Lack of power on board when cruising

[prv]

plotter only used when on the move

Ok - but used all the time when on the move? At 84 watts it's a significant draw, not something to be trivially left on while not being used. Miles from the nearest obstacle, do you really need a continuous display of your surroundings? Personally I'd have a basic numbers-only GPS to keep track of position on passage and feed the DSC radio, and only turn on the plotter for any tricky bits.

Pete

 

[Robin]

I'm still struggling to understand the E120 7A consumption and apparently that is with the radar off! On our last boat we had two independent plotters running at sea, one at the chart table and one on the coachroof, one Navman 5500i and one Navman 5600. The power consumption of both together when on max brightness was 1.6A and even with the radar on (which it wasn't unless either under engine or in poor vis or in shipping lanes) we would still be using under 6A.

 

[john_morris_uk]

I'm still struggling to understand the E120 7A consumption and apparently that is with the radar off! On our last boat we had two independent plotters running at sea, one at the chart table and one on the coachroof, one Navman 5500i and one Navman 5600. The power consumption of both together when on max brightness was 1.6A and even with the radar on (which it wasn't unless either under engine or in poor vis or in shipping lanes) we would still be using under 6A.

I thought he'd said something about using 7 Amp Hours - which I assumed was his estimated average consumption over a 24 hour period? Somewhere it got shrunk into 7 amps which I agree doesn't make sense. We were looking at buying the E120 at one stage and the current consumption in daylight with full brightness on is much less than 7 amps.

 

[Robin]

I thought he'd said something about using 7 Amp Hours - which I assumed was his estimated average consumption over a 24 hour period? Somewhere it got shrunk into 7 amps which I agree doesn't make sense. We were looking at buying the E120 at one stage and the current consumption in daylight with full brightness on is much less than 7 amps.

This is what he said which I read as 7A per hour. If he meant 7Ah over a trip then that is not much and unless the trips are very short it would hardly be 'the biggest user'. Confusing!

House battery capacity is 280ah and another 80ah for the engine. The fridge is one of the super efficient Isotherme water cooled ones - uses about 2.5a per hour when on - even so do not run all the time. Biggest user is the E120 chartplotter at about 7 a/h. The Mastervolt battery gauge is really good, lets you see what everything is using and allows you switch things on/off to maximise battery life. For the first week out from the marina shore power there is little problem in keeping the batteries up at 80%+, abet after some motoring. It's in the 2/3 rd week away from shore power that the engine needs to be run longer, also power usage more carefully managed.

 

[prv]

I thought he'd said something about using 7 Amp Hours

He actually said seven amps per hour, which doesn't make a whole lot of sense.

Pete

 

[john_morris_uk]

This is what he said which I read as 7A per hour. If he meant 7Ah over a trip then that is not much and unless the trips are very short it would hardly be 'the biggest user'. Confusing!

House battery capacity is 280ah and another 80ah for the engine. The fridge is one of the super efficient Isotherme water cooled ones - uses about 2.5a per hour when on - even so do not run all the time. Biggest user is the E120 chartplotter at about 7 a/h. The Mastervolt battery gauge is really good, lets you see what everything is using and allows you switch things on/off to maximise battery life. For the first week out from the marina shore power there is little problem in keeping the batteries up at 80%+, abet after some motoring. It's in the 2/3 rd week away from shore power that the engine needs to be run longer, also power usage more carefully managed.

I agree - confusing and you can read it either way - I was only pointing our I'd read it as AmpHours.

Lots of confusion over amps and amp hours on these forums. They are units of connected (excuse the pun) but very different things.

 

[noelex]

I have measured the power consumption of the Raymarine E series on friends boats while trying to sort out their electrical problems.
I cannot remember the exact figure, but It was about 3.5A without the Radar
It seems few people look at power consumption when buying new electronics. A pity because they do vary. As others have noted many charplotters are in the 1-1.5A range
Large screens will always use a lot of power..

 

[Robin]

Yes 3.5A continuous fir the plotter without the radar is still huge, especially when you then have to add to that the autopilot, VHF, instruments and fridge and nav lights as well maybe.

The smaller plotters like the Navmans that we had last time round taking <0.8A each are much more acceptable. IMO that would put the E120 into the motorboat only category unless you have a big yacht with appropriate battery and generating power. We are newcomers to motorboating after a lifetime under sail and it is a different world when you have plenty of DC power available under way even AC as well with the generator on.

 

[mobeydick]

On the E120/radar set-up: Just check the radar is actually OFF, not in standby mode. By default, the radar goes to standby mode, and still uses significant current. Manually turning it OFF (after which it will take a few minutes to warm up if you need it again) makes a significant difference.

MD

 

[Robin]

On the E120/radar set-up: Just check the radar is actually OFF, not in standby mode. By default, the radar goes to standby mode, and still uses significant current. Manually turning it OFF (after which it will take a few minutes to warm up if you need it again) makes a significant difference.

MD

I think you might just have cracked it, given the OP's admitted confusion with the manual!

Still he needs to look at the other side of the power equation though IMO, how to get more power back in and/or quicker and how much capacity is available.

 

[Bosun Higgs]

That will be me then!

If you routinely discharge your batteries BY 75% you will need to open an account with the battery supplier unless you have really high quality deep cycle batteries which very few so called deep cycle batteries are - think golf cart batteries not the usual leisure ones.

So in your case with 2 x 110Ah you actually only have 110Ah available by keeping discharge to less than 50% (about 12.2V lowest) 110Ah used will need maybe 140Ah returned by charging because it isn't 100% efficient. However the last 20% of charge takes several hours at low amps but raised volts and is a waste of time trying to do by engine, or generator running for that matter, plugged in to AC shorepower is different. The sensible time to stop running a generator or engine system is at 80% charge, the point at which the (smart) regulator will have dropped it right back. So on your 2 x 110Ah batteries your useful capacity is from 50% (110Ah) to 80% (176Ah) so just 66Ah actually usable IF your battery is still 100% capacity capable which is very doubtful as they all deteriorate with age/use. On that basis you should be able to go to 80% by putting back 66Ah + another say 40% for efficiency loss, so about 92Ah and maybe 2 hours of engine running. The battery capacity as well as the regulator will determine how many amps the alternator puts out and it will drop as the battery gets nearer full.

Also your alternator sounds like it is running too hot, not a good idea unless you have a good stock of spare ones. Between the battery shop and the alternator shop you could be providing some serious contribution to the economic recovery!

We had one fixed 75W solar panel on a gantry, but also carried a bigger one of 120W (it would put out up to 7A in the middle of a summer sunny day) that we just laid on deck when needed. This was more efficient than the fixed one because we could move it to avoid shadows a couple of times usually per day.

The key too is to have enough battery capacity to take a charge, it is a bit like filling water tanks from a rain collector, it is wasted if the tank is too small to take more when it is still raining.. Also bigger batteries will take and demand a higher alternator output for longer before being reined back by the regulator.

So, put some decent sized batteries on board, add a solar panel and wind genny, then see how your racing results/handicap changes!

I dont see what you think is materially different in what you said and what I said though I appreciate you might just like to argue.

The OP wants to do less engine running so that means either less leccy use or more leccy generated without the engine. Storage capacity is a secondary issue once he has a base level - recharging a half depleted 600aH set up will take no less engine time than doing it twice over for a half depleted 300aH bank. And with a big bank and a small alternator you are much m,ore likely to end up with batteries 80% charged - something which is as bad for them long term as running them down to 25% charge.

Yes the alternator temperature does concern me though it does not worry Sterling who pointed out that 60C is too hot to touch. Its a ventilation issue but the point |I was making to the OP was that smart chargers did have issues and the heat of an alternator running at full output for several hours is one of them. It needs to be addressed if like me your engine compartment ventilation isnt good.

 

[Robin]

I dont see what you think is materially different in what you said and what I said though I appreciate you might just like to argue.

The OP wants to do less engine running so that means either less leccy use or more leccy generated without the engine. Storage capacity is a secondary issue once he has a base level - recharging a half depleted 600aH set up will take no less engine time than doing it twice over for a half depleted 300aH bank. And with a big bank and a small alternator you are much m,ore likely to end up with batteries 80% charged - something which is as bad for them long term as running them down to 25% charge.

Yes the alternator temperature does concern me though it does not worry Sterling who pointed out that 60C is too hot to touch. Its a ventilation issue but the point |I was making to the OP was that smart chargers did have issues and the heat of an alternator running at full output for several hours is one of them. It needs to be addressed if like me your engine compartment ventilation isnt good.

I wasn't arguing with your mathematics but with the idea of discharging batteries by 75% which is a very quick way to destroy them. Charging to 80% is what is generally considered by the cruising community as the most efficient use of an engine driven system (or generator) whilst at anchor, ie it gets the most capacity replenished in the shortest possible time. I'm not suggesting 80% charge all the time, just in the alternator scenario, not if shorepower is available or with long periods of motoring, just not at anchor.

We used never to run our batteries below 12.3V, but with two solar panels and wind (and 2 alternators with smart chargers for when motoring, never static) we rarely reached that. Indeed with our solar panels not being regulated (but monitored closely, we had ammeters and voltmeters for those and the wind generator) we had occasions when we had to disconnect a solar panel to prevent overcharging. We also very occasionally deliberately ran our batteries up to 16V as an equalisation charge (easy to do with solar panels manually controlled and some shorepower chargers also have the option). Our batteries were regular deep cycle ones, ie affordable high quality but not super dooper ones, and these were still going strong when we sold the boat 10 years on.

In your case the alternator temperature might well be OK as Sterling said. On our new boat when the previous owner first set up the 160A alternators with smart regulators the alternators did get too hot and this was measured with an infrared heat gun at around 300F. As a result the Balmar regulators were adjusted until the alternator running temps were below 212F which is considered acceptable. I don't have an infrared heat gun yet but it is on my shopping list since they only cost around £50, for checking critical engine temps (oil and exhaust especially) from time to time, but this is on a mobo not a sailboat and we don't have get you home sails anymore! The problem with stock alternators is that they quote their 'best' output, not what they can run at continuously. I think our '160A' ones are now actually set to run 120A max which they can do 24/7 without overheating.

Does that make my comments clearer? It is difficult to put into words!

 

[pvb]

Storage capacity is a secondary issue once he has a base level - recharging a half depleted 600aH set up will take no less engine time than doing it twice over for a half depleted 300aH bank.

Actually, storage capacity is the most important issue for many boatowners. All too often we read posts about people spending hundreds of pounds on 100A alternators, thinking that they'll achieve a 100A charge into their batteries. Yet, in most cases, the battery bank size is way too small to accept anything like a 100A charge.

Bigger battery banks can absorb charge faster than smaller banks, that's a simple fact. For most boatowners, increasing battery capacity is the most cost-effective charging improvement they can make after fitting a "smart" regulator.

There's also the fact that, for a given consumption, the depth of discharge is less with a bigger bank - and it's the depth of discharge which ultimately wrecks batteries.

 

[Bosun Higgs]

Bigger battery banks can absorb charge faster than smaller banks, that's a simple fact. For most boatowners, increasing battery capacity is the most cost-effective charging improvement they can make after fitting a "smart" regulator. .

I disagree. Imagine you take 100aH out of a 200aH bank and compare it with taking 100aH out of a 600aH bank. The former is 50% discharged and will charge at full rate for at least the next 60aH. The larger bank is 16% depleted and will never charge at the full rate because the charger will rapidly cut back the voltage in response to the back emf of the battery bank. Obviously depends on the size of the alternator ( a 200amp alternator would be limited by the smaller bank) which is why you are advised to balance the two, alternator and bank size.

But to go back to the OPs post, his irritation was with needing to run the engine for so much time. I share his irritation but the solution isnt battery bank size once he has the basic necessary but either using as big an alternator as possible ( they say 120 amps for the normal single drive belt) combined with a smart charger or alternative inputs ( solar in my view) or reducing consumption.

To put it another way, your fuel tank size does not affect your speed, only the distance between fuel stops. And it takes just the same amount of time to put 30 gals in a 50 gal tank as in a 200 gal one.

 

[prv]

it takes just the same amount of time to put 30 gals in a 50 gal tank as in a 200 gal one.

Not if the 200 gallon tank has a bigger filler cap and can use the high-speed diesel pump at the trawler dock across the harbour.

I don't claim to be an expert on batteries, just saying your analogy doesn't really prove or demonstrate anything.

Pete

 

[pvb]

I disagree. Imagine you take 100aH out of a 200aH bank and compare it with taking 100aH out of a 600aH bank. The former is 50% discharged and will charge at full rate for at least the next 60aH. The larger bank is 16% depleted and will never charge at the full rate because the charger will rapidly cut back the voltage in response to the back emf of the battery bank. Obviously depends on the size of the alternator ( a 200amp alternator would be limited by the smaller bank) which is why you are advised to balance the two, alternator and bank size.

Why would the voltage be "rapidly cut back"? Alternators, even with add-on regulators, tend to run at a fairly constant voltage.

But to go back to the OPs post, his irritation was with needing to run the engine for so much time. I share his irritation but the solution isnt battery bank size once he has the basic necessary but either using as big an alternator as possible ( they say 120 amps for the normal single drive belt) combined with a smart charger or alternative inputs ( solar in my view) or reducing consumption.

Do you have any idea what battery bank capacity you'd need to accept charge at 120A for more than a few minutes?

To put it another way, your fuel tank size does not affect your speed, only the distance between fuel stops. And it takes just the same amount of time to put 30 gals in a 50 gal tank as in a 200 gal one.

That really is a fatuous comparison.

 

[kyleview]

Superb discussion and many great recommendations - THANKS. As an FIEE / FIET who does know a lot about these things I have decided / concluded to stay with what I have got and make sure that I get to shore power just every 2/3 weeks to top up. As I have no plans to sail the Atlantic this seems within my reach to be able to keep the fridge, chartplotter, lights, etc working sensibly on an extensive cruise - round Ireland, up West Coast, etc. I have picked up a number of tips in the forum on the E120 which are most helpful - Thanks.