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Just now, Mike the Boilerman said:

CBA. You know perfectly well there have been plenty of posts advising recharging at 50% over the years.

Fair enough. 

 

I CBA either, but have always understood the perceived wisdom is to not discharge batteries below 50% for max lifespan,which clearly isn't the same as waiting until they have reached 50% capacity before charging. 

Guess you don't want the tenner for you two SG? 

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1 hour ago, Mike the Boilerman said:

So where did I get this idea from, if not from advice on the board?

The answer is nowhere. I read it repeatedly on this board, over a period of about two years.

So have I... repeatedly. It was my received wisdom until I discovered, like Mike, that it is one way of destroying cheap, and expensive, batteries.

1 hour ago, rusty69 said:

Examples? 

CBA here as well :)

If I come across any in passing, I'll bump them to the top of a thread.

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1 hour ago, rusty69 said:

Fair enough. 

 

I CBA either, but have always understood the perceived wisdom is to not discharge batteries below 50% for max lifespan,which clearly isn't the same as waiting until they have reached 50% capacity before charging. 

Guess you don't want the tenner for you two SG? 

I always read it as a good compromise between battery life, and diesel or petrol costs, if off grid.

I've recently started to charge daily for a couple of hours, then for as long as I can on a Saturday or a Sunday, (4hrs+). Seems to be keeping the batteries at their fallen capacity, rather than getting worse.

I'm planning to get an extra 450W of solar and a reasonable MPPT controller, to see if I cant make charging a bit more continuous on a daily basis.

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The 50% idea (personally I use 60%, 12.2 resting volts) is a limit, not a target. My own usage pattern rarely takes me anywhere close to that limit as I tend to be on my way well before its reached, but seeing it approaching is a reasonable guide (for me) as to when I need to get frugal on electricity use - generally, again for me, that means the inverter stays off until I move or run the engine for a bit. The greater the distance you drop, the more stuffing you knock out.

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3 minutes ago, Sea Dog said:

The 50% idea (personally I use 60%, 12.2 resting volts) is a limit, not a target. My own usage pattern rarely takes me anywhere close to that limit as I tend to be on my way well before its reached, but seeing it approaching is a reasonable guide (for me) as to when I need to get frugal on electricity use - generally, again for me, that means the inverter stays off until I move or run the engine for a bit. The greater the distance you drop, the more stuffing you knock out.

Well no, it is neither a limit nor a target, it's just a ballpark rule of thumb SoC below which it's best not to go too often. That said, according to Trojan's figures, you can get the best life in terms of the maximum overall AH extracted over the life of the battery, by going to 40% SoC on every discharge.

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In the main batteries fail from one of two causes. Internal short circuits or excess sulphation. They are cause in two different ways.

Sulphation is the conversion of a lead oxide to lead sulphate and is an intrinsic part of how lead acid batteries work. The moment you discharge lead acid batteries by any amount you produce lead sulpahte but the problem is the longer the lead sulphate sits there waiting for charging to reconvert it to lead oxide the more and more it changes its properties so it becomes more and more difficult to reconvert to lead oxide by charging requiring higher and higher charging voltages to do it. Eventually the voltage required is  in excess the voltage that would in one way or another damage the batteries in other ways so normal charging leaves the old  sulpahte in place thus reducing the batteries capacity. This has nothing to do with the so called 50% rule and that "rule" addresses failure caused by short circuits.

Now think about the above. In an extreme case someone who is blindly following the 50% rule without much understanding may leave their in late October with 75% charged batteries thinking they will be OK but all winter the 25% of lead sulphate will be changing its composition making it harder and harder to reconvert so come the spring the batteries will have lost 25% of their capacity. The same will apply if the batters were left for days or weeks in that state, its just that the sulphate would be easier to reconvert so the damage would be less. I think this is what has ruined Mike's batteries.

Internal shorts are caused by either the build up of plate materiel in the base of the battery or contact between positive and negative plates when a separator becomes damaged. The rate at which this happens is related to charging voltages and the internal battery construction with more expensive batteries having features that enhance the plate separation and also tend to keep the plate materiel on the plates. It is these features and others that allow the manufactures to give different cyclic lives to different battery designs and it is this that the 50% "rule" seeks to address by reducing the depth of discharge so you get more "partial cycles" and thus less internal damage/wear from a given battery design.

I fear the discussion in this topic has been caused by people  misunderstanding the 50% "rule" and not grasping that it says "try not to discharge below 50% for optimum battery life but recharge ASAP to minimise sulphation.

 

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6 minutes ago, nicknorman said:

That said, according to Trojan's figures, you can get the best life in terms of the maximum overall AH extracted over the life of the battery, by going to 40% SoC on every discharge.

Perhaps that is where the confusion lies. 

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9 hours ago, Mike the Boilerman said:

CBA. You know perfectly well there have been plenty of posts advising recharging at 50% over the years.

Rubbish!

50% is generally accepted as being the very lowest you should take your batteries down to regularly if you want any extended life from them as a balance between life and usability but if you can avoid going that low then that will be much better. 

18 minutes ago, Sea Dog said:

The 50% idea (personally I use 60%, 12.2 resting volts) is a limit, not a target.

Absolutely. 

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2 minutes ago, nicknorman said:

Well no, it is neither a limit nor a target, it's just a ballpark rule of thumb SoC below which it's best not to go too often. That said, according to Trojan's figures, you can get the best life in terms of the maximum overall AH extracted over the life of the battery, by going to 40% SoC on every discharge.

Ok, point taken, but my post contained terms like 'personally', 'for me', etc, and was not targeted at those with far greater knowledge than most and who are perfectly able to choose their pattern for themselves - e.g. the OP, who has already expressed confusion.  

For some, 0% is the limit, but I think we'd agree that one can do rather better by drawing one's own red line somewhere above that, depending on what batteries one has. My red line remains at 60% for my Sealed Lead Acid batteries, but straying beyond that occasionally would not be the end of the world,  just more taxing than my normal regime.

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12 hours ago, bizzard said:

It meant that their Klug-gauge is reading all wrong and so they had to, first, gorge themselves on carrots to see better before surfacing at night to recharge the battery. Sometimes they did it with an exhaust snorkel.

Ive done that.

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33 minutes ago, nicknorman said:

That said, according to Trojan's figures, you can get the best life in terms of the maximum overall AH extracted over the life of the battery, by going to 40% SoC on every discharge.

But again, this is misunderstood. If someone takes for example 10% out in a day then they might think that they can go six days before they get down to 40% SoC and need to recharge. This is in direct contradiction to Trojan's advice to "recharge immediately following a discharge". 

So if you have Trojans and your bank is sized such that you'll use between 50% and 60% of the charge in a day, and if you can fully recharge them prior to the next discharge then yes, they'll have a long life. I suspect that there are insufficient hours in a day to achieve this. 

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39 minutes ago, nicknorman said:

it is neither a limit nor a target, it's just a ballpark rule of thumb SoC below which it's best not to go too often.

Semantics. The battery won't suddenly die if you go to 49%, so nobody is saying it's a 'hard limit'. We use 50% as a guide because it's a reasonable balance between usability and battery life. 

As you say above, it's best not to go below it too often but no-one is suggesting that you should go down that far regularly if it can be avoided. 

38 minutes ago, Tony Brooks said:

I fear the discussion in this topic has been caused by people  misunderstanding the 50% "rule" and not grasping that it says "try not to discharge below 50% for optimum battery life but recharge ASAP to minimise sulphation.

Agreed. 

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Most importantly, the bit that is often missed is "and recharge fully" when charging. Mike has often complained that he doesn't have the time to do this and I'm pretty sure that THAT is why his batteries suffer, far more than how far he discharges them. 

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Just now, WotEver said:

Most importantly, the bit that is often missed is "and recharge fully" when charging. Mike has often complained that he doesn't have the time to do this and I'm pretty sure that THAT is why his batteries suffer, far more than how far he discharges them. 

You forgot to mention his dodgy Smartgauge(s) 

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7 minutes ago, WotEver said:

But again, this is misunderstood. If someone takes for example 10% out in a day then they might think that they can go six days before they get down to 40% SoC and need to recharge. This is in direct contradiction to Trojan's advice to "recharge immediately following a discharge". 

So if you have Trojans and your bank is sized such that you'll use between 50% and 60% of the charge in a day, and if you can fully recharge them prior to the next discharge then yes, they'll have a long life. I suspect that there are insufficient hours in a day to achieve this. 

Yes this has been amply demonstrated by Mike, although prior to that I'm not sure we realised just how bad it was to repeatedly use a battery for several days without recharging. For your last para it depends on usage obviously, but in winter with the long evenings of satellite tv (the recording box takes a fair bit of juice), we like to have the boat well-lit (albeit with LEDs), electric blanket on overnight, kettle, toaster, coffee machine in the morning, we can get into the 50s before I start the engine, so we wouldn't have to try too hard to get to the 40s%. But certainly one could use 60% of capacity over 2 days and perhaps, with subsequent good charging, that won't lead to sulphation.

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Reading these last few comments I`m minded to the analogy of us as humans. We need a regular intake of food to give us energy. As we get older our mental attitude to applying effort and maintaining a fitness level tends to wain- well in my case. The result is muscle deterioration and even then with a renewed effort to get fit you never achieve that wonderful ability of early youth which is you can run all day and not understand exhaustion. Is ther not a "buzzer" that can just sound when your leisure batteries get to 12volts so its time to get going or at least put them on charge?

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4 minutes ago, nicknorman said:

Yes this has been amply demonstrated by Mike, although prior to that I'm not sure we realised just how bad it was to repeatedly use a battery for several days without recharging. For your last para it depends on usage obviously, but in winter with the long evenings of satellite tv (the recording box takes a fair bit of juice), we like to have the boat well-lit (albeit with LEDs), electric blanket on overnight, kettle, toaster, coffee machine in the morning, we can get into the 50s before I start the engine, so we wouldn't have to try too hard to get to the 40s%. But certainly one could use 60% of capacity over 2 days and perhaps, with subsequent good charging, that won't lead to sulphation.

Lets also not forget that although some people seem to live life for a set of " Trojans " :rolleyes: the said Trojans will last no longer whatsoever than cheapies unless mollycoddled.

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8 minutes ago, jddevel said:

Is ther not a "buzzer" that can just sound when your leisure batteries get to 12volts so its time to get going or at least put them on charge?

Yes, it's called a SmartGauge ;)

The rules are actually extremely simple. 

  • Charge daily if they're being discharged daily. 
  • Fully charge to close to 100% every time. 
  • Do not drop below 50% when discharging if you can avoid it. 

Tony

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8 minutes ago, jddevel said:

Is ther not a "buzzer" that can just sound when your leisure batteries get to 12volts so its time to get going or at least put them on charge?

Iirc, the Victron BM will do that. You can set a alarm levels, although I haven't because sods law says that the alarm point occurs when you're deep asleep and you won't be thanked for running your engine at 3am so there's not much to be done about it. Far better to become battery aware and keep an eye on your gauge(s). You'll soon learn what sort of consumption keeps you within limits and what threatens your batteries, so overly-frequent checking isn't normally required unless you're doing something more than normal.  I always look first thing in a morning at what I took out last night - I'm rarely below 12.4 volts.

Your Victron inverter will trip on low volts if that occurs when its in use, but that might well be much too low to stay above your red line voltage and I don't know if that's adjustable on the Victron. If you can (unless you have a 240V fridge, say), switch off your inverter when not required so as to prevent it's idle current being an unnecessary drain. That 240v 1 watt led table lamp uses rather more once those inverter losses are factored in!

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2 minutes ago, Sea Dog said:

I always look first thing in a morning at what I took out last night - I'm rarely below 12.4 volts.

I am sad enough to be able to see my Smartgauge from bed. 

Gauge mounting location is important. The more accessible it is, the more likely you will look at it. 

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32 minutes ago, mrsmelly said:

Lets also not forget that although some people seem to live life for a set of " Trojans " :rolleyes: the said Trojans will last no longer whatsoever than cheapies unless mollycoddled.

Our Trojans require no mollycoddling except for watering a couple of times a year. But then we do use our boat as boats are intended to be used - for daily cruising, not as a cheap substitute for a house. <taking cover> So they rarely get less than 8 hrs charging a day, and of course on shore power when we are in the house. So far they have been vastly better than the cheapies we had previously.

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Seadog. Have a 240v fridge and was considering as suggested in another topic a small second inverter just for the fridge but it was pointed out that this second inverter due to its "quality" may use as much "resting" power as my Victron anyway

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I have seen many mentions over the years of how the SmartGauge was originally designed by Gibbo as a simple and easy to use 'fuel gauge' for his wife. She was only told to keep the SmartGauge above 50%. I don't remember any corollary for her to recharge after every discharge ever being mentioned.

My batteries went wrong because I interpreted this literally and sized my batteries so it would take a week to run them down to 50%, at which point I would recharge them. Unfortunately I relied on the SmartGauge to tell me when they reached 100%, which as we all now know, is wrong.

In addition, I failed to 'recharge after every discharge' because the boat (and the battery bank) is in continuous use as a liveaboard, so the term is rather meaningless unless it means I need to start the genny every time the fridge motor shuts off. And somehow I think the Trojan advice DOES mean this. So now there are two things I'm doing wrong. 

Consequently my batteries rapidly sulphated from day one from I suspect, a combination of these two things, neither of which I realised. 

Given the emerging importance of recharging after every discharge, it seems the primary use for a SmartGauge of telling the user when they must recharge is extremely limited. In fact the only use for a SmartGauge seems to be to tell the user whether or not the batteries are heavily or lightly discharged, and whatever the state of discharge, NOW is the time to recharge!  

 

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