Solar panel controller - higher voltage than expected?

Cardo

Cardo

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www.yacht-tinkerbell.co.uk
So, we have one of these dealing with our (normally 300w, but currently 200w) panels:
http://www.ebay.co.uk/itm/MPPT-30A-...921?pt=LH_DefaultDomain_0&hash=item1c317a3559

We have 500Ah of sealed lead acid batteries that are currently being kept topped up by the controller, with very little (pretty much negligible) output at the moment.

Problem is, the voltages seem to be going surprisingly high, and I'm concerned it may be wrecking our batteries.

Quite often when I've had a look I'll find the voltage at the batteries is 14.4 - 14.5v. This is usually when it's suddenly got brighter as clouds have parted. If I keep an eye on things, the voltage usually drops down to around 13.8v after a minute or two. When things go cloudy and then brighten up again, same thing happens again.
Today I popped along to check on some stuff. It's been peeing down with rain and it's been really grey, but we had a sudden moment of sunshine as I got to the boat. I checked the voltage and this showed 14.8v!
I checked the batteries themselves and they didn't feel warm or anything like that.

For the time being, I've disconnected the solar panels as I'm concerned about damage being caused. Though, to be honest, if this has been causing damage, the damage will already be done!
When I disconnected the solar panels, the voltage dropped to 13.8v. I didn't hang around to see what they ended up resting at.

The controller is set to the sealed batteries setting and I've told it how much Ah the bank is.

Thoughts?
 
Just my twopennorth.... but the spec for solar panels I've got says output 18V. My rudimentary understanding is that Amps are proportional to potential difference ( ie difference between battery voltage and panel output) so charge going in will fall as battery voltage rises therefore it all sort of quietens down.
Mains chargers will put voltage at battery at about 14V as there has to be a higher pressure to push those pesky electrons in there but disconnect charger and battery voltage drops to under 13V.
Neither solar panels nor mains chargers have done owt bad to my batteries so far.
I'd be interested if anybody more clued up than I can expand on an explanation.
 
If, whilst being charged, the batteries are in need of very much charge then they'll show 14.5V or a bit more. If they're really fully charged then they'll show nearer 13.8V.[again whilst being charged]. It looks as if your batteries are supplying some output and therefore taking all that the solar cells can produce in order to get themselves recharged - the charging current and voltage are being determined by the intensity of the sunshine rather than the state of charge of the batteries. No worries.
 
Mine does the same. We are currently on a pontoon berth with shore power. My charger floats the 360AH bank at 13.4 to 13.6 normally. I have noticed though that if we get a burst of sunshine on the 240w of panels the volts will go up to 14.5ish for say 5mins and then the solar controller will dump the input from the panels and the voltage goes back to float level. If I check the solar input on the meter it will have dropped to very low or zero. Just seems to take a few minutes for the controller to sense that the batteries are fully charged. ---- I think!
 
Hadenough said:
Mine does the same. We are currently on a pontoon berth with shore power. My charger floats the 360AH bank at 13.4 to 13.6 normally. I have noticed though that if we get a burst of sunshine on the 240w of panels the volts will go up to 14.5ish for say 5mins and then the solar controller will dump the input from the panels and the voltage goes back to float level. If I check the solar input on the meter it will have dropped to very low or zero. Just seems to take a few minutes for the controller to sense that the batteries are fully charged. ---- I think!
Click to expand...

"Glad" to know I'm not the only one!

So, do short periods (5 mins?) of higher than recommended voltages cause harm to sealed batteries? I'm hoping the lack of (noticeable) rise in temperature means the batteries shouldn't be too upset.
 
Sounds like you dont have a problem. :encouragement:

Please stop talking about sunshine......we have forgotten what the sensation is like! :p
 
Cardo said:
"Glad" to know I'm not the only one!

So, do short periods (5 mins?) of higher than recommended voltages cause harm to sealed batteries? I'm hoping the lack of (noticeable) rise in temperature means the batteries shouldn't be too upset.
Click to expand...
Check the battery Datasheet, the should be some info there.
 
Panel voltage

I have 2 off 90W panels: each has a 'simple' voltage regulator feeding into a 375 Ah bank. I leave them on full time. I have a Xantrex Linklite monitor (it controls nothing, just measures what is). There is nothing switched on apart from the Xantrex and the panels, except when I'm messing about on board. The voltage will read between 13.8 and 14.2 when I arrive (afternoon) but drops to 12.9/12.7 when a user is put in service. It also drops overnight (no users) to 12.7/12.8. So the higher voltages are froth: no visible damage (and none expected) after 2 years.
 
Cardo said:
So, we have one of these dealing with our (normally 300w, but currently 200w) panels:
http://www.ebay.co.uk/itm/MPPT-30A-...921?pt=LH_DefaultDomain_0&hash=item1c317a3559


Quite often when I've had a look I'll find the voltage at the batteries is 14.4 - 14.5v.

Today I popped along to check on some stuff. It's been peeing down with rain and it's been really grey, but we had a sudden moment of sunshine as I got to the boat. I checked the voltage and this showed 14.8v!
Click to expand...

RTM

Is this not the "boost" stage of the charging cycle ??

Cant you set voltage of this stage to whatever you choose between 13.8 and 15.0 volts ?

RTFM Read the FULL manual I think you might find the explanation and the solution is in there.

.
 
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It may be that the MPPT algorithm has shortcomings. These are complicated devices: the controller periodically (every few seconds) examines the output of the solar array, and determines an appropriate operating voltage for the array. Then presumably the output stage does its own voltage regulation based on the battery charging requirements. It could be that the sunshine is changing more rapidly than the controller is reassessing conditions. Whether it matters is another question!
 
Almost identical set up but different MPPT with very similar results. When it first happened, I returned the Controller for a new one but no change. I haven't seen the 14.8 peaks recently (oh that will be the rain) but it does go into a 14.4, 14.3, 14.2, 14.1, 14.0, 13.9, 13.8 count down every now and again. Likewise my batteries seem to be OK.
 
Poor voltage control like this is common with the lower cost controllers.
It is not ideal especially for sealed batteries.

Good quality controllers of this sort of size like the Rogue, or the new 30A Midnite have a more accurate and adjustable voltage algorithm. They will also extract a bit more power from the panels, but of course they are more expensive.
 
Spuddy said:
Just my twopennorth.... but the spec for solar panels I've got says output 18V. My rudimentary understanding is that Amps are proportional to potential difference ( ie difference between battery voltage and panel output) so charge going in will fall as battery voltage rises therefore it all sort of quietens down.
Mains chargers will put voltage at battery at about 14V as there has to be a higher pressure to push those pesky electrons in there but disconnect charger and battery voltage drops to under 13V.
Neither solar panels nor mains chargers have done owt bad to my batteries so far.
I'd be interested if anybody more clued up than I can expand on an explanation.
Click to expand...

High Spuddy. We had better explain things a bit. You are obviously referring to a connection direct solar panel to battery. The no load voltage of the panel is close to 20volts so it is able to push current into the battery dependant msotly on amount of sunshine and panel size. This is fine for a small panel and large battery where a small percentage of AH rating in amps continuous will not harm the battery. If you go to a larger panel witha smaller battery the solar power ona sunny day can overcharge the battery. this results in loss of water and overheating. Probably battery damage. So we fit a regulator. This limits the voltage presented to the battery so that as the battery gains charge its inherent voltage rises so the difference between the battery voltage and the regualted voltage falls so current falls.
You will have heard of smart charger technology. This is where a higher voltage is presented to the battery to get max current in in the shortest time but which senses that the battery is charged and reduces the voltage to a float voltage when it is charged. This technology is used for alternator charge controllers maijns battery chargers and solar powered charge controllers.

Noew the next improvement in solar charge controil is the MPPT type controller. (Max Power point tracking) The controller takes the DC from the panel and converts it to AC to transform it down or up to the required voltage to charge the battery. It does this with aclever algorythm to extract the max power from the panel to get amx current into the battery (when required battery charge voltage is usually also determined by the "smart" algorythm)
Thus 20 volts at 5 amps from a 100 w panel in full sun can be converted to 13volts at nearly 7 amps. (there are losses). On a cloudy day 10 volts at 1 map from the panel can converted up to give 13volts at about .5 amp.
In the first case if it was a direct connection solar panel to battery if the battery were 13v then 7 volts at 5 amps or 35 watts would be wasted in the internal ressitance of the panel. In the second case there would be no charge because panel volts would be too low. Of course it is more complex than these 2 extreme cases but that is a rough indication of what MPPT does.

To the OP if the voltage is too high (check your multimeter or voltmeter) then the smart algorythm is causing the problem. It may be simply that with cloud then sun returning the whole charge regime starts again. Though I really don't know. A longer period of checking the battery charge voltage might help indicate if you have a problem.

Menawhile here in Perth news advises we have reached some sort of record with 100 days with no rain. None expected for a few more months. Not a drought just nromal summer weather. good for solar power. (and sailing) olewill
 
William_H said:
On a cloudy day 10 volts at 1 map from the panel can converted up to give 13volts at about .5 amp.
Click to expand...

Many people believe their MPPT controller will boost voltage, but only a couple of specialist models will do this. 99% of boat MPPT controllers will only reduce voltage.
 
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VicS said:
RTM

Is this not the "boost" stage of the charging cycle ??

Cant you set voltage of this stage to whatever you choose between 13.8 and 15.0 volts ?

RTFM Read the FULL manual I think you might find the explanation and the solution is in there.

.
Click to expand...

I've read the manual, plenty of times. It's not the most in-depth novel ever written. The only settings available are
- Type of battery
- Bank capacity
- Voltage adjustment based on ambient temperature (Currently set to 0, any ideas what it could/should be set to?)

Then there's settings to do with the load terminals, but I figure they're irrelevant to the current query.


So, it sounds like it's just the result of rapidly fluctuating brightness and a cheaper-end regulator that doesn't react particularly quickly to these changes. Not ideal with sealed batteries, but it shouldn't be too much of an issue once we head out and have continuous loads on the batteries. Next lot of batteries will be regular LAs I think.
 
Cardo said:
I've read the manual, plenty of times. It's not the most in-depth novel ever written. The only settings available are
- Type of battery
- Bank capacity
- Voltage adjustment based on ambient temperature (Currently set to 0, any ideas what it could/should be set to?)

Then there's settings to do with the load terminals, but I figure they're irrelevant to the current query.


So, it sounds like it's just the result of rapidly fluctuating brightness and a cheaper-end regulator that doesn't react particularly quickly to these changes. Not ideal with sealed batteries, but it shouldn't be too much of an issue once we head out and have continuous loads on the batteries. Next lot of batteries will be regular LAs I think.
Click to expand...

Sorry somehow my search for the user manual went off the rails and Iended up with the manual for the eTracer range.

What you have is intended for use as a street light controller. Hence all the setting up instructions for the load terminals. Perhaps you will be able to automate the operation of your deck lights.

I guess when used for street lights it would normally begin its charge routine with a partially discharged battery, having been powering the street lights during the night. It would therefore begin in the "bulk charge" part of its cycle not reaching the boost stage for sometime so if it was low reacting to changes it might not notice.
 
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VicS said:
Sorry somehow my search for the user manual went off the rails and Iended up with the manual for the eTracer range.

What you have is intended for use as a street light controller. Hence all the setting up instructions for the load terminals. Perhaps you will be able to automate the operation of your deck lights.
Click to expand...
Use it to turn on the anchor light when it gets dark. :D
I guess when used for street lights it would normally begin its charge routine with a partially discharged battery, having been powering the street lights during the night. It would therefore begin in the "bulk charge" part of its cycle not reaching the boost stage for sometime so if it was low reacting to changes it might not notice.
Click to expand...
Once we're back out and away, our batteries will rarely be fully charged, so it shouldn't be an issue then.
 
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