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Post Info TOPIC: ADDING A SECOND BATTERY AND VOLTS DROPPED??


Senior Member

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ADDING A SECOND BATTERY AND VOLTS DROPPED??


Hi again. Well we have hit the road for our big lap and after sorting out the problem with our fridge, due to Cyclone Debbie, did not get a chance to trial our free camp capability. When we only had one 120ah battery in our van we would get to 14.3v on our meter, and yes I know that you shouldn't add a new battery with an older one (18mths old) but thought we would try it. After adding the 2nd one the volts have gone down to only giving 12.7 on the meter. We have been on power at a caravan park since adding the battery so have not had a chance of trying the free camp thing again. My question of course is: should the volts be up in the 14s or is it normal for it to show lower with the two?

Kim

 



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Chief one feather

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Hi Kim, you should have 14+ at full charging, once charged it wil drop down so the two batteries could be fully charged. My thought would be the 240v has taken over and solar has shut off as is normal. Have you tried disconnecting the 240v and see how things go from there?

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Hi gandksmile

Some problem for sure ! Re-check your fitting NOW ! Consult someone about it as it should just work like it did before but last longer and take longer to charge up again.

When you are satisfied it is all correct then just stay at the caravan park but disconnect the power and see what happens. Just monitor the voltage as it is used up and if you have a problem just switch the power back on and fix the battery system. biggrin

Jaahn



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Senior Member

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It is not only under the cover of full shade but it is pouring rain at present so no solar. But shall try later. Thank you.

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Guru

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Make sure wiring to second is thick enuff.
Specially if a longish run.

Silly question. But are they BOTH AGM or BOTH Wet cells???.



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Guru

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Mine hardly gets over 13.7V AGM batteries

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Whats out there


Guru

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You did not tell us what the batteries are or what you are charging them with thus we don't have much of a clue what could go wrong. You also did not tell us what you are running from the batteries. You could try charging each battery separately and see what happened.

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PeterD
Nissan Navara D23 diesel auto, Spaceland pop-top
Retired radio and electronics technician.
NSW Central Coast.

 



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IMG_0226.JPGIs there a choke in wire size ? The dreaded VD ?



-- Edited by Aus-Kiwi on Monday 29th of May 2017 11:12:36 PM

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Guru

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Perhaps the process of elimination may solve the problem.

You know what the voltage was with the original single battery.

Try the later battery as a single in the system and check voltage. If same as previous battery then all ok.

Move on to next step of suitable cable size, connections & wiring generally.

A voltage float reading of around 13.5 is the objective.



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Aus-Kiwi wrote:

IMG_0226.JPGIs there a choke in wire size ? The dreaded VD ?



-- Edited by Aus-Kiwi on Monday 29th of May 2017 11:12:36 PM


 Aus Kiwi hi

That photo remined me of time I had stopped for dinner up the track when I came out all fired up to make the big mile, hit the key in the old KW not nearly enough to turn it over, had a light pair of jumper leads and I hooked up to a nearby farmer's tractor, still not quiet enough juice running though the leads by this time I had a small amount of people watching, this older guy (Myself was youngish a bit green) stepped down from his truck gradded the 2 leads put them on the positive and then reached over to my trailer, pull out one of my cross bars, wedged that between my truck and the tractor, he said "give that a go youngan ". That my friend was a real usefull lesson in electrics, used it a lot over the years with my now 50 year old light home made jumper leads from discarded junk.



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Guru

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Yep . In desperate times we have used a welder to start old diesels Fordson Mager tractor etc. But it has to done carefully only applying the welder while cranking . We have also run Bull bars together as you had done and doubled up on jumper leads on + positive side !! Even used 24v on half dead batteries just to have enough grunt to turn motor fast enough to start !! NO WAY would I do that to a modern vehicle with delicate, expensive ECU etc !!

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Whats out there


Senior Member

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The only time we get a battery meter reading above 14V is when the batteries have got down to around 12V before charging. When the batteries are fully charged the meter reading is a shade over 13V, which I have been told is 100% charged for AGM batteries. I dont want to see 14V on the gauge .

Maybe this might have been better on Tech Forum.


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Guru

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Barry, a little education for you. When a battery charger is first switched on it will go through a full cycle. It will first go into the bulk stage or in other words charging full chat. It will do that until the voltage rises to the set voltage of the absorption stage and the voltage will cease to rise whilst the charger is in that absorption mode. When the charge current reduces to the switch over point where the charger considers the battery is nearly fully charged the charger will switch over to the float stage. If the battery is fully charged and you are not watching the volt meter the charger could go through that cycle before you observe the meter it can go through the cycle in a few seconds. The set voltage of the absorption stage should be something over 14 V, the actual voltage depends upon the battery chemistry. The float voltage depends on the battery chemistry and should be between 13.3 and 13.8 V. An AGM float voltage should be between 13.6 and 13.8 V.

When the batteries are fully charged the meter reading is a shade over 13V, which I have been told is 100% charged for AGM batteries.

A voltage over 13V is fairly meaningless unless you know what is happening. The only meaningful voltage of a battery is the rested voltage. The rested voltage is when there has been no charge or discharge of a battery for more than a few hours. The rested voltage of a fully charged AGM battery should be around around 12.8 V, again depending the actual chemistry the manufacturer used in the battery.

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PeterD
Nissan Navara D23 diesel auto, Spaceland pop-top
Retired radio and electronics technician.
NSW Central Coast.

 

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