When you put batteries in parallel they automatically balance each other
... and they will automatically all be charged to the same level by the
charger.
If you bank charge with one charger per battery how do you have any
gaurantee the chargers actually all behave the same way? Chargers are
analog devices and some of the components could be different from
charger to charger.
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.
- David
Jeffrey Blamey wrote:
If you do the one charger how will you properly charge all the
batteries to the same level. It seems from watching this list for year
that the best approaches are a.) one charger for the series string and
utilize a BMS to ensure all the batteries are at the same level of
charge, or b.) individual chargers and no BMS - I am charging 6A per
battery at the same time and each charger goes into the final stage
when the time is approriate. You are clearly making it harder on
yourself to have to break the series connections between the
batteries.
Time for the series charge/BMS guys to chime in here.
Jeff
On Wed, Mar 12, 2008 at 9:50 PM, Andrew Wowk <[EMAIL PROTECTED]> wrote:
In concept, I have to disagree. It is simpler, cheaper, and less bulky. I
think in abstract terms, all we are really trying to do is break the battery
pack which is really just one large battery by definition, into 6-cell
sections for charging. I don't see why one large 12v charger wouldn't work
well, if not better due to being simpler and easier controlled.
However, there are some advantages to having individual chargers:
⚫ The maximum current should always be within a predefined limit. It may not
be with the batteries in parallel & one large charger, due to variations in
the batteries, battery temperature, and the variation in wire lengths
connecting them.
⚫ If the chargers check for battery problems and give some feedback, they
may not be able to do this properly w/batteries in parallel.
⚫ In the case of a battery w/shorted cell, the other batteries will be
charged properly. This may not be the case with batteries charging in
parallel.
Andrew in NM
On Wed, Mar 12, 2008 at 8:29 PM, Jeffrey Blamey <[EMAIL PROTECTED]>
wrote:
Sorry as far as the chargers go you can leave the normal series
connections in place, and wire each charger to each battery. 6
chargers at 6 amps each running their own charging algorith based on
each battery state of charge is preferable to one large charger trying
to charge 6 batteries in parallel.
Just imagine the series string is open, when it is charging it better
be. I have left the chargers in the circuit when the bike was turned
on but the chargers disconnected from their ac source. No appraent
problems with the Electricross chargers.
Jeff
