T&T: 24v charger

[Peter Bennett]

Actually, I think the original problem was to charge a 24 volt bank
using 12 volt chargers.

Most 12 volt multi-bank (or multi-output) chargers are designed to
charge multiple 12 volt batteries that share a common negative
connection, so the multiple outputs can't be used to charge two 12 volt
batteries connected in series.

A solution to the original problem would be to use two independent 12
volt chargers, one connected to each 12 volt section of the 24 volt
bank.  From one point of view, this may look like the chargers are
connected in series, but they aren't really, as the common connection
of the chargers is connected to the midpoint of the battery bank,
allowing the chargers to act independently.

Connecting two 12 volt chargers in series across a 24 volt battery,
without the mid-point connection, probably wouldn't work correctly.

Sunday, May 3, 2009, 11:46:44 AM, 2elnav wrote:

2nc> Post script.
2nc> Dave is  correct in  pointing out  the potential issue of some types of
2nc> charger.
2nc> the original disuciison  dalt with  multi bank chargers which have to have
2nc> isolation  in order to work with mor than one  battery.

2nc> Others have pointed out the fallacy of using automotive chargers which do
2nc> not have
2nc> internal isolation diodes.

2nc> It just goes to show, never take anything for granted; nor assume  that
2nc> everybody is on the same page.  :-((

2nc> We have often bitched about the exorbitant price of  'marine'  products  but
2nc> here is a case where marine grade does in fact  reflect better quality  for
2nc> more money.

2nc> Quality  chargers intended for permanent  connection to battery banks that
2nc> may see multiple  charging sources such as engine alternator, solar panels
2nc> or  a combiner  will have internal  diodes to prevent a back feed.  Multi
2nc> bank chargers intended to charge two or more batteries will also have diodes
2nc> on each output.
2nc> But dedicated chargers intended to work as stand alone  and connected to a
2nc> single battery  may not.
2nc> TC40+  IOTA and  Newmar  have the required characteristics.

2nc> Arild

2nc> ----- Original Message ----- 
2nc> From: "Dave Legrow" <dlegrow at yahoo.com>
2nc> To: <trawlers-and-trawlering at lists.samurai.com>
2nc> Sent: Sunday, May 03, 2009 11:17 AM
2nc> Subject: T&T: 24v charger


>> >A better way to combine them for charging is to
>>>split the bank in parallel like this...:
>>
>>
>> Ahh, a question of misleading verbage, for they are not actually parallel, 
>> but
>> rather still in series, with a floating 12v reference (unless you are 
>> putting
>> in a relay or swtich between the two batteries).
>>
>> Hopefully, Arild recommended to you a model that has isolated outputs. 
>> Some
>> chargers will go beserk or worse hooked up this way - but as usual - Arild 
>> is
>> correct, if you use the right model charger.
>>
>> Dave

-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca