Question for you electronics wizards...>>>
 

"Marty S." wrote:

I've checked the voltage and either battery by itself reads 12 volts when
hooked up in series, and they are 24 together. However, is there an issue
of amps or watts or current or whatever else flows in the wires? The fish
finder draws about 110 milliamps (whatever that is)... Will it burn out or
crack or implode or fizz out or whatever? (as you can tell, I didn't spend
a whole lot of time paying attention in 7th grade electrical shop)


This is the basic of connecting two (or more) identical batteries, i.e.
with same voltage and amperage, in series or parallel.

* A serial connection will increase the voltage (V) to the sum of all
batteries connected, while the current (A) will not increase.
Example: Two 12V 60A batteries connected in serial give 24V 60A.

* A parallel connection will increase the current (A) to the sum of all
batteries connected, while the voltage (V) will not increase.
Example: Two 12V 60A batteries connected in parallel give 12V 120A.

In your case, with two 12 V batteries connected in serial you will have
12V between ground and the positive terminal (+) of the first battery,
and 24V between ground and the positive terminal (+) of the second
battery, while the voltage across the negative (-) and positive (+)
terminals of each battery is 12V.
This is seen in the following simple schematic:

Ground
------
|
| +-----------+ +-----------+
| | | | |
+-----+ - 12V + +-----+-----+ - 12V + +-----+
| | | | | | |
| +-----------+ | +-----------+ |
| | |
| | |
|-------- 12V --------|-------- 12V --------|
|--- 12V equipment ---| |
| |
| |
|-------------------- 24V --------------------|
|--------------- 24V equipment ---------------|


When having two batteries connected in serial giving a total of 24V, and
you want to tap off 12V volt from one battery to supply 12V equipment,
you must connect the 12V equipment between ground and the positive (+)
terminal of the first battery as shown in the schematic above.

However, be aware of that the discharge of each battery will be uneven
as the first battery will be discharged more than the second battery.

And you don't have to worry about how much current (mA or A) the
equipment draw, as the equipment will not be damaged in any way as long
as the supply voltage is the same as equipment specifications, where 12V
equipment usually is designed for a nominal supply voltage of 13.8V
(i.e. nominal charging voltage).

However, make sure you always connect a suitable fuse between the
positive terminal (+) of the battery and the equipment. The fuse should
have a rating (mA or A) of one or two ratings higher than the current
drawn by the connected equipment.
The basic rule is to keep the fuse rating as low as possible, but of
course not less than the current (mA or A) drawn by the equipment.



Regards,

Stig Arne Bye

E-mail ......:
Contact .....: AOL IM: VT480TFE / MSN: / ICQ: 403349
Snail-Mail ..: P.O.Box 169, NO-9915 Kirkenes, Norway
Homepage ....: http://home.online.no/~stigbye/index.html
------------------------------------------------------------------------
Located just about 70°N 30°E - Almost at the top of the world!

Question for you electronics wizards...>>>
 

"Stig Arne Bye" wrote in message
...

However, make sure you always connect a suitable fuse between the
positive terminal (+) of the battery and the equipment. The fuse should
have a rating (mA or A) of one or two ratings higher than the current
drawn by the connected equipment.
The basic rule is to keep the fuse rating as low as possible, but of
course not less than the current (mA or A) drawn by the equipment.



Regards,

Stig Arne Bye



Just to clarify - the fuse should be rated for no more than the current
carrying capacity of the wiring of the connected device (in this case, the
fishfinder). Point is, the fuse protects the wiring, not the connected
device. Overheated wires cause fires. Not really a big issue with this
particular application, but can be important in higher power devices.

Eisboch

Question for you electronics wizards...>>>
 

Lots of guys that run the 36 volt trolling motors on the big bass
boats only run three batteries and run all the electronics off of one
of the batteries. Running your fish finder off one of your batteries
will not be a problem.

Question for you electronics wizards...>>>
 

Bill and everyone...

Thanks for your help!!! I'll try this out tomorrow!!!

--
Marty S.
Baltimore, MD USA


"Billgran" wrote in message
...



"Marty S." wrote in message
...
I'm running 2 12-volt batteries running in series to power my 24-volt
electric motor in my jon boat (on an electric-only reservoir) and I
want
to
run a fish finder. Here's my question -- can I safely run the fish
finder
off of one of the 2 12-volt batteries while running the 24-volt motor?
Or,
is that going to burn up the fish finder? Should I just invest in a
couple
of 6-volt lantern batteries instead?



The easiest way to hook them up so you will not have electrical
interaction
problems is to attach the negative wire of the fish finder to the same
battery terminal as the negative wire of the trolling motor. That way both
items use the same "ground" path.

Bill Grannis
service manager

Question for you electronics wizards...>>>
 

Marty S. wrote:
I've checked the voltage and either battery by itself reads 12 volts when
hooked up in series, and they are 24 together. However, is there an issue
of amps or watts or current or whatever else flows in the wires? The fish
finder draws about 110 milliamps (whatever that is)... Will it burn out or
crack or implode or fizz out or whatever? (as you can tell, I didn't spend
a whole lot of time paying attention in 7th grade electrical shop)


110 Milliamps (0.110 amps per hour current flow) is what your finder
draws at 12 volts. if you made the mistake and hooked it up to both
batteries (24 volts) then it would draw 210 milliamps, burning out your
finder, then increasing the amp draw even more as wire's insulation
melts, and wires short out to each other) . or at least blowing the fuze.
As long as your hooked to the Positive and negative of the same battery
you have nothing to worry about, your finder is wired up correctly, that
is if your circuit is not grounded to the boat, and all fish finders I
know of are not, they have a floating circuit (both Positive and
negative wires go to the finder)
--
Rodney Long,
Inventor of the Long Shot "WIGGLE" rig, SpecTastic Thread
Boomerang Fishing Pro. ,Stand Out Hooks ,Stand Out Lures,
Mojo's Rock Hopper & Rig Saver weights, Decoy Activator
and the EZKnot http://www.ezknot.com

Question for you electronics wizards...>>>
 

Go for it. Won't hurt a thing.
G
"Marty S." wrote in message
...
I'm running 2 12-volt batteries running in series to power my 24-volt
electric motor in my jon boat (on an electric-only reservoir) and I want
to
run a fish finder. Here's my question -- can I safely run the fish finder
off of one of the 2 12-volt batteries while running the 24-volt motor?
Or,
is that going to burn up the fish finder? Should I just invest in a
couple
of 6-volt lantern batteries instead?

--
Marty S.
Baltimore, MD USA

Question for you electronics wizards...>>>
 

On Wed, 9 Jun 2004 08:29:10 -0700, "Gordon"
wrote:

Go for it. Won't hurt a thing.

=======================

I agree. The current draw of the fish finder is very low compared to
the trolling motor. The batteries won't even know its there unless
you leave it turned on accidently.

Question for you electronics wizards...>>>
 

On Wed, 09 Jun 2004 08:43:15 GMT, "Billgran"
wrote:




"Marty S." wrote in message
...
I'm running 2 12-volt batteries running in series to power my 24-volt
electric motor in my jon boat (on an electric-only reservoir) and I want
to
run a fish finder. Here's my question -- can I safely run the fish
finder
off of one of the 2 12-volt batteries while running the 24-volt motor?
Or,
is that going to burn up the fish finder? Should I just invest in a
couple
of 6-volt lantern batteries instead?



The easiest way to hook them up so you will not have electrical interaction
problems is to attach the negative wire of the fish finder to the same
battery terminal as the negative wire of the trolling motor. That way both
items use the same "ground" path.

That's all I've been trying to say...

Question for you electronics wizards...>>>
 

"Marty S." wrote in message
...
Here's my question -- can I safely run the fish finder
off of one of the 2 12-volt batteries while running the 24-volt motor?

that should work fine.

As daytripper suggested, it would be a lot safer if you connected it across
the battery that had a connection to "ground". The trolling motor could be
totally isolated, but I wouldn't bet on it. It might be isolated as long as
the aluminum case of the lower unit didn't touch anything else.

The trolling motor should have a "positive" and a "Negative" power lead. If
either side was referenced to ground it would be the negative, so connect
your fish finder across the battery that connects to the negative trolling
motor lead.

As another has said, the fishfinder will create an unequal discharge in the
two batteries, so one will go dead before the other. But unless you sit
fishing for a LONG time the fish finder draw will be insignificant. Now, if
you start running spot lights or similar there might be an issue.

Rod

Question for you electronics wizards...>>>
 

In rec.boats Marty S. wrote:
: I've checked the voltage and either battery by itself reads 12 volts when
: hooked up in series, and they are 24 together. However, is there an issue
: of amps or watts or current or whatever else flows in the wires? The fish
: finder draws about 110 milliamps (whatever that is)... Will it burn out or
: crack or implode or fizz out or whatever? (as you can tell, I didn't spend
: a whole lot of time paying attention in 7th grade electrical shop)

Shouldn't be a problem connecting across one battery. Especially given
that the fish finder only draws 110 mA.

b.