battery backup switch

[frankz66]

Hi everyone, I wanted to know if there is a simple way perhaps with a graphic diagram on how to manage at the cut off of the panels a 110 amps AGM 48v accumulation and a possible 100 amp lifepo4 accumulation. Also before dawn comes for example at 5 am the switch returns to the accumulation agm . My need would be that only in the evening if the agm accumulation goes for example below 48v the switch with the lifeopo4 accumulation is made. Thank you all .

 

[robbob2112]

What you are looking for is a programable logic controller , PLC, (Siemens S7-1200 Series or any one of a dozen others)

It can be used to sense the voltage of both battery banks and switch from the AGM to the LiFePO4 when the AGM is low. It also has a built in clock and can switch back at dawn or using an electric eye to see dawn. And it has several dry contacts in it that could be used to switch the SCC output between banks using contactors (large high current relays) to control the bank being charged.

You would need to identify PLC units that are available in Malta and get help from a local rep for programming.

Note- you can do the same thing with voltage sense relays, contactors and a timer

 

[frankz66]

What you are looking for is a programable logic controller , PLC, (Siemens S7-1200 Series or any one of a dozen others)

It can be used to sense the voltage of both battery banks and switch from the AGM to the LiFePO4 when the AGM is low. It also has a built in clock and can switch back at dawn or using an electric eye to see dawn. And it has several dry contacts in it that could be used to switch the SCC output between banks using contactors (large high current relays) to control the bank being charged.

You would need to identify PLC units that are available in Malta and get help from a local rep for programming.

Note- you can do the same thing with voltage sense relays, contactors and a timer

Thank you, what kind of contactors could I use? Do you have any examples to show me or rather a link?

 

[robbob2112]

What size is your inverter? 5kW?

What is your budget?

Do you order from the US or does it need to be in the EU?

I can do up a diagram tomorrow

 

[frankz66]

The m i inverter is an offgrid 3000/6000 pure sine

Thinking of a switch (in my minimum competence) or a dry contact with diodes ..... it is limited.

I wanted to buy in Eu ( Italy )
My plant consists of an epever 6415AN , 1.5 kwp FV , a current accumulation of 48v 110 AGM amps .
I also have a power generator that is currently connected to a contactor, which if it is started switches the line from photovoltaic to the generator.

 

[ThaiTaffy]

Problem you will have with contactors is most that are rated for DC above 100amps normally come with 24v coils (Schneider for example)so you would need some form of Stepdown if your controlling via your batteries this could likely be controlled via a SSR and Arduino/esp if you don't want the expense of a dedicated plc but to automate it your looking at a fair bit of research if your starting from scratch.
In which case I might be better to pay the money and go with robbob's suggestion about a Siemens plc and get it programmed for you.

 

[frankz66]

Problem you will have with contactors is most that are rated for DC above 100amps normally come with 24v coils (Schneider for example)so you would need some form of Stepdown if your controlling via your batteries this could likely be controlled via a SSR and Arduino/esp if you don't want the expense of a dedicated plc but to automate it your looking at a fair bit of research if your starting from scratch.
In which case I might be better to pay the money and go with robbob's suggestion about a Siemens plc and get it programmed for you.

Hi, I use the home assistant for controls and automations, so I can intervene for the software part. What I'm interested in is the switching system through some device that I don't know which one!

 

[ThaiTaffy]

Hi, I use the home assistant for controls and automations, so I can intervene for the software part. What I'm interested in is the switching system through some device that I don't know which one!

So you can use esphome in that case just an esp with relay to switch two DC contactors one for each battery with one being on NC and the other on No

 

[ThaiTaffy]

Maybe something like this it's designed for EV but would cover your ratings
https://evshop.eu/en/relays/208-gigavac-gv200pa-contactor-12v-coil-without-economizer.html

 

[ThaiTaffy]

Let robbob do you a detailed diagram maybe I'm completely off and thinking too rudimentary, will be interesting to see what he comes up with.

 

[frankz66]

Let robbob do you a detailed diagram maybe I'm completely off and thinking too rudimentary, will be interesting to see what he comes up with.

Thank you, also because the switching with a relay (maybe power ssr because the maximum amperes are over 100 amperes at 48v) or something else...

 

[ThaiTaffy]

Thank you, also because the switching with a relay (maybe power ssr because the maximum amperes are over 100 amperes at 48v) or something else...

The relay would only power the contactors and no current from the batteries would ever pass through them unless it was being stepped down to power the esp.

 

[frankz66]

The relay would only power the contactors and no current from the batteries would ever pass through them unless it was being stepped down to power the esp.

A well-made scheme is needed! We await the response from ROB

 

[robbob2112]

Maybe something like this it's designed for EV but would cover your ratings
https://evshop.eu/en/relays/208-gigavac-gv200pa-contactor-12v-coil-without-economizer.html

The problem with these is they are only rated for 3 to 15 switches under load and then they are useless. Sometimes it is even 1 switch, all depends on the amps at switchover - what is needed is a motor reversing contactor with blowouts. Something like is used on a golfcart to switch but larger to handle the loads. The one linked is a battery disconnect for when you turn the car off or if there is an accident it switches off the battery and requires replacement if the car can be put back in service because it is destroyed internally when it switches under load. I have 8 of them I am going to use in a DIY battery bank where I can switch off the load before switching them.

I am looking at Albright SW202/SW88/SW192/etc

These are the type switches used in electric cars, forklifts, gold carts, etc. And this particular style contact has spare parts available so if the contacts weld at some point instead of replacing the contactor you can replace just the contacts.

Contactors are about $150usd for each set of SPST and you would need two. If you can get the DPDT contactor you need one that costs around $230usd

SPDT - single pole dual throw
DPDT - dual pole dual throw

Design to follow soon -

I'll do two ways so you can adjust depending on what you can get. Will list the specs as well. Any local place that services forklifts or heavy equipment can probably order them for you. Or amazon.it has one style of the SW202 - of course I can't read it, but it is there.

 

[frankz66]

The problem with these is they are only rated for 3 to 15 switches under load and then they are useless. Sometimes it is even 1 switch, all depends on the amps at switchover - what is needed is a motor reversing contactor with blowouts. Something like is used on a golfcart to switch but larger to handle the loads. The one linked is a battery disconnect for when you turn the car off or if there is an accident it switches off the battery and requires replacement if the car can be put back in service because it is destroyed internally when it switches under load. I have 8 of them I am going to use in a DIY battery bank where I can switch off the load before switching them.

I am looking at Albright SW202/SW88/SW192/etc

These are the type switches used in electric cars, forklifts, gold carts, etc. And this particular style contact has spare parts available so if the contacts weld at some point instead of replacing the contactor you can replace just the contacts.

Contactors are about $150usd for each set of SPST and you would need two. If you can get the DPDT contactor you need one that costs around $230usd

SPDT - single pole dual throw
DPDT - dual pole dual throw

Design to follow soon -

I'll do two ways so you can adjust depending on what you can get. Will list the specs as well. Any local place that services forklifts or heavy equipment can probably order them for you. Or amazon.it has one style of the SW202 - of course I can't read it, but it is there.

Thank you for the time you have dedicated to me. But if I wanted to do the switch manually what should I use? The system is 48v

 

[robbob2112]

You need a battery selector - you can choose between battery banks with it -
basically this is what I was building was one that worked off your existing control and some contactors to do the work automatically, with a safety feature to prevent both from being connected at once.

Technically you can just use a generic battery disconnect in the negative line of each battery bank

Turn off inverter
turn off AGM
turn on LFP
turn on inverter

OR
turn off inverter
turn off LFP
turn on AGM
turn on inverter

It won't be automated and it won't have any safety interlock to prevent you from turning on both at once. Not terribly safe in the long run because all it would take is once of turning them on while the AGM is drained and the LFP is full or vs versa and damage would happen to one of them.




You could get two of these and put them in a box with an interlock to prevent them from both being on

Amazon.com

Or any other set of DC rated breakers and an interlock kit (basically a piece of sheet metal mounted in such a way that when you switch the handle of one the other is tripped and vs versa

Look up generator interlock and you will see what I mean. The critical part is to get breakers that are rated for DC and are dual pole so you connect and disconnect both positive and negative at once.

 

[frankz66]

You need a battery selector - you can choose between battery banks with it -
basically this is what I was building was one that worked off your existing control and some contactors to do the work automatically, with a safety feature to prevent both from being connected at once.

Technically you can just use a generic battery disconnect in the negative line of each battery bank

Turn off inverter
turn off AGM
turn on LFP
turn on inverter

OR
turn off inverter
turn off LFP
turn on AGM
turn on inverter

It won't be automated and it won't have any safety interlock to prevent you from turning on both at once. Not terribly safe in the long run because all it would take is once of turning them on while the AGM is drained and the LFP is full or vs versa and damage would happen to one of them.




You could get two of these and put them in a box with an interlock to prevent them from both being on

Amazon.com

Or any other set of DC rated breakers and an interlock kit (basically a piece of sheet metal mounted in such a way that when you switch the handle of one the other is tripped and vs versa

Look up generator interlock and you will see what I mean. The critical part is to get breakers that are rated for DC and are dual pole so you connect and disconnect both positive and negative at once.

I understand, however the procedure with the hour switch involves a series of operations which are unmanageable in the long term. However, the solution with a dry contact and an SSR relay could be fine, the problem is the high currents. Some time ago I had seen a video on YouTube of a nice photovoltaic system, and the person who created it had created a system using dry contact and a series of power diodes to use an AGM bank as a backup if the lifepo4 voltage dropped .
This is a link :

 

[robbob2112]

Your home automation should be able to monitor the voltage of the battery banks and know the time.

With the pair of sw202 hooked up all it would take is a dry contact relay to switch it on or off. The power side comes from either battery in use since the coil voltage is 7-96vdc..the other side of the dry contact is hooked to the coil pin of the contactor to flip or back.

You could use the ssr digital relay or any common relay for the low current of the coil.

 

[frankz66]

Your home automation should be able to monitor the voltage of the battery banks and know the time.

With the pair of sw202 hooked up all it would take is a dry contact relay to switch it on or off. The power side comes from either battery in use since the coil voltage is 7-96vdc..the other side of the dry contact is hooked to the coil pin of the contactor to flip or back.

You could use the ssr digital relay or any common relay for the low current of the coil.

I understood little . Can you make a scheme?

 

[ThaiTaffy]

The problem with these is they are only rated for 3 to 15 switches under load and then they are useless. Sometimes it is even 1 switch, all depends on the amps at switchover - what is needed is a motor reversing contactor with blowouts. Something like is used on a golfcart to switch but larger to handle the loads. The one linked is a battery disconnect for when you turn the car off or if there is an accident it switches off the battery and requires replacement if the car can be put back in service because it is destroyed internally when it switches under load. I have 8 of them I am going to use in a DIY battery bank where I can switch off the load before switching them.

I am looking at Albright SW202/SW88/SW192/etc.

TIL
Thanks this was where I was confused I was thinking it was for motor switching.

Your home automation should be able to monitor the voltage of the battery banks and know the time.

With the pair of sw202 hooked up all it would take is a dry contact relay to switch it on or off. The power side comes from either battery in use since the coil voltage is 7-96vdc..the other side of the dry contact is hooked to the coil pin of the contactor to flip or back.

You could use the ssr digital relay or any common relay for the low current of the coil.

That's what I was thinking and by using each side a common dry contact relay used on many esp projects(NC/NO) you have in theory taken care of the safety aspect rather than having individual outputs control each relay.

 

[frankz66]

You need a battery selector - you can choose between battery banks with it -
basically this is what I was building was one that worked off your existing control and some contactors to do the work automatically, with a safety feature to prevent both from being connected at once.

Technically you can just use a generic battery disconnect in the negative line of each battery bank

Turn off inverter
turn off AGM
turn on LFP
turn on inverter

OR
turn off inverter
turn off LFP
turn on AGM
turn on inverter

It won't be automated and it won't have any safety interlock to prevent you from turning on both at once. Not terribly safe in the long run because all it would take is once of turning them on while the AGM is drained and the LFP is full or vs versa and damage would happen to one of them.




You could get two of these and put them in a box with an interlock to prevent them from both being on

Amazon.com

Or any other set of DC rated breakers and an interlock kit (basically a piece of sheet metal mounted in such a way that when you switch the handle of one the other is tripped and vs versa

Look up generator interlock and you will see what I mean. The critical part is to get breakers that are rated for DC and are dual pole so you connect and disconnect both positive and negative at once.

Hi, are you saying that a 48v switch like this would be fine? This is in case I wanted to do the exchange manually....

 

[ThaiTaffy]

Hi, are you saying that a 48v switch like this would be fine? This is in case I wanted to do the exchange manually....

Personally I'd say try find something a bit more quality it maybe rated for 300amp but the terminals on the back look like they would easily arc on switchover.

 

[robbob2112]

Hi, are you saying that a 48v switch like this would be fine? This is in case I wanted to do the exchange manually....

3 position that doesn't include a 'both', and quality. And two of them for safety so you switch both positive and negative. Breakers tied together would be safer and better so you can't ever even by accident turn both on at the same time.

1-off-2

 

[robbob2112]

note - I stopped with working out the automatic version when you said you wanted to do it manually. I assumed that meant the automatic version would be to expensive at around $350usd or so. The parts were all available in the EU.



Were it me I might get two of these and mount them side by side

ED252A-2 Albright Heavy-duty Emergency Stop Switch 250A 96V Maximum

Albright 250A heavy-duty battery disconnect switches with auxiliary, rated to 96Vdc at Arc Components Ltd. Double-pole emergency stop or panic switch, 250 Amps.

www.arc-components.com

So your switch procedure would be to - none of the switches are made to be used with current applied.

turn off inverter
push both switches in
pull the one you want - labeld lfp or agm
turn on inverter



The automatic version would be done with the inverter on and would just cause flickering of the lights when it switched. Or your automation could disconnect the inverter, make the switch, then reconnect the inverter.

 

[frankz66]

note - I stopped with working out the automatic version when you said you wanted to do it manually. I assumed that meant the automatic version would be to expensive at around $350usd or so. The parts were all available in the EU.



Were it me I might get two of these and mount them side by side

ED252A-2 Albright Heavy-duty Emergency Stop Switch 250A 96V Maximum

Albright 250A heavy-duty battery disconnect switches with auxiliary, rated to 96Vdc at Arc Components Ltd. Double-pole emergency stop or panic switch, 250 Amps.

www.arc-components.com

So your switch procedure would be to - none of the switches are made to be used with current applied.

turn off inverter
push both switches in
pull the one you want - labeld lfp or agm
turn on inverter



The automatic version would be done with the inverter on and would just cause flickering of the lights when it switched. Or your automation could disconnect the inverter, make the switch, then reconnect the inverter.

Thank you so much for providing me with all the relevant information. However, for the sake of technical curiosity, if you have the time and desire, you could draw up the diagram of the automatic one, in order to understand how to create an automatic switching system. Thank you .