[TR] Battery trickle charger

[Dave1massey at cs.com]

Actually, saying it is extremely important is a bit of hyperbole, 
especially in a cranking application where the level of discharge is not very deep.  
More important if you will be discharging deeply as in a wheel chair, 
electric vehicle situation or a situation where you are powering accessories when 
the engine is not running.  Since this is an RV the last might be the case.  
(Of course, if that is the case I suggest two 12 volt batteries with an 
isolator so that only one battery is used to power the devices saving the other 
to start the engine regardless.  I also recommend a deep discharge model 
for the battery powering the accessories and a cranking battery for starting.) 
 What IS important is to load the batteries equally.  That means NO! 6V 
loads that draw off only one battery.

I agree that two 12 volt batteries would probably be a better option.  
MGB's were originally equipped with two six volt batteries but many owners have 
converted to two 12 volt batteries in parallel.  Or just one 12 volt 
battery.

Lead acid batteries are pretty robust and tolerate the occasional 
overcharge without too much detriment so a one time charge upon initial installation 
where the two batteries are not charged to an equal state will be fine 
provided one isn't completely dead.

Dave

In a message dated 1/29/2013 5:02:36 AM Central Standard Time, 
aljlthomson at charter.net writes: 
> When using two sixes in series, it's extremely important to have 
> identically
> sized batteries so they charge evenly from the regular vehicle charging
> system. When using a plug in charger, you can use the 6V setting and do 
> each
> one individually or set it to 12V and charge them as a single unit ( which
> is what your alternator is doing anyways). Since every battery is made of
> groups of 2V cells, you are really charging 6 cells in series on a single
> battery, 12V system. When charging the batteries individually, you should
> monitor battery voltage or specific gravity (if you can open the cells) so
> as to balance the degree of charge in each battery.
> 
> I have had better luck with using a pair of 12V batteries in parallel for
> added amperage capability on tractors. In fact, I converted two of my
> row-crop Deeres to this type of a setup from the original factory
> two-sixes-in-series system. They seem to last longer and big 6V batteries
> get pretty expensive. A group 4 6V is about $160 from a Deere dealer while
> group 31 12V (950 CCA) is about 100 bucks from a truck shop. But, that's
> getting away from your question.
> 
> Charging your batteries individually at 6V and using a voltmeter for the
> first time will probably show you if the batteries are balanced. If they
> are, after that you could use the 12V setting and charge them as a single
> unit. I assume the vehicle is  negative ground. In that case, black,
> negative charger cable to the chassis and red, positive cable to the 
> starter
> insulated circuit.