Any Alternative? from using EXTIO3/4 to control 500amp Isolator Relay

[Gilbert]

Hi everyone,

I am planning to setup electrodacus for my camper, and my current setup will be 620ah Lifepo4 with 3 charging sources (Alternator, Solar, Shore 120VAC) & mainly 2 loads (3000Watt Inverter & 12v devices: largely 12V Air Conditioner @ 80amp)

I have most of my electrical setup figured out and purchased.  Largely thanks to this forum, learned so much!

But my only question/concern right now is using 500amp Isolator Relays (example: BlueSea MC-ACR Relay), as they requires power to stay CLOSED, this is "acceptable" for the EXTIO4 turning on and off the charging inputs, but for the EXTIO3 for system's loads, this means a constant draw of power 24/7, unless I manually shut down all powers.

I already exhausted my searching in this forum and on Google, does anyone has any suggestions on this?   

I am still hoping for a Normally Closed Relay or a circuit breaker that is triggered by electrical signal (EXTIO3), since my inverter is 3000watt, I will aim for minimum relay supporting 500amp.

Any recommendation or suggestions will be greatly appreciated!!

[Dacian Todea]

Hi Gilbert,

You should not need any relay for anything.

What model is your inverter? It should have a remote ON/OFF or maybe one can be made thus SBMS0 EXT IO3 can directly turn OFF the inverter without any relay or trip breaker needed.

For alternator I guess you will have a battery to battery charger and that will have an ignition signal that can be used as remote ON/OFF

Shore ? What charger you use for that ? That may also have remote ON/OFF and for solar if you use the DSSR20 that is OK or if maybe Victron MPPT then that also has remote ON/OFF

For the small 12V loads you can use the Victron BP65

[Gilbert]

Thank you so much for the comments.

You gave me alot of good thoughts to look into.  Really Appreciated!!

I still have some concerns, and I believe I still needs a Relay to disconnect incase of low temperature, high/low voltage cutoff.

I installed a 12VDC Air Conditioner, and it can max at ~80amps, so for 12VDC, with electric Fans and hot waters (all 12VDC), I plan for 100amps at once on the safe side

Right now my setup consist of these:

LOADS:

1) Xantrex PROsine 3.0 12v 3000Watt (this is very old, but working flawlessly, only down side is charging voltage only good for AGM, so I will disable its charger, and only use it as an inverter)  I may need to hack my inverter to remote turn off with EXTIO3.

2) 12VDC Loads - the Victron BP-100 is my solution.  100A continuous with 600A peak!  price is great too, only ~$60.   I wonder what is its idling current usage and how it works.  will need to do more research into it.  I most likely use EXTIO5/6 for this.   My plan is to turn off Inverter by ~25% SOC, then turn off 12v Loads by ~10%.

CHARGE:

1) Alternator 280amps, I connected it with a BlueSea ML-ACR 500A Relay (I already have this in hand, so I will use EXTIO4 to remote cutoff the Relay)

2) Shore Power with PowerMax 60amp 12v, it's only $120 for 60a charging, but it has no remote turn off.  This I may still need a Isolator Relay.  I wonder if the Victor BP-100 can be used??)

3) I have 4 72Cells 220watts Solar Panels - with Tracer 80A MPPT solar charge controller.   It has built in Low Temperature Cutoff, but has no remote cut off, so I may connect the charging 12V output together with the Shore Power output, both using the same relay controlled by EXTIO4.

[Gilbert]

After more research into  Victron BP-100/220, they are solid state Relay, and can be used on both Charge and Load side and control by electrodacus BMS.   I think this will be the solution to my setup.   

If you have any other suggestions or recommendation, please share and I will love to learn and look into other options!   

Thanks again everyone!

[Dacian Todea]

Gilbert,

Loads

1) The problem with that is that it has no remote ON/OFF control it needs separate for charging and for inverter but if you can hack that then it can be used. To get an idea of how an inverter charger should work look at how the Victron inverter charger is designed to be controlled by a two signal external BMS including SBMS0  https://www.victronenergy.com/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf

2) Yes that is ideal for DC loads and usually the 65A is more than enough for small DC loads. It uses very little current the remote is just less than 2mA and probably less than 10mA self consumption.

Charge

1) You will want a battery to battery charger and not just a relay as LiFePO4 will take all the current a source can provide an more so the alternator will be smoking fairly fast as alternators are not constant current charge sources so they will push as much current as they can (actually more than they can) trying to get to the voltage set point around 14.4V and that can take hours so alternator will overheat and die.

2) Yes BP100 can be used but why get this that has no remote ON/OFF when you already have Xantrex inverter charger and you can add a SSR on the AC input of that and control that to stop the charging. There is no such thing as an AGM or Lithium charger. As long as it has a remote ON/OFF the BMS will take care of the charging since LiFePO4 only needs the Bulck side the charging will end sooner than getting to absorption and the other stages for Lead Acid.

3) You may damage the Tracer MPPT if you disconnect the battery from it. You can ask but the only one that I know specifying that disconnecting the battery from MPPT is OK is the Victron and most others will get damaged if that happens.

[Gilbert]

I really appreciated your inputs and recommendation.  Thank you.

I do have some questions/comments on your suggestions, I will type them in RED below.

On Thursday, May 27, 2021 at 12:59:56 PM UTC-4 electr...@gmail.com wrote:

Gilbert,

Loads

1) The problem with that is that it has no remote ON/OFF control it needs separate for charging and for inverter but if you can hack that then it can be used. To get an idea of how an inverter charger should work look at how the Victron inverter charger is designed to be controlled by a two signal external BMS including SBMS0  https://www.victronenergy.com/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf

I will love the Victron Multiplus Inverter/Charger, but currently I have a budget to follow, and since I already have a Xantrex on hand, it be ideal I use it instead.

The inverter is controlled by a remote, so I am hoping to jump the "ON/OFF" switch on the result for inverter, if charger too then both.  the ON/OFF switch are push button, so I hope they can be connected to EXTIO3/4.   
Since EXTIO3/4 is open or closed, while here it's PUSH button to close circuit for a sec to signal a ON/OFF switch, hopefully I can find a way to hack it.

2) Yes that is ideal for DC loads and usually the 65A is more than enough for small DC loads. It uses very little current the remote is just less than 2mA and probably less than 10mA self consumption.

Charge

1) You will want a battery to battery charger and not just a relay as LiFePO4 will take all the current a source can provide an more so the alternator will be smoking fairly fast as alternators are not constant current charge sources so they will push as much current as they can (actually more than they can) trying to get to the voltage set point around 14.4V and that can take hours so alternator will overheat and die.

2) Yes BP100 can be used but why get this that has no remote ON/OFF when you already have Xantrex inverter charger and you can add a SSR on the AC input of that and control that to stop the charging. There is no such thing as an AGM or Lithium charger. As long as it has a remote ON/OFF the BMS will take care of the charging since LiFePO4 only needs the Bulck side the charging will end sooner than getting to absorption and the other stages for Lead Acid.

Honestly, I will LOVE to use the Xantrex Built-in charger, it's automated, has 120amp charging capacity, and it's free. Its just that when I was researching, people told me Xantrex PROsine 3.0 is a great Inverter/charger, but back in 2000s, and it is only designed for lead-acid battery, and it's charging voltage doesn't fit lifepo4 battery chemistry.  That is why I decided to just use it as inverter only.

Looking at the  Xantrex   operating manual, this is its charging voltage:

As I read online, People recommend to charge Lifepo4 battery, keeping bulk and absorption voltage @ 14.4 V, while a float is unnecessary, but if so, just keep floating voltage under 13.6 V.  

Sadly, the Xantrex Charger, cannot be adjusted to fit for Lifepo4, this is the reason why I decided to buy an additional 120vac charger.

With the above details, do you still recommend using the Xantrex to charge my Lifepo4?

Also I have another question, what exactly do you mean the BMS will take care of the charging? 

3) You may damage the Tracer MPPT if you disconnect the battery from it. You can ask but the only one that I know specifying that disconnecting the battery from MPPT is OK is the Victron and most others will get damaged if that happens.

Thanks for the headsup...   if this is the case, the only solution for me is to purchase a MPPT charger with remote ON/OFF feature.   This kinda sucks, consider Victron MPPT charger for 70amp charging, it's like $500+ (even if I buy 2 Victron 150/35 charger and parallel them)...  Do anyone has any other recommended MPPT charger that has remote on/off?

[Gilbert]

I was too excited with the electrodacus BMS, I couldn't sleep last night... LOL

I read so much and I believe I found a way so I can use my Xantrex PROsine 3.0 as charger as well.

FYI, since this inverter/charger is really old school, charging voltage (as well as cutoff voltage) cannot be manually adjusted only predefined values to choose from, but I found a way that fit my need.

Information I found that can "somewhat" adjust my Xantrex to charge with desired voltage for my 620ah lifepo4 battery:

On the Xantrex Inverter/Charger, I will set the battery type as FLOOD, unplug the battery temp sensor and manually set it to HOT, which gives me 14.0volt on charging (which is what I want to keep 3.5volt per cell), and I guess the 13.1v of float voltage doesn't really matter.

My low/high voltage cutoff setting will be:

• I want my Inverter to cutoff first before BMS, so I will set my Xantrex Low voltage cutoff to 12.0volt, which is 3v per cell, and I will set my BMS low voltage cut off to 11.2v or 2.8v/cell.
• For high voltage cutoff, I will just set it to 14.6v or 3.65v/cell

This is my final setup of my electrical system, I need your feedback on this if I overlooked anything, THANKS!

LOADS:

1. Xantrex PROsine 3.0 12v 3000Watt - Control by EXTIO3 (QUESTION: do I still need the BMS to cut the inverter load? if the inverter itself will cut off once voltage drop to 12volts?)
2. All 12VDC Loads will be protected by Victron BP-220.  I got it for $70.   And this will be controlled by EXTIO3 as well

CHARGE:

1. Alternator 280amps, connected through BlueSea ML-ACR 500A Relay , and this charging source will be controlled by EXTIO4
2. Xantrex PROsine 3.0 12v 3000Watt - Control by EXTIO4 (QUESTION: since the float voltage is only 3.1volt - which won't really charge the Lifepo4, do I still need the BMS to remote turn off the charger?)
3. 4 72Cells 220watts 5amp Solar Panels - I will use Tracer 80A MPPT solar charge controller with one DSSR20 between the MPPT and solar panels.  And the DSSR20 will be used as cutoff only, by EXTIO4.   (QUESTION: do I need the DEXT16? or just DSSR20 is good enough to remote ON/OFF solar charging?   My 4 solar panels output is 44volt @ 5amp, and I will parallel time incase one is shaded, so total is 44volt @ 20amp, is this too close to DSSR20 20amp?)

[Dacian Todea]

Since EXTIO3/4 is open or closed, while here it's PUSH button to close circuit for a sec to signal a ON/OFF switch, hopefully I can find a way to hack it.

You can hack it but it will not be super simple see Ross version https://groups.google.com/g/electrodacus/c/M8fe1VRLtYw/m/FokPNKT5AwAJ

You need the button and the ON LED signals and the circuit ross made or there is someone that made an arduino version I think 

FYI, since this inverter/charger is really old school, charging voltage (as well as cutoff voltage) cannot be manually adjusted only predefined values to choose from, but I found a way that fit my need.

You do not need to do anything to the charger other than allow SBMS0 to turn the charger ON or OFF. The charger will be perfectly fine for charging LiFePO4 as only the bulck stage is used and as soon as any cell gets to 3.55V the SBMS0 will turn OFF the charger as battery is already full.  The charger will never get to absorption, float or equalize stage as it will be turned off way before that.

QUESTION: do I still need the BMS to cut the inverter load? if the inverter itself will cut off once voltage drop to 12volts?

Yes the SBMS0 needs to have remote ON/OFF control as protection is based on individual cells not total battery voltage that is irrelevant.

QUESTION: do I need the DEXT16? or just DSSR20 is good enough to remote ON/OFF solar charging?   My 4 solar panels output is 44volt @ 5amp, and I will parallel time incase one is shaded, so total is 44volt @ 20amp, is this too close to DSSR20 20amp?

You do not need the DEXT16 but a DSSR20 can not handle more than 3x 220W panels and you are not allowed anyway to parallel more than 3 of those panels unless you have individual fuses for each panel. You will need two DSSR20's for 4 panels and you do not need individual fuses.

[Gilbert]

Thank you for all the clarification.

I will look into the Push button hack, and decide what MPPT charger I go for.

Will post my update & final schematic  once everything is ready.