CCred68046 wrote:

Um....ok, but why "dissimilar"? I'm curious about two different
batteries.


One is an old 1000 CCA deep cycle for trolling and the other is a new 420 CCA
starting battery. Switching them to the both position will cause the good
battery to be discharged by the weaker battery. The way it was described to me
by a battery expert was "If you pour good milk into bad milk you have a bunch
of bad milk".

Get a regular 1/both/2 battery switch. There's no problem switching
those 2 batteries together when charging. Just use the 1 or 2 positions
when you want to troll or start and use both when the engine is running.

Except when brand new batteries are fully charged, there's almost never
a situation when a boat with 2 batteries will have both of them in the
same state of charge. People parallel them all the time to charge
without a problem.

Steve

"Doug Kanter" wrote in message
...


It's funny: No matter how many times I've wondered how fast my boat would
fill up with water, I've never removed the drain plug while fishing a mile
from shore. I really want to, but I can't bring myself to do it.


Oh go ahead! Remove that plug. See how it feels and how much water
comes in through that little hole. See how much time you would have.
But be on your trailer or at the dock and with good pumps - and ready
to put the plug back in.

Huh?

On 11 Aug 2004 22:02:21 GMT, obull (CCred68046)
wrote:

Um....ok, but why "dissimilar"? I'm curious about two different
batteries.

One is an old 1000 CCA deep cycle for trolling and the other is a new 420 CCA
starting battery. Switching them to the both position will cause the good
battery to be discharged by the weaker battery. The way it was described to me
by a battery expert was "If you pour good milk into bad milk you have a bunch
of bad milk".

Just so I can get a grasp on this, why do you need to switch them?
Unless you are using something like a charger and want to switch it
from battery to battery, but that doesn't make much sense.

Are they not both 12 Vdc batteries?

Later,

Tom

On Wed, 11 Aug 2004 19:20:30 -0400, "Gary Warner"
wrote:


"Doug Kanter" wrote in message
...


It's funny: No matter how many times I've wondered how fast my boat would
fill up with water, I've never removed the drain plug while fishing a mile
from shore. I really want to, but I can't bring myself to do it.


Oh go ahead! Remove that plug. See how it feels and how much water
comes in through that little hole. See how much time you would have.
But be on your trailer or at the dock and with good pumps - and ready
to put the plug back in.

Huh?

I did this once on my Ranger. Didn't notice it until I was walking
down the ramp to the boat and watched the bilge pump spray water into
another boat a the ramp.

Needless to say, the other guy was somewhat annoyed. :)

Later,

Tom

Most likely you were talking to a milk expert. In order for one battery to
discharge into another there must be a voltage
difference between two - one battery charged and another drained.
Discharge/charge current will be limited by voltage difference (open ckt.)
divided by sum of internal (source) impedances of both batteries. After
initial surge current will exponentially go down to zero as result of
equalizing of battery voltages. Since battery internal impedances are very
low and there were no other power dissipating loads in a ckt., there is no
signifficant energy loss.
In other words both batteries may be connected together. As soon as they
both charged -there no current from one to another. Charging current will be
shared by both differently every time due to difference in charge and
capacity..
Unlike bad milk there are no bad electrons.

Good luck.

"CCred68046" wrote in message
...
Um....ok, but why "dissimilar"? I'm curious about two different
batteries.

One is an old 1000 CCA deep cycle for trolling and the other is a new 420
CCA
starting battery. Switching them to the both position will cause the good
battery to be discharged by the weaker battery. The way it was described
to me
by a battery expert was "If you pour good milk into bad milk you have a
bunch
of bad milk".

Should not matter, as sonn as they are both the smae voltage, then no
current. Get a 1/2/both switch so you can connect both togehter, of both
are low and you need a little extra energy. Run the battery on 1 (starting)
all the time and add a battery combiner from West Marine (about $90) This
connects both together for charging when the voltage rises above 13.4V.
Bill

CCred68046 wrote:
Does anyone know of a 2 battery switch that just allows for the use of one
battery or another at a time but NOT both? I just want a simple A/B switch.

Thanks.
The usual 1-both-2-off can be used this way. If you don't like it,
don't use it (the both position) Some day you might want it. Some
day you might want to charge both batteries at once.

A physical barrier to the both position might suit you.

Regardless, 2 simple off on swithes still allow a both selection.
Heavy enough switches not of the usual configuration in use in
millions of boats might well cost more, and as such, do not offer
the field defeat swith protection feature found in the typical switch.

Terry K

So... rather than replace the old, oddball battery(s), you think a different
switch is an appropriate fix? Gimme a break!

OK guys, I'm not going into huge detail here, I have done that before with this
problem. My Johnson outboard has an un-regulated charging system. There is
really nothing on my boat that uses any current to speak of. Once the starting
battery is fully charged (very quickly) the voltage go's up to 16+ and this is
not good. Its much cheaper to buy the switch to let the voltage go to the
trolling motor battery which is usually discharged enough to keep it "busy"
than it would be to try and put a regulator on it. To further complicate
matters the charging system is only 5 amps so when I used a combiner, both
batteries wound up low (I cant win!). Sooooo, I figure I can watch the guage
and just flip the switch when the voltage gets too high and let the trolling
battery have it. At 5 amps it would take it a looooooong time to recharge the
trolling battery. If anyone else has a better plan I am listening.

On 12 Aug 2004 05:23:20 GMT, obull (CCred68046)
wrote:

So... rather than replace the old, oddball battery(s), you think a different
switch is an appropriate fix? Gimme a break!

OK guys, I'm not going into huge detail here, I have done that before with this
problem. My Johnson outboard has an un-regulated charging system. There is
really nothing on my boat that uses any current to speak of. Once the starting
battery is fully charged (very quickly) the voltage go's up to 16+ and this is
not good. Its much cheaper to buy the switch to let the voltage go to the
trolling motor battery which is usually discharged enough to keep it "busy"
than it would be to try and put a regulator on it. To further complicate
matters the charging system is only 5 amps so when I used a combiner, both
batteries wound up low (I cant win!). Sooooo, I figure I can watch the guage
and just flip the switch when the voltage gets too high and let the trolling
battery have it. At 5 amps it would take it a looooooong time to recharge the
trolling battery. If anyone else has a better plan I am listening.

I've looked around and through my supplier books and I can't find just
a 1/2 position switch applicable for marine use.

I'm not trying to be offensive here, but you are over complicating the
issue. Just pick a switch and either disable the both position or
just don't use it.

Later,

Tom

I'm not trying to be offensive here, but you are over complicating the
issue. Just pick a switch and either disable the both position or
just don't use it.

No offense taken. I sometimes let others use this boat. If a 1-2 switch was
available I would prefer it due to the circumstances. Your help was
appreciated. Thank you Tom.