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Pb Charging

Old 12-26-2001, 02:43 AM
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Edgar Perez
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Default Pb Charging

I need to charge my starter battery (1.2ah, 12Volt) and my flight box battery (9ah, 12 Volt). I have a supernova, but Iím unsatisfied with the rate the charger selects. As an example, after 6-7 hours it has only put 390 mah on my starter battery (the battery I believe was almost exhausted)


I have on loan a programmable power supply. I can select volts and amps into it. What should be the setting that will fully charge the Pb batteries without damage?

Thanks,
Edgar

PD: Is there anyway to coax the Supernova to do the recharging faster? Changing the rate manually don't help, since the system seems to select the rate automatically. I was providing 13.8Volts to the supernova.
Old 12-27-2001, 08:26 AM
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Miniair
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Default charging 12V batteries

Are these sealed batteries or can you add water?

If they are sealed about the most you can put into them is 500MA or they will over charge and in most cases the case will bulge form the fumes created and not being able to escape will bulge the case. Also thay have been know to explode - not a very pretty site even if you weren't around at the time - Geled, hot acid all over the place.

Under no circumstances use an automotive type charger to charge sealed batteries.
Old 12-27-2001, 12:41 PM
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Red Scholefield
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Default Force feeding Pb battery

You might try charging it with by setting the SuperNova for Ni-Cd with C=100 ma for the 1.2 Mah cell and for C= 900 ma for the 9 Ah one in your field box. Do not let it go for more than 10 or 12 hours at these settings. Also watch the voltage. It should not go above 14.7 volts. If it does it indicates that the battery may be going bad (sulfated a bit) and should be replaced.
Old 12-27-2001, 02:00 PM
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Edgar Perez
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Default both

Thanks to Red and Miniair ,

The starter is sealed, the flight box one is the type you can add water.

I understand about the sealed one cracking, but if the capacity is 1.2ah, why can't I only put 500mah?

Red, thanks for the settings. I will try them.

Edgar
Old 12-27-2001, 03:18 PM
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Rodney
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Default pb batteries

You should always use a constant voltage source to charge lead-acid batteries. If you have one you can accuratelly set, set it for 13.7 volts and you can leave it on for a very long time with no damage. If you set it at 14.7 volts, only leave it on charge long enough to bring the battery to full charge. When you use a constant voltage charge, the current will be high initially and taper off to near zero as the battery approaches full charge.
Old 12-27-2001, 06:07 PM
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Red Scholefield
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Default Pb Charging

Constant potential is the preffered way to charge lead acid batteries. Unfortunately in the real world these chargers are not always readily available and many sold for use with sealed lead acid batteries are a compromise and end up being neither constant voltage or constant current but somewhere in between. In a good constant voltage charger there is usually some provision for temperature compensation. This is required because the voltage is temperature dependent. This starts to add cost to the charger.

In our application, R/C starter and field box batteries we can work around the problem by using constant current chargers and limit the charge to something between C/10 and C/20. Watch the charge voltage and when it reaches 14.7 turn off the charger. This is for gel cells, flooded cells (motor cycle batteries to which you can add water) use a lower setting, something around 13.8. When you see bubbling its time to stop the charge. Start low and work up on the charge voltage cut off if you want to use a constant current. Working with these you will soon learn what your battery will tolerate.

If you see abnormally high voltage at the beginning of charge this indicates that the battery has become sulfated. Just leave the charger on and see if the voltage will come down. Sometimes you can bring on back in this manner if your charge source has high enough voltage to push a C/12 to C/20 charge rate.
Old 12-27-2001, 11:23 PM
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Hobbsy
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Default PB charging

I use an ACE CVC charger on both types and it does well.
Old 12-28-2001, 12:53 PM
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dant-RCU
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Default pb charging

There is an article on just this subject in the current issue of IMAA's High Flight Magazine. If you can find a copy, check out the article.

BTW, the author recommends just what hobbsy uses - the ACE CVC charger.

DAn

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