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Old 06-07-2018, 09:13 PM   #1
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MPPT Solar and Lithium Question

So Iíve finished our solar/lithium upgrade. Now that itís installed itís not working like I expected so I wanted to see if this is right.

This is a Victron system with a 150/35 SmartSolar charge controller and a Victron BMV712 battery monitor. This is driving 300ah of BattleBorn batteries and getting power from 500w of solar on the roof. Thereís also a Victron Multiplus 3000 hybrid inverter but that doesnít matter for this discussion.

The solar controller seems to be all voltage based. It wants to go into float at a certain voltage etc. It doesnít seem to be helping support loads durring the day. Iíll be running the batteries down and all those solar panels will just sit there laughing at me. I think it may be expecting to just charge once a day in the morning. Hereís the question :

How can a solar charge controller work (well) with Lithum batteries that maintain a constant voltage from much of their discharge curve? Shouldnít the charge controller be talking to my battery monitor to find out the state of charge and kick on when power is being drawn durring the day? I donít have a Victron Color Control or a Venus central controller/monitor. Does it do that?
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Old 06-07-2018, 09:36 PM   #2
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you need a 110 to 12v converter that supports lion also.

the stock one from AS does NOT support Lion batteries
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Old 06-07-2018, 10:16 PM   #3
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MPPT Solar and Lithium Question

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Originally Posted by waninae39 View Post
you need a 110 to 12v converter that supports lion also.



the stock one from AS does NOT support Lion batteries


He has a multiplus hybrid inverter/charger... so the stock converter is gonzo in this install and he has one of the best pieces of equipment on the planet for inverter / converter functionality in a lion environment

I am following. I have a complete victron stack and the bmv / MPPT are networked via the CCGX using ve.direct bus, and then the multiplus is networked in via ve.bus. The system is set to use the bmv for soc status.

Since you donít have a CCGX and both your components (712 and MPPT) are smart I believe you can configure VE.Smart networking between the 2 to share SOC information via Bluetooth. You configure this via the victron connect app once youíve connected to one of the devices.

But even without ve.smart networking there is a way to make this work correctly as I know am solar and Lew both do non networked installs like this all the time.....

How did you configure your MPPT controller? What settings did you use?
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Old 06-07-2018, 10:49 PM   #4
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MPPT Solar and Lithium Question

Ah - looks like in a non networked environment battery voltage and current are still used to determine soc:

http://batteryuniversity.com/learn/a..._ion_batteries

So then it is critical for your MPPT to be configured correctly in terms of setting charged voltage. My victrons are 13.4 - 13.5v when fully charged and at rest.
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Old 06-07-2018, 11:52 PM   #5
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Ah - looks like in a non networked environment battery voltage and current are still used to determine soc:

http://batteryuniversity.com/learn/a..._ion_batteries

So then it is critical for your MPPT to be configured correctly in terms of setting charged voltage. My victrons are 13.4 - 13.5v when fully charged and at rest.
I talked to AM Solar and the fellow I talked to didn’t mention anything about networking betweeen the Battery monitor and charge controller. The Victron literature for VE Connect talks about it mainly for sharing voltage and temperature info. Neither are all that helpful for Lithium. Sure seems strange because without the SOC info I don’t see how the charge controller can make good decisions about when to charge lithium.

Does your installation, with the Color Control GX, start pulling power from the solar panels within a few minutes of the batteries being discharged even a little?

If there’s a way to network the two without a Color Control GCX or Venus I haven’t discovered it.

Battleborn said to set the Multiplus at 14.5v bulk charge and 13.5 float so that’s what I set the solar charger to as well. Not sure if that’s right. I have a call into them as well.
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Old 06-08-2018, 09:01 AM   #6
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Sounds like you have your MPPT setup correctly from a float/blunk perspective. Mine is set to 13.5 / 14.2 (for victron lithiums).

I can tell you most definitely SOC is shared across devices in a victron networked environment, at least with the MultiPlus anyways - because the MultiPlus has 3 different ways to measure SOC for it's charging algorithms, and in my configuration it sees the BMV in the system and automatically uses the BMV for SOC information - this is indicated to me on the CCGX (source for SOC). I have tested by unplugging the BMV com cable and the MultiPlus indeeds changes is source for SOC to it's internal calculation based on what 12v traffic it sees moving to / from the batts.

I can say that when my batts reach 100% SOC the MPPT does ramp down amps / current but keeps the float voltage at 13.5. In the one test I did I seem to remember that when I introduce 12v DC load when batts were 100%, the MPPT did ramp back up amps/current to help supply DC amps to the load. But I would need to re-test to confirm. I have also tested disconnecting the batteries and letting the MPPT supply all 12v amps to the trailer, and that did work as well (I have a huge array and can generate 40 amps DC out of my 150/85 on a sunny day).

For what it is worth I do not peg my lithium batteries and float them at 100%. Unlike lead acid, Lithium chemistry do not like that and it will cut the lifespan. I manage my battery bank to 90% charge. when I get to 90% I stop charging them. Once a month I will bring them up to 100% which is necessary to fully balance the cells, but otherwise I disconnect them from solar charging when boondocking until it's time to charge. The one exception for me is if I am running large loads like the AirCon - in which case I'll throw solar DC amps at it to minimize drain from the batteries.

When on shore power I disconnect the batteries from the system altogether and let the multiPlus convert down to supply 12v loads to the trailer, unless of course the batts are in need of a charge.

I'd give a call back to AM Solar if that is where you bought your gear - they'll know the answer on how the victron MPPT controller determines SOC in a stand alone configuration. My guess is voltage. But as I said - you don't want to float lithium batteries at 100% anyways.
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Old 06-08-2018, 10:16 AM   #7
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Hi

With the Battle Born's you *can* run them at a fixed voltage. It is *very* unclear how good an idea this is. If you set the MPPT to 14.6 for the first stage and 14.2 for the other two stages, it will do a pretty good job of keeping the batteries at full charge. If you set the later stages to a lower voltage ( say 13.6V ) then indeed things will drop a bit before the MPPT really gets going each day.

At least by my reading of the Victron stuff, you need a "brain" in the mix to get the MPPT and the BMV 712 to work together. They both have connectors on them to "chat". I don't think that's enough to get them to fully co-ordinate things.

Each and every Lithium battery out there seems to have a bit of a different approach to this and that. With the Battle Born's the BMS is fully integrated and you can't talk to it. There is no way to really know what the state of charge is. They will sit there pulling a fraction of an amp pretty much forever and ever if you keep them on charge. Is this power to the BMS? Is it the passive equalization? Are they haunted? No way to really know.

Bob
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Old 06-08-2018, 10:17 AM   #8
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Why not share what your MPPT settings are for the charge profile you are using? That sounds like the issue, if you didn't modify them to match the voltage of the BattleBorn (which is higher than Victron LFP) then its not going to work correctly. If your "float" is below the resting voltage of the BattleBorn then it will take a while before the SOC drops enough to drop the voltage so that the MPPT can detect it, remember that Lithium battery voltage profile is _very_ flat so any voltage based detection is unreliable.

I'd suggest editing your charging profile to have a voltage target of 14.5V or 14.6V for bulk, and the other stages should be at ~14.4V...you can tweak it from there down to perhaps 14.2V. You could technically float down to 14V, but you will need to just watch your actual voltage of your bank to see where it "rests" at...what happens is if the resting voltage of the bank under "load" doesn't drop below your float the charger won't switch to a higher voltage stage.

I haven't setup a Victron MPPT yet, mine is in the mail for me to install next week before our first trip of the season.
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Old 06-08-2018, 10:20 AM   #9
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BTW, you would probably get more info on this within the Electrical/Generator & Solar topic area: http://www.airforums.com/forums/f448/
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Old 06-08-2018, 10:24 AM   #10
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Hi

Things get a bit more complex depending on what you have done with the charge line from the 7 pin to the TV. As you fiddle the solar charger on the trailer, it can / will try to charge the TV battery. Running the TV battery at Lithium voltages probably isn't a good idea. One quick solution is to disconnect the wire to the TV. Another solution is a DC / DC converter on the TV wire.

With the DC / DC converter, you will get a fixed voltage output. They don't do "smart charge" stuff. If you want the TV to put power into the batteries, the DC / DC needs to be set above the "float" voltage on the MPPT. If the MPPT is set to 14.4 for float, then the DC/DC needs to be at 14.5.

Bob
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Old 06-08-2018, 02:56 PM   #11
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Thanks everyone

I've just ordered at Victron Venus GX which I should have Monday. That's just like the Color GX but without a screen. It's Victron's answer to the need to a central brain for all this. You talk to it over the WiFi hotspot it creates.

The Color screen on the Color GX is spiffy but also a royal pain to install (and $200 more) because of all the wires that need to go to it. Since we're trying to leave on our five week trip on Wednesday I'm keeping it simple and mounting the Venus GX down with the rest of the equipment under the bed.

I think without the battery monitor talking to the solar controller the solar controller reverts to some more basic algorithm. I think what it amounts to is it waits until sunrise and then starts collecting energy for the batteries. When it decides they are full (how I'm not sure) it just goes into float (13.5v.) If there are big loads during the day they would have to be so big as to drain the batteries below that threshold before they start charging again. With lithium they could stay there for a long time because of the flat discharge curve. Not what I want to have happen. If we decide to turn on the AC, for example, I'd like the solar supporting the little Honda 2000 generator as much as possible, for example.

To answer the DC-DC questions, I have a 9amp Victron DC-DC boost converter hooked up to the tow vehicle charge pin. It's set to provide a constant 14.5 volts when being towed.

Note that without a central controller there could be a danger of over charging between my 500W solar array and the Multiplus if I was plugged into shore power. Another reason for the Venus GX.

There may be a way to configure everything without a Venus/Color GX to work okay but with the clock ticking on our departure I don't want to mess with it and don't want to run the risk of shortening the life of our expensive battery bank.
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Old 06-08-2018, 03:41 PM   #12
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Hi

A bit of clarification:

1) You have Battle Born batteries. They have an integrated BMS ( battery management system ). One of the functions of the BMS is to charge the batteries. *IT* ( and not the other stuff in the system ) is what keeps the batteries topped off. They do *not* work like lead acid batteries.

2) If your MPPT is going back to 13.5V then you have not configured it properly for lithium batteries. You have to go in and select "custom settings" on the charger. If you do not, then the batteries will indeed cycle quite a bit.

3) You can have the DC/DC *and* the solar *and* the shore power converter running all at once. You will not overcharge the Battle Born batteries. That's why you paid the big bucks for them. They work it all out.

4) Just as with the solar, the charger / converter needs to be custom programmed for lithium batteries. It comes stock from the factory set for lead acid cells. That is not the optimum way to keep Lithium's topped up. Just as with the MPPT, the manual shows the settings for changing the voltages.

So how does this all work?

Something ( anything, solar, DC/DC, shore power) runs the DC bus up to 14.6V ( or whatever you have it set at). If the batteries need charge, current will flow into them. If they don't need charge, no current will flow.

A load comes along. The DC bus drops a bit if the MPPT (or whatever ) can not handle the whole load. When it drops, current flows out of the batteries. They will share the load as best they can. As things run from 14.6 down to about 13.4, you really are not pulling much at all off the batteries. There is quite a way for them to share over.

The BMV 712 tracks current into and current out of the batteries. If you still have it set for lead acid, it will not properly estimate things for a lithium system. There are several things to change around to get it to understand a lithium pack. Again, it's all in the manual and the information on the app. Once it is set up, it will give a pretty good idea what's in the battery. It will ignore minor charge currents ( as it should ).

So, a very cool system indeed. Lots of fun looking at the history chart on the MPPT and seeing how it is doing. You will note that the battery runs up to whatever your max is during the day. It will drop down to 13.4 maybe overnight as parasitic loads pull things down a bit.

Lots of fun !!!!

Bob
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Old 06-08-2018, 04:07 PM   #13
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Hi

A bit of clarification:

1) You have Battle Born batteries. They have an integrated BMS ( battery management system ). One of the functions of the BMS is to charge the batteries. *IT* ( and not the other stuff in the system ) is what keeps the batteries topped off. They do *not* work like lead acid batteries.

2) If your MPPT is going back to 13.5V then you have not configured it properly for lithium batteries. You have to go in and select "custom settings" on the charger. If you do not, then the batteries will indeed cycle quite a bit.

3) You can have the DC/DC *and* the solar *and* the shore power converter running all at once. You will not overcharge the Battle Born batteries. That's why you paid the big bucks for them. They work it all out.

4) Just as with the solar, the charger / converter needs to be custom programmed for lithium batteries. It comes stock from the factory set for lead acid cells. That is not the optimum way to keep Lithium's topped up. Just as with the MPPT, the manual shows the settings for changing the voltages.

So how does this all work?

Something ( anything, solar, DC/DC, shore power) runs the DC bus up to 14.6V ( or whatever you have it set at). If the batteries need charge, current will flow into them. If they don't need charge, no current will flow.

A load comes along. The DC bus drops a bit if the MPPT (or whatever ) can not handle the whole load. When it drops, current flows out of the batteries. They will share the load as best they can. As things run from 14.6 down to about 13.4, you really are not pulling much at all off the batteries. There is quite a way for them to share over.

The BMV 712 tracks current into and current out of the batteries. If you still have it set for lead acid, it will not properly estimate things for a lithium system. There are several things to change around to get it to understand a lithium pack. Again, it's all in the manual and the information on the app. Once it is set up, it will give a pretty good idea what's in the battery. It will ignore minor charge currents ( as it should ).

So, a very cool system indeed. Lots of fun looking at the history chart on the MPPT and seeing how it is doing. You will note that the battery runs up to whatever your max is during the day. It will drop down to 13.4 maybe overnight as parasitic loads pull things down a bit.

Lots of fun !!!!

Bob
When I called BattleBorn, they said to set the bulk charging at 14.5 volts and Float at 13.6 in the Multiplus Inverter. They said to set Absorb time to 1.5 hr.

Where I got confused is when, on a bright sunny day, with the fans and lights on, I had a consistent -8A on the BMV. The MPPT wouldn't kick on to support the load.

I've gone through all the devices and set them to Lithium and set their bulk and float settings to match the Multiplus. I tried an experiment of setting the MPPT Float voltage to 14.5 but it still didn't seem to turn on charging. It does turn on in the morning and charge everything up so electrically everything is working.

wulfraat: This is a huge ask but since you have the same setup as I do once the Venus arrives (except with more solar on the roof and more batteries on board) it would be fantastic to see your settings for everything. Any chance of a series of screen captures? I know this is a lot of trouble so don't worry if you can't do it.
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Old 06-08-2018, 04:41 PM   #14
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MPPT Solar and Lithium Question

Yes glad to send you some screenshotsÖ Iíll head out to the trailer this weekend and crank it up since itís in storage :-)

Did you confirm with a.m. solar or Victron that the MPPT controller does in fact get SOC from the BMV like the multiplus does when networked via the Venus?

Donít forget youíll need VE.direct and VE.bus cables to connect everything
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