Inverters DC to AC Battery help!
 

Planning to install a 3000watt inverter (not inverter/charger) on a boat
with twin outboards. The House batteries are maxed out with the
electronics. I thinking of installing a dedicated battery bank for the
inverter or utilize one of the starting batteries on the outboard. What do
you think

Bill

Inverters DC to AC Battery help!
 

"Wet-n-Wild Bill" wrote in
m:

Planning to install a 3000watt inverter (not inverter/charger) on a
boat with twin outboards. The House batteries are maxed out with the
electronics. I thinking of installing a dedicated battery bank for
the inverter or utilize one of the starting batteries on the outboard.
What do you think

Bill




Let's do a little arithmetic, first....

3000 watts divided by 12V = 250 amps, if the inverter were 100%
efficient, which it's not. How long do you think those house batteries
can provide 250 amps? 5 minutes? 1 minute? Hmm...it's a point.....

Now, how much is the combined DC output current of the two outboard gas
hogs hangin' off the back? 30A? 20? Some of them put out 7 or 12A to
recharge their starting batteries, but are NOT power sources at all to
save costs and to make that case as small as the customers demand it be.
Obviously, we got no 250 amps to power the inverter when the motor is
running...not at all.

Ok, so the house batteries are out....the outboard powering it just won't
happen...let's say we're going to put in a separate bank to run it and
recharge it when we get back to the dock. Those big, honkin' golf cart
batteries, the big tall ones, 6V, two in series to get 12V, they weigh a
ton, are 330AH at a 20A rate. At a 250A rate, they're only 150AH, maybe
even less. The chemical reaction to make electrons, unfortunately, takes
a lot of time. It's slow. So, if we're going to pull hard on them, and
250A is VERY hard, we'll say, just for argument and flaming on usenet,
150AH. You can use about that much, if they don't melt down at this
awful current level. So, 150AH divided by 250A = 6/10th of an hour at
full power...36 minutes...if the inverter were 100% efficient, which it's
not.

As you can see, this isn't going to happen unless we find room for some
6000AH submarine batteries. Each 2V cell weighs nearly a ton. We need 6
of them in series for 12V. Can we float it? They're 6' tall. Can we
get around 6 of them to get to the head if we mount them in the main
cabin?

What brand of generator was that you were thinking about??.....(c;
Diesel is best, but outboards use gas so we're probably stuck with gas.

I used to have a tagline that said:
"Nothing is funnier than watching a boater with a new 4KW inverter
carrying his electric heater down the dock with a big smile on his face."

Smoke came pouring out of this guy's boat at the dock, one day. Everyone
came rushing with their fire extinguishers to his aid, as it was a
Saturday morning. After the smoke cleared, the curious got looking at
what happened. He had a new inverter, 4KW I think it was. Big money!
He'd installed it, the best he could, and had plugged in a toaster (800
watts) and his coffee pot (1200 watts) to it. It was only half its
capacity, right? Should run great! Unfortunately, for him, it was
pulling 170+ amps off his big house batteries......through #8 red wires
he got from the marine store....which melted and caught the cheap plastic
insulation on fire....

Noone did any arithmetic before he installed it, obviously....(c;

Sure glad he wasn't anchored out in some cove by himself. He would have
jumped overboard as he did on the dock, and probably would have drown in
panic.

What brand of generator was that you were thinking about??.....(c;

Inverters DC to AC Battery help!
 

Wet-n-Wild Bill wrote:
Planning to install a 3000watt inverter (not inverter/charger) on a
boat with twin outboards. The House batteries are maxed out with the
electronics. I thinking of installing a dedicated battery bank for
the inverter or utilize one of the starting batteries on the
outboard. What do you think

Bill

I would have divided the 3000watts (AC) by 120 Volts (AC), not 12 volts.

That size of inverter at 12 volts will need a nominal 25amps when drawing
max power. Add on say 15% for loss on conversion and you would be looking at
near enough 30amps.

Personally, for that sort of current draw I would be looking for about
500A/H batteries and massive section cabling dependant on how close to the
inverter you can locate the batteries.

You need to properly work out the likely maximum draw before working the
figures for required battery power.

Deep-cycle truck batteries are worth a look. Don't buy starter batteries for
this type of application.


Dennis.

Inverters DC to AC Battery help!
 

"Dennis Pogson"

(big snip here)
I would have divided the 3000watts (AC) by 120 Volts (AC), not 12 volts.

That size of inverter at 12 volts will need a nominal 25amps when drawing
max power. Add on say 15% for loss on conversion and you would be looking
at
near enough 30amps.

Personally, for that sort of current draw I would be looking for about
500A/H batteries and massive section cabling dependant on how close to the
inverter you can locate the batteries.

Dennis, Dennis, Dennis!
Please rethink your formula. We all make slight tactical errors. You
may not believe this, but even I have made mistakes!
Old Chief Lynn

Inverters DC to AC Battery help!
 

I do understand the math P=IE! Another concern is recharging the battery
bank for the Inverter. I heard that my outboards have dual 70 Amp alternator
outputs, if so i should be able to utilize the second output for the
inverter battery bank?

My wire size requirement for a 3000w inverter is 4/0 with a 450amp fuse.
The distance of the outboards to the I-Battery Bank will be about 15-20
feet. I'm not sure what the size wire for the alternator output possible 12
ga. Should i increase the size of the wire for this run?

IF i donot have a dual outputs on the alternators what other options would i
have to re-charge the batteries underway?

Bill


"John Weston" wrote in message
. ..
Dennis Pogson, in article 5fbYf.4574$ic1.1629@newsfe5-
win.ntli.net, says...

I would have divided the 3000watts (AC) by 120 Volts (AC), not 12 volts.

That size of inverter at 12 volts will need a nominal 25amps when drawing
max power. Add on say 15% for loss on conversion and you would be looking
at
near enough 30amps.

Personally, for that sort of current draw I would be looking for about
500A/H batteries and massive section cabling dependant on how close to the
inverter you can locate the batteries.

You need to properly work out the likely maximum draw before working the
figures for required battery power.

Deep-cycle truck batteries are worth a look. Don't buy starter batteries
for
this type of application.


Dennis. Watts = Volts x Amps

Watts is power so you need the same power out as into the
inverter plus any losses in the inverters circuits. You can't
get more power out than you put in.

So 3000W = 12V x 250A or 120V x 25A I make it you'll need
250A (plus) at 12V into the inverter to get 3000W out

--
John

Inverters DC to AC Battery help!
 

In article ,
"Dennis Pogson" wrote:

Wet-n-Wild Bill wrote:
Planning to install a 3000watt inverter (not inverter/charger) on a
boat with twin outboards. The House batteries are maxed out with the
electronics. I thinking of installing a dedicated battery bank for
the inverter or utilize one of the starting batteries on the
outboard. What do you think

Bill

I would have divided the 3000watts (AC) by 120 Volts (AC), not 12 volts.

That size of inverter at 12 volts will need a nominal 25amps when drawing
max power. Add on say 15% for loss on conversion and you would be looking at
near enough 30amps.

Personally, for that sort of current draw I would be looking for about
500A/H batteries and massive section cabling dependant on how close to the
inverter you can locate the batteries.

You need to properly work out the likely maximum draw before working the
figures for required battery power.

Deep-cycle truck batteries are worth a look. Don't buy starter batteries for
this type of application.


Dennis.



Dennis, you need to go back and check your MATH....3Kw from 12Vdc
requires 250 AMPs, that is not including any efficency factors....
250 Amps is Welding Cable REQUIRED for battery to Inverter connections.
3Kw means you need BIG batteries with lots of AMP/Hour capacity
if your going to run much.......

Bruce in alaska
--
add a 2 before @

Inverters DC to AC Battery help!
 

On Mon, 3 Apr 2006 00:49:24 -0700, "Wet-n-Wild Bill"
wrote:

Planning to install a 3000watt inverter (not inverter/charger) on a boat
with twin outboards. The House batteries are maxed out with the
electronics. I thinking of installing a dedicated battery bank for the
inverter or utilize one of the starting batteries on the outboard. What do
you think

Bill

Personally I think that you should sit down and analyse what you need
an inverter for? Do you really, really need 3kw.
3000w is 300A after efficiency. a 300A load is 573A Peukert corrected
and will flatten a 450AH bank in .78hrs..
Recharging time with your setup ..... enjoy the boating!
First asses your maximum needs then do the calcs.
Pound to a penny (Sorry Dollar to a doughnut) that you need XXXWatts
for short periods of time. Work out the times and the loads. Do not
even contemplate Air Con, moving to England would be cheaper and
easier!!!!

Richard

Nb "Pound Eater" Parkend G+S UK

Inverters DC to AC Battery help!
 

Bill,

3000 watts is a lot of of AC power for a small to medium sized boat. Most of
the time you will be using only a fraction of the output. But, that doesn't
mean you can undersize the wires. 4/0 cable should be fine. I'm using 4/0
cable for my 4Kw inverter/charger but it's 24 volt on the DC side so the
current is half that of a 12 volt unit.

If the alternator in your outboard is indeed a 70 amp model, the 12 gauge
wire is way undersized. For the distance you listed you should use #1 AWG
for the positive and negative cables between the alternator and battery. You
should fuse the positive wire near the battery. I would suggest an 80 amp
ANL fuse and block. If you use the proper sized wire you won't need a fuse
at the alternator.

Rusty

"Wet-n-Wild Bill" wrote in message
m...
I do understand the math P=IE! Another concern is recharging the battery
bank for the Inverter. I heard that my outboards have dual 70 Amp
alternator outputs, if so i should be able to utilize the second output for
the inverter battery bank?

My wire size requirement for a 3000w inverter is 4/0 with a 450amp fuse.
The distance of the outboards to the I-Battery Bank will be about 15-20
feet. I'm not sure what the size wire for the alternator output possible
12 ga. Should i increase the size of the wire for this run?

IF i donot have a dual outputs on the alternators what other options would
i have to re-charge the batteries underway?

Bill

Inverters DC to AC Battery help!
 

Bill,

What are you going to use that inverter power for? Big difference if
your trying to drive a 2000watt microwave for 10 minutes once a day,
vs. some other use.

The 2000watt inverter option on my Beneteau 393 is powered by (2)
200Amp Hr Deep Cycle 12V, total 400AmpHr. I figure if I run the
Microwave for just 6 minutes, I barely have enough juice for the rest
of my energy budget for the day. That's assuming I can charge the
whole thing each day from dock power. Therefore, I am thinking of
removing the microwave and turning that area into storage.

Inverters DC to AC Battery help!
 

John Weston wrote:
Dennis Pogson, in article 5fbYf.4574$ic1.1629@newsfe5-
win.ntli.net, says...

I would have divided the 3000watts (AC) by 120 Volts (AC), not 12
volts.

That size of inverter at 12 volts will need a nominal 25amps when
drawing max power. Add on say 15% for loss on conversion and you
would be looking at near enough 30amps.

Personally, for that sort of current draw I would be looking for
about 500A/H batteries and massive section cabling dependant on how
close to the inverter you can locate the batteries.

You need to properly work out the likely maximum draw before working
the figures for required battery power.

Deep-cycle truck batteries are worth a look. Don't buy starter
batteries for this type of application.


Dennis. Watts = Volts x Amps

Watts is power so you need the same power out as into the
inverter plus any losses in the inverters circuits. You can't
get more power out than you put in.

So 3000W = 12V x 250A or 120V x 25A I make it you'll need
250A (plus) at 12V into the inverter to get 3000W out

Does that mean that the 300-watt inverter I use to (occasionally) power 2
laptops is taking 25 amps out of my batteries? Must check that cigar-lighter
fuse!

Inverters DC to AC Battery help!
 

Good points John.

Typical rated power to the AC adapter for a laptop is close to 150W, but
output to computer is in order of 65W. Explains why the damn things get hot.

Direct power may well be worth investigation, rather than using DC to AC to
DC.

surfnturf

--------------------------------------
"John Weston" wrote:

Watts = Volts x Amps snip
If your laptops are so inefficient as to require the full 300W
of available input power from the inverter then yes, that
equates to at least 25A at 12V. If it requires less power,
then the current drawn from the 12V battery drops to that
necessary to provide the power.

It doesn't matter that the laptop is being supplied at
120/240V from the inverter (and so the output current will be
around 2.5/1.25A), you'll still need more than 25A at the
input to the inverter if it needs the full 300W. If that is
the case, you wouldn't be using a 300W inverter, since they
don't like running at their maximum output for too long.

Typically, with computers, the rating of the power supply is
based on the expected maximum power requirement of the
peripherals and circuits, plus a bit for reliability. What is
actually drawn from the power source depends on what you are
doing with the computer. I'd expect a computer on a boat to
draw a *maximum* of around 100W (depending on its design) so
your cigar-lighter socket should be OK at around 8A. However,
if you ever try to power 3 or 4 working laptops, then your
fuse may blow, if the inverter doesn't quit first...

snip John

Inverters DC to AC Battery help!
 

John Weston wrote:
surfnturf, in article kcxYf.218601$sa3.159619@pd7tw1no,
says...
Good points John.

Typical rated power to the AC adapter for a laptop is close to 150W,
but output to computer is in order of 65W. Explains why the damn
things get hot.

Direct power may well be worth investigation, rather than using DC
to AC to DC.


A good power supply design shouldn't just dump the excess
power as heat. That's what linear regulators do, not the more
usual switching regulators. However, even they loose
something as heat so, in my opinion, just the one converter,
to provide the laptop's DC input needs directly is best

I use a DC-DC converter (12Vdc battery to approx 18Vdc) to
power my laptop since there is only one conversion loss
(+heat). It seems more efficient to me. Others prefer going
all the way up to 120/240Vac (+heat) to power the laptop AC-DC
power brick (+more heat) which goes back down to the 18-24Vdc
needed by the laptop.

I'm looking at replacing this with a 12V battery driven mini-
ITX when I get a round tuit now my laptop is faulty... I'll be
sailing on a boat with a shuttle-based system this summer so
will see how well it works

The laptop's power brick plus an inverter is far better at dealing with the
voltage "spikes" that an alternator can put out, as I found to my cost a
couple of years ago, blowing the system board using one of these DC-DC
converters.

Inverters DC to AC Battery help!
 

Look at
:http://www.logicsupply.com/product_i...roducts_id/504

The new dc-dc convertor handle things a lot better now.

Hanz

Dennis Pogson wrote:
John Weston wrote:

surfnturf, in article kcxYf.218601$sa3.159619@pd7tw1no,
says...

Good points John.

Typical rated power to the AC adapter for a laptop is close to 150W,
but output to computer is in order of 65W. Explains why the damn
things get hot.

Direct power may well be worth investigation, rather than using DC
to AC to DC.


A good power supply design shouldn't just dump the excess
power as heat. That's what linear regulators do, not the more
usual switching regulators. However, even they loose
something as heat so, in my opinion, just the one converter,
to provide the laptop's DC input needs directly is best

I use a DC-DC converter (12Vdc battery to approx 18Vdc) to
power my laptop since there is only one conversion loss
(+heat). It seems more efficient to me. Others prefer going
all the way up to 120/240Vac (+heat) to power the laptop AC-DC
power brick (+more heat) which goes back down to the 18-24Vdc
needed by the laptop.

I'm looking at replacing this with a 12V battery driven mini-
ITX when I get a round tuit now my laptop is faulty... I'll be
sailing on a boat with a shuttle-based system this summer so
will see how well it works


The laptop's power brick plus an inverter is far better at dealing with the
voltage "spikes" that an alternator can put out, as I found to my cost a
couple of years ago, blowing the system board using one of these DC-DC
converters.

Inverters DC to AC Battery help!
 

John Weston wrote:
Dennis Pogson, in article HmLYf.12303$NN4.1853@newsfe7-
win.ntli.net, says...


The laptop's power brick plus an inverter is far better at dealing
with the voltage "spikes" that an alternator can put out, as I found
to my cost a couple of years ago, blowing the system board using one
of these DC-DC converters.

Interesting observation, Dennis. I haven't had this
experience in either boat or car so I'll have to "look into
it". It suggests bad design because why didn't a similar
spike kill or ride-through the Inverter? The "buck
converter" design should have a similar transformer isolating
input and output as that in the inverter - unless it is a
cheap transformerless design... Perhaps the solution is to
get rid of the spike before it enters the electronics with an
additional filter before the input?? At least that would be
less power wasting.

There are probably cheap DC-DC converters which can't handle spikes, and
more expensive ones that can. The ones sold here in the UK for around £12
look altogether too simple to me. The one referenced by Hanz looks a
different matter altogether. I don't think the one bad experience I had is
sufficient to condemn all such devices, but a new system board these days is
as expensive as a new laptop, so my caution is understandable.

Running the laptop without the engine/alternator would probably be the
safest bet, but we all know crew members who will, as soon as the speed
drops below 2 knots, press the starter button!

Dennis.

Inverters DC to AC Battery help!
 

I've been running VIA system (CL10000,SP13000) for serval years. I've
been going with M1-ATX ,PW-200v,PW80 and now the M2-ATX. I use the power
to run the mainboard and also my LCD monitor and my LCD/TV. The monitor
and tv like only 12v. I power supply provide 12 with 10-24v input.

I'm now looking at Commell LV-675D Pentium M Mini-ITX. The Intel cpu
will be about 2.0 G.(Intel Pentium M760 2.0GHz Processor - 533MHz 2MB
Cache). I use only standard HD and DVD-r/w, not NOTEBOOK drive.

Hanz


John Weston wrote:
Dennis Pogson, in article WJRYf.6695$8o.1068@newsfe6-
win.ntli.net, says...


There are probably cheap DC-DC converters which can't handle spikes, and
more expensive ones that can. The ones sold here in the UK for around £12
look altogether too simple to me. The one referenced by Hanz looks a
different matter altogether. I don't think the one bad experience I had is
sufficient to condemn all such devices, but a new system board these days is
as expensive as a new laptop, so my caution is understandable.

Running the laptop without the engine/alternator would probably be the
safest bet, but we all know crew members who will, as soon as the speed
drops below 2 knots, press the starter button!


Hanz's one is the one I have on my mini-ITX experimental rig:

http://mini-itx.com/store/?c=10#p1830

It's a full power supply for a mini-ITX motherboard, rather
than a simple DC-DC converter for a laptop.

It handles the drop down to 6V whilst the starter runs (but
the house battery doesn't see this - now...). It also handles
up to 28V, clamping any excess. It shuts down everything after
a preset delay so you aren't left with the few milliamps of
drain with a standard inverter or converter.

Your comment about laptop repair is why I'm looking at the ITX
route to use more standardized components.

Inverters DC to AC Battery help!
 

Typical rated power to the AC adapter for a laptop is close to 150W, but
output to computer is in order of 65W. Explains why the damn things get
hot.

So don't bother with DC from the batteries to AC and then back again. Get a
laptop power supply that has a 12V input. The iJuice (aka iGo) adapters
work well. Then it's just a matter of using a cigarette lighter outlet.

Inverters DC to AC Battery help!
 

Bill Kearney wrote:
Typical rated power to the AC adapter for a laptop is close to 150W,
but output to computer is in order of 65W. Explains why the damn
things get hot.

So don't bother with DC from the batteries to AC and then back again.
Get a laptop power supply that has a 12V input. The iJuice (aka iGo)
adapters work well. Then it's just a matter of using a cigarette
lighter outlet.

All these little adapters work well on a regulated voltage, but with an
alternator running, the voltage can be far from regulated.