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Post by duncan on Oct 7, 2021 23:49:46 GMT
Yeah, but will he blab my dirty secret? Has Nick sorted the issue?
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Post by Deleted on Oct 8, 2021 8:08:42 GMT
Yeah, but will he blab my dirty secret? Has Nick sorted the issue? Yes, he did. Thanks Nick
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Post by peterboat on Oct 8, 2021 8:52:38 GMT
Hi Rusty, I have a pair of midnite solar controllers one for drive one for domestic, my domestic bank is the same a s johns 6 x valence 12 volts batteries set for 24 volts. My inverter is a Victron it closes down at 20 odd volts I have deliberately run it down to try it Valance batteries have a battery balancing board rather than a BMS, it is independent of the master BMS that controls it for cutoff. Charging with Midnite controllers is easy you set up parameters in my case 13.9 Bulk, 13,8 absorb and 13,4 float when it goes into float no amps go into the battery it will drop down to 13.4 as power is used from the 13.8 absorb, when it hits that point if its small loads it just covers the outgoings if I turn the kettle on it starts the cycle again and goes into bulk, absorb then float. I can watch this on the screen of the controller or my NASA in the boat. Shortly I will befitting my genny which is replacing the Whispergen, I will be fitting a 24 volt alternator to it or having the old one doctored, charging of the 72 volt battery will be done with a 72 volt charger on top of the solar. My current emergency charging for domestic is a 24 volt CTEC battery charger it has never over charged and has a supply function as well which is well withing the batteries limits. Valence batteries operates at higher voltages than LifePo4s maximum is 14.6 volts from memory so John and I are erring on the side of safety. Nick is right about alternators I have never in my garage years changed on for overcharging its always a failure, but there will be a first time hopefully not with me though
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Post by Deleted on Oct 8, 2021 9:19:30 GMT
Thanks Peter.
It sounds like both you and JohnV rely on only the inverter low voltage shut down and built in BMS function of the valence batteries to protect them from a low discharge event. You both appear to be on mains hook up for a lot of the time, and have a large amount of solar for any cruising in the summer months, so I can see how this would work for you both. If the batteries become overly discharged, you can simply turn on the battery charger,or generator, but that is unlikely to happen in the winter as you will be relying on the mains anyway.
During the summer, you will have heaps of solar. If you have no large DC loads other than the inverter (fridges freezers, heaters etc) it is clearly possible to go down this route.
Do you have any audible low voltage alarm installed?
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Post by peterboat on Oct 8, 2021 12:18:04 GMT
Thanks Peter. It sounds like both you and JohnV rely on only the inverter low voltage shut down and built in BMS function of the valence batteries to protect them from a low discharge event. You both appear to be on mains hook up for a lot of the time, and have a large amount of solar for any cruising in the summer months, so I can see how this would work for you both. If the batteries become overly discharged, you can simply turn on the battery charger,or generator, but that is unlikely to happen in the winter as you will be relying on the mains anyway. During the summer, you will have heaps of solar. If you have no large DC loads other than the inverter (fridges freezers, heaters etc) it is clearly possible to go down this route. Do you have any audible low voltage alarm installed? No audible alarms other than the inverter, my Fridge freezer is 12/24 volts so I have a constant dc load, my water pump is 240 volts! and the local fire brigade borrow it for emergencies!! As for shoreline rarely do I use it, the whispergen sufficed to keep the amps up and the genny will do the same I hope, that and the 4.6kw of solar
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Post by Deleted on Oct 28, 2021 19:42:34 GMT
Heeeellllllp.
My top balancing is not going well.
I connected all my 28 cells (4 x 7) as a 12 volt battery, connected the BMS and waited for it to cut out at 14,4V (3.6v/cell). I then disconnected and charged the 7 parallel cells at 3.6V (current set to 9A on PSU). The bank would only take about 0.5A at 3.57V (on PSU). Increasing it to 3.8 V gave the full 9A output, but will this damage the cells?
I'm beginning to think my cells may be U/S (hence the reason they were cheap).
Any ideas please
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Post by Telemachus on Oct 28, 2021 20:24:15 GMT
Heeeellllllp. My top balancing is not going well. I connected all my 28 cells (4 x 7) as a 12 volt battery, connected the BMS and waited for it to cut out at 14,4V (3.6v/cell). I then disconnected and charged the 7 parallel cells at 3.6V (current set to 9A on PSU). The bank would only take about 0.5A at 3.57V (on PSU). Increasing it to 3.8 V gave the full 9A output, but will this damage the cells? I'm beginning to think my cells may be U/S (hence the reason they were cheap). Any ideas please I’m not quite sure what you’re trying to do? You said the charger cut out at 14.4v - 3.6v per cell. But was that the actual cell voltages? Or just 14.4 divided by 4? The aim is to be able to reach a sensible charge voltage like 14.4v without any one cell going over 3.65v. If you have already done that, then the cells are adequately top balanced. If when you hit 14.4v one or more cells was over 3.65v then you need to add some charge to the lower cells or discharge the higher cells. And it would have been better not to hit 14.4v if any cells went over 3.65v. Bear in mind there is virtually no additional Ah to be had between charging to say 3.5v per cell and 3.65v per cell, if the charge current is allowed to subside.
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Post by Deleted on Oct 28, 2021 20:32:25 GMT
Thanks nick.
I set the BMS to cut out at 14. 4V or 3. 6v/ cell,whichever it reached first. One cell (bank of 7) hit that voltage, the BMS cut out and stopped charging.
At this point, I disconnected the bank and continued to charge 7 cells in parallel at 3. 6V.
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Post by Telemachus on Oct 28, 2021 20:41:20 GMT
Thanks nick. I set the BMS to cut out at 14. 4V or 3. 6v/ cell,whichever it reached first. One cell (bank of 7) hit that voltage, the BMS cut out and stopped charging. At this point, I disconnected the bank and continued to charge 7 cells in parallel at 3. 6V. Do you know what the other bank voltages were when the top bank hit 3.6v? Anyway if you take the other 3 banks, one at a time, up to 3.6v and wait for the current to subside, that is job done.
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Post by Deleted on Oct 28, 2021 20:43:10 GMT
Thanks nick. I set the BMS to cut out at 14. 4V or 3. 6v/ cell,whichever it reached first. One cell (bank of 7) hit that voltage, the BMS cut out and stopped charging. At this point, I disconnected the bank and continued to charge 7 cells in parallel at 3. 6V. Do you know what the other bank voltages were when the top bank hit 3.6v? Anyway if you take the other banks, one at a time,up,to 3.6v and wait for the current to subside, that is job done. 3.543 3.550 3.535
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Post by Telemachus on Oct 28, 2021 20:46:23 GMT
Do you know what the other bank voltages were when the top bank hit 3.6v? Anyway if you take the other banks, one at a time,up,to 3.6v and wait for the current to subside, that is job done. 3.543 3.550 3.535 So they are well up the knee then. You don’t need to add much to them to get them balanced. Or just take an Ah or so out of the top cell bank using a suitable resistor. Remind me what the total capacity of the 7 paralleled cells is?
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Post by Deleted on Oct 28, 2021 20:46:29 GMT
Thanks nick. I set the BMS to cut out at 14. 4V or 3. 6v/ cell,whichever it reached first. One cell (bank of 7) hit that voltage, the BMS cut out and stopped charging. At this point, I disconnected the bank and continued to charge 7 cells in parallel at 3. 6V. Do you know what the other bank voltages were when the top bank hit 3.6v? Anyway if you take the other 3 banks, one at a time, up to 3.6v and wait for the current to subside, that is job done. At 3.6V the other cells take very it little current. Job done?
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Post by Deleted on Oct 28, 2021 20:51:13 GMT
So they are well up the knee then. You don’t need to add much to them to get them balanced. Or just take an Ah or so out of the top cell bank using a suitable resistor. Remind me what the total capacity of the 7 paralleled cells is? They are 40Ahr cells.
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Post by Telemachus on Oct 28, 2021 21:29:34 GMT
I think if you connect the power supply to each of the 4 banks set to 3.6v or maybe 3.65v if you like, and the current is below an amp in each case, that is job done.
Obviously to check, you can repeat the charge to 14.4v (having discharged a bit) and check that the cell banks are all close to 3.6v.
Personally I am only charging to 14.3v and stopping charge when current falls to 5% of capacity. Because to go up to the allowed max of 14.6v adds less than an Ah (out of 600) so I don’t see the point. You only have 280Ah so in terms of Ah you would gain even less by taking it right up to the max.
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Post by Deleted on Oct 28, 2021 21:36:25 GMT
I think if you connect the power supply to each of the 4 banks set to 3.6v or maybe 3.65v if you like, and the current is below an amp in each case, that is job done. Obviously to check, you can repeat the charge to 14.4v (having discharged a bit) and check that the cell banks are all close to 3.6v. Personally I am only charging to 14.3v and stopping charge when current falls to 5% of capacity. Because to go up to the allowed max of 14.6v adds less than an Ah (out of 600) so I don’t see the point. You only have 280Ah so in terms of Ah you would gain even less by taking it right up to the max. Cheers nick. I will try that tomorrow. I was expecting more current going in tbh.
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