Zivan NG3 Charger

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geekygrilli
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Zivan NG3 Charger

Postby geekygrilli » Wed Aug 15, 2007 8:49 pm

Hi

I hooked my shiny new Zivan NG3 charger tonight, and charged for about 1/2 hour - all seems in perfect order.
I've got to go home now so I won't be leaving it on charge overnight - just in case. I'll charge tomorrow during the day, so I can keep an eye on proceedings.

I do have a question, though...

I can set the charge rate (I am running 110Ah Wet Lead Acid batteries) and I have a choice of 125Ah or 105Ah setting - which should I use?

I have set it to 105Ah, seems safest.

In my r/c model car racing days we used to peak our cells at various currents. The higher the current the more 'punch' you had, but used to dump earlier. Lower current gave less punch, but a longer run time. This was with NiCds and then later NiMH cells.

Does the same hold true for Lead Acid batteries?

As I understand it I can't tell the charger what current to charge at - it does its itself based on what capacity i say the batteries are. I am worried that if I say they are 105Ah, it will only put that much 'capacity' in, and I'll be short of a few %!
If i tell it they are 125Ah it will over charge...

Help...?

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EVguru
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Postby EVguru » Wed Aug 15, 2007 9:42 pm

I don't recognise the Ah sizes, but Zivan chargers used to have a low capacity or high capacity setting. The current was the same on both, but the alarm timer periods were different.

On the NG3 in my Scirocco, the alarm limits were six hours in bulk (constant current) and twelve hours in absorbtion (constant voltage). This was in fact WAY too long and I always ran an external timer.

I've usually found improved performance from lead acids when charged at higher currents. The internal resistance is lower, the cell balance is better, and from some laboratory papers the life expectancy may also be better. Hawker (Enersys) specify a MINIMUM charge current for good life.

Your NG3 will be rated at something like 22 amp and that should be fine.

The charge profile should be in the back of the manual.
Paul

http://www.compton.vispa.com/scirocco/
http://www.morini-mania.co.uk
http://www.compton.vispa.com/the_named

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geekygrilli
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Postby geekygrilli » Thu Aug 16, 2007 8:43 am

The charge profile sheet is all in Italian!

There are 10 different battery Ah settings, and from what I remember of my Italian and can work out, changing the battery Ah setting only adjusts the Max time at each point of charge, not the current.

Therefore, 105Ah setting just charges for a shorter period than the 125Ah setting.

The charger works in three phases, T1 is the high rate, T2 is the drop off slope, and T3 is trickle charge.

Think I've got it now. If I set the charger to a hight Ah rating, it will potentially charge for longer, which is a bad thing.

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Postby EVguru » Thu Aug 16, 2007 9:58 am

The charge time should be set by the DOD of the battery.

You have two main phases;

1. Bulk or constant current phase.
2. Absorbtion, Gassing, or constant voltage phase (current taper).

The first phase lasts until the voltage reaches the threshold for the second phase, or exceeds the timer limit. If you exceed the timer limit there is something wrong.

It could be because you were discharging the battery during charge, or it might be due to a failed cell or indeed several. The most common cause would be that the batteries are too hot. Ideally you have a temperature sensor and compensate the voltage threshold accordingly (around -10mv per 12v battery per degree C). Voltage above that level mostly causes heating rather than charging and you're driving the battery into 'thermal run-away'. Even if you've get the sensor, you have to identify the hottest battery and it might not always be the same one.

Problems often happen on a hot day when you've been driving hard and the batteries are nice and toasty.

This is where an external timer is useful. Ideally you would wait until the batteries have cooled down, but you might want to use the vehicle again. You set the timer (from experience) for a time that would only complete the bulk phase at most. Even if you verge on a thermal run-away, it will be limited by the external timer and the batteries do perform better when hot (they age faster though).

The second phase ends when the current drops below the programmed threshold, generally 2% of capacity for a flooded lead acid, or exceeds the second alarm timer. Again the current may fail to drop low enough. This might be due to temperature again, or simply as the batteries age.

The built in alarm timers are based on recharging an 80% discharged battery, so if you've only driven a short distance will be way too long to protect against any problems.

I'd set the charger capacity on the high side and use an external timer. A runback type would be ideal. You'll soon learn how long to set it for.
Paul

http://www.compton.vispa.com/scirocco/
http://www.morini-mania.co.uk
http://www.compton.vispa.com/the_named

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geekygrilli
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Postby geekygrilli » Thu Aug 16, 2007 11:03 am

Thanks Paul

Charger is on 2nd phase now (gassing).

Max time for first stage (at 105Ah setting) is 5:30 hrs, but mine moved onto second phase at 2:30hrs or less, can't be sure, been checking every 20 minutes.

Third phase seems to be trickle charger.

Electrofit Zapi are going to send me English instructions!

I think its all good! :D

I'll try to let the batteries cool down when in constant use, and sort out a timer. When charging over night for the next day's drive it will be good to have them finish charging at 630am; electricity iis cheaper off peak too.

Thanks again for your help.

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EVguru
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Postby EVguru » Thu Aug 16, 2007 12:36 pm

Paul

http://www.compton.vispa.com/scirocco/
http://www.morini-mania.co.uk
http://www.compton.vispa.com/the_named


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