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Post by Deleted on Aug 22, 2020 21:26:30 GMT
Thanks guys, I'll risk running the fridge a bit more tomorrow and watch the voltage drop. Sounds like I don't have any issues dropping from 15v to 12.7 volts, and that there is actually much more still to give- which is really encouraging. Cheers
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Post by Clinton Cool on Aug 22, 2020 21:50:33 GMT
Very quick tutorial:
12.7 to 12.8v (rested voltage, no load) is fully charged.
12.2 is around 50% you should aim to always keep your batteries above this if possible.
You should fully charge your batteries every couple of days (ideally), or once a week, at least.
Forget any gizmos the only way you can tell if your batteries are fully charged is by reading amps when charging. Amps should be less than 1% of amp hour capacity of the batteries. So, if you have 4 x 110AH batteries you'll know your batteries are fully charged when the amps in (known as the tail current) are 4 amps or so. None of this measurement is accurate is there is any load on the batteries. With experience you can decipher tail current with a load on. For example, if you have a tv on that draws 3 amps and amps in are 7, you can be happy that the batteries are fully charged.
You might have a device that measures amps in, but many boats don't. You'd be amazed how many boaters, even those living aboard, have no clue about battery charging. They regularly wreck expensive sets of batteries and accept it as being normal. It doesn't need to be normal.
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Post by Deleted on Aug 22, 2020 21:59:33 GMT
There is also the £diesel v £battery thing to take into account.
If it costs money to charge the batteries fully using a diesel unit then there will be a point where it is more effective to just kill the batteries and replace them rather than burning oil and wearing out your engine...
If you have a decent solar array then yes for part of the year you can keep it all together but for the other part it's more difficult.
I'm a bit of an advocate of burn less diesel replace batteries more often.
This is assuming the cruising pattern of the boat does not allow full recharging of the batteries on a regular basis. Obviously moving the boat is the priority so if you are also charging while doing that then it's all good.
If however you are stationary and running the main engine then you should be hung drawn and quartered and be tarred and feathered and fed to the lions. And shot at dawn.
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Post by Deleted on Aug 22, 2020 22:07:41 GMT
Very quick tutorial: 12.7 to 12.8v (rested voltage, no load) is fully charged. 12.2 is around 50% you should aim to always keep your batteries above this if possible. You should fully charge your batteries every couple of days (ideally), or once a week, at least. Forget any gizmos the only way you can tell if your batteries are fully charged is by reading amps when charging. Amps should be less than 1% of amp hour capacity of the batteries. So, if you have 4 x 110AH batteries you'll know your batteries are fully charged when the amps in (known as the tail current) are 4 amps or so. None of this measurement is accurate is there is any load on the batteries. With experience you can decipher tail current with a load on. For example, if you have a tv on that draws 3 amps and amps in are 7, you can be happy that the batteries are fully charged. You might have a device that measures amps in, but many boats don't. You'd be amazed how many boaters, even those living aboard, have no clue about battery charging. They regularly wreck expensive sets of batteries and accept it as being normal. It doesn't need to be normal. Cheers Ricco, I didn't realise that roughly a 0.5v drop equated to about 50% of the total charge used up. There are 500 watts of solar and the boat hasnt been used much lately-so its getting lots of tops ups. Maybe that's why the batteries started off showing I think 15v (might have been 14.8v, I was rushing around so didnt pay enough attention). So the apparently big drop to 12.7 was actually them getting quickly to their normal operating parameters, and was not a really genuine drop, in a way.
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Post by Deleted on Aug 22, 2020 22:50:22 GMT
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Post by Clinton Cool on Aug 22, 2020 22:52:24 GMT
Very quick tutorial: 12.7 to 12.8v (rested voltage, no load) is fully charged. 12.2 is around 50% you should aim to always keep your batteries above this if possible. You should fully charge your batteries every couple of days (ideally), or once a week, at least. Forget any gizmos the only way you can tell if your batteries are fully charged is by reading amps when charging. Amps should be less than 1% of amp hour capacity of the batteries. So, if you have 4 x 110AH batteries you'll know your batteries are fully charged when the amps in (known as the tail current) are 4 amps or so. None of this measurement is accurate is there is any load on the batteries. With experience you can decipher tail current with a load on. For example, if you have a tv on that draws 3 amps and amps in are 7, you can be happy that the batteries are fully charged. You might have a device that measures amps in, but many boats don't. You'd be amazed how many boaters, even those living aboard, have no clue about battery charging. They regularly wreck expensive sets of batteries and accept it as being normal. It doesn't need to be normal. Cheers Ricco, I didn't realise that roughly a 0.5v drop equated to about 50% of the total charge used up. There are 500 watts of solar and the boat hasnt been used much lately-so its getting lots of tops ups. Maybe that's why the batteries started off showing I think 15v (might have been 14.8v, I was rushing around so didnt pay enough attention). So the apparently big drop to 12.7 was actually them getting quickly to their normal operating parameters, and was not a really genuine drop, in a way. You're learning very quickly, that's exactly it. Depending on what type of batteries you have your solar charge controller should charge at between 14.4 and 14.8v. It's interesting that they were 15v but probably not worth too much thought at the moment, just treat it as a rounding difference. The point Mr Magnet made about the choice between endless running hours vs. battery longevity is a good one. There is a choice there. I might be a bit opinionated but the best choice, if you can keep your batteries in perfect condition for 8 months of the year with solar, is to make the effort needed to keep them in good condition for the remaining 4. Rather than running an £8K engine to produce a few amps during this period it's far better to run a generator. Yes, storing fuel can be a pain but the running costs are similar and you won't have to sit on a vibrating boat for hours on end. And when the engine wears out it will cost a few hundred to replace rather than £8K.
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Post by Deleted on Aug 22, 2020 22:58:45 GMT
Cheers Ricco, I didn't realise that roughly a 0.5v drop equated to about 50% of the total charge used up. There are 500 watts of solar and the boat hasnt been used much lately-so its getting lots of tops ups. Maybe that's why the batteries started off showing I think 15v (might have been 14.8v, I was rushing around so didnt pay enough attention). So the apparently big drop to 12.7 was actually them getting quickly to their normal operating parameters, and was not a really genuine drop, in a way. It's interesting that they were 15v Was the engine running at the time? I seem to recall there are some choice gadgets already installed.
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Post by Clinton Cool on Aug 22, 2020 23:08:00 GMT
It's interesting that they were 15v Was the engine running at the time? I seem to recall there are some choice gadgets already installed. Does any alternator/ alternator controller charge at 15v? Other than an equalisation burst.
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Post by Deleted on Aug 23, 2020 3:57:41 GMT
Was the engine running at the time? I seem to recall there are some choice gadgets already installed. Does any alternator/ alternator controller charge at 15v? Other than an equalisation burst. With the engine (and thus the alternator) running...'a healthy charging system should give a reading of between 13.8v and 14.4v at regular idle speed...anywhere outside of that range [indicates] under or over-charging - both of which will shorten the battery life...' But I'm sure Tony mentioned the presence of a Sterling battery-to-battery system present. However it could have been the voices. Also, I would guess the reading Tony is quoting is from some type of monitoring equipment linked to his domestic bank and not the starter battery being fed by the alternator.
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Post by naughtyfox on Aug 23, 2020 6:14:08 GMT
All batteries die, its just a question of when. If they are the originals,and that's possible, then its likely they are below par. But seems to me no massive concern in the here and now, probably a job to consider next summer. See how things go this winter. Buy a box of fat candles (thin ones are a waste of space). Tbh Nemesis, it looks like the batteries will run the lights for days- as you would expect I guess. So no need for candles- although of course I will have to get a stock in asap! I dont have a single bloody one... I recommend these: 8 hours. You can put them in the kitchen sink to to warm that area in winter. Remember naked flames and gas get on well together! Keep away from gas leaks! Handy on the back deck in lanterns, or on the roof in lanterns. Robert Dyas (ironmongers) sell them www.robertdyas.co.uk/
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Post by naughtyfox on Aug 23, 2020 6:21:05 GMT
Thanks guys, I'll risk running the fridge a bit more tomorrow and watch the voltage drop. We have a tiny 12v fridge/cool box and don't have that on unless we're driving the boat/engine running. 99% of boaters' battery moans are directly connected to their bloody fridges.
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Post by naughtyfox on Aug 23, 2020 6:25:17 GMT
There is also the £diesel v £battery thing to take into account. If it costs money to charge the batteries fully using a diesel unit then there will be a point where it is more effective to just kill the batteries and replace them rather than burning oil and wearing out your engine... Regular changing of the engine oil will elongate the life of the engine!
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Post by Clinton Cool on Aug 23, 2020 7:25:12 GMT
Thanks guys, I'll risk running the fridge a bit more tomorrow and watch the voltage drop. We have a tiny 12v fridge/cool box and don't have that on unless we're driving the boat/engine running. 99% of boaters' battery moans are directly connected to their bloody fridges. This is true. Fashion dictates that a fridge should be electric nowadays. Fashion dictates that people should prefer to run noisy, expensive engines for hours every day, just for the few amps to run the fridge, when they could spend a fiver a week on gas leading to them, and everyone else in the area, forgetting about the whole matter. Fashion has a lot to answer for.
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Post by Telemachus on Aug 23, 2020 8:33:46 GMT
Does any alternator/ alternator controller charge at 15v? Other than an equalisation burst. With the engine (and thus the alternator) running...'a healthy charging system should give a reading of between 13.8v and 14.4v at regular idle speed...anywhere outside of that range [indicates] under or over-charging - both of which will shorten the battery life...' But I'm sure Tony mentioned the presence of a Sterling battery-to-battery system present. However it could have been the voices. Also, I would guess the reading Tony is quoting is from some type of monitoring equipment linked to his domestic bank and not the starter battery being fed by the alternator. I think that quoted voltage range is out of date. Modern batteries especially sealed ones have lots of calcium in the plate alloy, which raises the gassing voltage and necessary charging voltage. I’d say you want 14.4 to 14.6v to properly charge modern leisure batteries, unless they are fancy AGM or gel, in which case check the manufacturer’s specs.
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Post by Telemachus on Aug 23, 2020 8:40:32 GMT
And just to pick up on earlier points, there is an effect called “surface charge” that temporarily raises the battery voltage during and shortly after charging. So whilst 12.7-12.8 does represent a fully charged battery, this only applies some time after charging is stopped (several hours, or after some moderate discharge). It doesn’t apply during charging so if during charging you see 12.8v and then stop charging, you batteries will be way less than fully charged. You need to charge at at least 14.4v until the charge current drops to around 1 or 2% of capacity.
When you stop charging the voltage will rapidly fall to 13.5 or so, and then over a few hours or a few Ah, down to the 12.7 which represents a fully charged battery. After that the voltage will fall much more slowly towards the 12.2v (no-load voltage) which represents 50% charge.
So in summary the amount of charge taken out of a just-fully-charged battery to get from 14.4v to 12.7v is minimal. Once the battery gets to 12.7v the voltage will decay much more slowly.
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