Battery Chargers

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CalicoJack

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We have a very power hungry fridge which wants about 5 amps per hour. Currently we are using a 4 amp charger which helps but can't keep up; it's alright most of the time because the fridge trips out when it gets cold enough and gives the charger time to catch up, however, when it's really warm the fridge never gets cold enough to trip out for long enough to allow the charger to catch up.

I thought that the easiest answer was simply to buy a charger with a bigger capacity and so went to Halfords and saw one which was a smart charger with an output of 12 amps and the capability to trickle charge once the battery is full. Good so far, however,....

The chap in Halfords was concerned that I could end up either overcharging the battery, or destroying the charger, because the charger was never designed to work whilst the battery was being drained at the same time as it was being charged. He felt that the charger would carry on charging at 12 amps even when the battery was at full charge.

I have no idea whether he is correct can you help. The battery is a ( wet) standard 110 amp leisure battery.
 
CalicoJack said:
The chap in Halfords was concerned that I could end up either overcharging the battery, or destroying the charger, because the charger was never designed to work whilst the battery was being drained at the same time as it was being charged. He felt that the charger would carry on charging at 12 amps even when the battery was at full charge.

I have no idea whether he is correct can you help. The battery is a ( wet) standard 110 amp leisure battery.
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You don't say which make/model of charger you were considering, but it's highly unlikely to damage either the battery or itself. It certainly wouldn't be able to keep pumping 12A into a fully-charged battery! If in doubt, ask the charger manufacturer.
 
CalicoJack said:
We have a very power hungry fridge which wants about 5 amps per hour. Currently we are using a 4 amp charger which helps but can't keep up; it's alright most of the time because the fridge trips out when it gets cold enough and gives the charger time to catch up, however, when it's really warm the fridge never gets cold enough to trip out for long enough to allow the charger to catch up.

I thought that the easiest answer was simply to buy a charger with a bigger capacity and so went to Halfords and saw one which was a smart charger with an output of 12 amps and the capability to trickle charge once the battery is full. Good so far, however,....

The chap in Halfords was concerned that I could end up either overcharging the battery, or destroying the charger, because the charger was never designed to work whilst the battery was being drained at the same time as it was being charged. He felt that the charger would carry on charging at 12 amps even when the battery was at full charge.

I have no idea whether he is correct can you help. The battery is a ( wet) standard 110 amp leisure battery.
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My Ring Smart charger goes into recondition mode if any significant load is applied to the battery while it is operating. I have not left it on to see what would eventually happen.

I think most, if not all, the Ctek chargers can support a load while charging. If I was you I would look at the higher rated Cteks . See http://www.ctek.com/gb/en/chargers

Leave the Halfords chargers for someone who wants one for charging his motor car battery.
 
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pvb said:
You don't say which make/model of charger you were considering, but it's highly unlikely to damage either the battery or itself. It certainly wouldn't be able to keep pumping 12A into a fully-charged battery!
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I agree with PVB. Provided the charger is good quality, so not prone to over-heating, and rated at more than the constant drain from the fridge + anything else to give some headroom, it should be fine. My boat spends a few weeks a year on shore power with the fridge running 24/7 and the charger is fine. I guess that for liveaboards this situation would apply for months on end.

Richard
 
The fridge either uses 5 amps or it doesn't. Per hour doesn't add anything, though if you used 5 amp hours per hour as an average that would make sense. In any case, this is going to be a lot to deal with and maybe improving the system might be more effective. It is the heat losses that need to be taken into account, so a well-insulated fridge, however large or inefficient its mechanism, will use less power than one with less insulation.
 
CalicoJack said:
The charger that I was looking at in Halfords was a Ring.
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Yes i bought mine in Halfords... a good few years ago so the range has changed several times since and the prices have rocketed.

It was a bit of an impulse buy when halfords had them on special offer ( could still have shopped around and got it much cheaper though) Not bought for the boat .... just so as i had a modern automatic charger to use at home.

I am happy with it for the uses I bought it for but I don't regard it as a quality bit of kit and I know it wont do what you want to do.

I guess you have looked at this one.
No idea if it will do what you want.... probably not if it behaves like mine !
mainimage.jpg
 
Having had the caravan built in power supply fail I have looked into this problem with serious interest this week. Having read the online instructions for many chargers many are not intended for use as continuous power supplies. In the end I chose a unit designed to act as both a power supply and a multi stage charger.
 
My Ring 16 does the same as VicS'.

For a robust setup on your boat I'd map out your combined consumption, calculate amp needs and then talk to providers of chargers made for the purpose (Sterling, Mastervolt, CTec, Victron, Xantrex etc.)

Might cost more but will give the desired result and peace of mind.
 
One question no one has asked... Your 5 Amps fridge load, is that constant (i.e. Peltier effect fridge) , or is it a compressor fridge averaging 5A? If the latter, the compressor running draw will be a lot higher than 5A... MY Waeco CF 18 runs for about 8 minutes an hour at about 5A so that's a consumption of 0.7AH... On a similar cycle for this fridge it would be peaking north of 30A... Which is almost like running glowplugs for that period.

So if its a Peltier fridge, change it for a compressor one...
 
maxi77 said:
Having had the caravan built in power supply fail I have looked into this problem with serious interest this week. Having read the online instructions for many chargers many are not intended for use as continuous power supplies. In the end I chose a unit designed to act as both a power supply and a multi stage charger.
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Spi D said:
My Ring 16 does the same as VicS'.

For a robust setup on your boat I'd map out your combined consumption, calculate amp needs and then talk to providers of chargers made for the purpose (Sterling, Mastervolt, CTec, Victron, Xantrex etc.)

Might cost more but will give the desired result and peace of mind.
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I agree with these guys, get the proper tool for the job. My fridge is on 24/7 and in this weather the Eberspacher is too. I have a Sterling Pro Charge Ultra and it keeps the batteries charged whilst constantly running whatever i have turned on.
 
I don't understand why this appears to be out of the ordinary problem to anyone. If you are running your engine and using current drawing devices, provided your alternator has a greater output than is being consumed, the battery will be kept charged and you are all quite happy to accept this as normal. Switch of the engine and replace the alternator with a battery charger of suitable amperage and it becomes an issue. Why?
 
myquest said:
I don't understand why this appears to be out of the ordinary problem to anyone. If you are running your engine and using current drawing devices, provided your alternator has a greater output than is being consumed, the battery will be kept charged and you are all quite happy to accept this as normal. Switch of the engine and replace the alternator with a battery charger of suitable amperage and it becomes an issue. Why?
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Because not all modern multistage "smart" battery chargers will support this. A battery charger merely intended for automotive use is the least likely to support it as those of us with Ring Smartchargers already know.

The Ring suddenly seeing an increase in current demand thinks, "whoa, something wrong here" and puts itself into "recondition mode".

A charger designed to support power supply is programmed to supply the extra current while maintaining the same voltage output.
 
myquest said:
I don't understand why this appears to be out of the ordinary problem to anyone. If you are running your engine and using current drawing devices, provided your alternator has a greater output than is being consumed, the battery will be kept charged and you are all quite happy to accept this as normal. Switch of the engine and replace the alternator with a battery charger of suitable amperage and it becomes an issue. Why?
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The performance of an engine's alternator is quite simple. The regulator will cut the charging off when voltage reaches a cut-out level regardless off the capacity (amp) fed into the battery. Take a starter battery: When charged to 100%, starting a williilng engine takes seconds and hardly vcan be seen on capacity. The alternator rapidly restores to 100%.
If by consumption the starting battery is down to eg. 60% that alternator will work, but mistake the raising voltage and cut out before 100% capacity has been reached - regardless of running hours. Such deep discharges btw is the big killer for batteries (less so for types designed to tolerate the 'abuse').

If charging by a charger with a different charging control, the regulation is different. Old fashioned chargers will charge and reduce while full, but never stops completely hence will push the capacity to it's limit - and if not turned off might boil the liquid into evaporation.
A modern charger, the so called intelligent types, will charge and monitor progress, then executes a predefiend number of stages (som a few, others many) to ensure the fastest, careful, 100% rebuild of capacity possible. This of course takes an undisturbed run through all stages (ie. they do not like consuming devices to 'interfere').

Dedicated on-board charging systems will provide the best of all properties. Commonly capable of charging more battery (banks) separately by managing these in 'channels'. If required, such equipment will supply whatever consumers you have and and the same time perform intelligent maintenance of the batteries.

All IMHO, ya know.
 
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Spi D said:
The performance of an engine's alternator is quite simple. The regulator will cut the charging off when voltage reaches a cut-out level regardless off the capacity (amp) fed into the battery. Take a starter battery: When charged to 100%, starting a williilng engine takes seconds and hardly vcan be seen on capacity. The alternator rapidly restores to 100%.
If by consumption the starting battery is down to eg. 60% that alternator will work, but mistake the raising voltage and cut out before 100% capacity has been reached - regardless of running hours.
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Sorry, but that's utter bollocks. If you don't understand electrics, you really shouldn't be posting advice here.
 
Spi D said:
Sorry but document your statement.
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Almost don't know where to start! All an alternator regulator does is regulate, ie it controls the max voltage the alternator can produce. It doesn't ever "cut the charging off" as you've claimed. During charge, the charge current gradually tails off as the battery's state of charge increases. Effectively, this is because the difference between the regulated charge voltage and the battery's own voltage reduces as the charge state increases (and in simple terms it's the difference in those voltages which affects how much charge current can be pushed into the battery). Because the charge current reduces as the battery approaches full charge, getting it up to 100% may take some time, but it will inevitably reach that level, because the regulator can't "mistake the raising voltage and cut out before 100% capacity has been reached".
 
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