I have a trailer with an internal battery to run lights, a winch, the
trailer emergency brake, that sort of thing. My previous tow vehicle had a
charging lead so that the trailer battery was charged by the vehicle while
it was being towed. The current tow vehicle doesn't have this lead
connected, so I charge the battery while stopped with a normal battery
charger.

I would like to connect up a charging lead, but I wonder if it should be
connected directly to the vehicle battery, or to a switched source? My last
truck seemed to have it direct, since I could run the trailer lights by
plugging into the truck, which would be handy.

Any ideas on how this is normally wired would be appreciated.

Cheers, Brian

On Fri, 05 Sep 2003 22:19:00 GMT, Gunner wrote:
Yep. Got to any autoparts store or RV dealer for a "battery isolator".
Its used to charge more than one battery from a common source, but
only allow the battery to be drained from its respective loads. And
put a proper fuse on the line going to the trailer G. I think they
are only around $20 or so.

BTW..I believe the isolator is nothing more than a diode bridge, but I
cannot think how the diodes are oriented at the moment. Im sure the
very good bunch of electron plumbers we have here will be able to give
you chapter and part number G

Ok, ASCII art schematic follows, switch to a fixed pitch font now.

diode 1
x----|-------BAT 1-------Loads
|
Alternator+ ----x
|
x----|-------BAT 2-------Loads
diode 2

Gary

Gary Coffman wrote:
On Fri, 05 Sep 2003 22:19:00 GMT, Gunner wrote:

Yep. Got to any autoparts store or RV dealer for a "battery isolator".
Its used to charge more than one battery from a common source, but
only allow the battery to be drained from its respective loads. And
put a proper fuse on the line going to the trailer G. I think they
are only around $20 or so.

BTW..I believe the isolator is nothing more than a diode bridge, but I
cannot think how the diodes are oriented at the moment. Im sure the
very good bunch of electron plumbers we have here will be able to give
you chapter and part number G


Ok, ASCII art schematic follows, switch to a fixed pitch font now.

diode 1
x----|-------BAT 1-------Loads
|
Alternator+ ----x
|
x----|-------BAT 2-------Loads
diode 2

Hmmm, that only seems to involve one power rail, and puts the load in
series with the battery... you sure about that?

I'd say that it would be more like running several diode bridges off of
the alternator rails, then having the output of the bridge in parallel
with battery and load.

AC1 and AC2 are connections to the alternator:

AC1 --------+-----|------+-----------------------\
| | |
| | |
- - |
^ ^ |
| | |
| | |
+------|-----+--------- AC2 |
| |
| |
+--------------| |--------------------+ - smoothing
| | capacitor
| - + |
+-------------BATT--------------------+
| |
| |
\--------- - LOAD + ------------------/

Connect as many of those as you like to the same alternator by joining
the AC1 and AC2 inputs together. The smoothing capacitor may not be
necessary, the battery itself may smooth the output more than enough -
I'm not sure if a high ripple current into a battery does it any good,
though.

Gary

ABS

On Sat, 06 Sep 2003 13:15:31 +0100, Alaric B Snell
pixelated:

Gary Coffman wrote:
Ok, ASCII art schematic follows, switch to a fixed pitch font now.

diode 1
x----|-------BAT 1-------Loads
|
Alternator+ ----x
| |
| x----|-------BAT 2-------Load -
| diode 2 |
- -
|_______________ground_________________________|


Hmmm, that only seems to involve one power rail, and puts the load in
series with the battery... you sure about that?

He just left off the ground circuit since it was easily inferred.

Imagine the ground dropping down from the Alternator- and running
over to the right side of the load, the load-. (see my mods above)

Yes, a hot leads goes in series through the load to ground.

A smoothing cap isn't necessary since it's performed (to a
great extent) by the solid-state regulator and batteries
are VERY forgiving.


------------------------------
Gator: The other white meat!
------------------------------
http://www.diversify.com Comprehensive Website Development

On Sat, 06 Sep 2003 13:15:31 +0100, Alaric B Snell wrote:
Gary Coffman wrote:
On Fri, 05 Sep 2003 22:19:00 GMT, Gunner wrote:

Yep. Got to any autoparts store or RV dealer for a "battery isolator".
Its used to charge more than one battery from a common source, but
only allow the battery to be drained from its respective loads. And
put a proper fuse on the line going to the trailer G. I think they
are only around $20 or so.

BTW..I believe the isolator is nothing more than a diode bridge, but I
cannot think how the diodes are oriented at the moment. Im sure the
very good bunch of electron plumbers we have here will be able to give
you chapter and part number G


Ok, ASCII art schematic follows, switch to a fixed pitch font now.

diode 1
x----|-------BAT 1-------Loads
|
Alternator+ ----x
|
x----|-------BAT 2-------Loads
diode 2

Hmmm, that only seems to involve one power rail, and puts the load in
series with the battery... you sure about that?

I'd say that it would be more like running several diode bridges off of
the alternator rails, then having the output of the bridge in parallel
with battery and load.

AC1 and AC2 are connections to the alternator:

AC1 --------+-----|------+-----------------------\
| | |
| | |
- - |
^ ^ |
| | |
| | |
+------|-----+--------- AC2 |
| |
| |
+--------------| |--------------------+ - smoothing
| | capacitor
| - + |
+-------------BATT--------------------+
| |
| |
\--------- - LOAD + ------------------/

Connect as many of those as you like to the same alternator by joining
the AC1 and AC2 inputs together. The smoothing capacitor may not be
necessary, the battery itself may smooth the output more than enough -
I'm not sure if a high ripple current into a battery does it any good,
though.

The output of an auto alternator is DC (the rectifiers are internal).
The loads, and the alternator negative in my diagram are, as is normal
in automotive practice, returned via the chassis. I didn't bother to
sketch that in since ASCII art is difficult enough without all that extra
detail.

Gary

On Fri, 5 Sep 2003 10:18:51 -0400, "Brian"
wrote:

I have a trailer with an internal battery to run lights, a winch, the
trailer emergency brake, that sort of thing. My previous tow vehicle had a
charging lead so that the trailer battery was charged by the vehicle while
it was being towed. The current tow vehicle doesn't have this lead
connected, so I charge the battery while stopped with a normal battery
charger.

I would like to connect up a charging lead, but I wonder if it should be
connected directly to the vehicle battery, or to a switched source? My last
truck seemed to have it direct, since I could run the trailer lights by
plugging into the truck, which would be handy.

Any ideas on how this is normally wired would be appreciated.

Cheers, Brian

On mine I have an isolator solenoid that connects the battery of the
vehicle to the charge line.