Lithium & other advice/facts

[KevKim37]

Terry,

I already have a Shunt/PLS2 setup and 520watts Solar but I would like to know are the extra panels inputs/outputs set up with the relay, configured through the PL20 to combine the readings with the the original panels already connected to the PL20. In other words what I am asking does the PL20 store and record both sets of panel readings. Your assistance greatly appreciated.

Cheers Kev.

[T1 Terry]

If you are happy with your purchase of an MPPT regulator then that''s fine, none of the ones I've trialed have been able to outperform the PWM controller over the whole days charging. I modified one of my domestic 24v panels to create 2 x 12v panels and it out performs the 24v panel through an MPPT controller.
It's a bit better for the MPPT controllers when high loads are placed on lead acid batteries as there is a larger difference in voltages 11v to 15v but with the lithium batteries the charging voltage range is between 13.2v and 13.8v, the Vmpp of a panel working in full sun is about 15v, just not enough to be gained with a max of 1.8v differential, the power used by the MPPT controller to convert from 15v to 13.2v has to come from some where, add that to the issues with them being incompatible with any other charging system on the same battery it just rules them out entirely in my books, they just aren't true value for money to me, another panel bought with the money saved will give a far better outcome.
Horses for courses, as long as people who are buy them have their eyes wide open and are not conned by the promise of a 30% increase in output and they fully realise it's 10% at the very best and still only for half a day then they have made a judgement call that only they can make.

[T1 Terry]

Terry,

I already have a Shunt/PLS2 setup and 520watts Solar but I would like to know are the extra panels inputs/outputs set up with the relay, configured through the PL20 to combine the readings with the the original panels already connected to the PL20. In other words what I am asking does the PL20 store and record both sets of panel readings. Your assistance greatly appreciated.

Cheers Kev.

Yes, it gives a combined reading and if you hold the button in for a long push in the charge window it will split between what's going through the regulator and what's going through the shunt.

[bob r]

if the pl20 will handle 360w without modification
I will go that way thank you for the advice everyone

[Pokey]

It's a bit better for the MPPT controllers when high loads are placed on lead acid batteries as there is a larger difference in voltages 11v to 15v but with the lithium batteries the charging voltage range is between 13.2v and 13.8v, the Vmpp of a panel working in full sun is about 15v, just not enough to be gained with a max of 1.8v differential, the power used by the MPPT controller to convert from 15v to 13.2v has to come from some where, .....

You miss my point here Terry. With my MPPT controller I am running 24V panels and can run them in parallel/series say, 4 x 250W panels run as 2 & 2 producing 500W @ 48V (nom). The MPPT controller is perfectly capable of using that very efficiently to charge at the 13.2V - 13.8V that the Li batteries require, just as efficiently as it can a lead acid battery at 11V. Given that the Morningstar reg can be purchased as cheaply as the PL20 their is the benefit of a) cheaper domestic 24V panels and b) ability to use lighter cable without any increase in voltage drop or the same size cable with a decrease in voltage drop thus being either cheaper or more efficient.

Horses for courses, as long as people who are buy them have their eyes wide open and are not conned by the promise of a 30% increase in output and they fully realise it's 10% at the very best and still only for half a day then they have made a judgement call that only they can make.

The 30% improvement is possible but not realistic. It is generally only promoted by those distributing cheaper whiz bang units and not by the more upstanding manufacturers, but even so, a 10% improvement is still better then none. On top of this there is no need to worry about shunts and relays and the possible overheating that you previously had as the controller is rated at 60A, more then enough to handle the 48V 500W throughput. It becomes a much simpler plug and play set up in my view.

[Craig]

if the pl20 will handle 360w without modification
I will go that way thank you for the advice everyone

Hi Bob,

I have been running this set up for a few years. On the very rare occasion you do reach the max amps, the pl 20 simply discards the couple of extra amps. This is not an issue.

[bob r]

thank you for that information craig I could fit the relay later if needed

bob

[T1 Terry]

The real advantage of running the relay is the cables can go straight from the solar panels to the battery compartment, no need to try to thread big cables through wall cavities to the controller and then on to the battery. If the controller is going to be mounted some where in the most direct path between the solar panels and battery compartment by all means just use the controller for now and add the relay if you find you need it.
Don't scrimp out on cable size, this very handy calculator http://www.kilowatts.com.au/calculator-voltage-drop.php will help you determine the cable size needed and this site http://www.engineeringtoolbox.com/awg-w ... d_731.html will help you convert that to cable size.
This is the biggest mistake people make with solar, under estimating how much they will loose by using cable that is under sized, the added cost is minimal, the gains last the life of the system.

T1 Terry

[bob r]

thanks for that terry where would I get the right relay and a wiring diagram so I get it right
bob

[T1 Terry]

This is the schematics on the plasmatronics site, I recommend using the Jaycar relay, if you use the heat sink they recommend for it you will be limited to 40 amps per relay, to get the full 100 amps requires building a different heat sink and fan controls. The set up I use had the fan running constantly in yesterdays heat so to me the non fan cooled heat sink would have a restricted load capacity on days where the ambient was over 40degC, this would go for any solar regulator that relies on non fan assisted cooling if it was running close to it's designed capacity. If you use their resistor recommendations you need to mount it somewhere it will get good cooling, it gets mighty hot when the PWM starts although my test unit is still functioning after nearly 2 yrs, I doubt it would survive charging lead acid batteries though.
http://www.plasmatronics.com.au/downloa ... .V1.11.pdf
http://www.plasmatronics.com.au/downloa ... pacity.pdf

T1 Terry