Solar Panel MPPT Charger

[steveallan]

Link to the Mag. that did the articles for the Ultrasonic kit.

http://siliconchip.com.au/

 

[wizard]

Its like before -you cant get the detail without buying the relevant edition of the mag or wait for the kit price from Jaycar (not listed on their website yet either on the UK or the Au one)

 

[nigelmercier]

Its like before -you cant get the detail without buying the relevant edition of the mag or wait for the kit price from Jaycar (not listed on their website yet either on the UK or the Au one)

I subsribe to this magazine, give me a few days ...

 

[alan]

Solar MPPT Charger Kits

I think they are available but only for lead acid batteries.
http://www.jaycar.com.au
CAT. NO. KC5500

Alan.

 

[nigelmercier]

I subsribe to this magazine, give me a few days ...

This PDF of the article may be of interest, the password is

- please do not cross-post this to other forums.

 

[simonfraser]

looks interesting, not knowing much about electric project boxes, would it not be better to use a plastic box to build the unit in ?

 

[charles_reed]

I think they are available but only for lead acid batteries.
http://www.jaycar.com.au
CAT. NO. KC5500

Alan.

I've a 500BZ MPPT unit - output cut-out volts can be adjusted for the type of batteries being fed.
What needs to be appreciated is that the output volts are, to a great extent, governed by the state of charge of the batteries and it's only the point at which the cut-out operates and charging ceases, which is adjustable.

Re plastic vs steel - most of these products are short-run lines - a plastic box requires an expensive tool. Mine too, has a steel box, with two sets of LCD read-outs for volts/amps in/out.

It is a considerable advance over a simple controller, increasing output by 20-25%.

 

[sarabande]

Does anyone feel inclined to make up one, or possibly two, of these please ?

Any ideas of rough costs (parts, construction, and good beer money)

 

[noelex]

Interesting controller. Its cheap enough that you can use one for each panel which improves MPPT efficiency on a boat.
The only drawback is the charge parameters are not adjustable and are a bit low for most batteries.

looks interesting, not knowing much about electric project boxes, would it not be better to use a plastic box to build the unit in ?

Aluminium cases are often used for electronic projects because they act as a heatsink. You can often substitute a plastic box, but you need an internal heatsink.

It is a considerable advance over a simple controller, increasing output by 20-25%.

I think you find you will be find on a boat the maximum gain will be 5- 10% from MPPT on average.

 

[noelex]

I've a 500BZ MPPT unit - output cut-out volts can be adjusted for the type of batteries being fed.
What needs to be appreciated is that the output volts are, to a great extent, governed by the state of charge of the batteries and it's only the point at which the cut-out operates and charging ceases, which is adjustable.
.

Good regulators have 3 or 4 adjustable voltage points. Equalize, boost, absorption and float. The time at least on absorption should also be adjustable. Like a 3 stage battery charger this decreases charge time and improves battery health
Unfortunately cheap regulators and many reasonably expensive MPPT regulators do not do this.

 

[nigelmercier]

The only drawback is the charge parameters are not adjustable and are a bit low for most batteries.

In what way are they not adjustable?

 

[noelex]

In what way are they not adjustable?

They are not adjustable because there no adjustment.

Bulk is fixed at 14.4 v absor[tion at 14.4v (probably one of these is a misprint) float at 13.5 and equalize at 15.84v. Absorption time is fixed at 1hr.
There is temperature compensation, but the above parameters other than the temperature compensation cannot be varied in any way I can see. These figures will not be ideal for most batteries.
Still, not bad given the cost. Many cheap regulators have a single voltage point which is much worse.

 

[Playtime]

Bulk is fixed at 14.4 v absor[tion at 14.4v (probably one of these is a misprint) float at 13.5 and equalize at 15.84v. Absorption time is fixed at 1hr.

General question about MPPT controllers - does the above cycle restart each day (i.e. after a period of darkness) or does the controller 'remember' where it was in the cycle.

 

[noelex]

General question about MPPT controllers - does the above cycle restart each day (i.e. after a period of darkness) or does the controller 'remember' where it was in the cycle.

Regulators with several stages (boost abs and float) will reset back to boost when the voltage drops below a certain level. The better regulators have a short time delay on this.
From the specs it looks like the Jaycar resets onto boost once the voltage drops below 12.45V which is typical.
This means that if the boat is not used and the batteries not drained the voltage will stay on float, but if the battery is used overnight it will start the next day on boost.
Some regulators also have a facility to go to boost say every 30 days to keep the electrolyte stirred up.

This sort of fine control of voltage is important for battery health and to ensure none of the solar power is wasted.

 

[gregcope]

Noelex,

Any suggestions for a decent two battery regulator for lead acid batteries?

 

[noelex]

Noelex,

Any suggestions for a decent two battery regulator for lead acid batteries?

I am happy to recommend alternatives, but a bit more information such as the size and type of solar panels, battery capacity and type, use etc are really needed.
Most regulators have a single output, and use this just to charge the housebank, or use a VSR to provide power distribution.
On my own boat the regulator supplies 2 house banks and can be combined with the start batteries, via a simple battery switch, to give the start electrolyte a stir occasionally.

 

[nigelmercier]

In what way are they not adjustable?

They are not adjustable because there no adjustment.

Errr ... yes there is! The adjustment is in the software...

; load SLA preset values
; battery voltage reduced to 0.3125 so 14.4V becomes 4.50V and D920 (H398) with A/D conversion (10-bit)
	movlw	H'03'
	movwf	CUT_M		; cutout SLA voltage high byte 14.4V 
	movlw	H'98'
	movwf	CUT_L		; cutout SLA voltage low byte
	movlw	H'03'
	movwf	FLOAT_H		; float SLA voltage high byte 13.5V 
	movlw	H'5F'
	movwf	FLOAT_L		; float SLA voltage low byte
	movlw	H'03'
	movwf	EQ_HI		; Equalsiation voltage high byte (14.4V x 10%)= 15.84V
	movlw	H'F4'
	movwf	EQ_LO		; Equalisation voltage low byte

 

[nigelmercier]

General question about MPPT controllers - does the above cycle restart each day (i.e. after a period of darkness) or does the controller 'remember' where it was in the cycle.

I can't vouch for all of them, but the one in the article is powered by the battery, so it does not restart each day, and therefore does not need to "remember". The trigger to reset the cycle depends on the voltage only.

Good question though.

 

[noelex]

Errr ... yes there is! The adjustment is in the software...

; load SLA preset values
; battery voltage reduced to 0.3125 so 14.4V becomes 4.50V and D920 (H398) with A/D conversion (10-bit)
	movlw	H'03'
	movwf	CUT_M		; cutout SLA voltage high byte 14.4V 
	movlw	H'98'
	movwf	CUT_L		; cutout SLA voltage low byte
	movlw	H'03'
	movwf	FLOAT_H		; float SLA voltage high byte 13.5V 
	movlw	H'5F'
	movwf	FLOAT_L		; float SLA voltage low byte
	movlw	H'03'
	movwf	EQ_HI		; Equalsiation voltage high byte (14.4V x 10%)= 15.84V
	movlw	H'F4'
	movwf	EQ_LO		; Equalisation voltage low byte

I think adjusting the software controlling the microcontroller is beyond the capabilities of most yachtsmen. But if you could explain how you would go about making the adjustments that would be great. It makes the regulator far more useful.
For example if I wanted to reset the boost voltage to 14.7V how is that done? What interface is used ?

 

[charles_reed]

Interesting controller. Its cheap enough that you can use one for each panel which improves MPPT efficiency on a boat.
The only drawback is the charge parameters are not adjustable and are a bit low for most batteries.


Aluminium cases are often used for electronic projects because they act as a heatsink. You can often substitute a plastic box, but you need an internal heatsink.


I think you find you will be find on a boat the maximum gain will be 5- 10% from MPPT on average.

In practice, in Greece it has been considerably higher than the figure you quote, the makers claim up to 40%. It is, of course, far more effective where you have lots of sun.