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240v fridge and freezer power

We are considering buying a boat that has separate 240v fridge and freezer. The boat has a1600 inverter and 4 110 Ah batteries to run these when not on shore power. I need to know wether this is a suitable set up for a boat that will largely cruising or moored away from power supply for days at a time?

Asked by: Kevin Cracknell  | 2.31pm, Monday 17 March


WW says:

The simple answer is- if you are cruising, then yes it should be fine! If you are going to spend long periods of time moored up, with little or no engine running, then probably not.
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Assuming *(as from energy efficiency labels) that a modern fride or freezer, around 4 cuff, uses around 180kWh (or units) of electricity each, that is around 1kWh per day- which is around 83Ah of battery capacity per day.
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However, the inverter is not 100% efficient, and will be consuming current even in standby mode- so, taking into account the current in inefficiencies, you would be looking more at around 100Ah per day of consumption, give or take (depending on the temperature, settings and inbuilt efficiencies of the fridge and freezer).
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As you will have a battery bank (whehn it was new) of 440Ah, and the fact that you can really only utilise around 40% effective of the battery bank, you would have around 200Ah to play with. Assuming no other appliances were running, this would give you about 48h of time running the fridge and freezer before the battery levels were depleted to the point of being effectively "flat".
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You could increase the effective battery capacity by utilising an advanced alternator charge controller, which might increase both the effective capacity, as well as recharge rate of the system when running the engine.
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Alternatively, you might be able to offset the consumption with solar or wind generation. A panel of around 200W might, in summer, feed back in around 50Ah a day, which would then massively increase your useable battery bank capacity- but at other times (overcast/rain/winter) it may only provide a small proportion of the required power.
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Increasing the ventilation around the fridge and freezer (possibly from the cabin bilge) will help reduce power consumption.
Hope that helps. Let us know if we can be of more assistance.
Mark

Mark Langley  | 4.19PM, Monday 17 March

Fridges and freezers that run on battery power directly are more efficient than their mains powered equivalents, mainly due to better motors. This coupled to the power saving from not running an inverter 24/7, will give a reduction in battery drain. However the appliances are considerably more expensive as it is a niche market, which is why people are tempted to fit mains powered units.

Rupert Smedley  | 4.56PM, Monday 17 March

The time taken to recharge batteries is very difficult to estimate. Standard alternators will reduce the charging current quite rapidly, whilst advanced charging with an alternator controller will reduce the charge time and put more power into the batteries.
It is probable that you will replace the bulk of the charge into the batteries within a couple of hours; however to ensure good battery life it is important to recharge them thoroughly as often as possible. This is where solar panels come into their own, as they trickle charge constantly during daylight.

Rupert Smedley  | 5.07PM, Monday 17 March

With some alternator controllers, it is possible to combine the outputs of two alternators, and then have a twin output into the domestic and the starter battery banks
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This has the advantage of increasing the charging rate- often the alternator that is solely for recharging the engine starter battery has very little work to do, while the one tasked with feeding the domestics can be overworked.

Mark Langley  | 8.03PM, Monday 17 March


Readers say:

Thank you, I believe this boat has two 60 amp alternators, can you estimate the number of hours the engine would need to be run to recharge the battery bank?

Kevin Cracknell  | 4.54PM, Monday 17 March

Thanks very much for all the replies.

Kevin Cracknell  | 2.20PM, Tuesday 18 March

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