View Single Post
  Spotlight this post!  
Unread 08-05-2013, 12:04
EricVanWyk EricVanWyk is offline
Registered User
no team
 
Join Date: Jan 2007
Rookie Year: 2000
Location: Boston
Posts: 1,597
EricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond reputeEricVanWyk has a reputation beyond repute
Send a message via AIM to EricVanWyk
Re: Connecting battery & charger to PD board

I spoke with a friend of mine that used to design battery chargers about this. We looked at three lead acid charger types:

1) Giant Transformer and a Rectifier
Exactly what it sounds like. The voltage is set by the turns ratio of the transformer. The current limit is set by the magnetic paths in the transformer. Good enough for charging a battery, but I wouldn't want to rely on the precision of any specs.

2) Buck Regulator, CC-CV
This looks really similar to the power supplies on the PD, but they accept a much higher input voltage (rectified wall power). It is the gross topology of the 5V regulator, and the over-current strategy of the 24V regulator.

CC -> Constant Current. If the voltage difference between the battery's current state and its desired state is high enough, the buck regulator reduces its output voltage until a given current is produced.
CV -> Constant Voltage. Once the battery is high enough, the current is reduced until a given voltage is produced.

This type is fine to use with a PD as long as a battery is also attached.

3) Buck Regulator, High Frequency Injection
Just like #2, but with additional circuitry that attempts to rejuvenate the battery by hitting it with a high frequency component. This is great for batteries, not so great for the power supplies on the PD.

Do not use this type while attached to the PD.