need a good low voltage cut off for my LFP battery

[bluefox140]

I currently have 24@522AH and adding 24v 200AH. will have total around 700AH of LFP battery. my battery doesn't last all night . it will reach the auto low voltage cut off from the BMS around 5am that's why I am adding additional 200AH to it. I watched all will,s YouTube videos . one of his videos he mention best way to extend LFP battery life is to cut off around 20% to 25% and charge only up to 80%. what's a good product that I can add into my system so it will auto cut off around 20%. I don't want to fully discharged my battery so it will shorten their lives.

 

[Dzl]

An inverter with a programmble low voltage disconnect for AC loads + a Victron Battery protect for DC loads would allow you to achieve this using voltage based cutoff points. Alternatively, if your inverter doesn't have programmable LVD, or you would prefer the battery protect to control everything, you can use the battery protect to switch some inverters indirectly. Adding a BMV into the system may enable SOC based cutoffs (I believe I heard this but am not positive). @smoothJoey may know of some alternatives to the battery protect if it doesn't meet your needs for one reason or another.

 

[bluefox140]

I have this inverter. it doesn't have adjustable low voltage cutoff

 

[Dzl]

It may be possible to use the battery protect to remotely switch the inverter on/off. It cannot be used in the direct current path, but you may be able to use the remote ports to switch the inverter, but it would take a little DIY-ing. I don't know the specifics of how to accomplish this or if your inverter is able to be controlled this way (if it can be done with Sigineer or AIMS, it should work with yours).

 

[bluefox140]

It may be possible to use the battery protect to remotely switch the inverter on/off. It cannot be used in the direct current path, but you may be able to use the remote ports to switch the inverter, but it would take a little DIY-ing. I don't know the specifics of how to accomplish this or if your inverter is able to be controlled this way (if it can be done with Sigineer or AIMS, it should work with yours).

will look it up. thanks

 

[Zil]

I only know of one LVD that the manufacture recommends for use with an inverter. It is Battery Guard by Samlex. I have BG-200. I have only one complaint, The stud for battery side of device is a bit short. I asked Samlex, but they never answered my questions. https://www.samlexamerica.com/products/ProductDetail.aspx?pid=27

 

[bluefox140]

I only know of one LVD that the manufacture recommends for use with an inverter. It is Battery Guard by Samlex. I have BG-200. I have only one complaint, The stud for battery side of device is a bit short. I asked Samlex, but they never answered my questions. https://www.samlexamerica.com/products/ProductDetail.aspx?pid=27

no good bad reviews

 

[Zil]

Where did you see bad reviews? I replaced the first one I purchased. Same complaint of short terminal. But device does what it claimed to do and does it well. I had to use Flared starter lugs on the cable. Instead of heavy duty lugs.

 

[bluefox140]

Where did you see bad reviews? I replaced the first one I purchased. Same complaint of short terminal. But device does what it claimed to do and does it well. I had to use Flared starter lugs on the cable. Instead of heavy duty lugs.

on Amazon

 

[Zil]

Funny. Only saw one bad review and two 5 star reviews on Amazon. But mine works as described.

 

[MrNatural22]

on Amazon

Take Amazon reviews with a grain of salt as they say. Amazon reviews contain a lot of BS and bogus answers.
People give sometimes totally irrelevant and really dumb answers to questions looking for some sort of needy attention.

 

[mr_ed]

I've had the same issue with no programmable low voltage disconnect on my inverter. My plan (have all the parts but haven't gotten around to doing it yet) is to do the following:
- Connect a cheap (about $5 on ebay) low voltage disconnect board direct to the battery;
- Connect a tiny relay (very low current draw) to the board, so that the relay is only closed if voltage is above the set cut-off voltage;
- Cut the line on the remote inverter switch and run it through the relay;
- Only use the remote inverter switch (i.e. don't use the switch on the inverter, as it would bypass this system).

With the above, the inverter should be shut off when the low voltage board cuts the power to the relay. Obviously this solution only works if you have a remote switch on your inverter.

 

[bluefox140]

I've had the same issue with no programmable low voltage disconnect on my inverter. My plan (have all the parts but haven't gotten around to doing it yet) is to do the following:
- Connect a cheap (about $5 on ebay) low voltage disconnect board direct to the battery;
- Connect a tiny relay (very low current draw) to the board, so that the relay is only closed if voltage is above the set cut-off voltage;
- Cut the line on the remote inverter switch and run it through the relay;
- Only use the remote inverter switch (i.e. don't use the switch on the inverter, as it would bypass this system).

With the above, the inverter should be shut off when the low voltage board cuts the power to the relay. Obviously this solution only works if you have a remote switch on your inverter.

yes I do. this sounds like a really good plan

 

[bluefox140]

yes I do. this sounds like a really good plan

hey man can you teach me how to wire these and to the inverter on and off board ? really appreciated

 

[mr_ed]

Hey - no worries.

1) Run wires from the positive and negative output terminals on the low voltage disconnect board to the 85 and 86 terminals on the relay (these are the terminals that connect to the relay electromagnet, not the relay switch). It won't matter which way you wire these - you just need to create the circuit to activate the magnet and pull the switch closed.

2) Strip the lead running to your inverter remote switch and cut one of the wires (if it's an RJ11 which it looks in the photos like it might be, then there may be a couple of unused wires in there - you'll need to work out which two the active wires are - suggest some googling or trial and error)

3) Connect one end of the cut wire to terminal 30 on the relay and the other end to terminal 87.

Once the above is done, if the low voltage cutoff board cuts power to the relay, the relay switch will open and turn off the inverter.

Note you should be able to get away with a very small relay, as I don't expect there is a significant current running through the switch (if it's an RJ11 then the wires are tiny so the current can't be much). The issue with relays is that they draw a current to hold the switch closed (which will be all the time unless you have a low voltage situation). The current draw on larger relays can be significant, so you'll want to go with the smallest / lowest draw relay you can get away with. You might be able to get away with a tiny PCB relay in your case - worth having a look at.

 

[mr_ed]

Let me know if that doesn't make sense

 

[bluefox140]

Hey - no worries.

1) Run wires from the positive and negative output terminals on the low voltage disconnect board to the 85 and 86 terminals on the relay (these are the terminals that connect to the relay electromagnet, not the relay switch). It won't matter which way you wire these - you just need to create the circuit to activate the magnet and pull the switch closed.

2) Strip the lead running to your inverter remote switch and cut one of the wires (if it's an RJ11 which it looks in the photos like it might be, then there may be a couple of unused wires in there - you'll need to work out which two the active wires are - suggest some googling or trial and error)

3) Connect one end of the cut wire to terminal 30 on the relay and the other end to terminal 87.

Once the above is done, if the low voltage cutoff board cuts power to the relay, the relay switch will open and turn off the inverter.

Note you should be able to get away with a very small relay, as I don't expect there is a significant current running through the switch (if it's an RJ11 then the wires are tiny so the current can't be much). The issue with relays is that they draw a current to hold the switch closed (which will be all the time unless you have a low voltage situation). The current draw on larger relays can be significant, so you'll want to go with the smallest / lowest draw relay you can get away with. You might be able to get away with a tiny PCB relay in your case - worth having a look at.

make sense thanks alot

 

[Zil]

Better read your inverter manual. Most, if not all, state switch off the load before switching inverter off.

 

[mr_ed]

Better read your inverter manual. Most, if not all, state switch off the load before switching inverter off.

Interesting point. This would apply to any low voltage disconnect (I.e. not just my proposed set up, but any battery connect / pro latch system). Something to think about. I wonder how the internal low voltage disconnect deals with that.

Mine will just be an emergency backup- it will be very rare that I would ever get my battery down that low- so I’m comfortable using it.

 

[MrNatural22]

Better read your inverter manual. Most, if not all, state switch off the load before switching inverter off.

I wonder if that pertains also to potential inverter harm if the inverters LVD activates while a load is running? I guess that may be something asked to the tech support.
I know Samlex support always answers telephone inquiries.