As a very basic answer, a 100 amp/hour battery should provide 100 amps for
an hour or 1 amp for 100 hours, in reality of course it would probably
melt if required to do the former. Then you need to factor in age, type of
use, deep charge trickle or whatever. At best it is a guide only as to the
possible maximum the battery can provide.

As I normally daysail I do not need a battery in my boat. But when I
occasionally cruise for a few days, I would like one, but only for the
lights. I do not have other power consuming devices in my boat.

So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

"Jens K" wrote in message
om...
As a very basic answer, a 100 amp/hour battery should provide 100 amps
for
an hour or 1 amp for 100 hours, in reality of course it would probably
melt if required to do the former. Then you need to factor in age, type
of
use, deep charge trickle or whatever. At best it is a guide only as to
the
possible maximum the battery can provide.

As I normally daysail I do not need a battery in my boat. But when I
occasionally cruise for a few days, I would like one, but only for the
lights. I do not have other power consuming devices in my boat.

So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

Please do a power audit (www.reading-college.ac.uk/marine) under course
notes. This will tell you exactly how much electricity you need to store.

Then decide if teh battery will still have enough capacity left to start the
car in adverse conditions (my guess is no).

If you do decide to go ahead with your proposed plan, please be aware that a
car battery is constructed differently to those designed for the use you
have in mind and you will shorten its life. If it is going to be by a
measurable amount, I have no idea, butw ould not take the risk.

I suspect a small leasure battery from a caravan shop and a split charge
relay for the car (from the same source) would be your best bet. You could
even just run a wire from the ignition switch to a croc clip in the boot to
recharge the leasure battery whilst driving.

Tony Brooks

"Jens K" wrote
So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

It'd be like leaving your car's interior lights on for four days. Would the
car still start? Probably, but maybe not. (Mine didn't, leaving me stuck).
Would the battery's life be shortened? Probably, but maybe not.

Bad idea. Car batteries are designed to produce a lot of power for a
few seconds and then be immediately recharged. They can survive being
deeply discharged maybe 5 or 6 times before they die.

Assuming you have a 25 watt anchor light burning 8 hours. That is 16
AH. Then you have 3 10 watt cabin lights burning 4 hours. That is 10
AH. Over a three night weekend that is about 75 AH. That will kill a
group 27 auto battery in short order. You need 150 AH of battery minumum.

The cheapest and longest lasting route would be a pair of $50 golf cart
batteries from Wallymart, Sam's or Costco and a $60 charger with auto
shutoff from Harbor Freight. You will eat that much in car batteries in
one season.

Jens K wrote:

As I normally daysail I do not need a battery in my boat. But when I
occasionally cruise for a few days, I would like one, but only for the
lights. I do not have other power consuming devices in my boat.

So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On 22 Jun 2004 04:48:35 -0700, (Jens K) wrote:

As a very basic answer, a 100 amp/hour battery should provide 100 amps for
an hour or 1 amp for 100 hours, in reality of course it would probably
melt if required to do the former. Then you need to factor in age, type of
use, deep charge trickle or whatever. At best it is a guide only as to the
possible maximum the battery can provide.

As I normally daysail I do not need a battery in my boat. But when I
occasionally cruise for a few days, I would like one, but only for the
lights. I do not have other power consuming devices in my boat.

In the same situation many years ago (very impoverished) I bought a
newer secondhand battery for my ancient car and put the old car one
into the boat. With just one 10 watt tricolour nav light (the old
fluorescent type that gave loads of light for low wattage but rotten
colour cutoff) and a similar wattage single cabin fluorescent, plus
oil cabin and anchor lights, a charged old battery usually lasted a
couple of weeks summer cruising. Nights are short, and you don't put
the nav light on till it's genuinely fairly dark. If there's was
nothing around, I admit I turned it off.

So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

Can you push-start your car?
John Wilson

Remove characters from e-mail address to reply
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In the same situation many years ago (very impoverished) I bought a
newer secondhand battery for my ancient car and put the old car one
into the boat. With just one 10 watt tricolour nav light (the old
fluorescent type that gave loads of light for low wattage but rotten
colour cutoff) and a similar wattage single cabin fluorescent, plus
oil cabin and anchor lights, a charged old battery usually lasted a
couple of weeks summer cruising. Nights are short, and you don't put
the nav light on till it's genuinely fairly dark. If there's was
nothing around, I admit I turned it off.

Can you push-start your car?

Well, I don't think I could push-start it, but rolling down a slope
would work. Unfortunately there is no slope at the marina.
However, I think I won't risk it. Coming back from a cruise and not
being able to start the car will certainly make my wife mad, so I
would have to buy a new battery for this reason anyway.
I guess I just dislike the idea of the thing sitting in the boat doing
nothing, almost the whole year, but needing recharging and
attention...

In article ,
(Jens K) wrote:


In the same situation many years ago (very impoverished) I bought a
newer secondhand battery for my ancient car and put the old car one
into the boat. With just one 10 watt tricolour nav light (the old
fluorescent type that gave loads of light for low wattage but rotten
colour cutoff) and a similar wattage single cabin fluorescent, plus
oil cabin and anchor lights, a charged old battery usually lasted a
couple of weeks summer cruising. Nights are short, and you don't put
the nav light on till it's genuinely fairly dark. If there's was
nothing around, I admit I turned it off.

Can you push-start your car?

Well, I don't think I could push-start it, but rolling down a slope
would work. Unfortunately there is no slope at the marina.
However, I think I won't risk it. Coming back from a cruise and not
being able to start the car will certainly make my wife mad, so I
would have to buy a new battery for this reason anyway.
I guess I just dislike the idea of the thing sitting in the boat doing
nothing, almost the whole year, but needing recharging and
attention...

Sure there is a slope at most marina's. It is called the Launching Ramp.
You just have to be really quick on the clutch, and breaks, and if you
don't get a start, you and your car take a swim........


me

(Jens K) wrote in
om:


Well, I don't think I could push-start it, but rolling down a slope
would work. Unfortunately there is no slope at the marina.

The boat ramp is "sloped"......(c;

John Wilson wrote:
Can you push-start your car?

Probably not, if it's a modern one with computerised engine management.

Andy

"Jens K" wrote in message
om...
As a very basic answer, a 100 amp/hour battery should provide 100 amps
for
an hour or 1 amp for 100 hours, in reality of course it would probably
melt if required to do the former. Then you need to factor in age, type
of
use, deep charge trickle or whatever. At best it is a guide only as to
the
possible maximum the battery can provide.

As I normally daysail I do not need a battery in my boat. But when I
occasionally cruise for a few days, I would like one, but only for the
lights. I do not have other power consuming devices in my boat.

So now the question is this: could I simply move my car's battery to
the boat? Let's say for a four days cruise during summer time. Will it
still start the car afterwards? I guess there will be the pleasant
side-effect that the car will be less likely to be stolen.

I used to use a relay in the boot which would charge a second car battery
when the first was full. This I used successfully for several years
occationally i'd swap the (fully charged) batteries over.

The Q