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Post Info TOPIC: Two 12v batteries in parallel charged from 2 sources
River rob


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Two 12v batteries in parallel charged from 2 sources
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Hi

Im in the process of installing solar panels on my van. I'm replacing the existing battery with 2 new 100amp batteries.

My question is can I leave all existing wiring and charging to the original battery position and then connect the solar through the solar controller to the second battery and connect them in parallel?

Not sure if this ok to do. What happens if the batteries are being charged from both ends at the same time? 

Or do I need to connect both supplies to one battery?

The reason I ask is I am putting the second battery inside the van, so it is going to be easier to connect the solar to it. The other battery is mounted underneath the van

thanks

Rob



-- Edited by River rob on Tuesday 15th of November 2016 05:15:14 AM



-- Edited by River rob on Tuesday 15th of November 2016 05:26:17 AM

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Jaahn


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Hi Robsmile

The two batteries should be connected together by heavy cables so there is virtually no resistance between them in both + and - connections. Then what you want to do will be OK. It would be best practice to have them close together but that is not always possible.wink

Jaahn 



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River rob


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Thanks Jaahn
The batteries will be about 500mm apart. What size cable do you suggest?
Sorry make that about 800mm.no



-- Edited by River rob on Tuesday 15th of November 2016 09:32:04 AM

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PeterD


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Starter motor size cable. ie 6 or 4 B&S.

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Peter_n_Margaret


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I would suggest about 30mm2.
At 800mm apart, I wold also recommend a fuse at each end of the +ve that links those 2 batteries. A short of any sort in that cable would be catastrophic.

Cheers,
Peter

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OKA196, 4x4 'C' Class, DIY, self contained motorhome. 960W of solar, 400Ah of AGMs, 310L water, 280L fuel. https://www.oka4wd.com/forum/members-vehicles-public/569-oka196-xt-motorhome
 

 
River rob


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Ok thanks guys I'll fit fuses as suggested

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River rob


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Hi Jaahn

i have completed the system and charging from solar panels works fine on its own but when I connect 240 to the c-tek charger the volts go up to 15.5v and the solar regulator cuts out on high voltage. So somehow with both running I can't control the amps.

Is there something I can do to rectify this?

Thanks



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oldtrack123


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River rob wrote:

Hi Jaahn

i have completed the system and charging from solar panels works fine on its own but when I connect 240 to the c-tek charger the volts go up to 15.5v and the solar regulator cuts out on high voltage. So somehow with both running I can't control the amps.

Is there something I can do to rectify this?

Thanks

 

Check the Ctek settings &  ALL connections ,you could have   bad joint

It should not take the battery that high 

First check the voltage directly on the battery terminals

I  very much doubt that  will be 15.5V

work back until you find where the voltage jumps



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Tony Bev


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River rob wrote:

Hi Jaahn

i have completed the system and charging from solar panels works fine on its own but when I connect 240 to the c-tek charger the volts go up to 15.5v and the solar regulator cuts out on high voltage. So somehow with both running I can't control the amps.

Is there something I can do to rectify this?

Thanks

I am not an Electrician

Look at the manual for your model 240 volt CTEK battery charger

Some of them start off in Desulphation Mode, and they can push in, up to 15.8 volts, for as short time

Below is a link to one such 240 volt CTEK battery charger

http://www.ctek.com/Archive/ProductManualPdf/MXS%205.0_EN.pdf

 



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Jaahn


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River rob wrote:

Hi Jaahn

i have completed the system and charging from solar panels works fine on its own but when I connect 240 to the c-tek charger the volts go up to 15.5v and the solar regulator cuts out on high voltage. So somehow with both running I can't control the amps.

Is there something I can do to rectify this?

Thanks

 Hi Rob smile

I am not familar with the C-tec but a suggestion has been made that it might be in desulphate mode. Probably turn that off if you can anyway.  Also check for high resistance connections has been suggested.

Not sure what the other charger is either. But any good chargers mounted together parallel into a battery should have no problem. They each have a maximum voltage and if the other one is higher or equal to that voltage then they do not supply any more. It should not matter whether there is one, two, three or more batteries if there is no resistance between them.

All vans use two chargers or controllers or three, if they have solar and 240V chargers and 12v DC-DC chargers. They should work together OK. 

Jaahn



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River rob


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Hi all
As suggested the ctek charger was in recondition mode . Changed it to normal mode and so far all good ?
Can only blame myself for this one.

Thanks again everyone , much appreciated





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oldtrack123


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Peter_n_Margaret wrote:

I would suggest about 30mm2.
At 800mm apart, I wold also recommend a fuse at each end of the +ve that links those 2 batteries. A short of any sort in that cable would be catastrophic.

Cheers,
Peter

 Ditto 



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River rob


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Thanks old track
Sorry for the delayed reply , been off the air for a while.

I'll fit fuses at each end of + cable as you suggest.



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Aus-Kiwi


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Handy to isolate battery . Funny thing is most car or truck Manu don't have them . They say the cable is heavy enough that it won't burn ., My old Fuso bus has a head bar about 30mm long , 2mm thick 1 20mm wide .. These things are designed to STAY on the road ., Ex JDM bus .. Simple and easy fixed .,

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Aus-Kiwi


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Buzz bar . Bloody auto correct !!

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Whats out there
swamp


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hi

Battery cable under a few meters long would not be an issue ,no fuses .  Well insulate exterior of cable to prevent rub thru .

It is desirable when connecting twin batteries that the pos cable comes from one battery and the neg  comes from the other . Or What can happen is 1 battery is always favoured over the other if wired conventional when being charged and discharged . Potentially shortening the life of the first connected battery .

If using an inverter use the same cable size as the inverter or larger .

If not 35mmsq / 2b&s cable .In parallel the batteries need to function as one unit especially if there is distance between them .

 



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