One more inverter question
 

So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen

Hello Stephen,

Just do the math. 2300 watts is about 200 amps at 12 volts!
That's maybe 3 hp with no losses, so your Yanmar can handle
it, but not many alternators will handle 200 amps
continuously. What your alternator doesn't supply will come
from the batteries. They'll discharge fairly quickly.

Forget the electric heater. A microwave might be practical
for short periods, and a power tool like an electric drill
should be no problem at all.

A boombox may be a small load, but a TV/VCR may not be. For
a load of 120 watts, you're talking about a dc current of
more than 10 amperes. Depending on the state of charge and
capacity of your batteries, you could get a couple of hours
of TV from them.

Good luck.

Chuck



Stephen Trapani wrote:
So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen

Comments below:
"Stephen Trapani" wrote in message
...
So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen

Simple math. Watts = Amps x Volts

So, lets say the alternator attached to your Yanmar is capable of putting
out a sustained 65 amps at 14.6 volts with the engine running at, say, 2000
RPM without overheating or burning up the belt or whatever. And it can do
this for as long as you want to support a heavy load on your inverter.

So: 14.6 volts x 65 amps = 949 watts x 85 % efficiency = 800 watts or so.

This means, if your inverter is 85 % efficient at converting 14.6 volts to
115 volts you will only be able to get enough power from your alternator
through to your inverter to deliver a sustained 800 watts to whatever it is
you want to run. In other words, if you run a 1000 watt electric heater
(and most are 1500 watts or more) off your inverter with your engine running
you will still be slowly running your batteries down. Any sustained load
below 800 watts or so will run off the alternator, with perhaps a little
left to trickle charge the batteries.

On the other hand, if your load is intermittent, like a power tool, or
microwave, it depends on how much of the time the tool/whatever is running.
If it causes the inverter to draw more than your charging system can deliver
it will draw the extra from the batteries but when the tool is off the
alternator will charge the batteries back up. Expect more inefficiency in
charging the batteries so it wont be a 1 to 1 relationship of run time to
recovery time, more like 1 to 2 or worse.

But it can be done and is. You should probably forget about the heater
though...

Make sense?
--
Ken Heaton, Cape Breton Island, Canada
kenheaton AT ess wye dee DOT eastlink DOT ca

Ken Heaton wrote:

Comments below:
"Stephen Trapani" wrote in message
...

So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen


Simple math. Watts = Amps x Volts

So, lets say the alternator attached to your Yanmar is capable of putting
out a sustained 65 amps at 14.6 volts with the engine running at, say,

Okay, so my amp meter reads somewhere around 45 amps when it is charging
the battery, so I figure 45? X 14.6v? so I can expect, say 80%
efficiency just to be safe, 525 watts?

2000
RPM without overheating or burning up the belt or whatever. And it can do
this for as long as you want to support a heavy load on your inverter.

So: 14.6 volts x 65 amps = 949 watts x 85 % efficiency = 800 watts or so.

This means, if your inverter is 85 % efficient at converting 14.6 volts to
115 volts you will only be able to get enough power from your alternator
through to your inverter to deliver a sustained 800 watts to whatever it is
you want to run. In other words, if you run a 1000 watt electric heater
(and most are 1500 watts or more) off your inverter with your engine running
you will still be slowly running your batteries down. Any sustained load
below 800 watts or so will run off the alternator, with perhaps a little
left to trickle charge the batteries.

I can tell by the amp hour rating of the batteries how long the two
group 27s will hold up in this over-use state, right? How do you figure
that? It will suck anything over 45 off the the batteries draining the
batteries faster the higher the charge?

And then if I keep running the over-use after the batteries run down,
the inverter overharge alarm will go on? No big deal I can just turn off
the large draw and charge up the batteries before I turn off the Yanmar?

Will the 12 volt Bible cover this? I just ordered it.

On the other hand, if your load is intermittent, like a power tool, or
microwave, it depends on how much of the time the tool/whatever is running.
If it causes the inverter to draw more than your charging system can deliver
it will draw the extra from the batteries but when the tool is off the
alternator will charge the batteries back up. Expect more inefficiency in
charging the batteries so it wont be a 1 to 1 relationship of run time to
recovery time, more like 1 to 2 or worse.

But it can be done and is. You should probably forget about the heater
though...

One more question, is this sort of usage hard on the batteries at all?
Wear them out faster or anything?

Make sense?

Very helpful, thank you!

Stephen

YES! That type of discharge cycle is VERY hard on batteries. Most Type
27 deep cycle batteries are good for about 280-360 discharge/charge
cycles. You didn't indicate if your type 27s were deep cycle. If they
are standard auto starting batteries, the cycles will be less. You
should never discharge the batteries below 50% capacity. If you want to
run a 2300 watt inverter, get a pair of Trojan J305HC batteries (335 Amp
Hrs). a Balmar 100 Amp alternator, a three stage regulator for the
alternator,a Balmar Duo-charge, and keep the 27 for a starting battery.
krj

Stephen Trapani wrote:
Ken Heaton wrote:

Comments below:
"Stephen Trapani" wrote in message
...

So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen



Simple math. Watts = Amps x Volts

So, lets say the alternator attached to your Yanmar is capable of putting
out a sustained 65 amps at 14.6 volts with the engine running at, say,


Okay, so my amp meter reads somewhere around 45 amps when it is charging
the battery, so I figure 45? X 14.6v? so I can expect, say 80%
efficiency just to be safe, 525 watts?

2000
RPM without overheating or burning up the belt or whatever. And it
can do
this for as long as you want to support a heavy load on your inverter.

So: 14.6 volts x 65 amps = 949 watts x 85 % efficiency = 800 watts or
so.

This means, if your inverter is 85 % efficient at converting 14.6
volts to
115 volts you will only be able to get enough power from your alternator
through to your inverter to deliver a sustained 800 watts to whatever
it is
you want to run. In other words, if you run a 1000 watt electric heater
(and most are 1500 watts or more) off your inverter with your engine
running
you will still be slowly running your batteries down. Any sustained load
below 800 watts or so will run off the alternator, with perhaps a little
left to trickle charge the batteries.


I can tell by the amp hour rating of the batteries how long the two
group 27s will hold up in this over-use state, right? How do you figure
that? It will suck anything over 45 off the the batteries draining the
batteries faster the higher the charge?

And then if I keep running the over-use after the batteries run down,
the inverter overharge alarm will go on? No big deal I can just turn off
the large draw and charge up the batteries before I turn off the Yanmar?

Will the 12 volt Bible cover this? I just ordered it.

On the other hand, if your load is intermittent, like a power tool, or
microwave, it depends on how much of the time the tool/whatever is
running.
If it causes the inverter to draw more than your charging system can
deliver
it will draw the extra from the batteries but when the tool is off the
alternator will charge the batteries back up. Expect more
inefficiency in
charging the batteries so it wont be a 1 to 1 relationship of run time to
recovery time, more like 1 to 2 or worse.

But it can be done and is. You should probably forget about the heater
though...


One more question, is this sort of usage hard on the batteries at all?
Wear them out faster or anything?

Make sense?


Very helpful, thank you!

Stephen

On Sat, 26 Mar 2005 10:40:18 -0800, Stephen Trapani
wrote:

So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen

If I recall correctly, the stock (Hitachi?) alternator on my 2GM was
only rated at 35 amps - that would only be enough to sustain a 3 amp
(360 watt) load at 120 volts. (I replaced the stock alternator with a
higher output unit, and a smart regulator, to give me some chance of
keeping the batteries charged.)

Given the small alternator, and your very small battery bank, I think
the 2300 watt inverter is excessively large. In any case, I would
strongly recommend doing some re-wiring so that you have a dedicated
starting battery, and the inverter, and other non-engine loads, will
run off separate deep cycle batteries.

Forget about electric heat - it just isn't feasible with the batteries
you have. The microwave, power tools (and possibly an electric
kettle) are OK, as they are short-term loads, and the total
ampere-hours used by them should be fairly low. The TV and boom box
would be on for longer periods, but are fairly low draw, so may also
be OK - but I would definitely want a separate starting battery!



--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Peter Bennett wrote:

On Sat, 26 Mar 2005 10:40:18 -0800, Stephen Trapani
wrote:


So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen


If I recall correctly, the stock (Hitachi?) alternator on my 2GM was
only rated at 35 amps - that would only be enough to sustain a 3 amp
(360 watt) load at 120 volts. (I replaced the stock alternator with a
higher output unit, and a smart regulator, to give me some chance of
keeping the batteries charged.)

Given the small alternator, and your very small battery bank, I think
the 2300 watt inverter is excessively large. In any case, I would
strongly recommend doing some re-wiring so that you have a dedicated
starting battery, and the inverter, and other non-engine loads, will
run off separate deep cycle batteries.

Yeah, that would be cool. I've got a '79 Hunter 33.' Maybe I've got a
mental block but I can't figure out where I could possibly put another
battery bank. It's got little enough storage as it is. Seems I'd have to
use the, um lockers under the, um port and starboard settees. Yuck. I
wish I had more clearance above bilge pump in the bilge! The whole dang
bilge is only about 18 inches deep or so.

So that's why I've been asking about the cheaper, easier, but less
powerful solution with the 2 group 27s I know I can fit.

Forget about electric heat - it just isn't feasible with the batteries
you have.

Yeah, I've got a Force 10 propane. I'll get that working soon,
hopefully. I just thought maybe I could use the floor electric heater in
a backup situation if I needed to, on the 850watt setting if I need to.
Looks like it won't be good for much else.

The microwave, power tools (and possibly an electric
kettle) are OK, as they are short-term loads, and the total
ampere-hours used by them should be fairly low. The TV and boom box
would be on for longer periods, but are fairly low draw, so may also
be OK - but I would definitely want a separate starting battery!

So in order to do without the seperate starting battery I can manage
with careful planning, etc?

Stephen

On Sat, 26 Mar 2005 10:40:18 -0800, Stephen Trapani
wrote:

So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

==========================================

A pair of group 27s is totally inadequate for a high powered inverter,
and as others have pointed out, your alternator is not big enough to
make up the shortfall. My recommendation would be (4) 6 volt golf
cart batteries in series parallel. They have about the same foot
print as an 8D but are a couple of inches higher. The 4 golf carts
will deliver 100 amps continuously for over 1/2 hour and
intermittently for quite a bit longer. They can be purchased at Sam's
club for about $50 each and are light enough to be easily handled.
Don't skimp on the battery cables, nothing less than 2/0 will be big
enough.

Peter Bennett wrote:
On Sat, 26 Mar 2005 10:40:18 -0800, Stephen Trapani
wrote:


So, say I've got a measley 2 group 27s and my old Yanmar 2GM15 and I
want to by a 2300watt continuous inverter. BUT...

I'm willing to run the Yanmar while I'm using any heavy loads like a
power tool, microwave, or electric heat and I only use the inverter
*without* running the Yanmar/alternator for small loads like a TV/VCR or
a boombox.

Any problem with that?

Stephen


If I recall correctly, the stock (Hitachi?) alternator on my 2GM was
only rated at 35 amps - that would only be enough to sustain a 3 amp
(360 watt) load at 120 volts. (I replaced the stock alternator with a
higher output unit, and a smart regulator, to give me some chance of
keeping the batteries charged.)


There are two alternators shipped with the small Yanmars - a 35 Amp
and a 50 (or is it 55?) Amp Hitachi. I have the larger. On one
engine I replaced it with a Balmar, but on those times that I've had
to use the Hitachi for primary charging I've been disappointed in its
output. I don't think it ever got to 35 Amps, and this was only when
there was a heavy load.

Stephen Trapani wrote:
Peter Bennett wrote:

The microwave, power tools (and possibly an electric
kettle) are OK, as they are short-term loads, and the total
ampere-hours used by them should be fairly low. The TV and boom box
would be on for longer periods, but are fairly low draw, so may also
be OK - but I would definitely want a separate starting battery!


So in order to do without the seperate starting battery I can manage
with careful planning, etc?

Only if you never go outside the range of SeaTow. If you have a
number of electrical loads, its only a matter of time before you wake
up and find the anchor light, plus the TV that you forgot to turn off,
has drained the batteries. So the question becomes, do you need to
start the engine to get back home? I would think that there is some
place you could find to stash a small AGM starting battery that would
greatly reduce this risk.

BTW, one of my "pet peeves" is using an inverter to power a small TV,
when there are plenty of TVs that run on DC more efficiently. You
should read the specs carefully, because many TVs have significant
loads, even when "turned off." For instance, my AC/DC 9 inch
Panasonic draw almost 2 Amps more when powered on AC, and that load
continues simply by being plugged in. This means that you could
inadvertently draw an extra 25 Amp-hours overnight from this alone.

There are other "forgotten" loads to think about. If you run the
propane through a shutoff solenoid, that may draw a half Amp. And if
you run it all night for a heater, you should have leak detector -
another small but constant load.