I formulated my question poorly. Please dont take offense, but in the last 4 months of my learning process I have learned that the devil is in the details. What I should have asked is this: Can you, through personal experience, verify that this Chargery BMS, if set to a low voltage cutoff, say 2.8 v, actually cuts off the discharge once the first cell hits this low voltage. Again, no offense intended, just trying to get down to solid facts. Thanks for your patience.
Chargery BMS now with Low Temp Cutoff
- Thread starter Steve_S
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Thank you very much for this personal experience. I am concluding that the products from this Chargery company are very impressive.
I can confirm the same result
grizzzman
Photon Vampire
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It’s passive
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Well, TBH there has been a lot of 'banter' about shunts, their ratings and accuracies etc... I like the Deltec's, it's also what Midnite Solar uses for their sensing component (WizbangJr) and I find them to be quite accurate and they are all properly calibrated at the factory. It's my personal choice to use these. The specs for Chargery say no more that 75mv and I imagine their shunts are fine for the intended use (as long as they get affixed to something to prevent them from moving around at all.
You should be fine using this 100mV/200A shunt to measure currents up to 150A, because I this case the shunt voltage measured by the BMS will not go passed 75mA. If the shunt voltage measurement circuit of the Chargery BMS is capped at 75mV then going beyond this value exposes you to misreading of the current and possibly damage, although it's likely it can handle a bit of overvoltage.
Can anyone explain in general terms what the significance of the mV rating of a shunt is, what determines the proper value, what the pros/cons of higher or lower values are?
I posted something like that here: https://diysolarforum.com/threads/need-smart-bms-as-replacement-for-shunbin-pack.2046/post-40824
If something is unclear or looks wrong please tell
I posted something like that here: https://diysolarforum.com/threads/need-smart-bms-as-replacement-for-shunbin-pack.2046/post-40824
If something is unclear or looks wrong please tell
Thanks for the link, I'll read up on it!
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Solarfun4jim
Solar seduced :-)
So, it 'maybe capped' at 75mV....thanks, that makes sense. Since i'll only be pushing 100A max peaks, the 100mV version should only need function to the 50mV level peak in my case though to cover the 100A load.
Thanks
ps although the wording in the spec was 'suggested' but you dont know if that just the chinglish?
ie "Please use correct current shunt according to actual maximal charge and discharge current, singe shunt is
enough for BMS16T, 75mV or less shunt is suggested. BMS16T can detect charge and discharge current by same
shunt. "
Think i will send jason@ chargery a mail to see if it can be hooked up to a 100mV shunt and recalibrated(just for reference).
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Thanks for all the excellent information on the Chargery BMS. I have watched the vids and read the manual from chargery. Non of this material mentions how a solar charge controller works with the Chargery BMS. How is such a solar charge controller connected to the Chargery BMS? What happens when the BMS determines the battery is full and charging needs to stop? How does the Chargery BMS communicate a stop charging message to the solar charge controller? In other words, what are the physical connections between SCC and BMS, what are the logical messages between them, and what happens when BMS deterimes the battery is full? Has anyone actually made this connection and tested it out?
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
No BMS directly interfaces with an SCC, it's not their job to do that. Their job is to manage the pack and cells within it. Most SCC will just dump the load off when batteries hit full, now many can have a relay activated diversion allowing you to take the extra juice and put it to use like a hot water heater or something else. Just like with Lead Batteries, they can be charging along at 75A and when they hit full and can no longer take charge, the SCC dumps it off (usually as heat) There is no BMS or anything to tell the SCC the batts are full, no need. SCC's see "Ending Amps" which when a battery pack / bank stars to get full it can only take so many amps in and once that drops threshold the SCC burns off the excess by default. That is why SCC's get so hot, that they need cooling fans and / or large cooling heat sinks (as seen on Tristar, some EPEver and others for example).
TBH, I the to see good power dumped when it could be used for something, as bad as throwing out good food ! just wrong IMO.
The Chargery can send a signal when it is full, usually to a dedicated charger unit or to an Inverter/Charger that can accept the signal (not all do). This same signal could also be used to trigger a relay for dumping incoming solar power. The kicker is, with multiple BMS's there would be no arbitrator as such, so this is where doing some programming on RaspberryPi or similar could manage that data signal coming from BMS' and then delegate the action to be taken.
TBH, I the to see good power dumped when it could be used for something, as bad as throwing out good food ! just wrong IMO.
The Chargery can send a signal when it is full, usually to a dedicated charger unit or to an Inverter/Charger that can accept the signal (not all do). This same signal could also be used to trigger a relay for dumping incoming solar power. The kicker is, with multiple BMS's there would be no arbitrator as such, so this is where doing some programming on RaspberryPi or similar could manage that data signal coming from BMS' and then delegate the action to be taken.
Thanks so much for this clarification. So a SCC is connected directly to the battery thus bypassing the BMS entirely?
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Solarfun4jim
Solar seduced :-)
Steve, on the DC switch, could you run position 1 through a 470ohm resistor, to pre charge the caps, then after 5 seconds say, move to full power on position 2 for example?NO not at all.... The BMS is the "agent" in between.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Sure, I suppose that could be done, hang a preloading battery like an AGM or something on Pos 2 with the main power bank on Pos 1 but "in-vehicle" the switch with AFD would be more prudent.
Let me disagree here. The BMS is here to allow or forbid charge and/or discharge. You can do it the hard way with relays, this way you physically open the circuit and you are sure that no current can flow anymore. But you can also use the function of many inverters, chargers and SCC that have inputs to control whether they are allowed to charge or discharge the battery. Nearly all Victron equipments (inverter/chargers, MPPTs etc...) have that for instance. They have 2-wire inputs that are "on" when the contact between the two wires is closed and "off" when the contact is open. Using an optocoupler as in one of the latest videos from Will, you can use the Chargery outputs that are initally supposed to drive relays to control the inputs of the inverter/charger/SCC and forbid or allow charge. Then everything is about how much you trust your equipment and whether you would trust more a relay than direct control of the chargers/loads (both have weaknesses I would say).
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