Make output limit dependent

[dogfox]

Hi guys,

Just had a thought about harvesting power a bit more efficiently..

I currently have a bit over 5000w of solar being regulated by two devices.  I have a bit over half going to an apollo t80 (purchased before I was enlightened) and the balance going to a classic 150.  My battery bank is 1600ah in 24v config that can safely accept 93 amps (10% of c10).

I have both regs limiting output amps so i dont go significantly above the battery input charge limit..

My thought was.. can the classic be made to limit battery input amps as apposed to regulator output amps.. In order to take into account big loads such as pool pumps or ac units.. 

If it can already - please share the knowledge. 
If it can not, is it theoretically possible? what can I do to help

Cheers

[ClassicCrazy]

I don't get why you want to limit battery input amps . And how is that different from the controller output amps ?

The Classic will supply the power to the big loads if available from solar - and it is not going effect the charging current. For example if the Classic is regulating charging to 10 amps and you suddenly have a load of 30 amps dc  - the extra 30 amps will basically go right to your inverter . The Classic will still maintain the 10 amps charging current - depending on what state it is in . If it is in Absorb then unless the voltage drops because of the load , then the Classic will supply the 40 amps ( if available) 30 to load, 10 make it to battery.  If you have your amps output on the Classic restricted below 40 amps lets say to 30 amps - then you will only get that much out.

Larry

[zoneblue]

As its understood, Midnite has that feature on the drawing board. But it has been there a while and it sounds it may be another year....

[boB]

What he means is to be able to limit the current going INTO the BATTERY instead of the current
coming OUT of the MPPT controller because that current coming out of the controller does NOT
all go into the battery....    That is, unless you didn't have any DC loads like an inverter etc...

But I suppose there wouldn't be any need for a battery bank if you didn't have any loads
to such down the battery.

This limit would be done by way of the Whizbank Junior battery shunt sensor that could
tell the Classic when to limit its output current.    This feature all by itself is pretty easy
actually EXCEPT that if there are more charge controllers in the system, it won't be
as easy to communicate that information to all of them and have them all limit
proportionally.  It's not all that hard either but that is what would take the majority
of the work.

Also, since you have the Apollo TS and the Classic, I suppose the Apollo could just do
all that it can and let the Classic limit itself as long as the Apollo doesn't charge higher
than you want.

That being said,  this feature should come some time. 
I just can't say exactly when.

boB

[dogfox]

Thanks boB,

What you describe is exactly what I was suggesting..  I would think that the wizbang jr would be installed in between the charge controllers and the batteries so it would 'see' the current going in and have the classic adjust as it sees fit.  In my case, the T80 would not be able to limit based on output from the wizbang jr (unless I could get the Apollo people to work with you guys - not likely).  The Apollo does have aux in/outs but I don't think they are proportional inputs to use with an output ignal from the wizbang/classic.  I'll have to dig out the manual.

Anyway, thanks for the info and Im looking forward to what you guys come up with next

Cheers

[binkino]

Have the same issue and waiting for this function
see my posts ...

Big thumbs up, when this function will be included!


On my system I have 48V 230Ah battery bank and must limit the Classic to 23 Amps because the 10% charge max.
But it the classic sould be able to deliver more amps and I have the load, the classic can not "see" this and will not give more then these 23 Amps.
If I don't cut it at 23 Amps it would cook my batteries with more then 30 Amps in best sun.

[ClassicCrazy]

Have the same issue and waiting for this function
see my posts ...

Big thumbs up, when this function will be included!


On my system I have 48V 230Ah battery bank and must limit the Classic to 23 Amps because the 10% charge max.
But it the classic sould be able to deliver more amps and I have the load, the classic can not "see" this and will not give more then these 23 Amps.
If I don't cut it at 23 Amps it would cook my batteries with more then 30 Amps in best sun.

If you put in more than 23 amps doesn't the voltage rise quickly , putting it into Absorb, and then it regulates the current down ? It won't always put in maximum current when in Absorb .   Are they flooded lead acid batteries ?

Larry

[zoneblue]

Yes, the 0.1C "rule" is not inviolable. However the higher you go the bigger the risks, and if things go wrong the bigger the mess. Hence 0.1C is a good place to be for FLA. For AGM you can go to 0.2C comfortably, and in certain good quality brands even higher. However watch the temps and make your own (informed) call about it.


Or... get into lithium and charge away to your hearts content.

[ClassicCrazy]

Zoneblue - just looked at the write up of your system . That is an excellent review of the Classic .

What kind of lithium batteries are you using ? I think I only saw AGM in your write up.

Larry

[zoneblue]

The AGMs are still going. Now three years old. Next bank will be lithium.
Still trying to "finish" the install. Combiner, SPD, AXS, and tidy up all still sitting in the corner.

[ClassicCrazy]

Nice neat looking job on that zoneblue .

[binkino]

Here is my post to this topic:
http://kb1uas.com/mnsforum/index.php?topic=2555.0

I am just actualy in the situation, that this function would be more then neccessary.

I had problems with my 230Ah AGMs and brought them today to the dealer for meassuring/testing.
Because one again failed in its capacity and I also let them check the other two batteries.
One was changed some weeks ago.

So, as I am "off grid" most time thanks to the midnite, batteries and inverter.
It is impossible to drive the charger with the inverter without batteries, but I see no sense to "waste" the energy

So I take the old 27Ah batteries from my e-scooter (like these 50ccm scooter, just electric) and connected them to the system.
Yes, I know with 27Ah I don't get the big price - but it is better then nothing and on day I can feed my home with energy instad of paying for the energy.

So the situation, they are rated by max. charging of 5 amps.
If I set the classic to 5 Amps, it will rise and fall with the volts, switches from and back between grid and batteries.
So I had to set to 10 amps, hope the inverter will need enough energy, that the batteries are not blown.


So you see, it is more then importand needed to have a function, that watches the charging current and regulate the amps.
Specialy today I am very sad about missing this function. I can not sit here all the time and regulate all couple of minutes the amps manualy. (also the changed amps in the classic settings are not in real time changed... takes a time... why?)


So hope you all understood the situation ,,,, and my english ... once again ;-)

[ClassicCrazy]

My advice is if you need to get new lead acid batteries to replace old ones - ask if you can get flooded instead of AGM . They are longer lasting and you can do maintenance and check the specific gravity on each cell  to make sure all is well.

Larry

[binkino]

yes thanks that is right, today I know this all ...
the thing was in my situation, there were AGM build in from this untrustworthy company and (see my story on www.a68k.de/pv/ but it is in german)
and after I found out that 2 batteries are 'dead' I had to get very quick new batteries and it was most the money thing
Sure, the next batteries will be either OPzS or like that, or something better - but next year.
Meanwhile we watch the battery market, whats new and coming on


But I do not give up the hope (we say, the hope is dying at last) that we can have this function

[australsolarier]

maybe you should get lifepo4 batteries. they take a much higher charge and can be discharged lower.