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Gordon

Battery Charging

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I am looking for some kind of charging system for my fridge battery (Waeco compressor)  I initially had the Waeco power supply that automatically switched over to battery when not on shore power. This was more trouble than it was worth  due to a small but significant voltage drop in the switch when on battery.  I am at present connecting a portable intelegent car battery charger when on shore power, a good system but a pain to connect. I am looking for something a bit more permananant.  There are a number of intelegent chargers, 4 stage chargers and loads of intelegent chargers that claim to be for leisure batteries in boats and motorhomes. Any reason why any of these would not be suitable. I am concerned that if these were permanantly connected to the battery but the shore power not on they would cause a drain on the battery due to their detection circuitry. A five amp unit would be plenty large enough  Your thoughts please

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I have used CTEK chargers to maintain battery backup on critical safety systems and would say it is excellent equipment. ( Although I have been retired for quite a while now)

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We have a CTEK M100 charger on our 2-battery system and it has performed flawlessly.

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Thanks Guys for the swift answers  Yes I have heard good things about ctek chargers and maybe worth getting over those  that are about half the price

 Three questions now please  What if you have one connected without shore power ie if the post trips over winter Would there be a current drain, The Ring intelegent car charger I use certainly does draw a bit and leds light. In fact I would not expect to leave it powered over winter Healthy leisure batterys can easily cope with a few months idle

Secondly Spider, You said you use an M100 on a two battery system I am assuming you mean a pair of batterys in parrelel rather than two banks. I intend to address the issue of the domestic battery once the fridge is sorted.

What is the difference between the CTEC marine chargers and the others. Marine ones are twice the price (normal boating issue) I am guessing the only difference is they are waterproof. If that is an issue in my case I would have a lot more than a flat battery to worry about

I am guessing a 3.8amp one would be adequate as although the fridge draws a tad more than that the off cycle of the fridge will give adequate time to catch uo

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Not sure the 3.8 amp will be enough. In theory yes but in the last three days heat my fridge has run almost flat out!

It's also likely that as both your fridge and battery age one will demand a little more power to maintain your ice cold drinks just as the other is able to offer a little less due to reduced performance. 

A battery charger running at full capacity all the time may not last as long as one having an easier life. 

Your question about 'marine quality' is interesting though. I would expect something marine to use stainless or non corrosive fittings, tinned wiring, able to function in extremes of temperature in an engine bay for example  and be waterproof!

I am not sure whether we have an industry standard for 'marine' and it seems anyone can stick a piccy of a boat on their packaging and print marine next to it.

Best to keep to well known brand names for a better chance of a quality product? 

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54 minutes ago, Gordon said:

Secondly Spider, You said you use an M100 on a two battery system I am assuming you mean a pair of batterys in parrelel rather than two banks. I intend to address the issue of the domestic battery once the fridge is sorted.

Yes in parallel, sorry should have been more specific.

Wise words from JanetAnne!

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Hi Gorden The sterling four stage charger i  use with my Waeco fridge works fine not cheap but if i disconnect the shore power it then supplies  240 volts from batteries but if i switch this off the fridge automatically switches over to batt power which is charged by solar when engine not running. you do need at least a 50 amp wire or larger from the battery to the fridge depending on distance from battery all connections need vaseline or simmerler to prevent corrosion in the marine environment. this is why marine is more cost easily, shown when comparing with cookers for caravans and the identical marine one often double the price of land based one.The fridge shouldn't use more power on 12 volt then 240 volt providing the size of cable is adequate, if shore power is available to run a charger why charge a battery to run the fridge which will run on 240 volts as well as 12 volts, by all means have a separate 12 volt supply to fridge, but if the battery doesn't last/ runs flat and fridge stops working you eatheir have a duff battery or not enough batteries.   to run a fridge between battery charging solar is often the answer as more sun/and heat more power used and supplied for free, solar could also work out cheaper than a 4 stage battery charger which you need if connected to the batteries 24/7 and with the added ability to maintain your batteries fully charged when boat not being used and allow them to last longer.  John

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Thanks John   I suppose Marine must also be capable of dealing with sea and salt  Most of the connections on everything else on a broads cruiser are not anything special and corrossion has in my experience has been limited to the very rare switch contact.

The fridge is 12/24 volt only it has no mains option, I did fit the Waeco power supply which ran the fridge from shore power and switched over to battery if the mains was disconnected, this was a dissapointing device as it presented a voltage drop to the 12V supply causing the fridge to cycle unnecessarily, removal of this gave much better 12 Volt operation.

As for adequacy of the cable or battery, I have replaced every connector and switch and the volt drop is neglible, as far as battery capacity is concerned, yes it is only a single 110Ah, the domestic is a parallel pair and for the little demand on the domestic side of things I have I could swap them over, but that in itself is not a simple job and would increase cable runs and joints. One fridge battery is adequate generally but on temps like we have had it could give little more than a day  I am looking to something that could help it to run in the marina for a a few days and keep the battery charged at the same time  On the same vein we often    may use the battery for a couple of days and then travel only  a short distance only say Womack to Potter or St Benets to Ranworth, Something like the CTEK would be perfect on that score . I have considered Solar and am still thinking about it but it would be way ott for my needs and far to costly to justify against the cost of a 3.8 or 5Amp charger.

I am not particularly worried about conditioning over winter either in my experience a healthy leisure battery loses nothing in a few months.

I guess I will be able to see if the charger causes any drain if the post trips out using an Avo if not I will leave it giving its TLC over winter, if it does I can always switch the output  Thanks for your interest and helpful reply

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3 hours ago, JanetAnne said:

Not sure the 3.8 amp will be enough. In theory yes but in the last three days heat my fridge has run almost flat out!

It's also likely that as both your fridge and battery age one will demand a little more power to maintain your ice cold drinks just as the other is able to offer a little less due to reduced performance. 

A battery charger running at full capacity all the time may not last as long as one having an easier life. 

Your question about 'marine quality' is interesting though. I would expect something marine to use stainless or non corrosive fittings, tinned wiring, able to function in extremes of temperature in an engine bay for example  and be waterproof!

I am not sure whether we have an industry standard for 'marine' and it seems anyone can stick a piccy of a boat on their packaging and print marine next to it.

Best to keep to well known brand names for a better chance of a quality product? 

Thanks for the reply  Yes I tend to agree that it would be worth the extra few poinds to go for the 5 amp hence I have been convinced that CTEK is the way forward, seems to get a good press in both the boat and car/bike world.  I assume that if CTEK say marine it is at least designed for the job, but I suppose its really only relavant if you go salty.   Thanks for your reply and help

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5 hours ago, Spider said:

We have a CTEK M100 charger on our 2-battery system and it has performed flawlessly.

Do you know if it causes any issues if the mains is disconnected for an appreciable time ie if left over winter and the elctric post trips  As they do

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We've not had any issues, the charger has simply restarted when the power is reconnected, although the longest power has been disconnected is only a couple of weeks.

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We have gone down a slightly different route. Our compressor type fridge is 12volt and draws around 3 amps (a bit more at start up) which  is supplied by two 110aH domestic batteries. We have a 100w solar panel and MPPT controller that charges the batteries all the time when there is sunlight. Given that the fridge does not run all the time the solar panel will keep up with the consumption of the fridge. I did not want to fit a built in charger to run on shore power since it is only the fridge that draws any large degree of power so I made a panel that has a 10amp rated double pole break before make change over relay and a 240v to 12vDC power supply fed through a double pole fused isolator. As soon as the shore power is plugged in (assuming that the isolator is switched on) the power supply will start up, power the relay and switch the fridge over to the power supply output. Disconnection the shore power or switching of the isolator resumes the battery feed to the fridge.

Because our fridge is in an enclose space with little space around it there was little if any air flow to allow the evaporator to lose the heat generated when the compressor was running, in hot weather it was running most of the time which is neither good for the fridge or current consumption. To combat this I made a thermostatic controlled computer fan positioned behind the fridge to blow onto the compressor and evaporator when the temperature in the cavity reaches a certain temperature and continues to run until the temperature reduces again. This made a tremendous difference to the operation of the fridge reducing the duty cycle and therefore current draw even on the hot days that we have see this year.

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Interesting approach, Fan idea is interesting I may go down that route

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Fan is good to move the heat I've got one on the rear of the fridge in the garage for that reason and now we've stopped getting the alarm beeping.

I' have a Ctek 3.5A on a pair of 7Ah blocks on my bench which comes on every Saturday to ensure the blocks are topped up over winter.

I have a Ctek 5A on the 130Ah block which runs the garden lights but that has a 100W solar panel which tops it off on a Saturday over winter. (why Saturday because it was my free electric day with Brit Gas)

No issues with Ctek we used them on our large gen sets.

I was in the mancave Saturday and both went stright to green on power up which they should do.

5 year old 100w panel still gives 4 amp on full charge, Need to replace with a new pair - research required.

 

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6 hours ago, StillCruising said:

 

Because our fridge is in an enclose space with little space around it there was little if any air flow to allow the evaporator to lose the heat generated when the compressor was running, in hot weather it was running most of the time which is neither good for the fridge or current consumption. To combat this I made a thermostatic controlled computer fan positioned behind the fridge to blow onto the compressor and evaporator when the temperature in the cavity reaches a certain temperature and continues to run until the temperature reduces again. This made a tremendous difference to the operation of the fridge reducing the duty cycle and therefore current draw even on the hot days that we have see this year.

Now that is interesting, my fridge has plenty of ventilation but when the weather is hot the boat is hot and so is the ventilation space. 

Any chance of a components list / schematic? 

 

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Fans can make matters worse if there is inadequate ventilation

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There has been some interest in my fridge cooling fan. The final design evolved from several unsatisfactory attempts mostly concerning the amount of air gap behind the fan restricting the flow and the positioning of the fan with relation to the back of the fridge. I did make a few notes in my book at the time so I have typed them up as a rough spec for anyone that may be interested. The fan and digital controller are available on e-bay very cheaply. It would be OK to not have the thermostat and run a fan all the time as they take very little power but at night when the temperature has dropped it is not really needed and as we sometimes use the seat in the saloon as guest bed the, whirring of even a quirt fan can be obtrusive in the still of the night. The controller has a thermocouple and I found that it was best to position this out of the air flow, in fact it is now positioned beside the fan as in the photo. Setting the on and off temperatures did require some experimentation and would obviously vary dependent on particular installations.

The 12v feed from the fan is taken via a small line fuse from the supply line to the fridge so that it runs either off the battery or the 12 power supply when on shore power.

I am considering adding a second fan next year to give more air flow over a bigger area. 

 

Fridge Fan Materials & Construction

80mm 12volt Computer Fan x 1

20mm x 25mm wood batten as required

Digital Thermostat x 1

Plastic Spacers 35mm x 4

Terminal Block x 1

P Clips x 2

Screws as required

 

Constraints that I worked with:

The assembly cannot extend more than 80mm from the wall to give a reasonable air flow gap to the evaporator on the back of the fridge of approx 100mm.

To achieve full airflow the back of the fan must be unobstructed, experimentation suggests 55mm min so 20mm wood thickness + 35mm spacers used

Fan must run only when the air temperature behind the fridge rises above an acceptable level. (to be determined)

Fan must continue to run until the temperature drops to an acceptable level (to be determined.

 

I hope this all makes some sort of sense, PM me if you want any other info.

 

P1080652.JPG

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Yes you do need adequate ventilation around a fridge and the space and gaps requirement around a fridge is part of the spec. That said there are many electric compressor fridges on old boats that have been fitted as replacements for old gas fridges using the same aperture (as ours was) that are close  to or  fall a bit short in the ventilated area. As installed (before we bought the boat) our fridge has always worked OK in 'normal temperatures but on very hot summers days has really struggled virtually running all the time as it just could not get rid of the heat fast enough. Our fan just supplements the naturally occurring air movement and believe me it has made a big difference to the efficiency of the fridge.

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It often helps if the air flow to the base of the fridge comes from the bilges as this is much colder than cabin air temperature, as is often said ventilation ,ventilation. John

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Thanks for all your suggestions I have on the basis of these and other research bought a CTEK MXS5

Experiments with a leisure battery have answered the two questions I had

Does the charger draw any current from the battery when the mains is off. i.e if the power tripped in the winter. Yes it does but its only 300 micro amps. Back of fag packet maths suggests unless I ran out of fingers in the sums it would take about 4 months to take 1Ah. More than willing to be corrected on this.

The second question is that  there are a number of selectable modes for the charger, what would happen on a mains flick. Good news is  it defaults to a normal charge mode, although I dont believe it would matter where it restarted.

Not sure what would happen if the engine was started with the charger conncted but am pretty confident it would at worst confuse the CTEK .

Pretty confident this is the answer to my needs.and give me much more flexibility than the Waeco power supply gave particularly the ability to charge the battery as well. I may even after trialling it for a bit get one for the domestic bank although I have no issues with that, Just got to get down there and fit the thing to the boat.

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