Dual 12V SLA battery charger

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MTTweaker
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Dual 12V SLA battery charger

Post by MTTweaker »

I am having an issue with the operation, If i use it as a one battery charger, it will work perfectly.
when the code is for dual, once the battery is plugged in the sequence will start and too much blinking starts to happen.
when the battery reaches green LED, green LED and yellow will be blinking...strange things like that

I dont know what i am doing wrong. I figure if the Chip has two CCP ports i should be able out put 2 different PWM at the same time

Any ideas will be appreciated...

I have a code attached. the POT's mimic the battery voltages
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dual rev 1.fcfx
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LeighM
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Re: Dual 12V SLA battery charger

Post by LeighM »

I would suspect that it is a physical issue with the battery charging.
The on charge voltage is going to be higher than the off charge voltage,
so you probably need to measure the voltage off-charge,
or use hysteresis in your decision process.
Also maybe more but smaller PWM step changes.
A Google on battery charging :wink:

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Steve001
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Re: Dual 12V SLA battery charger

Post by Steve001 »

Hi,

how are your batteries connected ?
can you provide a drawing

Why PWM output SLA are charged with constant voltage "Float charging"

Have a Google Yuasa little red book of batteries and charging

https://www.google.co.uk/search?source= ... urlaqDulzc

The open circuit terminal voltage on a battery should not be lower than the battery voltage.

i.e. >24 V on a 24 V DC system.

When charged the batteries will only accept a charge to replace the losses within the battery (approx. 10mA per Ah of battery). If there is a standing load (i.e. control relay or lamps etc.) the charger will output the standing load plus the losses of the battery i.e. If a standing load of 1 Amp is present with 8 Ah sealed lead acid batteries then the charger will supply 1.08 Amps.
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Steve001
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Re: Dual 12V SLA battery charger

Post by Steve001 »

had a look at your program

why are you using 9V for low battery voltage ? - battery manufacturers get "twitchy" when you start to discharge to 1.7 - 1.6 Volts per cell
if on a discharge - peak dips can go lower i.e engine cranking as this is of a short duration. (their are batteries that can "deep discharge" £££ $$$ )
You are on the limits of battery "Discharge Damage"

Lead acid batteries are damaged in terms of capacity and service life if discharged below the recommended cut off voltages.

if a lead acid battery were discharged to zero volts, and left standing in either “on” or “off” load conditions for a long period of time, severe sulphation would occur, raising the internal resistance of the battery to abnormally high levels. In such an extreme case, the battery may no longer accept charge.

also

High ambient temperatures will increase battery Ah capacity but reduce service life of the battery.
Low ambient temperatures will increase service life of the battery but reduce battery Ah capacity.
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