Seeking Normally Closed Latching Contactor and Q&A about balancing my Li Ion battery bank

Wondering is anyone is using latching contactors in their system design for High and low voltage cutoff (HVD/LVD). I'm shopping for a 12vdc normally closed, latching contactor. So, the contactor is normally conducting, but if 12v is applied to the terminals it latches open, regardless of if that 12 volts goes away.
You don't seem to find these babies on any street corner.
Please Note: This tread has evolved. LostinSpace has asked that this note be placed here--Lots of evolution of thoughts and ideas during debugging and use of system. -Bill B Moderator
You don't seem to find these babies on any street corner.
Please Note: This tread has evolved. LostinSpace has asked that this note be placed here--Lots of evolution of thoughts and ideas during debugging and use of system. -Bill B Moderator
UPDATE: This thread started off as a search for a normally closed contactor that would draw power only to switch state when a trigger even occurred. However, a member (@karrak) after seeing a photo of my array suggested a way the pack could be configured more efficiently. In doing so I uncovered a major problem wherein the cells of the pack were not staying balanced... in spite of thorough attempts to do so. The majority of this thread is the process of discovering why the pack wouldn't balance.
LostinSpace April 4th, 2018
Qty 24 Sharp 153W poly panels, Midnite MNPV6 combiner, Magnum
MS-4448-PAE inverter with RC50 remote, Magnum MMP Mini panel, Midnite
Classic 150 charge controller, Qty 32 LiFePO4 72AH cells in 2 string 48V
array. BMS.
Comments
19 SW285 panels
SE5000 inverter
grid tied
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
mike_s, Mouser, of course. I can't tell from the data sheet if the contacts are normally closed. The unit seems to use two coils. Do you happen to know for a fact that it is mechanically latching? But no worries. I will contact Mouser. Thank you!
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
http://www.ametekswitch.com/products/DC-Contactors-List.aspx
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
http://www.evwest.com/catalog/product_info.php?products_id=162
https://www.bluesea.com/products/category/20/95/Solenoids/ML-Solenoids
-Bill
mike_s, Sweet. That's the baby I want then.
BB., That one looks like it would fit the bill too. Now it's just a question of price as to which one I will try out.
I like this forum. My biggest fear about posing such questions in forums is that someone will respond with the dreaded "What are you trying to do?" You know what I mean? Because if you answer that question the post turns into people critiquing your approach, and you never get your question answered. :<
So thank you.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
> Solray, yes, I suppose so, although that's a bit over my head so would be a Plan B. ;>
>
> mike_s, Sweet. That's the baby I want then.
>
> BB., That one looks like it would fit the bill too. Now it's just a question of price as to which one I will try out.
>
> I like this forum. My biggest fear about posing such questions in forums is that someone will respond with the dreaded "What are you trying to do?" You know what I mean? Because if you answer that question the post turns into people critiquing your approach, and you never get your question answered. :<
>
> So thank you.
You are very welcome. We are always happy to share a point of view or an option you might have overlooked. It's always beneficial to get more sets of eyes on the problem with different perspectives and specialties rather than just an echo chamber where everyone says the same thing.
We do have a few here that always answer everything the same way, your question cannot be answered because I don't know everything about your life history. Lol
If you really want a latching relay, YM tech makes a line of them. See: http://www.goodymt.com/pdf/LatchRelay.pdf#page=24 for a 150 amp version.
BTW when you are talking about latching relays there's no such thing as "normally closed" - they stay where you put them, so there's no "normally."
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
And so far the LVD on the Magnum has not triggered when the freezer comes in. Naturally this is a subjective comment as I don't know how the magnum will behave with multiple loads PLUS borderline pack voltage. It might be interesting to see if the Magnum has a cutout buffer.
Same on the high side. In this case the charge controller is keeping the lid on pack voltage. It's floating the cells at around 3.3v. Does the cc need a backup? I just came across a thread on the Midnite forums where a guy had a rare failure of a Classic 150 whereby the cc allowed unregulated panel voltage to get to the pack. The battery voltage was raised sky high to the panel voltage and the Calb cells were bulging when he discovered the fault. If a HVD had been set at, what, 3.65-3.7v per cell, perhaps such a disaster would have been avoided.
As you can see by my signature our systems are very similar. I choose to use a JDL-404 also. I have HVD and LVD contactors on a 12AH battery with tender. I also used a piezoelectric alarm. Been up and running 14 months and have had no high or low shutdown. Glad to see you're using LFP.
I mounted the JDL-404 in the front panel of the inverter. (photo below)
Good luck with your system,
Rick
I am available for custom hardware/firmware development
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
If your inverter had a remote on/off switch input you could use that instead of the relay. I had a look at the manual and couldn't find anything. It would be slightly more complex but you could hook a small relay across the on/off switch on the front of the inverter and pulse it to simulate pressing the on/off switch. To make sure that it had indeed turned off you should probably monitor the current to see if it drops to nearly zero to make sure that the inverter has turned off.
On my LFP battery I haven't bothered having a relay to disconnect the inverter. My reasoning is that I will have to be around using the power to drain the battery so will hear an audible alarm. If I am away from home and if my solar controller fails, all the equipment left running will take around a week to flatten the battery and I can monitor the battery SOC remotely via the Internet on my phone.
For the charge controller cutoff, you are better off disconnecting the solar panels from the controller rather than the controller from the battery. You could use a smaller Solid State Relay to do this. In the classic manual they mention that there is an internal relay to disconnect the panels at night. If this is the case I would think that if the classic detected a fault that it could disconnect the panels via the internal relay. Would be good if Midnite made it possible to switch this relay off remotely. Might be worth a phone call to them to discuss this.
I agree with Raj, that it is a good idea to have some sort of audible alarm as well.
Your signature mentions a BMS, do you have any details on what BMS your battery has connected to it?
Simon
32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
modified BMS based on TI bq769x0 cell monitors.
Homemade overall system monitoring and power management https://github.com/simat/BatteryMonitor
I agree - I did this and it worked well (arduino controlling the inverter).
Nice price on the DD60D200 200A DC SSR (if it holds up under use).
I am available for custom hardware/firmware development
http://canada.ul.com/safetyalerts/ul-warns-of-solid-state-relay-with-counterfeit-ul-recognition-mark-release-13pn-52/
http://www.instructables.com/id/The-inner-workings-of-Counterfeit-FOTEK-SSRs/
Also, (it appears) that many of the counterfeit SSRs failed shorted (on). Not a good thing for your application.
-Bill
PS: I should also add that SSRs (in general) need to be well heat sinked. They run much hotter than a typical mechanical relay.
-Bill
Thanks for this input Karrak. Ideally I would like to employ one mechanism to disconnect the batteries, so a cutoff that literally breaks the cable connection from the batteries seems the simplest and most assured approach. Unless you know of some compelling reason to not have solar juice entering the cc if it is powered off??
On the audible, I've ordered a celllog 8, which has one built in.
On the BMS, I would be happy to message you privately with what I'm using, but I'm concerned that mentioning anything to do with battery management here will take the thread off topic. :>
Let me ask you, is that HVD/LVD contactor a normally open device, using 12v juice to keep the contacts closed?