I'll say hello...

[NeilP]

Hello all...

Sorry for this post....I came back to the top and added this line as I could see i was rambling. I am basically looking to see if there is a way I can rewire/improve how I am doing stuff with little or no cost..

I'll put a post up just to say a quick hello, but already, by doing the 'new to a forum' things, like reading FAQ's I have answered my own question, or at least confirmed what I thought.
Bit of a mixed post this, see if any one can pick their way through my ramblings.
I live in Jersey, the island, 49.17 Degrees North, 2.05 West.

I'll summarise here, just in case any one has any bright ideas.. Though I'll not be spending any money again for a while as I just upped my mortgage from £700 a month to £1900...my choice...pay it off quicker..so no new toys for a while
Unless of course someone can recommend I a worthwhile, but cheap (£120-150 max) MPPT controller upgrade that will give a great improvement over the PWM


I inherited a pair of unmatched panels and a Sun YOBA® 80A controller. It does its job ..cant say more than that. Suspect it to be a cheap and cheerful thing, probably no the most efficient...but as I say it was all free..inherited from a chap i helped in his last years of life. I do suspect it might be junk..but no idea ..wont take offense if you all laugh at it, and say it came from a Christmas Cracker

Battery bank is 2volt lead acid cells..big things, 6 x4 inch by 18 inch tall roughly, from an aircraft tug, about 4 tonne of them. I rigged them up about 4 years ago. and I cant give the exact series parallel config at the moment, but I think 4 parallel strings of 6 to give 12 volt out. I had a 12 volt 2kW 240volt inverter, so had to go with 12 volt.

They are not matched as you can see
they are wired in parallel
about 60 foot from the controller.
Cable is 4 core Flexible 3 phase armoured industrial/farm machinery type flex. Since 4 core, the cores are paired to give lower resistance.

Bright sunlight, the controller shows a max of 8 amps. I can turn the panels manually during the day to keep them aligned. This is al set up in a farm meadow /camping area to supply us with WiFi/Sonos connectivity to the house, lighting etc for the odd nice summer day we can use the area. If you are in the UK you will know it has not had much use this year!

years ago when I rigged it up, I just did them in parallel and just left it . it works..it is fine...but if the power is left on, and we get cloudy conditions, the battery bank does drop slowly over a week or two to about what can be seen in the controller picture.

Got to thinking about it the other day and thought I might get improvement / less voltage losses if wired in series. Controller is good for < 48 volt and it does run fine wired in series.

But it is a PWM controller...so a higher voltage in and half the current. yes I checked this the other day . from 7.9 amps down to 3.3 amps when in series..as expected higher voltage too..but only till the charge controller does its thing.

So what do you all reckon ...would a MPPT controller and wire in series make a good noticeable difference..like 30-40 % or more or is it going to just be a marginal increase?

No money or time or inclination to buy new panels yet, just makign the best of what we have with the thought to leave it on 24/7 drawing 2-3 amps for inverter, WIFI Bridge and AP and a CCTV camera.

If I could squeeze another 30-40 % charge capacity to keep the batteries topped up , i reckon all would be good to keep it powered permanently.

 

[BenQ]

From what I can tell, you don’t have enough panels to charge those batteries at a higher voltage. Even if you did, you said you only have a 12v inverter. Unless you are able to find a really good deal on a used 24v or 48v inverter and 1 or 2 more panels, there isn’t anything you can do.

 

[NeilP]

The two panels in series in full sunshine the other day gave around 36 volts into the PWM controller and it was displaying a max of 3.9 amps on the LHS of the LCD panel. But not sure where the amperage is being displayed from ..if it was the input to the controller, or if that is what the controller is pushing in to the battery.

It has been working well enough..just a thought after seeing stuff about MPPT charge controllers. I read that the MPPT type controller can work better/ more effieient with a good differential between panels and battery voltage. I think what you are saying is that the 36 volt panel to 13.8 voltage differential of the cells is not great enough ?

Re wiring the battery bank is not a real option..even if I did have a different inverter.....though...if I did go higher voltage..there is always the potential to use some small buck/boost style Switched mode PSU's to run the Wireless bridge, the Access point and the CCTV... Save losses of going up to 240VAC..then back down to the 48 volt and 24volt with the Power Over Ethernet convertors for the Wireless devices..

Hmm..I'll see if I can get the pictures of the battery bank.

 

[NeilP]

Here is the battery bank... free ..so that was good...plenty of scrap value when their time is up...They were a few years old, regularly charged/ maintained, but never used in the aircraft tug...and I got the job of 'disposing" of them when work sold the tug...
Now I see the picture and count them up I can see how I have them set up. It is two banks of 6s3p
Just looking at the spec again...I thought each cell was 80 Ah..but I see that 80 ah is the per plate capacity. so each 2 volt cell must have 8 plates so 640Ah from the centre of the chart

I do nto ahve a picture of where they are setup. but getting to them again to re configure them would be a pain.....though getting to the ends of each block to reconfigure to two banks of 36 volt might be possible...they are stacked in a rack..so getting to the lower ones means manually moving the top ones down off the rack after disconnecting each cell...not a job I fancy again ..

 

[BenQ]

Okay, so a few things, increasing efficiency by 30-40% as you originally stated by changing to an mppt charge controller is probably not going to happen, unless your current pwm controller is really crappy and only 60% efficient. How efficient is your current controller? This one on Amazon is 99.5% efficient so if yours is really horrible (which it probably isn’t) then sure you’ll get a lot more efficient! Will Prowse already tested pwm vs. mppt and there wasn’t much difference under good conditions.

Real gains in battery efficiency come from inverters that do not consume too much power AND convert dc to ac efficiently.

 

[BenQ]

Or adding more solar panels. Honestly from what you said in your original post, you’re close to being able to leave this thing running 24/7 so find a couple more used 12v solar panels and add them in parallel and that should do it!

 

[NeilP]

The adding the panels bit...living here in jersey ..getting the buggers shipped to the little island end up costings as much as buying the things

The current two are mounted on a 4 inch stainless pole at about 6 foot..woudl not be a big job to make a frame if I found any.

Yes, it is close to being able to be left running 24/7 any way , so that was why I was thinking that a different controller might be enough. and the easy ..swap in 20 minutes job..rather than a days metal workmen to build a new bigger rotating frame for the new panels.


Just bypassing the inverter completely might be just as useful in efficiency gains...12 VDC- to 48vdc step-up ebay module would be better, more efficient than 12v to 240 back down to 48 via a big inverter.

Ah thanks for the YouTube link..I'll watch it next.

 

[NeilP]

Looking at the video...I think that an MPPT might be a good option, combined with direct power of the devices without the inverter..

 

[BenQ]

Yes, if you don’t need a big inverter, change that! That will be a huge energy saver! If you still aren’t able to run 24/7 and want to try an mppt controller, go for it, but watch the video and good luck!

 

[NeilP]

My inverter was not as big as I thought. I had used the big one, but had already fitted a 600W one, instead of the big one.

I got an MPPT controller last week and fitted it today. Cloudy 11 am sun shine and with the two panels now in series, I was getting 10-11 amps in to the battery bank.

Compared to 7.8 amps in bright midday sunshine with the PWM charger and the panels in parallel, definitely a good upgrade.
Was the smallest MPPT controller they did, at 20 amps, but enough for my needs.

My network access point is in the same shed and runs 12volt, and I can get a
12-48V boost convertor PoE injector for the bridge client of the connection.





It was this one

SolaMr MPPT 20A Solar Charge Controller​

 

[NeilP]

Well that controller lasted all of three weeks.

My fault really as i jsut did nto think..

I had my 600W (1200W peak) inverter connected to the output of the old PWM 100 amp output capable controller and it had worked that way for years.

never drawn more than about 30-40 W max from the inverter so never had a problem.

I went away for a vacation and some mates came to stay and plugged their SWMPSu e-bike battery charger in to the inverter..something I'd not have done...but last year they did the same...and all was fine with the old big PWM charge controller.

This little MPPT controller could not take it ...I forgot TBH that the inverter was nto via relay or similar..it was all wired in tucked away down the back..


So this 20 amps MPPT controller only had a 10 amp output


Yesterday a new EPEVER Tracer AN Series 2210An controller arrived...and a 100 Amp relay ..
I want the inverter 'controlled' from the Charge controller so when i go away and friends come to stay at my backwoods camp site..they will not totally kill the batteries leaving the inverter on..If voltage drops below 11.whatever volts ..charge controller will cut the relay and kill the inverter.


They di nto send a data cable for the Tracer though...so cannot user the User Mode for the battery type. Have set it to flooded cell for now.

Need to make a interface cable...will start a new post on that ...

 

[A.Justice]

Okay, so a few things, increasing efficiency by 30-40% as you originally stated by changing to an mppt charge controller is probably not going to happen, unless your current pwm controller is really crappy and only 60% efficient. How efficient is your current controller? This one on Amazon is 99.5% efficient so if yours is really horrible (which it probably isn’t) then sure you’ll get a lot more efficient! Will Prowse already tested pwm vs. mppt and there wasn’t much difference under good conditions.

Real gains in battery efficiency come from inverters that do not consume too much power AND convert dc to ac efficiently.

That's an issue where Will and I disagree. That test that he did (PWM vs MPPT) was good, but was using panels that were properly sized for the battery, so the panels don't make much excess voltage. That means the MPPT isn't going to be much more efficient UNLESS you have higher voltage, uneven, or shaded panels. So while the test he did was accurate, I feel that there is more to the story.

I got some 55v, 3.5a panels to use on a 12v system. My pwm controller would push 3a MAX, I switched to MPPT and can get over 10a per panel. MPPT's shine at high voltages, PWM works well for lower.

In OP's case he probably won't squeeze that much extra power with an MPPT (MAYBE 10%), at least not enough to justify the cost.

 

[NeilP]

The increse in charge current i got from going with the two panels in parallel, and a PWM controller, and switching to Series panels and a MPPT controller is this

MAX charge current i ever saw with PWM and parallel panels was
7.9 amps

Going to Series and 36-38 volt out the panels, -and the first MPPT controller… 11 amp charge current

Reading the spec sheet of the Tracer AN 2210, i see they claim higher efficiency at LOWER input voltage.

So . a toss up between feed line losses along 60-80 foot of cable, at the lower voltage, Parallel panels, which the controller will find more efficient, or less losses along the feed, and lower controller efficiency…admittedly only by a % or two

 

[NeilP]

So ...what increase % did I get...
was 7.9 max..now I am getting at 11..possibly more , not checked on a similar sunny day ..but a good 11.amps

11/7.9 = 1.39 = so 39 % increase

or would you say 3.1 amp increase over the original 7.9

3.1/7.9 = 0.39 ...ph ..so the same..yes so 39 % increase in this case.


Panels were 18 volt panels. and as A. Justice said, a higher voltage...36 volt max to a 12 volt battery system.

Now to get the data cable form them . so i can turn down the max charge voltage. I think it should be lower than they set for flooded lead acid. Their maximum over charge voltage is around 16 volts.

Will start a new thread for that