Solar PWM

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gstuart

gstuart

D3 Grandad
Full Member
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kermit_rr said:
Maybe worth starting a new thread on solar? lol

I understood dual controllers were for 2 different solar inputs, where you have different orientation to the sun or different rated panels etc
Mppt is better tech than pwm but they only really come into their own when you have 2 or more panels in series to ramp up the voltage.
I've got 2, 50w panels and a mppt controller. Waiting for some decent sun to compare battery input from parallel vs serial solar connection, it seems difficult to find cold hard facts online
Click to expand...

hi buddy @kermit_rr

so carrying on with this and very grateful to ur goodself

Ref The dual controllers, so I assume that’s why said about the overkill , maybe I’ve not quoted them correctly but the ones I’ve looked at are just for dual batteries as per pic

so indeed was wondering if it’s worth keeping the aux battery or do away with it and fit the tyre compressor in its place for convenience

Plus looking at securing the panel I’ve got the roof rails but not the cross bars so thought of buying some L shaped stainless steel bars , fixing it between the rails and then running the wire through a blank thats in my roof, was going to use battery cables 16mm but alas haven’t really looked into cable size and if 16mm is overkill, would run around 15 x feet from front to back

Another thing I see it mentions the controller is suppose to be as near as possible to the battery, but if u have 2 x is it just the case of putting it in the middle of them

Also can see what the max distance is away from a battery they can be fitted

have been spending months reading up so then when I buy the bits it will do as intended , well in theory anyway

do u run a lot off ur solar then plse, is it mainly for when u go away camping etc , can never remember series or parallel , always have to look it up and what the advantages are

will be interesting of what ur finds are , think I saw a video ref that where a guy tests them in series and then parallel , will see if I can find it

thks so much as always

https://zhcsolar.com/dual-battery-solar-charge-controller/

2D5181E0-9470-409E-B19C-28347C9D9A9D.jpeg
 
Interesting video! However he uses 40v panels, in the UK, 18 or 20v seems more common - mine are 18v
Also, in my opinion, his serial/parallel argument isn't entirely correct. Not wrong, just missing a few details when it comes to mixing panels. You won't have that problem :)
I have 2 identical 50w panels that use monocrystaline split cell tech. which is why i want to test both wiring methods to see which, if either, works best
Mppt will give a better result over pwm on 40v panels, I'm not yet sure how much better mppt will be over pwm on a single 20v panel, it's probably minimal.
Had a quick look at the dual controllers and it seems they connect primarily to the leisure battery but can trickle charge a second starter battery. On the one i looked at, it was max 1A to the starter, which may or may not meet your needs. I said overkill because i assumed it was dual solar inputs to a single battery. Also, you'll probably be ok with a pwm if you have a single 18v panel
Let me do some tests and see what my findings are. Will be wednesday at the earliest, dependant on sun
 
kermit_rr said:
Interesting video! However he uses 40v panels, in the UK, 18 or 20v seems more common - mine are 18v
Also, in my opinion, his serial/parallel argument isn't entirely correct. Not wrong, just missing a few details when it comes to mixing panels. You won't have that problem :)
I have 2 identical 50w panels that use monocrystaline split cell tech. which is why i want to test both wiring methods to see which, if either, works best
Mppt will give a better result over pwm on 40v panels, I'm not yet sure how much better mppt will be over pwm on a single 20v panel, it's probably minimal.
Had a quick look at the dual controllers and it seems they connect primarily to the leisure battery but can trickle charge a second starter battery. On the one i looked at, it was max 1A to the starter, which may or may not meet your needs. I said overkill because i assumed it was dual solar inputs to a single battery. Also, you'll probably be ok with a pwm if you have a single 18v panel
Let me do some tests and see what my findings are. Will be wednesday at the earliest, dependant on sun
Click to expand...

many thks for the great info and u found the video interesting , through ur knowledge I wouldn’t have known that all his findings weren’t 100%

the controller I looked at seems u can have the main crank battery as a primary and indeed leisure battery as the second connection

didn’t realise that ref the starter amps, assume it was in the manual of the controllers, will need to see what amperage my starter is or what other figures I need to look at

know my alternator is rated at 150 amps

this again and look forward with great interest to ur results
 
Also found this which I found interesting , ref location of controller and size of cables, wondering if I use 4mm or if it would be an overkill ,

https://www.leadingedgepower.com/sh...ar-panels/solar-panel-installation-guide.html

quote

Ideally, the charge controller should be within 5m of the panels and within a metre or two of the batteries. The basic rule of thumb is that the shorter the cable the better, as it will reduce any voltage losses and result in a more efficient system. Cables that are supplied with the panels are designed to reduce voltage loss to less than 2.5% over 5m. For longer lengths, or if you are combining more than panel into a single cable set, you should use our cable charts or ask us for advice. Cleversolar 2.5mm solar cable is generally ok for 5m lengths up to 135W (270W at 24V) and our 4mm cable for up to 200W (400W).
 
Found the tech spec for the Bluetooth one, https://pbautoelectrics.co.uk/shop/...ontroller-15a-for-12v-or-24v-systems-stcc15m/


Technical Specification
  • Nominal System Voltage: 12/24VDC (automatic system voltage recognition)
  • Battery Voltage Range: 11-36V
  • Rated Battery Current: 15A
  • Self-consumption: ≤24mA
  • Over Voltage Disconnect Voltage: 16V/32V
  • Charging Limit Voltage: 15.5V/31V
  • Equalize Charging Voltage: 14.8V/29.6V
  • Float Charging Voltage: 13.8/27.2V
  • Operating temperature: -35oC to +55oC
  • Overall dimensions: 150 x 85 x 40mm
  • Mounting hole size (in case): 3.8mm
  • Terminals: 6mm2
  • Net weight: 220g
 
What size battery are you using Gary? What panels are you using?

I use 180 Watts of panesl to change a 1300 Wh Pb battery, using 3 of my PWM5 charge controllers. A high efficiency PWM charge controller is all that's needed for small capacity systems of a few hundred Watts of panels and a 100 Ah battery.

MPPT uses more power than it recovers in small systems, so is a pointless system to employ.
 
This is off that link. And is absolute BS.
"The PV Logic MPPT Pro charge controller has been designed to deliver the highest possible power from any 12v or 24v solar panel into a 12v battery. MPPT (multi power point tracking) technology increases solar yield by up to 20% over a standard PWM charge controller by artificially modifying the voltage coming from the solar panel by actively matching it to suit what a battery or batteries require, whatever state of discharge they may be in. This advanced algorithm ensures that whatever the weather conditions, a solar panel or panels will deliver the maximum power to a battery/s and with the minimum of electrical losses."

They can't even get the terminology correct. MPPT means Maximum Power Point Tracking. Not Multi power point tracking. :mad:

An MPPT charge controler won't recover an extra 20% from the panel, fact. The real figure is closer to 3%, 5% tops. But then when the sun goes down, this MPPT is consuming 25 times more energy from the battery, than one of my PWM5 charge controllers, so it's simply wasting any extra energy it "might" have recovered. It's an expensive waste of money imho.;)
 
Last edited:
There's so much wrong or inaccurate information out there it's just daft, some of it comes from so called professionals who should know better.
I'm tempted to write a page about what I've learned to be true, but nobody would likely ever find it.
Many folks say don't bother with mppt unless you have at least several hundred Watts of panel, to just get more panels, but if you have space limitations then that's simply not an issue.
Mppt isn't a magic bullet, but the battery charging tech is often better than you get in the cheapest pwm controller.
Like I've said previously, mppt comes into its own when you have more than one panel or the output voltage is significantly higher than the ~14.5v required to charge a battery.
 
Nodge68 said:
What size battery are you using Gary? What panels are you using?

I use 180 Watts of panesl to change a 1300 Wh Pb battery, using 3 of my PWM5 charge controllers. A high efficiency PWM charge controller is all that's needed for small capacity systems of a few hundred Watts of panels and a 100 Ah battery.

MPPT uses more power than it recovers in small systems, so is a pointless system to employ.
Click to expand...

hi mate

recently replaced the exide with a yuasa 019 , which indeed has 95/ah and 900 Cca

haven’t got any panels yet and been reading about solar for while in what to get
 
Nodge68 said:
This is off that link. And is absolute BS.
"The PV Logic MPPT Pro charge controller has been designed to deliver the highest possible power from any 12v or 24v solar panel into a 12v battery. MPPT (multi power point tracking) technology increases solar yield by up to 20% over a standard PWM charge controller by artificially modifying the voltage coming from the solar panel by actively matching it to suit what a battery or batteries require, whatever state of discharge they may be in. This advanced algorithm ensures that whatever the weather conditions, a solar panel or panels will deliver the maximum power to a battery/s and with the minimum of electrical losses."

They can't even get the terminology correct. MPPT means Maximum Power Point Tracking. Not Multi power point tracking. :mad:

An MPPT charge controler won't recover an extra 20% from the panel, fact. The real figure is closer to 3%, 5% tops. But then when the sun goes down, this MPPT is consuming 25 times more energy from the battery, than one of my PWM5 charge controllers, so it's simply wasting any extra energy it "might" have recovered. It's an expensive waste of money imho.;)
Click to expand...

kermit_rr said:
There's so much wrong or inaccurate information out there it's just daft, some of it comes from so called professionals who should know better.
I'm tempted to write a page about what I've learned to be true, but nobody would likely ever find it.
Many folks say don't bother with mppt unless you have at least several hundred Watts of panel, to just get more panels, but if you have space limitations then that's simply not an issue.
Mppt isn't a magic bullet, but the battery charging tech is often better than you get in the cheapest pwm controller.
Like I've said previously, mppt comes into its own when you have more than one panel or the output voltage is significantly higher than the ~14.5v required to charge a battery.
Click to expand...

many thks guys and so grateful

alas I’ve just gone from that same advice off the sites ref the MPPT controllers as I haven’t got any previous knowledge so indeed spent the time reading them

would rather listen to both of u as I know it’s 100% accurate

thk god I asked and just didn’t go ahead and buy the MPPT controller

so will do some searching again for a PWM controller as mentioned no point using something is it’s going to take a lot back out the battery

another thing is the panels, are mono better please ,

Will be nice to at last resolve the constant power hungry disco flattening batteries in under a month if not used

will take the aux fuse box and switch that over to the main battery later

can’t thk u enough for this and very grateful for u taking the time
 
Just thinking , is the 100 watt ok for a size to use and what mm cable size would I need from the solar panel to the controller plse,

many thks
 
gstuart said:
Just thinking , is the 100 watt ok for a size to use and what mm cable size would I need from the solar panel to the controller plse,

many thks
Click to expand...

I use a 100 Watt panel, hooked up the one of my £12.50 PWM5 charge controllers, using 4mm sq cable. 4mm sq is all that's needed for a 100 Watt panel. You can actually use 2.5mm cable for a 100 Watt panel, as the current isn't much more than 6 Amps in full sun, on a correctly angled panel. Your panel will be flat, so will loose about 50% of the output.
 
Nodge68 said:
I use a 100 Watt panel, hooked up the one of my £12.50 PWM5 charge controllers, using 4mm sq cable. 4mm sq is all that's needed for a 100 Watt panel. You can actually use 2.5mm cable for a 100 Watt panel, as the current isn't much more than 6 Amps in full sun, on a correctly angled panel. Your panel will be flat, so will loose about 50% of the output.
Click to expand...

many thks as always , see didn’t think of that with the panel flat loosing output , shame I can’t angle it but then won’t get under many height barriers unless I can somehow work out a bracket system so when at home / holiday can raise it a few degrees and then lay it flat when out driving , maybe some boot struts ??? , along with a locking catch

so far ref the panel , come up with fitting the factory short rails, then using some L shaped stainless steel lengths to go across the rails

did look into some of the ones u can lay on ur dashboard but weren't very big as in output

thks as always
 
I just looked up the details of my 10A pwm and 10A mppt controllers. Both made by the same company. The self consumption of the pwm is 8.4mA and the mppt ~12mA
 
You can get round the lower output of flat panels, simply by doubling them up, so fit 2 instead of 1. ;)

Dash mounted panels are pointless, as the UV needed to generate the power is filtered out by the UV blocking coatings on windscreen glass. ;)
 
kermit_rr said:
I just looked up the details of my 10A pwm and 10A mppt controllers. Both made by the same company. The self consumption of the pwm is 8.4mA and the mppt ~12mA
Click to expand...

that’s interesting and indeed as u both said earlier proves the point of the MPPT using more Ma
 
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