Electric system | Narrowboat Blogs | Narrowboat Forum

Avatar

Please consider registering
guest

sp_LogInOut Log In sp_Registration Register sp_MemberList Members

Register | Lost password?
Advanced Search

— Forum Scope —




— Match —





— Forum Options —





Minimum search word length is 3 characters – maximum search word length is 84 characters

sp_Feed Topic RSS sp_TopicIcon
Electric system
Friday,28 November, 2014
4:58 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

12 volt or 24 volt ?

Would there be some hidden pitfalls in using a 24 volt system?
I would like the opinions of the experienced boaters on this. 

M

Friday,28 November, 2014
7:53 pm
Avatar
Member
Members
Forum Posts: 59
Member Since:
Sunday,3 November, 2013
sp_UserOfflineSmall Offline

24 volt enjoys a lower current draw (amps =watts/volts), so hence you get longer battery life because of a lower amp draw:

100w/12v = 8.3 amps

100w/24v = 4.16 amps

The lower amp draw also means that thinner (and hence cheaper) cable can be used

However, 24volt stuff tends to be a lot more expensive to buy than 12 volt, as the market is very exclusive

 

Si

Saturday,29 November, 2014
12:06 am
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

The longer battery life is a red herring but you will benefit from lower voltage drop on long cable runs to devices, given same gauge cable.

Although 12 volts is the industry standard, 24 volts is used on most trucks so there are many devices that work on such. Budget though to have a 12 volt system as well.

Finally the higher voltage makes for more efficient engine driven alternator(s} to charge your batteries.

Regards – Richard –
Ecky Thump

Saturday,29 November, 2014
12:56 am
Avatar
Member
Members
Forum Posts: 183
Member Since:
Monday,21 May, 2012
sp_UserOfflineSmall Offline

The thing here is safety in numbers. The vast majority of canal boats are 12v.

Power losses are better at 24V and 48V (think national grid at 400KV, there is a reason for that) but there are few devices that will matter on this. Bow thrusters and solar panels spring to mind as having long cable runs.

But on a dark and cold winters eve when you need something fixing ‘now’ … 12v will be easier and cheaper (cheaper being a relative term on boats).

If you contemplate a hybrid 12v / 24v system, you have added another layer of complexity to your life :)

We’ve been stranded a couple of times with no power (on hire and then our share boat) and it’s not funny. You really want to make sure that you have the simplest of setups so someone (maybe you) has a good chance of fixing it when needed. Probably by torch light !!

PB

Monday,1 December, 2014
5:55 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

Thank you all for the input !

Cable size was one argument – I could put the heavy battery bank in the forehold to balance the boat.
Added plus – it’s cooler in there (battery life).
The inverter/charger would also go in there, so the high-load cables will be very short.
This would also save separate batteries for the bow thruster (if fitted), only the diesel generator will have it’s own starter battery.
(the steam plant doesn’t need a battery for starting – only some matches and paper/wood)

The last evenings I have compared availability and prices, very rough guide only, but it shows a picture.

– inverter/charger 4.5 kW
24 volt model is marginally smaller and lighter than 12 volt (not by a decicive margin)
24 volt model is at least 15 % less cost!! (checked on the Victron page and current price list)

– pumps (circulating and fresh water)
same size, same price

– alternators
same size, nearly same price

– cables, switches, fuses
would be the same or marginally smaller/cheaper

– bow thruster
available in both voltages

– freezers
some models available in both voltages (Engel for example, high price in all versions)

– refrigerators
same size, same price
(but the use of 240 volt models has been propagated here with good arguments, I will really have to check this)

– washer/dryer/cooking/microwave
not applicable as I want to use 240 volt models

btw there are a lot of 12/24 volt microwaves for truck use.

Where there might be problems
– cooling fans
– TV/monitors

DC/DC-converters 24/12 volt are not too expensive, this could be used to power a low-load 12 volt rail for unexpected cases.

 

So I would see no (big) problem in using a 24 volt system.
The critical pumps for the steam plant and the water system will be duplicated, this is good marine usage.
I know that everything can fail (and will at some time), that is why you carry spares.
The parts which you have as spare on board will probably never fail. Wink
One last argument: traction cells are rather heavy, in going to 24 volt there will still be reasonable capacity
at a weight which can be handled without special equipment in an emergency.

Richards comment “The longer battery life is a red herring” I don’t understand completely,
for 12 volt I will need 2 6V-traction cells, for 24 volt I will need 4 cells – so the stored energy (Whrs) should be double.

M

 

ps: the math required for this post was 12+12 – if that isn’t an indication! Laugh

Monday,1 December, 2014
9:10 pm
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Sorry there was a misunderstanding. Obviously if you are comparing 12 & 24 volt battery sets with the same amp hour capacity, the latter will double the energy available as you have double the number of 12 or 6 volt batteries.

It was a suggestion that somehow a 24 volt system drew less energy from a battery that I was commenting on.

Out of interest will you be using DC output alternator(s) driven from your steam plant and if so your thoughts on compensating for the volt drop on the charge cable run from back to front of boat (there are ways). Also how do you plan to use the Victrons charger – will it be only used on shore power or will you have onboard AC generation other than Victrons inverter of course? 

Regards – Richard –
Ecky Thump

Tuesday,2 December, 2014
4:57 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

I made a preliminary sketch of the electric system:

http://fs1.directupload.net/images/user/141202/lo7wmzxd.jpgImage Enlarger

 

“… compensating for the volt drop on the charge cable run from back to front of boat (there are ways)”

Of course I would be very interested in your assistance.

M

Tuesday,2 December, 2014
5:25 pm
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Thanks for schematic, which always explains things better than words. Can I assume the shore power 10 amp feed to Victron is down to the isolation transformer limitations? If so you would need a current limiting breaker after the IT (but before the generator feed) since most shore power hookups offer 16 amp connections.

Regarding volt drop on the 9 metre charge cable run (x 2 to allow for return). You would need to use substantial cable cross-section. Off the top of my head around 50mm2 with fuses both ends. In any case volt drop could be compensated by remote sensing alternators or more likely external digital alternator regulators as sold by Sterling and Adverc. Having said that the simplest although not neccessarily cheapest solution would be a single Sterling alternator to battery charger sized to take the combined max output of both alternators which would be paralelled to this device. Whatever you choose the sensing wire would run directly to the battery bank, such that the device compensates for volt drop by running the alternator(s) at a higher voltage. Volt drop on this particular cable wouldn’t be an issue since its high impedance sensing.

Regards – Richard –
Ecky Thump

Tuesday,2 December, 2014
5:54 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

The current limiting will be done by the inverter/charger, if there is higher demand the diesel generator will get a start signal
as long as it is not locked out manually. If I use the smaller version of the IT a current limiting breaker would be reasonable.

For a voltage drop of max. 0.5 volts at 80 amperes I have arrived at 100 mm², that is a lot but could be done with two cables each way.

Questions:
– could the 24 volt cables be run along the bilge?
  (high voltage cables will be run just below the gunwhale in a cable duct)
– would the DC-system be grounded?
  In any case I will use both + and – cables, so no current is transferred throug the hull.
– could traction cells be wired in parallel to increase capacity with using smaller cells?
  (I found different opinions on this)

Thank you for the info on the external digital alternator regulators.

M

Tuesday,2 December, 2014
8:58 pm
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Montgomery said
The current limiting will be done by the inverter/charger, if there is higher demand the diesel generator will get a start signal
as long as it is not locked out manually. If I use the smaller version of the IT a current limiting breaker would be reasonable.

For a voltage drop of max. 0.5 volts at 80 amperes I have arrived at 100 mm², that is a lot but could be done with two cables each way.

Questions:
– could the 24 volt cables be run along the bilge?
  (high voltage cables will be run just below the gunwhale in a cable duct)
– would the DC-system be grounded?
  In any case I will use both + and – cables, so no current is transferred throug the hull.
– could traction cells be wired in parallel to increase capacity with using smaller cells?
  (I found different opinions on this)

Thank you for the info on the external digital alternator regulators.

M

My thoughts were that AC passing through the Victron Combi to distribution could well exceed the IT’s current limitation. Yes you can tweak the Victron to limit but then you may find its inverter kicking in to supplement the AC current draw. Fitting a 10 amp MCB on the IT’s output (assuming that’s its current rating) solves the issue in one go without worrying if you have programmed the Victron correctly or even that its performing current limiting as intended.

Regarding charge cable dimensions, as an example I use 35mm2 over a longer run and at 12 volts! This is only to charge a pair of batteries for BT though (12 volt 220aH) with max 90 amp alternator. I know that over a 100 amps has been drawn down this cable due to short term back feed from service bank before the splitters inhibit cut in, as the fuse blew (its now fused at 200 amps). I have a monitor dedicated to this battery bank and have absolutely no charge issues, indeed the instant the bowthruster is used I hear the engine note change as alternator replaces the power drawn from batteries.

Trying to achieve such a minimal volt drop with such massive cables IMO seems like serious overkill, especially as it can be compensated for as in previous post. 

There are many reasons to have the battery negative connected to hull, but none of them deflect from the need for a cable return to battery negative for each device. It used to be thought that this may cause electrolytic corrosion but it has been proven that as long as its the negative thats grounded there will be no loss of hull metal. Whilst under normal conditions no current should flow through the single strap from battery negative to boat hull, it provides a clear path under fault conditions for fuses and breakers to operate by turning a tenuous situation into a known one.

The cables on my boat run under the gunnels down both sides of the boat enclosed neatly in rectangular section trunking and totally out of view whilst being easily accesible. Using 2.5mm2 three core double insulated arctic cable for distribution will allow AC and DC to run alongside each other. Running cables in the bilge offers more chances of chaffing and poor accessibility.

Finally with regard to batteries a single lead/acid cell is nominally 2 volts at whatever amp hour (Ah) capacity. Stringing them in series increases voltage with Ah of bank remaining the same as a single one. Putting this string in parallel with other similar ones leaves voltage the same but increases Ah capacity of bank. It therefore doesn’t matter how you cable them together to achieve your goal as long as its done in a balanced manner. This topic may help when linking 12 volt batteries – I would treat each depicted 12 volt battery as a pair in series for 24 volts.

Regards – Richard –
Ecky Thump

Wednesday,3 December, 2014
6:32 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

Thank you very much,
this is a really informative website, it will be reading stuff for the next two months.
The diagrams for battery connections and the calculations show how easily one could be completely wrong – a real eye opener!

As it looks now, the forehold has changed from fuel storage to electricity storage. Laugh
That’s important to me, as I want to use only a wee bit of ballast (should be possible with a 15 mm base plate).
So the balancing of all the heavy parts along the available space is a real challenge.
An added bonus is the easy accessibility for the rather heavy cells,
also they are out of harms way if one of them should decide to misbehave
(I would not like to have a runaway battery near the bedroom…. ).

Also the forehold will be one of the coolest areas of the boat, this will have a direct influence on battery life.
With the cost of a large battery bank some effort in this direction should be reasonable.

I would also like to hear your opinion on Trojan batteries?

M

Wednesday,3 December, 2014
11:07 pm
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Had a set of Trojans once. Not the popular true deep cycle 6 volt T105 golf cart ones, but 12 volt open lead acid although they were also supposed to be deep cycle. From the outset I was not impressed by the fact they drew current whilst on float, and they only lasted a little over three years. This in contrast to the cheap so called leisure batteries which generally being of lead calcium plate construction have a very well defined current draw cut off when fully charged. My current 550 Ah bank draws less than an amp whilst on float. This increases my confidence as I know a) when they are fully charged and b) am unlikely to suffer any gassing issues, electrolyte depletion, overheating, fumes etc. 

Having said all that the T105’s seem popular and the price premium is not as great as it was if you shop around. My current thinking is that I will stick with the sealed lead calcium leisure ones when the present ones need replacing. The are showing no great signs of capacity loss after 2.5 years, and I charge them at up to 14.8 volts (14.4v recommended), but they are never kept at this voltage being left on float at 13.5 volts when fully charged. A similar set lasted five years despite being abused during Atlantic crossing. I expect to pay aroud £70 each for 12 volt 110 Ah ones.

Regards – Richard –
Ecky Thump

Thursday,4 December, 2014
10:23 am
Avatar
Where the mood takes me, from the south coast to the canals of England/Wales
Member
Members
Forum Posts: 462
Member Since:
Wednesday,5 December, 2012
sp_UserOfflineSmall Offline

There have been several changes in recent years to the BSS on electrical things. I think you will find there is a requirement for a negative return from each device back to the battery. The use of the hull as a return is not liked.

 

http://www.boatsafetyscheme.or….._final.pdf

 

BSS 3.3.3 applies to electric cables both DC & AC run in the bilges

 

BSS 3.9 Alternating current systems – multiple power sources and consumer units

Thursday,4 December, 2014
4:46 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

Hallo,

no worry,
there will always be two cables (+ and -) in each DC circuit, using the hull as return was never planned.
I just want to earth the negative battery connection on one point to avoid unclear situations and spurious voltages arond the boat.
This earth connection will be the central earth also for the 240 volt rail (required for safety reasons).
For all 240 volt circuits there will be RCD/RCBO protection – I have this in my workshop, has saved many  a nasty situation.Laugh

According to BSS 3.3 a seamless cable in the bilge (in a solid cable tray) will be no problem.

BSS 3.9.1
“Applicability – the requirement for one power source to be connected does not apply to synchronised multiple power sources.”

A Victron Quattro is designed exactly for this situation:
– shore connection and
– generator with automatic cut in at higher demand

In my sketch you can see the changeover switch in the shore connection, so only one socket can be live at a time.
What’s missing in this drawing is the middle position – both sockets disconnected.
The cables will have to be protected by a RCD at each end, especially the aft connection is quite long.

M

Friday,5 December, 2014
12:23 am
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Its a matter of personal choice I know but would be interested in your reasoning for two shore power inputs given its extra complexity. If its just to allow shore power hookups from either end of your relatively short boat and be able to use a shorter shore power lead, why not have a longer one – chances are you will need the extra length at some point anyway.

Regarding RCD’s – they only protect downsteam and duplicating them again increases complexity with little or no safety gain. The shore power pedestal socket will have its own RCD protection so that takes you to the IT’s input. An RCBO (combined RCD and overload breaker) on its output would achieve the overload protection I alluded to earlier. Finally an RCD on the Victron output (pass through or inverter) would satisfy the BSS requirements.

Regarding the Victron – I know it can supplement limited incoming AC with a syncronised output from its own inverter, but I wasn’t aware it can achieve that with an AC supply from external generator. How is the generator syncronised to grid power? as it would need a very sophisticated genny to accept external sync.

Finally – sorry to go on ;) – beware of having fully automated generator start-up systems. Nice to have the bells and whistles to achieve this, but you may not be best thought of if it decides to fire up the genny in the middle of the night, not to mention your own lack of sleep. Certainly not a good thing if boat unattended – too much potential for something to go wrong without intervention.

Regards – Richard –
Ecky Thump

Friday,5 December, 2014
4:52 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

Hallo Richard,
regarding shore power input and lead you are right, I will have to think about it.
Front or back or never mind?

Victron (from the description on the webpage):
“Two AC inputs with integrated transfer switch
The Quattro can be connected to two independent AC sources, for example shore-side power and a generator,
or two generators. The Quattro will automatically connect to the active source.”
 
I will have to study the manual again, it’s not quite clear if the generator has to be already running or not,
anyway it is not a synchronisation but a switch over (either shore or generator). 
On one side I believe in sensible automation, on the other side I would always fit a selector manual-automatic
if possible or simple a shut off switch (to prevent starting) so I would not get beaten by my neighbours on a mooring. Laugh
M
Friday,5 December, 2014
5:36 pm
Avatar
Where the mood takes me, from the south coast to the canals of England/Wales
Member
Members
Forum Posts: 462
Member Since:
Wednesday,5 December, 2012
sp_UserOfflineSmall Offline

Montgomery said
Hallo Richard,
regarding shore power input and lead you are right, I will have to think about it.
Front or back or never mind?

Victron (from the description on the webpage):
“Two AC inputs with integrated transfer switch
The Quattro can be connected to two independent AC sources, for example shore-side power and a generator,
or two generators. The Quattro will automatically connect to the active source.”
 
I will have to study the manual again, it’s not quite clear if the generator has to be already running or not,
anyway it is not a synchronisation but a switch over (either shore or generator). 
On one side I believe in sensible automation, on the other side I would always fit a selector manual-automatic
if possible or simple a shut off switch (to prevent starting) so I would not get beaten by my neighbours on a mooring. Laugh
M

It is a long time since I have played with the likes of the Quattro, but I do not think the Quattro is capable of synchronising to two independent AC sources. I think that is why BSS are not happy with more than one AC source being able to feed a boat’s systems at any one time. Probably don’t have to explain to either of you what happens when two out of sync AC high voltage feeds meet. 

I think you will find BSS will need convincing that at no time can two AC sources feed the Quattro. That is unless you can find a generator that will sync itself to the shoreline.

GM

Friday,5 December, 2014
6:41 pm
Avatar
Member
Members
Forum Posts: 42
Member Since:
Monday,6 October, 2014
sp_UserOfflineSmall Offline

From the manual:
“Two AC inputs; integrated switch-over system between shore voltage and generating set
The Quattro features two AC inputs (AC-in-1 and AC-in-2) for connecting two independent voltage sources.
For example, two generator sets, or a mains supply and a generator set.
The Quattro automatically selects the input where voltage is present.

If voltage is present on both inputs, the Quattro selects the AC-in-1 input, to which normally the generating set is connected.

(underlining done by me)

So the switch over is done automatically, but the start (or stop) of the generator has to be done manually.
If the generator is switched off mains takes over.
According to this description it is not possible to draw power from both simultaneously.

M

Saturday,6 December, 2014
10:25 am
Avatar
Aldermaston
Member
Members
Forum Posts: 292
Member Since:
Thursday,12 January, 2012
sp_UserOfflineSmall Offline

Montgomery said
Hallo Richard,
regarding shore power input and lead you are right, I will have to think about it.
Front or back or never mind?

Victron (from the description on the webpage):
“Two AC inputs with integrated transfer switch
The Quattro can be connected to two independent AC sources, for example shore-side power and a generator,
or two generators. The Quattro will automatically connect to the active source.”
 
I will have to study the manual again, it’s not quite clear if the generator has to be already running or not,
anyway it is not a synchronisation but a switch over (either shore or generator). 
On one side I believe in sensible automation, on the other side I would always fit a selector manual-automatic
if possible or simple a shut off switch (to prevent starting) so I would not get beaten by my neighbours on a mooring. Laugh
M

Hi Montgomery, yes I thought that was the case with the Victron’s input although your post suggested the generator cut in at higher loads. I think what actually happens is that shore power is given priority, but if it fails and generator output is sensed by the Victron it will automatically switch over. Either that or it can trigger an auto start up.

Regards – Richard –
Ecky Thump

Monday,8 December, 2014
5:15 pm
Avatar
Member
Members
Forum Posts: 3
Member Since:
Monday,11 February, 2013
sp_UserOfflineSmall Offline

Bloomin’ ‘eck!

saw the electrical system thread, and thought that’s exactly where I need to be to get my questions answered – until I started reading it !!

Didn’t understand half of what was said, and I pride myself on being a reasonably intelligent bloke, so at the risk of sounding exactly the opposite I’ll ask my question(s) – next year me and “she who’s really in charge” are having a widebeam built, on which we intend to live permanently, and initially at least, continuously cruise. 

We’ve pretty much got everything sorted out, layout; heating; cooking etc. but my main concern is having enough electricity to survive “off grid.” The boat will have an integral generator included (but I’d rather save that for emergencies), and we intend to have 4-6 100w solar panels installed. Since there will be times when we are not underway, and therefore not charging the batteries, we are looking to fit out the boat with the most energy efficient system and appliances. I have been told that the best option is to have both 240v sockets and 12/24v sockets. I’m looking to run a fridge, freezer, laptop and possibly TV on 12/24v with the larger appliances (washer/dryer, microwave etc.) on 240v. Which is best 12 or 24v and is it worth the effort and expense? ANY advice (please keep it as simple as possible so’s not to fry my brainConfused) that anyone can offer would be most appreciated.

Martin

Forum Timezone: Europe/London

Most Users Ever Online: 298

Currently Online:
5 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

pearley: 968

Alan: 637

GM: 462

deckhand: 296

richardhula: 292

Paul B: 183

Johny London: 142

martincowin: 120

MikeEaves: 116

Our Nige: 110

Member Stats:

Guest Posters: 69

Members: 15090

Moderators: 0

Admins: 1

Forum Stats:

Groups: 1

Forums: 10

Topics: 1458

Posts: 9024

Administrators: Paul Smith: 1797

Direct Your Visitors to a Clear Action at the Bottom of the Page