Electrical charging question

[WotEver]

Smartgauge + relay. When SOC goes below 50% all domestic 12v power turns off apart from a small LED sign that says "candles in cupboard".

Great idea ?

[Arthur Brown]

As a totally alternative suggestion, try to enforce that every day that the boat is occupied the engine is run at just above tickover (insert number here say 1200rpm but that's a lot for a Kelvin!) for say 4 hours including real cruise time,

 

This way if you cruise then you do the four hours easily, if you sit there you must put in an engine period sufficient for the engine to make enough electricity, and hot water!

 

Alternate plan two -fit a smaller inverter.

 

Alternate plan three - fit more solar panels.

 

Alternate plan four - reduce the available current at 240v by reducing the breaker ratings, a 6a breaker will let a lot of power be drawn from the inverter A 2A breaker may keep consumption within that which an impaired recharge cycle will provide.

 

Alternate plan five - Look at the inverter, does it have a third "input" connector for remote switching? If so enable this so that it's really easy to turn the inverter OFF (as opposed to stand by) This may save some quiescent running losses.

[Arthur Brown]

Look for some places where the boat can access shoreline overnight and fit charger and lead. Establish a requirement to plug in and recharge from mains for money once per week.

Some sockets only live when real mains is connected.

[1st ade]

The thing is, a Smartgauge is the best available for this task but still quite a long way off ideal.

 

Non-technical sharers will quickly learn the lights stay on and the vacuum still works when the Smartgauge drops below 50%, and that the notice saying 'Recharge at 50%' can safely be ignored with no apparent consequences.

 

A "Smartgauge 2" is needed. This would be calibrated to display "0%" when the charge has actually fallen to 50%, and should the true state of charge then continue to fall to say 49% or 48%, the Smartgauge 2 sends a signal to a companion device which disconnects the domestic service to protect the batteries.

 

This way, the battery state of charge meter behaves in much the same way as a diesel fuel gauge.

 

Finally yes the Smartgauge 2 needs installing in the galley or saloon in full view of were the high power consumption devices might be used, not hidden away in a cupboard or out of sight.

 

I have my own Smartgauge on the wall in my galley and I can see it from here as I type this. Display is set to permanently ON at minimum brightness and I am always aware of the SoC. I can see it and read it from 20ft with no need to approach it and press buttons. Like the sound of the ecofan keeps me aware of the state of the stove, the SG display keeps me constantly aware of the SoC.

 

Currently it is reading 22%. yes, really!

 

Mike (and others) have put their finger on the real problem even if you have instrumentation. Diesel - engine stops when empty. Gas - Cooker stops when empty. Water - tap / shower stops when empty. Electricity - Why (especially to those used to houses, mobile phones and laptops) should I believe that 50% is empty when plainly nothing has stopped working and I can get many more hours out of the battery?

[WotEver]

That's what the big sign is for.

 

Or the disconnect relay

[Top cat]

Batteries don't suddely die when you go below 50%, but the rate that they wear out goes up the deeper you discharge them. The 50% figure come from battery sizing calculations for application with consistent discharges and it turn out that if you design your system for a 50% disharge thats the most cost effective trade ofv between battery cost and life.

 

So while its good practice to limit your discharge to 50% a 60% limit is kinder to them and so on till you get to very small discharges.

Its having the battery spending a lot of time in a semi disharged state that does a lot of damage. So taking them down to say 45% and promtly recharging is less damaging than spending a few days between 60 and 75%.

 

Back to the share boat problem, if you could arrange for a mains hook up at your change over mooring, fit a good charger and ask your syndicate to plug in on arrival , and disconnect last thing before departure, I'm sure that would help your batteries last a bit longer. Thats what we did on the share boat I was on, I recall we got c tek 25, which wasn't expensive or difficult to use or install. Worked for us, only changed batteries once in the 10 years I was with them.

 

Top Cat

[ditchcrawler]

Obviously batteries are not hyper expensive, and if I was running a share boat with a load or people I didn't always fully know and that might not be fully up to speed with what was or was not ok with batteries I might well take three years as ok which would be on a par with for instance people living off grid and not putting enough in over winter.

But equally as I say, assuming the boat is moving most days, and you are not overly discharging the battery then I would expect more like 5-6 years out of a set of a generic set of 110Ah batteries before performance is significantly reduced, and if a £120 SoC gauge and a fourth battery make the difference between 9 months and five years you have saved a packet and likely helped the planet to boot.

 

You should be able to tell if the voltmeter is on the domestics or start battery fairly easily by looking at as you crank the engine. I would expect if you only had one and it was by the fuseboard i it would be on the domestics, but equally if was in with the engine gauges, the reverse would be true, and it could be on either.

An accurate voltmeter will give a plausible state of charge reading after a suitable period of off-load. Say if the fridge is only run during the day, and you read it first thing in the morning before running the pump to have a wash. But equally your average 'automotive' type 50mm round gauge you often get bundled with the rev counter will only tell you if its pancaked or not, and on-load voltage is also largely meaningless.

 

If the boats never plugged in then a charge is pointless. And if the alternator is getting the batteries properly back to being charged there should be no need, we have a charger and use in from time to time including when working on the boat with mains or a generator running, but never over summer, and we get 6-8years out of a set of four 110Ah batteries.

 

 

 

Daniel

We had one owner allowed his daughter and son in law to use the boat, they sat up all night, all the lights on playing cards, running the ebispatcher and only moving to the pub during the day, we also had a Rediline and Microwave, result goosed batteries.

[nb Innisfree]

50% SoC/DoD has turned into a holy grail.

 

Another 50% 'rule' states that the most efficient way to replace power is to stick to a partial state of charge routine, i.e. do bulk charging only by discharge to no lower than 30% SoC and charge to 80% SoC or when acceptance voltage is reached (30% to 80% =50% hence the idea that batteries are only good for half of their stated capacity) Advisable to do an occasional 100% charge to equalise (by trial and error I decided weekly to be best) I found this routine to be the best compromise though it has to be remembered that as batteries deteriorate bulk charge needs to be gradually extended into absorption charge

Edited January 23, 2016 by nb Innisfree

[DHutch]

I wonder if it would help Cheshire cat’s people to understand what the boat batteries hold in the way of energy would be to think about it as kWh (a unit of energy at home).

 

3 x 110Ah batteries so that is a total capacity of 330Ah or 3.9kWhs approx and [half that is therefore just under 2kWh]

 

That vacuum cleaner used to clean the boat [for 2 hours] uses 1.00kWh or more than the sensible usable charge. The batteries will probably run the vacuum for 3 hours or so by taking the batteries down to flat and that damages the batteries and shortens their lives.

 

...effectively an off grid live-a-board and a lot of live-a-boards have in excess of 440Ah batteries ...

 

I basic education of roughly what certain items use is not stupid and may help keep within a reasonable SoC (say always above 50%) but its also needs to be very non-technical for most people, and for instance I just cant see you using a vacuum cleaner for two hours to clean boat and which point the assumption is flawed from the off even if well intended.

 

A holiday/share boat is quite different from most liveaboard scenarios and typically the are clocking up the hours moving the boat, the difference between living on an off-grid mooring, and staying for a week on a boat that's doing 6-8hours motoring a day is huge, even with the 'change over day' tendency.

I can see their eyes glazing over at the beginning of the conversation. These folks are non-technical. My wife doesn't know a kWh from a gallon of petrol but she knows that if we have too many lights on over winter the bill gets bigger and I'd suggest from what we've heard that CC's owners are much the same.

 

Agreed. But I would also augment that with the fact that two 16W florescent lights even for six hours (0.2kWh) uses a lot less power than a 2kW hairdrier/straighteners for half an hour (1kWh) so sitting in the dark to do you hair doesnt help a lot, compared to using a second towel to get it a dry as you can before combing it dry over an hour and a half.

 

Similarly using the microwave for catering and brew reheating will mash power out of the batteries and while a laptops power consumption isnt super huge its a lot more than the lights will be and you can having it on for hours and hours!

 

 

 

 

Daniel

[DHutch]

Tungsten bulbs have been replaced by leds but we've still got five or six fluorescent striplights.

You can do all the sums you like, and there is for instance an led version of the 'Trilite' which is one of the more common fluorescent strip lights on boats. However the trilite is clearly designed to be fitting in vans and the colour temperature is quite painful in a boat (we have them in our engineroom) so we have just replaced a couple of our 16w 2D fluorescent lights light-for-like because they work of the shelf, the colour is nice, and in the grand scheme compared to what we put back in running the engine its not worth the effort. The ones which still work I have managed to get replacement covers for them at a reasonable price even with minimum order of ten units.

 

If you where looking to turn them LED assuming they still look ok and the covers are not badly yellowed I would seriously considered the strips/rolls of warm white LEDs cut up and laid inside the old covers with the tubes removed.

 

##

Non-technical sharers will quickly learn the lights stay on and the vacuum still works when the Smartgauge drops below 50%, and that the notice saying 'Recharge at 50%' can safely be ignored with no apparent consequences.

Horse to water I guess.

 

As said, its not a drop-dead level, and whether you bring it back the following morning or leave it like that for a week is very relivent too, but if the next set of batteries last 9 months again, at least people will know why and prehaps either take it more seriously, or talk about getting a larger bank.

We had one owner allowed his daughter and son in law to use the boat, they sat up all night, all the lights on playing cards, running the ebispatcher and only moving to the pub during the day, we also had a Rediline and Microwave, result goosed batteries.

I must said, I dont know what a eber uses, but the hire boats we where on when we did a stag weekend in bath had diesel central heating and having had that running all day and into the evening (it was winter) the inverter had dropped out by the time we got back from a night on the town. Much to everyones (phones) disappointment!

 

 

Daniel

[WotEver]

 

Agreed. But I would also augment that with the fact that two 16W florescent lights even for six hours (0.2kWh) uses a lot less power than a 2kW hairdrier/straighteners for half an hour (1kWh) so sitting in the dark to do you hair doesnt help a lot, compared to using a second towel to get it a dry as you can before combing it dry over an hour and a half.

I don't disagree in principle but I don't believe the info would sink in. However, if they use the hair dryer and see the ammeter suddenly jump to a high number and the SmartGauge start counting down quickly then I think they'll get the idea much faster.

 

Tony

[Loafer]

I can't find the post I want to quote, but this false quote is similar:

 

'With a Smartgauge and an ammeter you have all the info you need'... or summat.

 

That statement was made about 2 months ago, at the beginning of all the Smartgauge 'tennis' that has been going on. After all the ensuing arguments and personality questioning, that statement is still true.

 

If you're electrically challenged, get a Smartgauge (or nothing).

 

If you want to know when you SHOULD recharge, get a Smartgauge.

 

If you want to see your charge current, get an ammeter. A shunt-based ammeter is as cheap as chips nowadays.

[Loafer]

No, Loafer has a 'proper' boat

 

Tony

 

Hoo, yes indeed. No digital nonsense here, well, except for 2 iPhones, a McBook, an McIpad, 2 WiFi mongles, BMV 600 and stuff like that!

 

But we do have some nice old analog ammeters!

[Theo]

If you can run to an reasonable voltmeter as well then with a bit of research on your part the other users will have a fair idea when something goes wrong.

 

Get a laminated card with the alternator's regulated voltage on it, its rated output, and the tail current you are happy to accept as indicating charged batteries.

 

Let it be known that:

 

1. The ammeter should be reading close to the alternator's rated output when revving immediately after first start of the day.

 

2. Just before the last shut-down of the day the voltmeter should be reading close to the regulated voltage with less than 10 amps flowing.

 

3. If the ammeter is not reading the stated tail current with no electrical things running the engine must be kept running above xxxx rpm until it does.

 

If 1. is not met in all probability there is a fault (faulty alternator or loose belt).

 

If 2 is not met the alternator is probably faulty (although a wiring connection may have gone resistive).

 

If 3 can not be met then there is probably a battery fault developing or the user needs to curb their electricity use.

 

You will probably have to slightly adjust the values to allow for the wiring of the particular boat.

 

 

Edited to add: The important thing for the OP is that the other users always get the batteries as fully charged as possible rather than discharge them too deeply. This assumes the battery bank capacity is more or less matched to "typical" electrical loads. It would not matter too much if one idiot ignored it because the next users would probably get things back and then have a say.

 

A useful thing about this arrangement is that the ammeter can be wired into the alternator output since that is all that needs to be measured. In my particular setup it would need major rewiring of the busbars to enable discharge currents to be measured.

 

Edited to add that in this case you don't need to measure currents in both directions.

 

Nick

[Graham.m]

 

I basic education of roughly what certain items use is not stupid and may help keep within a reasonable SoC (say always above 50%) but its also needs to be very non-technical for most people, and for instance I just cant see you using a vacuum cleaner for two hours to clean boat and which point the assumption is flawed from the off even if well intended.

 

A holiday/share boat is quite different from most liveaboard scenarios and typically the are clocking up the hours moving the boat, the difference between living on an off-grid mooring, and staying for a week on a boat that's doing 6-8hours motoring a day is huge, even with the 'change over day' tendency.

 

Agreed. But I would also augment that with the fact that two 16W florescent lights even for six hours (0.2kWh) uses a lot less power than a 2kW hairdrier/straighteners for half an hour (1kWh) so sitting in the dark to do you hair doesnt help a lot, compared to using a second towel to get it a dry as you can before combing it dry over an hour and a half.

 

Similarly using the microwave for catering and brew reheating will mash power out of the batteries and while a laptops power consumption isnt super huge its a lot more than the lights will be and you can having it on for hours and hours!

 

 

 

 

Daniel

 

I know a lady CCer who takes a couple of hours to vacuum her boat. Every nook and cranny is searched and cleaned from bow to stern. As for hair curler/straightener she initially insisted that she had to have a 3kW inverter just for her hair things. She uses them virtually everyday. As she owns the boat she does what she wants when she wants. In the end she had a 4kW diesel generator, which is started from the bedroom principally so that she could run her fan heater to take the chill off before she got up. lol I lent her the fan heater while she was on shoreline and the boat was being sorted after purchase, it has a new home.

 

I think it is something to do with up bring and attitudes when the are young. But I suspect that any lady who brings a vacuum from home to clean a boat with could be of a similar attitude.

Edited January 23, 2016 by Graham.m

[DHutch]

I don't disagree in principle but I don't believe the info would sink in. However, if they use the hair dryer and see the ammeter suddenly jump to a high number and the SmartGauge start counting down quickly then I think they'll get the idea much faster.

 

Tony

 

Well yes, also that!

 

Ammeter that can cope with a 1800kVA inverter then...

 

 

 

Daniel

I think it is something to do with up bring and attitudes when the are young. But I suspect that any lady [one] who brings a vacuum from home to clean a boat with could be of a similar attitude.

 

Well yes, also that!

 

Ammeter with 10 day data-logging ability and 3g card...

 

 

Daniel

[Tony Brooks]

 

A useful thing about this arrangement is that the ammeter can be wired into the alternator output since that is all that needs to be measured. In my particular setup it would need major rewiring of the busbars to enable discharge currents to be measured.

 

Edited to add that in this case you don't need to measure currents in both directions.

 

Nick

 

 

No but when a couple phones are on charge, a laptop running off 12V, the fridge cuts in and someone starts the microwave oner may have to wait a fair while to get the required tail current. Its much better to wire it (in this case) so it is only measuring the charging current.

 

Also if its an earth return alternator it means the shunt and "ammeter" wires will have to be in the positive which also has some fault and accuracy implications.

[Loafer]

 

 

No but when a couple phones are on charge, a laptop running off 12V, the fridge cuts in and someone starts the microwave oner may have to wait a fair while to get the required tail current. Its much better to wire it (in this case) so it is only measuring the charging current.

 

Also if its an earth return alternator it means the shunt and "ammeter" wires will have to be in the positive which also has some fault and accuracy implications.

 

I have to question that, Tony! The only problem I'm aware of, with shunts in the positive line, is that all 4 connections on the shunt are 'high' compared to their surroundings, so must be insulated from whatever they're attached to.

 

Please administer punishment if I'm wrong!

 

ETA: Thats for independent shunts. I guess some manufacturers REQUIRE that their battery monitor shunts are in the negative line. Not enough research here!

Edited January 23, 2016 by Loafer

[Tony Brooks]

 

I have to question that, Tony! The only problem I'm aware of, with shunts in the positive line, is that all 4 connections on the shunt are 'high' compared to their surroundings, so must be insulated from whatever they're attached to.

 

Please administer punishment if I'm wrong!

 

ETA: Thats for independent shunts. I guess some manufacturers REQUIRE that their battery monitor shunts are in the negative line. Not enough research here!

 

The insulation thing is correct but now think about the two thin wires running from shunt to meter. If one of those or the meter terminals shorts to negative the thin wires WILL melt and probably catch fire. ON the face of it this is easy to prevent by fitting a fuse in each cable close to the shunt BUT:-

 

 

Such ammeter are in reality millivolt meter calibrated as amps and they rely upon the known voltage difference between the two ends of the shunt being proportional to the current flowing through the shunt. Now, I know current in those two cables is very small but the quality of readily available fuse holders and fuse gives me cause fr concern because any slight voltdrop across the fuse must result in inaccurate amp readings.

[sjc]

You can get hall effect current sensors that fit over the cable like a sleeve. Admittedly a pain to fit but you have no problems with safety as they are completely isolated from the high current cables. If I ever get around to it that's what I intend to use, not sure if any commercial ammeters use them though ?

[WotEver]

You can get hall effect current sensors that fit over the cable like a sleeve. Admittedly a pain to fit but you have no problems with safety as they are completely isolated from the high current cables. If I ever get around to it that's what I intend to use, not sure if any commercial ammeters use them though ?

The problem with most Hall Effect sensors is that they're not terribly accurate.

 

Tony

[Arthur Brown]

If the batteries read (smartg.../smartb...) less than 50% then selected items go OFF -inverter, 12v sockets, most lights -leaving just enough to find the bedroom light switches. and the ignition switch.

[sjc]

The problem with most Hall Effect sensors is that they're not terribly accurate.

 

Tony

 

Just looking at a typical supplier, accuracy ( within 5% ) isn't an issue, although cost might be :-

 

http://www.allegromicro.com/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Non-Intrusive-Hall-Effect-Current-Sensing-Techniques-for-Power-Electronics.aspx

[WotEver]

 

Just looking at a typical supplier, accuracy ( within 5% ) isn't an issue, although cost might be :-

 

http://www.allegromicro.com/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Non-Intrusive-Hall-Effect-Current-Sensing-Techniques-for-Power-Electronics.aspx

I guess I should have said "the ones at reasonable cost aren't terribly accurate".

[Graham.m]

I guess I should have said "the ones at reasonable cost aren't terribly accurate".

 

Biggest trouble with a handheld hall effect sensor is keeping it still enough in the right position to get an accurate reading. When mounted solidly in say an engine room the engine's vibrations and changing magnetic field can affect them. But they do have their place in measurement one just has to be aware of limitations.