Parallel 2 pwm (c40) charge controllers from single source array.

[danda]

Presently I have two solar arrays, each feeding its own c40, which are both connected to a single large forklift battery (48v).

so far, so good.

Under certain conditions, the controllers are handling a bit over 40 amps and on a hot summer day, it will reach overtemp and shut down for ten minutes to protect itself.   working as designed.   I even put an external fan blowing over the heat fins, and it still happens.

Now, I happen to have two c40 spares.

I am wondering what would happen if I ran each input array through 2 c40s instead of a single one.

So it would look like:



My questions are:

1. Has anyone tried this, and if so what was your experience?

2. Would this work to effectively reduce/halve the amperage flowing through each charge controller?

3. Any solid reasons NOT to do it?

[SparWeb]

In a word, No.
Each C40 regulates the current by switching on/off thousands of times per second.  For two C40's to do this in parallel would mean that on some cycles, one switches off, shedding all of the current to the other, and vice-versa.  Since this will be a confusing condition I have no idea if each C40 would respond appropriately.  In any event, it wouldn't solve your problem - each C40 would still be seeing in excess of 40 amps during the "on" cycles.

What about splitting the panels into 3 or 4 arrays?  You must have some panels in parallel, because that's the only way I think you can get 40+ amps out of any typical array of panels.  The groups don't really have to match, despite what the purists say.  Your collection of C40 charge controllers would be happy with that.

[joestue]

the only way to do that is convert the c40 into a buck converter. the problem being.. it wasn't designed for that.

[danda]

In a word, No.
Each C40 regulates the current by switching on/off thousands of times per second.  For two C40's to do this in parallel would mean that on some cycles, one switches off, shedding all of the current to the other, and vice-versa.  Since this will be a confusing condition I have no idea if each C40 would respond appropriately.  In any event, it wouldn't solve your problem - each C40 would still be seeing in excess of 40 amps during the "on" cycles.

Ok, this makes sense to me.  Thanks for spelling it out.

I do still wonder... I would think there probably exists some sort of device that can split current into two streams.   Don't computer power supplies do something like this?  If I had such a device, then it could be installed before the charge controllers.   Can anyone tell me if such devices exist and if so what are they called?   (just curiosity at this point)

What about splitting the panels into 3 or 4 arrays?  You must have some panels in parallel, because that's the only way I think you can get 40+ amps out of any typical array of panels.  The groups don't really have to match, despite what the purists say.  Your collection of C40 charge controllers would be happy with that.

Yeah, that is a possibility.  But I already have all the wiring buried and it goes into two combiner boxes and then into underground conduit to the 2 (indoor) charge controllers.  It would be a headache to change, and also I oversized the wiring from the combiner boxes to handle 60+ amps for each array.

For now, I've bitten the bullet and bought a morningstar ts60.   With it plus a c40 I can handle 100 amps continuous, which is adequate for the panels.

[SparWeb]

It seems we all end up with spare C40's eventually... I have an extra too!

[Mary B]

C40's make good diversion controllers!

[camillitech]

Sorry to disagree chaps but I've been running 4 Morning Stars in parallel for years. Well it's actually been 2 x 2 in parallel in Diversion mode and it's worked just fine. I did not do this off my own initiative but was told it was the best way by 'one who knows' and has been selling MS TS40's since 'Adam was a lad'.

Cheers, Paul

[joestue]

Well it's actually been 2 x 2 in parallel in Diversion mode and it's worked just fine.

well, that is why.

question i have for you is what exactly is going on? do you have two morning star's driving a single load resistor? or does each one have its own resistor?

[camillitech]

I have two in parallel set to diversion driving a 3.6kW immersion using Hugh Piggott’s TriStar follower circuit (see his website for details). Been running two of these with the second one (pair) set at slightly higher voltage via the dip switches. I also have another 48v forklift bank with two Tri stars one set to diversion driving air dumps with second one set to charge control at a slightly higher voltage. They have all been operating flawlessly for years now. Maybe I am just lucky

[SparWeb]

Well, yes, 2 in parallel on diversion loads would be just fine...

But that isn't what the OP asked about. 

[camillitech]

But that isn't what the OP asked about.

Perhaps he should have 

[camillitech]

Well it's actually been 2 x 2 in parallel in Diversion mode and it's worked just fine.

well, that is why.

question i have for you is what exactly is going on? do you have two morning star's driving a single load resistor? or does each one have its own resistor?

Each pair of charge controllers drives one immersion via an SSR https://lifeattheendoftheroad.wordpress.com/2016/10/22/an-off-grid-journey/ and if the thermostat opens it diverts to DC air resistors at least I think it does  It's a long while since I installed it and it has worked so well. Not only that but I'm well into a bottle of vodka and it has been a long day 

[camillitech]

Perhaps Hugh's blog will make it clearer http://scoraigwind.co.uk/tristar-follower-to-control-ac-heaters/ 

[clockmanFRA]

'camillitech' is correct regards the Morninstar Tristars.

I have 5off Tristar's runing since 2007 and all set for diversion control.

I did try C40's but they are just not fast enough switching for my wind turbines they seem to lag slightly.

Morningstar products sure are good high quailty and certainly withstand the work i give them.