How much is too much Solar Power and how much is just enough?

[Tony1]

26 minutes ago, booke23 said:

 

It might be worth starting a new thread on this subject.

My boat had the lithium's installed by the previous owners. It has a 160ah lithium as the house battery and a 100ah starter battery, and the engine has a 40a starter and 100amp house alternator. It looks to have been professionally installed, but the installer clearly couldn't work out how to utilise the twin alternator setup, so only the 40a alternator is utilised to charge both the lead acid and lithium.

 

I have tried to look into using the 100a alternator to charge the lithium, but it's not straightforward....connecting it direct to the lithium will destroy the alternator. I think there are smart regulated alternators you can get now that can charge lithium batteries directly, but I'm not sure! 

 

There are people who will reply here that know more than I ever will about alternators and batteries, but I can share a couple of experiences from trying to get my 100 amp alternator to charge my lithiums. 

The first disappointment was that although the domestic alternator is rated at 100 amps, it will not charge at more than 45 amps without overheating (when running at tickover). I think this limitation is fairly common on the more budget end of the engine market, such as my canaline 38. 

Turning up the revs cools it down a bit and gives you the option of a bit more charge output, but in reality you cant be at say 1400rpm all the time, its just not practical. 

 

I would have a closer look at how the lithium charging is set up now- there may be something you can use as part of an upgrade. 

He wont have connected the lithium directly to the alternator, as you said- it would overwork the alternator very quickly and damage it.

 

So do you think it is set up with the lead acid acting as a charge source for the lithium? It may be there is a split charge device in there, as is used in many campervans etc.  

Maybe there is a B2B type device in the system already? 

Either way, that alternator will probably not give you more than 45amps of charge on a continuous basis, if its anything like mine. 

 

ETA: I actually use extra B2Bs when moored, because then I can run the engine at a steady 1300rpm to keep the alternators cool.

When doing this I switch on an extra B2B for each alternator, and get an extra 30-40 amps of charge. 

 

Why dont they just give us decent capable alternators to start with??

 

 

Edited December 10, 2021 by Tony1

[booke23]

5 minutes ago, Tony1 said:

So do you think it is set up with the lead acid acting as a charge source for the lithium? It may be there is a split charge device in there, as is used in many campervans etc.  

I'm not exactly sure.......one thing is certain, the 40amp starter alternator is the only one in use as the 100amp alternator has had it's belt and wiring removed! It's all Victron kit and the battery monitor indicates that even with the engine revving quite hard, the alternator doesn't generate more than about 25-30 amps. At typical cruising rpm it's only putting in about 15amps.

There thing is, there is also 400 watts of solar on the roof. So although the alternator setup is inefficient, it works fine for me as I'm not living aboard. If I could think of a way to utilise the 100amp alternator inexpensively then I'd definitely do it!

[Tony1]

2 minutes ago, booke23 said:

I'm not exactly sure.......one thing is certain, the 40amp starter alternator is the only one in use as the 100amp alternator has had it's belt and wiring removed! It's all Victron kit and the battery monitor indicates that even with the engine revving quite hard, the alternator doesn't generate more than about 25-30 amps. At typical cruising rpm it's only putting in about 15amps.

There thing is, there is also 400 watts of solar on the roof. So although the alternator setup is inefficient, it works fine for me as I'm not living aboard. If I could think of a way to utilise the 100amp alternator inexpensively then I'd definitely do it!

 

So in summer you're covered by the solar, and in winter you only need extra charge on the days when you dont cruise much, or at all?

 

The B2B option in this case might be the cheapest, as long as you never want to increase charging capacity. I initially thought 50 amps would be ok, so I put in a single B2B, but in reality as a liveaboard its not that great in winter.

But once you start down the B2B route, having spent £300 on the B2B, it becomes very tempting to carry on.... 

 

A Renogy or a Sterling B2B unit will give you about 50amps of charge, which is better than you have now. I can only guess there is some kind of split charge relay in there at the moment to send charge to the lithium. 

You could use your starter battery as the charge source for a Renogy B2B, since they're only about £200, as compared to £300 for the Sterling unit. 

But I would check that the Renogy actually outputs 50 amps. 

 

It does depend what is there already. It may be that there is already wiring in place for a split charge relay, or it may be there is even a B2B there. 

 

The thing to bear in mind is that once you increase the charging capacity, you might then also need to think about how to manage it. How will you stop the lithium being overcharged, for example? 

You might be looking at getting a victron BMV712, plus some kind of disconnecting device for if/when the voltage gets too high.  

This is where the costs can really start to climb unfortunately.

 

 

[WillCful]

I think a new thread on this might be a good idea… maybe I’ll start one… tomorrow! 
 

Yes, I am lucky to already have a large alternator installed. I’ll take a look into a regulator for it (mastervolt) and see if this would be a good option. It would be great to just have the alternators completely separate. Hopefully I can make it cheaper if it fit it myself! There’s also the Wakespeed 500, think it’s about £600 or so for the unit. 
 

I think that in terms of the off-grid, ‘alternator charging’ community is boat dwellers are in a minority or at least a unique position, all the products seem to be geared towards single smaller car/van alternator set ups charging much smaller battery banks.

 

I already have 800 watts of solar installed but will add another 300 I think for next summer, I planned ahead! My charge controller can handle this. 

Any lithium battery bank should already be protected by BMS for over charging etc. The main thing to consider is damage that can occur to the alternator if the BMS suddenly cuts charging (in the event of full battery for example) as I understand it there needs to be some kind of small load or ‘dump’ for the alternator to continue supplying current (even a very small amount). Journey with Jono has a YouTube video about this where he uses an old lead acid battery with a small load on it (although I think a LA on its own would be fine as it would self discharge over time and never be ‘full’). He does this with loads of fancy Victron kit though and it seems way OTT, hopefully I can figure out something simpler. Maybe the mastervolt can handle this?
 

I’ve emailed Renogy about potentially increasing the output of their 60a B2B unit, if they can be paralleled this would possibly be a cost effective solution as they cost about £180 each. 

[Tony1]

34 minutes ago, WillCful said:

I think a new thread on this might be a good idea… maybe I’ll start one… tomorrow! 
 

Yes, I am lucky to already have a large alternator installed. I’ll take a look into a regulator for it (mastervolt) and see if this would be a good option. It would be great to just have the alternators completely separate. Hopefully I can make it cheaper if it fit it myself! There’s also the Wakespeed 500, think it’s about £600 or so for the unit. 
 

I think that in terms of the off-grid, ‘alternator charging’ community is boat dwellers are in a minority or at least a unique position, all the products seem to be geared towards single smaller car/van alternator set ups charging much smaller battery banks.

 

I already have 800 watts of solar installed but will add another 300 I think for next summer, I planned ahead! My charge controller can handle this. 

Any lithium battery bank should already be protected by BMS for over charging etc. The main thing to consider is damage that can occur to the alternator if the BMS suddenly cuts charging (in the event of full battery for example) as I understand it there needs to be some kind of small load or ‘dump’ for the alternator to continue supplying current (even a very small amount). Journey with Jono has a YouTube video about this where he uses an old lead acid battery with a small load on it (although I think a LA on its own would be fine as it would self discharge over time and never be ‘full’). He does this with loads of fancy Victron kit though and it seems way OTT, hopefully I can figure out something simpler. Maybe the mastervolt can handle this?
 

I’ve emailed Renogy about potentially increasing the output of their 60a B2B unit, if they can be paralleled this would possibly be a cost effective solution as they cost about £180 each. 

 

 

Far more knowledgeable folks will be able to contribute tomorrow I'm sure, but as a final point, I would agree that two B2Bs linked to your 170amp alternator are probably the cheapest solution at under £400,  but do factor in the cost of the 'source' lead acid battery (if its not your starter battery), the extra cabling, etc.

And do bear in mind that the result will have cabling that is more complex that it would be if you went for the controller solution. 

 

I don't know how the mastervolt unit handles a disconnection caused by an extreme/high voltage situation, but I imagine it must be part of the feature set. Certainly you need to check that- and on that note, what I would strongly advise, just for research purposes (and something I should have done at an earlier date) is to call Ed Shiers and have a chat about what the options, features and costs are for a controller solution. 

He is one of the very few marine electricians who really understand lithium batteries and alternator charging issues. He is also very approachable and informative, and also extremely fair and ethical in his approach. 

 

My personal advice would be not to rely on the lithium batteries' internal BMS for day to day management.

The cut-off values generally set for those internal BMS units are a bit extreme, intended for emergencies, and are not usually configurable.

E.g. you probably dont want your batteries to get down to 10.5 volts before they disconnect.  

 

So you might want to factor in some other monitoring and control devices to disconnect (or switch off) your charging units, or your loads (or both at once), such as the victron BMV712. 

So it might be worth checking if the renogy B2Bs will respond to an external 'switch off' signal from a monitoring unit such as a BMV712. 

 

 

 

Edited December 10, 2021 by Tony1

[IanD]

You can get a load dump protector for about 50 quid which will clamp any spike caused by the BMS disconnecting while the alternator is charging, Sterling do one but there might be others.

[booke23]

4 hours ago, Tony1 said:

 

So in summer you're covered by the solar, and in winter you only need extra charge on the days when you dont cruise much, or at all?

 

The B2B option in this case might be the cheapest, as long as you never want to increase charging capacity. I initially thought 50 amps would be ok, so I put in a single B2B, but in reality as a liveaboard its not that great in winter.

But once you start down the B2B route, having spent £300 on the B2B, it becomes very tempting to carry on.... 

 

A Renogy or a Sterling B2B unit will give you about 50amps of charge, which is better than you have now. I can only guess there is some kind of split charge relay in there at the moment to send charge to the lithium. 

You could use your starter battery as the charge source for a Renogy B2B, since they're only about £200, as compared to £300 for the Sterling unit. 

But I would check that the Renogy actually outputs 50 amps. 

 

It does depend what is there already. It may be that there is already wiring in place for a split charge relay, or it may be there is even a B2B there. 

 

The thing to bear in mind is that once you increase the charging capacity, you might then also need to think about how to manage it. How will you stop the lithium being overcharged, for example? 

You might be looking at getting a victron BMV712, plus some kind of disconnecting device for if/when the voltage gets too high.  

This is where the costs can really start to climb unfortunately.

 

 

 

Yes basically covered by solar in summer. In winter the engine would have to be run much longer with my setup to charge the battery than it would if I could utilise the 100amp alternator. 

There is already a Cyrix Li charge relay, a Cytrix Li load relay along with a VE.bus BMS which I think covers over charge/discharge/temperature etc!

[Tony1]

13 minutes ago, booke23 said:

 

Yes basically covered by solar in summer. In winter the engine would have to be run much longer with my setup to charge the battery than it would if I could utilise the 100amp alternator. 

There is already a Cyrix Li charge relay, a Cytrix Li load relay along with a VE.bus BMS which I think covers over charge/discharge/temperature etc!

 

My challenge is that as a liveaboard I have to generate 80-100Ah every day, and generally speaking the solar is just not going to it, over the next 2 or 3 months. 

I have 1400 watts of panels, but even today, with the sun out for an hour or two, I only got 350 Wh from the panels, so less than 30Ah- and that's going to get even worse before it improves any. 

So for me it was definitely worth upgrading the charging current, otherwise I'd be running the engine (or a genny) for at least 4 hours each day to recharge. And over 3 or 4 months, thats a lot of diesel. 

 

In terms of solutions, it might be that you could hook up the 100 amp alternator to a cheap lead acid battery, and from that to a B2B charger, then to the lithium. You would want to route it through the victron BMS though, so its properly controlled. 

 

But the B2B solutions do tend to creep up in cost though. There's the cost of a cheap lead acid source battery (unless you use the starter battery as the source), plus extra cabling, lugs, crimping tool- its surprising how much you can find yourself spending as well as the cost of the basic B2B unit.

 

There is a 30 amp victron B2B charger for about £200, and I imagine that would be fairly easy to link to the victron BMS so that the B2B charging is well controlled.

30 amps isnt that much, but I guess it depends how much you want to get from the 100 amp alternator- but I have a feeling it wont give more than 45 amps without overheating.

 

To test how much charge my alternator could give without overheating, I linked it directly to the lithium batteries temporarily, using varying lengths of 16mm and even 10mm cable to restrict the current to 70 amps, 60 amps 50 amps and then 40 amps. 

At tickover, I found the alternator overheated at anything over 45 amps. The reason I'm mentioning this is because you dont want to buy a B2B that allows too much charging. It may be that a 40 amp B2B is the most you want, if thats all the alternator can safely give out at tickover. 

 

 

 

 

 

 

 

 

[TheBiscuits]

3 minutes ago, Tony1 said:

My challenge is that as a liveaboard I have to generate 80-100Ah every day, and generally speaking the solar is just not going to it, over the next 2 or 3 months. 

I have 1400 watts of panels, but even today, with the sun out for an hour or two, I only got 350 Wh from the panels, so less than 30Ah- and that's going to get even worse before it improves any. 

 

Switch the fridge off Tony.

 

Outside temperatures in the shade - for example a box in the welldeck - have been fridge temperatures for weeks now.  Your real issue is likely to be frostburn on the lettuce until February

 

You are trying to keep the cabin hot and the fridge cold in the same small space.  Choose one of them and deal with the other.  I'd rather have a warm cabin and save the 30-40 Ah every day, but you could choose otherwise.  I know several boaters who don't heat their boat unless there is ice forming inside it, but I think they are nuts!

 

Also watch less TV - it saves power and is better for general mental health

 

[Tony1]

Just now, TheBiscuits said:

 

Switch the fridge off Tony.

 

Outside temperatures in the shade - for example a box in the welldeck - have been fridge temperatures for weeks now.  Your real issue is likely to be frostburn on the lettuce until February

 

You are trying to keep the cabin hot and the fridge cold in the same small space.  Choose one of them and deal with the other.  I'd rather have a warm cabin and save the 30-40 Ah every day, but you could choose otherwise.  I know several boaters who don't heat their boat unless there is ice forming inside it, but I think they are nuts!

 

Alas my dear Mr Biscuits; would it were so simple... 

As well as the usual odds and ends, bike trolley, spare mooring pins, tins of paint, mop and bucket, etc etc, the cratch is also currently doubling up as a coal bunker, with 8 or 9 bags of excel.

It's generally got a coating of coal dust over parts of the deck, which makes the idea of food storage a bit sub-optimal, and there just isn't much space.

 

I can now charge at 90 amps or more, so with even a little bit of solar I can get all my daily charging don in less than an hour. The fridge probably accounts for about 40-50Ah per day, which I can generate in about half an hour.

For me personally, the cost of doing that and running the fridge outweighs the faff of finding an external food storage space in winter.

Bear in mind as well that on sunny winter days, the see-through plastic windows turn the cratch into a sort of greenhouse, so its not that cold anyway. 

 

I'm one of those namby pamby boaters who doesnt do everything hard core. Boating involves enough compromises in my opinion -  I need a fridge in my life  😀

 

[TheBiscuits]

1 minute ago, Tony1 said:

As well as the usual odds and ends, bike trolley, spare mooring pins, tins of paint, mop and bucket, etc etc, the cratch is also currently doubling up as a coal bunker, with 8 or 9 bags of excel.

It's generally got a coating of coal dust over parts of the deck, which makes the idea of food storage a bit sub-optimal, and there just isn't much space.

 

It's all thermal mass which keeps the temperature ideal fridge levels.  Use a plastic box with a lid to keep coal dust off the food and the rats out.  The paint and the mooring pins can be stored in the (switched off) fridge if you are getting desparate. The bike trolley less so! 

 

5 minutes ago, Tony1 said:

The fridge probably accounts for about 40-50Ah per day

 

That's around half your daily requirements in the shortest days of winter.  You're spending twice as much on diesel as you need to be even with your fancy lithiums just to stand still.

 

7 minutes ago, Tony1 said:

For me personally, the cost of doing that and running the fridge outweighs the faff of finding an external food storage space in winter.

 

Fair enough, but please stop whining about it. 

 

9 minutes ago, Tony1 said:

Bear in mind as well that on sunny winter days, the see-through plastic windows turn the cratch into a sort of greenhouse, so its not that cold anyway. 

 

See earlier comment about coalbags in welldeck.  More thermal mass = more stable temperatures.

 

11 minutes ago, Tony1 said:

I'm one of those namby pamby boaters who doesnt do everything hard core. Boating involves enough compromises in my opinion -  I need a fridge in my life

 

When did you get your boat?  The old rule of thumb is that the second winter on a boat decides if you are cut out for being a liveaboard or not ...

 

[Tony1]

7 hours ago, TheBiscuits said:

 

It's all thermal mass which keeps the temperature ideal fridge levels.  Use a plastic box with a lid to keep coal dust off the food and the rats out.  The paint and the mooring pins can be stored in the (switched off) fridge if you are getting desparate. The bike trolley less so! 

 

 

That's around half your daily requirements in the shortest days of winter.  You're spending twice as much on diesel as you need to be even with your fancy lithiums just to stand still.

 

 

Fair enough, but please stop whining about it. 

 

 

See earlier comment about coalbags in welldeck.  More thermal mass = more stable temperatures.

 

 

When did you get your boat?  The old rule of thumb is that the second winter on a boat decides if you are cut out for being a liveaboard or not ...

 

 

I think the rough cost of running the fridge is 30 mins of diesel fuel, at the rate of about 1 litre per hour. So its maybe 40p per day, for about 100 days of the year, which is very roughly £40 per year.

 

For me personally, £40 per year is a cost I'm happy to bear if it means I don't have to use a large box for storing food and beer, in a very cramped and dusty cratch. 

I have the luxury of having food and beverages arrayed in a highly visible way so that I can rotate and organise foods by date and by type, easily and hygienically. 

I have a fridge, in a nice clean and accessible location.

For very roughly £40 per year. 

 

There are many luxuries in our lives that a cost an awful lot more than that, taken over a year.

It is my personal opinion that in my personal case, that £40 is money very well spent, and I dont see myself changing my approach in the future for economic reasons (lthough the case for environmental reasons is a more compelling one that I would potentially reconsider). 

 

Your mileage obviously varies, and you are happy not to pay to run a fridge in winter.

I hope you continue to enjoy your choice, as I will most certainly continue to enjoy mine. 

 

PS- this is my second winter, but I have to say so far I quite like it.

The bike rides for shopping are a bit more lairy on wet or icy roads, and the getting dark at 4pm thing is not great, but there is a huge plus- there is no bugger moving. 

There are no queues at facilities or locks, and no hair-raising dodging about in bridge holes, so the general cruising experience is very pleasant indeed.  

I think I'm seeing on average two boats moving in a typical 4-5 hour cruise. And by and large, I can moor wherever the hell I want for 14 days, even on the 48 hour moorings (and yes, before the nit picking legal eagles swoop, I am aware there are exceptions to that policy).  

But so far so good 😀

 

What would make me give up boating is more likely to be when I've done the whole system, and the novelty of seeing new places and things wears off. 

For me the attraction is only partly being on a boat- mostly its the ability to move your house around that appeals, which is why my saloon is starting to look like the inside of a motorhome  😀

 

Edited December 11, 2021 by Tony1

[PeterF]

9 hours ago, Tony1 said:

I don't know how the mastervolt unit handles a disconnection caused by an extreme/high voltage situation, but I imagine it must be part of the feature set.

 

The Mastervolt Alpha Pro regulator has two positive supplies like a lot of these regulators, one is the main power supply for the field coil and the other is intended to be switched to turn the regulator on and off and only has a small current demand. The control wire is, normally switched from the ignition via a relay for a standard install with lead acid, but for lithium you could wire this through the BMS "allow to charge" connection/ relay if it has enough current capacity or via another relay. The Balmar and Wakespeed units are the same.

[booke23]

10 hours ago, Tony1 said:

 

My challenge is that as a liveaboard I have to generate 80-100Ah every day, and generally speaking the solar is just not going to it, over the next 2 or 3 months. 

I have 1400 watts of panels, but even today, with the sun out for an hour or two, I only got 350 Wh from the panels, so less than 30Ah- and that's going to get even worse before it improves any. 

So for me it was definitely worth upgrading the charging current, otherwise I'd be running the engine (or a genny) for at least 4 hours each day to recharge. And over 3 or 4 months, thats a lot of diesel. 

 

In terms of solutions, it might be that you could hook up the 100 amp alternator to a cheap lead acid battery, and from that to a B2B charger, then to the lithium. You would want to route it through the victron BMS though, so its properly controlled. 

 

But the B2B solutions do tend to creep up in cost though. There's the cost of a cheap lead acid source battery (unless you use the starter battery as the source), plus extra cabling, lugs, crimping tool- its surprising how much you can find yourself spending as well as the cost of the basic B2B unit.

 

There is a 30 amp victron B2B charger for about £200, and I imagine that would be fairly easy to link to the victron BMS so that the B2B charging is well controlled.

30 amps isnt that much, but I guess it depends how much you want to get from the 100 amp alternator- but I have a feeling it wont give more than 45 amps without overheating.

 

To test how much charge my alternator could give without overheating, I linked it directly to the lithium batteries temporarily, using varying lengths of 16mm and even 10mm cable to restrict the current to 70 amps, 60 amps 50 amps and then 40 amps. 

At tickover, I found the alternator overheated at anything over 45 amps. The reason I'm mentioning this is because you dont want to buy a B2B that allows too much charging. It may be that a 40 amp B2B is the most you want, if thats all the alternator can safely give out at tickover. 

 

 

Thank you for the insight @Tony1. Certainly food for thought. However as you say the costs will mount, even if I go down the B2B charger route, I can see the thick end of £500 disappearing from my account! It might be more beneficial overall adding another solar panel, giving me 600w of solar in total. Even taking into account upgrading my MPPT it'll probably be cheaper than messing with the second alternator. 

[Alan de Enfield]

41 minutes ago, booke23 said:

It might be more beneficial overall adding another solar panel, giving me 600w of solar in total

 

 

It'll mean you have 'way to much' in the Summer, and it will do s*d all to your winter output.

If you need to use high Ah per day then you need to use what will replace it +25%

 

Over the years I have found that doing things on the cheap usually results in having to do them 2 or 3 times and ends up costing considerably more than doing it correctly in the 1st place.

[Tony1]

40 minutes ago, booke23 said:

 

Thank you for the insight @Tony1. Certainly food for thought. However as you say the costs will mount, even if I go down the B2B charger route, I can see the thick end of £500 disappearing from my account! It might be more beneficial overall adding another solar panel, giving me 600w of solar in total. Even taking into account upgrading my MPPT it'll probably be cheaper than messing with the second alternator. 

 

The only useful thing I'm able to do is to share things I've found myself, as I don't have the knowledge to recommend solutions with any confidence. 

 

In my case the charging upgrade will eventually pay for itself in saved fuel and engine running hours, whereas in your case it might take longer to give any real payback- so in your case the various solutions are perhaps more about convenience and efficiency than they are purely financial, and I can understand your reluctance to spend heavily in that scenario. 

 

Apologies for stating the obvious, but bear in mind that an extra solar panel will not be much help with charging in winter, which is when the main challenge exists. 

Also, make sure your MPPT can handle the extra charge that will come in. If not, thats an extra cost for the solar option. 

I had to buy a second MPPT when I got my extra panels, as the original one didnt have the capacity.

 

I do love having my extra solar, as even in Spring and Summer you can get plenty of overcast days, and it means you can moor in places with limited view of the sun/sky, high trees, etc, and you still get a good yield of energy. 

But in your shoes, since you do a fair bit cruising when aboard, I'd be looking hard at B2B options to take advantage of the engine running, if any of the B2Bs are feasible and controllable using your existing BMS. 

[TheBiscuits]

1 hour ago, booke23 said:

Even taking into account upgrading my MPPT

 

Check the manual.  Many MPPT units can be connected to more panels than the rated output but only to a certain limit and it's very important to not exceed input voltage.

 

 

[IanD]

The problem the OP has is that all the methods to get faster charging/reduced engine running time cost a fair bit of money, and the best one (two big poly-vee external-regulator alternators + Wakespeed or similar) costs the most -- and the real best solution (LFP batteries) costs more again...

 

And as Tony points out, more solar just increases the power in winter when he needs it from sod-all to 1.5x sod-all 😞

Edited December 11, 2021 by IanD

[Tony1]

1 minute ago, IanD said:

The problem Tony has is that all the methods to get faster charging/reduced engine running time cost a fair bit of money, and the best one (two big poly-vee external-regulator alternators + Wakespeed or similar) costs the most...

 

 

Spot on- if only my alternator setup used a poly V belt, I'd have been more willing to have a regulator installed, plus a new and bigger alternator.

It would have cost in the region of £1000 all fitted and connected, but it would have been a fantastic solution, and over ten years, it would have probably paid for itself in saved fuel, engine servicing etc 

 

But as it was, it wasnt straightforward to change my crank to the required poly V setup.

There used to be a poly V crank adaptor kit sold by the main dealer for £300 or so, but there wasnt even 100% certainty that it would be fully compatible with my engine, as it was apparently changed a year or two ago, and I was a bit hesitant because there was an element of doubt, even a small one, when committing so much money.  

 

But the main reason I didnt go for the regulator, in fairness, was because by the time I became aware of the details about it through discussions with Ed, I'd already committed so much money to the B2B approach that it made no sense to change tack. 

Live and learn, I guess...

 

[David Mack]

13 hours ago, Tony1 said:

The fridge probably accounts for about 40-50Ah per day, which I can generate in about half an hour.

 

6 hours ago, Tony1 said:

I think the rough cost of running the fridge is 30 mins of diesel fuel, at the rate of about 1 litre per hour. So its maybe 40p per day, for about 100 days of the year, which is very roughly £40 per year.

If the fridge uses 40-50Ahr per day, at 12 volts that corresponds to around 500 Whr or 0.5 kWh per day. Or 50 kWh for 100 days. If that costs you £40 in diesel then your generating cost equates to 80p per unit. Other assessments on here suggest generating your own power is quite a lot more expensive than that.

Edited December 11, 2021 by David Mack

[IanD]

8 minutes ago, David Mack said:

 

If the fridge uses 40-50Ahr per day, at 12 volts that corresponds to around 500 Whr or 0.5 kWh per day. Or 50 kWh for 100 days. If that costs you £40 in diesel then your generating cost equates to 80p per unit. Other assessments on here suggest generating your own power is quite a lot more expensive than that.

Well-insulated modern fridges use rather less energy than that, so replacing the fridge might be the easiest way to reduce his energy use...

[Tony1]

3 minutes ago, David Mack said:

 

If the fridge uses 40-50Ahr per day, at 12 volts that corresponds to around 500 Whr or 0.5 kWh per day. Or 50 kWh for 100 days. If that costs you £40 in diesel then your generating cost equates to 80p per unit. Other assessments on here suggest generating your own power is quite a lot more expensive than that.

 

I'm not well versed in the various units of energy and electricity, so I can't comment in detail on your statement.

 

My rough calculation is based on the assumption that my engine burns about 1 litre of diesel per hour, during which time it generates about 90-100Ah of charge. 

The fridge probably uses half of those Ah, hence my estimate that it takes about half an hour's worth of engine running (and half a litre of diesel) per day to run the fridge.

 

Hopefully someone more knowledgeable will be along with a better explanation and more accurate estimate. 

That said, I would happy to pay twice as much as my £40 estimate, and indeed more, to be able to run a fridge, so my approach would not change anyway, even if it turns out to be a fair bit more. 

 

 

[IanD]

Just now, Tony1 said:

 

I'm not well versed in the various units of energy and electricity, so I can't comment in detail on your statement.

 

My rough calculation is based on the assumption that my engine burns about 1 litre of diesel per hour, during which time it generates about 90-100Ah of charge. 

The fridge probably uses half of those Ah, hence my estimate that it takes about half an hour's worth of engine running (and half a litre of diesel) per day to run the fridge.

 

Hopefully someone more knowledgeable will be along with a better explanation and more accurate estimate. 

That said, I would happy to pay twice as much as my £40 estimate, and indeed more, to be able to run a fridge, so my approach would not change anyway, even if it turns out to be a fair bit more. 

 

 

What model is your fridge, and what is its rated annual consumption? You might be able to find one which uses considerably less energy...

[Tony1]

12 minutes ago, IanD said:

Well-insulated modern fridges use rather less energy than that, so replacing the fridge might be the easiest way to reduce his energy use...

 

I've also found, not surprisingly, that how high you have the thermostat makes a big difference to daily energy consumption. 

 

A couple of weeks ago I got back late and put several beers in the fridge, and then turned the thermostat to maximum cooling, in the hope that it would cool the beer down more quickly. 

 

I forgot to reduce it back to normal, and overnight the energy consumption was, I would roughly estimate, about double what it normally is. It's amazing how the quest for cool beer has advanced the speed of fridge research. Or is it just me...

 

Without doing detailed testing, my best guess is that my fridge uses on average a bit under 2 amps, which would mean a bit under 48Ah in a 24 hour period. So I reckon somewhere between 40 and 45 Ah, but I've not been bothered enough to really test it properly tbh.

 

 

Edited December 11, 2021 by Tony1

[Tony1]

6 minutes ago, IanD said:

What model is your fridge, and what is its rated annual consumption? You might be able to find one which uses considerably less energy...

 

The name on the front is 'ICEKING', but there's no leaflet for it so no idea about specs- I would guess it was new with the boat 6 years ago.

As far as I'm aware, 40-50Ah per day is about normal for an under-counter fridge without a freezer compartment? So at the moment I'm not looking for a replacement.