Fridge and electrics

[Chubb41]

Hi all

 I’m looking for some help I’ve got a dawncraft  and I’m at the stage of putting electrics inside at the moment I have just the one battery to start the engine I believe I need to leisure batteries and inverter I will need power for fridge TV and charge points  I am a mechanic so the engine side I’m okay with basic wiring but unsure what inverter fridge etc to buy 

thanks Chris 

[Alan de Enfield]

The first questions are not 'off topic' but very relevant  to give correct guidance for your installation.

 

How are you going to maintain charging your leisure batteries ?

Do you have an outboard or inboard engine ? (make and model if outboard)

Are you planning on solar panels (if so what size) ?

 

 

If you buy a 12v fridge then you don't need an inverter.

Most 230v TVs these days actually have a 'brick' in their power line that reduces the supply to 12v, so a 12v supply is not a problem.

Phone, tablet, etc charging can be done via a 'cigarette' lighter socket and relevant USB chargers.

 

A fridge alone will use 30-50*Ah per day so you will need 1x 100Ah battery just to support the fridge, and will need to generate 40-60*Ah per day to replace that used

* = depending on make & model.

 

An Inverter uses power just to 'power itself' even when not powering any equipment, this can be anywhere between 0.5amps and 3 or 4 amps, so it is important to choose the 'right one'. Inverters are available in 'Pure Sine Wave' and 'Modified Sine Wave' most modern electrical/electronic equipment struggles with a MSW inverter.

Some equipment (mainly that with 'motors') draws considerably more than their 'rated' wattage so bear that in mind - eg, a fridge rated at (say) 75 watts may actually draw up towards 1000w on start up, buy your inverter with that in mind.

Basically buy a £100 inverter off ebay and (possibly) waste your money, or buy an £800 'marine' Quality brand and "get an inverter for life"

[leeco]

How much have you got to spend on a setup?

 

ive just installed a small setup with cheap inverter charger 300 watt of solar with MPPT charger 2 6v deep cycle batteries and all cost £950

[Detling]

1 hour ago, Alan de Enfield said:

Most 230v TVs these days actually have a 'brick' in their power line that reduces the supply to 12v, so a 12v supply is not a problem.

Phone, tablet, etc charging can be done via a 'cigarette' lighter socket and relevant USB chargers.

Used to be true, but most 240 volt TV's today ate 240 into the case those that do use a power brick are ususlly about 19 volts, but a laptop car charger will provide that.

[Chubb41]

Thanks the engine is a Volvo penter 2000  series and then Enfield 130 I’m thinking of  charging the battery from the alternator as the alternator seems to have another live feed from also so I can use want to charge alternator  and want to charge two  leisure batteries or maybe  switch to directly calling from the starter battery to the leisure batteries when the  battery to start the engine is full then from you leisure batteries to an inverter  ?  I will be living on the boat and it’ll be just a small fridge for milk etc  and sockets just to charge my phone and the TV that’s hope this helps

chris ps Thanks for all your advice

ps 12v over 240 ? 

Edited August 5, 2018 by Chubb41

[MtB]

Someone wrote a book about boat electrical systems and their design. You seem so 'at sea' over even the most basic of basics I suggest you buy it and read it before proceeding. Someone will be along shortly with the author and title.

 

Or read Tony Brooks' website tb-training.co.uk (IIRC the url)

[Tony Brooks]

9 hours ago, Chubb41 said:

Thanks the engine is a Volvo penter 2000  series and then Enfield 130 I’m thinking of  charging the battery from the alternator as the alternator seems to have another live feed from also so I can use want to charge alternator  and want to charge two  leisure batteries or maybe  switch to directly calling from the starter battery to the leisure batteries when the  battery to start the engine is full then from you leisure batteries to an inverter  ?  I will be living on the boat and it’ll be just a small fridge for milk etc  and sockets just to charge my phone and the TV that’s hope this helps

chris ps Thanks for all your advice

ps 12v over 240 ? 

An odd form of words in the middle of this lot that looks nonsense. The red part - I bet it does not have another output terminal.

 

Ideally you would wire the alternator output (B+) to the new domestic bank and the use a Voltage Sensitive Relay to connect the domestic battery positive to the engine battery positive. Both bank's negatives should be link by the same sized cable as the starter uses.

 

It will work if you just fit the VSR to link the engine battery to the domestic battery when the engine is charging and inking the battery negatives. However t will be subject to the potential for relay contact problems but hundreds of boats are wired like this.

 

When I see "fridge" and inverter I start to worry about undercharging the batteries and over discharging them so would advise an ammeter and voltmeter (digital) and learning how to interpret them to monitor your new batteries.

 

Yes te URL Mike gave is correct.