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Old 03-02-2014, 04:50 AM   #1
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Solar help please

Well, I retired in December last year, and I am now full timing. My power problems have not gone away, and I have conflicting advice from so many quarters.

I have four 12V solar panels, two 85W and two 90W. I have five 12V AGM 100 AH batteries, but I bought them as two, then one, then another two, over about two and a half years. I have a 3KW Victron inverter and a Victron battery monitor that shows me more information than I can use at present. I should be able to freedom camp without plugging in to shore power, but the guys who did the solar installation knew sweet BA about solar when they started. I finally convinced them to put the controllers as close as possible to the panels, and use wire the thickness of my little finger to go from there to the battery.

However, it seems that the positive wire from the controller goes from the controller at the back of the bus all the way the house cut off relay at the front of the bus, before returning on a smaller cable to the batteries. Doesn't seem like a good idea. It also seems that the negative wire from the controller goes to the chassis, and then there is massive wire that goes from the battery mounts (chassis) to the shunt that controls the battery monitor. One fellow traveller says that the whole house system should be completely isolated from the chassis, and if it is not, my monitor will not read correctly. (He used to install solar systems on boats, where if you connected to the chassis (hull) you turned the entire boat into a battery and it corroded.)

Do I need to have the chassis isolated from the house system?

Everything I have read here suggests that the solar should go straight to the batteries, is there any reason to pass it to the house cutoff at the front of the bus? Should I install a switch of some sort between the solar and batteries to enable me to disconnect the solar if required?

As always, I await the gurus here to help me try and sort out my problems.
Graham Gracie
Coachmen Mirada 1999, F53 chassis.
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Old 03-02-2014, 06:53 AM   #2
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Graham: The house charging unit should be isolated from the batteries when you are using solar. I recently got a nice mini tutorial from VSHEETS. I had used his design as a template for my install and followed his advice. I placed a switch on the charging circuit from my whole house converter. THis isolated the charge circuit from solar charging and still allows my use of the converter when on shore power but only solar ever charges the house system unless I disconnect it.
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Old 03-02-2014, 07:10 AM   #3
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What solar controller do you have? Model number. Hopefully it's an MPPT type and not a power wasting PWM.

You normally mount the solar controller as close to the battery as possible and wire the positive and negative battery connections directly to the battery bank with the positive going through a DC rated circuit breaker or fuse and the negative via a shunt.

One side of your shunt should connect to your battery negative and nothing else to the battery negative. All other negative to the other side of the shunt like chassis ground, solar negative, inverter negative.

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Old 03-02-2014, 07:45 AM   #4
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You have too much battery for that much solar. Your Victron can be set to display SOC state of charge (where mine is set 90% of the time) and you should be reaching 100% SOC with some regularity or you will damage your very expensive batteries. As stated you controller needs to be as close to your battery bank as possible, Mine sits on to of my 150AH Lifeline AGM, the reason for this is voltage drop Voltage Drop Calculator Do the math the higher voltage from the panel to the controller should be held to less than 2%, almost impossible when you are taking the output voltage from controller to battery. Check the actual voltage at the battery, the shunt from the Victron should be at the batteries. Home work time. Deep Cycle Battery FAQ RV Electrical HandyBob's Blog « Making off grid RV electrical systems work
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Old 03-02-2014, 09:29 AM   #5
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Quote:
Originally Posted by GSGracie
I have four 12V solar panels, two 85W and two 90W.
One should generally have at least 100 watts of solar for 100AH of battery capacity. Your batteries are likely connected in parallel for 500AH and you only have 350 watts of solar.

Quote:
Originally Posted by GSGracie
I have five 12V AGM 100 AH batteries, but I bought them as two, then one, then another two, over about two and a half years.
Batteries perform best if they are all the same kind and age. However, your battery situation shouldn't be a severely limiting factor in your system.

Quote:
Originally Posted by GSGracie
I have a 3KW Victron inverter and a Victron battery monitor that shows me more information than I can use at present.
You should learn how your battery monitor works and what it can tell you.

Quote:
Originally Posted by GSGracie
I finally convinced them to put the controllers as close as possible to the panels, and use wire the thickness of my little finger to go from there to the battery.
That was a mistake. The controller should be as close to the BATTERIES as possible, and then size the wire between the panel combiner box and the controller for no more than 2 percent voltage drop, and the wire between the controller and batteries should be the size of your finger for a run of five feet or less. I have less than four feet of 2 gauge wire between my controller and batteries. Between my inverter and the batteries has probably less than two feet of 2/0 gauge wire with a catastrophic fuse.

Quote:
Originally Posted by GSGracie
However, it seems that the positive wire from the controller goes from the controller at the back of the bus all the way the house cut off relay at the front of the bus, before returning on a smaller cable to the batteries. Doesn't seem like a good idea. It also seems that the negative wire from the controller goes to the chassis, and then there is massive wire that goes from the battery mounts (chassis) to the shunt that controls the battery monitor. One fellow traveller says that the whole house system should be completely isolated from the chassis, and if it is not, my monitor will not read correctly. (He used to install solar systems on boats, where if you connected to the chassis (hull) you turned the entire boat into a battery and it corroded.)
Sorry, but what a mess. A solar charging system should generally be connected to the house batteries. Any connection to the chassis should be facilitated through something like a Trik-L-Start or auxiliary battery charging on the solar controller.

Quote:
Originally Posted by GSGracie
Everything I have read here suggests that the solar should go straight to the batteries, is there any reason to pass it to the house cutoff at the front of the bus? Should I install a switch of some sort between the solar and batteries to enable me to disconnect the solar if required?
Yes, a disconnect switch between the solar controller and batteries is advised.

RV Electrical and Solar

If you can go to Montana you might be able to get Handy Bob to fix and upgrade your system. Handy Bob Solar Blog

If you could perhaps list all your equipment makes and models and any other specific configurations (wire size, fusing, disconnects, etc.) it would help us learn more about the shortcomings of your current system.

Good Luck.
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Old 03-02-2014, 12:19 PM   #6
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Some details in the attached of my installation that may help. YMMV.
Attached Files
File Type: pdf VSheetz - Solar Setup for my RV v1.1.pdf (473.7 KB, 46 views)
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Old 03-03-2014, 01:14 AM   #7
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Thank you all for your prompt replies. Now my problem is, do I take it back to the guys who stuffed it up in the first place, or cut my losses and get someone else to fix it. It seems as though there is enough wrong with the setup that the original guts are not worth persevering with.
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Old 03-03-2014, 10:18 AM   #8
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It seems to me that you are knowledgeable enough to do the work yourself, it's easy really, and doing it yourself provides increased self-sufficiency.

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Old 03-03-2014, 10:39 AM   #9
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Quote:
Originally Posted by GSGracie View Post
Thank you all for your prompt replies. Now my problem is, do I take it back to the guys who stuffed it up in the first place, or cut my losses and get someone else to fix it. It seems as though there is enough wrong with the setup that the original guts are not worth persevering with.
It's worth taking back once, IMHO. As you said, they were learning about RV solar on your coach, give them a chance to learn more and fix it. They should be able to understand and follow the advice given above and rectify the wiring issues.

If they can't/won't fix it then do as Ed said, do it yourself. Start by trying to document exactly what equipment you have and where the wiring goes (photo or scan of something hand-drawn is fine) and posting it, I'm sure you'll get some drawings back with suggestions for changes.

There don't seem to be a lot of places in New Zealand advertizing competency in RV Solar on-line, mostly just places that sell the components.
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Old 03-03-2014, 11:05 AM   #10
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Sorry, I didn't notice New Zealand was OP's location. While Handy Bob might not be an option for a personal fix, careful reading of his blog can be helpful.

The Jack and Danielle Mayer RV Electric site is very good to understand the basics.

Armed with proper knowledge you hopefully can get them to make the appropriate changes.
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Old 03-15-2014, 04:48 PM   #11
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Update!

Load tested the five batteries, two are excellent, two are very good and one is not good. I have disconnected the positive terminal of the bad battery so it no longer affects my bank, and I have ordered five new 100AH 12V batteries to replace the whole set. Should be able to sell on the four good batteries for a reasonable loss to help offset the cost. Hopefully this will make a big difference to the amount of storage I can actually keep and use.

My "consultant" thinks my MPV controller and charger built in to the inverter are probably set up wrong, so he will check and reset these once the good batteries are installed.

The inverter is wired up so that ALL shore power passes through the inverter and then to the plugs; not ideal, but I can live with that rather than going through an extensive rewire.

The wires from the panels to the MPV controllers are barely adequate, but at least the controllers are wired direct to the batteries, as they should be. If the other changes don't give me adequate off grid recovery, I will replace those wires as my next step.

Looking forward to running off grid, and being able to park anywhere!

Thanks for your help, as always it is appreciated.
Cheers
Graham
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