Can a car battery be kept charged with another car battery?

[billcalley]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

 

[AndyS]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

 

[AndyS]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

Andy writes:
Sure, but there are a couple of tricks.

1) Use the portable battery to run a small inverter that will boost
the output
to a couple of volts higher than the portable battery voltage.
Then use
this higher voltage to charge the fixed battery , either thru a
resistor or
some time of current limiting regulator.

2) Use and additional portable battery in series with the first
portable
battery to provide a higher voltage, and proceed as above.

3) The simplest way, however, is to just connect the two batteries
in
parallel with a 1 ohm resistor in the positive leads. When the
portable
battery is "freshly charged" it will bring up the charge in the
fixed
battery, slowly. ( The one ohm is to limit the current so
there's not
any gassing). The portable battery will need to be charged
regularly
and this is only a trickle arrangement. But, if that's all you
need, it
is very simple.

Perhaps there are other suggestions, such as buying a solar array
that
will put a few hundred mils into the fixed battery. That would
work OK as
a trickle maintainer, but remember, it will only work for a few
hours every
day..... The internet will give you the average daily "full sun"
numbers for
various location. In Dallas, for instance, "full sun" only
averages 5 1/2
hours per day. So don't use "peak sun" number for the array
output
without factoring this in.

Just a couple suggestions. I'd be interested in reading some of
the other
replies...... Lots of creative people on this group.

Andy W4OAH in Eureka, Texas

 

[Jim Thompson]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

The most efficient would be to simply swap the batteries.

...Jim Thompson

 

[no_one]

or just bring the fresh battery when you actually need to start the car;
consider disconnecting the in car battery to reduce "nuisance" loads from
the car.

 

[GregS]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

I don't think you can charge one with another battery. The charged battery will
only be 12 volts under load. You need 13.5 volts to charge normally.
Any time a battery looses a great deal of power, it permanately looses power.
It will not last. Jump starting is going to be very hard on the battery. You can
use a battery with increased cells to charge a battery, or use two 12 volters and a
regulator to deliver a lower charge, longer charge time. There is a FAQ or two
on batteries which you shaould read. You can keep a battery trickle charged with a
solar unit, which is what i should have done last winter. i have a very small
solar unit, thats capable of keeping a battey topped off.

greg

 

[Wimpie]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

Hi Bill,

I think you can maintain your battery at a reasonable voltage to avoid
damage, but I don't think that you can give it a full charge or
maintain a full charge. You can use a head light bulb in series with
the positive lead to limit the charge current. Make sure that the
battery that is used for charging is in good condition and fully
charged.

At low temperature the battery to be charged will only accept charge
when the voltage is higher then the normal room temperature voltage
(about -30 .. -50mV/degr C. for a 12V battery). So to avoid sulfation,
you need to charge with higher voltage then your "charger battery" can
give. So I agree with Andy to use a step up converter when you may
expect low temperature conditions.

You may search on "lead acid battery maintenance" for having a table
with charge voltage versus temperature and/or battery voltage versus
capacity left.

If you have regular access to the battery, you may take it home, give
it a full charge (at room temperature) and put it back. At low
temperature, the self discharge is not that high for a f r e s h
lead acid battery. You can leave it for about 6 months after giving it
a full charge.

Best regards,

Wim
PA3DJS
www.tetech.nl

 

[Jim Yanik]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

Get one of those SOLAR panels that plug into the cigarette lighter
socket.They are intended to keep a car battery charged,during storage.

 

[billcalley]

Get one of those SOLAR panels that plug into the cigarette lighter
socket.They are intended to keep a car battery charged,during storage.

--
Jim Yanik
jyanik
at
kua.net- Hide quoted text -

- Show quoted text -

Thanks guys -- your recommendations are great stuff! I'll have to
look into which way to go next.

Very Best Regards,

-Bill

 

[Jasen]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

if the car's outdoors get one of those solar charging panels.
they cost about the same as the battery and there's no maintenance.

or you could take the battery out,

or run a 12V cable (with a fuse at the car end) to somewhere where
you can have a charger....

Bye.
Jasen

 

[Jamie]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

You need slightly higher voltage than that battery you're attempting
to charge.
why not set up some 14..16 volt solar panels to keep the car's battery
charged ?
I know some one that does that now with their camper vehicle at a camp
sight that does not have power all year round. it seems to work very
nicely. He run's a low power 2 meter repeater from it.

 

[Al]

You need slightly higher voltage than that battery you're attempting
to charge.
why not set up some 14..16 volt solar panels to keep the car's battery
charged ?
I know some one that does that now with their camper vehicle at a camp
sight that does not have power all year round. it seems to work very
nicely. He run's a low power 2 meter repeater from it.

Get two 12V motorcycle batteries. Why? smaller, lighter. Hook them in
series to give you 24V. Get two 12V lamps, say rated at 1 amp, hook them
in series. Now connect the minus of the 24V pack to the minus of the 12V
battery. Hook the two series 12V lamps between the plus terminals of the
24V pack and the 12V battery.

If your 12V battery is shorted, the worst that can happen is the two 12V
lamps will light normally. This limites the current to, say, two amps.
Otherwise the 12V battery will have a 1 amp or so trickle charge from
the 24V pack. The amount of charge will be indicated by the brightness
of the two bulbs. The capacity of the two smaller batteries must be
sufficient to recharge your 12V battery to your satisfaction.

When you get home, recharge your motorcycle batteries.

Al

 

[z]

Hi All,

I have a car that is not located near any 120VAC power, so I
cannot use a normal trickle charger to maintain my car's battery at
full charge (the car sits for long periods). But can I use another
(fully charged) lead acid car battery, or perhaps even one of those
portable car jump starter units (like the Black and Decker VEC010BD
300 AMP JumpStarter), to keep my car's battery fully charged? Every
week or so I would bring home the "charger battery" for a recharge,
then hook it back up again to my car's battery through jumper cables.
Is this possible, or are there some major pitfalls?

Thanks,

-Bill

Would work best if the "charger battery" is like an enormous truck
battery.

I've tried using the little portable items with a car that isn't
driven frequently enough to charge the battery, and in the beginning
when there was enough juice to start the car, for some reason just
driving it around even for an hour on the highway wouldn't cause the
car battery to fully charge, and eventually the car battery got low
enough that the portable thing couldn't put it over the top to start
the car.

Now I know what you're thinking, that the car battery had just died,
because that's what I thought too; but I decided to give it one more
chance and connected a little 5 amp Sears charger up for two days
before the current meter looked like zero, and the battery has been
able to start the car fine even with up to two weeks dead time (as
long as I dared leave it) even in the winter. ??

Oh yeah, I had similar bad results with one of those little solar
panel chargers that sit on the dashboard, at least in the winter.
Summer, it seemed to do better.