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[KW]

An intelligent charger will not reliably fully charge 2 batteries connected in parralel

I'm quite willing to listen  ........ what's the difference between two in a parallel & one bigger capacity battery, as far as charging them is concerned?

Other than charging time & current, nothing.

You can have as many batteries as you like in parallel, providing the total Ah capacity doesn't exceed 75Ah (according to the specs of the Ctek charger).

When connecting batteries in parallel, the voltage will stay the same but the current capacity will be the sum of all the batteries combined.
When connecting batteries in series, the voltage will be the sum of the batteries and the current will remain constant at 55Ah.

The above figure is based on the 065 battery quoted by Skruntie.

[Andy B]

....
You can have as many batteries as you like in parallel, providing the total Ah capacity doesn't exceed 75Ah (according to the specs of the Ctek charger).
 ....

or 120 for maintenance

[Mr Skrunts]

Ok, to clarify, I have 2 cars, 2 x dead flat batteries. plus the 2 old betteries that came off.

Idea is to fully cherge all 4 battries if in decent condition to thier fully charged state.

There well only be 2 decent batteris of the four, as the 2 weaker batteries were given to my mate for trying to starting dud RC 2 stroke helicopters hoping they would at least hold enough charge for that job with the 12v power starter unit.   

The best of the 2 newer btteies was to go back on my Elite and possibly fit the monitor/charge adapter some where on the dash for the odd boost if the car needed it.

The GLS currently SORN I was thinking that a tralier plug could be adapted, hoping that the 2nd socket has a parmanant 12v (+) on it and cound just be plugged in for a boost every few weeks.

Then to keep the life of the 2 old but spare batteries going after fully charged the idea was to hook them up in parallel and ckip the CTak charger to them.


Simples really ...... or is it.   

[KW]

....
You can have as many batteries as you like in parallel, providing the total Ah capacity doesn't exceed 75Ah (according to the specs of the Ctek charger).
 ....

or 120 for maintenance

Correct, but "maintenance" charging is not actually charging.

[Andy B]

....
You can have as many batteries as you like in parallel, providing the total Ah capacity doesn't exceed 75Ah (according to the specs of the Ctek charger).
 ....

or 120 for maintenance

Correct, but "maintenance" charging is not actually charging.

but it's what Skruntie wants the charger to do.

[Kevin Wood]

Then to keep the life of the 2 old but spare batteries going after fully charged the idea was to hook them up in parallel and ckip the CTak charger to them.

As you have the choice, probably better to connect them one at a time. That way, if one of the batteries is sulphated, for example, and needs conditioning, the charger will detect this and do the necessary. If it's in parallel with a battery in better condition, it won't be detected.

Connecting the batteries one at a time won't mean they take any longer to charge, assuming they'll absorb the full output of the charger for most of the charge cycle, but it will mean that any conditioning and recovery features in the charger work better.

Kevin

[Marks DTM Calib]

The intelligent chargers work on a time, voltage and current principle.

The initial de-sulphation stage is time basd....this will work.

The second stage is a constant current charge setup....no huge problems here.

The third stage is a constant voltage charge.....nothing to worrying here either.

The worst bit is the final long term float charge. Here the micro continualy monitors the battery voltage and applies maintaining pulses as required......this is where i goes wrong.

The reason is that no 2 batteries are the same and as a result one will self discharge quicker than the other.....the result is that one of the batteries quite simply gets over charged over time as the charger meets the needs of the lesser item.

We found this out the hard way a year or two ago using parralel batteries in an edge router style product.....in the event of a power failure we were getting just over half of the expected holdup time......and the reason was that one of he batteries had been very slowly boiled off.

[Andy B]

......

The reason is that no 2 batteries are the same and as a result one will self discharge quicker than the other.....the result is that one of the batteries quite simply gets over charged over time as the charger meets the needs of the lesser item. ......

       Simple really! 

[Mr Skrunts]

Excellent stuff, cheers everyone for your input.

Been out to the car today, door opened with the key which was an unexpexted surprize, My mate was here as I know it would take 2 to open the bonnet, usual stretched cable problem which has now had some WD40 on the catcth/cable etc ready for when we get round to adjusting it next week.

Car hadnt been started since christmas, bless it's little heart it fired the first turn of the key with one of those jump/booster pack things.

Reset the windows and radio tuned it and checked all the windows etc.  Sunroof was a bit iffy at first the I tried pushing the control knob in and turned all was fine there.

Only niggles were a locking solenoid working both directions on its own at power up before starting.  Power hooked up, alarm went off, pressed the alarm fob to open doors and solenoid started making open/shut noise.  Turned ignition on/off a couple of times it seemed fine.

Fronts pads were slightly stuck on, no issues there.

Car had advisories for corrosion on inner O/S front disk, thre wear and a front bush (I think)  Car was parked up at christmas as the corrosion had taken one of the pads metal to metal ( my fault as all plans went tits up due to illness)

So now I dunno whether to just stick a set of pads in and make sure there is nothing else wrong with the car on a run.  Or put the new pads and disk on now and get the bush or wishbones (cant quite remember the exact problems on the advisory)

Then either get new bushes/wishbones fitted and gett tracking done locally, Or get all the joints soaked and make a trip to wim and let Tony fit new suspention as requied and set the car up.  (If I do that will be later in the year)

But basically chuffed to bits with the car.

[Mr Skrunts]

Handy little idea, not sure if its any good though.

http://cgi.ebay.co.uk/Battery-Disconnect-Switch-Isolator-Cut-Off-Switch_W0QQitemZ230458803540QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item35a86a4554

[Mr Skrunts]

Well I must admit, for a tiny little unit I am well impressed.

Put it on to charge the day it arrived, took it off after 3 hours, then did 2 x 7/8 hour charge sessions the next  days.

Didnt start the car on any occasion as I wanted a full charge in the battery, didnt touch the car yesterday as it was pi55ing it down.

Gone to the car today, all spot on, fired on 1st turn of the key, so well inpressed with the little unit.

Just need to suss out the best way to add a permant route for the wirning now to leave a charging connection permanantly wired.   

[Andy B]

Handy little idea, not sure if its any good though.

http://cgi.ebay.co.uk/Battery-Disconnect-Switch-Isolator-Cut-Off-Switch_W0QQitemZ230458803540QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item35a86a4554

but this kind of thing will allow you to retain your alarm & radio stations etc   

[Kevin Wood]

but this kind of thing will allow you to retain your alarm & radio stations etc   

Won't stop the battery draining though.

Kevin

[Drewomega]

Handy little idea, not sure if its any good though.

http://cgi.ebay.co.uk/Battery-Disconnect-Switch-Isolator-Cut-Off-Switch_W0QQitemZ230458803540QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item35a86a4554

I use one of these when I leave here for months at a time. There is a fused link on it which will allow the alarm etc to be armed if required. 

[Marks DTM Calib]

But again, wont stop the battery draing, it will only stop somebody starting it.

We use these at the heritage centre for some of the plant....they work very well