Battery charger question (AC ripple voltage)

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Ripple is caused or elimintaded by the filter capacitors to smooth out the have wave rectifications by the diodes.

Some DC rectifiers use very small capacitors (cheap) therfore will have a lot of ripple when loaded up, or one or more of the Filter caps has gone bad which can easily happen.. So if you are experiencing a lot of ripple that was not there before look at the filter caps.

In the case of battery chargers, especially inexpensive auto battery chargers, they usually do not have a lot of filter caps if any at all, because the battery acts as the capacitors. Higher quality ones will have filters.

You get the point, check the caps.
 
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alaskanassassin said:
What is the cause of an AC ripple voltage in a battery charger system and how do you correct it. I was thinking maybe a diode maybe going out? It is an SCI battery charger. Thanks Doug
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Also, an open diode in a full-wave rectifier would create excessive ripple. An oscillogram would identify this problem.
 
alaskanassassin said:
They are lead acid batteries.
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Lead acid batteries generally have quite low impedance so you wouldn't expect to see a lot of ripple voltage across the battery.
Ripple current can be another matter. Fitting a choke (inductance) in series with the DC feed to the battery can significantly reduce this. It also means the harmonic components in the supply are also reduced for conventional SCR chargers.
 
rattus said:
Also, an open diode in a full-wave rectifier would create excessive ripple. An oscillogram would identify this problem.
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Well an opem diode or full wave is same as an open circuit with no current passing through. Batteries would just discharge.If it is a half of the full wave bridge then you have a point, and a scope would easily spot it.

Shorted diode would cause all kinds of ripple and explode batteries if OCPD did not operate.
 
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alaskanassassin said:
What is the cause of an AC ripple voltage in a battery charger system and how do you correct it. I was thinking maybe a diode maybe going out? It is an SCI battery charger. Thanks Doug
Click to expand...

Half wave and full wave rectification by diodes both cause AC ripple due to the nature of sine wave voltage rising and decaying. Battery charging does not much care about this ripple, but supply for sensitive electronic equipment is usually filtered and regulated by other devices or specialty rectifier elements.
 
The ripple voltage is something tied directly to the manufacture/quality of the charger. Like eveything else, there are chargers and there are chargers. If it is a cheapo (usually an unfiltered unit) charger, expect a lot of ripple. If it a good high quality charger (filtered), expect little ripple.

The charger type will depend on what you are using it for, load current, baterry size and other variables. Typically for substation batteries and telecom you have to go for a good filtered unit with low ripple.

If the ripple is an issue for you, I would suggest to upgrade to a better unit, rather than trying to fix it on site with electronics. Some good manufacturers are SENS-USA, La Marche, ALCAD, SBS Battery and Hindle Power.
 
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