On Thu, Mar 13, 2008 at 9:07 AM, Travis Gintz <[EMAIL PROTECTED]> wrote:
> so, here's a Q, how is he going to take the pack OUT of series, and > put it into parallel for charging? > > Wouldn't that require a contactor for each battery to take it out of > series, and some relays to connect to the 12V charger bus? > > Or is his system going to be 12V.... > The diagram is attached. Please note that the 12 fuses in the diagram should be rated for the full pack voltage. On Thu, Mar 13, 2008 at 8:54 AM, Johnathan Vail <[EMAIL PROTECTED]> wrote: > You are right they will balance each other out and charge to the same > level but that isn't really what you want. You want the best charge for > the individual cell. Any time you have multiple cells charged together > the stronger ones will beat up on the weaker ones. > In extreme cases with high amp charges one cell will reach max charge > before the other one and the extra current could cause over heating of the > electrolyte > Maybe in a series string, but maybe not in a parallel configuration. It is voltage that forces overcharge, and in a parallel configuration of cells, the voltage would remain constant for each of them. On Thu, Mar 13, 2008 at 8:32 AM David Herron <[EMAIL PROTECTED]> wrote: > One issue I haven't seen Andrew address is ... if you connect in > parallel two batteries who aren't at the same voltage.. clearly they're > going to try and equalize when you connect them, so there should be a > large spark. The voltage should be close, and I would not expect much current to flow. Connecting a fully charged battery in parallel with a discharged battery doesn't cause an alarming amount of current to flow with a big spark. We do it when we leave car lights on, and need a jump start. A potential problem I can see is if one battery has a shorted cell than it may draw a lot of current from the others. This appears to be like connecting a 5 cell battery in parallel with a 6 cell battery. I imagine this is a good reason for the fuses in the diagram. On Thu, Mar 13, 2008 at 7:53 AM Jeffrey Blamey <[EMAIL PROTECTED]> wrote: > If you do the one charger how will you properly charge all the > batteries to the same level... You are clearly making it harder on > yourself to have to break the series connections between the > batteries. > At a CV of 14.7v, and a current of <.01CA, a battery is fully charged. If I wait until the current is .01CA of any one of n number of batteries in parallel at 14.7v, than that ensures that all of them will be fully charged before the charger cuts off. Holding the voltage at 14.7v for a 6-cell battery ensures that it will not be overcharged at room temperature. The intention is really the same as bank charging. I don't want or care to charge all of the batteries to the same level, I just need to charge every cell within the battery to 100%, and prevent cell damage due to overcharging. I think I'm making it much easier on myself. I'll have one simple charger with 1/6 the chance of failure of any one of 6 chargers failing. Andrew in NM
<<attachment: Parallel_charging_drawing.gif>>
