On Nov 16, 4:21*pm, JIMMIE wrote:
I want to add a couple of deep discharge type batteries to my truck
for camping but how do I intermix them with the normal auto battery
and charging system. I was thinking about getting a charger meant for
charging batteries from solar panels and connecting the solar panel
input to the generator. A 20A charger cost about $50USD .This would be
very reasonable if I knew it would work as expected.

Jimmie

Hey jimmie:

TI makes a really sweet ic for charging batteries the UC3906. Is the
greatest IC since sliced bread for charging batteries. It took forever
to charge my deep cycle marine battery like a110AHr. A straight
charger it would take a week to charge 100% it's that last 15% that's
the toughest. The UC3906 charged my deep cycle marine battery to full
charge from dead in 10 hours. It's one of the greatest homebrew jobs
I've done. I used it to charge a 110AHr deep cycle marine battery for
my electric bike. I could ride 2 days on a single charge like $0.25
worth of electricty back and forth to work. 45 miles on a single
charge.

73 OM
n8zu

Agreed! I designed a DC UPS power supply for Harris using the
UC3906 to charge a 4Ahr gell cell for wireless pbx. The only
down side is it requires some head voltage for the regulator,
so it won't work well off a 12V vehicle system unless the engine
is running and then not so great.

I still have two of those Harris power supplies one runs an HT
monitoring a repeater and the other runs a scanner and a small
transmitter. The batteries are ten years old and show little
loss of capacity.



raypsi wrote in news:355e6bae-ab52-4d0e-8fde-
:

TI makes a really sweet ic for charging batteries the UC3906. Is the
greatest IC since sliced bread for charging batteries. It took forever
to charge my deep cycle marine battery like a110AHr. A straight
charger it would take a week to charge 100% it's that last 15% that's
the toughest. The UC3906 charged my deep cycle marine battery to full
charge from dead in 10 hours. It's one of the greatest homebrew jobs
I've done. I used it to charge a 110AHr deep cycle marine battery for
my electric bike. I could ride 2 days on a single charge like $0.25
worth of electricty back and forth to work. 45 miles on a single
charge.

73 OM
n8zu

On Nov 17, 7:41*pm, Grumpy The Mule wrote:
Agreed! *I designed a DC UPS power supply for Harris using the
UC3906 to charge a 4Ahr gell cell for wireless pbx. *The only
down side is it requires some head voltage for the regulator,
so it won't work well off a 12V vehicle system unless the engine
is running and then not so great.

I still have two of those Harris power supplies one runs an HT
monitoring a repeater and the other runs a scanner and a small
transmitter. *The batteries are ten years old and show little
loss of capacity.

raypsi wrote in news:355e6bae-ab52-4d0e-8fde-
:



TI makes a really sweet ic for charging batteries the UC3906. Is the
greatest IC since sliced bread for charging batteries. It took forever
to charge my deep cycle marine battery like a110AHr. A straight
charger it would take a week to charge 100% it's that last 15% that's
the toughest. The UC3906 charged my deep cycle marine battery to full
charge from dead in 10 hours. It's one of the greatest homebrew jobs
I've done. I used it to charge a 110AHr deep cycle marine battery for
my electric bike. I could ride 2 days on a single charge like $0.25
worth of electricty back and forth to work. 45 miles on a single
charge.

73 OM
n8zu- Hide quoted text -

- Show quoted text -

I think I am going to try charging it through a 10 amp constant
current source. If it works the way I am thinking as the battery nears
full charge the pass transistor should saturate applying nearly full
generator voltage across the battery topping off the battery. Im
thinking(hoping) that when this occours the voltage drop across the
transistor may be just enough to yield nearly the ideal float voltage
for the batteries.
The batteries normally power my heater and lights for my popup camper
and a couple of radios that are mostly used for rx. With only an
initial charge from the battey charger before leaving home I can camp
about 4 days. With some additioal charging I am hoping to extend it
another 2 oor 3 days. Since our trips usually include a few hours a
day of driving I thought I would use this oppurtunity to top off the
batteries. I have leaned against the idea of just running the engine
for that purpose. The incandescent bulbs I am using in the camper are
the main draw on the batteries perhaps going to LEDs would help.

Howdy,


The saturation voltage will probably be less than a volt,
likely only a few tenths of a volt. When the vehicle is
running the output voltage could be too high. A transistor
that comfortably handles the ten amps is going to be something
like a 2N2955 or 2N3055 there are curves on the data sheets
that tell the story. As the current souce runs out of compliance
and the current drops, the output voltage rises because the
saturation voltage decreases.

There is an easy fix if you use a PNP pass transistor. Clamp
the base at 13.6V plus a base emitter drop, say 0.8V, the output
can't rise higher than the float voltage.

Better yet, use a TL431 to sense the battery voltage to end the
constant current charge by reducing the bias and enter float mode.
(The TL431 is a very handy device and cheap. Check the app notes
and I'm sure you'll find many other uses for it.) Then either NPN
or PNP will work, choose your poison.

I modified a junky old eight amp Kmart charger like this with a
PNP device for charging the six volt battery in my tractor.

You'll need some sort of short circuit protection. During a short
the ten amps times the supply voltage will be dissipated in the pass
device. Could be a fuse or breaker or active protection. I left
this out of my first attempt and the pass device didn't like being
shorted for even a moment. Luckily I tested this before putting it
all back together rather than finding out later on in a snow storm.
The existing thermal breaker was much too slow.

LEDs would be a huge improvement.


73,
Grumpy


JIMMIE wrote in news:1fa6ec49-6eab-4cb6-8eeb-
:

I think I am going to try charging it through a 10 amp constant
current source. If it works the way I am thinking as the battery nears
full charge the pass transistor should saturate applying nearly full
generator voltage across the battery topping off the battery. Im
thinking(hoping) that when this occours the voltage drop across the
transistor may be just enough to yield nearly the ideal float voltage
for the batteries.
The batteries normally power my heater and lights for my popup camper
and a couple of radios that are mostly used for rx. With only an
initial charge from the battey charger before leaving home I can camp
about 4 days. With some additioal charging I am hoping to extend it
another 2 oor 3 days. Since our trips usually include a few hours a
day of driving I thought I would use this oppurtunity to top off the
batteries. I have leaned against the idea of just running the engine
for that purpose. The incandescent bulbs I am using in the camper are
the main draw on the batteries perhaps going to LEDs would help.

On Nov 18, 2:46*am, Grumpy The Mule wrote:
Howdy,

The saturation voltage will probably be less than a volt,
likely only a few tenths of a volt. *When the vehicle is
running the output voltage could be too high. *A transistor
that comfortably handles the ten amps is going to be something
like a 2N2955 or 2N3055 there are curves on the data sheets
that tell the story. As the current souce runs out of compliance
and the current drops, the output voltage rises because the
saturation voltage decreases.

There is an easy fix if you use a PNP pass transistor. *Clamp
the base at 13.6V plus a base emitter drop, say 0.8V, the output
can't rise higher than the float voltage.

Better yet, use a TL431 to sense the battery voltage to end the
constant current charge by reducing the bias and enter float mode.
(The TL431 is a very handy device and cheap. *Check the app notes
and I'm sure you'll find many other uses for it.) *Then either NPN
or PNP will work, choose your poison.

I modified a junky old eight amp Kmart charger like this with a
PNP device for charging the six volt battery in my tractor.

You'll need some sort of short circuit protection. *During a short
the ten amps times the supply voltage will be dissipated in the pass
device. *Could be a fuse or breaker or active protection. *I left
this out of my first attempt and the pass device didn't like being
shorted for even a moment. *Luckily I tested this before putting it
all back together rather than finding out later on in a snow storm.
The existing thermal breaker was much too slow.

LEDs would be a huge improvement.

73,
Grumpy

JIMMIE wrote in news:1fa6ec49-6eab-4cb6-8eeb-
:



I think I am going to try charging it through a 10 amp constant
current source. If it works the way I am thinking as the battery nears
full charge the pass transistor should saturate applying nearly full
generator voltage across the battery topping off the battery. Im
thinking(hoping) that when this occours the voltage drop across the
transistor may be just enough to yield nearly the ideal float voltage
for the batteries.
The batteries normally power my heater and lights for my popup camper
and a couple of radios that are mostly *used for rx. With only an
initial charge from the battey charger before leaving home I can camp
about 4 days. With some additioal charging I am hoping to extend it
another 2 oor 3 days. Since our trips usually include a few hours a
day of driving I thought I would use this oppurtunity to top off the
batteries. I have leaned against the idea of just running the engine
for that purpose. The incandescent bulbs I am using in the camper are
the main draw on the batteries perhaps going to LEDs would help.- Hide quoted text -

- Show quoted text -

Saturation voltage my oh my. A simple DC to DC convertor on the gate
of a FET of like 4 milli ohm so no more Vsat. I've done it with the
UC3906 which is designed to charge lead acid. All you need is a source
that'll will handle all that current. All the tricks I've seen done
with lead acid charging constant current will fawk up ur battery
unless you know when to shut it off like the UC3906 does.
Maybe 3 TL431's as sensors and you can do it. But the UC3906 can
sense a shorted cell and will not charge the battery if there is a
shorted cell.

73 OM
n8zu

Howdy,

Geez... I read this and it confused me. I haven't been
sleeping much and shouldn't post late at night.

The easy fix is to use an emitter follower circuit
where the the constant current load is connected to
the emitter. If you put the regulator in the Positive
side lead use an NPN.

In my instance the current regulator's pass transistor
is in the negative lead so the heatsink is at the same
potential as the vehicle chassis. No insulating hardware
is required.


73,
Grumpy

Grumpy The Mule wrote in
:


There is an easy fix if you use a PNP pass transistor. Clamp
the base at 13.6V plus a base emitter drop, say 0.8V, the output
can't rise higher than the float voltage.

On Mon, 17 Nov 2008 09:06:28 -0800 (PST), JIMMIE wrote:

I didnt think you could charge a deep cycle battery in an
automotive system without damaging the battery.

Hmmm mine is 7yrs old

Howdy


I didn't describe this fully.

Dissipation protection... Put the diode of an optocoupler
with a resistor in series across the pass device's emitter
and collector. Then connect the opto's transistor to the
reference feeding the base of the pass device. Adjust the
resistor in series with the LED so that when there's too
much voltage across the pass device the led lights and
decreases the reference voltage which reduces the current
in the pass device.

Another way to do this requires a zener, two transistors
and three resistors. Optos are cheap enough and it's
less parts to wire up.

I fused the output in case something breaks, to keep the
circuit from being slagged. In a short the thermal breaker
on the transformer took about 45 seconds to trip. I've no
idea what the fault current was but the needle of the lazy
ten amp full scale meter that's built into the charger was
slammed forcefully against the stop.


73,
Grumpy


Grumpy The Mule wrote in
:

You'll need some sort of short circuit protection. During a short
the ten amps times the supply voltage will be dissipated in the pass
device. Could be a fuse or breaker or active protection. I left
this out of my first attempt and the pass device didn't like being
shorted for even a moment. Luckily I tested this before putting it
all back together rather than finding out later on in a snow storm.
The existing thermal breaker was much too slow.

JIMMIE wrote:
On Nov 16, 4:42 pm, wrote:
Why not use a traditional split charge relay.
Alternator output then becomes the limiting factor

I didnt think you could charge a deep cycle battery in an
automotive system without damaging the battery. Its my understanding
that car batteries are designed for a quick charge at realativly high
current while deep cycle batteries require a long low current charge.
To make it work thought you had to have a special charge regulator for
the deep cycle battery.
==========================
'Deep Cycle' batteries should be charged with a current not exceeding
0.1C , meaning that a 80Ah battery should be charged with a current not
exceeding 8 Amperes.

Frank KN6WH

The UC3906 is temp compensated unlike zeners which go up with temp
rise and down with temp decrease. Believe me 1/10 of a volt change
will fawk up the charge rate. Been there done that.

I've quick charged deep cycle marine batteries at work when I forgot
to put my battery on charge on my electric bike. 55 amp in one hour no
problem. Now I was using this my electric bike every day to gits to
work. I got 2 years out of that deep cycle marine battery before my
brushes on my motor were no longer available from Grainger. I didn't
count the times I quick charged the battery at 55 amp rate but it was
quite a few.

If this isn't any everyday thing make it simple, no frilles But a
automotive in car charging system is the worst thing anybody to do to
a battery. I'd let my battery sit on cold concrete before I'd charge
it with an automotive charging system in a car.

73 OM

n8zu



I didnt think you could charge a deep cycle battery in an
automotive system without damaging the battery. Its my understanding
that car batteries are designed for a quick charge at realativly high
current while deep cycle batteries require a long low current charge.
To make it work thought you had to have a special charge regulator for
the deep cycle battery.

==========================
'Deep Cycle' batteries should be charged with a current not exceeding
0.1C , *meaning that a 80Ah battery should be charged with a current not
exceeding 8 Amperes.

Frank * KN6WH