Advice on installing an inverter

[brich]

I've found a nice 50' narrowboat which I'm considering purchasing.

 

It seems to have been used mainly as a live-aboard, spending almost all of it's life (about 12 years) moored up and attched to shore power to run a couple of TVs (at 40W each) , a Microwave at 700W, a small Candy Washing machine about 1500W and a slimline fridge freezer, say 120W. The 12V circuits are completely separate. The engine is a Vetus 3 with a standard 12V 75A alternator. It has two 110Ah batteries which appear to be used to provide power for both leisure and engine start (a bit unusual but probably soluble). I'm intending to cruise rather than moor, so most of the time we would be without shore power.

 

I'm thinking about installing a 2Kw pure sine inverter, with the idea of being able to run the fridge freezer all the time, the TV and Microwave on demand, and the washing machine occasionally (when there are no flat stones about) with the engine running so that the alternator assists when needed. However, I think I need to add some more batteries into the system - I was thinking 4 x 110Ah and a separate 80Ah or similar for engine start. But now I'm not sure that the 75A alternator will be enough to keep this battery load topped up, even if I drop in a battery management system.

 

Can anybody suggest if this set-up is likely to work, or suggest what might be feasible?

 

Thanks

 

Brian

[steelaway]

I've found a nice 50' narrowboat which I'm considering purchasing.

 

It seems to have been used mainly as a live-aboard, spending almost all of it's life (about 12 years) moored up and attched to shore power to run a couple of TVs (at 40W each) , a Microwave at 700W, a small Candy Washing machine about 1500W and a slimline fridge freezer, say 120W. The 12V circuits are completely separate. The engine is a Vetus 3 with a standard 12V 75A alternator. It has two 110Ah batteries which appear to be used to provide power for both leisure and engine start (a bit unusual but probably soluble). I'm intending to cruise rather than moor, so most of the time we would be without shore power.

 

I'm thinking about installing a 2Kw pure sine inverter, with the idea of being able to run the fridge freezer all the time, the TV and Microwave on demand, and the washing machine occasionally (when there are no flat stones about) with the engine running so that the alternator assists when needed. However, I think I need to add some more batteries into the system - I was thinking 4 x 110Ah and a separate 80Ah or similar for engine start. But now I'm not sure that the 75A alternator will be enough to keep this battery load topped up, even if I drop in a battery management system.

 

Can anybody suggest if this set-up is likely to work, or suggest what might be feasible?

 

Thanks

 

Brian

 

Hi Brian

 

IMHO You are right even with a alternator charge controler you will need to run the engine for far to long for all this to be feasable.

You will need at least another 75A alternator, 110A would be better, and with a charge controler you will be achieve reasonable running times.

Maybe 5 hours a day

Running a washing machine will still be a problem

 

Alex

[chris w]

A 2KW inverter may also be slightly marginal to run a 1500W washing machine. It may not allow the motor to start up when the heater is also on. A 3KW inverter would solve that problem.

 

Your 700W microwave will consume about 1400W of power when it is ON. The 700W figure is only the microwave power but microwave ovens are only around 50% efficient in terms of the power they draw from the 240v supply.

 

Here's a rough power audit: (ignoring the washing machine for the moment)

 

2 TV's for 4 hours each and 40W each = 320WH per day (WH = watt.hours)

Microwave for say 15 minutes per day @ 1400W = 350Wh per day

Fridge @ 120W @ 50% duty cycle for 24 hours = 1440WH per day

 

Total WH's = 2110 WH. We'll divide this by 10v rather than 12v to allow for the inefficiencies of the inverter. This gives 211AH (Ampere.Hours) per day which is about double what a "typical" narrow boater would use. It's a very high consumption.

 

You would need about 600AH of batteries to cope with this for one day. This is because you mustn't discharge below 50% to avoid damaging the batteries and are unlikely to have the time to charge above 80%, so only 30% of the battery is accessible. Thus, 211/0.3 is approximately 600AH.

 

The other problem is that you need to replace almost 50% more than you take out owing to battery physics charging inefficiencies. So you will need DAILY to replace around 300AH. This will take about 15 hours!!!!! See why this is not going to work. It's usually always the recharging that is the problem.

 

We have also not taken into account the washing machine yet nor indeed pumps and lighting. The pumps will add around 5AH per day and the lights around 20-30AH per day. Although the alternator will be supplying current all the time you are cruising, it will be mainly used by the fridge because TV will be in the evening or early morning and likewise the microwave. So the alternator will keep the fridge going during the day but will not add much to the depleted batteries from the night before.

 

In my opinion, this is not a workable solution. You need to get a 50W fridge and consider dumping the microwave. This would cut your daily consumption by about 100AH per day - a huge amount of saving.

 

 

Chris

Edited May 19, 2009 by chris w

[Gibbo]

This is workable but with a few changes and compromises:-

 

You're going to need about 500Ahr + of domestic batteries plus your engine start.

 

You either need to add another bigger alternator just for the domestics or another alternator of the same size and parallel them.

 

Your washing machine will run happily from a 1500 watt inverter but do not use the inbuilt water heater. Switch it off completely. Make sure you either wash with cold water or you put hot water into the washing machine.

 

Heating anything from battery power is the closest thing to insanity that it is possible to get on a boat.

 

Gibbo

[chris w]

You either need to add another bigger alternator just for the domestics or another alternator of the same size and parallel them.

 

 

Gibbo

We have the circuit for you

[brich]

A 2KW inverter may also be slightly marginal to run a 1500W washing machine. It may not allow the motor to start up when the heater is also on. A 3KW inverter would solve that problem.

 

Your 700W microwave will consume about 1400W of power when it is ON. The 700W figure is only the microwave power but microwave ovens are only around 50% efficient in terms of the power they draw from the 240v supply.

 

Here's a rough power audit: (ignoring the washing machine for the moment)

 

2 TV's for 4 hours each and 40W each = 320WH per day (WH = watt.hours)

Microwave for say 15 minutes per day @ 1400W = 350Wh per day

Fridge @ 120W @ 50% duty cycle for 24 hours = 1440WH per day

 

Total WH's = 2110 WH. We'll divide this by 10v rather than 12v to allow for the inefficiencies of the inverter. This gives 211AH (Ampere.Hours) per day which is about double what a "typical" narrow boater would use. It's a very high consumption.

 

You would need about 600AH of batteries to cope with this for one day. This is because you mustn't discharge below 50% to avoid damaging the batteries and are unlikely to have the time to charge above 80%, so only 30% of the battery is accessible. Thus, 211/0.3 is approximately 600AH.

 

The other problem is that you need to replace almost 50% more than you take out owing to battery physics charging inefficiencies. So you will need DAILY to replace around 300AH. This will take about 15 hours!!!!! See why this is not going to work. It's usually always the recharging that is the problem.

 

We have also not taken into account the washing machine yet nor indeed pumps and lighting. The pumps will add around 5AH per day and the lights around 20-30AH per day. Although the alternator will be supplying current all the time you are cruising, it will be mainly used by the fridge because TV will be in the evening or early morning and likewise the microwave. So the alternator will keep the fridge going during the day but will not add much to the depleted batteries from the night before.

 

In my opinion, this is not a workable solution. You need to get a 50W fridge and consider dumping the microwave. This would cut your daily consumption by about 100AH per day - a huge amount of saving.

 

 

Chris

 

Thanks Chris and Gibbo - you've confirmed my thoughts that this was not really workable. So for Plan B...

 

A 1500W pure sine inverter - perhaps one that autoswitches betweeen shore and inverted power automatically

 

Two TVs as before - 320 Wh per day

 

I'll dump the microwave - not a problem.

 

I'll dump the domestic fridge freezer and replace with something like the 12V INDEL fridge from Roadpro (rated at 19W per hour, lets say 500 Wh per day) unless I should be looking for a small mains fridge? http://tinyurl.com/q9h9hq

 

To replace the Candy I'll get a Thompson X-11-1 twintub which is rated at 350W wash-motor and 165W spin motor, and hot filled from the calorfier or Morco gas heater. I'm told that these are simple 'traditional' washing machines. 30 minutes washing and 5 minutes spin is 175Wh plus 14Wh, say 200Wh: http://tinyurl.com/qdbjx3

 

That gives a budget of about 1000 Wh which is about 100Ah - this would almost be within the capacity of the existing batteries. Does this sound right?

 

I think I should still fit the extra engine battery, and extra 110Ah leisure battery and the alternator controller.

Edited May 19, 2009 by brich

[denboy]

Thanks Chris and Gibbo - you've confirmed my thoughts that this was not really workable. So for Plan B...

 

A 1500W pure sine inverter - perhaps one that autoswitches betweeen shore and inverted power automatically

 

Two TVs as before - 320 Wh per day

 

I'll dump the microwave - not a problem.

 

I'll dump the domestic fridge freezer and replace with something like the 12V INDEL fridge from Roadpro (rated at 19W per hour, lets say 500 Wh per day) unless I should be looking for a small mains fridge? http://tinyurl.com/q9h9hq

 

To replace the Candy I'll get a Thompson X-11-1 twintub which is rated at 350W wash-motor and 165W spin motor, and hot filled from the calorfier or Morco gas heater. I'm told that these are simple 'traditional' washing machines. 30 minutes washing and 5 minutes spin is 175Wh plus 14Wh, say 200Wh: http://tinyurl.com/qdbjx3

 

That gives a budget of about 1000 Wh which is about 100Ah - this would almost be within the capacity of the existing batteries. Does this sound right?

 

I think I should still fit the extra engine battery, and extra 110Ah leisure battery and the alternator controller.

If its the small candy t 10 itll work off a 1000w inverter

[chris w]

Thanks Chris and Gibbo - you've confirmed my thoughts that this was not really workable. So for Plan B...

 

A 1500W pure sine inverter - perhaps one that autoswitches betweeen shore and inverted power automatically

 

Two TVs as before - 320 Wh per day

 

I'll dump the microwave - not a problem.

 

I'll dump the domestic fridge freezer and replace with something like the 12V INDEL fridge from Roadpro (rated at 19W per hour, lets say 500 Wh per day) unless I should be looking for a small mains fridge? http://tinyurl.com/q9h9hq

 

To replace the Candy I'll get a Thompson X-11-1 twintub which is rated at 350W wash-motor and 165W spin motor, and hot filled from the calorfier or Morco gas heater. I'm told that these are simple 'traditional' washing machines. 30 minutes washing and 5 minutes spin is 175Wh plus 14Wh, say 200Wh: http://tinyurl.com/qdbjx3

 

That gives a budget of about 1000 Wh which is about 100Ah - this would almost be within the capacity of the existing batteries. Does this sound right?

 

I think I should still fit the extra engine battery, and extra 110Ah leisure battery and the alternator controller.

 

 

That sounds much better. Don't go for a mains fridge if you can avoid it, they are about 30% less efficient than a 12v version of which about half of this is the inverter losses.

 

For 100AH per day get about 300AH of batteries minimum PLUS a separate start battery.

 

Chris

[wonderdust]

I'll dump the domestic fridge freezer and replace with something like the 12V INDEL fridge from Roadpro (rated at 19W per hour, lets say 500 Wh per day) unless I should be looking for a small mains fridge? http://tinyurl.com/q9h9hq

 

Also have a look here, we have the larder fridge very pleased with it!

[chris w]

I'll dump the domestic fridge freezer and replace with something like the 12V INDEL fridge from Roadpro (rated at 19W per hour)

Sorry to be pedantic but, just for future reference, a device of 19W power isn't 19W per hour........ it's just 19W. The ENERGY used over an hour is 19 watt.hours (19WH).

 

Chris

[Gibbo]

brich that sounds much better.

 

You could keep your existing washing machine and just use it with a hot fill so its heater doesn't come on. Power consumption will then be about the same as the twin tub you propose.

 

Having said that, I have a Candy studio washer and it's coming out to be replaced with one of those small twin tubs. Reasons are it takes a bigger load, washes quicker, and I'm hoping it doesn't vibrate as much.

 

I still think you're going to need the extra domestic batteries. You're very marginal as it is.

 

As regards the alternator controller it depends on what voltage your alternator charges at. Modern ones run at a higher voltage than the older ones and in that case the external controller will do nothing or next to nothing.

 

Gibbo

[chris w]

As regards the alternator controller it depends on what voltage your alternator charges at. Modern ones run at a higher voltage than the older ones and in that case the external controller will do nothing or next to nothing.

 

Gibbo

Although that's not what we who have them fitted find........ to bring up an old chestnut.

[Gibbo]

Although that's not what we who have them fitted find........ to bring up an old chestnut.

 

Yes it's getting to be a very tiresome chestnut.

 

It's just because you see an increase in current going into the batteries and assume that means they're charging faster. Which is an incorrect assumption.

 

If you are so adamant that I am incorrect, then why not charge them at 200 volts and do it in 5 minutes. Don't say that's a silly question. Actually answer it and you may see where your error lies.

 

Gibbo

 

Edit: The alternator on Lionheart has no internal controller. It therefore has an external controller. I can adjust the charge voltage to more or less any voltage I want. I therefore know that acceptance at the gassing voltage charges them faster than any other voltage. Completely irrespective of the measured current into the battery (which isn't all charge current). That's in addition to many years of research whilst working for my own company and also for the two biggest names in the game.

Edited May 20, 2009 by Gibbo

[chris w]

If you are so adamant that I am incorrect, then why not charge them at 200 volts and do it in 5 minutes. Don't say that's a silly question. Actually answer it and you may see where your error lies.

 

Gibbo

Now you're just being silly.......

[Gibbo]

Now you're just being silly.......

 

I knew you'd say that.

 

Actually answer it (if you can) and you will see why you are wrong.

 

Why is charging above the gassing voltage (ie at 14.8 volts) good by your standard but going even higher is not?

 

Answer the question.

 

Gibbo

[Justme]

Using that twin tub you will wash in 8-12mins (or less for lightly soiled stuff) & have 2 or 3 spins (rinse cycle) of 2-3 mins. Or thats what we use any way.

 

Justme

[chris w]

I knew you'd say that.

 

Actually answer it (if you can) and you will see why you are wrong.

 

Why is charging above the gassing voltage (ie at 14.8 volts) good by your standard but going even higher is not?

 

Answer the question.

 

Gibbo

Because a small amount of gassing (IF there is any at that voltage) will still charge our batteries faster. Thos of us who have alternator controllers KNOW that once installed they make a hell of a good difference. You are the only one involved in manufacturing electronic systems who thinks like that.

 

Why not send an open letter to Charles Sterling or Adverc for example asking them to debate your claims so that we can have both sides of the professional argument in writing.

 

Chris

[Gibbo]

Because a small amount of gassing (IF there is any at that voltage) will still charge our batteries faster.

 

That sounds like you just made that statement up because you want it to be true. Not because it is based on any sort of understanding of the subject.

 

Thos of us who have alternator controllers KNOW that once installed they make a hell of a good difference. You are the only one involved in manufacturing electronic systems who thinks like that.

 

You have no idea how funny that is!

 

Having been a practicing electronics engineer for well over 25 years dedicated to this one single field, having worked for over 15 years for the two biggest names in the industry, having been a part of the design team for one of the biggest selling lead acid battery chargers ever produced, having consulted for the biggest ever European battery charger manufacturer in order to correct their slightly dodgy design, having designed one of the most popular alternator controllers currently on the market, having single handedly designed the most acurate battery SoC meter in the world, currently consulting for the biggest military power supply company in the world on battery charger and monitoring devices and knowing when a transistor is saturated or not I think I am in a much better position to know about the subject than a boater with a battery boiler and a multimeter.

 

I am not the only person that thinks like this. Try speaking to real engineers in this field instead of a few end users.

 

Gibbo

 

Why not send an open letter to Charles Sterling or Adverc for example asking them to debate your claims so that we can have both sides of the professional argument in writing.

 

And as for this bit: Why do you think the Adverc cycles around the gassing voltage?

 

Do you think they did it for a giggle to confuse boaters when looking at their voltmeter? Or do you think, just possibly, it might have something to do with the fact that remaining above the gassing voltage slows charging down?

 

Gibbo

[chris w]

I am not the only person that thinks like this. Try speaking to real engineers in this field instead of a few end users.

 

Gibbo

So name some of these mythical people and let's get their opinion. I'm sure the controller manufacturers would only be too happy to join in.

 

Chris

[Gibbo]

So name some of these mythical people and let's get their opinion. I'm sure the controller manufacturers would only be too happy to join in.

 

Chris

 

Mythical. LOL. You're a funny guy. I worked with them for many years. I don't think they'd appreciate having their names rattled round an internet forum.

 

Gibbo

[chris w]

Mythical. LOL. You're a funny guy. I worked with them for many years. I don't think they'd appreciate having their names rattled round an internet forum.

 

Gibbo

Why not if they agree with you? Talk to them privately then and ask them to contribute. I have just emailed all the major manufacturers of alternator controllers stating that you claim that their controllers have no real benefit for internal regs from 14.2v and over. I have asked them to to counter your view with facts rather than marketing stuff that alternator controllers are a waste of money.

Edited May 20, 2009 by chris w

[Gibbo]

Why not if they agree with you? Talk to them privately then and ask them to contribute. I have just emailed all the major manufacturers of alternator controllers stating that you claim that their controllers have no real benefit for internal regs from 14.2v and over. I have asked them to to counter your view with facts rather than marketing stuff that alternator controllers are a waste of money.

 

Good. I await the results.

 

Oh, be sure to email the engineering department not the marketing department. Oh wait, they'll pass it on to marketing as it's a marketing issue. I guess you'll have a hard time pulling this off seeing as you don't know any of the engineers.

 

Gibbo

[chris w]

Good. I await the results.

 

Oh, be sure to email the engineering department not the marketing department. Oh wait, they'll pass it on to marketing as it's a marketing issue. I guess you'll have a hard time pulling this off seeing as you don't know any of the engineers.

 

Gibbo

I trust your guys will contribute as well.

[brich]

Sorry to be pedantic but, just for future reference, a device of 19W power isn't 19W per hour........ it's just 19W. The ENERGY used over an hour is 19 watt.hours (19WH).

 

Chris

 

Sorry, I copied the detail of the RoadPro website spec where it said the average hourly consumption was 19W (1.6A at 12V) and forgot to put the H afterwards.

 

I'm sorry I asked about the alternator controller - didn't mean to stir up an argument!

 

Brian

[brich]

As regards the alternator controller it depends on what voltage your alternator charges at. Modern ones run at a higher voltage than the older ones and in that case the external controller will do nothing or next to nothing.

 

How do you determine the charging voltage - from the manufacturers spec sheets or do you need to measure it directly under some specific conditions? Also, do you need to be aware of the type of batteries you have when choosing a controller (e.g. open vs sealed lead acid batteries)?

 

Thanks

 

Brian