Volt/amp meter

[duncan webster 1Participant @duncanwebster1]

I finally got round to fitting an ammeter in the cable between solar panel and controller. As I suspected no charging going on. I then measured the voltage from the solar panel. Connected to the controller with battery connected and signals switched on I get 12.5 volts, same as the battery volts. If I disconnect the controller I get >20v. Seems something is pulling down the panel volts, but I don’t know whether it is a duff controller or the solar panel having gone high resistance. My cunning plan now is to put a couple of car rear light bulbs in series across the panel with controller disconnected and see what happens. If the panel is OK I expect to get some amps.

Anyone think this is stupid? Testing the controller isn’t as easy, we have no mains, so no means of injecting volts unless I take the whole box of tricks home, which isn’t as easy as it sounds.

[duncan webster 1]

On duncan webster 1 Said:

Connected to the controller with battery connected and signals switched on I get 12.5 volts, same as the battery volts. If I disconnect the controller I get >20v. Seems something is pulling down the panel volt

Solar panels are essentially current sources. They will show almost their full open circuit voltage with very, very little light, but can only produce a trivial amount of current in those circumstances, so what you’re seeing could be completely normal. To generate current, it needs sun – the more the better.

I would suggest checking again when the panel is completely illuminated with full sun. You can connect an ammeter straight across the panel (not the battery!), short circuiting it and compare the current generated to the specification.

The dull and overcast weather we’ve been having isn’t good for solar.

 

[duncan webster 1Participant @duncanwebster1]

Thanks, come to think of it I can’t remember it being sunny at any time when I’ve been measuring. I’ll wait for a sunny day before taking any further action. At least it gives me an excuse for procrastination.

[noel shelleyParticipant @noelshelley55608]

As Andy has said put a load straight across the PV panel and read the current, Be it bulbs or simple short, a check on voltage at the same time may be useful. The weather has not been good for PVs – it is interesting it observe the increase in output as the PV panel is brought fully on to the sun in all planes. That you have 20v is fine, try a 24v lorry bulb, a side light first then a brake light, a stop/tail bulb gives both in one ! I fancy you have voltage but little current, poor light or a faulty PV panel.  Good luck Noel.

[duncan webster 1Participant @duncanwebster1]

Well for the first time in months we had a conjunction between my being at the track and an appearance of the sun. Where the panel is positioned it never did see the sun much before 1:00 pm, but I found that when it would have been seeing sunshine last year, the trees have grown so that it was still in shade. Ten minutes later with some pruning shears and it was charging merrily. In my ignorance I had assumed that being able to see the sky would be enough to get some charge, but it seems not. Unfortunately the trees in question are in protected woodland, so I’ll have to ring the council and get permission to do a more thorough job. To be fair to them, in the past they have been very helpful, probably because when a tree dies and has to be felled for safety reasons, we have always planted a replacement UK hardwood replacement. We even water the replacements for a year or two to give them a start, which is more than another local council can manage.

Thanks to resent respondents who pointed me in the right direction

[CirclipParticipant @circlip]

Failure rate must be phenomenal of garden lights supplied with solar cell charge systems. Even a new “Floating fountain” didn’t work unless the power of the Sahara sunlight  was applied.

Regards  Ian.

[Howard LewisParticipant @howardlewis46836]

If the trees have a Tree Protection Order, Do not tell the Council that you have pruned them, (Unless it was dead wood constituting a Health and Safety hazard)

Otherwise you could be fined or end up sewing mailbags!

Then expect to fill in a seven page form, in the hope of getting permission to prune “live” foliage.

Howard

[Robert Atkinson 2Participant @robertatkinson2]

The solar panel consists of several cells in series (possibly parallel as well depending on design). If even one cell on the panel is in shadow the output voltage will be reduced and thus the battery will not fully charge. a couple of cells in series could stop charging completly.

Robert

[Peter Cook 6Participant @petercook6]

It doesn’t matter how idiot proof you make things – nature will simply breed a better idiot.

[Howard Lewis]

On Howard Lewis Said:

If the trees have a Tree Protection Order, Do not tell the Council that you have pruned them, (Unless it was dead wood constituting a Health and Safety hazard)

Otherwise you could be fined or end up sewing mailbags!

Then expect to fill in a seven page form, in the hope of getting permission to prune “live” foliage.

Howard

We have an agreement with the tree man that we can do ‘low level pruning’ otherwise we would struggle to run trains. As I said they have always been reasonable, they have agreed to us felling 2 trees which were in danger of dropping big branches as long as we put something in to replace them.

[duncan webster 1Participant @duncanwebster1]

Cutting back the trees which were overshadowing the panel provided a temporary solution, but it’s back. Despite the really sunny weather over the weekend we ran out of electrons. Nicked the battery out of an electric loco to allow us to continue. I’ve brought the (lead acid) batteries home and put them on charge via my Aldi ‘intelligent’ charger. Checking 20 hours later now says it is fully charged (4 bars) but only 12.8v. I think it should be up at 14v or so if fully charged. It is very old, probably 10 years+. Time for a new battery? Can I test it. It’s a deep cycle 24 AH, so an automotive tester doesn’t feel right. Just putting second battery on charge now, that is 36AH, but I suspect not deep cycle as it quotes 320A

We’re going to move the panel to away from the trees, and while we’re on add a second one. Do I simply put the new one in parallel with the old one?

Similarly, when the diesel genny is running it would be sensible to have that contributing. Any ideas on connection. Current thoughts are a relay which detects genny running and connects genny charger to battery, disconnecting the solar panels. Am I over thinking it? Running the genny full time is not attractive, if it hasn’t got a good load it soots up its injectors.

[Robert Atkinson 2Participant @robertatkinson2]

12.8 volts does sound a bit low immediately off charge. You can test the battery with a load like an 55W headlamp / foglamp. A 55W bulb will draw approximately 4.6A so your 24AH battery should last about 5 hours. At voltage of about 11V would be the “flat” point, certainly no lower than 10V. If it doesn’t last 3h it’s time to go to the scrap.
You mention a second battery that is different. Isthat on it’s own charger etc? You should not connect different batteries in series or parallel.

Robert.

[duncan webster 1Participant @duncanwebster1]

12.8 was with it still on charge. The solar panel controller has some intelligence, although as I didn’t buy the bits or assemble it I don’t fully understand it. It is supposed to preferentially charge the primary battery and then when that is fully charged switch to the secondary. I’m not too clear what it does when discharging, it certainly cuts everything off when battery volts gets down to ~11.5v. Unfortunately the chap who made it up is now ill and is struggling to contribute.

 

 

[Stuart Smith 5Participant @stuartsmith5]

I fitted this monitor to my battery electric loco.
It is intended for solar setups.

https://lowenergysupermarket.com/product/battery-monitor/

I also made a dc current and voltage monitor using an Arduino and a Hall effect clip on Ct. Using this you can record the readings to a memory card or display on a pc. I can post details if anyone is interested.

Stuart

[Michael GilliganParticipant @michaelgilligan61133]

These, which occasionally appear in Lidl “silly-cheap” don’t do anything very clever … but they do it quite well:

.

.

.

MichaelG.

[Author]

Posts