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

Why not use a traditional split charge relay.
Alternator output then becomes the limiting factor

Hello Jimmie,


I've used a relay to disconnect the auxilliary battery when either
the ignition is off or the auxilliary battery voltage is low ~11.5V.
There is a series diode and resistor in parallel with the relay
contacts to bring the auxilliary battery back up slowly when the
engine is running so the undervoltage lockout can reclose the relay
and not dump the discharged battery on the alternator.

The automotive "ice cube" relays are good for this I've seen some
rated as high as 80A.

Another refinement I did not try is a switch to override the undervoltage
lockout so I could jump the vehicle off the auxillary battery. Perhaps
the switch should be across the diode so the auxillary battery slowly
charges the main battery?


73,
Grumpy



JIMMIE wrote in news:b5cabbfd-f220-4c7e-9cef-
:

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

Grumpy The Mule wrote in
:

A correction...

Another refinement I did not try is a switch to override the _ignition_
lockout so I could jump the vehicle off the auxillary battery. Perhaps
the switch should be across the diode so the auxillary battery slowly
charges the main battery?

wrote:

Why not use a traditional split charge relay.
Alternator output then becomes the limiting factor
I'm not familiar with the term split charge relay, but if it is what is
referred to as a "Battery Isolator" then I actually like the idea. A good
isolator will charge the starting battery first then it will take leftover
power to charge the other battery. Combine this with solar power and you
have a winning combination in my book.

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.

Jimmie

Howdy,

What type of deep discharge battery do you mean?
Gell vs AGM vs VRLA vs Flooded battery generally
require different care.

I use low maintenance flooded deep disharge batteries
and charge them at 20% of their AHr capacity rating.
I'd have no worries about mounting one of these remotely
from the alternator (like in the trunk) and letting the
vehicle system charge it.

Gell or AGM I'd charge at 10% capacity or less. These
would require some current limiting circuit.

The volts per cell for full charge and float charge will be
different too. Though if you keep the battery between 80%
and 20% of full charge it's not an issue.


73,
Grumpy


JIMMIE wrote in news:8795bf5a-715c-4a24-8290-
:

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.

Jimmie

"JIMMIE" wrote in message
...
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

If the RV isn't being used all the time the Battery chemistry is less of an
issue. Deep cycles should be charged at roughly no more than 10 amps. and
floated at 13.2 v. But if it is being cycled, the float value is less of an
issue. You will need the long trip to insure it is up for the next stop.

If you are mounting the second battery under the hood, close to the charger,
then it is best to use NR 10 or 12 wire for the charge line to limit the
current and be able to disable the RV relay rather than leave it charging
every day on long commutes. You will need to check the water more often.

I didn't see my earlier post, again DON'T use a solar charge controller as
most regulate by shorting down the solar panel. If the system voltage is
normal, nothing happens. If it should go high for any reason then it would
simply burn out things.

On Nov 17, 1:58*pm, Grumpy The Mule wrote:
Howdy,

What type of deep discharge battery do you mean?
Gell vs AGM vs VRLA vs Flooded battery generally
require different care. *

I use low maintenance flooded deep disharge batteries
and charge them at 20% of their AHr capacity rating.
I'd have no worries about mounting one of these remotely
from the alternator (like in the trunk) and letting the
vehicle system charge it.

Gell or AGM I'd charge at 10% capacity or less. *These
would require some current limiting circuit.

The volts per cell for full charge and float charge will be
different too. *Though if you keep the battery between 80%
and 20% of full charge it's not an issue.

73,
Grumpy

JIMMIE wrote in news:8795bf5a-715c-4a24-8290-
:



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.

Jimmie- Hide quoted text -

- Show quoted text -


Im not sure but they are sealed 100Ahr batteries and the max recharge
rate is 10amps so definitly not FLOOD.
I have recharged them from my aux power connector in my truck bed but
this took a lot more care and effort than I wanted to give. Wife and
kid thought I was paying more attention to the batteries than them.. I
thought about feeding them from a constant current source. In this
case it would act more like a current limiter.

Jimmie

Howdy,


Ok, the minimum you'd need to charge these is a voltage and
current regulated supply limited to less than 10A and 13.62
for AGM or 13.50 for gell (check the manufacturer's stated
the float voltage). No more than 14.1V in any case.

The vehicle voltage is not much higer than this with the
engine is running. It's possible to build a low drop linear
regulator to serve this function. Linear Technology or Micrel
should have an app note you can work from. This is the one
device solution. You'll get a couple of hundred milliamps
to an amp at 13.6V from as low as 14V maybe a bit less.
Good for keeping the auxilliary battery topped off but not
so good for recharging.

If you want faster recharge (which still won't be very fast
since 120%-140% of 100Ahr is is going to take 12H-14Hr at 10A)
I suggest a SMPS running off the vehicle battery it can charge
the gell cell even when the engine isn't running.

Try National Semiconductor's Web Bench power design tool and
roll your own with their parts.
http://www.national.com/appinfo/power/webench.html

For minimum recharge time a bigger SMPS (maybe a nice push-pull)
is required. I might try a simple switcher boost converter or
switched capacitor converter and raise the vehicle supplied
voltage to about 24V at a few milliamps to bias a series pass
MOSFET linear regulator. The output current and drop-out
voltage are then only limited by the mosfet pass device(s)
.... virtually unlimited! Though not as efficient as the
switcher. Maybe a good idea to throttle back the current
limit from 10A when the engine is running to a few hundred
milliamps when it is not. Though even that's too much if the
vehicle sits unused for too long.

Which causes me to ponder... you'll drain the vehicle battery
unless the engine is running. Even at 10A charge current a
full recharge requires a fair amout of driving! Perhaps it's
better to plan on recharging the battery from "dock side" power
and only trickle charge the battery from the vehicle to keep
it topped off. One of the low drop regulator IC's set to 13.6V
or a simple switcher(tm) would be all you need for that.



73,
Grumpy




JIMMIE wrote in news:0309608e-8c61-4bac-a667-
:

Im not sure but they are sealed 100Ahr batteries and the max recharge
rate is 10amps so definitly not FLOOD.
I have recharged them from my aux power connector in my truck bed but
this took a lot more care and effort than I wanted to give. Wife and
kid thought I was paying more attention to the batteries than them.. I
thought about feeding them from a constant current source. In this
case it would act more like a current limiter.

Jimmie