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Post by tonyb on Oct 29, 2016 8:42:18 GMT
As Tony said Gibbo explains it very well on the Smartgauge site and I think another member worked out an even better way. That was our very own SmileyPete and his solution is also on that page along with a credit. I thought it was but was not sure and did not want to upset anyone by naming the wrong person. Worth pointing out there is far more quality electrical expertise on here now than at the other place it seems.
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Post by Gone on Oct 29, 2016 8:54:05 GMT
Bettina - Not wishing to damage your domestic harmony with "im at the back" but a microwave run for about 5 minutes with your battery bank will use about 2% of your usable capacity. Should you want to run it for longer just do it with the engine running or on shore power when it wont use any. I have one and only use it for porridge in the morning and the occasional ready meal, if it broke I probably wouldn't replace it.
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Post by Albion on Oct 29, 2016 19:56:16 GMT
Tonyqj, in your description of Bulk charge phase you seem to imply that the charger would run flat out (for want of a better description) at whatever it was capable of delivering. However, my Victron gel batteries have a recommended max charging current of 0.2 C (so for a 100Ah battery it should be no more than 20A unless temperature compensated). Would it be worth adding a small caveat to this effect? Roger
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Post by Telemachus on Oct 29, 2016 20:44:55 GMT
I seem to be a bit late to the party!
Regarding the OP, very good (if that doesn't sound patronising!). I'd just take issue with the definition of float charge.
I'd say that float charge isn't really bringing the batteries up to fully charged - they should already be fully charged. Float charge is a maintenance function not a charging function and at a typical voltage which I would say is more like 13.25v for normal wet lead acid, there will be no additional charging. The float charge voltage is a compromise between keeping the batteries fully charged, and not creating too much long term plate corrosion.
Although it may be too complex for the scope of the original article, I'll just say a bit about CEF and peukert. Read or not as you please!
CEF (Charge efficiency factor) is the ratio of amp hours that have to be put back, compared to amp hours taken out. The difference is the amount of amp hours that went to cause gassing of the electrolyte (breaking down the water into hydrogen and oxygen). Note that charge efficiency is not directly related to energy efficiency. This is because energy is amp hours times volts, and when discharging the volts are lower than when charging. So whilst the CEF might be 90%, the power or energy efficiency will be quite a bit less.
CEF is not related to peukert.
Summary: peukert relates to the speed of the chemical reaction in the battery that creates the current.
Peukert is relevant to the way in which a battery's capacity in AH is specified. Typically a battery may be specified at 110AH if when discharged at 11A it is flat after 10 hours. "Flat" or zero state of charge is, for the purpose of the discharge test, defined as a specific end voltage, maybe 10.5v. But if you discharged the battery at 22A instead of 11A, you would get to the end voltage of 10.5v before 5 hours was up. Why? Just because the chemical reaction slows down as most of the chemicals get used up, and it gets harder for the different chemicals to "find" each other in order to react. So perhaps the same battery, when tested at 22A, would only have 95AH by the time it reached 10.5v. So what happened to the rest of the AH. Well, nothing really. They are still there, just a bit sleepy. Give them a rest for a while and then continue to discharge the battery slowly and they can all be recovered.
So peukert is only relevant to AH remaining if you want to discharge a battery at a highish rate until it is flat. If you discharge a battery at a high rate for a short time, and then allow the battery to recover by stopping the discharge or discharging slowly - i.e. typical usage on a boat - the badged AH remains available and peukert is irrelevant.
Not to be confused with internal resistance and consequential power loss. So if you discharge a battery quickly, the internal resistance of the battery causes voltage drop. Peukert means that the voltage internally produced is a bit less. Both these effects cause a lower terminal voltage and hence less power, so overall less energy available from the battery. So if a battery has a certain amount of energy stored in watt hours, if you discharge it rapidly you will recover fewer watt hours and that lost energy is not recoverable even if you let the battery rest.
So peukert is only useful for a "time to run flat at the current rate of discharge" type of display. Since boats tend not to drain batteries at a constant rate, such displays are pretty useless.
However peukert combined with internal resistance means that one can extract more overall energy from a battery by discharging it slowly, than if one discharges it fast.
Bear in mind that AH is a measure of electrical charge and doesn't have a concept of power or energy. Watt hours, being AH times the available voltage, is a measure of energy.
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Post by tonyqj on Oct 29, 2016 20:47:01 GMT
Tonyqj, in your description of Bulk charge phase you seem to imply that the charger would run flat out (for want of a better description) at whatever it was capable of delivering. However, my Victron gel batteries have a recommended max charging current of 0.2 C (so for a 100Ah battery it should be no more than 20A unless temperature compensated). Would it be worth adding a small caveat to this effect? Roger Okay, I'll think about exactly how to word that and put it in. As you state though, in Bulk the charger will indeed run at its maximum current. Thanks for the suggestion.
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Post by bettina on Oct 29, 2016 20:47:04 GMT
Bettina - Not wishing to damage your domestic harmony with "im at the back" but a microwave run for about 5 minutes with your battery bank will use about 2% of your usable capacity. Should you want to run it for longer just do it with the engine running or on shore power when it wont use any. I have one and only use it for porridge in the morning and the occasional ready meal, if it broke I probably wouldn't replace it. LOL no problem with that Chewy I really only want one for reheating leftovers or melting butter or chocolate for baking (save using a pot). I've never used one to "cook" anything in. So the longest it would be on at anyone time would be 4 - 5 minutes.
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Post by tonyqj on Oct 29, 2016 21:28:14 GMT
I seem to be a bit late to the party! Regarding the OP, very good (if that doesn't sound patronising!). I'd just take issue with the definition of float charge. I'd say that float charge isn't really bringing the batteries up to fully charged - they should already be fully charged. Float charge is a maintenance function not a charging function and at a typical voltage which I would say is more like 13.25v for normal wet lead acid, there will be no additional charging. The float charge voltage is a compromise between keeping the batteries fully charged, and not creating too much long term plate corrosion. Ooh, ooh, can we have an argument? π Most chargers that I've looked at switch to float as the battery approaches 100%. Therefore it ain't at 100% yet. 13.6V (or even 13.3V) will very slowly put the last percent or so into the battery, treating it as gently as possible in addition to countering self-discharge. By way of example, most caravans are fitted with a 13.6V power supply which also functions as the battery charger. No stages, just a fixed 13.6V which will fully charge a 12V lead acid battery albeit slowly. Obviously if the battery is very discharged then a low voltage charge like this will do nothing to counter sulphation but it will fully charge the battery.
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Post by tonyqj on Oct 29, 2016 21:33:44 GMT
Tonyqj, in your description of Bulk charge phase you seem to imply that the charger would run flat out (for want of a better description) at whatever it was capable of delivering. However, my Victron gel batteries have a recommended max charging current of 0.2 C (so for a 100Ah battery it should be no more than 20A unless temperature compensated). Would it be worth adding a small caveat to this effect? Roger Done π
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Post by tonyqj on Oct 29, 2016 21:52:03 GMT
Nick said:
Whilst true, it is convenient to describe it as such to newbies. You may have noticed that I did so in an earlier post when I said "You can think of an Ah as a 'unit of power' and a typical leisure battery has 110 of them". To have said the same but using "a measure of electrical charge" would, I believe, be less easy to digest.
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Post by Telemachus on Oct 29, 2016 22:16:18 GMT
I agree to some extent. The only problem with simplifications is that they can come back to bite you later on. Whilst we can all presume that everyone has 12v boats, in fact some have 24v - at which point a 110AH battery takes a very different meaning.
Anyway, just offering that up for the thread, not suggesting you at it to the OP.
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Post by tonyqj on Oct 29, 2016 22:18:42 GMT
I agree to some extent. The only problem with simplifications is that they can come back to bite you later on. Whilst we can all presume that everyone has 12v boats, in fact some have 24v - at which point a 110AH battery takes a very different meaning. Not really - it still has 110 of them, they're just bigger. π
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Post by Telemachus on Oct 29, 2016 22:31:40 GMT
I seem to be a bit late to the party! Regarding the OP, very good (if that doesn't sound patronising!). I'd just take issue with the definition of float charge. I'd say that float charge isn't really bringing the batteries up to fully charged - they should already be fully charged. Float charge is a maintenance function not a charging function and at a typical voltage which I would say is more like 13.25v for normal wet lead acid, there will be no additional charging. The float charge voltage is a compromise between keeping the batteries fully charged, and not creating too much long term plate corrosion. Ooh, ooh, can we have an argument? π Most chargers that I've looked at switch to float as the battery approaches 100%. Therefore it ain't at 100% yet. 13.6V (or even 13.3V) will very slowly put the last percent or so into the battery, treating it as gently as possible in addition to countering self-discharge. By way of example, most caravans are fitted with a 13.6V power supply which also functions as the battery charger. No stages, just a fixed 13.6V which will fully charge a 12V lead acid battery albeit slowly. Obviously if the battery is very discharged then a low voltage charge like this will do nothing to counter sulphation but it will fully charge the battery. I'd agree that plenty of chargers switch to float as the battery approaches 100% but that is often a bad thing as they switch far too early. I see no reason not to switch to float after the battery is nominally fully charged. My MV Combi has 13.25v as the default float voltage and I thought it a bit low, so I asked Gibbo (years ago) and he said that 13.25 was about right, as if it is higher it just shortens battery life when left on 24/7. When it switches to float the current falls to zero. When I come back to the boat after a few weeks on shore power float, if I put the charger back to bulk / absorption it takes quite a few amps for a while before settling down at 0.25% or so, so clearly float wasn't keeping it at 100%, but only close to 100%. Yes 13.6v will charge the battery, but it is too high for long term float of a wet lead acid battery. Caravan chargers are a simplistic compromise. Finally just to mention that float charge is not just about keeping the batteries charged in the presence of self-discharge, but also running the boat's services when connected to shore power long term.
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Post by smileypete on Oct 30, 2016 1:43:18 GMT
Here's a copy of what I recently posted on batt charging if someone want's some simple charging/monitoring tips: 1) Batteries in frequent use need a FULL charge at least weekly - other charging can be near full as practicable. 2) SO, what is a FULL charge, then? To paraphrase 'The Battery FAQ' (link): a) Charge voltage has reached the correct level as required by the manufacturer or specialist supplier. b ) Charge current has tailed off to a steady low level, usually less than 1 to 2% of batt capacity in Ah - may take 6 to 8 hours! c) If a non sealed battery, it helps if the battery acid is fizzing gently at the end - a quick peek once in a blue moon will do. 3) Recharge when the batt voltage no longer recovers above 12.2V, or say 12.1V if running a few LED lights or 12V fridge. If the inverter starts beeping it's definitely time to recharge! 4) IMPORTANT: Safe handling precautions for batteries can be found at 'The Battery FAQ' via the link given above. That's about it really...
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Post by Gibbo on Oct 30, 2016 14:09:37 GMT
I agree with Tony's work but would like to add in the hope of saving potential confusion if anyone charging from their alternator is waiting for the voltage to drop to float. In the vast majority of cases the standard alternator regulator does not have a float phase. It just maintain the same voltage as it did when in the bsorbtion stage. External regulators and a very few on alternator regulators will have a float stage. Spot on. A typical alternator is really just a two stage charger. Bulk and absorption/acceptance (depends who you believe for the correct word).
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Post by Gibbo on Oct 30, 2016 14:10:27 GMT
Charge Efficiency/Peukert/Black Magic is all the same thing as far as this guide's concerned. Yeah but Peukert is all but irrelevant for the typical narrowboat owner. There was fundamental misunderstanding of it on CWDF in hindsight, which seemed to be reflected in what you wrote, Nick can fill you in on the details. Bullshit!
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