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Voltage Equalizer For Series Connected Batteries

IP.com Disclosure Number: IPCOM000010916D
Publication Date: 2003-Jan-31
Document File: 2 page(s) / 132K

Publishing Venue

The IP.com Prior Art Database

Abstract

There are many problems with both charging and dischargeing typical series connected battery cells. By connecting many relatively low voltage cells in series, it has been possible to raise the voltage of the system so that lighter wiring can be used. However, this also demands that all of the current during both charging and discharging must pass through each of the cells or batteries. If all of the cells were always exactly identical, and all cells were always discharged uniformly, there would be no problem. However, usually one or more cells differ internally because of past history. As an individual cell discharges, that cell raises the overall resistance that the charger sees, preventing the other cells from becoming fully charged, or slowing the rate at which they are charged. If the charging system is capable of raising the overall voltage to compensate for it's failings. Essentially, each battery cell is acting as an integrator. Small changes in capacity of any one cell of the system cause greater and greater changes in how the system behaves. In addition, it has become common practice to create multi-cell systems in which some parts of the system use lower voltage taps, normally draining current from only a few batteries, for particular functions or accessories that do not require the full system voltage. This of course accentuates the problem, because an entire portion of the series battery pack is now weaker that other parts. Battery life is a strong function of charging/discharging history. Some form of regulation greatly enhances system life. Essentially, one would like to charge in parallel and discharge in series.

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