Solar/Inverter and car charge system

Hi there,

I have a question for you guys regarding the charging system I plan to install in my Camper Trailer.

I have organised the gear that will charge my auxillary battery (in the camper) from my vehicle whislt travelling - but I also have a 200 watt 5.5 amp solar panel with regulator and a 3000 watt inverter. My question is how will I wire up the system to include the inverter?

How will the connections look like on the batttery? Will it be ok to leave the inverter connected to the auxillary battery whilst the battery is being charged by the car or the solar panel? It has its own switch, but will it cause undue interference being constantly connected?

Thanks.
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Reply By: for all your solar needs - Mandrake's Solar Power- Monday, Mar 08, 2010 at 09:17

Monday, Mar 08, 2010 at 09:17
SmokeyD ,

Are those figures correct 200 watt 5.5 Amps - If they are then you have a 24 volt solar panel and will need a DC voltage stepdown of some kind to get to 12 volt output .

Having everything connected to the Aux battery is fine ( except as above and below )

The only problem I see has been mentioned here many times - driving with a potentially lethal 240 volt live system in your vehicle is not the best idea - The Inverter should be disconnected while driving for everyone's safety ..

Cheers

Steve
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Follow Up By: Member - John and Val - Monday, Mar 08, 2010 at 09:33

Monday, Mar 08, 2010 at 09:33
Steve's right on both counts.

I wouldn't rely on any switch to ensure the inverter doesn't decide to kick in and deliver 240V unexpectedly. The safety issue has been discussed frequently here, and in a metal vehicle is a serious consideration.

Also, as Steve says, it sounds as if you have a 24V panel/s. This will be ok to charge 12V batteries, but it will be important that you have a suitable MPPT controller to get reasonable efficiency. Steve can't publicise his solar shop here, but it's worth a visit at this address. There you'll find attractively priced gear, including controllers.

Cheers

John
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Reply By: Member - John and Val - Monday, Mar 08, 2010 at 09:20

Monday, Mar 08, 2010 at 09:20
Depends on the inverter. Personally I would leave the inverter disconnected from the battery except when it is being used. If it is a 3000W one, the 12V side is almost certainly not being switched, in which case the inverter will always draw at least a small amount of current from the battery when idle.

Another concern - That's a big inverter. If you are ever likely to use more than a little of it's capacity, you'll need a lot of 12V power and big batteries.

Cheers

John
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Follow Up By: Nomadic Navara - Monday, Mar 08, 2010 at 09:47

Monday, Mar 08, 2010 at 09:47
Yes, why the hell do you want such a large inverter. An inverter of that size will require a fair bit of power to drive it when you are only drawing small loads. Why do you need an inverter at all.

An inverter of that size will require a 300 A switch if you want to switch it off when it is not being used. This to me is a rather large and unnecessary installation. The supply cable will have to be much larger than starter cable if you are not mounting the inverter right at the battery.

There seems to be a fetish for newcomers to include inverters in their 12 V systems. To me, these are a waste of good battery power. I prefer to purchase small electrical items that are capable of operating directly from 12 V - this saves a lot of power by not transforming your battery power to 240 V and then back to low voltages. If you go to Jaycar or DSE you can purchase 12 V driven power supplies to run your computer and charge batteries in your appliances for less than the price of a good inverter.

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Reply By: Battery Value Pty Ltd - Monday, Mar 08, 2010 at 09:31

Monday, Mar 08, 2010 at 09:31
SmokeyD,

you can leave the inverter connectd to the aux battery whilst being charged, it won't harm the inverter.

But depending on your solar regulator, the battery could get harmed.

If the solar regulator is multistage, i.e. it outputs a higher boost voltage, and a lower float voltage, then any inverter load current could delay or prevent the switch over point from the high to the low charging voltage.
Some better regulators have inbuilt programmable time limits, load/battery current sensor etc. which offer some protection, but it's still advisable to let someone experienced have a closer look at the system to minimize risk of battery damage.

Or, you could just turn off the inverter during the day, while the battery receives charge from the panel, or you could force constant float charging on the regulator (at the lower voltage, and at the expense of longer charging times).
200W@5.5A doesn't add up BTW.

Best regards, Peter
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Follow Up By: SmokeyD - Sunday, Mar 14, 2010 at 14:20

Sunday, Mar 14, 2010 at 14:20
Hi again,

Thought I had this problem licked.

I decided to go the way of the new regulator as I mentioned in my last post - only after that didI decide to put a meter across the solar panels terminals just to make sure of the output volatage. When I did, it read a constant 20.5 volts, not the 36 as mentioned on the back panel. Is this indicative of only half the panel working (diode short) or is "Nomadic Navara" correct in his summation...
"FollowupID: 678169 Submitted: Wednesday, Mar 10, 2010 at 13:29
Nomadic Navara posted:
Ed - I know that, however he is charging a 12 V battery (which is also a little more than 12 V most of the time.) However, a 36 V panel is an unusual size. Smokey said "the regulator the correct one for that voltage and panel." As the regulator does not appear to be an MPPT type things are not adding up. It could well be the correct voltage panel, someone has confused the 36 cells with it being a 36 V peak power point panel and calculated the current out by dividing 200 by 36.

Smokey - you could clear this up by providing the manufacturer and full model number of the panel."

Details listed on the back of the panel are -

(Tong Lin) PMW 200 PW

Watts = 200
Voltage = (VWP) 36.0 volts
current = 5.56 amps

I opened the connection box at the back and the terminals are covered in a foam like substance. I have started to carefully remove the foam (with plastic tool) and have uncovered so far 3 large diodes. The chap from Esolar suggests to remove all wiring from the panel terminal block and measure the short circuit current and open circuit volts. If I get same voltage, then I have 100 watt unit only. It could also be a diode short - in which case he suggests to remove both diodes and check them and then the panel current and voltage again. When I get all the covering off, I'll send a photo of the terminal block.

I am not overly confident with the above, so would appreciate some direction and ideas.

Cheers
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Reply By: Nomadic Navara - Monday, Mar 08, 2010 at 09:55

Monday, Mar 08, 2010 at 09:55
You say you have your solar panel with regulator. As stated earlier, it looks like a 24 V charging panel. Is the controller an MPPT type? If not you will be wasting a lot (50% or more) of your panels potential power output. If the regulator is a simple 12 V model you may be in danger of damaging it with input voltages of over 35 V.

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Reply By: Member - Ed C (QLD) - Monday, Mar 08, 2010 at 10:02

Monday, Mar 08, 2010 at 10:02
As indicated above, 200W @ 5.5A indicates a (nominal) 24V panel...
It will have an open circuit voltage of around 44V, and an operating voltage of 36V....

To connect that panel to a 12V system via anything other than a MPPT controller, you will be losing (wasting) 60% of it's capacity...

Connected via a MPPT controller (which can accept the higher open circuit voltage), that panel will deliver up to 15Amps (@ 13.5V).....

You do have a MPPT controller, don't you??

:)



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Reply By: SmokeyD - Monday, Mar 08, 2010 at 13:08

Monday, Mar 08, 2010 at 13:08
Fellas,

My apologies, I haven't furnished you with all the information.

The inverter is 3000 watts peak and 1500 continuous. The solar panel is 36 volt output with the regulator the correct one for that voltage and panel.

The inverter will reside alongside the battery and only be used infrequently, so the only reason for the question was for convenience sake in where to store it to be out of the way and connected to the battery permanently.
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Follow Up By: olcoolone - Monday, Mar 08, 2010 at 14:53

Monday, Mar 08, 2010 at 14:53
What size battery do you have and what are you running of the inverter?
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Follow Up By: Member - Ed C (QLD) - Monday, Mar 08, 2010 at 15:10

Monday, Mar 08, 2010 at 15:10
What make / model solar regulator do you have ?

:)

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Follow Up By: Nomadic Navara - Wednesday, Mar 10, 2010 at 13:02

Wednesday, Mar 10, 2010 at 13:02
The controller you gave the model number in the next reply does not look like a suitable one for a 36 V panel. A 36 V panel looks an odd size, is it in fact as 36 cell panel. A panel with 36 cells is the correct size for a simple 12 V controller and battery. (Yes I know you said the current OP is 5.5 A, but things are not gelling.)
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Follow Up By: Member - Ed C (QLD) - Wednesday, Mar 10, 2010 at 13:29

Wednesday, Mar 10, 2010 at 13:29
Peter, the operating voltage (36V) is indicative of a (nominal) 24V panel...

;-))

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Follow Up By: Nomadic Navara - Wednesday, Mar 10, 2010 at 13:59

Wednesday, Mar 10, 2010 at 13:59
Ed - I know that, however he is charging a 12 V battery (which is also a little more than 12 V most of the time.) However, a 36 V panel is an unusual size. Smokey said "the regulator the correct one for that voltage and panel." As the regulator does not appear to be an MPPT type things are not adding up. It could well be the correct voltage panel, someone has confused the 36 cells with it being a 36 V peak power point panel and calculated the current out by dividing 200 by 36.

Smokey - you could clear this up by providing the manufacturer and full model number of the panel.
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Reply By: SmokeyD - Wednesday, Mar 10, 2010 at 08:33

Wednesday, Mar 10, 2010 at 08:33
Hi - apologies for the delay, work waits for no man!

To answer your questions - the battery is a 75AH deep cycle AGM battery, and the regulator is an Esolar KS30. Will only be using inverter for phone charging and small apps and not for long periods.

Hope that helps.
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Follow Up By: Maîneÿ . . .- Wednesday, Mar 10, 2010 at 11:04

Wednesday, Mar 10, 2010 at 11:04
SmokeyD, sell the inverter to someone who *needs* it, because you definately don't have a realistic use for it at all.

The larger the inverter capacity, the more power it consumes just to run itself, replace it with a PSW Inverter of about 200 Watts max for small applications and will drain your small capacity DC battery, why not add a 2nd identical battery??
(it's like running a V12 supercharged diesel in a VW beatle - total overkill)

Maîneÿ . . .
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Follow Up By: Member - Mike DID - Wednesday, Mar 10, 2010 at 12:02

Wednesday, Mar 10, 2010 at 12:02
" the battery is a 75AH deep cycle AGM battery"

- if you run a 1500 watt Inverter at full load it'll draw 150 amps from the battery ! Who designed that sysytem for phone charging and small appliances ???
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Follow Up By: Nomadic Navara - Wednesday, Mar 10, 2010 at 12:52

Wednesday, Mar 10, 2010 at 12:52
I've just had a look at the specifications for the E-solar controllers at this link - the price can be found at this link, it is around $200. The price looks too low for an MPPT controller and the specifications also do not mention that it is of that type. I would suggest that your controller is not suitable for the panel. If your controller and inverter are still in pristine condition then then I suggest you seek a refund for them. Purchase an MPPT controller and a 2 - 300 W inverter. An alternate way to go would be to swap the 24 V panel for a 12 V one that is suitable for your controller.

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Follow Up By: Member - Ed C (QLD) - Wednesday, Mar 10, 2010 at 13:20

Wednesday, Mar 10, 2010 at 13:20
Nothing in the published specs to indicate that that regulator is MPPT, which more than likely means that it is not... Which in turn means that it is definitely not the correct regulator to be charging a 12V battery from that panel...
(ergo my previous reply;-))

Have a chat to Mandrake about budget-priced MPPT controllers, or alternatively,
have a look at this one on ebay for what I consider to be the best value-for-money out there atm...

Morningstar MPPT controller on ebay

:)



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Reply By: SmokeyD - Thursday, Mar 11, 2010 at 22:57

Thursday, Mar 11, 2010 at 22:57
Hi there gentlemen,

Well, firstly I must say a huge thankyou to all of you for your input. I have done extensive research based on your advice and come up with a solution. Originally I bought the system from my son who assured me it was all compatible.
First, yes you are right, the PV panel is 24 volt, (200 watt, 5.5 amp), and the Esolar regulator is (according to John @ Esolar) only capable of either 12 or 24 volt charging. Meaning, it will only successfully charge a 12 volt battery from a 12 volt PV panel and likewise the 24 volt - one or the other. The inverter was thrown in with the deal, so we thought we may as well use it. However, after considering everything, we have decided it's not worth including it in our set-up, as rightly pointed out, you can get away with phone charging ion a 12V car systems, and it's far too big for our needs and potentially dangerous. Aslo, I wanted to keep my option to charge my auxilary battery from my car chargining system open (something you can't do if yo have a 24 volt battery bank), and to utilise all the 12 volt lights and switches I had bought.

So now, I have decied to sell the inverter and regulator and have ordered the morningstar item from Ebay (probably the most economic option, thanks Ed C). It proports to be able to convert the 24 volts for my 12 volt system. I have also ordered another 75 Ah battery to link up (parallel) so that I get 150Ah's of usable juice.

At present I have a fridge/freezer (60watt, 5 amp) and some (3) 12 volt, 24 x LED lights that are at present the total sum of my power needs. I realise that the power available may be over kill, but I'm sure it doesn't hurt.

Cheers!
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