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Post by Telemachus on Oct 1, 2020 17:06:02 GMT
I think you could still use it though, by operating it from the BMV relay. You can set the BMV relay to operate both on under voltage and over voltage. Just connect the NO terminal of the BMV relay to the “Remote” connection, and the COM relay terminal to 0v. um that’s worth thinking about. So set the undervoltage on the intelitec and then use the bmv 712 to send it the signal to cutout at over voltage? I might speak with the guy from intelitec again and see what he says, he was very friendly. You could do it that way, or just use the BMV for both over and under voltage. As far as I know you can set both a high voltage limit and a low voltage limit at the same time, and the relay will operate if either the high or the low threshold is exceeded. You can also set a low SoC limit to operate the relay.
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Post by kris on Oct 1, 2020 17:57:00 GMT
um that’s worth thinking about. So set the undervoltage on the intelitec and then use the bmv 712 to send it the signal to cutout at over voltage? I might speak with the guy from intelitec again and see what he says, he was very friendly. You could do it that way, or just use the BMV for both over and under voltage. As far as I know you can set both a high voltage limit and a low voltage limit at the same time, and the relay will operate if either the high or the low threshold is exceeded. You can also set a low SoC limit to operate the relay. That sounds interesting, as I definitely need an automatic cut out I wouldnt trust myself like John when I’ve next got chance I’ll phone the company and see if he thinks it would be okay. Makes it a bloody expensive relay though. But it definitely seems like a solution, thanks nick. How are you getting on with yours?
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Post by Telemachus on Oct 1, 2020 19:30:23 GMT
You could do it that way, or just use the BMV for both over and under voltage. As far as I know you can set both a high voltage limit and a low voltage limit at the same time, and the relay will operate if either the high or the low threshold is exceeded. You can also set a low SoC limit to operate the relay. That sounds interesting, as I definitely need an automatic cut out I wouldnt trust myself like John when I’ve next got chance I’ll phone the company and see if he thinks it would be okay. Makes it a bloody expensive relay though. But it definitely seems like a solution, thanks nick. How are you getting on with yours? Gliding this week and next, and Jeff is waiting for an appointment to have an impacted wisdom tooth and cyst cut out, so not quite sure when we’re going to be down next. I’ve got plenty of software development to do first, anyway.
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Post by patty on Oct 1, 2020 19:38:59 GMT
That sounds interesting, as I definitely need an automatic cut out I wouldnt trust myself like John when I’ve next got chance I’ll phone the company and see if he thinks it would be okay. Makes it a bloody expensive relay though. But it definitely seems like a solution, thanks nick. How are you getting on with yours? Gliding this week and next, and Jeff is waiting for an appointment to have an impacted wisdom tooth and cyst cut out, so not quite sure when we’re going to be down next. I’ve got plenty of software development to do first, anyway. R u allowed to come down? We r trapped here.
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Post by Telemachus on Oct 1, 2020 20:31:34 GMT
Gliding this week and next, and Jeff is waiting for an appointment to have an impacted wisdom tooth and cyst cut out, so not quite sure when we’re going to be down next. I’ve got plenty of software development to do first, anyway. R u allowed to come down? We r trapped here. Yes at the moment we are. Both Aberdeen and Tamworth don't have any additional restrictions for now. Things could change, of course!
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Post by peterboat on Oct 1, 2020 23:17:33 GMT
Like John I dont monitor my batteries anymore, solar charges them, occasionally I fire up the whispergen but with the amount of solar on the roof its not needed. I havent bothered with over undercharge cutoffs all though like John I have one, the whispergen is set up for under voltage batteries but as yet hasnt ever come on. I cant remember the last time I connected the puter to them. I have four Valences in my electric truck charged by solar as well, it works well and clocks up 50 to 100 miles a week, the batteries are connected together by their leads and according to the truck software well in balance. I stick rigidly to the 20 80% SOC and expect the batteries to outlive me. As I type my batteries are at 26.6 volts so all is well on the boat, the drive bank is at 79.3 volts its nominally 72 volts so well within the 20 to 80%, I dont expect to charge them before spring next year ready for a spring cruise unless we get some good winter weather to tempt us out
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Post by kris on Oct 2, 2020 5:55:52 GMT
Just to be clear peter by 80 20 you mean you don’t charge them over 80% and don’t drain them less than 20%? Personally I’d like to have a cutout to protect what is a major investment. I’d like them to outlive me as well, but I’m a little bit younger than yourself.
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Post by JohnV on Oct 2, 2020 6:13:39 GMT
Like Kris I have sh Mastervolts from James. I thought you had Valence batteries John. brain fart
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Post by peterboat on Oct 3, 2020 9:50:06 GMT
Just to be clear peter by 80 20 you mean you don’t charge them over 80% and don’t drain them less than 20%? Personally I’d like to have a cutout to protect what is a major investment. I’d like them to outlive me as well, but I’m a little bit younger than yourself. Not bothered Kris I have 30 batteries on drive and six on domestic the drive batteries arrived in a state of discharge and recovered with a charge, BMSs all flashing green, the drive batteries are disconnected at the moment and all solar is onto the domestic batteries, if something goes wrong the whispergen will fire up to charge them up so no issue really is their?
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Post by kris on Oct 3, 2020 10:55:14 GMT
I think you might have misunderstood what I’ve posted peter. I wasn’t saying there was “an issue.” I was asking you about your charging and discharging practices? Also saying that my preference is to have an automatic cutout.
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Post by kris on Oct 7, 2020 12:38:49 GMT
Doh your right nick, thanks for that. It must be hard to be so clever? I’ve let James know as well, as he was going to bye one after frying one of the victron ones because they are not bi directional. Typical just when you think youve found a solution. I think you could still use it though, by operating it from the BMV relay. You can set the BMV relay to operate both on under voltage and over voltage. Just connect the NO terminal of the BMV relay to the “Remote” connection, and the COM relay terminal to 0v. I’ve spoken with technical support for the Bgb relay. It was the first time he had ever seen one and was reading from the manual. At first when I asked him if it would work as you suggest Nick, he said yes. When I mentioned an inverter he backed off and said it wasn’t suitable because of it using “fet” technology. To be honest I think he was being cautious because of the uncertainty in his voice I could tell he didn’t really know and it was just safer to say it wasn’t suitable. I just wanted to see what you thought about it.
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Post by Telemachus on Oct 7, 2020 20:39:18 GMT
OK I didn't realise it was an electronic switching device. FETs, or more accurately MOSFETs, are electronic devices (transistors, really) that can be used to switch currents on and off. No moving parts, as opposed to a relay such as the Tyco BDS-A with mechanical switch contacts. I suppose one issue is that an inverter typically has a large bank of capacitors connected across the 12v input to smooth the power demand. When the inverter has been disconnected for a while, these capacitors discharge. And so when you reconnect, there is a massive surge current as the capacitors initially presents as a near dead short circuit, until they charge. It will only take a few milliseconds to charge the capacitors, and this doesn't present a problem for a mechanical switch, but the semiconductor juntion on a power MOSFET is very small and thus in the event of an overload, even of a very short duration such as a few milliseconds, can overheat and melt.
The device datasheet mentions a peak current of 1500A, which sounds a lot, but probably the initial current into an inverter is more than that. But one could probably cater for that by ensuring that the resistance of the wiring is sufficient to keep the transient current below 1500A. That would be 0.009 ohms. 0.009 ohms would drop 1.8v at 200A (2 kw from the inverter) which is rather a lot, but perhaps if you had a smaller inverter and/or didn't intend to take much out of the inverter, it would be less.
Another consideration is that in the event of a short circuit somewhere, even though the circuit is fused, it takes a while (relatively) for the fuse to melt and in the mean time, the semiconductor junction of this device can melt as it has less thermal mass.
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Post by Deleted on Oct 7, 2020 21:00:46 GMT
I remember doing the metal oxide semiconductor field effect transistors during my brief time at Loughborough reading "electrical and electronic engineering" advertised in the brochure as "renewable energy systems engineering". The former was much too boring. I would have been happy to be studying the latter though. Doping and silicon? I'd rather go boating !
1500 amps as an inverter startup current does seem slightly extreme but
Probably good not to have been dragged into the nonsense corporate bollocks anyway.
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Post by kris on Oct 8, 2020 7:37:22 GMT
OK I didn't realise it was an electronic switching device. FETs, or more accurately MOSFETs, are electronic devices (transistors, really) that can be used to switch currents on and off. No moving parts, as opposed to a relay such as the Tyco BDS-A with mechanical switch contacts. I suppose one issue is that an inverter typically has a large bank of capacitors connected across the 12v input to smooth the power demand. When the inverter has been disconnected for a while, these capacitors discharge. And so when you reconnect, there is a massive surge current as the capacitors initially presents as a near dead short circuit, until they charge. It will only take a few milliseconds to charge the capacitors, and this doesn't present a problem for a mechanical switch, but the semiconductor juntion on a power MOSFET is very small and thus in the event of an overload, even of a very short duration such as a few milliseconds, can overheat and melt.
The device datasheet mentions a peak current of 1500A, which sounds a lot, but probably the initial current into an inverter is more than that. But one could probably cater for that by ensuring that the resistance of the wiring is sufficient to keep the transient current below 1500A. That would be 0.009 ohms. 0.009 ohms would drop 1.8v at 200A (2 kw from the inverter) which is rather a lot, but perhaps if you had a smaller inverter and/or didn't intend to take much out of the inverter, it would be less.
Another consideration is that in the event of a short circuit somewhere, even though the circuit is fused, it takes a while (relatively) for the fuse to melt and in the mean time, the semiconductor junction of this device can melt as it has less thermal mass.
so no good for the job then? Oh well.
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Post by JohnV on Oct 8, 2020 8:32:39 GMT
Another consideration is that in the event of a short circuit somewhere, even though the circuit is fused, it takes a while (relatively) for the fuse to melt and in the mean time, the semiconductor junction of this device can melt as it has less thermal mass.
fast enough fuses are available !!! the downside is that they cost more than the unit you are protecting
(Hit that wall years ago when working in a development lab)
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