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Solar vs Generator


Nick D

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1 hour ago, leeco said:

Yeah but what is it a new type of battery?

looks like a standard leisure battery but 10 times the price, a little more functional, and one third the weight.

 

pays yer munny and takes yer choice, basically.

 

 

................................   I wish I could afford 4 of them on my little 'lectric yogurt pot.

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10 hours ago, Tony Brooks said:

The Smarguage is a sort of battery fuel gauge BUT it will reliably tell you when you should stop using electricity and start charging ASAP but is not so good at telling you when to stop charging so in addition you need an ammeter. However to maximise battery life you need to recharge as close to fully each day. Solar is excellent at that in summer as others have described.

 

there are also battery monitors made by at least two companies that give you volts and amps but regrettably more. Regrettably because the percentage charged or time to go before charging all too often turns out to be a lie and as the months go on the lies get larger and larger. If you promises to ignore those problem readings ans stick to amps and volts then one of these like a BVM is all you need BUT you will have to  do a bit of learning so you can infer state of charge from battery voltage but that's for another day. That then brings us back to the non-technical statement, to properly monitor your batteries and deal with electrics in general you need to develop technical skills. A Smartguage for "stop discharging" and an ammeter for "stop charging" is about as non-technical as you can get. I would suggest that you fit and learn to use battery monitoring equipment before anything else.

 

There is a whole new set of problems related to both battery chargers and solar controllers dropping down to what is known as float voltage too soon but if you leave the batteries on shore line charging for weeks then that problem is unlikely to be a major one.

I'm curious about this, back in the day when I still had a car I don't suppose that the battery ever reached full charge (well perhaps on a very occasional motorway run) since most of the use was around town, on the car the battery lasted over 7 years (still fired the engine up to start as I sent it to the scrapyard).

 

Soon after I got the boat, due to the previous owner having allowed the domestic batteries to go completely flat, I had to replace the whole bank. The replacement batteries have just celebrated their fifth birthday (quiet affair, just a few friends around:cheers:) and still seem to be performing well (tempting fate again) with rarely more than 4 hours cruising per day. I don't get into the technicalities of how these things work but I do note that when the alternator charge to the batteries drops to 8amps or less after a given amount of time the Battery monitor flips to 100% SOC which may or may not be wrong, but I really don't care. The batteries still work and I was expecting to have to change them some time after the 5 year mark so every extra year is a bonus. 

 

On a different tangent, a question that has always puzzled me is that if, for example, I go into a marina for a few days on shore power which will put the battery charge back up to a full and genuine 100% SOC what happens to the power being generated by the domestic alternator (or solar if I had it as well) as I then cruise off into the sunset if it isn't going into the battery? I've seen the ammeter part of the battery monitor go down quite low but have never seen it as zero so it appears to be trying to put charge into what would effectively a fully charged battery. I know that is what the regulators are for but do they have a facility to shut the charge off altogether when the battery is full?

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On 02/08/2018 at 20:06, Nick D said:

When we're on the cut we tend to cruise for about 4 hours a day. This doesn't give us enough charge for our needs so we run the engine for another three hours on average.

Removed as I just realised this thread is 4 pages long and I answered before the bottom of the first. See I am learning, but not fast enough :giggles:

Edited by ditchcrawler
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48 minutes ago, Wanderer Vagabond said:

I'm curious about this, back in the day when I still had a car I don't suppose that the battery ever reached full charge (well perhaps on a very occasional motorway run) since most of the use was around town, on the car the battery lasted over 7 years (still fired the engine up to start as I sent it to the scrapyard).

 

Soon after I got the boat, due to the previous owner having allowed the domestic batteries to go completely flat, I had to replace the whole bank. The replacement batteries have just celebrated their fifth birthday (quiet affair, just a few friends around:cheers:) and still seem to be performing well (tempting fate again) with rarely more than 4 hours cruising per day. I don't get into the technicalities of how these things work but I do note that when the alternator charge to the batteries drops to 8amps or less after a given amount of time the Battery monitor flips to 100% SOC which may or may not be wrong, but I really don't care. The batteries still work and I was expecting to have to change them some time after the 5 year mark so every extra year is a bonus. 

 

On a different tangent, a question that has always puzzled me is that if, for example, I go into a marina for a few days on shore power which will put the battery charge back up to a full and genuine 100% SOC what happens to the power being generated by the domestic alternator (or solar if I had it as well) as I then cruise off into the sunset if it isn't going into the battery? I've seen the ammeter part of the battery monitor go down quite low but have never seen it as zero so it appears to be trying to put charge into what would effectively a fully charged battery. I know that is what the regulators are for but do they have a facility to shut the charge off altogether when the battery is full?

The Charge Current will shut down to Zilch when presented with 100% Charged Batteries.

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Some good info here.

 

IF the objective is reliable long term power via lead acid batts, then the boater needs to learn how to effectively charge and effectively monitor said batteries.

 

Otherwise it's in the lap of the gods, who may not be so magnanimous. Though plentiful solar can delay their wrath, at least in summertime...

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8 hours ago, Wanderer Vagabond said:

I'm curious about this, back in the day when I still had a car I don't suppose that the battery ever reached full charge (well perhaps on a very occasional motorway run) since most of the use was around town, on the car the battery lasted over 7 years (still fired the engine up to start as I sent it to the scrapyard).

 

Soon after I got the boat, due to the previous owner having allowed the domestic batteries to go completely flat, I had to replace the whole bank. The replacement batteries have just celebrated their fifth birthday (quiet affair, just a few friends around:cheers:) and still seem to be performing well (tempting fate again) with rarely more than 4 hours cruising per day. I don't get into the technicalities of how these things work but I do note that when the alternator charge to the batteries drops to 8amps or less after a given amount of time the Battery monitor flips to 100% SOC which may or may not be wrong, but I really don't care. The batteries still work and I was expecting to have to change them some time after the 5 year mark so every extra year is a bonus. 

 

On a different tangent, a question that has always puzzled me is that if, for example, I go into a marina for a few days on shore power which will put the battery charge back up to a full and genuine 100% SOC what happens to the power being generated by the domestic alternator (or solar if I had it as well) as I then cruise off into the sunset if it isn't going into the battery? I've seen the ammeter part of the battery monitor go down quite low but have never seen it as zero so it appears to be trying to put charge into what would effectively a fully charged battery. I know that is what the regulators are for but do they have a facility to shut the charge off altogether when the battery is full?

Not sure it that’s a question or observation.

 

The duty of a domestic battery and start battery are very different although on  modern long distance truck they tend to merge.

 

In a car for most of the time the vehicle's electrical load is supplied by the alternator with the battery only supplying it on the odd occasion so the battery only has to deal with starting. That is provide well over 100 amps for an incredibly short space of time (unless the engine is worn out). When you work it out you only discharge a engine battery by a very few Ah per start so it is quickly recharged. About half an hour after each start the engine battery will be well on its way to fully charged. The speed of recharging ensures the battery suffers minimal sulphation and  the very small discharge ensures you do not lose much cyclic life.

 

The domestic batteries on the other hand are required to sustain a far lower rate of discharge (unless a hefty inverter is involved) but for much longer periods so the Ah removed is far higher (remember 30Ah to 50Ah per day for an electric fridge). Then many people sit in a nice mooring for a couple of days  without charging the batteries. This results in a battery that has a lot more opportunity to sulphate and the deeper discharge uses up more cyclic life so domestic batteries tend to have a shorter useful life than start batteries.

 

On the point about what happens to power being generated by the alternator or solar when the batteries are fully charged. First of all it is exceptionally difficult to fully charge a battery that is fitted to a boat of vehicle but they also suffer a degree of self discharge so those two things together allow a very small charge to flow with nominally fully charged batteries. All the PWM & MPPT solar controllers I have seen drop to a float voltage when they think the batteries are fully charged so that is a lower voltage than "normal" so it is far less likely to damage the batteries by overcharging them. The solar controllers, in effect, chop the current from the panels up so keep on open circuiting them so the on load and off load periods are adjusted to  provide a safe voltage at the current the batteries demand. this means for much of the time with fully charged batteries the panels are generating current.

 

The alternator is different in that the voltage it produces is controlled by messing with magnetic field strength inside it but its regulated voltage is chosen as the best compromising between fast recharging and minimising battery damage by excess voltage or over charging. If you left a modern 14.5V regulated alternator charging 24/7 for several weeks it may well damage the battery but we do not do that. A few regulators and all the expensive alternator controllers in one way or another cause the voltage to drop when they think the batteries are fully charged. Either by handing control back to the alternator's regulator, which as I explained could in exceptional circumstances cause overcharging, or by taking full control and dropping it to a float voltage.

 

If you have a reasonable amount of solar plus fully charged batteries it is not unknown for the charge warning lamp to flicker/glow and the warning sounder to quietly cheep to itself very soon after starting. This is because the alternator's voltage regulator sees the solar voltage, thinks it is too high, and shuts the alternation down. As soon a sit shuts down the voltage tends to drop so it starts charging again. Putting an electrical load on usually sorts it. So an alternator would not be producing any current if the apparent battery voltage was high enough. The regulator would simply shut it down by not providing the current for the internal magnetic field to build up.

 

 

 

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OP.

My opinion on this:

If you're not particularly technically minded and don't want to babysit the batteries to get the absolute max life out of them, spend £100 on a SmartGauge, available from Merlin.

It gives you the percentage charge of the battery bank, to an accuracy that perfectly acceptable to the average user.

Dead simple, press a button, shows you the charge. If it's below 60% panic. If it's above 80% put your feet-up.

 

As for energy generation, because you have shoreline on occasion and you don't live off grid, I would invest in a genny or solar.

 

My question for you would be what is your energy use?

Needing more than 4 hours daily suggests quite a bit of usage to me, perhaps the easiest thing will be to just drop your usage with some appliance / habit changes

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11 minutes ago, sirweste said:

I did try to keep it as general as possible! With caveats in about it being accurate enough to the average user!

 

 

Doesn’t maje what you said right, or even close. Recipe for a wrecked set of batteries more like...

 

Now where did I put my popcorn..? 

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58 minutes ago, Mike the Boilerman said:

 

Doesn’t maje what you said right, or even close. Recipe for a wrecked set of batteries more like...

 

Now where did I put my popcorn..? 

It's not even close to right?? I know you and other had issues with faulty SmrtGs, but assuming that is a fully functioning one then if it shows you anything around 60% then you should be panicking. 

If the value is above 80% then you're alright generally.

With the OP cruising regularly then his batts are likely to see full charge regularly.

 

Unless I'm miss-informed on this I think my general statement was generally right, as far as general goes?

 

 

 

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15 minutes ago, sirweste said:

It's not even close to right?? I know you and other had issues with faulty SmrtGs, but assuming that is a fully functioning one then if it shows you anything around 60% then you should be panicking. 

If the value is above 80% then you're alright generally.

With the OP cruising regularly then his batts are likely to see full charge regularly.

 

Unless I'm miss-informed on this I think my general statement was generally right, as far as general goes?

 

 

 

 

Nope. It’s 50% wrong and as I said, a recipe for wrecked batteries. Nothing to do with I correct calibration of smartgauge. 

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1. So I'm sat at home tonight watching Netflix and me batteries are at 80% or so, I go to bed, wake up have a shower and then recharge them through the day, to the claimed 100% +/- 10%

2. If I'm watching TV and I'm told that me batteries are at 60%, I panic, switch everything off, get on charge in the morning ASAP.

 

I really don't understand how I've got this wrong. How are you supposed to use batteries if not as per 1. !!!??!?

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13 minutes ago, sirweste said:

1. So I'm sat at home tonight watching Netflix and me batteries are at 80% or so, I go to bed, wake up have a shower and then recharge them through the day, to the claimed 100% +/- 10%

 

Not quite as wrong ...but still wrong. Lead acids must be charged to 100% frequently to avoid sulphation, which reduces capacity and kills them. When I say 100%, I dont mean 95%, 96% etc. I mean 100%. The smartgauge can not reliably tell you when it is 100%. If you rely on it, it can wreck you batteries if you only go to say 95%. Your 100% +/- 10% is just not good enough. This has been discussed again and again and again and again....on this forum. You need to monitor tail current to know when you get to 100%.

There is an issue on what does 'frequently' mean. I chose to interpret that as every couple of days and try to get to 100% every day. Others will say weekly. My batteries are lasting well.

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13 minutes ago, sirweste said:

1. So I'm sat at home tonight watching Netflix and me batteries are at 80% or so, I go to bed, wake up have a shower and then recharge them through the day, to the claimed 100% +/- 10%

2. If I'm watching TV and I'm told that me batteries are at 60%, I panic, switch everything off, get on charge in the morning ASAP.

 

I really don't understand how I've got this wrong. How are you supposed to use batteries if not as per 1. !!!??!?

I have to say I tend to be with you on this, I find it really difficult to get excited about tail current,charging rate,blah,blah,blah of my batteries. They are a black box as far as I'm concerned which, when faulty, gets replaced. I cruise during the day, the (false) SOC reading is 100%, the following morning it is 88% so I go for another cruise, it then reads 100% again. I really don't care whether that figure is accurate to within 50%, 30%, 10% or 0.005%, my batteries have just celebrated their 5th birthday on this inept method that I use, so if they expire tomorrow I'll still have got a good return on them. This idea that I have to fully charge the batteries to within an inch of their lives seems pointless to me since they will only be 100% until the second that the fridge kicks in when they will no longer be 100%:unsure:

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Yes, I'm happy with my comment then.

As per my post to the OP, if he's not too concerned about babysitting his batteries to get the absolute max life out of them, then what I suggested should be about fine.

My T-105 bank is now above 3 years young and I think I hit 100% (depending on solar) on average 5 or 6 times a month, how delightfully uselessly anecdotal!!! 

 

With the OP returning to base every 3 weeks or so his batteries will be then tippy topped up. 

 

So as my original post, if the OP is not too worried about squeezing the absolute max life out of the batts and just want's to get an acceptable return for a reasonable amount of effort, then a SmrtG and not faffing about with tail currents and the like is the answer.

If the OP does want to know about the techy details and get the max life, then you're right - but from reading the thread that wasn't the impression I got.

Edited by sirweste
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3 hours ago, sirweste said:

Yes, I'm happy with my comment then.

As per my post to the OP, if he's not too concerned about babysitting his batteries to get the absolute max life out of them, then what I suggested should be about fine.

My T-105 bank is now above 3 years young and I think I hit 100% (depending on solar) on average 5 or 6 times a month, how delightfully uselessly anecdotal!!! 

 

With the OP returning to base every 3 weeks or so his batteries will be then tippy topped up. 

 

So as my original post, if the OP is not too worried about squeezing the absolute max life out of the batts and just want's to get an acceptable return for a reasonable amount of effort, then a SmrtG and not faffing about with tail currents and the like is the answer.

If the OP does want to know about the techy details and get the max life, then you're right - but from reading the thread that wasn't the impression I got.

Thank you Sirweste, you have summarised my requirements exactly. I'm not the sort that wants to worry about tail currents and constantly checking amps and volts etc. although I do appreciate that some people are more fastidious than me and I thank all those that have contributed to this thread and I have learnt a lot, in particular what I can do to manage the batteries better if I choose to do so.  I also appreciate that my slightly more relaxed attitude than others in this area might mean that my batteries have a shorter life, but it's a price I'm willing to pay.  Prior to this latest exchange today and based on the previous advice in this thread, I had already decided to buy a Smartguage meter and will see how this goes.  

 

The most important thing I have learnt from this thread is the fact that the bulk charging takes place early on and that batteries take much longer to complete the top up. I have probably been running my engine for unnecessarily long periods as a result.  This was the original reason for my question about solar vs generator. It may well be that I need neither, but once I have tried the Smartgauge for the next few cruises I should have some idea and if I do, will definitely choose solar over the generator.  Having not been on a shore line before, I think this will make a difference by ensuring that the batteries get topped up fully at least least every three weeks and I will aim to give them a full charge once a week whilst cruising (yes I know I can't be sure they are fully charged with a Smartguage but I will just have to use my judgement!)

 

Thank you once again for your help. I seem to have generated (excuse the pun) a lot of debate.

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