Club 80-90 Forums

Hi,

I plan to add 24v to my camper and keep the house system separate. The main reason being is that 24v is more efficient (smaller cables and losses) and I already have a 24v victron inverter charger. I have calculated will probably need around 400 - 600 watt solar array to power my fridge 24/ 7 and a small radio/ laptop. Has anyone else tried this and/ or have experience of fitting 2 alternators to a t25.

oh heck, why complicate life
Mike

400w - 600w of solar panel? Have you got a football field sized space on your roof?
Well 1.5m x1.5m at £800+ import duty + controller? Say a round £1000 when all said and done for 400w.You won't get 400w from it for 24 hours though.That is the maximum. You do know that you don't get any power at night from a solar panel?
A 24v alternator will sap power from your engine also.
You will need very large battery capacity to run a fridge for the 18 + hours when you have no power from the solar panels or run the engine for the same time.
Is this a serious question?

I fear yes..
M

Oldiebut goodie wrote:You do know that you don't get any power at night from a solar panel?

Yes

leave it 12v fit a solar if thats your wish, whatever yoiu do you will not run the fridge on 12v as you wont be able to carry enough batteries use the fridge on gas or splash out on a compressor fridge (£500 ish) and then you can, losses re;12v/24v on our applications is not really a consideration,
appreciate your thinking but wouldnt go down that route
mike

Seems very elaborate for running a cool box.
Using electricity to heat elements to move amonia is ineficient
If you must use electricity..try thinking about using your stored\solar power better..
Like a compressor type fridge. A motor is better than an element.
I guess thats another expense you can add to the cost of this experiment

Cannot see the point at all! waste of time and money!

I want a system that is less reliant on a hook-up.

The fridge that came with the van is a Coolmatic RD40E compressor fridge with a Danfoss BD compressor currently running at 12v it might do 24v. At an outside temperature of 20°C and an internal temperature of 5°C the refrigerator has an average power of 11 watts per hour or about 1 amp per hour. In other words 24 Ah per day.

Let’s say the fridge was running at its maximum duty cycle of 50% this would give 12 Ah per day or 132 watt hours.
Hopefully I can convert the fridge to 24v if not I will use a 24v to 12v converter to charge the 12 battery and the rest of the 12 dc system. At 24v it would be 6 Ah per day

I already have a Victron 24v 800w inverter/ charger and 2 120AH deep cycle batteries. Taking in to account the fridge and 70% efficiency for the system - I have a spare 100Ah.
24V * 100Ah = 2400 watt-hours of battery capacity
Assuming 70% efficiency in the inverter and a typical 20" LCD TV using 45 watts....

2400 watt-hours * 0.70 efficiency) / (45 watts) = 37 hours usage
You don’t want to run a battery down 100% so 18 hrs real at 24v

2 x 200W 12v panels in series would allow me to watch my TV for 13 hours per day every day. This is taking into consideration 3 hours of sun per day and no sun for 2 days.

I never ever use hook up. 1x 110Ah leisure battery, 40w of solar panel, fridge on gas. Never needed hook up in 5 weeks away. Use the KISS principle - can't see why you want to use 24v and an inverter. There is very rarely a need for 230v in a van - just use 12v gear,12v tv if you must have one, 12v laptop adapter etc..
I have been wild camping for over 40 years and cannot see what you are trying to achieve by using 24v when you already have 12v! You are going to lose bu**er all voltage/efficiency on a 12v system in one of these vans due to the short cable runs and the use of adequately rated cabling. Due to the mobile nature of wild camping the engine is recharging the batteries on a regular basis anyway. Unless you stay in the same spot for weeks on end and annoy the local residents, which is something a true wild camper will not do.
The only advantage of the compressor fridge is if you are in continual high ambient temperatures such as in Spain.
Where are you going to safely mount these 2x200w solar panels?
Stay at home if you want to watch tv for 13 hours a day!
Just leave the system at 12v.

The TV was just an example; I have kids and a wife who like the odd luxury when away. Nintendo DS, mobile phones and laptop especially when away for extended periods.
If I do the calculation with 12v:
12V * 100Ah = 1200 watt-hours of battery capacity
1200 watt-hours * 0.70 efficiency) / (45 watts) = 28 hours usage or 14 hrs real usage.
In this case 24v is 1/3 more efficient.

Think you are making it too complicated, two 120Ah batteries in series is still 120Ah, two 120Ah batteries in parallel is 240Ah really the same capacity without the complication. Any marginal efficiency in 24v would be lost in the inverters.

bigherb wrote:Think you are making it too complicated, two 120Ah batteries in series is still 120Ah, two 120Ah batteries in parallel is 240Ah really the same capacity without the complication. Any marginal efficiency in 24v would be lost in the inverters.

But with 24v I can keep the current low.

Use a dc to dc step up/down converter not an inverter for phones/laptops/tv etc. If you are intent on wild camping try getting the kids off the need for electronic distractions. Just don't take them and let the kids discover the world outside of a little screen. My youngest daughter soon became adept at reading a map and relating it to the outside topography. Try it - you will be surprised at how much they will learn away from a little screen.

You are heading into a load of expense/grief for nil benefit going about it the 24v route.

The only people I know that use 24v already have that system in the base vehicle like buses and commercial vehicles and they have to do a lot of 24v to 12v converting for things. Luckily my bus was already 12v (20 seater Merc 508) - some were not.

These fellas are giving you sound advice. I can follow your logic on this but its soon lost once my cost calculator kicks into action and theres so much out there that will run happily from 12v or with only minor mods. I don't use mains hookup either. Far better to invest time and thought into making more conservative use of 12v by using LEDs throughout and buying stuff that was actually designed with making the best use of a 12v source to start with. Sadly too many manufacturers invest all their energies into design and functionality without committing any time to power consumption and its this end you need to look at. Certainly the really smart minds are in this area. Also agree on the getting out more approach otherwise you might just as well stay at home...

If its having enough juice that bothers you, carry a spare leisure that you charge before setting off? Don't knock yourself out trying to keep up with the Jones's, bring them down to your level (Quentin Crisp).