12 volt Power setup

Submitted: Tuesday, Jan 25, 2011 at 12:48
ThreadID: 83884 Views:2948 Replies:3 FollowUps:7
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I want to set my 12volt Auxillary power up the best way possible based on my needs.

I have two Aux batteries one is charged directly from the alternator isolated via a redarc. The other is charged from the alternator useing a CTEK DC>DC battery charger. Both are separated IE: Are not in paralel. I want to introduced solar charging to these but not sure on the best way to set this up.

I,d be interested in any comments on best way to setup this up. Ive been told best is too set these batteries up in pararal as follows.
Alternator > CTEK > Battery 1 > Battery 2 then run a cable from battery 2 to solar panel regulator. Thias apparanntly then ensures both batteries simultaneously received charge from solar

Ive tried to locate a good Auto electrican in Sydney whom also understands solar for advice in setting up and installation to no avail so I may as well install it myself. Problem is as mentioned I do not know the best way to set this up.

Appreciate any comments

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Reply By: Robin Miller - Tuesday, Jan 25, 2011 at 13:21

Tuesday, Jan 25, 2011 at 13:21
Hi Noel

I always design everything for max survivability but I am not sure if this is your goal.

Hence I never parallel up the systems, and following this logic I would simply wire the solar panels direct to each battery via its own low cost regulator, this means that a stuffed on one side will not flatten the other battery.

Robin Miller

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AnswerID: 442987

Reply By: Mandrake's Solar Power- Tuesday, Jan 25, 2011 at 14:08

Tuesday, Jan 25, 2011 at 14:08
As you are already setup - as Robin said above - One Solar Panel input and 2 Solar Regs - one attached to each battery ..

Dead simple and dead easy to install - 5 Anderson plugs and a few screws and its done ...


AnswerID: 442994

Follow Up By: Member - Noel C (NSW) - Tuesday, Jan 25, 2011 at 14:31

Tuesday, Jan 25, 2011 at 14:31
OK Thanks I understand the two solar regs one for each battery meaning only one battery can be solar charged at a time but I,m confused with 5 anderson plugs? I would have though only two?
FollowupID: 715052

Follow Up By: Mandrake's Solar Power- Tuesday, Jan 25, 2011 at 14:42

Tuesday, Jan 25, 2011 at 14:42
One attached to each battery ..
One attached to the Solar Panel cable
Then a V shaped connection cable to join the main cable to both regs at the same time ...

So thats 6 sorry !!

Oops ..

FollowupID: 715054

Follow Up By: Member - Noel C (NSW) - Tuesday, Jan 25, 2011 at 15:22

Tuesday, Jan 25, 2011 at 15:22
lolol Ok I,m still cunfused lolol its not hard to do with sort of stuff lol

I understand the Anderson plug on the panel but the plugs to each battery? Wouldnt the batteries be hard wired to their respective regulators.

Can you help maybe with a rough back of envelope diagram?
FollowupID: 715059

Follow Up By: Mandrake's Solar Power- Tuesday, Jan 25, 2011 at 15:35

Tuesday, Jan 25, 2011 at 15:35
Email sent with diagram ..


FollowupID: 715060

Reply By: _gmd_pps - Tuesday, Jan 25, 2011 at 15:44

Tuesday, Jan 25, 2011 at 15:44
As I understand you are after an "elegant solution" not necessarily the "best" , otherwise you would not do what you do at this stage.

A nice solution for your question is the Sunsaver Duo with remote meter. I came across this when I did some research about bringing in a few more solar panels and batteries from the US. You get that controller for $150 in USA, but it is only "low current (25amp)" and not MPPT, but it should suffice for your application.

Using two controllers on a y-connector from a solar panel to charge two batteries is very inefficient but may work for some low current, low demand installations.

good luck
AnswerID: 443003

Follow Up By: ChrisK - Tuesday, Jan 25, 2011 at 16:06

Tuesday, Jan 25, 2011 at 16:06
Noel, I have to agree with gmd about the sunsaver duo solar controller. I had one fitted to my van a year or so ago and it charges both sets of batteries from the panels without a hitch. It's also dead easy to use & understand, only a few optios, 1 - shows how much charge is going into the batteries from 240, 2 - shows the temp of the panels, 3 - shows solar input to battery bank 1 and 4 - shows solar input into battery bank 2.
Mine was installed in Melbourne by Glen from "Power to be free". I have no affiliation with him but he did a great job and came to my home to do the install which was completed as quoted in a couple of hours.
FollowupID: 715062

Follow Up By: Member - Noel C (NSW) - Tuesday, Jan 25, 2011 at 16:57

Tuesday, Jan 25, 2011 at 16:57
Your comments intrigue me "elegant solution" not necessarily the "best"?

What would you consider as the best solution?
FollowupID: 715065

Follow Up By: _gmd_pps - Wednesday, Jan 26, 2011 at 02:47

Wednesday, Jan 26, 2011 at 02:47
hmmmm... to answer that I surely would need more text than I can fit in a reply here ...
I can give you a few arguments what my "Best" solution would not be

1. Charging your batteries from an alternator via a voltage sensing relay
2. Isolating a battery with a diode
3. Charging a battery via a wire of the trailer plug
4. Using batteries which require maintenance (standard wet cells)
5. Charging from solar panels with no or basic/cheap regulator
6. Using insufficient wire thickness
7. Switching batteries in parallel for charging.
8. Not isolating batteries when not in use
9. Not keeping batteries on float when not in use
10. Using components not capable of working in at least 40degrees heat
11. Not temperature compensating during charge
12. Not organise batteries in banks for load management
13. Mixing batteries (age and type) in banks
14. Charging batteries with a fixed voltage charger (see 1)
15. Packing batteries too tight without air flow
16. Not using suitable low discharge disconnects
17. Not using voltage boosters where required

I could go on ...
The "Best" system for me is the one which meets the requirements of the user in the best possible way, within the given parameters of budget, space and weight minimising manual control, being load and charge balanced and avoid as many of above points as possible.

Load balanced means that most if not all of the continuous demand is fulfilled without storage need and only peak demand requires storage.

Charge balanced means that the amperage available for charge is actually absorbed as charge current and not burnt as heat because the battery capacity cannot take it.

A standard wet cell cannot take 40Amps charge current so it does not make sense to have 400W solar panels unless you use the extra energy coming from the panels for something else.

Another criteria for my definition of charge balanced is that I require the lost charge in the batteries at any point in time to be replaced within 6 hours during the day (including solar, wind, vehicle alternator or generator).

The "Best" system gives me continuous use of power (preferably from renewable energy - there are exceptions) without the need for grid connection. It is not a matter of size or amount of power delivered it is a matter of how good my demand is fulfilled. Some have low and some have high demand. My own system is designed for a very high demand.

have fun

FollowupID: 715103

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