Another battery question..

[lufc71]

I always switch off the fridge (and all non-essential electrics) when the engine is not running. Would it be practical to not do this for a few hours, or would you recommend leaving the engine running while sailing for charging? Anybody know how long it takes to run the batteries down?
I'll be chartering a 44' Bavaria in a couple of weeks and was hoping to make better use of the fridge

 

[PetiteFleur]

I always switch off the fridge (and all non-essential electrics) when the engine is not running. Would it be practical to not do this for a few hours, or would you recommend leaving the engine running while sailing for charging? Anybody know how long it takes to run the batteries down?
I'll be chartering a 44' Bavaria in a couple of weeks and was hoping to make better use of the fridge

As long as there is a separate engine staring battery(which is usual on modern boats) it won't be a problem as when you start the engine the service batteries will be recharged. I still have the original Off:Batt1:Both:Batt2 setup and I alternate batteries on a daily basis and the fridge is quite happy overnight on one battery. I the recharge it the next day and repeat. Seems to work for me but if in a marina for more than one night I plug in the battery charger.

 

[noelex]

I always switch off the fridge (and all non-essential electrics) when the engine is not running. Would it be practical to not do this for a few hours, or would you recommend leaving the engine running while sailing for charging? Anybody know how long it takes to run the batteries down?
I'll be chartering a 44' Bavaria in a couple of weeks and was hoping to make better use of the fridge

The higher you keep the SOC of the batteries the longer they will last. 50% is often used as a cut off for maximimum discharge. There is nothing magical about this number, but it is a reasonable compromise between using the batteries and giving them a long life. Try and keep the discharge less than this.
The only really practical way of monitoring the discharge is with a battery monitor.

Most battery banks will have enough capacity to run a fridge , lights etc for 24-48 hours before the 50% limit is reached.

Most crusing boats without solar etc run their engine for about 2 hours once a day to keep up with the demand.
This varies a lot depending on efficiency of the fridge, charging system LED light etc. Charter boats tend not to be as well set up so typically need more engine time. This can be while motoring, motor sailing, or just at anchor.

If you run the house batteries down the engine will still start ok on the separate start battery fitted to most boats. I try treat all systems with some sympathy when I am on a charter boat, but the companies do budget for frequent replacment of the house bank because they are often run much lower than they should be.

 

[lufc71]

Thanks for the advice gents.

 

[Rivers & creeks]

Our good quality compressor fridge consumes an average of 1 amp and a continuous of 4.5amps. Even at double my average you will only need an hour's motoring to make up for it. It's all the lights you need to worry about, halogens and incandescent bulbs will consume huge amounts of juice, often 2 amps each bulb.

 

[VicS]

Some boat fridges ... at least the better ones ... will cut out when the battery volts fall below a certain value to prevent completely discharging them. They automatically cut in again when the battery is recharged

(Some solar panel regulators have the ability built in to do this too.)

 

[VicMallows]

On a charter boat you will have no idea as to the existing condition of the house batteries ..... only way to find out will be by trial. (Just make sure you keep the engine battery isolated and exclusively for starting the engine).