Posted: Sun Apr 19, 2020 10:16pm

Hi,I'm new to the forum so not sure if this has been asked recently.im having a widebeam built at min and would like to have a 48v 10kwh battery bank and was wondering if going all 230v on the boat would A .. be safe if done correctly. B... Has anybody already done this that could advise. The fridge is 230v and so an inverter will be on all the time.

Posted: Sun Apr 19, 2020 11:29pm

Sorry forgot to add. Battery's are lithium and will have 3kw solar array.

Posted: Mon Apr 20, 2020 9:28am

As batteries provide DC current and 230V is AC you will need an inverter to convert one to the other. When you say all 230V what do you mean? If this is to be a diesel engined boat then you won't find a 230V AC starter motor very readily if at all although you could swap the alternator for a Travelpower that gives a 230V output. You can't charge batteries from 230V AC without a battery charger although with h that may be the easiest way to get a sufficiently close control of the charging. Then there is the availability and easy sourcing of things like 230V water pumps and shower pumps. If you mean running all the other domestic equipment on 230V then as long as the system is correctly installed and maintained with all the necessary safety devices then there is no reason not to do so. I would suggest that most new boats have ample 230V AC power sockets and many run 230V fridges, TVs etc. If it is a diesel engined boat then the complications will be with starting and providing 12V/24V DC for the warning lamps and instruments. If you intend to use a lead acid battery in parallel with the lithiums to act as an alternator load when the lithium charging is turned off and engine start battery the trying for a fully 230V AC boat complicates things. I am also far from clear why you are wanting a 48V battery bank. It sounds as if you might be going for electric propulsion in some way and if so that further complicates things if a diesel engine is also installed. You talk about a 10kWh battery bank. That is equivalent to a 200Ah bank @ 48 volts, 400 @ 24Volts and 800 @ 12 volts. As you can use most of that capacity with lithiums exactly how do you intend to recharge the batteries between (say) October and May? However much solar you install I doubt that will do it. You are unlikely to get more than about half the solar panel's rated output in the UK at midday in high summer so even accepting the lithiums will accept virtually all the current you can throw at them it seem that depending upon your electrical use you might have a shortfall in charging during the summer and will have one during the winter. My advice is to discuss all this with your boat builder and get insurance backed guarantees that whatever system they install it will fully provide for your electrical needs over the full year.

Posted: Mon Apr 20, 2020 3:38pm

Hi, thank you for replying. I will be using an inverter at 48v and I'm having a 48v alternator fitted to charge battery's when not enough sun. From the sounds of it there is no real problem going all 230/240v. I understand using an inverter will create some losses but with efficient equipment I can't see me using more power than at 12/24v.

Posted: Mon Apr 20, 2020 4:04pm

Hi Tony, just to explain a little better. I'm having a widebeam sailaway built and will fit out myself. With help from a very good electrician. I am wanting to go completely 230v. This is why I've chosen 48v and I was also looking to maybe add an electric drive to prop in future. I want to go 230v mainly because I can get things easily and cheaper. With regards to the solar panels I could go 4kw to help with charging but will have a 48v 100ah alternator on engine to charge batteries. I didn't think about warning lights and control panels being 12/24v so I may well get a 12/24v lithium for this purpose.

Posted: Mon Apr 20, 2020 4:34pm

Some comments. Make sure your good electrician fully understands the regulations re mains wiring on BOATS plus the 12/24/48 volt DC stuff. So you are having a special engine build installed? That is nearly a 5Kw alternator (assuming you mean 100 amps, alternators are not rated in Ah). 4.8kW = 6.5 HP through the belt - some belt! And its even more than that when the inefficiency is taken into account. You may find with lithiums the engine will not rev up. I very much doubt you will have a 48V 100Amp alternator. Have you costed the mains versions of the domestic water pump, shower pump and navigation lights? I doubt they will be any cheaper than the 12/24 volt equivalent. The starter will probably be 12 or 24 volt and they need lots of amps. I know lithiums charge quickly but you may have to reduce the charge to prevent the alternator overheating and that will increase the charge time. Have you done a power audit and charging calculations yet to see how large your battery bank will have to be and how or how long you will need to recharge it? Sorry but at present this has all the hallmarks of a very early stage project that may need a very heavy dose of realism if it is to become an actual workable boat. Anyway as long as its properly installed by a proper marine electrician who understands all the regs going fully 230V AC will be safe.

Posted: Mon Apr 20, 2020 5:10pm

Hi Tony, the electrician has done several off-grid installs and has some experience of boat electrics. He's a friend who will research everything required to install correctly and safely. The alternator is as you say 100amps not ah. Apologies. I've spoken with the engine builder who has used this unit before and has the correct pulley system for it. Your correct that it will be 4.8kw. I'm no expert in this field so have to take the advice given by the engine builder. With regards to the pumps I agree this will not save me money. It's more the fridge, TV, washing machine and things that will be a lot cheaper and with lighting I'll have much more choice as to fittings. Although I am considering running the lights at 48v. As for this being a project.. your correct again 🙂. I understand this is going to be more difficult than maybe I realise but I'm hoping by doing enough research and getting very helpful advise from people that know. (Thank you Tony). That I'll be able to do this.

Posted: Mon Apr 20, 2020 7:05pm

Please ensure that he does not use flat twin & earth as he would/could on a land based off grid installation. It must be multi-strand flexible cable. Often a suitably sized "arctic" grade cable is used. As this is a new boat and if there is the slightest chance you may need to sell it within 5 years at present it must comply with all the ISO standards referred to in the Recreational Craft Directive. Come January 1st 2021 this may change but I would not bank on it. You will be responsible for completing the paperwork demanded by the RCD.

Posted: Mon Apr 20, 2020 7:28pm

Hi Tony, will be using arctic blue. I don't plan on selling as will be living aboard. Thank you for advice about rcd. I'll comply with what ever is needed.