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Thanks Mike and sorry to be away for a day. I've been testing, rewirng, moving the van around to do some roof-top sunbaking, (not me, the panels), and writing notes throughout yesterday and this morning of things like Voc, Vmp, Imp, HV (House Voltage), and keeping my eyes and fingertips on the topside of the MPPT controller to monitor its temperature compared to my stable 'control' which is the box of the 1000W inverter. The inverter is always at least 33% hotter than the MPPT controller. Meaning that the MPPT feels around 75% of the temperature the inverter at the most, the sunniest 30.1A Imp times.
Yesterday I ran all three 'sets': 60W x 2 portable, 150W x 2 rear, & 200W x 1 front. in parallel, and did reach 30.1A on the MPPT controller screen at one stage, That was the point when the MPPT controller got the hottest and started to smell just a little tiny bit like a gluten-free bakery, which was pleasant and only very slightly alarming, I popped the fuse for the portable and reduced the Imp reading on the controller back to around 23-25A for the rest of the afternoon. Your calculations were right on the proverbial nail. The House Voltage (battery voltage + MPPT input - load) held at around 13.8V all afternoon. This was the voltage of the Dia-Mec batteries when purchased, incidentally.
Alas when the Sun set, HV dropped down to around 12.5V, partly because of the 6pm movie commencing. The van received his usual 60 minutes of diesel charging between 17:00 and 18:00 yesterday afternoon, and then another 30 minutes between 19:00 and 19:30. I'm starting to understand 'his' preferred routine after almost three seasons of co-habitating in sin like this. The batteries are never going to hold 13.8V overnight again, not even if I unbolt the terminals, If I can keep things over 12V until morning, like yesterday morning, then that is all I can ask until I can replace these two cheapie batteries with some good quality items when the whole electrical system is finally built and tested to production standard,
Bedtime at around 20:30 saw the House Voltage at 12.2V when I switched off the bedside LED lamp, leaving only the food cooler running on level 6 of 7 as usual, Lo and behold if I did not wake at the habitual time of 00:44 to hear that the food cooler fan was running and House Voltage down to 11.6V. I lay awake until 02:44 and the food cooler fan never stopped for those two hours, and the HV fell to 11.2V. I got out of bed and reset the cooler coolness setting around from 6 to 7, 1, 2, 3, 4, 5 and as hoped, the fan stopped for the rest of the night, as far as I could tell. House Voltage on my $15.00 red LED voltmeter that I can see at the end of the bed in the dark returned to 11.6V and stayed there until dawn. The MPPT controller approved of the battery voltage in the morning and happily commenced recharging the batteries without any need for diesel help for the second morning in a row, which passed 12V again well before breakfast time.
The woman who lives in the transportable dwelling next door to me visited while walking her pesky little long-haired dog this morning to confirm that I was still interested in her *no-longer-useful Engel fridge, and that might solve this latest Waeco cooler fan stuck on ON problem in the near future. It hasn't happened before that I was awake to notice. Anyway, the poor old abused Chinese 100AH batteries that I have been so neglectful towards over the past seven(7) and two(2) months still seem to be able to keep their nightly promises. When I get the chance I'll save some money for some Japanese batteries, or maybe if I get real lucky, I could try some LiFePO4s when they finally become old technology and their price stabilises at some dependable South American standard.
* husband died. No more camping out for a woman alone.
This morning I got up on the park's resident ladder once more and reconnected the pair of 150W rear roof-top panels in series, and things tested much better today than earlier in the week. The MPPT controller was even able to modulate almost effortlessly between the 39V of the series panels, the 20V of the portable panels (|| config), and the single 200W panel's 22V. I've recorded the different Voc values with the fuses removed, and then the Vmp values when all hooked into the same +ve and -ve junctions - parallel 'sets', one set being wired in series.
Now here comes the best part. In the Owners' Manual it states that a common ground between the high-voltage DC panel circuit (MPPT input) and the 12VDC 'house' circuit (MPPT output) is just hunky-dory so I read it again to make sure I wasn't having some senior moment with my reading comprehension.
They weren't kidding, Mike! Now I have rehooked all the -ves from the MPPT into the same ground on the side pillar of the van, behind the passenger seat. What this means is that I will no longer need to run -ve wires from the panels down into the cab. This will reduce the number of wires from the current eight(8) big thick 20A heavy-duty outdoor wires down to four(4), only half area through the grommet ... but wait! There's more ...
By connecting both the front 200W and rear 150W roof-top panels in series, there will only be need for two big red +ve wires coming down from the roof through the slit in the front of the sliding door now, which will be most welcome, because the door will not shut without a very hard push now, since there are a bundle of eight(8) wires wrapped in green PVC tape around 3/4" diameter, and the sliding door is gradually trimming the green PVC to smithereens. It could never have lasted. Only the fuses have allowed me to sleep in peace for half the night.
Changing to series wiring and earthing the panels up on the roof is going to reap a very wonderful benefit because of the physical incongruity of eight thick cables totalling 3/4" diameter squeezed through a slit in the side doorway which is only around 1/4" on happy days. I'll only need two(2) wires now. Both +ve for the front and rear panel pairs in series configuration.
My plan is to have the wiring redone as well as the roof-rack rebuilt to properly accept the larger 200W panels with 100mm longer 140mm wider dimensions before Friday next week, so that I can drive into town and collect that last panel, and it will fit onto the roof in around 30 minutes in the carpark.
CONCERNS REGARDING TEENIE-WEENIE DIODES.
Then there are only the portable 60W pair left in parallel. After yesterday's voltage disharmony between the 'sets' of panels when one set was wired in series totalling 40V Voc and the others were either alone or parallel at Voc 20V, I decided that I would need to take your advice, Mike, and rewire the portables into series so that eventually all three(3) sets of pairs will be Voc around 40-44V.
What has stopped me in my tracks this morning, so that the portable 60W panels are still in the OEM parallel, is that I can still feel the hard skin and the numbness on my right index finger after using the portables in excellent insolarence this morning for an hour, and then flipping them on their fronts in a hurry, unscrewing the lids of the small black 100mm square terminal boxes (as shown in phoitos above) and then testing the heat on the diodes with aforementioned right index fingertip. Ouch. It was hot. I can still feel the burnt finger.
"Oh no!", I thiought to myself, "If I hook these two panels in series, then the diodes are going to get twice as hot and then the whole thing will melt!"
I am wondering though, if there is any real truth in my hypothesis. At the MPPT end, what we get from two panels in a series circuit is double the voltage at half the amperage, to produce the same power in watts, with slightly less loss depending on the wire gauge because higher voltage at lower current produces the same watts with less heat, (less current). The higher volts flow faster with less current just as water will flow faster over a waterfall than it does in a canal or estuary. This is my electrical theory at its most advanced level, and could be quite incorrect.
Now, here is the difference between the MPPT end and the series solar end, in my uneducated head, that is. When I am running the 2 x 60W panels in parallel I produce X amperes of current which must pass through each panel's respective 6-AIC MIC diode and this makes it too hot to touch for more than around 2 secs. Apparently it is around 6.8A Imp according to the decal on the back and this is for the total 120W panels because 120W / 17.6V Vmp = 6.8181818 A. I hope I am right here because each 60W panel has its own decal so I would have guessed the specs for 60W, but the maths doesn't add up for that. I guess each decal refers to the 120W pair as a couple.
If I change to series wiring, by connecting one +ve to the other -ve and then connecting the output wires to the remaining -ve & +ve, including both diodes in the circuit, it seems to my logic that this would mean that the current produced by each panel does not just pass through the diode once now, but twice.
I must be wrong about this, In series we get double the voltage and half the current. I must be wrong in my paranoia. Please help.
If I rewire the 120W portable with its twin 60W panels into series so that the combined voltage more closely matches the other two pairs of fixed roof-top panels, will this put double the energy, double the heat energy that is, through those poor little teenie-weeny diodes ?
I hope that this coming week will allow me to rebuild the roof-rack, and rewire the electrics on the roof into series, and have enough connectors, nuts & bolts to do the job. If it works, I am going to draw diagrams, take photos, complie test reports and begin a new post hoc thread in the Off-Grid Solar 12V Mobile subforum where everything I have written so far would be more relevant.
I still don't know whether it would be safe for the diodes to change the portable panel to series but that is only a 10 minute job and it still adds a couple of amps to the total when hooked into the high-voltage system as it has worked out today.
I am so happy to have found a way to cut the number of big, thick cables all squashed up in the crack of the sliding door by 75%. Hooray!
See why I call this current stage of the Great Solar Transit Project, the 'prototype'?
How long do you reckon THAT would have lasted?
Yesterday I ran all three 'sets': 60W x 2 portable, 150W x 2 rear, & 200W x 1 front. in parallel, and did reach 30.1A on the MPPT controller screen at one stage, That was the point when the MPPT controller got the hottest and started to smell just a little tiny bit like a gluten-free bakery, which was pleasant and only very slightly alarming, I popped the fuse for the portable and reduced the Imp reading on the controller back to around 23-25A for the rest of the afternoon. Your calculations were right on the proverbial nail. The House Voltage (battery voltage + MPPT input - load) held at around 13.8V all afternoon. This was the voltage of the Dia-Mec batteries when purchased, incidentally.
Alas when the Sun set, HV dropped down to around 12.5V, partly because of the 6pm movie commencing. The van received his usual 60 minutes of diesel charging between 17:00 and 18:00 yesterday afternoon, and then another 30 minutes between 19:00 and 19:30. I'm starting to understand 'his' preferred routine after almost three seasons of co-habitating in sin like this. The batteries are never going to hold 13.8V overnight again, not even if I unbolt the terminals, If I can keep things over 12V until morning, like yesterday morning, then that is all I can ask until I can replace these two cheapie batteries with some good quality items when the whole electrical system is finally built and tested to production standard,
Bedtime at around 20:30 saw the House Voltage at 12.2V when I switched off the bedside LED lamp, leaving only the food cooler running on level 6 of 7 as usual, Lo and behold if I did not wake at the habitual time of 00:44 to hear that the food cooler fan was running and House Voltage down to 11.6V. I lay awake until 02:44 and the food cooler fan never stopped for those two hours, and the HV fell to 11.2V. I got out of bed and reset the cooler coolness setting around from 6 to 7, 1, 2, 3, 4, 5 and as hoped, the fan stopped for the rest of the night, as far as I could tell. House Voltage on my $15.00 red LED voltmeter that I can see at the end of the bed in the dark returned to 11.6V and stayed there until dawn. The MPPT controller approved of the battery voltage in the morning and happily commenced recharging the batteries without any need for diesel help for the second morning in a row, which passed 12V again well before breakfast time.
The woman who lives in the transportable dwelling next door to me visited while walking her pesky little long-haired dog this morning to confirm that I was still interested in her *no-longer-useful Engel fridge, and that might solve this latest Waeco cooler fan stuck on ON problem in the near future. It hasn't happened before that I was awake to notice. Anyway, the poor old abused Chinese 100AH batteries that I have been so neglectful towards over the past seven(7) and two(2) months still seem to be able to keep their nightly promises. When I get the chance I'll save some money for some Japanese batteries, or maybe if I get real lucky, I could try some LiFePO4s when they finally become old technology and their price stabilises at some dependable South American standard.
* husband died. No more camping out for a woman alone.
ON SERIES WIRING
This morning I got up on the park's resident ladder once more and reconnected the pair of 150W rear roof-top panels in series, and things tested much better today than earlier in the week. The MPPT controller was even able to modulate almost effortlessly between the 39V of the series panels, the 20V of the portable panels (|| config), and the single 200W panel's 22V. I've recorded the different Voc values with the fuses removed, and then the Vmp values when all hooked into the same +ve and -ve junctions - parallel 'sets', one set being wired in series.
Now here comes the best part. In the Owners' Manual it states that a common ground between the high-voltage DC panel circuit (MPPT input) and the 12VDC 'house' circuit (MPPT output) is just hunky-dory so I read it again to make sure I wasn't having some senior moment with my reading comprehension.
They weren't kidding, Mike! Now I have rehooked all the -ves from the MPPT into the same ground on the side pillar of the van, behind the passenger seat. What this means is that I will no longer need to run -ve wires from the panels down into the cab. This will reduce the number of wires from the current eight(8) big thick 20A heavy-duty outdoor wires down to four(4), only half area through the grommet ... but wait! There's more ...
By connecting both the front 200W and rear 150W roof-top panels in series, there will only be need for two big red +ve wires coming down from the roof through the slit in the front of the sliding door now, which will be most welcome, because the door will not shut without a very hard push now, since there are a bundle of eight(8) wires wrapped in green PVC tape around 3/4" diameter, and the sliding door is gradually trimming the green PVC to smithereens. It could never have lasted. Only the fuses have allowed me to sleep in peace for half the night.
Changing to series wiring and earthing the panels up on the roof is going to reap a very wonderful benefit because of the physical incongruity of eight thick cables totalling 3/4" diameter squeezed through a slit in the side doorway which is only around 1/4" on happy days. I'll only need two(2) wires now. Both +ve for the front and rear panel pairs in series configuration.
My plan is to have the wiring redone as well as the roof-rack rebuilt to properly accept the larger 200W panels with 100mm longer 140mm wider dimensions before Friday next week, so that I can drive into town and collect that last panel, and it will fit onto the roof in around 30 minutes in the carpark.
CONCERNS REGARDING TEENIE-WEENIE DIODES.
Then there are only the portable 60W pair left in parallel. After yesterday's voltage disharmony between the 'sets' of panels when one set was wired in series totalling 40V Voc and the others were either alone or parallel at Voc 20V, I decided that I would need to take your advice, Mike, and rewire the portables into series so that eventually all three(3) sets of pairs will be Voc around 40-44V.
What has stopped me in my tracks this morning, so that the portable 60W panels are still in the OEM parallel, is that I can still feel the hard skin and the numbness on my right index finger after using the portables in excellent insolarence this morning for an hour, and then flipping them on their fronts in a hurry, unscrewing the lids of the small black 100mm square terminal boxes (as shown in phoitos above) and then testing the heat on the diodes with aforementioned right index fingertip. Ouch. It was hot. I can still feel the burnt finger.
"Oh no!", I thiought to myself, "If I hook these two panels in series, then the diodes are going to get twice as hot and then the whole thing will melt!"
I am wondering though, if there is any real truth in my hypothesis. At the MPPT end, what we get from two panels in a series circuit is double the voltage at half the amperage, to produce the same power in watts, with slightly less loss depending on the wire gauge because higher voltage at lower current produces the same watts with less heat, (less current). The higher volts flow faster with less current just as water will flow faster over a waterfall than it does in a canal or estuary. This is my electrical theory at its most advanced level, and could be quite incorrect.
Now, here is the difference between the MPPT end and the series solar end, in my uneducated head, that is. When I am running the 2 x 60W panels in parallel I produce X amperes of current which must pass through each panel's respective 6-AIC MIC diode and this makes it too hot to touch for more than around 2 secs. Apparently it is around 6.8A Imp according to the decal on the back and this is for the total 120W panels because 120W / 17.6V Vmp = 6.8181818 A. I hope I am right here because each 60W panel has its own decal so I would have guessed the specs for 60W, but the maths doesn't add up for that. I guess each decal refers to the 120W pair as a couple.
If I change to series wiring, by connecting one +ve to the other -ve and then connecting the output wires to the remaining -ve & +ve, including both diodes in the circuit, it seems to my logic that this would mean that the current produced by each panel does not just pass through the diode once now, but twice.
I must be wrong about this, In series we get double the voltage and half the current. I must be wrong in my paranoia. Please help.
If I rewire the 120W portable with its twin 60W panels into series so that the combined voltage more closely matches the other two pairs of fixed roof-top panels, will this put double the energy, double the heat energy that is, through those poor little teenie-weeny diodes ?
I hope that this coming week will allow me to rebuild the roof-rack, and rewire the electrics on the roof into series, and have enough connectors, nuts & bolts to do the job. If it works, I am going to draw diagrams, take photos, complie test reports and begin a new post hoc thread in the Off-Grid Solar 12V Mobile subforum where everything I have written so far would be more relevant.
I still don't know whether it would be safe for the diodes to change the portable panel to series but that is only a 10 minute job and it still adds a couple of amps to the total when hooked into the high-voltage system as it has worked out today.
I am so happy to have found a way to cut the number of big, thick cables all squashed up in the crack of the sliding door by 75%. Hooray!
See why I call this current stage of the Great Solar Transit Project, the 'prototype'?
How long do you reckon THAT would have lasted?
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