Man This solar thing drive me nuts. help

[paulcheung]

I just went to the control room to observe something, What I see is not make sense to me. Please help me to understand it.

I have two outback FLEXmax 60 amps charge controller. one Magnum MS4448PAE 4400watts inverter. 8 Rolls 4000 series S460 6volt batteries wired in 48 volts system.

The two outback CC have it's own solar array only connected to the common battery bank.

What I see today is that one CC read in 125volts and ~6amps and out 54.9volts 13.33amps status charging is float.

the other CC read 92volts ~10 amp in and out 54.9volts 19.5amps. the inverter is inverting 40amps at 54.2volts.

When I turn off the second CC the first one jump the amps to 33amps and if I turn on backthe second CC, the first CC go back to 13.3 amps.

This don't make sense to me. The inverter is drawing 40 amps to convert the watts to the house and the two CC controllers is not product more than the current the inverter draw. so why is the first conntroller limit it's currents? the two of them is push out 33 amps, 7 amps less than the inverter draw. yet when I turn off the second CC, the first CC push 33amp by it self. so it is limit it's current flow. Can someone tell me why?

Thank you.

Paul from the Caribbean Island

[inetdog]

This don't make sense to me. The inverter is drawing 40 amps to convert the watts to the house and the two CC controllers is not product more than the current the inverter draw. so why is the first conntroller limit it's currents? the two of them is push out 33 amps, 7 amps less than the inverter draw. yet when I turn off the second CC, the first CC push 33amp by it self. so it is limit it's current flow. Can someone tell me why?

Thank you.

Paul from the Caribbean Island

The only thing that makes sense of this to me is that the battery voltage is such that both CCs, individually and together, think that the battery needs to be charged in Absorb or Float and that voltage at the inverter terminals is not high enough to send more than 33A to the batteries. I would look at the battery voltage with no load or charging, then with only CC connected, only inverter connected and then both.

It might also be that there is too high a wire resistance between the CCs and the battery terminals. But this guess would only apply if the two CCs shared a length of wire to the batteries. Otherwise you would be able to get more current from the two together than from just one.

[thastinger]

You may have been looking at some spike type draw. No way you're drawing 40 amps out and putting 33 amps in or you wouldn't be staying in float, you would be in bulk.

[Mike90250]

Do you have a synchronizing cable or hub between the two charge controllers ? Without some method of sync'ing them, minor voltage sense differences between them will always have one lag behind the other.

[inetdog]

Do you have a synchronizing cable or hub between the two charge controllers ? Without some method of sync'ing them, minor voltage sense differences between them will always have one lag behind the other.

But that would not cause the sum of the currents to be limited to less than the two arrays can produce and the batteries can accept. If only one CC was providing current, it could be the capacity limit of its array, but the OP says that both CCs are contributing.

[paulcheung]

The first controller has 12 panels and the second controller has 8 panels. the panels wired 4 in a series. I have seen the first panel put out more than 55amps and the second panels put out 28 amps. something is wrong between the inverter and battery and the controllers. when I turn off the second CC, the first one jump to 33amps out put. when I turn on the second cc it drop back to 13.33 amps make the total sum 33amps. but yet the inverter draw 40amps. so even if the battery is fully charged, the load should release the resistance if there is any.

Thanks. I need to forward this problem to outback techs.

[Sunking]

Thanks. I need to forward this problem to outback techs.

I do not see a problem. What you are seeing is a system operating with fully charged batteries.

[paulcheung]

I do not see a problem. What you are seeing is a system operating with fully charged batteries.

Hi,
Yes I understand what you saying, but the inverter is still drawing 40 amps. it is 7 amps greater than the two controller put out together. yet the two controller can put out more. I understand if the two controller put out same 40 amps as the inverter draw. but it short. Can you make me understand?
Thank you.

[thastinger]

Hi,
Yes I understand what you saying, but the inverter is still drawing 40 amps. it is 7 amps greater than the two controller put out together. yet the two controller can put out more. I understand if the two controller put out same 40 amps as the inverter draw. but it short. Can you make me understand?
Thank you.

Paul read my above comment and listen to what you're saying...you're saying that you are drawing out 7 more amps than you're putting in but somehow manage to stay in float mode. That can be true but only for a short period of time, if it continued then your CC would enter a rebulk charge mode. Sounds to me like you don't know your system very well yet.

[paulcheung]

I think I forget to mention it is only the first CC stay in the float mode and the second one was at bulk mode. What I don't understant is why the two CC don't push out more or atleast the same amount amps the inverter draw.

[Sunking]

I think I forget to mention it is only the first CC stay in the float mode and the second one was at bulk mode. What I don't understant is why the two CC don't push out more or atleast the same amount amps the inverter draw.

Two reasons.

1. Mainly the two systems are not the same power, so they cannot be the same current.
2. You do not have the sync cable installed to allow them to communicate.

Paul nothing is wrong, the system is doing what it is suppose to. The problem is you do not understand the system is not capable of doing what you want, and is under sized. Really not much more we can do for you. If you do not have a generator I suggest you get a battery charger to get the batteries charged up and quit using them.

[inetdog]

I think I forget to mention it is only the first CC stay in the float mode and the second one was at bulk mode. What I don't understant is why the two CC don't push out more or atleast the same amount amps the inverter draw.

Very simple: Either the two CCs are not seeing the same voltatge because you have wiring problems or they are set to different voltage points. You may be able to get close to what you want by using separate battery sense leads from each CC to the battery and experimenting with the set points to get them to behave similarly.

Or else you need to allow them to communicate so that when the master unit is in bulk mode it will try to put the other unit in bulk mode too to deliver more power to what it thinks is just the battery.

The problem with the latter approach is that the master CC will think that all of the current is going into the battery and so may be limiting the total based on what it thinks that the battery can tolerate.

Trying to get the most out of your solar panels when running a sizable DC load compared to the nominal charging current of the battery will require a much smarter set of CCs than you have. The upcoming product from Midnite Solar, which can incorporate a battery shunt so that it knows exactly were its output current is going, stands a good chance of doing what you want. But it is not available yet and will not be cheap.

[Sunking]

The upcoming product from Midnite Solar, which can incorporate a battery shunt so that it knows exactly were its output current is going, stands a good chance of doing what you want. But it is not available yet and will not be cheap.

How did you hear about that? They are being pretty tight lipped about it and only a few dealers have the inside story. Did they leak it already?

[inetdog]

How did you hear about that? They are being pretty tight lipped about it and only a few dealers have the inside story. Did they leak it already?

They have actually admitted that they were exploring it on other Forums and discussed its advantages (on threads started by others on related CC topics) while being totally tight lipped about any time schedule or details.

That is the only hard fact behind my post, the rest is SWAG. But thank you for the confirmation.

[Sunking]

That is the only hard fact behind my post, the rest is SWAG. But thank you for the confirmation.

I do not know a whole lot. Just some conversations I have had with an Tech Rep and an Engineer I have become friends with over there.

I am a little bit surprised it has taken this long and only one company venturing into it. Power management has been around a long time in Telecom, Utilities, and home automation. We use it a lot in Telecom and Data centers to mange battery plants and energy cost. You see a little bit of it in grid tied systems like Enphase as an example. But that is more Bells and Whistles rather than active control.