Solar charging fault issue

[Deleted member 6336]

Hi all,
I’m hoping some of you solar gurus can help with a problem I’m having with my converted T6 campervan.
My set up which has worked perfectly for the past 2.5 years is:

• Photonic Universe 120W semi-rigid panel
• Photonic Universe MPPT charge controller
• CTEK D250SA DC-DC charge controller
• 90AH lead acid battery (2.5 years old)

In case you’re wondering why there are two charge controllers, the conversion was done for me by a company and at the time they specified CTEK controllers in their conversions which presumably came in a kit but I wanted to monitor power output from the panel so they slotted in the second controller with an LCD panel with basic system info.

Battery:
On our last trip away, back in April before it warmed up we got a low (leisure) battery warning so apparently we managed to deplete it overnight. The load was 1x 12v fridge, 2 x iPads charging and 2 x iPhones charging. *As per my earlier comment, this is generally the load we put on the battery overnight and had no low power issues.
I carried out a basic discharge test on the battery, disconnecting the fully charged battery from the panel and it took around a day and a half for the battery to discharge from 13V to 11. 7V and trigger the warning.
It’s a little dometic 12V fridge, but unfortunately I don’t know the advertised power usage, but I would have expected around 2-3 days.
Q1: Do you think the battery is on its way out and needs to be replaced?
PS, I’ve already been down the rabbit hole of lead acid vs AGM vs Gell, vs lithium!! Ultimately the quality of battery I get will depend on the outcome of Q2

Solar charging:
I‘m lucky to have a friend with a lot more knowledge on solar and van builds than me but he is cray busy, so all he can manage is to drop in now and then on his was home from work.
Has has tested the output from the solar in optimal conditions (unusual for Scotland) and we are generally only getting around 11V from the panel. We have seen as much as 16V but on re-testing get around 11V again, so this is weird.
From my layman knowledge, I understand that the panel will not charge the battery if the voltage of the battery is higher that the output from the panel, so this explains why the battery is never getting charged from the panel.
That is except for in some cases it does kick in, then stop. I have just turned the fridge on with the battery sitting at 12.9V and the solar panel indicator light on the CTEK unit came on for awile (I didn’t sit and watch it) but it was less than an hour.
We have removed the Photonic Universe MPPT to see if it was faulty and disrupting the flow to the battery but it has made no difference.

• The panel has no obvious damage to explain the low/intermittent output.
• My mate has tested the voltage at the panel junction box and at the battery to rule out wiring issues

Q2: Could the apparent panel fault result from a sub-parr battery? Or do I have a bad panel?

If you’ve made it this far, thanks for sticking with me even if you don’t have a clue either
Colin

 

[Dellmassive]

Q1 - possibly . . if you run any SLA battery flat (bellow 10v) you reduce its capacity, running it very low only a few times will kill it.
The only way to tell properly is to do a capacity test.

1-fully charge to 100% (battery draws less than say 1amp)
2- discharge via load/shunt/power meter - to meter out the capacity in Ah. (a good battery will give you 50% of rated)
3- fully recharge again metering out the charged Ah
4- compare reading with the battery spec. (so 95ah battery expect 40ah ish)

remember with SLA you can only use 50% of the rated power - so 45Ah for your 95Ah battery


if you get less than the 50% you are expecting - then replace the battery.

if it needs replacing . . . then choose an AGM option for cheaper, or Lithium for Premium - dont bother with standard or leisure or heavy duty lead acid its not worth it - still with AGM or Lifpo4.

Q2 - possibly.

its easy enough to test the panel - you need a multi meter.

1-wait for a sunny day, disconnect the panel from the controller.
2- use meter to test the VOC - Voltage open circuit (so across the two bare wires) - it should be as per the panel spec ( say18-24v)
3 - then use the meter to test the ISC - current short circuit (use a clamp meter or line meter to measure the max current) (you should get aroun 6A per 100w)



more info here:

Dellmassive’s "How I Done It" blogs.

-- Dellmassive`s -- "How I Done It" -- thread -- ************************************************** Dellmassive`s -- "how I Done It" -- Thread ************************************************** Kit List And Stuff -- How I Done It & What I Use --...

www.t6forum.com

 

[Deleted member 6336]

Q1 - possibly . . if you run any SLA battery flat (bellow 10v) you reduce its capacity, running it very low only a few times will kill it.
The only way to tell properly is to do a capacity test.

1-fully charge to 100% (battery draws less than say 1amp)
2- discharge via load/shunt/power meter - to meter out the capacity in Ah. (a good battery will give you 50% of rated)
3- fully recharge again metering out the charged Ah
4- compare reading with the battery spec. (so 95ah battery expect 40ah ish)

remember with SLA you can only use 50% of the rated power - so 45Ah for your 95Ah battery


if you get less than the 50% you are expecting - then replace the battery.

if it needs replacing . . . then choose an AGM option for cheaper, or Lithium for Premium - dont bother with standard or leisure or heavy duty lead acid its not worth it - still with AGM or Lifpo4.

Q2 - possibly.

its easy enough to test the panel - you need a multi meter.

1-wait for a sunny day, disconnect the panel from the controller.
2- use meter to test the VOC - Voltage open circuit (so across the two bare wires) - it should be as per the panel spec ( say18-24v)
3 - then use the meter to test the ISC - current short circuit (use a clamp meter or line meter to measure the max current) (you should get aroun 6A per 100w)



more info here:

Dellmassive’s "How I Done It" blogs.

-- Dellmassive`s -- "How I Done It" -- thread -- ************************************************** Dellmassive`s -- "how I Done It" -- Thread ************************************************** Kit List And Stuff -- How I Done It & What I Use --...

www.t6forum.com

Thanks for taking the time to reply, I really appreciate it.
I had already come to terms with the real possibility that I would end up having to re-do my entire solar power set up and have been looking at options but was really just wondering is you or anyone could shed some light on the way the panel seems to sometimes work? My mate tested the the circuit across the two bare wires And got the 16V then 11V readings, but he doesn’t have a clamp meter. (The VOC quoted on the panel data sheet is around 20V)
I though these thing were either working or dead (other that the gradual decline in performance over time?
Battery:
My mate initially recommended upgrading to AGM until I found THIS which has made him reevaluate his stance on AGM.
I found a reasonably priced Lithium so had decided that would be the way to go until I found THIS which is a worry and pushes the price up even more by adding a new smart DC-DC with optional temp sensor fitted to the alternator.
I’ll have a look at your “how I done it” section in more detail, but I have been working along the lines of:
Changing the panel from semi rigid to a higher output rigid mounted on a roof rack compatible with my Drivelodge roof (this will be the second panel I’ve had fail and when they’re bonded to the roof it’s a massive pain)
I had hoped to leave the CTEK in but if I go lithium that’s probably not an option so looking at the victron Orion DC-DC. The CTEK is also only rated for a max 23V VOC from the panel which is a bit limiting if I put a bigger panel on.
Victron Smart MPPT charge controller.
I’d be interested to hear your thoughts on this layout.
Cheers
Colin

 

[Dellmassive]

solar panels can fail in numerous ways.

normally micro fractures of a cell or two,

or again micro fractures in the cell bond wires which are like tin foil . .

so heat, light, sun can cause the voltage to rise and fall.

water ingress and corrosion are all possible.


+++

if the panel spec VOC is 20v . . . . . then in strong sunlight you should get 20v

if you getting 11-16v id assum there is a fault with it.

++++


one way to tell is just connect a different panel as a temp test. . . then retest.


++++


from what you are describing my gut feeling is the panel is faulty.