Connecting cables to 12v PV solar controller?

[toontra]

Very basic, I'm afraid, but beyond me.
I want to attach a 12v light spur to the output of a PV control unit like this one:

There are connectors at the bottom right for this specific purpose.  The system is already up and running. 

My  question is - can I just stick the wires in while everything is "live" or should I disconnect the meaty PV panel and/or battery cables first?

[Diver300]

Just join them up live. It's 12 V so no risk of electrical shock. It says "full protect" so even if you short it out, it shouldn't do any harm.

Try not to short it out anyhow, so have all the wiring to the light and its switch finished before you make the final connection which should be to the control unit.

[toontra]

Just join them up live. It's 12 V so no risk of electrical shock. It says "full protect" so even if you short it out, it shouldn't do any harm.

Try not to short it out anyhow, so have all the wiring to the light and its switch finished before you make the final connection which should be to the control unit.

Thanks!  Yep, that was the plan - connect up the light, switch & cable & then shove the wires in the terminal last of all.

[aidan.f]

'Very Basic' is  an accurate summary of that controller - and  for less  than  £5 I don't  expect much circuit or overcharge protection.
With 12 Volts @ 30 amps  as  the  'rating'  you  could  potentially be  feeding 360 Watts of  solar power into 100's  of Ah of  batteries The  potential fire risk is huge.
I presume the system was  installed by a  competent  person?
What external fusing  is incorporated  in the  installation? All cables (and  the  device) should be rated for the prospective fault current.
Personally if it is  much  more than a 10 Watt  panel charging a 7aH SLA with  5 Amp fusing  in the battery circuit  for  a toolshed (containing  nothing valuable )I would  rip it out  and start  again

It's  not  even  an efficient solar charger...

[grams]

for less  than  £5 I don't  expect much circuit or overcharge protection.

That easily buys you a microcontroller and a couple of big MOSFETs, which is more than enough to all the necessary jobs. I have a similar one and it's biggest problem is it trips *too* easily - it's sensitive to brief current spikes and relay flyback pulses.

I think it's fine, though as you say you probably want an appropriately rated fuse on the battery as a backup.

[toontra]

Thanks all.  It's 50w panel and one of these batteries:

https://www.amazon.co.uk/gp/product/B00WPWFN6M/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

No extra fusing was done on the battery AFAIK.  All the cabling was done as recommended using appropriate cables and connectors.

The whole setup is just to allow devices to be charged in the holiday hut and seems to work fine for that purpose, but the addition of a light would be useful, thus the question.

[aidan.f]

NO FUSING ANYWHERE WITH  THAT BATTERY!

Have you any idea what the fault  current  would be?

toontra, please, please  get  a  competent  person on board

Just  because it  says 'protection does not  mean anything at  all

You should have  a  battery  isolator and  battery  fuse  with all cables rated for  the  fuse fault  current, or  individual circuit  protection

Why  cut  corners  when  a  few  10's  of  £'s buys peace of  mind. especially  somewhere you  are sleeping

I have  read the  document below, as a design  engineer this  device correctly  installed  will be  several orders  of  magnitude  safer

https://www.sunstore.co.uk/wp-content/uploads/2018/11/EPEVER-Manual-VS-AU.pdf

3-Stage intelligent PWM charging：Bulk, Boost/Equalize, Float
Support 3 charging options: Sealed, Gel, and Flooded
LCD display design, dynamically displaying device’s operating data and working condition
Multiple load control modes
Energy statistics function
Battery temperature compensation function
Extensive Electronic protection
Electronic Protections：

PV short circuit protection
PV reverse polarity protection
Battery over voltage protection
Battery over discharge protection
Battery reverse polarity protection
Load overload protection
Load short circuit protection
Battery overheating protection
Controller overheating protection

Let's  talk about  a scenario  just  to make my point..
Install of 24-12 Volt DC converter in a big  red  fire truck.  Installer  did  not  read  instructions, 'fit fuse of X amps rating'.' Unit failed fire appliance got filled with nasty smoke.
Two problems- Incompetent installer, and equipment  not  manufactured fail-safe with internal protection.
'If  it  can happen it  will happen...'

I have a similar one and it's biggest problem is it trips *too* easily - it's sensitive to brief current spikes and relay flyback pulses

So, as expected it's  a crap design.

[toontra]

Thanks Aidan.  Will swap controllers ASAP! Is that sufficient or do I somehow need to fuse the battery also?

BTW there is no inverter on our setup.

[aidan.f]

toontra,
Just  edited my  post above
Battery > Isolator> Fuse > Cable
https://cpc.farnell.com/unbranded/438/battery-isolator-switch/dp/CP03036?ost=battery++isolator
https://cpc.farnell.com/multicomp/mccq-211cn/fuseholder-in-line-ato-30a/dp/FF02078?st=30%20amp%20fuseholder
With a  30 Amp fuse the cable between battery and  fuse/controller  should  be  at  least  2.5 mm CSA
If  you  fit smaller fuses for each  sub - circuit then thinner  cable  will do.. - Probably  best to  have  a separate switch to isolate outputs when away in case  something  flattens  the battery
e.g .https://cpc.farnell.com/multicomp/ppfh-76ato4/fuseholder-ato-4pos-led/dp/FF02308
(not  ideal as  LED  indicators will drain battery over  time hence home/away  switch)
Regarding  the  controller  - just the  first  I  Googled -  so you  may  be  able to get a more suitable  one
CPC MT1050EU probably  a  bit  too  sophisticated =spendy  it  uses MPPT charging  which wrings the  last  few watts out  of the solar panel
CPC are also a  good  source of  enclosure boxes and  cable  tidying  bits  and  bobs

[toontra]

Excellent stuff.  Thanks again aidan.

A small job has turned into a bigger job.  Funny how that happens 

[aidan.f]

Whereabouts are  you?

[toontra]

I'm in London but the hut is in Scotland!  I'm going up at the end of the month.

[aidan.f]

Ah-Ha ..
Well I have a garage full of cables and connectors in Durham. 8 miles from A1 I could make something up ready for you.  Shall we PM from now on?

[toontra]

Indeed!

[Kim]

NO FUSING ANYWHERE WITH  THAT BATTERY!

Have you any idea what the fault  current  would be?

Quite.  Lead-acid batteries are rather good at melting things, (sometimes themselves).  There's a reason people like to use them for starting cars.

Just because 12V won't give you an electric shock doesn't mean it won't find other ways to hurt you.  (I've probably mentioned the time I measured the voltage on a car battery using a 2-for-a-fiver Craplin multimeter, having made the rookie mistake of leaving the probe in the 10A socket.)

I mean, I might give the Chinesium charge controller a go, on the understanding that at some point it is likely to either  a) fail with something in the 'on' state and overcharge/overdischarge the battery  or  b) attempt to release its own magic smoke.  With appropriate fusing and a battery you're not too precious about, sure, it's probably fine for a shed or something.

[chrisbainbridge]

There is a to. Of advice on the diy campervan sites and Facebook pages about how to wire these things with ready made professional wiring looms.

[aidan.f]

The system is as toontra Op'd is pretty simple and low demand. Max battery load below 5 Amps  A charge controller converter upgrade with battery fusing and isolator is on the cards. One thing to consider is expected battery automony. Three 600mm LED striplights (8W each) used for 4 hours a day would be about  10 amp hours. So 7.5 days use from a fully charged 75Ah battery. Solar charging wintertime over this period could  be minimal.

[toontra]

We only need minimal lighting so I was proposing to connect an LED strip light with inline switch.  Even this will only be used for a couple of hours a day in autumn/spring and not at all over the winter (hut abandoned!):

https://www.ebay.co.uk/itm/12V-5054-SMD-LED-Light-Bar-Hard-Tube-Strip-Under-Cabinet-Cool-White-Warm-White/114401236731?ssPageName=STRK%3AMEBIDX%3AIT&var=414621667196&_trksid=p2057872.m2749.l2649

We're still actually using gas mantle lighting for most areas fed with micro piping installed by my grandfather over 80 years ago, so no safety issues there     Replacement mantles are getting hard to find these days 

[grams]

Replacement mantles are getting hard to find these days 

Easy to find if you have a geiger counter.

[Jurek]

Replacement mantles are getting hard to find these days 

Easy to find if you have a geiger counter.

Had to look that up......