EV / Hybrid grid charging voltages

[Daox]

So I'm trying to get my head around how this is working. I just ordered some power supplies that put out 90V each to make an Insight grid charger. They are put in series for 180V max. The car uses a 144V pack. Obviously the voltage goes up and down a fair amount in normal usage.

My question is why do we aim for a 180V output on the charger side? Is it simply a case of they can go to 180V and that is above what the pack will ever charge to, thus they can provide the full current to that voltage?

[rmay635703]

The insight guys told me my 180 volt setup was insufficient to charge the pack.

From what I know, when you trickle charge the nimh the profile can go much higher than expected before all the cells are truly full.

[gone-ot]

It's called "charge voltage," because when the charging-voltage is the same as the battery-voltage, all charging basically stops.

Think of the "charge-voltage" as the voltage difference required (varies with battery composition AND temperature) to "force" electrons into an almost -- but not actually -- charged battery.

With lead-acid batteries the "charge voltage" is about 2.1-2.5Vdc for a 12.6Vdc battery...or 14.7-15.1Vdc output from the charger.

[Ecky]

Although my Insight's battery is "144v", it rests at about 154v on a warm summer day. As the battery charges, its voltage slowly rises, until it peaks (usually around 170v), indicating the battery is roughly full. After unplugging the charger, the battery voltage gradually drops back down to its resting voltage of ~154. These voltages will vary based on temperature, with peak voltage being closer to 180v when it's below freezing outside. To my knowledge, if the charger could not put out more than the battery's peak voltage, it wouldn't be able to fully charge it.

The behavior is a bit different with different battery chemistries, but I'm not very well-read on the topic.

[Stubby79]

Already been said in different words, but...
Nominal voltage vs actual voltage vs charge voltage. Each one is higher then the last.