Replacing a 40ah solar Controller

[Jon and Kay]

Ok. Might as well ask why there appears to be a very small selection of solar controllers above 40ah.

I have had 700 watt at 17v = 40 ah of solar panels on the roof. As usual the winter sun and inability to tilt these panels has degraded them by 30% and they currently only supply 30ah at best (until we get further North).

So I added another 400w of solar, about 22ah , so the system again supplies 40+ah

So now the PL40 will be underrated in Summer. It is a PWM PL40

I could expand the PL40 by use of a SSR, but this would require me to run extra 10mm2 cables from the controller/ssr to the battery, a distance of 10 metres.

I think changing to a MPPT controller may be a better option. Especially if the controller could be mounted near to the battery, with a remote control in the 'house' This way I could use the current wiring between roof and battery. (higher voltage, thinner wire)

But I cannot seem to find a suitable controller. Any ideas?

[T1 Terry]

You already have the cabling from the solar to the PL40 and from the PL40 to the battery, so why do you need to run more cabling to use the SSR method? You would need to run 2 control wires, but you would need to run that cabling for the MPPT controller to get the remote operation anyway.

T1 Terry

[Jon and Kay]

Hi Terry

The cable from PL40 to Battery is 10 metres of 10mm2 , that carries 40 amps ok, but would have too high a voltage drop at 80 amps

[T1 Terry]

The aim is for the 40amps in winter is that correct? Do you need more than 60 amps in summer? Using the voltage drop calculator http://www.calculator.net/voltage-drop- ... 0&x=47&y=9 and allowing for 16v from the panels in summer, 10mm sq cable is roughly 7awg cable and the 10 mtr run you would still see 14.04v @ 60 amps at the battery end, more than enough to charge lithium batteries.

T1 Terry

[Jon and Kay]

No
No

The aim is for 40 Amps at least, Summer, Autumn, Spring or Winter. But 80 Amps would provide adequately all year round.

The Controller is currently 1 metre from Solar Collectors junction, 10 metres from Battery.

I need 60+ amps in Summer to run the Aircon without decreasing battery storage. I run the aircon all day now, but the battery requires replenishment.

Before adding 400w extra solar, I was down to 27ah from the panels at best. 350ah per day does not cut the mustard.

I am near fully 240v, a full size 240v fridge plus freezer (total 310litres) , 7.5kg washer dryer etc. Every 240v appliance other than fridges is never turned off, started by remote controls.

[BruceS]

I can see your problem.
This is why I went to 48V (nom).
The only problem with doing that is somehow I do still need a few items powered by 12V. (radio, depth sounder etc)
I looked for a 48V to 12V converter but ended up just grabbing a 12V AGM & using the old existing solar panel with an occasional spurt from a 240V battery charger.
Plenty of 48V charger/inverter/solar controllers around and I solve the thick wire problems.
Not sure how you can solve your problem. Maybe 2 chargers to batteries?
Even MPPSolar only have a 800w MAX 12V solar controller from a quick look.
http://www.ebay.com.au/itm/True-MPPT-60 ... SwYmZXELau

[Jon and Kay]

Thanks Bruce

I don't know the answer, but I do know the question.

One supply of 100 volt from the roof at 17 volt....down to a controller nearby the batteries. Send and control a charge to the LFPs.

An MPPT controller ...at say 80 amps is available, but I want to control it in House. I need a remote control like the Plasmatronics has. (PLM)

[T1 Terry]

No
No

The aim is for 40 Amps at least, Summer, Autumn, Spring or Winter. But 80 Amps would provide adequately all year round.

The Controller is currently 1 metre from Solar Collectors junction, 10 metres from Battery.

I need 60+ amps in Summer to run the Aircon without decreasing battery storage. I run the aircon all day now, but the battery requires replenishment.

Before adding 400w extra solar, I was down to 27ah from the panels at best. 350ah per day does not cut the mustard.

I am near fully 240v, a full size 240v fridge plus freezer (total 310litres) , 7.5kg washer dryer etc. Every 240v appliance other than fridges is never turned off, started by remote controls.

You will not get 80 amps from 1100w of solar no matter what controller you use. I have proved to anyone who will watch the test that an SSR controlled by PWM provides more amps into a lithium battery than an MPPT controller, even Julian admits there is more output via direct connection via an SSR.
Look at the calculator Jon, the size cable you state as 10mm sq equals 7AWG, the length is 10 mtrs, or 11mtr now, little difference, the supply voltage is 16v or greater so we will go with 16v, at the end of the 11mtr there will be 60 amps @13.84v, that is plenty to drive the inverter to power the air con.
It's all in how it is wired up Jon, you can spend your $$ on a top of the line MPPT controller if you want, it's your money, but you won't get anything like the 80 amps you are expecting.

T1 Terry

[jon_d]

Jon,

My plan is;

MPP 5048 http://www.mppsolar.com/v3/pcm50488048cx-series/

2 banks of three 37.5V OC 200W panels giving close to 114 V being converted down to 24V feeding AGM's.

Same as you, this is to power the AC directly and top up the batteries (between AC cycles) when/if they are drawn down.


I note my plan was hatched years ago and parts have been purchased over that time... so I'm locked into it. It will be interesting to see how the controlled performs.

[Jon and Kay]

Hi Terry

I am acutely aware that the current solar will not supply 80ah. I am providing for future proofing, i.e. adding another 400 watt of solar at a future time. (sometime this year)

In the mean while the 80 amp system should supply 60ah now. It still has to be able to supply 80ah when the next panels are added.

Jon_D, If I had my time again......Then I would use high voltage solar with individual MPPT controllers.

I may just have to duplicate the cabling from controller/ssr to the battery, and stop mucking about.