Solar panel/battery advice
Hi looking for advice i have just changed my battery and got a 120ah agm type the problem is the panel won't charge the battery above 12.2 the panel is a 160 watt when the sun is on the panel the charge controler shows green and won't put anymore charge in but as soon as the sun goes in it shows red and only shows 12.2 on the caravan panel any ideas could it be the charge controler
Thanks
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either the battery is suspect or the controller...
as above....
charge the battery fully using an offline charger or EHU on the van. wait 24hrs the resting voltage should be 12.6 or even 12.7
if it isn't getting above the 12.2 as in your post, then the battery has failed. showing red and 12.2 must be a big clue?
however, if the battery gets to 12.7 via a different charger and stays there after a rest period, then the solar charger can't be charging it fully.
im no electrician but when I asked about a second panel (2x 100w) I was told my 10amp regulator would need to be changed for a 20amp one. could this be the case for you?
i have 2x 95 ah leisure batteries.
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It is not clear what voltage you are measuring, is it the solar panel when not connected to the battery or is it the battery voltage with panel connected? It sounds like the latter in which case the battery has had it and the panel cannot rescue it. Do as BB above suggests.
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Hi thanks for all your reply's back home now will take the battery off and give it a full charge,it was showing full green on the charge controler and 12.6 on the caravan power panel and taking no more charge but if you put the panel in the shade it would start to flash on the solar cotroler as though it was putting more charge in and would drop to 12.2 on the caravan power panel the solar charge controler is 10amp the reading iam showing is with the solar panel connected to the battery
Thanks
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as hitch says, the 'showing full' and the 12.6v reading could be the raised voltage charge from the regulator....
you could just disconnect (pull a fuse) on the connections to the battery, wait a bit and measure again....this would then be the real charge in the battery not what's coming in via the panel/controller.
i also agree with Ocsid re the amperage of the controller, it needs to be a 20amp one...
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photonic universe sell 160 solar kits with only 10amp controller so don't think that's the problem.
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I wouldn't be happy with this. To estimate the rating of a controller you divide the total solar panel wattage by the battery voltage and add 25 percent which for a 160w panel comes to near enough 17 amps. Even without the 25 percent margin the current is just over 13 amps! A 20 amp controller is required.
peedee
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I agree 10A seems a bit "near the knuckle" but don't forget solar panel output voltage is something like 18-21V so 160/18 is less than 10A, and you won't get absolute peak output from the panel unless the light is coming perpendicular to the panel, so by the time you factor all that in it'll be OK... Just don't go to one of the Tropics (Cancer or Capricorn) on midsummer's day!
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Not reassuring to me, actually raises other concerns.
At the higher current "bulk" phase with an expected output of 14.6 volts the current will be about 11 Amps, even higher, 11.6 A if using as low a bulk phase as 13.8 volts.
Is the efficiency of the controller low enough to keep within the rating, or the panel not as rated?
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The output of a solar panel is about 20 volts, so the current from 160 watt panel will be nearer 8 amps maximum. Given the dire efficiency of the controller I doubt that the current will increase much, if any when at the 14 plus volts of the output.
My 100 watt panels 10 amp controller give a maximum output of about 5.5 amps. I think that represents about 75% efficiency which is quite good.
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When I fitted a 135w panel to my last van, I tried to buy a 20amp controller. The supplier refused to sell me one saying a 10amp one would be fine. He said that the amp rating is based on the input not the output amps. I have no reason to disbelieve him as it saved me money.
Also as a general observation it seems strange that the OP states that he changed the battery and has a problem since then. People leap to the conclusion it must be the controller. Possible but not likely imho
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You cannot work Ohms law using battery voltage to determine the panels output in amps.
160w panel is 'Peak power' and will never be realised in this country, the amps will be calculated by the maximum voltage output of the panel which is around 18-20 volts. If the voltage drops due to lack of sun the 160w output will also drop, hence so will the amps. In reality it will never exceed 8/9 amps and even less due to inefficiency.
10 amp controller is fine.
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You cannot work Ohms law using battery voltage to determine the panels output in amps.
The 10 amp rating is the output of the controller not the input! At least that is the norm. There are so many variables in determining the output of a panel, not least the intensity of light and the angle onto the panel, that using panel watts divided by battery volts is just a way of estimating controller requirements, another is to divide the watts by 16.5? Either way I would not be happy with a 10amp controller on a 160watt panel. To me a 10amp controller is I assume leaving very little margin to allow heat to dissipate unless it is not a very efficient panel.
peedee
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Exactly, because all the controller does besides its 10 amp output rating is reduce the voltage of the panel to an acceptable level for charge. I am pointing out that a 160w (PEAK) panel can in no way exceed the input because of its inefficiencies and therefore will not exceed the 10a output of the controller.
PEAK wattage figures are stated for the perfect conditions, for instance full sun, at the equator, and temperature, add in the inefficiency and you end up with a 100/120w panel in this country.
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Although the solar panels on the roof of my house occasionally reach peak output on some days from March to October, they still generally are producing about 85% of their rated output. That is on a south facing roof with a 30 degree pitch. A panel laying flat on a caravan/motorhome roof is going to be less efficient than that.
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"PEAK wattage figures are stated for the perfect conditions, for instance full sun, at the equator, and temperature, add in the inefficiency and you end up with a 100/120w panel in this country"
This is simply not correct, the panels performance can be optimum on the Poles not the Equator. It is being "normal" to the sun, a haze free "reach" through the atmosphere and very importantly being cold that produce the highest yields.
That temperature factor significantly degrades the yield on the Equator compared to the Poles or even here.
For those wanting to understand; note the panel's performance is rated at 25C, and typical temperature coefficients are -0.5%/C.
Plus, the cells get hot as a side effect of working so reaching and exceeding 50C is typical in Equatorial areas with an ambient easily at 40 + C.
So, even at just 50C surface temperature on the panel will yield 12.5% below its rating.On the Poles it could be well below freezing, but if at 0C it could yield 12.5% above its rating. Helped by the low temperature largely eliminating moisture haze in the atmosphere.
Therefore we can see levels of 25% better performance on the Poles than the Equator.
I have an free standing 11 year old 85Watt Kyocrea panel, controlled by a Morningstar PWM controller with associated meter.
Regularly here in the UK, the controller outputs to the battery a few Watts over the panels rated 85 Watts.Little doubt this is the consequence of the cooler than 25C temperature here, my placing the panel normal to the sun and use of a high performance controller.
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If the output from the controller was actually 12.2 volts and the battery was healthy then the battery would be pushing current into the controller which in theory can’t happen due to the diodes blocking reverse current flow. So, it is still possible that the battery is faulty. It charges up to 12.6 volts (which is actually a bit low for a freshly charged battery assuming the meter is accurate) but does it retain this for any length of time and does the voltage drop off dramatically on light load without the solar panel connected? If the battery is healthy then it can only be a faulty controller but I still wonder where the reverse current is discharging to.
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Not completely correct ocsid, what you going to do move the panels from the north to the south pole or vice versa when for approx half the year there is darkness, now there's inneficiency.
Also the sunlight above the equator is direct and focused with less atmosphere to diffuse the light, unlike the poles where the sun is at a slant and solar rays are spread over a wide area.
Yes above 85 degrees centigrade solar panels lose some efficiency but being on or near the equator they stand a good chance of working 365 days a year , and solar panels being solar panels need sunlight and the poles can be pretty dark for a long long time.
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