|
Post by Telemachus on Mar 7, 2021 19:40:11 GMT
Yes I understand what you are talking about, which is why I like these battery chargers you see the amps and the voltage. I’ve 1040 amp/hrs but unfortunately only have 60amps of battery charging available at the min. When it’s all set up I plan to get another 120amp battery charger. But not yet, probably after I upgrade the solar. Ok so 60A into 1040A is C/17, quite slow. I’d think you were at 95% by the time you get to 13.8. Just a guess!
|
|
|
Post by Telemachus on Mar 7, 2021 20:05:24 GMT
I think you need to rethink the concept of relating charge voltage to SoC. If you apply 13.8v to your batteries, they will reach 100% SoC after a while, albeit somewhat slower than if you charged at 14.4v etc. So it is less about what voltage you charge to, more about what current you stop charging at. If you apply 13.8v at a high current, and stop as soon as the voltage reaches that, you will have a much lower SoC than if you apply 13.8v at a low current and stop charging as soon as 13.8v is reached. I can’t remember how much capacity you have but say it’s 400Ah and you are charging at 60A, that is relatively slow and once the battery voltage gets to 13.8v I suspect the SoC will be over 90%. But you will get a better idea of that than me, I am only theorising and relating to my experiences of charging 200Ah at 5A. I found (charging slowly) that once the voltage got to 13.6v there was virtually nothing left, ie SoC at 99%. Very shortly afterwards the voltage would be off up the knee because the batteries couldn’t take any more charge. Can I ask your opinion on this issue Nick: On most days in the Winter months I wont be cruising (maybe 2 cruising days out of 5), and so on most days I will want to charge to 85% SoC as quickly as my limited setup allows. I am hoping to use the minimum amount of diesel that will deliver an acceptable charge (say 100Ah for a day). I'll normally be charging every day, but sometimes I'll leave it for 2 days and have 200+Ah to put back into the batteries. On many days the charge might be a bit fragmentary- an hour here and there perhaps, depending on whether I have boats close by, or how flat the batteries are first thing in the morning. On work days I dont like having the engine running between 9am and 5pm if possible. With that objective in mind of getting from (say) 50% to 85% with as little diesel used as possible, and within the scenario of snatching an hour here or there to do the charging, is there a case for creating a charging profile for the winter months, with the following characteristics: 1. a higher bulk voltage (say 14.4v) to speed things up (and would the 85% SoC target be reached more quickly than it would be if charging at say 13.8v?) 2. zero time spent at the target voltage, once it has been reached (on my Sterling there is a setting to control that). Bear in mind on most winter days, within the 90 mins engine running, I wont get to the target voltage anyway. 3. Second charge phase is set at 13.7v. The thinking here is that if the batteries have reached 14.2v in the first phase (at my low charge current), they will be brim full, so let them discharge a bit. But (as is more likely) if they havent gotten above 13.7v in the bulk charging phase, then they will get a further chance in the second phase to pick up a decent amount of charge One of the complicating factors in summer (not so much in winter) seems to be that the measurement of battery voltage during daylight is confused by the fact that they are constantly being charged by the solar, and I've noticed that when under charge, their voltage is not the same as it is when measured with no charge (I think you called this 'resting'). So when its sunny, the B2B is reading a charging voltage, but when its crappy weather, its reading what seems more like a resting voltage, and the thresholds and trigger voltages that it works with are more difficult to be certain about. Perhaps in part you are still suffering from an urge to keep the SoC in the upper half (LA habits)? Why take that batteries from 50% to 85% rather than 20% to 55%? Ok I suppose one answer is to have a margin in the event of unexpectedly being unable to charge. But my point is that 20% SoC is no better or worse than 80% SoC. That takes some getting used to! 13.7 volts, held for long enough, will take the SoC to 100%. On your specific questions: 1) it depends on the charge profile of the charging device, ie how much the current decreases before the target voltage is reached, but generally yes I think so. Equally one of the bad things that happens to Li is metallic lithium plating on the electrode. This basically happens when you try to ram charge into the battery faster than the reaction can progress. It’s particularly an issue at low temperatures (because reaction rate is slow) and is the reason why max charge current is usually quoted as 1C. Of course you are well below that and I think your limiting factor will be the paltry 45A coming out of the B2B so it probably won’t make much difference. By the time the B2B has staggered up to 13.8v the battery will be pretty close to 100% and 5 mins later it will be at 14.4v so it won’t make much difference. 2) zero time at the target voltage is safe, but if you want to get to 100% (maybe you don’t) you need to hold the target voltage until the current decreases to about 5% capacity. Mind you, you are only starting at a current of 10% capacity so the CV phase won’t last long. 3) 13.7v is not any sort of discharge voltage, the batteries will continue to charge to 100% albeit more slowly. It is tricky trying to adapt LA battery charging devices to Li, because as we’ve said plenty of times, for Li you want to charge until you reach a certain voltage, hold that voltage, then when the current drops to 5%, stop charging altogether or at least drop the charge voltage to a fully charged zero current value of around 13.35. Or maybe 13.25 to avoiding the SoC being at 100% for the rest of the daySo the charger needs to act on % current and voltage, and for it to act on % current it needs to know the capacity of the battery it’s connected to. LA chargers just don’t seem to work like that.
|
|
|
Post by kris on Mar 7, 2021 20:38:49 GMT
Perhaps in part you are still suffering from an urge to keep the SoC in the upper half (LA habits)? Why take that batteries from 50% to 85% rather than 20% to 55%? Ok I suppose one answer is to have a margin in the event of unexpectedly being unable to charge. But my point is that 20% SoC is no better or worse than 80% SoC. That takes some getting used to! Ain’t that the truth. You would be better off knowing nothing of batteries and charging and it all being new. It’s relearning the habits of a lifetime.
|
|
|
Post by kris on Mar 8, 2021 15:30:28 GMT
So today I got my laptop to connect to the victron inverter, I had to update the firmware to be able to configure the settings in the inverter. Which I managed to do no problems. So I got the configure program working,went to alter the low voltage cutout to maybe 12.9v in order to add protection to my lifepo4’s. How ever if I set the low value to 12.9v the reset value is limited to 13.9v which is too high. It seems like an idiosyncrasy of the victron configure software that the reset value has to be 1v higher than the cut out voltage. I’m wondering what to do? I’m getting there just this to sort out and then program the mppt then I’ll be on for upgrading my solar to 2.2kw. I’m beginning to trust the relay to protect the batteries which is reassuring as they are such a big investment for me. Ps does anybody know if it’s worth turning the aes system on?
|
|
|
Post by Telemachus on Mar 8, 2021 16:09:09 GMT
So today I got my laptop to connect to the victron inverter, I had to update the firmware to be able to configure the settings in the inverter. Which I managed to do no problems. So I got the configure program working,went to alter the low voltage cutout to maybe 12.9v in order to add protection to my lifepo4’s. How ever if I set the low value to 12.9v the reset value is limited to 13.9v which is too high. It seems like an idiosyncrasy of the victron configure software that the reset value has to be 1v higher than the cut out voltage. I’m wondering what to do? I’m getting there just this to sort out and then program the mppt then I’ll be on for upgrading my solar to 2.2kw. I’m beginning to trust the relay to protect the batteries which is reassuring as they are such a big investment for me. Ps does anybody know if it’s worth turning the aes system on? I think 12.9v is too high anyway. Under heavy load the inverter input voltage will dip due to a combination of cell internal resistance, wiring to the inverter, voltage drop at the fuse and isolator etc. Bearing in mind 10v no load is the absolute minimum voltage, 12.9 under load is way, way above that. I’d set it to say 12v and then the recovery voltage will be 13v which is not too bad. Or just rely on the BMV /BGB. Not sure if the inverter has a time delay before tripping out due to undervoltage, but if not you will get nuisance trips from momentary voltage dips as a heavy load kicks in. Whereas as we know, the BMV applies a 10 second delay. As to AES it rather depends on what you have connected to it. If you have small loads eg phone chargers, oven clocks etc then they may not be enough to take it out of AES mode and they might not like the funny AES waveform. On the other hand if the loads you intend to use are all reasonably big (enough to exit AES mode) then it will be fine, and AES will save you a bit of power when the inverter is on but not doing anything
|
|
|
Post by kris on Mar 8, 2021 17:20:14 GMT
So today I got my laptop to connect to the victron inverter, I had to update the firmware to be able to configure the settings in the inverter. Which I managed to do no problems. So I got the configure program working,went to alter the low voltage cutout to maybe 12.9v in order to add protection to my lifepo4’s. How ever if I set the low value to 12.9v the reset value is limited to 13.9v which is too high. It seems like an idiosyncrasy of the victron configure software that the reset value has to be 1v higher than the cut out voltage. I’m wondering what to do? I’m getting there just this to sort out and then program the mppt then I’ll be on for upgrading my solar to 2.2kw. I’m beginning to trust the relay to protect the batteries which is reassuring as they are such a big investment for me. Ps does anybody know if it’s worth turning the aes system on? I think 12.9v is too high anyway. Under heavy load the inverter input voltage will dip due to a combination of cell internal resistance, wiring to the inverter, voltage drop at the fuse and isolator etc. Bearing in mind 10v no load is the absolute minimum voltage, 12.9 under load is way, way above that. I’d set it to say 12v and then the recovery voltage will be 13v which is not too bad. Or just rely on the BMV /BGB. Not sure if the inverter has a time delay before tripping out due to undervoltage, but if not you will get nuisance trips from momentary voltage dips as a heavy load kicks in. Whereas as we know, the BMV applies a 10 second delay. As to AES it rather depends on what you have connected to it. If you have small loads eg phone chargers, oven clocks etc then they may not be enough to take it out of AES mode and they might not like the funny AES waveform. On the other hand if the loads you intend to use are all reasonably big (enough to exit AES mode) then it will be fine, and AES will save you a bit of power when the inverter is on but not doing anything I did think of setting the low voltage at 12v, but then thought that it won’t ever be used as the relay will cut out before then. My original intention was to get the inverter to cut out before the relay. So when in the position of a constant load draining the battery the heavy loads ie inverter would cut out before threatening the batteries.
|
|
|
Post by Telemachus on Mar 8, 2021 17:38:12 GMT
I think 12.9v is too high anyway. Under heavy load the inverter input voltage will dip due to a combination of cell internal resistance, wiring to the inverter, voltage drop at the fuse and isolator etc. Bearing in mind 10v no load is the absolute minimum voltage, 12.9 under load is way, way above that. I’d set it to say 12v and then the recovery voltage will be 13v which is not too bad. Or just rely on the BMV /BGB. Not sure if the inverter has a time delay before tripping out due to undervoltage, but if not you will get nuisance trips from momentary voltage dips as a heavy load kicks in. Whereas as we know, the BMV applies a 10 second delay. As to AES it rather depends on what you have connected to it. If you have small loads eg phone chargers, oven clocks etc then they may not be enough to take it out of AES mode and they might not like the funny AES waveform. On the other hand if the loads you intend to use are all reasonably big (enough to exit AES mode) then it will be fine, and AES will save you a bit of power when the inverter is on but not doing anything I did think of setting the low voltage at 12v, but then thought that it won’t ever be used as the relay will cut out before then. My original intention was to get the inverter to cut out before the relay. So when in the position of a constant load draining the battery the heavy loads ie inverter would cut out before threatening the batteries. Well you could always lower the trigger voltage on the BMV!
|
|
|
Post by kris on Mar 8, 2021 17:53:32 GMT
I did think of setting the low voltage at 12v, but then thought that it won’t ever be used as the relay will cut out before then. My original intention was to get the inverter to cut out before the relay. So when in the position of a constant load draining the battery the heavy loads ie inverter would cut out before threatening the batteries. Well you could always lower the trigger voltage on the BMV! That’s true. I’ll have ago at setting the mppt tmw then see I need to order my new solar panels, I’m sure enough of the bmv- relay now. I’m charging them right now with the generator, they have just been between 13.2-12.8v this last week with the amount of charge from the current 700ish watts of solar I’ve got at the moment. So I’ll raise the voltage synchronise the bmv and see what happens.
|
|
|
Post by kris on Mar 10, 2021 13:59:48 GMT
so ive been thinking about the settings for the mppt controller again ive read the Morningstar document and think these settings will work for me. well I at least want to turn float off,what do people think? dhttps://2n1s7w3qw84d2ysnx3ia2bct-wpengine.netdna-ssl.com/wp-content/uploads/2018/04/Lithium-Iron-Phosphate-LiFePO4-Generic-Charge-Settings.pdf
|
|
|
Post by kris on Mar 12, 2021 13:49:16 GMT
I’ve been reading around and watching YouTube videos about what the settings should be on my mppt controller. It’s confusing to know what’s for the best. Here’s a video from a lifepo4 manufacturer well rebrander maybe. That say the absorption voltage should be 14.6v
|
|
|
Post by peterboat on Mar 12, 2021 14:15:59 GMT
I’ve been reading around and watching YouTube videos about what the settings should be on my mppt controller. It’s confusing to know what’s for the best. Here’s a video from a lifepo4 manufacturer well rebrander maybe. That say the absorption voltage should be 14.6v Kris for many years James, John and I have gone the 13.8/9 bulk 13.6 absorb 13.4/5 float, it works batteries still working as they should, yes it lower than the maximum that Valence charge at but its within the 20-80% long life routine for lithium batteries.
|
|
|
Post by kris on Mar 12, 2021 14:48:21 GMT
I’ve been reading around and watching YouTube videos about what the settings should be on my mppt controller. It’s confusing to know what’s for the best. Here’s a video from a lifepo4 manufacturer well rebrander maybe. That say the absorption voltage should be 14.6v Kris for many years James, John and I have gone the 13.8/9 bulk 13.6 absorb 13.4/5 float, it works batteries still working as they should, yes it lower than the maximum that Valence charge at but its within the 20-80% long life routine for lithium batteries. yes I’m aware of this peter. I’m just interested in finding out the best settings for my mppt. I find it interesting that there is so much variance in recommended settings. As you know these batteries need no float so I have the option to turn that off.
|
|
|
Post by Telemachus on Mar 12, 2021 15:43:02 GMT
I’ve been reading around and watching YouTube videos about what the settings should be on my mppt controller. It’s confusing to know what’s for the best. Here’s a video from a lifepo4 manufacturer well rebrander maybe. That say the absorption voltage should be 14.6v No he says 14.4 for absorption voltage. 14.6 is high voltage disconnect. In my view, because the charge current is relatively low compared to the capacity (although I guess it depends on how much panel wattage you have) that by the time the system voltage gets to 13.8 the batteries will be virtually fully charged and very little extra charge will be added between 13.8 and 14.4, whereas quite a bit of extra stress will be added.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Mar 12, 2021 15:45:07 GMT
Quite a lot of people advocate under 14v on the MPPT for LFP batteries. I've set mine at 13.6. I think this means a slightly lower capacity but more life. That's the theory.
There is a lot of discussion about 14.5v+ being quite damaging specially if the batteries sit at this voltage for extended time periods, which seems likely in summer with solar input.
|
|
|
Post by kris on Mar 12, 2021 15:53:31 GMT
Soon to have 2.2kw of panels so lots of power in the summer. I’m just kind of thinking aloud really. But it’s interesting the differing opinions.
|
|