electrics Electrics - Inverter vs Transformers

[rusty69]

5 hours ago, Tony Brooks said:

You will get the rated output for a comparatively short time, probably less than an hour) while the batteries demand more electricity than the alternator/charger can supply but very soon that alters.

Sir, Sir. Is that why its called an Alternator? 

[Alethea Price]

On 9/17/2017 at 20:33, nicknorman said:

Hi Alethea.

Great to see you asking the right questions and listening to the answers! Lots of newcomers on here do neither!

i would suggest a "back to first principles" approach. By which I mean that whatever electrical energy you want to consume, has to be created in the first place. That is the difficult bit. Whether you consume that energy at 12v DC or 230v AC (or both) is a less important issue.

I think we are struggling in the dark until we know the engine type and alternator type / output, the generator type/ output too. That realistically determines whether it is worth having an inverter and being able to use appliances that take a lot of power.

Once you have created the energy you probably want to store it - in batteries obviously - and you want to have sufficient capacity that you can go for a day or preferably two, without having to charge the batteries.

But batteries are not a terribly easy way to store energy ( nothing is!) and so for any high power appliances it is generally considered best to generate the power at the time it is being used - ie run the engine or generator whilst you are using a high power appliance, presuming that said alternator or generator can produce sufficient power.

It sounds like the boat has mains wiring for shore power so it shouldn't be too hard to add an inverter - just remember that inverters are typically capable of proving a lot of power, and that is a lot of current at 12v.

Just on your environmental point, although running the boat's engine is easiest, typically you will have a large engine designed to propel the boat, and the load presented by the alternator is very small compared to that required to propel the boat. So if you run the engine whilst tied up just to charge the batteries, it is fairly inefficient because quite a bit of fuel is used to just keep the big engine spinning. A smaller generator, working harder, is more efficient but of course less convenient. Frame generators are cheapest but tend to be the noisiest and IMO are pretty antisocial as a result. There is no easy answer!

Thanks for the advice and support! It's great to find so many helping hands ready to assist and advice new comers. I am very much taking a back to basics approach so your guidance makes absolute sense. The advice to hope not to charge for two days is particularly valuable I will plan with that always in mind thank you.

[Alethea Price]

On 9/17/2017 at 22:31, Tony Brooks said:

I want to emphases Wotever's post about charging taking longer that four hours. taking a "typical" boat 2 to 4 hours may get you to 80% fully charged but the other 20% takes an extraordinarily long time.  If you do not fully recharge you will sooner or latter destroy your battery.

Now a word about charging. The mistake most newcomers make is to assume the rated output of a battery charger or alternator will be supplied all the time it is running. Nothing could be further from the truth. You will get the rated output for a comparatively short time, probably less than an hour) while the batteries demand more electricity than the alternator/charger can supply but very soon that alters.

As the batteries charge up they demand less current so the alternator produces less. Apart from that first short period its the batteries that control the charge NOT the alternator or charger.  The amount they take gradually reduces over the next hours until the charging current reduces until it reaches 3 to 6 amps for the 330 Ah battery set or 2 to 4 amps for the 220 Ah battery set. The last few hours will be at a very low charging currant (amps).

Taking a typical system (if there is such a thing) you can probably assume that a charger or alternator will produce an average charge of about half its rated output over 2 to four hours. From then on the average will get lower and lower. This is why it takes so long to fully charge batteries.

The alternator on a single alternator engine is likely to have a maximum output of 70 amps but 40 to 50 are probably just as common. I can get away with a single 70 amp alternator on a all but totally 12V holiday boat. I would not like to try it as a livaboard unless I was cruising for at least six hours a day.

 

Now about running the generator. Yes the 8 till 8 rule applies but a proper cocooned generator will be in a sound proofed box so anyone close by will not know its running. You can also get away with running engines and generators when mooring way out in the sticks with no boats or houses anywhere close but remember sound travels a long way over water at night.

 

PS - if you do not want to buy new batteries every few months some form of battery monitoring will be required so you do not over discharge them and also avoid wasting fuel by running the alternator/generator for longer than needed. We can advise but there are entrenched views on here. The simplest is an ammeter and voltmeter but that requires some diligent study and experience from you.

Thank you too for the advice.

 

My approximate was not including an inverter which I image would increase this time quite considerably, however my approximate came from all of my other electrical usage when calculated using the tb-training power audit. Of course I am perfectly willing to be wrong and will be preparing as much as possible in order to accommodate for a much larger charge time.

 

Thank you also for your information on charge time, rated output reduction and avoiding over discharge of batteries -  Although I am sure some new comers do make this mistake this is something I am already fully aware of and am taking into consideration with all my planning so thank you for reinforcing my understanding. I also already have intentions to buy a battery monitor.

 

Thanks again.

[Alethea Price]

On 9/17/2017 at 11:45, Alethea Price said:

Hi there new to the community so I hope it's alright to create a new thread.

The narrowboat I'm currently looking to purchase is set up with an alternator, 3 new 12v batteries, no inverter, mains cabling throughout. There is also a generator on board. I'm sorry I can't provide specifics at this point, but even general advice much appreciated.

If I continue with the purchase, I'm intending on putting on 4 Renogy 100 Watts 12v Monocrystalline Solar panels and doing my best to use the engine for power as minimally as possible (going into winter I realise that the solar is not going to give much power).

The current owner will also be putting on a new 12v Fridge if I go ahead with the purchase.

The appliances I intend on running would be a toaster, iron, TV, record player, iMac (I already own this and not looking to replace it), Laptop charger, Mobile charger. I'll be replacing all the current lighting with LED. There is currently a Washing Machine on board but the owner says its best to remove it as its on the mains (makes sense, although I would consider keeping it if anyone could provide a realistic solution).

Stove and oven will be gas, have yet to decide on a water heating system. The current gas boiler is defunct. Currently considering a new gas boiler or a back boiler for the burner (no burner currently on board looking to purchase) to fuel hot water (taps, shower) and heating (there are radiators throughout but I'm not sure if they would be necessary once I purchase the burner - she's 63'.

To be clear I will not be mooring up and 'plugging in', so everything needs to be off grid power.

My knowledge is limited so being completely open, I apologise if my questions appear naive any support appreciated:

1. Is it better to consider investing in a good inverter, or should I look at transformers on an appliance by appliance basis?
2. If primary usage was 12v, would installing an inverter affect functionality or can you run both 230v and 12v with an inverter?
3. I'm not particularly keen to keep the generator but would anyone advise that I do and why?
4. Instead of an inverter or transformers would anyone's opinion be that I simply run the engine (with alternator) when using non-12v appliances, and why? I want to reduce emissions and costs from over using the engine unnecessarily wherever possible.
5. Will the current 'all mains' wiring cause any problems with purchasing 12v appliances e.g. the fridge.
6. If I wanted to consider keeping the washing machine what would you recommend having in place?

Thank you for your advice.

Just to add to my original query I now have some more details regarding the alternator and batteries. The following information has been provided to me by the seller:

"There is a single, new, alternator, it is 120 amps ....the charging is through a diode which splits the charge to both the domestic and engine start batteries. The three batteries are all about 100 amps, two are for domestic use and one is dedicated engine start - this is common to most boats - Voltage on the generator is 240, 2.2 KVA, petrol (four stroke) and it's portable.   Both 12 and 240 volts run throughout the boat

The seller tells me he's never heard of a boat to have two alternators which seems to contradict some of the advice I've been offered on this forum. Any further input would also be much appreciated.

I will clearly need more batteries - Although I had already calculated for this, but the good news is that 12v and 240v run throughout the boat.
Regarding the generator - I'm disappointed that it is Petrol but beyond the fumes, does anyone have any input as to actions you would recommend? i.e. would you replace this with a diesel? Would you keep the petrol?

 

Thanks all!

[nicknorman]

22 minutes ago, Alethea Price said:

Just to add to my original query I now have some more details regarding the alternator and batteries. The following information has been provided to me by the seller:

"There is a single, new, alternator, it is 120 amps ....the charging is through a diode which splits the charge to both the domestic and engine start batteries. The three batteries are all about 100 amps, two are for domestic use and one is dedicated engine start - this is common to most boats - Voltage on the generator is 240, 2.2 KVA, petrol (four stroke) and it's portable.   Both 12 and 240 volts run throughout the boat

The seller tells me he's never heard of a boat to have two alternators which seems to contradict some of the advice I've been offered on this forum. Any further input would also be much appreciated.

I will clearly need more batteries - Although I had already calculated for this, but the good news is that 12v and 240v run throughout the boat.
Regarding the generator - I'm disappointed that it is Petrol but beyond the fumes, does anyone have any input as to actions you would recommend? i.e. would you replace this with a diesel? Would you keep the petrol?

 

Thanks all!

120A is a reasonable-sized alternator. The only thing to consider is that if you only have one of something, if it breaks you have none. One alternator was normal on older engines but modern engines (ie in the last 10 -15 years or so) tend to have two, one small one for the starter battery and one larger one for the domestic batteries. However if the engine only has 1 alternator, it is fairly difficult to add another one due to mechanical and space constraints. But plenty of people manage with just one.

You mention a diode splitter. This is not a very good way to spilt the charging current between the two sets of batteries as a diode intrinsically drops 0.5 to 0.7 volts. In other words, the charging voltage at the batteries is perhaps 0.7v less than the alternator is producing. This can significantly slow down charging and result in failure to fully charge.

this is not a difficult problem to fix as the diode pack can be replaced with a relay for relatively little effort. But it is something I would pay attention to when you get the boat - ie check what voltage is actually being delivered to the batteries. As we said before it all starts with generating the power and you want to have the best means available to get the power from the alternator into the batteries. Maybe it will be OK, but maybe not.

2 domestic batteries isn't really enough. We have 4.

Petrol generators are fairly common but apart from the exhaust fumes (never run the genny on the boat near a door etc) there is also an issue with the raw petrol. Petrol fumes are heavier than air and would tend to sink to the bottom of the hull, lurk around, maybe build up, and eventually go "boom" with a spark. Unlike a caravan etc, heavy gasses can't find their way out of the bottom of a boat. So take care with storing petrol on the boat and never refuel the genny on the boat.

[WotEver]

32 minutes ago, Alethea Price said:

The seller tells me he's never heard of a boat to have two alternators...

That shows nothing more than his ignorance. It's exceptionally common. 

33 minutes ago, Alethea Price said:

the charging is through a diode which splits the charge...

First thing to do would be to replace this with a VSR which will instantly give you over half a volt more charging voltage. 

34 minutes ago, Alethea Price said:

The three batteries are all about 100 amps, two are for domestic use and one is dedicated engine start - this is common to most boats...

Again, his ignorance showing. Two domestic batteries is the minimum you're likely to find. Many boats have 3, 4, 6 or even more  

36 minutes ago, Alethea Price said:

There is a single, new, alternator, it is 120 amps

That's a reasonable size. 

2 minutes ago, nicknorman said:

Petrol generators are fairly common but apart from the exhaust fumes (never run the genny on the boat near a door etc) there is also an issue with the raw petrol. Petrol fumes are heavier than air and would tend to sink to the bottom of the hull, lurk around, maybe build up, and eventually go "boom" with a spark. Unlike a caravan etc, heavy gasses can't find their way out of the bottom of a boat. So take care with storing petrol on the boat and never refuel the genny on the boat.

Also bear in mind that petrol isn't available on the canals. You generally have to walk to a petrol station to get some. 

[OldGoat]

It is strange to see that the make of engine is still not declared - it could be a bit of an elephant in the room (hopefully not) and the comment about single alternators is not in my experience  because -

Usually the standard alternator is small making it difficult to fit a larger unit in its place AND more importantly on some / many engines the drive - both pulley and how it is fitted to the engine  are not suitable or strong enough to drive the larger unit. Most - if not all higher powered alternators for best / better results need larger  and different pulleys and  belts for even reasonable results. Especially so for you because your charging window will be small.

While typing this I see two other have commented on the same issue - so I won't expand further.

I think it is important to push the point about what make and size is the engine? If it 'old' then it will be noisy and again running it too neat the 8 - 8 window will be unpopular. Being a suspicious O-G I have two possible candidates neither of which are very attractive. Please would you push that point to the vendor?

 

[ditchcrawler]

Have you actually seen this boat in the flesh?

[mross]

1 hour ago, WotEver said:

2 hours ago, Alethea Price said:

The seller tells me he's never heard of a boat to have two alternators...

That shows nothing more than his ignorance. It's exceptionally common. 

Eh???  Is it exceptional or common?  It can hardly be both   I suspect this is a typo..................

[Tony Brooks]

2 hours ago, Alethea Price said:

Just to add to my original query I now have some more details regarding the alternator and batteries. The following information has been provided to me by the seller:

"There is a single, new, alternator, it is 120 amps ....the charging is through a diode which splits the charge to both the domestic and engine start batteries. The three batteries are all about 100 amps, two are for domestic use and one is dedicated engine start - this is common to most boats - Voltage on the generator is 240, 2.2 KVA, petrol (four stroke) and it's portable.   Both 12 and 240 volts run throughout the boat

The seller tells me he's never heard of a boat to have two alternators which seems to contradict some of the advice I've been offered on this forum. Any further input would also be much appreciated.

I will clearly need more batteries - Although I had already calculated for this, but the good news is that 12v and 240v run throughout the boat.
Regarding the generator - I'm disappointed that it is Petrol but beyond the fumes, does anyone have any input as to actions you would recommend? i.e. would you replace this with a diesel? Would you keep the petrol?

 

Thanks all!

I have doubts abut the 120 amp alternator.

As has been said two domestic batteries and a single alternator suggest this is an old boat. The maximum size older boats tended to use is 70 amps with 50 amps or less being common. I have some concerns over how easy it would be to fit a 120 amp alternator in place of the typical older ones.

Giving the battery capacity in amps and saying  he has never heard of two alternator engines suggests to me he may be trying to ell you what you want to hear.  You need to visit the boat and take lots of photos.  so we can help identify the equipment.

What sounds like an open frame industrial generator makes me suspect the batteries will be totally useless as well.

As far as the power audit goes as long as you divided the Mains equipment's wattages by 10 to get 12V Amps to put into the power audit it will be near enough.

[bizzard]

1 hour ago, ditchcrawler said:

Have you actually seen this boat in the flesh?

With his clothes on I guess.    Erm, her clothes on, solly.

Edited September 19, 2017 by bizzard

[MtB]

Alethea,

A few points strike me. 

1) Fully charging a battery bank from 50% to 100% takes at least ten hours with the best charger money can buy, in my personal experience. 

2) Charging from 90% to 100% accounts for about 50% of those ten hours. As the state of charge increases the charge current progressively diminishes, and 100% can be said to have been achieved when the charge current at 14.4v has stopped reducing and remained stable for half an hour. This is why the last little bit of charge takes SO LONG.

3) The charging voltage is very critical. Mention earlier of 0.7v being lost in the split charge diode probably doesn't sound significant to you as a new person to the subject but that missing 0.7v is critically important.  It will mean your batteries will probably never get fully charged.

4) As a person whose work is frantic during the winter months I simply don't have two hours per day between the hours of 8am and 8pm when I am on the boat, to charge the batteries as is generally advised. So I have a properly silent generator I can run any time of night or day.

5) Solar only works in the brighter months of the year. Now, in mid september my six solar panels barely keep up with just the fridge. I have started using the genny to supplement the solar and in a month or so the solar will stop working completely.

6) Big inverters (i.e. 1kw and larger) encourage you to use power hungry mains appliances which will suck the life out of your two domestic batteries in a flash. I suggest you'll need four or better, six, even without an inverter.

7) Learning how to avoid wrecking your batteries is probably the most challenging aspect to learning how to live on a boat. A completely different strategy is to not bother, but buy a new set of batteries each autumn and progressively abuse and wreck them over the coming winter (by charging only partially to 80 or 90%) and consciously not worry about it. Come summer your lower power needs mean the wrecked batteries will tide you over to the next autumn battery purchase. This is a perfectly valid strategy and far lower in stress than trying to make batteries last five years. 

That's about it really. Other than to say two alternators are commonplace on narrowboats. Your seller is kidding you and cannot be trusted. 

[ditchcrawler]

49 minutes ago, bizzard said:

With his clothes on I guess.    Erm, her clothes on, solly.

I am just wondering if the OP is going from an advert and is communicating with a distant seller who may or may not have a boat for sale. They wouldn't be the first

[nicknorman]

10 minutes ago, ditchcrawler said:

I am just wondering if the OP is going from an advert and is communicating with a distant seller who may or may not have a boat for sale. They wouldn't be the first

Well it wouldn't be the first time! Yes I think you are right to sound that note of caution.

[WotEver]

2 hours ago, mross said:

Eh???  Is it exceptional or common?  It can hardly be both   I suspect this is a typo..................

Exceedingly so

[Alethea Price]

4 hours ago, nicknorman said:

120A is a reasonable-sized alternator. The only thing to consider is that if you only have one of something, if it breaks you have none. One alternator was normal on older engines but modern engines (ie in the last 10 -15 years or so) tend to have two, one small one for the starter battery and one larger one for the domestic batteries. However if the engine only has 1 alternator, it is fairly difficult to add another one due to mechanical and space constraints. But plenty of people manage with just one.

You mention a diode splitter. This is not a very good way to spilt the charging current between the two sets of batteries as a diode intrinsically drops 0.5 to 0.7 volts. In other words, the charging voltage at the batteries is perhaps 0.7v less than the alternator is producing. This can significantly slow down charging and result in failure to fully charge.

this is not a difficult problem to fix as the diode pack can be replaced with a relay for relatively little effort. But it is something I would pay attention to when you get the boat - ie check what voltage is actually being delivered to the batteries. As we said before it all starts with generating the power and you want to have the best means available to get the power from the alternator into the batteries. Maybe it will be OK, but maybe not.

2 domestic batteries isn't really enough. We have 4.

Petrol generators are fairly common but apart from the exhaust fumes (never run the genny on the boat near a door etc) there is also an issue with the raw petrol. Petrol fumes are heavier than air and would tend to sink to the bottom of the hull, lurk around, maybe build up, and eventually go "boom" with a spark. Unlike a caravan etc, heavy gasses can't find their way out of the bottom of a boat. So take care with storing petrol on the boat and never refuel the genny on the boat.

Thank you for the advice. I was planning on also having 4 batteries, and will looking into your advice regarding replacing the diode pack. Very helpful thanks

[Alethea Price]

1 hour ago, nicknorman said:

Well it wouldn't be the first time! Yes I think you are right to sound that note of caution.

Hi All, thank you for the concern. Just wanted clarify despite my being new to narrow boating I am not so inexperienced in the boating field having sailed yachts (a very different creature of course) for over 20 years. With that in mind, and with no disrespect as I'm hugely grateful for all the support everyone is offering, I hope no one thinks I'm naive enough that I would being my plans on a boat I've not seen, although I'm sure you may have come across people doing this before.

I have indeed seen her in the flesh and had a little jaunt down the canal and back. She is a real vessel and although I have no doubt the seller is trying to calm some of my concerns - ultimately to make a sale, I think he is a genuinely nice member of the community and means no ill will. He owns many a boat but this is his first time selling and he didn't have the paperwork together at the time - a story I believe to be honest.

We are also in daily contact with responses to my queries as I wait on a full survey to be conducted and will be going to view her again at the end of this week hence why I am so thankful for all your responses as I will be fully equipped to investigate the boat in full this time.

That said some of your comments are all correct. It is indeed an old boat, built in 1970, and although I don't have the spec for the engine I can tell you it is a BMC. I am of course insisting on all the information before I make any big moves and will pass on information as soon as it comes to me.

 

Thank you all again for the on going help.

[WotEver]

If it's a BMC then I'm pretty sure it could turn a 120A alternator. Hopefully @Tony Brookswill be along shortly to confirm or deny  

[Tony Brooks]

Depends what BMC. If its a 1.5 then I would not have expected that wider pulllys had been fitted to drive such a large alternator without belt problems. If its a 2.2 or larger it may have had  a wider belt as standard. One thing is sure. At that gae it would have had a 10 ofr 11AC system at one time or just possibly an ACR, certainly not 120 amps but it may have been changed,

[WotEver]

Hopefully OP will instruct the surveyor to confirm alternator and engine type. 

[smileypete]

At a very rough guess I'd say 1.5k to 2.5k minimum to get the boat kitted out to do what the OP wants, eg instant water heater and eleccy stuff.

Depends partly on the price bracket of some kit eg genny, chargers; but also whether there's gas pipes in place for the water heater already and a suitable locker for storing genny and fuel.

As long as budget is in place it shouldn't be tooo big a problem as it's all fairly standard stuff, but will take some time to sort out fully, so maybe buying a boat in the spring would be an easier option if spare time is limited in any way.

Edited September 20, 2017 by smileypete