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Voltage configuration in batrium
#1
Hi again,

i want to use my packs 100p 14s in the voltage range from 3.3 to 4.0 Volts. Does it make sense to configure these voltages in batrium itself? Or would it make more sense to configure batrium in the full voltage range 2.5 to 4.2 volts and let the inverter just start and stop between the desired 3.3 to 4.0 volts? What do you think?
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#2
The charge controller should be configured slightly higher than the voltage you have set in the Batrium for balancing to begin, otherwise it will balance constantly and significantly shorten the lifespan of your longmons (I assume you're using longmons?). For the cutoff voltage, it is safe to configure that in either the Batrium or Inverter. Please note that the longmon datasheet states the lowest operating voltage is 2.20V. In my experience, they tend to get a bit funny before then, like around 2.30V or 2.35V.
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#3
I don't understand. I thought balancing only happens when a certain voltage is reached. So if the charger is configured to max 4.0 volts per cell and batrium is configured 4.2 volts shouldn't there be any balancing at all?
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#4
(10-14-2019, 10:01 AM)Maniac_Powerwall Wrote: Hi again,

i want to use my packs 100p 14s in the voltage range from 3.3 to 4.0 Volts. Does it make sense to configure these voltages in batrium itself? Or would it make more sense to configure batrium in the full voltage range 2.5 to 4.2 volts and let the inverter just start and stop between the desired 3.3 to 4.0 volts? What do you think?

I see the equipment roles like this:

1) Charge Controller - this is where you set max charge (3.9v/pack or 4.0v or 4.1v etc).   
2) Inverter on/off can initiated in 2 basic ways - i.e. 2a) let Inverter do it based on its own voltage range or 2b) use external equipment secondary feature (such as Charge Controller auxilary relay or Batrium relay) to control on / off based on voltage or other criteria.
3) BMS (Batrium) - monitor cell/pack level voltages, initiate balance, initiate critical event shut-down, control external operations (such as fans).

You set these things in 'cooperation' with each other, but I don't see Batrium as the 'master brain'...   a Charge Controller is too good at its job - i.e. max voltage charging (bulk, absorb, float).   Inverter on/off uses the battery bank to produce power *simultaneously* with charging and balancing - i.e. its a cooperative operation.   Batrium's primary function is to monitor/protect and balance the battery bank and secondarily to initiate external events such as shunt-trip to disconnect the battery in an emergency or turning on fans for extra cooling.

Back to balancing... you things to work in cooperating with the voltage range that you want to work with. Let's say you choose a max of 4.0v (Charge Controller role) and the inverter comes in somewhere in that range and shuts off at 3.3v by itself, then you have a 3.3v -> 4.0v range. You can set Batrium to balance at the top of that range (say 4.0v) OR you can use auto-level and initiate a lighter touch balance anywhere in that range or do both.

Let's say you decide on top balancing only with 4.0v goal - and you set the Batrium to balance at 4.0v and Charge Controller Absorb/Float to 4.0v... BUT you find there is a slight voltage difference between equipment and Batrium sees 3.9v and never gets to 4.0v even though the Charge Controller says 4.0v. Then you can back off the Charge Controller a tenth of a volt and see if that works the way you want. Its typical to 'fine tune' things a bit. Its also OK to change your mind from week to week as you see how things work. For example, a 3.3v low is pretty low and you might find that 3.5v low (just ahead of the discharge curve knee) is better.
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#5
Ok so you would prefer to set both in the same voltage ranges? Charger and Batrium? You use quite similar voltage ranges right? 3.5 to 4.0? How is your batrium configured?

Thanks alot for the explainations...
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#6
I made a personal decision to operate at a maximum high of 4.0v  and a daily/deliberate low of 3.5v  (inverter off).    I have a 14s (48v nominal) 18650 battery bank.

The high of 4.0v/cell is set/controlled by the charge controller -  absorb = 56.4v (4.03v/cell) and float = 56.3v (4.02v/cell).   

The inverter is turned on/off by an auxilary relay feature of the charge controller.  When the battery voltage reaches 52.0v (3.71v/cell) the relay is turned on - which turns on the inverter. I can set this to any value I want in the charge controller interface.

The low of 3.5v/cell is enforced by turning off the auxilary relay at 49.5v (3.53v/cell) - which turns off the inverter. I can set this to any value I want in the charge controller interface.

Because I chose 4.0v maximum  the charge controller enforces this, and in my case I don't need or want to balance on a daily basis, I set the Batrium just a little higher - at 4.05.   This avoids top balancing.
See "Bypass Volt CV9 [ 4.05]  v"  on left column


If you choose my voltage range as your operating guide, you could set Batrium at 4.00 or 3.97 or something like that to kick off balancing at the max of the charge cycle. You should experiment and see what works best for you by adjusting this setting.

However...  on most days I never reach the maximum.  My system is designed to use PV power during the day as much as I can to limit the battery DOD.  On average I only reach 3.8v/cell as the maximum  so in that case, if it wanted to do balancing, I would have to set Batrium to 3.75 or something like that so that 'on average' the balancing would kick in.

------------------------
From your comment, I still sense that there is confusion about things.   Please note that the Charge Controller does not do a 'range' of voltages... its only concerned with the top or max voltage.   The bottom of the range is typically where your inverter shuts off or the load shuts off - so its the inverter off function or process is the point that sets the bottom voltage.

Batrium doesn't set or control either the top or the bottom voltage range - but rather monitors the whole thing and it might throw shunt-trip on over voltage or under voltage or might turn balancing on at a certain point in the range - but that's not the same as controlling the top and bottom.     Note: There's a lighter version of balancing that you initiate mid-range called Auto Level, but that's an advanced topic and we can take that up once you get the basics in place - and there a nice youtube on it by @Daramor

IF your charge controller does not have the ability to turn your inverter on/off at a custom voltage range and your inverter is not settable, you could do this thru expansion board of the Batrium - like turning a fan on/off based on temp, you could turn the inverter on/off based on voltage. Or you can just live with the bottom voltage that is native to your inverter - its OK as long as that's within your design goals.
Headrc and Sleonard2649 like this post
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#7
I got a PIP5048GK thats why im wrote charger and voltage range, that's wrong of course. I should have talked of an inverter. As soon as i got the system up and running a lot of things will be clear for me. For now i just want to get a good base to start. Thanks again for explaining i think i got my answer.

So best configure both Batrium and Inverter/charger to my desired voltages.
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#8
Bypass voltage should Always be above too voltage set at the inverter.

IF you need balancing a bit eatlier you need to look at autolevel instead. That One can be configured based on volt, Soc and or current.

Check My video about at it.

Generally you should never need to balance that often so top voltage bypass or very sparse auto level is enough. I havent balanced any of mine in like 4 weeks and not an issue.
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#9
Thanks I thought it had to be that way, eiher I didn't understand the first reply or it was wrong.

@Daromer how would you configure Voltages? Full range in Batrium 2.5 to 4.2 and inverter 3.3 to 4.0 volts? Or both between 3.3 to 4.0 volts?
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#10
Your batrium gear should:
- balance (use auto balance above 80% SoC + bypass at or just above 4.0),
- trigger charger cut off on out of spec high cell V, eg >4.2V/cell,
- trigger inverter cut off on out of spec low cell V, eg <3.0V/cell,
- trigger charger & inverter stop on loss of cellmon comms,
Your charger should charge (CV) to pack voltage of 56.0V (=4.0V/cell per your values) hold it there and stop when current has dropped away.
Your charger can also float the pack at 56.0V or just under (as you have margin to 4.2V cell).
Your inverter should low voltage cut off at pack voltage of 46.2V (3.3V/cell per your values).

Optionally you can set the Batrium to start cooling fan when bypassing.
Running off solar, DIY & electronics fan :-)
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