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Post by Telemachus on Apr 4, 2021 18:21:02 GMT
Nicks gone quiet about his batteries? Not really, I left the boat on Friday morning to come home. So no more information to impart until we can get back to it - remember there is still a travel ban in North Korea - I mean Scotland of course! Not allowed out of local authority area except for essential purposes, until April 26th. The status is that I still need to make up and run a cable between BMS and the Tyco, so currently the batteries are “unprotected” but I set the Combi to Forced Float with a voltage of 13.25v so hopefully they will be OK! I also need to make up rather long cable to connect the BMV to the BMS as my intention is to use that as the primary SoC reference. Also need to make up some packing to firmly locate the batteries, and find 50kg of ballast weight from something. I have taken measurements for all the above so hopefully next time I can get down, it can be sorted fairly quickly. I did tidy up the wires with a selection of tywraps before I left, but forgot to take any photos.
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Post by Telemachus on Apr 4, 2021 18:28:07 GMT
And I’m knackered, left the boat at 2pm to drive the 425 miles, got home about 10pm, then up at 8 the next morning to drive the 85 cross-country miles to the gliding club. Busy weekend at the gliding club doing various chores, now just got home and relaxing with a nice glass of Cava supplied by Jeff.
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Post by kris on Apr 4, 2021 18:34:54 GMT
And I’m knackered, left the boat at 2pm to drive the 425 miles, got home about 10pm, then up at 8 the next morning to drive the 85 cross-country miles to the gliding club. Busy weekend at the gliding club doing various chores, now just got home and relaxing with a nice glass of Cava supplied by Jeff. Ah you poor thing bless. Don’t forget that lithium’s will stay at rest without any harm for long periods 50% is recommended. So perhaps no need to charge whilst away from the boat.
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Post by Telemachus on Apr 4, 2021 18:42:22 GMT
And I’m knackered, left the boat at 2pm to drive the 425 miles, got home about 10pm, then up at 8 the next morning to drive the 85 cross-country miles to the gliding club. Busy weekend at the gliding club doing various chores, now just got home and relaxing with a nice glass of Cava supplied by Jeff. Ah you poor thing bless. Don’t forget that lithium’s will stay at rest without any harm for long periods 50% is recommended. So perhaps no need to charge whilst away from the boat. Yes I did consider unplugging the shore power and would have done so if it was “just me”, but it might be that Jeff goes down before me, so I thought I’d just leave things as usual. When I left, the SoC was around 75% (which was a bit high for ideal, but probably OK) with the voltage around 13.3v. By setting the float voltage to 13.25 zero current was flowing into the batteries but it means that if Jeff uses 12v power, the Combi will start to provide power if the voltage drops just a bit further.
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Post by peterboat on Apr 4, 2021 18:54:16 GMT
Ah you poor thing bless. Don’t forget that lithium’s will stay at rest without any harm for long periods 50% is recommended. So perhaps no need to charge whilst away from the boat. Yes I did consider unplugging the shore power and would have done so if it was “just me”, but it might be that Jeff goes down before me, so I thought I’d just leave things as usual. When I left, the SoC was around 75% (which was a bit high for ideal, but probably OK) with the voltage around 13.3v. By setting the float voltage to 13.25 zero current was flowing into the batteries but it means that if Jeff uses 12v power, the Combi will start to provide power if the voltage drops just a bit further. They will be fine for our sort of use and a few weeks nearly full charged wouldnt do any harm. I leave my drive batteries at 60% all winter but the other day fully charged them ready go and they will be like that most of the season
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Post by kris on Apr 4, 2021 18:54:20 GMT
Ah you poor thing bless. Don’t forget that lithium’s will stay at rest without any harm for long periods 50% is recommended. So perhaps no need to charge whilst away from the boat. Yes I did consider unplugging the shore power and would have done so if it was “just me”, but it might be that Jeff goes down before me, so I thought I’d just leave things as usual. When I left, the SoC was around 75% (which was a bit high for ideal, but probably OK) with the voltage around 13.3v. By setting the float voltage to 13.25 zero current was flowing into the batteries but it means that if Jeff uses 12v power, the Combi will start to provide power if the voltage drops just a bit further. Ah I see. I’m still having difficult really with soc. The majority of the time I’ve been using mine they have been around 13.4-13.5 so I’ve no idea what their soc would be? I manually set the soc the other day when I charged them 13.8v I can’t remember the soc I set I think I guessed at 80%.ish. But it’s something I need to sort out . I’m fitting 2.2kw of solar tmw so I’ll see what that does.
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Post by kris on Apr 4, 2021 18:55:28 GMT
Yes I did consider unplugging the shore power and would have done so if it was “just me”, but it might be that Jeff goes down before me, so I thought I’d just leave things as usual. When I left, the SoC was around 75% (which was a bit high for ideal, but probably OK) with the voltage around 13.3v. By setting the float voltage to 13.25 zero current was flowing into the batteries but it means that if Jeff uses 12v power, the Combi will start to provide power if the voltage drops just a bit further. They will be fine for our sort of use and a few weeks nearly full charged wouldnt do any harm. I leave my drive batteries at 60% all winter but the other day fully charged them ready go and they will be like that most of the season Yes this is one of the many advantages that they have. I really like mine now.
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Post by peterboat on Apr 4, 2021 18:58:07 GMT
They will be fine for our sort of use and a few weeks nearly full charged wouldnt do any harm. I leave my drive batteries at 60% all winter but the other day fully charged them ready go and they will be like that most of the season Yes this is one of the many advantages that they have. I really like mine now. I couldnt cope with LAs now to much hard work
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Post by kris on Apr 4, 2021 19:03:10 GMT
Yes this is one of the many advantages that they have. I really like mine now. I couldnt cope with LAs now to much hard work I wouldn’t want to go back.
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Post by Telemachus on Apr 4, 2021 19:17:50 GMT
13.4v as a rested zero current voltage is around 90% SoC. See the chart I posted on the previous page. Above 90% you can start to get some idea of SoC from voltage, but between 10% and 90% the voltage is pretty flat. I think that realistically, the only way is to synchronise the BMV at close to 100% from time to time, and just use the BMV SoC in the intervening time. Errors will accumulate but until I get to actually use our system “in anger” I wouldn’t like to say how quickly the BMV SoC will drift off to the point it’s a problem.
If you charged to 13.8 and held that for a while, or charged slowly, that is virtually 100%.
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Post by peterboat on Apr 4, 2021 19:42:45 GMT
13.4v as a rested zero current voltage is around 90% SoC. See the chart I posted on the previous page. Above 90% you can start to get some idea of SoC from voltage, but between 10% and 90% the voltage is pretty flat. I think that realistically, the only way is to synchronise the BMV at close to 100% from time to time, and just use the BMV SoC in the intervening time. Errors will accumulate but until I get to actually use our system “in anger” I wouldn’t like to say how quickly the BMV SoC will drift off to the point it’s a problem. If you charged to 13.8 and held that for a while, or charged slowly, that is virtually 100%. Valence batteries Nick 14.6 volts is full I have at the beginning charged all mine to that and the SOC on the puter resets to that 13.8/9 is 80% according to the battery software. I think Kris has the software so he could do the same on a one at a time exercise with the battery plugged into the puter, they would then be all top balanced like mine were, how long that lasts I have no idea? But it was last done over 4 years ago
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Post by Telemachus on Apr 4, 2021 22:12:17 GMT
13.4v as a rested zero current voltage is around 90% SoC. See the chart I posted on the previous page. Above 90% you can start to get some idea of SoC from voltage, but between 10% and 90% the voltage is pretty flat. I think that realistically, the only way is to synchronise the BMV at close to 100% from time to time, and just use the BMV SoC in the intervening time. Errors will accumulate but until I get to actually use our system “in anger” I wouldn’t like to say how quickly the BMV SoC will drift off to the point it’s a problem. If you charged to 13.8 and held that for a while, or charged slowly, that is virtually 100%. Valence batteries Nick 14.6 volts is full I have at the beginning charged all mine to that and the SOC on the puter resets to that 13.8/9 is 80% according to the battery software. I think Kris has the software so he could do the same on a one at a time exercise with the battery plugged into the puter, they would then be all top balanced like mine were, how long that lasts I have no idea? But it was last done over 4 years ago Valence batteries are lithium magnesium ferrophosphate, but as far as I can tell the magnesium bit is for cycle life improvement and doesn’t alter the voltage SoC relationship. Well at least, I can find no evidence that it does. There does seem to be scant information about it on the internet. I just watched a video from Southwest EV capacity testing valence batteries, he says the battery was fully charged. He then put on his discharge gadget but before he actually started the discharge, the voltage was 40.4v which, for a 12v battery, would be 13.47. This ties in with what I’ve found with my straight Lithium ferrophosphate (no magnesium) batteries, although perhaps a bit lower voltage than might be expected. It therefore seems to me that if the voltage is held much above say 13.6v until the current subsides to zero, it will be fully charged. But perhaps the root of the issue is about the exact conditions and circumstances we are both talking about. If you are talking about charging fairly fast and then terminating the charge as soon as 13.8v is reached, then yes I can believe 80%. But I am struggling to believe that 80% SoC rested open circuit voltage is 13.8v. Can you be more precise as to exactly what you mean? At the end of the day Kris can fully charge his batteries until the knee is climbed to 14.6 at a fairly low current, reset the BMV to 100%, discharge until the BMV says 80%, remove the load and let it rest a bit, and then note the voltage. I will be very surprised if it is anything like 13.8v and I think it will be more like 13.3v. If it is, then clearly the magnesium does have a significant effect on the voltage SoC curve but as I said, I will be surprised.
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Post by peterboat on Apr 5, 2021 8:11:16 GMT
Valence batteries Nick 14.6 volts is full I have at the beginning charged all mine to that and the SOC on the puter resets to that 13.8/9 is 80% according to the battery software. I think Kris has the software so he could do the same on a one at a time exercise with the battery plugged into the puter, they would then be all top balanced like mine were, how long that lasts I have no idea? But it was last done over 4 years ago Valence batteries are lithium magnesium ferrophosphate, but as far as I can tell the magnesium bit is for cycle life improvement and doesn’t alter the voltage SoC relationship. Well at least, I can find no evidence that it does. There does seem to be scant information about it on the internet. I just watched a video from Southwest EV capacity testing valence batteries, he says the battery was fully charged. He then put on his discharge gadget but before he actually started the discharge, the voltage was 40.4v which, for a 12v battery, would be 13.47. This ties in with what I’ve found with my straight Lithium ferrophosphate (no magnesium) batteries, although perhaps a bit lower voltage than might be expected. It therefore seems to me that if the voltage is held much above say 13.6v until the current subsides to zero, it will be fully charged. But perhaps the root of the issue is about the exact conditions and circumstances we are both talking about. If you are talking about charging fairly fast and then terminating the charge as soon as 13.8v is reached, then yes I can believe 80%. But I am struggling to believe that 80% SoC rested open circuit voltage is 13.8v. Can you be more precise as to exactly what you mean? At the end of the day Kris can fully charge his batteries until the knee is climbed to 14.6 at a fairly low current, reset the BMV to 100%, discharge until the BMV says 80%, remove the load and let it rest a bit, and then note the voltage. I will be very surprised if it is anything like 13.8v and I think it will be more like 13.3v. If it is, then clearly the magnesium does have a significant effect on the voltage SoC curve but as I said, I will be surprised. The batteries own internal BMS has a SOC meter, its what for me dictates its state of charge. If kris does as you say and slowly charges the batteries on an individual basis, whilst the battery is connected to the valence software, he will when he hits 14.6 volts and all cells balanced have a 100% SOC. I did it using a 180 watt solar panel and solar charger. I did it in stages starting at 13.8 for all the batteries then 13.9 etc until I hit 14.6 its because I was putting the batteries in series that I did top balancing the once. I then found that when the batteries were discharged to 13.8/9 the internal BMS says the batteries are at 80%, which is why I bulk charge to this voltage, absorb at 13.6 and float currently 13.4 volts as I am not at the boat. I have stuck to these voltages for years with no ill effects and John with the same batteries uses similar voltages
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Post by kris on Apr 5, 2021 8:56:13 GMT
It is definately confusing I’m happy with not really knowing the real soc as long as I’ve got a reasonably accurate voltage reading and am aware of amps in and out. Unfortunately whilst james connected them to his computer and showed me that they are balanced and the number of cycles. I haven’t had any luck with the software myself. Mine are the older ones with the small round connectors I managed to make a lead but can’t get them to communicate. I think I need a new copy of the software but I don’t think it can be found on the internet any more. But I’m happy with how they are. I’ve got a 12v bank though so no complications with the parallel series situation.
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Post by Telemachus on Apr 5, 2021 10:22:14 GMT
Valence batteries are lithium magnesium ferrophosphate, but as far as I can tell the magnesium bit is for cycle life improvement and doesn’t alter the voltage SoC relationship. Well at least, I can find no evidence that it does. There does seem to be scant information about it on the internet. I just watched a video from Southwest EV capacity testing valence batteries, he says the battery was fully charged. He then put on his discharge gadget but before he actually started the discharge, the voltage was 40.4v which, for a 12v battery, would be 13.47. This ties in with what I’ve found with my straight Lithium ferrophosphate (no magnesium) batteries, although perhaps a bit lower voltage than might be expected. It therefore seems to me that if the voltage is held much above say 13.6v until the current subsides to zero, it will be fully charged. But perhaps the root of the issue is about the exact conditions and circumstances we are both talking about. If you are talking about charging fairly fast and then terminating the charge as soon as 13.8v is reached, then yes I can believe 80%. But I am struggling to believe that 80% SoC rested open circuit voltage is 13.8v. Can you be more precise as to exactly what you mean? At the end of the day Kris can fully charge his batteries until the knee is climbed to 14.6 at a fairly low current, reset the BMV to 100%, discharge until the BMV says 80%, remove the load and let it rest a bit, and then note the voltage. I will be very surprised if it is anything like 13.8v and I think it will be more like 13.3v. If it is, then clearly the magnesium does have a significant effect on the voltage SoC curve but as I said, I will be surprised. The batteries own internal BMS has a SOC meter, its what for me dictates its state of charge. If kris does as you say and slowly charges the batteries on an individual basis, whilst the battery is connected to the valence software, he will when he hits 14.6 volts and all cells balanced have a 100% SOC. I did it using a 180 watt solar panel and solar charger. I did it in stages starting at 13.8 for all the batteries then 13.9 etc until I hit 14.6 its because I was putting the batteries in series that I did top balancing the once. I then found that when the batteries were discharged to 13.8/9 the internal BMS says the batteries are at 80%, which is why I bulk charge to this voltage, absorb at 13.6 and float currently 13.4 volts as I am not at the boat. I have stuck to these voltages for years with no ill effects and John with the same batteries uses similar voltages I’d agree that the internal SoC is probably the best indicator of SoC. Although I suppose we don’t actually know how accurate it is. But something isn’t adding up. You say that 13.8v is the zero current voltage after discharging to 80% SoC. Unfortunately I can’t find any graphs of zero current voltage vs SoC for valence batteries. However, there is Valence’s own graph for voltage at various rates of discharge, all of the curves are fairly fast discharges, there’s one at C/5 and one at C/3. These give about 13.25v and 13.15v at 80%. Of course, one would expect the voltage to be lower under discharge, than at zero current. Then I looked for a graph of standard LiFePO4 discharge voltage, found one at C/4, which gave 13.25 at 80% SoC which is commensurate with my findings. If we take the mid point of the Valence C/5 and C/3 to give an estimate for C/4 it would be 13.2v. So slightly lower than for standard LiFePO4, and this might be explained the the longer wiring runs inside the battery (interconnecting all the small cells) and the probably presence of some kind of shunt within the Valence battery. But anyway, with these figures being very close to the standard LiFePO4 it seems to me unlikely that the magnesium has any significant effect on the voltage vs SoC relationship. And for standard LiFePO4 the zero current voltage at 80% SoC is about 13.3v, which is a long way away from your 13.8v. As I said, something doesn’t add up. And looking at Valence’s own graph, surely it is unfeasible that the voltage would drop from 13.8v at 80% SoC no load, to about 13.3v at C/8? Li batteries just aren’t like that! In summary I would agree that your charging voltages are entirely ok, but I suggest that actually you are charging close to 100% or certainly to well over 80%. How close depends on how long you hold the 13.8v after reaching it, how long you hold the 13.6 after reaching it.
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