Thanks Baz,

Do readings vary with deep cycle 12V batteries or are the readings the same?

 

Hi Duh

I think they are close, but not really 100% sure, maybe someone else can with more technical expertise can help.

From my experience a 12 V wet cell is technically "flat" at about 12.3 - 12.2 V ( shouldn't go down to 12 V or battery life is reduced), whilst a deep cycle is technically flat at 50% of its capacity.

I take my caravan batteries (4X100AH deep cycle) to 12V regularly which shows about 40% capacity remaining. We were on the road full time for 3 years and now batteries are just over 5 1/2 years old. One failed at about 2 years but it must have ben a dud.

What application is your battery used for, as modern chargers help to keep batteries fully charged BUT a car alternator for example generally only charges a battery to about 70% of its capacity. So you can see that modern multi stage chargers/solar chargers and regulators are far better than a simple charge from a car alternator.

Hope this helps.

Cheers Baz

Hi
yes ,you can parallel two batteries with heavy cables , but they should be the same type & preferably near the same capacity.

The battery which, the "Experts" tested & said Ok has definitely lost capacity ,from sitting in a discharged condition & is now useless, even though it may charge up to the fully charged voltage
I suspect the experts did not do a load test on it, just a voltage test

The battery that has only reached 12.2 volts has suffered the same fate

Peter

Hi again Duh

My advice is NOT to put your 2 batteries in parallel. The reason is if you flatten one in paralllel YOU THEN FLATTEN BOTH.

No matter how careful you are it's Murphy waiting to strike.  Friends years ago accidentally flattened all caravan batteries and both batteries in 4WD as they inadvertantly connected all to a heavy load , including inverters to solve a problem and in the end forgot about it (beer was cold). It happens when you least expect it.

As you are in Perth someone could give you the name of a good auto elec or go to a specialised 4 WD place and get good advice, plus shop around is good too.

In simple terms you need the ability to charge both batteries and discharge (even flatten) the house battery WITHOUT flatenning your starting battery. This can be done relatively cheaply with simple manual switching systems up to fully auto systems.

Someone will know someone in Perth - maybe a new topic - HELP me find a good auto electrician in Perth.

Cheers Baz

Duh wrote:

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Using say a multi-meter or plug in cigarette type 12V starter/crank battery reader, is the link shown below a good indication of the state of the battery;

http://www.marxrv.com/12volt/voltchart1.gif 

 

Thanks for the link Duh, handy little reference, I have a volt meter attached to my MH batteries and up to this point was wondering exactly what it was telling me, so, correct me if I'm wrong but it seems to me that if the volt meter ever dips to 12v or lower the batteries are in urgent need of some erg's

 

 

 

 

-- Edited by Duh on Thursday 8th of November 2012 06:14:35 PM

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-- Edited by Santa on Sunday 11th of November 2012 08:53:22 AM

Duh wrote:

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Thanks Baz, the campervan doesn't belong to me and I have suggested the auto electrician bit so have to bite my lip now but good advice.

The house battery is not linked to the crank/starting battery so one is not affected by the other.  But he house battery is ancient I think, because it is enclosed in a wooden framed box without disconnecting things I can't read what is on the sides but I would say it needed replacing some time ago.  But the crank battery is new, the owner taking it up with the RAC at present, but not forceful enough IMHO.

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 Hi Bazz

Yes quite correct, if is the 2nd battery is for another use[Auxillary]

The best way then is to have automatic Isolation by a good VSR battery isolator

Traxide, Red arc  etc all good units & simple to install.

 

Peter

oldtrack123 wrote:

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Momentary dips due to heavy loads are ok but sustained use at low voltage should be avoided if you want long battery life

Suggest you consider a low voltage cutout

Peter

 

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 I use a Baintech LVC low voltage cut-out in my rig and can recommend it. It has a 30 second time delay to allow for momentary voltage dips due to heavy loads such as a compressor fridge starting.

Duh wrote:

---

Thanks Baz, the campervan doesn't belong to me and I have suggested the auto electrician bit so have to bite my lip now but good advice.

The house battery is not linked to the crank/starting battery so one is not affected by the other.  But he house battery is ancient I think, because it is enclosed in a wooden framed box without disconnecting things I can't read what is on the sides but I would say it needed replacing some time ago.  But the crank battery is new, the owner taking it up with the RAC at present, but not forceful enough IMHO.

---

 Did you try desulfator for your house battery?

Here is a link to the Ebay where you can get it, with delivery costs included:

http://www.ebay.com.au/sch/i.html?LH_BIN=1&clk_rvr_id=410862555763&_nkw=battery+desulfator&rt=nc&LH_FS=1

This may solve y problem for good, and cheaply. The battery will run as new.

90% of the time, battery gets sulphated, what this causes loss of ability to hold power, even if it will show sometime even great volatege, but only for short time...

Almost every battery can be rescued, if you'll connect to it a battery desulphator while charging, and/or leave it on even permanently - if it only still shows voltage and doesn't have shorted plates. I had problem with battery ones, myself, when I bought second hand car some time ago. Battery was flat, and didn't want to hold power at all. In the winter time, just overnight stay depleted it so bad it hardly could turn the starter motor.

Finally, when I needing to ask for a jump-start, after just short visit at my friends' I went straight to near-by Jayco shop, and bought the desulphator for about 50.00 bucks. I put in on immediately (it has just two crocodile connectors), and... I forgot since them I ever had a problem.

I left it permanently, till I finally sold the car, when (of course) I removed the desulphator, and now use it on my new car. It is just as simple as connecting two crocodile connectors to your battery, and problem is gone... If you just lease the van, you don't have to leave it with the van when you give it back. I use it now for years, and plan to get another one for solar charging my auxiliary battery too. It is an excellent maintenance tool, for affordable price.

-- Edited by Esperian on Thursday 15th of November 2012 12:56:22 PM

I use a Redarc Dual Battery "Smart Start" isolator to connect my van's 12v system to the car battery. This is an example of a VSR that Peter (OT123) is referring to. (VSR = Voltage Sensitive Relay, we techies love acronyms!). The main purpose of these devices is to ensure that the starting battery gets charging priority and that the second battery is not connected to the main battery until the main is first recharged.

I also have installed a Rotronics solid state dual battery isolator (VSR) between the main car battery and the auxiliary battery in the car.