low voltage battery cutoff options

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mufaddalk
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low voltage battery cutoff options

Post by mufaddalk »

Hi, i have a PIP5048GK inverter running my 48v lifepo4 battery cells.

I have set my standby voltage to 51V and back to battery discharge at 52V. I could set my standby (back to grid) voltage to 50V, however i am aware that this inverter keeps on draining the battery even on standy. this setup has worked for me most of the time. unfortunately twice (once a month back and second time was yesterday) early morning i checked my HA notification, my battery was down to 46V at about 8am, it was raining most of previous day and the inverter went on standby around 7pm last night.

I am concerned about the life of my battery, i have noticed this twice, it might have happened more times. i am looking at options to prevent this from happening in the future.

1. I have been looking online for a relay (100A) with low voltage cutoff of 48V, or a similar device. I have found low voltage dual battery isolater (https://www.australiandirect.com.au/Bat ... gers/KAVSR) they are meant for a different purpose, do you think i can make it work for what i want to achieve. if anyone know of any of similar ideas let me know
2. I have create a small app that reads the inverter data and send it to HA via MQTT (link to the app below). is there an interface command that i can send to the inverter that will turn it off rather then standby. I have an auto transfer switch connected after the inverter, so if there is no power from inverter, it will switch to grid automatically.

https://github.com/oxynic/Inverter.homeassistant.MQTT - to send inverter data to HA via MQTT

Thanks for your help,
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coulomb
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Re: low voltage battery cutoff options

Post by coulomb »

mufaddalk wrote: Sat, 18 Jul 2020, 10:13 is there an interface command that i can send to the inverter that will turn it off rather then standby.
No, not even with fully patched firmware.

To turn if off completely, you need to turn the switch off (normally closed relay contacts in series? But it might be different for the remote display models). And also, remove all charging sources (PV and AC-in).
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
dRdoS7
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Re: low voltage battery cutoff options

Post by dRdoS7 »

Hi,

I've used 2 of these:

https://www.ebay.com.au/itm/LAWN-MOWER- ... ctupt=true

Mine came from ABR, I used them to swap some cells in and out of the battery bank of 40 NiFe cells. Depending on bank voltage, the inverter was connected to either 35 or 40 of the cells. Used them for a couple of years until I bought a 5048MG.

Also used 2 of these:

https://www.ebay.com.au/itm/SSR-100-DD- ... Sw~c1dQDgM

Used to switch AGMs in and out of running parallel with the NiFes. Had to use 2 in series, output to output or input to input (can't remember which), to prevent current backflow. They were used to smooth the transition between 35 or 40 cells. The AGMs were almost stuffed and only lasted a little while longer. Then I found the switching was quick enough not to need then anyway. :roll:

I don't know if they'll be suitable for your service though. Might be OK as you're not expecting to have any large current flowing because the inverter will be in standby mode.

That 12V isolator probably won't work because your voltage, hopefully, will never drop that low. Plus, 48V will likely kill it. :shock:

Another option, which I didn't try, is to use a 500A winch solenoid:

https://www.ebay.com.au/itm/I-MAX-12V-D ... ctupt=true

I had thought of using 1, instead of the 2 I had, but I wasn't sure if my thinking was correct.

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Re: low voltage battery cutoff options

Post by dRdoS7 »

Hi,

Just re-read your original post (raining here in Brisbane, our daughter is at work, and our grand-son is at school).

I missed that you have an ATS.

Using the 12V VSR: I think you could, if it's ground/-ve is placed 4 cells away so it sees the correct voltage. That is maybe what you had planned.

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mufaddalk
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Re: low voltage battery cutoff options

Post by mufaddalk »

thanks @dRdoS7 for your suggestions.

I typed my original thread in a hurry, I was looking at the 12V 120a low voltage cutoff relay at that stage. in hindsight that might not be ideal as you mentioned in your reply. I have since been looking at 48v 100a+ LVD relays and they are none to be seen. I would have thought they would be one available or something similar, i am surprised there aren't any. best i found was 48V 30A ones on ebay and i was thinking of putting 3 in parallel.

Re your Solid state relay link on your post (https://www.ebay.com.au/itm/SSR-100-DD- ... Sw~c1dQDgM), i can use that between my battery and inverter, what did you use to control i.e. connect / disconnect the relay. perhaps i can use the 48V 30A LVD mentioned above to control this 100A relay?

Thanks
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Re: low voltage battery cutoff options

Post by paulvk »

Look for Albright contactor 48v on ebay they go up to 500 amp I have a few from old telco gear
and Element14 https://au.element14.com/albright-engin ... t=albright
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Re: low voltage battery cutoff options

Post by dRdoS7 »

Hi,
mufaddalk wrote: Sat, 25 Jul 2020, 14:37 Re your Solid state relay link on your post (https://www.ebay.com.au/itm/SSR-100-DD- ... Sw~c1dQDgM), i can use that between my battery and inverter, what did you use to control i.e. connect / disconnect the relay. perhaps i can use the 48V 30A LVD mentioned above to control this 100A relay?
I can't find the controllers I bought on ebay. Allowed setting upper & lower voltage setpoints, offsets, time delay, and a small amount of voltage reading calibration. It measured 0-100V DC and 8-30V power supply (IIRC). Not home, so can't check anything.

They are in a nice plastic surface mount case, with an LED display, 2 buttons to alter/read settings. Terminals for power supply, measurement, and control (no/nc). The -ve is common for power and measurement. If you can find one, good luck deciphering the instructions!

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mufaddalk
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Re: low voltage battery cutoff options

Post by mufaddalk »

thanks @dRdoS7 , i will try to find that controller.

I did some more testing, i found that on Line mode the inverter drains 200W from the battery, this is the issue as its practically draining the battery from its lowest point.

The good news is that on standby it only drains 2W from the battery. I will try to investigate if there is a command i can set to change it to standby at night when its on line mode, i should be able to automate provided there is a command i can use. If i can achieve this, this would be my preferred option.
mufaddalk
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Re: low voltage battery cutoff options

Post by mufaddalk »

paulvk wrote: Sat, 25 Jul 2020, 22:10 Look for Albright contactor 48v on ebay they go up to 500 amp I have a few from old telco gear
and Element14 https://au.element14.com/albright-engin ... t=albright
thanks @paulvk , unfortunately i am looking for a Low voltage cutoff device, not just a relay. Or maybe i can use the relay if i can find a controller that will be able to measure the voltage and trigger cutoff.
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Re: low voltage battery cutoff options

Post by paulvk »

mufaddalk wrote: Sun, 26 Jul 2020, 07:25 thanks @paulvk , unfortunately i am looking for a Low voltage cutoff device, not just a relay. Or maybe i can use the relay if i can find a controller that will be able to measure the voltage and trigger cutoff.
In that case then go to e-bay look for "Wireless Voltmeter Ammeter" and you will find a combined meter
that does amps (versions up to 500A) , volts , capacity , temperature , uses a hall detector for amps
It has high volts, low volts , over current cut off relay outputs.
Note the one with temp sensor is the better stable one
I replaced the NRF24 wireless modules for long range ones off e-bay and get good range through
multiple walls over 30 meters , its best to do the programming close by or on a bench to set voltages.
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brendon_m
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Re: low voltage battery cutoff options

Post by brendon_m »

I have a couple of those meters and they work well, although I have blown a few up (my own fault) but one I had just started giving funny readings after a power cycle (reading 400+V on a 48V battery). I assume it took a spike and died and another one I had never read right out of the box (but in that case the box looked like it was dragged from China to my house).
All in all I find them to be quite versatile and accurate, especially for the price.
They're about $70 off ebay, banggood, aliexpress etc.
Being able to read up to 500A and 500V makes them especially good for EVs as long as you isolate the power supply as the voltage sense, power supply and usb (usb is only a power supply, no data) grounds are all linked.
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Re: low voltage battery cutoff options

Post by paulvk »

Here is a picture of one I have put the readout in a box with high power NRF-24 and small switch mode supply.
Note this is the one without temp sensor do not get this one, the one with temp sensor has two digits both sides
of the decimal point for volts and a temp reading below the 38:37 in my picture.
The OFF in my picture is the relay indicator.
box from jaycar HB6075
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Cowardlyduck
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Re: low voltage battery cutoff options

Post by Cowardlyduck »

I'm building a powerwall atm and like the look of this meter a lot.
Image
My BMS has bluetooth, but the range isn't great and for the most part the useful info it provides is the same as this plus I would like to have the option of displaying it on the case.

Does the WiFi connect to an app or present a web page, or is it just for programming?

Cheers
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brendon_m
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Re: low voltage battery cutoff options

Post by brendon_m »

The "wifi" is just a wireless link between the display and the measuring module. The display is powered by a usb port. You can change the address to 50? different address so you can have multiple units running in close proximity. Also if you put 2 modules and 1 display on the same address channel, the display will cycle between the 2 modules every second
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Re: low voltage battery cutoff options

Post by paulvk »

No the meter is not wifi (this would have been superb) its wireless with NRF-24 modules
the USB cable between the modules is just for 5V power its not USB but does let
you run the display off any USB power , computer , laptop
If you put an antenna on top of your diy power wall you can put the display
anywhere you want , in the kitchen , in the lounge room or make it portable
just needs 5 volts and the long range NRF-24 modules come with SMA connector
you buy these off e-bay to replace the short range ones that come with
the meter they just plug in.
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mufaddalk
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Re: low voltage battery cutoff options

Post by mufaddalk »

paulvk wrote: Sun, 26 Jul 2020, 08:52 In that case then go to e-bay look for "Wireless Voltmeter Ammeter" and you will find a combined meter
that does amps (versions up to 500A) , volts , capacity , temperature , uses a hall detector for amps
It has high volts, low volts , over current cut off relay outputs.
Note the one with temp sensor is the better stable one
I replaced the NRF24 wireless modules for long range ones off e-bay and get good range through
multiple walls over 30 meters , its best to do the programming close by or on a bench to set voltages.
Thanks @paulvk , this is good for displaying voltage, current, etc. It still not what i want, I am looking for a low voltage cutoff, something that i can use between the battery and inverter or connect to a relay to cutoff when the battery voltage drops to a certain value. currently i have the inverter connected to homeassistant and i can view the voltage, current, and other stats anytime on my phone.
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Re: low voltage battery cutoff options

Post by paulvk »

mufaddalk wrote: Mon, 27 Jul 2020, 07:41 I am looking for a low voltage cutoff, something that i can use between the battery and inverter or connect to a relay to cutoff when the battery voltage drops to a certain value.
Yes it has this!
Low and high voltage relay output
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