detect it automaticly, but that's not mentioned either. A good charger has stages, ie a CTEK is a 7 stage charger, you could occasionally hook on to push the bank really full.
If you doubt I'dd go for a normal lead battery, witch fits in your bank. Half price.. Please take the time to read that Victron book Energy unlimited.

About power consumption: it is always increasing, 150W may be enough for now, maybe in 5 years you demand 400W... You can easally drop your energy consumption by changing your lights into LED, but the real drag is an inverter, for your electrical bikes to charge, or a nespresso...
And a generator is not everywhere appreciated.

[The combat wombat]

The Sargent is OK for managing the electronics, but as you say, not the best solution for charging the battery. I will invest in a multi-stage charger, like the Ctek in the future and use that when I have a EHU.

We like to keep things simple, so won't be using an inverter. We will not have a TV (we don't watch TV at home, so won't be watching it on the van!), or any other mains-powered equipment. We have a gas stove for making our coffee and cooking our food Phones can be charged on 12v and I've already replaced all the G4 Halogen bulbs with LED bulbs. The single biggest consumer of power is the fridge at around 2Ah, for which a 150W panel should be sufficient. I'd rather buy a well-known brand at 150w than some cheap eBay panel at 200W and with an MPPT controller, you get more charge per watt.

There is no heating in the van, but if we do want to use it in the colder weather, I will fit a propex heater, If I have the budget. They run on gas and use minimal power.

I have read that Victron book and I think for our power needs, a 150w panel would be enough to keep the battery charged for 2-3 days, But I can always add a second panel at a later date.

[blizard]

I think you are going to be ok, you thought it over.

We don't watch TV also, but I download a bunch of British detectives, and watch them.
So I ripped off the satellite disc to give room to the panels.

[blizard]

I found an interesting article explaining the difference between PWM and MPPT https://www.victronenergy.com/upload/do ... r-MPPT.pdf