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Post by Deleted on Jan 18, 2021 7:57:32 GMT
I thought this had been established ages ago!
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Post by Telemachus on Jan 18, 2021 8:20:24 GMT
Just remember, Red to red Black to black Blown Blue to bits.
With your stupid comments you sound just like a spoilt child trying to impress everyone with his knowledge.
You just end up looking like an insecure individual who requires constant approbation
Well at least I’m not in competition with Tony Dunkley for the grumpiest old git on the forum. And yes you are right, blue not blown.
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Post by kris on Jan 18, 2021 9:34:54 GMT
Anyway, now that nursey has given the grumpy one his medication and he’s gone sleepibyes, I’ve done a bit of research on SoC vs voltage. I took a rested 200Ah battery, added 10% SoC quite slowly at 5A to take it up to 50% SoC, then started logging the voltage and disconnected the charger. You can see the voltage subsides over many hours towards its ultimate rested voltage - after 16 hours it probably hasn’t quite got there. So in terms of trying to identify SoC from voltage, bearing in mind the very flat discharge curve, that 0.08v droop is quite significant. So even with loads turned off (current temporarily zero) you can’t really work out the SoC unless you know the charge/discharge history or leave it at zero current for a day. It's useful to know how long they take to get down to a 'stable' resting voltage after a charge, but I think in my case they are almost never going to get that length of time to sit without some load being put on them. I would guess that on a non-cruising day (and in winter) the fridge and other things will be left on during the 100-120 minute daily engine run to charge the batteries- and as soon as the engine is turned off, the inverter load from the fridge etc will make itself felt. So this elongated and very gradual decay period wont normally get a chance to happen. There will be a few summer days when I'm away, the solar will pump the batteries up, and there will be almost zero load on them afterwards. But that said, if I'm not there I wont be looking to read the SoC. And if I am there, they will be getting a bit of a hammering, assuming the requisite beer supplies can be procured to provide a thermal challenge for the fridge. If I know that I'm going to be away for a few days in the summer, I'll switch off the fridge and the inverter, and I'll probably disconnect the lithiums to keep them from being kept at a high SoC for several days by the solar charge. In those periods I'll rely on a single lead acid battery (that I'll leave in parallel with them) for the minimal discharging tasks that might be needed when I'm away. So I will need an SOP or checklist of the jobs when I'm leaving the boat for more than 24 hours. Sadly it might now be a few weeks till I get the lithiums properly set up. I've got the BMV700 and the B2B on board, but my electrician is saying that she's no longer allowed to attend a job in this marina unless its an emergency. I have suggested taking the boat to meet her at a nearby bridge so that the job is done on the towpath whilst I am CCing - and is thus fully legal. But she is very busy for the next two weeks. My guess is there is a small chance of her getting a chance to do it on Thurs 28, but most likely it will be the week after that, and maybe 2 weeks after. Given that the original install took 4 weeks to happen, I feel I have to now look at what other options might be available. But marine electricians are ludicrously thin on the ground in these here parts. So there is the option of calling other marine electricians in the area, but I am now starting to give serious thought to the idea of attempting the B2B install myself, if I can get some guidance from the folks on this forum. People like yourself will know instantly which wire should be connected where. What looks like an impenetrable forest of wires to me, will be easily understood by an expert. The earliest opportunity to electrocute myself will come on Thursday and Friday, so if I know you will be around on those days (or others) to look at photos (which hopefully wont include flesh burns), I think I might give it a shot. did you get the bmv 700 or 712 the 712 seems the most useful for me anyway.
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Post by Deleted on Jan 18, 2021 13:10:22 GMT
did you get the bmv 700 or 712 the 712 seems the most useful for me anyway. I went for the BMV700 in the end. I found a new one on eBay for about £120, whereas the BMV712 was close to £200, and I dont really need the extra features it has. The BMV712 would have been nice to have just in case, but if my plan works, I wont need the voltage cutoff/control features of the 712, because my B2B charger will prevent a high-voltage situation from happening, and I'm hoping to use a split charge relay as a low voltage cutoff. After trying to understand the discussions about how to build a high/low voltage cutoff protection system using relays and using the BMV712 as a control system, I decided it was just never going to be feasible for me. I dont even understand a lot of the electrical terminology being used, so trying to follow your example (and perhaps Nicks) was not an option. So I'm hoping that I can use this split charge smart relay as a low-voltage over discharge protection: www.splitcharge.co.uk/product/durite-0-727-43-200a-smart-programmable-relay/The idea of these is to stop a vehicle battery from discharging into a leisure battery when the vehicle battery drops below say 12v, but my plan is to use it on the leisure batteries. I.e. the voltage sensor from the relay will go onto the lithiums, and cut will the output from them when they fall below 12v. It should be a very rare event, but its nice to have a cheap (and simple) protection system in there just in case.
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Post by Telemachus on Jan 18, 2021 13:31:04 GMT
You can use the BMV700 in the same way as the BMV712 to operate a low and high voltage cutoff device, so it still remains an option. The difference is that when the relay of the BMV700 operates, it continues to take a small additional current whereas the BMV712 doesn’t.
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Post by kris on Jan 18, 2021 13:37:20 GMT
You can use the BMV700 in the same way as the BMV712 to operate a low and high voltage cutoff device, so it still remains an option. The difference is that when the relay of the BMV700 operates, it continues to take a small additional current whereas the BMV712 doesn’t. . I didn’t know the 700 did the same thing. Oh well.
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Post by Telemachus on Jan 18, 2021 13:39:56 GMT
You can use the BMV700 in the same way as the BMV712 to operate a low and high voltage cutoff device, so it still remains an option. The difference is that when the relay of the BMV700 operates, it continues to take a small additional current whereas the BMV712 doesn’t. . I didn’t know the 700 did the same thing. Oh well. What the 712 gives over the 700 is: 1/ the ability to monitor voltage of a second battery, or the temperature of the main battery 2/ lower power consumption, in particular when the relay is on 3/ bluetooth interface
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Post by kris on Jan 18, 2021 13:41:34 GMT
did you get the bmv 700 or 712 the 712 seems the most useful for me anyway. I went for the BMV700 in the end. I found a new one on eBay for about £120, whereas the BMV712 was close to £200, and I dont really need the extra features it has. The BMV712 would have been nice to have just in case, but if my plan works, I wont need the voltage cutoff/control features of the 712, because my B2B charger will prevent a high-voltage situation from happening, and I'm hoping to use a split charge relay as a low voltage cutoff. After trying to understand the discussions about how to build a high/low voltage cutoff protection system using relays and using the BMV712 as a control system, I decided it was just never going to be feasible for me. I dont even understand a lot of the electrical terminology being used, so trying to follow your example (and perhaps Nicks) was not an option. So I'm hoping that I can use this split charge smart relay as a low-voltage over discharge protection: www.splitcharge.co.uk/product/durite-0-727-43-200a-smart-programmable-relay/The idea of these is to stop a vehicle battery from discharging into a leisure battery when the vehicle battery drops below say 12v, but my plan is to use it on the leisure batteries. I.e. the voltage sensor from the relay will go onto the lithiums, and cut will the output from them when they fall below 12v. It should be a very rare event, but its nice to have a cheap (and simple) protection system in there just in case. That sounds a bit difficult to programe.
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Post by kris on Jan 18, 2021 13:42:40 GMT
. I didn’t know the 700 did the same thing. Oh well. What the 712 gives over the 700 is: 1/ the ability to monitor voltage of a second battery, or the temperature of the main battery 2/ lower power consumption, in particular when the relay is on 3/ bluetooth interface I’ve got it sat here now, so I’m not much bothered.
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Post by Telemachus on Jan 18, 2021 13:47:03 GMT
What the 712 gives over the 700 is: 1/ the ability to monitor voltage of a second battery, or the temperature of the main battery 2/ lower power consumption, in particular when the relay is on 3/ bluetooth interface I’ve got it sat here now, so I’m not much bothered. If you afford it, I think the modest additional cost of the 712 is worth it just for the lower power consumption “in emergency”. That’s why I bought that one.
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Post by Deleted on Jan 18, 2021 13:55:20 GMT
I went for the BMV700 in the end. I found a new one on eBay for about £120, whereas the BMV712 was close to £200, and I dont really need the extra features it has. The BMV712 would have been nice to have just in case, but if my plan works, I wont need the voltage cutoff/control features of the 712, because my B2B charger will prevent a high-voltage situation from happening, and I'm hoping to use a split charge relay as a low voltage cutoff. After trying to understand the discussions about how to build a high/low voltage cutoff protection system using relays and using the BMV712 as a control system, I decided it was just never going to be feasible for me. I dont even understand a lot of the electrical terminology being used, so trying to follow your example (and perhaps Nicks) was not an option. So I'm hoping that I can use this split charge smart relay as a low-voltage over discharge protection: www.splitcharge.co.uk/product/durite-0-727-43-200a-smart-programmable-relay/The idea of these is to stop a vehicle battery from discharging into a leisure battery when the vehicle battery drops below say 12v, but my plan is to use it on the leisure batteries. I.e. the voltage sensor from the relay will go onto the lithiums, and cut will the output from them when they fall below 12v. It should be a very rare event, but its nice to have a cheap (and simple) protection system in there just in case. That sounds a bit difficult to programe. I have to agree- those are the programming instructions below. It sounds as if it has to be wired up in one way just for the programming phase, and then wired up slightly differently for operational use. When I made an attempt to explain this idea to the electrician on the phone yesterday, she wasn't sure it would work, but tbh I probably explained it badly, so I'm still optimistic. "PROGRAMMING FUNCTION To enter programming mode, the power must be off to terminal 30 and terminal 85 must be connected to ground or -0V. Connect terminal 86 to terminal 30 and then re-connect the power to terminal 30. The LED on the top of the unit will flash a number of times indicating the current programme number (once for 1, twice for 2, Etc.). Remove and replace, within 40 seconds, the connection to terminal 86 and the LED will start to sequence through the programme numbers (once for 1, pause, twice for 2, pause, Etc.). When the number of the programme required is reached remove the connection to terminal 86. The LED will flash the number of times to confirm the programme number selected. If this is OK re-connect terminal 86 and the LED will flash quickly indicating that the setting is saved. (If not OK turn the power off and start again.) Turn the power off. When the power is turned back on the unit will use the last programme set." Seeing all this faff, I'm tempted to ask the electrician if they can put in a circuit or a switch that will enable me to switch from operational mode to programming mode, in case I want to change the low-voltage threshold at some point in the future.
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Post by Deleted on Jan 18, 2021 14:09:27 GMT
I’ve got it sat here now, so I’m not much bothered. If you afford it, I think the modest additional cost of the 712 is worth it just for the lower power consumption “in emergency”. That’s why I bought that one. I have to admit, I was sorely tempted by the bluetooth, thinking how convenient it would be to check the battery status on my phone, but the £70 difference in price swung me against the 712. If someone asked me tomorrow whether in my opinion a high or low voltage cut off was essential to a lithium installation, I'd tell them not really- on the basis that the batteries they buy will almost certainly have a built in BMS to manage the voltage protections. Those are a bit extreme, but then again it will be an extremely rare event, so maybe they can rely on the the built in BMS. For people who dont have a built in BMS and are using an alternator, some sort of protection against high charging voltage is probably required- again just my opinion, having done some limited charging tests and seeing how easy it is to get damagingly high voltages with my existing A2B charger when it reaches the final stage of charging.
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Post by Telemachus on Jan 18, 2021 15:41:03 GMT
If you afford it, I think the modest additional cost of the 712 is worth it just for the lower power consumption “in emergency”. That’s why I bought that one. I have to admit, I was sorely tempted by the bluetooth, thinking how convenient it would be to check the battery status on my phone, but the £70 difference in price swung me against the 712. If someone asked me tomorrow whether in my opinion a high or low voltage cut off was essential to a lithium installation, I'd tell them not really- on the basis that the batteries they buy will almost certainly have a built in BMS to manage the voltage protections. Those are a bit extreme, but then again it will be an extremely rare event, so maybe they can rely on the the built in BMS. For people who dont have a built in BMS and are using an alternator, some sort of protection against high charging voltage is probably required- again just my opinion, having done some limited charging tests and seeing how easy it is to get damagingly high voltages with my existing A2B charger when it reaches the final stage of charging. It’s not quite that simple! Because BMS means different things to different people. As I understand it, your Valence batteries have a BMS with built in balancing and SoC reporting, but with no shut off device in the event of over or under voltage. That is the “middle position”. At the two other ends are bare cells like I have, or a drop in replacement battery such as is sold by Victron or Mastervolt which does have an internal shut off device.
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Post by Telemachus on Jan 18, 2021 15:44:53 GMT
That sounds a bit difficult to programe. I have to agree- those are the programming instructions below. It sounds as if it has to be wired up in one way just for the programming phase, and then wired up slightly differently for operational use. When I made an attempt to explain this idea to the electrician on the phone yesterday, she wasn't sure it would work, but tbh I probably explained it badly, so I'm still optimistic. "PROGRAMMING FUNCTION To enter programming mode, the power must be off to terminal 30 and terminal 85 must be connected to ground or -0V. Connect terminal 86 to terminal 30 and then re-connect the power to terminal 30. The LED on the top of the unit will flash a number of times indicating the current programme number (once for 1, twice for 2, Etc.). Remove and replace, within 40 seconds, the connection to terminal 86 and the LED will start to sequence through the programme numbers (once for 1, pause, twice for 2, pause, Etc.). When the number of the programme required is reached remove the connection to terminal 86. The LED will flash the number of times to confirm the programme number selected. If this is OK re-connect terminal 86 and the LED will flash quickly indicating that the setting is saved. (If not OK turn the power off and start again.) Turn the power off. When the power is turned back on the unit will use the last programme set." Seeing all this faff, I'm tempted to ask the electrician if they can put in a circuit or a switch that will enable me to switch from operational mode to programming mode, in case I want to change the low-voltage threshold at some point in the future. It is a bit of a faff, but something you may only have to do once, or very occasionally. But yes it might be helpful to have a push button or switch wired in to make it easier, it will be very low current so nothing fancy needed.
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Post by Deleted on Jan 18, 2021 19:26:01 GMT
I have to agree- those are the programming instructions below. It sounds as if it has to be wired up in one way just for the programming phase, and then wired up slightly differently for operational use. When I made an attempt to explain this idea to the electrician on the phone yesterday, she wasn't sure it would work, but tbh I probably explained it badly, so I'm still optimistic. "PROGRAMMING FUNCTION To enter programming mode, the power must be off to terminal 30 and terminal 85 must be connected to ground or -0V. Connect terminal 86 to terminal 30 and then re-connect the power to terminal 30. The LED on the top of the unit will flash a number of times indicating the current programme number (once for 1, twice for 2, Etc.). Remove and replace, within 40 seconds, the connection to terminal 86 and the LED will start to sequence through the programme numbers (once for 1, pause, twice for 2, pause, Etc.). When the number of the programme required is reached remove the connection to terminal 86. The LED will flash the number of times to confirm the programme number selected. If this is OK re-connect terminal 86 and the LED will flash quickly indicating that the setting is saved. (If not OK turn the power off and start again.) Turn the power off. When the power is turned back on the unit will use the last programme set." Seeing all this faff, I'm tempted to ask the electrician if they can put in a circuit or a switch that will enable me to switch from operational mode to programming mode, in case I want to change the low-voltage threshold at some point in the future. It is a bit of a faff, but something you may only have to do once, or very occasionally. But yes it might be helpful to have a push button or switch wired in to make it easier, it will be very low current so nothing fancy needed. I'd be very grateful for your thoughts on a related issue: I outlined the relay-based solution to my electrician and she was pessimistic about it. In trying to describe my idea over the phone, I started by saying that in using the relay, I would 'pretend' that the lithiums were the vehicle battery (i.e. the battery that needed to be protected from over-discharging). So I would connect the relay into the wire that carried the output from the lithiums to the inverter. There is a sensor wire that would normally be connected to the battery that is the source of the charge (normally the vehicle battery). So normally, this sensor would monitor the vehicle battery voltage. In my setup, this sensor would instead be connected to an appropriate position on the lithium battery bank. So when the sensor detects the lithium battery voltage has fallen below say 12v, the relay disconnects the output/load that is being taken from the lithiums. When I explained this, the electrician suggested that a further battery would be required after the relay (in other words, between then relay and the inverter). I dont understand why she would have said this, unless I described the relay setup in a confusing way. I'm hoping it is that, because I thought I had a simple and cheap protection against over-discharging, and I dont want to have to go back to the drawing board. I'm pretty sure the batteries will survive without an over discharge cut off (unless I let other people use the boat), and 99% of the time I'll be watching the batteries' SoC manually, but it would be a nice thing to have if it can be done cheaply and simply.
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