Camper Van 500Ah LIFePO4 battery bank build.

[James Smith]

I am starting from scratch and have been researching this off and on for the past 3 years, I'm a carpenter by trade and electronic/electrical/computer info. seems like it needs to be pounded into my head in small increments.  The lithium online "self-study" program is made very difficult and frustrating by all of the conflicting "facts" that are found.

My system will be 12 volts and will consist of 20 Fortune Brand 100Ah 3.2V 6C aluminum cased cells controlled by the ElectroDacus SBMSO.  (ElectroDacus is currently  on order)  I plan to parallel the batteries in groups of 5 and then put those groups in series to make 12 volts.

It will have two charging sources, a Sterling BB1260 battery to battery charger and a Xantrex Freedom XC 2000 Inverter Charger.  I may add some solar later.

The main reason for the battery bank is to run a Dometic Cool Air RTX 2000 12V roof top air conditioner that is rated at 6824 BTU.

I WLL HAVE MORE QUESTIONS AS I FINISH WORKING THROUGH THIS BUT FOR NOW I HAVE TWO:

(1)  I already have 8 of the Fortune batteries that I bought almost 2 years ago and am getting ready to buy the other 12.  The 8 batteries have not been used yet and are stored in my basement, I check the voltage every month or two and it has remained very constant.  The voltage is 3.33V and is the same as when The Electric Car Parts Co. shipped these to me in June 2019.

Will the SBMSO be sufficient for balancing this battery bank? 

If not is it possible to use another balancer with the ElectroDacus?

Carl at ECPC thinks that I will need one.  Two years ago before I found your BMS he sold me a simple BMS and "Deligreen Active Battery Equalizer" and he thinks that I still need the balancer especially because of the age differences in my cells.

I'm already aware that I will have to hook my cells together and let them balance before I assemble my bank.

(2)  I believe that both my Sterling Battery to Battery Charger and my Xantrex Inverter Charger are both already designed so they can be controlled by the EXT IO4 port for charging and the inverter portion can be controlled by the EXT IO3.  Am I correct?

Thank you for your time!

[Dacian Todea]

James,

Yes the battery will be correctly configured as groups of 5 cells in parallel and then 4 of these groups in series for 12V. The BB1260 should work as it has remote ON/OFF but the Xantrex Freedom will not work as there is no ON/OFF remote even just for inverter but you will need separate remote for inverter and separate for charger and as far as I know the Victron Multiplus 3000VA and up are the only ones that have separate remotes and they explain how that is setup here https://www.victronenergy.com/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf

1) Is not relevant that you have older stock cells if you can by the exact same model they will perform the same so you can use the 8 you already have distributed as groups of two then the other 3 in each group will be new cells then pack should be fairly equal and yes the SBMS0 will keep the battery in balance nothing else is needed.

2) As mentioned above the BB1260 will work (someone has the smaller BB1230 so I looked recently in to that) but the Xantrex will not work even just as an inverter as there is no toggle ON/OFF switch just a momentary switch that will change the state and to make that work you will need extra custom circuit you will need to build and even so that will only controll the inverter and not the charger part as that will need to have a separate controll.

What EXT IO3 and IO4 is is just a switch normally open when devices need to be OFF and close circuit when devices need to be ON so it is like a small electronic relay.

Best regards,

Dacian.

[Dacian Todea]

Sorry I missed the ignition signal on the XC 2000 so that can be used as an inverter and the EXT IO3 can control the inverter. But the charger still has no separate control so it can not be used to charge the battery. You can maybe add a SSR on the AC input line allowing the SBMS0 to disconnect the AC input line but maybe not a very convenient way of control as it will not work in UPS type mode so maybe good if just occasionally you need to charge the battery from the grid.

 

[James Smith]

Dacian,

Thanks for the prompt response!

I still believe that the Xantrex  XC 2000 may work for charging.  On page 55 of the Owners Guide (Document No. 975-0784-01-01      Rev C      Date:  July 2020) it calls Setting #26 "The Charger Ignition Control".  This appears to work off of the same wire as the ignition signal for the Inverter and can be set either OFF or Auto-ON.  Would it be possible to connect this wire to both the EXT 103 and EXT 104 ports to control both the inverter and the charging?

The ignition signal is supposed to be 12 volts, is that a problem?  What does the SBMSO supply for a signal?

Note:  There is more than one version of the Xantrex Freedom XC Inverter Charger manual on line so the above reference numbers are important.  These numbers are found on Page ii.

Thank You,

James Smith

[Dacian Todea]

James,

The controls for chargers needs to be separate from those for discharging else when battery is fully charged both the charger and the inverter will power OFF and likely that is not what you will want.

There is no voltage on the EXT IOx it is just a small solid state switch with open circuit for OFF and close circuit for ON or enable charger or discharge depending on type. The EXT IOx are based on Toshiba TLP172GM and capable of max 50mA any voltage up to 350Vdc

So the way it will be connected it will be EXT IO3+ connected to battery+ 12V through a 470Ohm resistor (resistor is for overcurrent protection in Case EXT IO3- is shorted to GND the current will not be higher than 50mA and the TLP172GM is fully protected so are the wires). Then EXT IO3- is connected to inverter ignition signal.

That inverter is likely the same inverter made by MPP Solar that I also use is just made by the OEM for Xantrex.

In order for the SBMS0 to protect the battery all chargers need to have remote ON/OFF connection and separately all Loads so that when battery is fully charged 3.55V in case of LiFePO4 all chargers will be stopped but not the Loads then if any cell is below 2.8V all loads will be stopped to protect battery from over discharge but not the chargers they will still be enabled.

[James Smith]

Dacian,

Thanks again for all of your help, I understand what you said about possibly using a SSR on the AC input line and that may be a possibility but I still have some more questions.

(1)  You noted that the way my Xantrex is set up that both the charger and the inverter will power OFF when the battery is fully charged.  For me that would not be much of a problem if I am able to turn the inverter back on.  If the ElectroDacus  SBMSO will let me do that what would be the simplest method?  (I would not need the inverter turned back on until the shore power is disconnected from the inverter/charger.  This is because of the automatic transfer switch inside the Xantrex that will pass power through for my AC power needs while I'm charging so I do not need the inverter at that time only when I don't have shore power.)

(2)  Do I understand correctly that when using the SBMSO that the ON/OFF Switch on the inverter/charger should be left in the OFF position?

(3) Since you did not mention the possibility of using something like a Victron Battery Protect or Charge Control, I assume that these would not work for my situation.  Is that a correct assumption?

Thanks,

James Smith

[Dacian Todea]

James,

1) Once the battery is full the Xanterx will be turned OFF both inverter and charger part then you can not manually turn that ON unless you bypass the SBMS0 and lose the protection for over charger and overdischarge.

Not quite sure if the bypass is not alos disconnected when the inverter charger is turned OFF as on my inverter that will be the case.

2) I have not seen an ON/OFF button on the Xantrex other than the momentary type switch next to the display. Hope you understand that you can not have a momentary switch in the OFF position as that is like a computer mouse click so is always open circuit and circuit closes just as long as you push the button when you release it will be open circuit again and the device changes state so you need to know the state before you pushed the button to know what the new state will be ON or OFF.

3) The victron battery protect can not disconnect the DC supply to an inverter or inverter charger.

If you want to understand how a inverter charger that can be controlled by a BMS should look like check the spec for the Victron multiplus  https://www.victronenergy.com/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf they have separate remote ON/OFF for the inverter and for the charger. Open circuit means OFF and close circuit means ON that way if the remote wires brake for some reason the device will be safely in the OFF position.

[James Smith]

Dacian,

I've been thinking more about my shore power charging situation and I wanted to ask you about an idea that I have and see if you think it will work.

Just to give you a little more info. about the Xantrex  Freedom XC  2000 Inverter/Charger.  The 30 amp AC pass through uses a normally closed switch so that will work any time the unit is plugged in.  Also the on/off switch is a mechanical switch that has both  in and out positions, not a momentary type.  Both the inverter/charger and the available remote panel use this same switch.  These items will likely not make any difference in my situation though, just filling you in.

(1)  My idea is to use the Xantrex for both inverting & charging but NOT for bringing AC power into the van through the transfer switch.  I would bring power in through a mechanical selector switch so that I could manually switch between shore power or inverter power.  I would control the inverter by means of the ignition signal that we previously discussed and I would control the charging with an SSR on the AC input line as you said was a possibility.  The charger via the SSR would be powered by a dedicated circuit inside of the van.  The Xantrex charges at a max. of 80 amps @ 12 VDC and draws  a max. 11 Amps @ 120 VAC.

(2)  Do you see any problems with this idea?

(3)  If this is a workable idea do you have a recommendation for an SSR?

Thanks Again!

James

[Dacian Todea]

Hi James,

Any AC SSR should be capable to switch the AC input on the charger. Get one that is 40A rated or more and you will need to install it on a heat sink as they usually have about 1V drop and at 11A that is 11W so it will not work without a heatsink.

Usually all SSR brands are OK for AC the DC ones are more problematic and but the AC ones use IGBT normally so they are not a problem.

[James Smith]

Dacian,

Thank you very much for the reply!  I believe that this should be a good solution for my situation.

I'm sure to have more questions later but for now I have one more charging question.  I believe that the SBMSO will allow me (if needed for a quick charge) to charge from both the Xantrex and my Sterling 60 amp battery to battery charger at the same time.  This would give me a charging rate of somewhere around 140 amps.  Am I correct that both chargers can be used at the same time?

Thanks,

James

[Dacian Todea]

James,

Unless you manually disable a charge source the SBMS0 will allow all connected charge sources to charge until battery is fully charged. A well installed 500Ah battery should not have a problem handling 140A charge current.

[James Smith]

Dacian,

Thanks for the reply!  It seems like I'm finally starting to get a grip on at least portions of my build.

James

[James Smith]

For Dacian or Anyone That Has An Opinion,

What online circuit diagramming tools/sites are both good and easy to use for a campervan lithium project?

Thanks,

James

[Oberon Robinson]

Hi James, I suggest checking out FarOutRide: https://faroutride.com/electrical-system/

There are also some great resources at https://diysolarforum.com/resources/categories/how-to-pdfs-or-ebooks.4/

For background, the MarineHowTo article on LiFePO4 systems, and the Nordkyn Design series on lithium battery systems are essential reading.

And of course, there's the Beginner's Guide to ElectroDacus. :)

That should keep you busy for a couple of minutes.

Oberon

[James Smith]

Oberon,

Thank You for the suggestions!  At this point I'm mainly looking for a good site to start working on a wiring diagram that I can print out, however, more knowledge is always a good thing.

Thanks,

James