Lithium users

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VanKitten

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So, I have encountered an issue.   This is something every lithium user must have figured out.....  so,

    The BMS has a few functions, one of which is to disconnect the battery positive side when the discharge falls below a certain level, or when the charge reaches the top defined level.   This is to protect the battery.   This is an automatic function.

So..now, the solar charge controller enters the picture.  

The installation guide is quite specific that cutting the battery side positive before FIRST disconnecting the solar array will damage and possible destroy the charge controller.

Ok..how do I solve this?   The BMS has no connection nor access to the array side of the mppt.    Turning the battery positive off in the event of reaching max charge is a totally normal thing.  Will happen routinely.

My system is 400ah   60amp max from the solar array.    

It is obvious that the Morningstar mppt I have will not be a workable one for this system.

Other lithium users...how did you solve this?
 
Yes, I read that whole thing. So, I get that something, possibly additional hardware, is needed.

I am asking what other lithium users have done in Their systems as the work around.

Or...did they find a different solar charge controller which has the internal safety mechanism to shutdown.
 
Disconnecting or connecting the battery from the controller first or last makes no difference to the controller. The advice is do to a safety issue, and is to protect the operator. Our van mounted solar systems would be hard pressed to reach that much power. I can't speak for cheap-china-doll controllers. They are better off gone. I did talk to renogy and morningstar.
 
Might want to rename this thread "Lithium BATTERY" users...
 
Yes...lithium is batteries. I don't think the word lithium is used in reference to anything other than lithium batteries.

The BMS performs this function completely automatic. When max charge is reached...it shuts off the charging. (Disconnect + side battery) The issue seems to be that the Morningstar (and others) cannot be shut off while still connected to the solar array. No operator involved in that, all automatic.

Since the BMS does not have contact with or control over those cables coming down from the roof...how is this supposed to work?

Anyone running their mppt through their inverter/charger? Someone suggested that. Crazy idea? Well, I don't see how that actually helps....but...
 
Lithium medication is used for treatment of mania. Separation from lithium ion batteries should also be made?
 
If the BMS shuts off the charge into the battery, it really does that one cell at a time until they are all the same charge, but the controller does not care. The charge just stops at the battery management. Again. The controller does not get damaged. Nothing melts. The current from the panels will get dumped to a heat sink. But the controller should be sized to handle the few amps involved. Mine handles 45 amps. My panels are 30 absolute amps if every sun beam is perfectly converted. That is doubtful.
 
Weight....what mppt are u using?

And... no, my battery management cuts off the actual cable supplying the battery.

60 amps from the roof...if everything is perfect
 
I'm somewhat ignorant on this subject. But I have two 100 ah lithium batteries and a Morningstar controller. When my batteries are fully charged, my breaker trips and the controller shuts down. I think your question is how to do this? Buddy' RV in flaggstaff installed my system. They are very knowledgeable, I'd suggest giving them a call.
 
BMS should be final protective layer in OVD /LVD, last resort, not used for daily operations.

The other devices should be set so BMS only kicks in if they fail.

SC should go to 13.1 Float at 13.8V, minimal Absorb even none, long before the BMS OVD is triggered.

A good SoC meter with switching relays can open the panel circuit, set at say 14V, BMS could be at 14.2V.
 
I charge Lithium with constant V.

If the maximum panel Amp output is less than the maximum input current allowed into my Lithium batteries, why not let the panel apply its maximum current as long as the battery V Max is not exceeded?

I would not go into the shoulder zone of the battery maximum charge V.

For LiPo and for Li-Ion I limit the cell to 4.0 V.
 
Ok...

Let's try this from that angle

Is this problem unique to Morningstar? If this is just an issue with the Morningstar..I will get a different manufacturer product.


I have a system where the disconnect between the batteries and the mppt is the actual cable itself being turned off.

This is because the system size is too large for the BMS circuit boards available to deal with. I wrote about this somewhere else. But, the three basic functions of the BMS are handled separately.... I use a contactor to shutdown charging (both from the mppt and the inverter/charger when in use...some day there maybe an addition for wind turbine and/or a generator). I run all this then a power bar capable of handling 400amp. The contactor shuts the power off between the power bar and the battery when the max charge is achieved on the batteries. This is normal operating. I'll post a picture below
 
IThis is the board .   I wired it on the table first...then attached the inverter/charger and batteries once it was mounted.....

Since I have multiple Charge sources...I run it all thru the "charge" power bar
Since I have multiple load sources...I run all of it thru the "load" power bar

Since the inverter can be either...I put a manual switch in place ... than I should the switch at the bottom left side...

So basically..it is two relays. One to cut off at max charge. One to cut off at low charge


photo.JPG
 

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Kat, let me ask you this:

Would it be possible and/or feasible in your system to put a small inexpensive 12v* lead-acid battery in parallel with the lithium batteries, but NOT switched by the contactor (continuous load) ...it would always be presenting a battery source to the controller even IF the lithiums are dropped offline.

The mppt controller should be happy with that.

It might make the battery gurus cringe, but it seems to me it might be one solution.

Shields UP!

Fire away guys...find fault with this answer, if it wont work, tell us why...

:huh:

(* if the system is 24v or 48v, use more batteries)
 
I cannot imagine where I would find the space for it....but aside from that...how would it get charged? The Mppt has one connection to battery +. That will be connected to the "charge" power bar. That is a 4 gauge wire.

Do you mean to splice a second wire to it and branch ... one to the power bar, one to a 12v battery...somewhere? What would happen to it if lithium charging is off and everything is being dumped into it? Mppt would be set up to throw the max output all the time...no float, etc

I get what you are thinking. But..how does it mess up the lithium batteries?

Simplest answer is. Is there an mppt controller without the fatal flaw that Morningstar has?
It is an inherent part of any mppt controller....or a design mistake by Morningstar?
 
My first suggestion would be to call Morningstar and ask if that would or might work...otherwise its a moot point.

And Morningstar probably did all the design work before the lithium batteries ever hit the market.

But yes, you would run a new cable from the output lug from the controller to the new battery positive. Attach it at the bus bar or controller side of the contactor.

It could be a small lead acid. My concern and the one that will probably be pointed out is that this new battery will probably NOT see its optimum charging algorithms...but who cares...its there to do one job only: Present a battery source and load to the controller.

If the BMS cuts the lithiums, and it is night time, AND you have a substantial load on the LOAD terminals of the mppt unit, the small new battery  would quickly become depleted. But, moving heavy loads off of it would fix that.

A small lead acid battery would be less than $50...and the lithiums should remain fat dumb and happy.

Or, run a cable all the way to the starting battery and use THAT one....
 
Call it sacrificial, make it cheap only combine while charging, NP.
 

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