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Battery bank without grounding?


Tomek

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Hi. I want to build a strictly leisure battery bank with two 70Ah batteries and 2500watt inverter that will be used only for things like kettle, low power microwave, digital gadgets like phones and laptops, maybe cool box from time to time.

 

I do not want to connect my new leisure bank to the boat's engines and intend to charge it by petrol generator only.

 

I have an area near helm where I can place batteries and inverter - like a wooden box/cupboard. My question is... do I have to ground the batteries and the inverter?

 

Thanks, t.

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My battery bank and inverter are grounded/earthed. They are connected to the engine bed on two bolts that are about 70mm apart. That was the recommendation at the time when I wired my boat. My inverter also has a link between neutral and earth output connections. This is because the RCD device failed on its test without such a link.
I am curious as to why you don't want to take advantage of your boat engine's charging circuit though? Dead easy with a voltage controlled relay.

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13 minutes ago, Tomek said:

I do not want to connect my new leisure bank to the boat's engines and intend to charge it by petrol generator only.

Obviously you do not need to answer - but - If you would do so - Why would you want to do this, is just seems so strange and unconventional.

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I think your batteries are way too small for running the appliances you mention

 

With 2x 70Ah batteries you will have 70Ah usable (based on the 50% 'rule')

 

A 2kw Kettle will draw 200 amps (20 minutes will flatten the batteries)

A 750 watt microwave will draw 150 amps (30 minutes will flatten the batteries)

 

Both of which are (admittedly) normally only used for short periods.

 

A typical cool box will be drawing 4 or 5 amps continuously so after 24 hours it would actually have taken your batteries so low as to have actually damaged them.

(14 hours will flatten them)

 

Remember that whatever you take out has to be replaced.

Lets say you have a 20Ah battery charger - many people believe that this will charge your battery at 20 amps until it is 'full'. This is incorrect.

It would probably require 4-6 hours of running the generator and a battery charger to get the batteries charged to 95%, it will probably take another 3 or 4 hours to get it 'full'.

 

Add into the mix the dangers (and additional BSS requirements) of having petrol on board and the CO produced by the generator, it just doesn't seem to be an ideal system.

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16 minutes ago, Alan de Enfield said:

Obviously you do not need to answer - but - If you would do so - Why would you want to do this, is just seems so strange and unconventional.

Just so I dont kill myself... are you saying that if the bank is not connected to the boat's electrics grounding it isint necessary?

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7 minutes ago, Alan de Enfield said:

I think your batteries are way too small for running the appliances you mention

 

With 2x 70Ah batteries you will have 70Ah usable (based on the 50% 'rule')

 

A 2kw Kettle will draw 200 amps (20 minutes will flatten the batteries)

A 750 watt microwave will draw 150 amps (30 minutes will flatten the batteries)

 

Both of which are (admittedly) normally only used for short periods.

 

A typical cool box will be drawing 4 or 5 amps continuously so after 24 hours it would actually have taken your batteries so low as to have actually damaged them.

(14 hours will flatten them)

 

Remember that whatever you take out has to be replaced.

Lets say you have a 20Ah battery charger - many people believe that this will charge your battery at 20 amps until it is 'full'. This is incorrect.

It would probably require 4-6 hours of running the generator and a battery charger to get the batteries charged to 95%, it will probably take another 3 or 4 hours to get it 'full'.

 

Add into the mix the dangers (and additional BSS requirements) of having petrol on board and the CO produced by the generator, it just doesn't seem to be an ideal system.

As to the BSS, the generator would be fixed outside in the back of the boat like it's often done on narrowboats.

 

But you did open my eyes... I have a gas cooker. Do you think it would make more sense to boil water on bas rather than using a kettle? Microwave I have is low power 350watt only and I'll use it twice a week maybe for 2 minutes.

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9 minutes ago, Tomek said:

But you did open my eyes... I have a gas cooker. Do you think it would make more sense to boil water on bas rather than using a kettle?

Yes much more sense, even when on a shore power we still use a kettle on the gas. Same in the Caravan.

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6 minutes ago, Tomek said:

Just so I dont kill myself

230v AC is still 230v AC from an inverter and is still a 'killer' if mishandled.

 

You should be earthing the inverter.

Presumably you will be running the 230v output thru some form of fuse box, RCD etc ? and not just plugging the appliances straight into the inverter.

 

Re the Microwave - you don't 'get anything for nothing' you cannot cook something in a 350w microwave in the same time that you could in a 750 watt microwave.

It will take just over twice as long. So if it takes 10 minutes to 'cook the rice' (or whatever) in a 750w it will take you 25 minutes in a 350w microwave.

 

The wattage figures quoted for microwaves are the OUTPUT / COOKING power, NOT the input power - the input is usually about 2x the out put, so your 350w microwave will be drawing 70amps from the batteries vis the inverter.

 

If it is one of those 'camping / truckers' microwaves - forget it, look at the reviews - they are useless.

 

Do not use electricity for heating anything, unless plugged into a shoreline. Use the gas for cooking and for boiling the kettle.

 

Use batteries for when you NEED electricity, phone charges, laptop etc.

 

Assuming you have an engine with a 'normal' sized alternator (ie not an outboard engine) get your 'leisure batteries' plumbed into the system and let your engine charge them. It'll be cheaper than a generator and all the other 'stuff'.

 

You can get a 12v adapter to charge lap-tops  (mine is 12v to 19v) so you don't even need mains electricity.

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Just now, Tomek said:

 

 

As to the BSS, the generator would be fixed outside in the back of the boat like it's often done on narrowboats.

 

But you did open my eyes... I have a gas cooker. Do you think it would make more sense to boil water on bas rather than using a kettle? Microwave I have is low power 350watt only and I'll use it twice a week maybe for 2 minutes.

Yes, boil on the gas like most other experienced boaters do.

 

I bet that 350 watts is cooking power so the power drawn will be more like 700 watts so 70 amps from the batteries plus low power might mean its running for longer than a higher powered one.

 

This sounds like it might be an aft or centre cockpit GRP cruiser so with the cockpit up-stand you can't have the petrol generator in the cockpit or, indeed, anywhere withing the boat or you will breach the BSS UNLESS it's stored in a gas tight and properly vented "gas tank".

 

Unless the cool box uses a proper compressor then  I agree with Alan, not sensible to try to run it from batteries unless they are being charged.

 

Depends what you mean by "grounding". They are grounded to the metal parts of the boat so if a short circuit developed a fuse would blow or a breaker trip before the wiring and boat caught fire.

 

I note you have not told us what normally charges your batteries. If  its an engine alternator and you go cruising then the sensible thing to do is increase your domestic battery bank capacity (if you have a domestic bank) or use the new batteries to form one and feed all your domestic electrical loads from it (including the inverter) from it. Charge both the engine bank and domestic bank from the alternator by us using a split charge relay. However trying to get 140Ah of battery to supply 250 amps for the inverter at full output is far from practical, let alone recharging.

 

If you don't cruise then you need a mooring with a shore line so it all becomes academic.

 

If its charged form an outboard, especially an older one then I can see why you think you need a generator.

 

 

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4 minutes ago, Alan de Enfield said:

230v AC is still 230v AC from an inverter and is still a 'killer' if mishandled.

 

You should be earthing the inverter.

Presumably you will be running the 230v output thru some form of fuse box, RCD etc ? and not just plugging the appliances straight into the inverter.

 

Re the Microwave - you don't 'get anything for nothing' you cannot cook something in a 350w microwave in the same time that you could in a 750 watt microwave.

It will take just over twice as long. So if it takes 10 minutes to 'cook the rice' (or whatever) in a 750w it will take you 25 minutes in a 350w microwave.

 

The wattage figures quoted for microwaves are the OUTPUT / COOKING power, NOT the input power - the input is usually about 2x the out put, so your 350w microwave will be drawing 70amps from the batteries vis the inverter.

 

If it is one of those 'camping / truckers' microwaves - forget it, look at the reviews - they are useless.

 

Do not use electricity for heating anything, unless plugged into a shoreline. Use the gas for cooking and for boiling the kettle.

 

Use batteries for when you NEED electricity, phone charges, laptop etc.

 

Assuming you have an engine with a 'normal' sized alternator (ie not an outboard engine) get your 'leisure batteries' plumbed into the system and let your engine charge them. It'll be cheaper than a generator and all the other 'stuff'.

 

You can get a 12v adapter to charge lap-tops  (mine is 12v to 19v) so you don't even need mains electricity.

Agree with everything but one last thing I have become aware of: It is getting harder to find a lap top that will run off those excellent 12-19 converters. I really struggled and now have a Dell and an HP laptop that have a silly 3 wire system on the DC side, and can only use official power supplies. I bought a cheapo inverter (Ring) that charges my laptops and cameras nicley. Not very efficient I know, but any port.... 

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28 minutes ago, Tony Brooks said:

Yes, boil on the gas like most other experienced boaters do.

 

I bet that 350 watts is cooking power so the power drawn will be more like 700 watts so 70 amps from the batteries plus low power might mean its running for longer than a higher powered one.

 

This sounds like it might be an aft or centre cockpit GRP cruiser so with the cockpit up-stand you can't have the petrol generator in the cockpit or, indeed, anywhere withing the boat or you will breach the BSS UNLESS it's stored in a gas tight and properly vented "gas tank".

 

Unless the cool box uses a proper compressor then  I agree with Alan, not sensible to try to run it from batteries unless they are being charged.

 

Depends what you mean by "grounding". They are grounded to the metal parts of the boat so if a short circuit developed a fuse would blow or a breaker trip before the wiring and boat caught fire.

 

I note you have not told us what normally charges your batteries. If  its an engine alternator and you go cruising then the sensible thing to do is increase your domestic battery bank capacity (if you have a domestic bank) or use the new batteries to form one and feed all your domestic electrical loads from it (including the inverter) from it. Charge both the engine bank and domestic bank from the alternator by us using a split charge relay. However trying to get 140Ah of battery to supply 250 amps for the inverter at full output is far from practical, let alone recharging.

 

If you don't cruise then you need a mooring with a shore line so it all becomes academic.

 

If its charged form an outboard, especially an older one then I can see why you think you need a generator.

 

 

As to the heating... I have a Mikuni diesel heater. Would you know if it uses battery power too?

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30 minutes ago, Tony Brooks said:

Yes, boil on the gas like most other experienced boaters do.

 

I bet that 350 watts is cooking power so the power drawn will be more like 700 watts so 70 amps from the batteries plus low power might mean its running for longer than a higher powered one.

 

This sounds like it might be an aft or centre cockpit GRP cruiser so with the cockpit up-stand you can't have the petrol generator in the cockpit or, indeed, anywhere withing the boat or you will breach the BSS UNLESS it's stored in a gas tight and properly vented "gas tank".

 

Unless the cool box uses a proper compressor then  I agree with Alan, not sensible to try to run it from batteries unless they are being charged.

 

Depends what you mean by "grounding". They are grounded to the metal parts of the boat so if a short circuit developed a fuse would blow or a breaker trip before the wiring and boat caught fire.

 

I note you have not told us what normally charges your batteries. If  its an engine alternator and you go cruising then the sensible thing to do is increase your domestic battery bank capacity (if you have a domestic bank) or use the new batteries to form one and feed all your domestic electrical loads from it (including the inverter) from it. Charge both the engine bank and domestic bank from the alternator by us using a split charge relay. However trying to get 140Ah of battery to supply 250 amps for the inverter at full output is far from practical, let alone recharging.

 

If you don't cruise then you need a mooring with a shore line so it all becomes academic.

 

If its charged form an outboard, especially an older one then I can see why you think you need a generator.

 

 

I will boil and cook on gas only then :)

 

You were almost right! I have a centre cockpit steel cruiser.

 

As to the batteries, I have four batteries and two engines. Three batteries with two battery switches are on side of left engine and one battery on side of right engine with near master switch. I dont know know which ones are leisure but I will look into it. I don't even know the capacity ?

 

I have a mooring but not residential and want to try and cruise continuously over the winter on river Cam and Great Ouse which is a real challenge as all the moorings are 48h.

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On our butty we had a 12 volt system for lights and pumps and a 24 volt for the inverter. 

In those days the inverter was the size of a small fridge and was a useful source of heat as it powered its way up to 500 watts.

 

anybody under the age of 60 can turn off now.

this was to run the trusty hifi.

 

Bd1a turntable 

mission acoustic 720 ( still got them)

rogers  ravensbrook amp

sony tuner

jvc cassette deck

the speaker wires were thicker than most peops fridge wires.

 

the only problem was mains hum but hey it had 30watts rms just wind it up theres no one else on the cut.

 

was it earthed. No. Was the hull earthed. No.

was there a fuse box no

was there a certificate of normality

no

we survived.

 

 

 

  

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51 minutes ago, Tomek said:

As to the heating... I have a Mikuni diesel heater. Would you know if it uses battery power too?

You bet it does.  About 20A during start up and 5A (IIRC) when its running.

 

8 minutes ago, Alan de Enfield said:

Yes - it must use electricity from the battery(s) to get the spark to ignite the diesel.

To be pedantic, it uses a glow plug, not a spark as it starts up and then a fan and a pump continuously.

 

 

N

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2 hours ago, Tomek said:

As to the BSS, the generator would be fixed outside in the back of the boat like it's often done on narrowboats.

 

 

This is coming up time and time again. You may have seen petrol generators on the back of narrowboats but it won't pass the BSS.

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11 hours ago, Tomek said:

As to the heating... I have a Mikuni diesel heater. Would you know if it uses battery power too?

Yes - all the time it is running. I very much doubt your battery bank is anywhere near large enough to support that inverter and any form of Mikuni type heater -= air or water.

10 hours ago, Tomek said:

I will boil and cook on gas only then :)

 

You were almost right! I have a centre cockpit steel cruiser.

 

As to the batteries, I have four batteries and two engines. Three batteries with two battery switches are on side of left engine and one battery on side of right engine with near master switch. I dont know know which ones are leisure but I will look into it. I don't even know the capacity ?

 

I have a mooring but not residential and want to try and cruise continuously over the winter on river Cam and Great Ouse which is a real challenge as all the moorings are 48h.

Yes - and you will face flood conditions with very high water levels, high flows and likely great logs sweeping down stream and hitting your boat. Very bad idea. I suspect that often the moorings will be under water for days or maybe weeks at a time. I do not know those rivrs but do know the Thames that is by & large very well controlled.

 

If its a steel boat the it is vital that the 12V batteries are connected to the hull at a single point because the dangers of a cable shorting to the metal hull are much greater than with a GRP boat.

 

Before you go spending any money you need to understand the electrical and charging system you have. I suspect but do not know the three batteries are domestic ones and the single is the start battery. How the charge splitting is accomplished  is anyone guess, especially as you presumably have an alternator on both engines. The battery switches may be simply on-off isolator switches or   they could be bat1, bat2, both, off switches that can be wired in a number of ways but most probably to switch charge or to switch battery banks. a photo would help identify the switches.

 

What is becoming clearer to me is that you seem to have little idea about the problems of storing the electricity you will use and far more importantly how you will get everything you take out of the batteries back in within a reasonable time. I am sure you would do better by adding additional batteries to your existing battery bank and ensuring they are charged in the best way possible form the engines that going down the separate generator route although a separate generator is a very nice addition. However any 12V output on a 230V AC generator is NOT suitable for long term battery charging. You need to add a 230VAC charger for that.

 

Despite what some on here say boats are no floating cottages connected to the mains services and should not be considered as such. Electricity use needs to be very considered and battery charging very diligent.  My advice is forget the inverter and you can get car adaptors to charge pones and run laptops etc. I would also advise that you get some form of battery monitoring equipment and some knowledge so you do not destroy your batteries in days or a few weeks. Be aware that any monitor that shows amps, volts, amp hours in & out plus any percentage of charge left or time left is likely to encourage you to destroy your batteries unless you totally understand its demands, setting & shortcomings.

 

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12 hours ago, blackrose said:

 

This is coming up time and time again. You may have seen petrol generators on the back of narrowboats but it won't pass the BSS.

I agree.

 

It is essential to avoid exhaust gas from a petrol boat entering the boat interior. I do ocassionally use a petrol generator but only if the generator off the boat and well clear of any risk of fumes entering my boat or others.

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1 hour ago, MartynG said:

I agree.

 

It is essential to avoid exhaust gas from a petrol boat entering the boat interior. I do ocassionally use a petrol generator but only if the generator off the boat and well clear of any risk of fumes entering my boat or others.

I would be far more concerned about fumes from the petrol because once they reach a certain concentration the slightest spark and you get a very large bang. Of course exhaust fumes are also dangerous but a little more slow acting than petrol fumes. Agree only use off the boat for both reasons, including refuelling on the bank.

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3 hours ago, roland elsdon said:

Lovely things. Did you buy a kit. 

Nope. I accumulated all sorts over the years. I regularly use a Quad 33 & 303 through a pair of Proac Tablettes but I have other kit that gets used at different times. 

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3 hours ago, Tony Brooks said:

I would be far more concerned about fumes from the petrol because once they reach a certain concentration the slightest spark and you get a very large bang. Of course exhaust fumes are also dangerous but a little more slow acting than petrol fumes. Agree only use off the boat for both reasons, including refuelling on the bank.

There should be no significant petrol fumes if the generator if functioning correctly  . But agree refuelling must be ashore.

Concern about exhaust fumes from petrol engines ,in boats, is well founded. There have been deaths from carbon monoxide poisoning as you surely know. 

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41 minutes ago, MartynG said:

There should be no significant petrol fumes if the generator if functioning correctly  . But agree refuelling must be ashore.

Concern about exhaust fumes from petrol engines ,in boats, is well founded. There have been deaths from carbon monoxide poisoning as you surely know. 

Of course I know but I think you overstate the dangers. Its a bit like saying people get killed crossing the road so never cross the road. I have often run my generator while doing small jobs on the cruiser stern and also in the well deck but for that I make sure the cover is rolled right up. In both cases the exhaust is pointed away from the cabin entrance.  Diesels make CO as well, just not so much of it, especially our old low pressure mechanically injected versions. 

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