New Fridge/freeze conversion, consumption details and queeries / Solar panel?

[xeitosaphil]

After much work over the past few months I have now got most things working properly and have now managed to fire up one of last winter’s projects, the new Fridge Freezer cool box conversion. It is quite small ( about 35lts ) due to the amount of insulation provided, but will be suffice for my needs and hopefully the benefits of the extra insulation will be worth the reduction in volume.
Once down to temperature approx 30mins ( empty ), the freezer sits @ -7 Degrees C, the fridge goes down to +3 degrees C which is a little low but with more food in it, and a little more tweaking it may go a little higher. The Danfos BD 35 f cycles once every 30 mins and runs for 7 mins at a time. 4 mins @ 3amps and 3mins @2 amps – is this about right?

It is controlled by an air temp thermostat as recommended by the Tech guy at Penguin frigo Refridgeration.
If I have worked it out right on the figures above, it will use about 28 ah over a 24 hr period?However my ammeter doesn’t read milliamps’ so 3amps could be up to 3.9amps and 2 amps could be up to 2.9amps which could make the drain up to 38ah over a 24hperiod?
Having run it for 24 hrs it reduced my 220ah domestic bank from 86% to 70 % which I equated to 35ah (16%) rightly or wrongly, which could account for the difference between 28ah and 38ah based on the different possible ammeter readings.

Re charging the battery up again to 86% using the engine, it took 1 1/2hrs roughly @ aprox 1400 rpm with a 90A alternator / Adverc, only possible as I was attached to the berth with the engine in gear.

I thought this is not a scenario I could achieve if anchored somewhere, so I need to supplement my charging with a solar powered panel.

Having looked at panel out puts, would I be right in assuming that a 100w solar panel will probably give me aprox 5.5amp charge over a 6 - 7 hr period i.e. 35ah a day on a nice sunny day? This would offset the drain from the frdg/frzr and with another flexi panel of say 20w, may cope with most of the usual usage.

Would a MPPT 10A Solar Regulator be that much better than a PWM regulator and worth the extra expense?

I have put some links to a few panels which may be suitable but would be glad to hear of others if better suited or even cost less, one does have bi-pass diodes included so should have better performance with shading issues.
As Prices are about to rise I thought I would get in before they do. I also need to replace my existing Unisolar 11w flexible panel in front of the spray hood on deck as it is only showing 1.5v across the two wires so must be shot. Not sure whether to go with another flexi panel as mounting a fixed panel would be a problem with access to the boom when attending the Main, I did wonder if it would be possible to fix one in front of mast on coach roof but would rather not if possible as the cable length to the batteries would be in excess of 5mtrs.
Any comments gratefully received.

Solar panel links
http://www.ebay.co.uk/itm/100W-Mono...caravan-boat-NEW-/350556163623#ht_4116wt_1141

http://www.sunstore.co.uk/12v-100w-Monocrystalline-Solar-Panel.html

http://www.ebay.co.uk/itm/NEW-100W-...UK_Gadgets&hash=item3a81db1776#ht_4804wt_1018

The one I favour at the moment is the first link as it has bi pass diodes and seems to have reasonable guarantees and a sturdy frame as it will need to be fitted on the push pit on moveable fixings. It also says it is 18-19% efficient which seems to be better than the others, but I wouldn’t know how to determine it?

 

[William_H]

IMHO solar panels size is really dictated by what you are prepared to mount and put up with. They are big for the power they develop. 100w panel is pretty big and would normally require a gantry type of mounting. So I think cost of the panel is less rellivent than cost and inconvenience of mounting it.
You are right a 100 watt panel will produce 5 amps direct into the battery. But hat is under ideal sunshine. Typically 25 to 35AH per day. A mppt controller can get a little more current into battery so is worth buying. The fridge consumption is a very variable quantity from day to day depending on ambient temperature and amount of use.
I would not replace the small panel if you are going for a big panel. Unless you want it just for engine battery or similar.
So start with the question where will the big panel be mounted. That will dictate the physical size you can accommodate. Buy a panel accordingly. Then use the engine alternator as necessary under the actual circumstances at the time to keep the battery up. good luck olewill

 

[vyv_cox]

Your fridge/freezer is more efficient than mine, being half the size and better insulated, as mine is a standard Waeco 65 litre compartment but with a water cooled Danfoss BD 35 F compressor. Your consumption current is slightly lower than mine and operating period is less, although mine is operating in Greece where the ambient temperature is fairly high. I have 125 watts of solar panel, which is more than adequate in mid-summer but only just in spring and autumn. I have seen about 7 amps from the panels in the middle of the day, it is currently 0745 and the regulator is showing 1.7 amps.

 

[xeitosaphil]

IMHO solar panels size is really dictated by what you are prepared to mount and put up with. They are big for the power they develop. 100w panel is pretty big and would normally require a gantry type of mounting. So I think cost of the panel is less rellivent than cost and inconvenience of mounting it.
You are right a 100 watt panel will produce 5 amps direct into the battery. But hat is under ideal sunshine. Typically 25 to 35AH per day. A mppt controller can get a little more current into battery so is worth buying. The fridge consumption is a very variable quantity from day to day depending on ambient temperature and amount of use.
I would not replace the small panel if you are going for a big panel. Unless you want it just for engine battery or similar.
So start with the question where will the big panel be mounted. That will dictate the physical size you can accommodate. Buy a panel accordingly. Then use the engine alternator as necessary under the actual circumstances at the time to keep the battery up. good luck olewill

Hi olewil,
Thanks for your comments, I have given some thought to where I might mount the panel and come up with this location ( see photo). You will see from it that there are a couple of light weight davits that the previous owner had fitted which I have used in the past for my Avon Redcrest when port hoping on a daily basis, but which is stowed when passage making. I did wonder about mounting it on the top of those, but it would be a pain to mount and dismount all the time, and there is the storage of panel when not mounted for use to consider. So I came up with this location permanently fixed on the push pit with swivel brkts which allow it to fold down between folding ladder and rubbing strake when not in use, but lifted and supported by poles off the rubbing strake when used. I have also made provision in the brkts to be able to slide the panel to str/brd when using the boarding ladder, so hopefully have got all things covered.
You will also see from photo that there will be shading from the back stay which I am hoping the bi pass diodes will help with.
I know the panel is quite large and hopefully it will not look too out of place, but I can’t see any where else to put it and I don’t particularly want a gantry.
Will think about the MPPT controller as it would be good to get the best possible output from the panel.

Good to know my assumptions are ok, thanks.

 

[AngusMcDoon]

If in each hour you are running 8 minutes at 3 amp and 6 minutes at 2 amps your daily consumption in Ah is...

( ((8/60) * 3 ) + ((6/60) * 2) ) * 24

which is 14.4 Ah. Sounds a bit low.

 

[xeitosaphil]

Your fridge/freezer is more efficient than mine, being half the size and better insulated, as mine is a standard Waeco 65 litre compartment but with a water cooled Danfoss BD 35 F compressor. Your consumption current is slightly lower than mine and operating period is less, although mine is operating in Greece where the ambient temperature is fairly high. I have 125 watts of solar panel, which is more than adequate in mid-summer but only just in spring and autumn. I have seen about 7 amps from the panels in the middle of the day, it is currently 0745 and the regulator is showing 1.7 amps.

Hi Vyv,
Thanks for your feedback, I’m glad to hear that all the trouble I went to with regards to the insulation seems to be beneficial on drain and run times. The weather here though can’t really be compared to where you are in Greece!
Temp on fridge trial was approx 15 - 20c degrees during the day, I expect yours was closer to 25 - 35c degrees. I don’t think I can accommodate a 125w panel as the slide mounting would be a little unstable with the extra length, so will have to make do with a 100w and hope it copes.
Are you running with a MPPT controller or just a PWM?
Can you run two different panels of different wattage from the same controller and would they be affected by a shore based 240v intelligent battery charger. One other thing I did wondered about is, if you have two battery banks do you need two controllers or can you run both from the same one.

Do you have any recommends or views for either controllers, doesn’t need to be top notch as the load will only be 10 amps max even with the additional 20w panel if is needed.

It must be nice to wake up in the morning and have the sun shining every day! " Jealous or what "

 

[Phoenix of Hamble]

Your set-up is very slightly more efficient than mine too, so you aren't getting it too wrong!

One other observation..... -7 deg is a little too 'warm' for a freezer IMHO.... mine sits at about -15 deg

 

[xeitosaphil]

If in each hour you are running 8 minutes at 3 amp and 6 minutes at 2 amps your daily consumption in Ah is...

( ((8/60) * 3 ) + ((6/60) * 2) ) * 24

which is 14.4 Ah. Sounds a bit low.

" cycles once every 30 mins and runs for 7 mins at a time. 4 mins @ 3amps and 3mins @2 amps

14mins per hr = 8mins x 3amp and 6mins x 2amp
8mins x 3amps - 8 x 24=192mins@3amp=192/60=3.2hrs - 3.2hrs x 3amps = 9.6ah \
6mins x 2amp - 6 x 24=144mins@2amp=144/60=2.4hrs - 2.4hrs x 2amps = 4.8ah / Total 14.4ah

I worked it out quickly and obviosly got my sums wrong! not sure how you worked it out from your formular, but when I worked it out the long way round, I came out with the same answer as you.
I think in haste I doubled the amps useage along with the time over the one hour period which would account for twice the Ah useage amount calculated.

As said the ammeter doesn't read milliamps so the 3amp could be 3.9amps and the 2amp could be 2.9amp which would mean
3.2hrs x 3.9amps = 12.48ah
2.4hrs x 2.9amps = 6.96 ah Total 19.44ah


Only other thing is, as said battery was showing a 16% discharge from begining to end of trial which suggested to me a 35ah discharge or less dependant on the SOC of batteries to start with. If you were to say batteries could only give out say 200ah or less as they are not new, 16% of that would be 30-32ah / 24hrs = 1.25 -1.33ah per hour discharge.

Only thing I know is, the percentage discharge was right as observered and the time run and amperage rates were right as observered all be it they may be a little adrift as ammeter doesn't record milliamps. Bottom line is, I will just need a solar panel as big as I can fit to off set the fridge/freezer use, and I will have to monitor the amps usage in more detail when spending more time onboard in one period.

Thanks for taking the time to reply to thread

 

[xeitosaphil]

Your set-up is very slightly more efficient than mine too, so you aren't getting it too wrong!

One other observation..... -7 deg is a little too 'warm' for a freezer IMHO.... mine sits at about -15 deg

I know the freezer is a little bit warm @ -7deg, but unfortunately due to the fact I have a larger than it should be evaporator box ( due to the generosity of - l'escargot ) smashing Chap Thanks Mark, and the extra thickness of insulation,( I thought it better to be more efficient at the expense of a larger capacity ) if I turn the freezer compartment down any lower, the fridge will be frozen also. At the present freezer setting -7deg C the fridge is @ + 3deg C. The frozen stuff I put in the freezer still stays frozen and I am hoping that the fridge once loaded with more food will rise to maybe +4-5 deg C.
This is a fantastic improvement on the original cool box installation that was originally fitted to the boat back in the 1970’s as it had no insulation to speak of, ( 6mm of polystyrene ) and no refridgeration at all. So the new one has had to be a little bit of a compromise but I am very pleased with the results so far and it has all fitted in and looks nice, it looks like it has always been there.

Many photos available of the instalations etc if anyone is interested.

 

[AngusMcDoon]

I know the freezer is a little bit warm @ -7deg...

Some guidance here about what you should expect for a freezer at -7...

European freezers, and refrigerators with a freezer compartment, have a four star rating system to grade freezers.

[∗] : min temperature = −6 °C (21 °F). Maximum storage time for (pre-frozen) food is 1 week
[∗∗] : min temperature = −12 °C (10 °F). Maximum storage time for (pre-frozen) food is 1 month
[∗∗∗] : min temperature = −18 °C (−0 °F). Maximum storage time for (pre-frozen) food is between 3 and 12 months depending on type (meat, vegetables, fish, etc.)
[∗[∗∗∗] : min temperature = −18 °C (−0 °F). Maximum storage time for pre-frozen or frozen-from-fresh food is between 3 and 12 months

Although both the three and four star ratings specify the same storage times and same minimum temperature of −18 °C (−0 °F), only a four star freezer is intended for freezing fresh food, and may include a "fast freeze" function (runs the compressor continually, down to as low as −26 °C (−15 °F)) to facilitate this. Three (or fewer) stars are used for frozen food compartments that are only suitable for storing frozen food; introducing fresh food into such a compartment is likely to result in unacceptable temperature rises.

 

[xeitosaphil]

Some guidance here about what you should expect for a freezer at -7...

European freezers, and refrigerators with a freezer compartment, have a four star rating system to grade freezers.

[∗] : min temperature = −6 °C (21 °F). Maximum storage time for (pre-frozen) food is 1 week
[∗∗] : min temperature = −12 °C (10 °F). Maximum storage time for (pre-frozen) food is 1 month
[∗∗∗] : min temperature = −18 °C (−0 °F). Maximum storage time for (pre-frozen) food is between 3 and 12 months depending on type (meat, vegetables, fish, etc.)
[∗[∗∗∗] : min temperature = −18 °C (−0 °F). Maximum storage time for pre-frozen or frozen-from-fresh food is between 3 and 12 months

Although both the three and four star ratings specify the same storage times and same minimum temperature of −18 °C (−0 °F), only a four star freezer is intended for freezing fresh food, and may include a "fast freeze" function (runs the compressor continually, down to as low as −26 °C (−15 °F)) to facilitate this. Three (or fewer) stars are used for frozen food compartments that are only suitable for storing frozen food; introducing fresh food into such a compartment is likely to result in unacceptable temperature rises.

Thank you Angus,
I will print that off it will be a great help and a useful source of info for future reference.

" Maximum storage time for (pre-frozen) food is 1 week " that will be all I require as it is so small anyway, so great.

" introducing fresh food into such a compartment is likely to result in unacceptable temperature rises ". I have fitted two digital thermometers to monitor temperatures in the two separate compartments so I can keep an eye on this possible situation, although I hadn’t thought till now how useful a manual override switch may be to bypass the thermostat.- Maybe an upgrade for next winter if I find I need it.

 

[geem]

You may find your run time reduces when you will the fridge/freezer, once it is all cooled down. Also, if you want to reduce the cooling effect in the fridge, you could apply a little closed cell foam to the evaporator to reduce the cooling effect into the fridge compartment. This worked on my last set up.

 

[xeitosaphil]

You may find your run time reduces when you will the fridge/freezer, once it is all cooled down. Also, if you want to reduce the cooling effect in the fridge, you could apply a little closed cell foam to the evaporator to reduce the cooling effect into the fridge compartment. This worked on my last set up.

Thats what I was hoping would happen once I started to fill it, thanks for the tip of isulating the evaporator will leave that as an option at this stage but good to know it works.

 

[vyv_cox]

I have two panels, 80 and 45 watts, connected in parallel and controlled by a Sunworks PWM regulator. It isn't the cheapest option but it controls two battery banks. It's a 9 amp regulator but it gets pretty warm at midday with around 8 amps going through it.

My battery charger is connected directly to the batteries but it receives very little use.