On 10/12/2010 3:30 PM, Rick Morel wrote:
On Tue, 12 Oct 2010 13:19:12 -0700, Stephen Trapani
wrote:

Keep the 1500 W inverter for your microwave and coffepot. The standby
current will probably exceed the TV's current.

What does that mean?

Standby, or idle current is the Amperage the inverter draws while not
powering anything but is turned on. Of course we all turn the inverter
off when not being used, but it pretty much is also added to whatever
it's powering.

I've seen 1500 W inverters that have a 2.5 Amp idle, and some as low
as 0.5 Amp. Another factor is the inverter is more efficient at about
half power or so.

This is not all that much of an issue for folks with larger house
banks and/or easy means to recharge.

So the questions are, what size and type boat? What Amp Hour house
batteries?

I have two 6v golf cart batteries as a house bank. 500 total amp hours?
I forget. H33. Primarily long weekends use. I just want to be able to
hang on the hook on weekends once in a while without shore power.

I think what you are saying is that if I get a second, smaller inverter
(which probably come pretty cheap nowadays) it will use far less amps to
power the TV and even have some to spare for a DVR. Have I got that right?

You can find a 12V TV, but they're a whole lot more $$$

Ah. So I probably can't just find a cheap one with a 12v power brick
(presumably I tear off the brick) as Wilbur suggests?

Stephen

On Wed, 13 Oct 2010 14:15:12 -0700, Stephen Trapani
wrote:

On 10/12/2010 3:30 PM, Rick Morel wrote:
On Tue, 12 Oct 2010 13:19:12 -0700, Stephen Trapani
wrote:

Keep the 1500 W inverter for your microwave and coffepot. The standby
current will probably exceed the TV's current.

What does that mean?

Standby, or idle current is the Amperage the inverter draws while not
powering anything but is turned on. Of course we all turn the inverter
off when not being used, but it pretty much is also added to whatever
it's powering.

I've seen 1500 W inverters that have a 2.5 Amp idle, and some as low
as 0.5 Amp. Another factor is the inverter is more efficient at about
half power or so.

This is not all that much of an issue for folks with larger house
banks and/or easy means to recharge.

So the questions are, what size and type boat? What Amp Hour house
batteries?

I have two 6v golf cart batteries as a house bank. 500 total amp hours?
I forget. H33. Primarily long weekends use. I just want to be able to
hang on the hook on weekends once in a while without shore power.

I think what you are saying is that if I get a second, smaller inverter
(which probably come pretty cheap nowadays) it will use far less amps to
power the TV and even have some to spare for a DVR. Have I got that right?

You can find a 12V TV, but they're a whole lot more $$$

Ah. So I probably can't just find a cheap one with a 12v power brick
(presumably I tear off the brick) as Wilbur suggests?

Stephen

It really depends on what you are powering. If only lights and TV then
certainly you should be able to get a couple of days use out of them.

The thing about inverters is that they aren't all equally as
efficient. Some require more power to create a specific amount of A.C.
than others, and usually the smaller, cheaper models are the less
efficient.

By the way, how big are these "6 v golf cart batteries" that give you
500 amp-hours? The usual 6 volt golf cart battery is the T-105 that is
rated at 225 amp-hours and wiring two in series to get 12 VDC results
in 225 amp-hours capacity. 4 wired series parallel gives 450
amp-hours.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Thu, 14 Oct 2010 07:30:09 +0700, Bruce in Bangkok
wrote:

By the way, how big are these "6 v golf cart batteries" that give you
500 amp-hours? The usual 6 volt golf cart battery is the T-105 that is
rated at 225 amp-hours and wiring two in series to get 12 VDC results
in 225 amp-hours capacity. 4 wired series parallel gives 450
amp-hours.

You can get 260 A-H with a pair of T-145s but that's about as good as
it gets.

http://www.google.com/search?hl=en&s...q=trojan+t-145

On 10/13/2010 5:30 PM, Bruce in Bangkok wrote:
On Wed, 13 Oct 2010 14:15:12 -0700, Stephen Trapani
wrote:

On 10/12/2010 3:30 PM, Rick Morel wrote:
On Tue, 12 Oct 2010 13:19:12 -0700, Stephen Trapani
wrote:

Keep the 1500 W inverter for your microwave and coffepot. The standby
current will probably exceed the TV's current.

What does that mean?

Standby, or idle current is the Amperage the inverter draws while not
powering anything but is turned on. Of course we all turn the inverter
off when not being used, but it pretty much is also added to whatever
it's powering.

I've seen 1500 W inverters that have a 2.5 Amp idle, and some as low
as 0.5 Amp. Another factor is the inverter is more efficient at about
half power or so.

This is not all that much of an issue for folks with larger house
banks and/or easy means to recharge.

So the questions are, what size and type boat? What Amp Hour house
batteries?

I have two 6v golf cart batteries as a house bank. 500 total amp hours?
I forget. H33. Primarily long weekends use. I just want to be able to
hang on the hook on weekends once in a while without shore power.

I think what you are saying is that if I get a second, smaller inverter
(which probably come pretty cheap nowadays) it will use far less amps to
power the TV and even have some to spare for a DVR. Have I got that right?

You can find a 12V TV, but they're a whole lot more $$$

Ah. So I probably can't just find a cheap one with a 12v power brick
(presumably I tear off the brick) as Wilbur suggests?

Stephen

It really depends on what you are powering. If only lights and TV then
certainly you should be able to get a couple of days use out of them.

Well, occasional microwave, charge cell phones, morning and afternoon
coffee, lights, and hopefully a TV/dvr.

The thing about inverters is that they aren't all equally as
efficient. Some require more power to create a specific amount of A.C.
than others, and usually the smaller, cheaper models are the less
efficient.

By the way, how big are these "6 v golf cart batteries" that give you
500 amp-hours? The usual 6 volt golf cart battery is the T-105 that is
rated at 225 amp-hours and wiring two in series to get 12 VDC results
in 225 amp-hours capacity.

Yeah, that's what I have, 225.

Stephen

On Wed, 13 Oct 2010 18:18:13 -0700, Stephen Trapani
wrote:

Well, occasional microwave, charge cell phones, morning and afternoon
coffee, lights, and hopefully a TV/dvr.

Kind of putting it all together...

I haven't seen the "brick" powered TV's in quite a while. Maybe at a
flea market or something?

The Golf Cart batteries are the best. Two in series should be fine for
what you want, but let's see.

Daily power, taking your "list" above out of order:

First, to determine the daily power requirements you have to take the
current draw, Amps, of each thing and multiply by the number of hours
used to get the Amp Hours per day of each. Remember, anything powered
by the inverter is going to be the 120VAC Watts divided by 10 for 12V
Amps.

We'll do that below, with best guesses.

Lights: I'm sure your talking 12V ones. The anchor light is the
biggie, with incandescent at about 1.5 Amps for 12 hrs.

[ 18 Amp Hours ]

LED would be about 2 Amp Hours, but cost more than a couple more
battereis.

Inside lighting. Varies, but say 2.5 Amps for 5 hours.

[ 12.5 Amp Hours ]

Same as above for LED inside lighting, but not as expensive.

Charging cell phone: Negligible if you have a 12V charger.

Coffee:

We had a 10-cup with thermos type carafe. It drew 75 Amps and ran for
5 minutes. Just to make it easy, let's say 6 minutes, 1/10 of an hour
or 7.5 Amp Hours per pot. Morning and afternoon then are

[ 15 Amp Hours ]

Microwave: We get a bit iffy here. Our 800 or 900 Watt one, I forget
which, drew about 95 Amps. That works out to about 1.6 Amp Hours per
minute of use ( 95 / 60 ). So you don't want to use it too much.

Let's say a couple meals reheated and a few cups of coffee and put it
at 15 minutes. 15 X 1.6 =

[ 24 Amp Hours ]


TV/DVD: Ours, using both was about 5 Amps as I recall. Figuring 4
hours in the evening and 1 hour of news in the morning, that's

[ 25 Amp Hours ]


Adding it all up, the total is:

[ 94.5 Amp Hours per day ]

So you're looking at basically 2 days with your batteries.

With LED anchor and inside lighting,

[ 68 Amp Hours per day ] Quite a difference.

Basically almost 3 days.

Remember you don't want to totally kill your batteries.

Adding another pair of batteries will of course double that and is the
less expensive route then LED lighting.

Rick

On Thu, 14 Oct 2010 05:24:56 -0500, Rick Morel
wrote:

On Wed, 13 Oct 2010 18:18:13 -0700, Stephen Trapani
wrote:

Well, occasional microwave, charge cell phones, morning and afternoon
coffee, lights, and hopefully a TV/dvr.

Kind of putting it all together...

I haven't seen the "brick" powered TV's in quite a while. Maybe at a
flea market or something?

The Golf Cart batteries are the best. Two in series should be fine for
what you want, but let's see.

Daily power, taking your "list" above out of order:

First, to determine the daily power requirements you have to take the
current draw, Amps, of each thing and multiply by the number of hours
used to get the Amp Hours per day of each. Remember, anything powered
by the inverter is going to be the 120VAC Watts divided by 10 for 12V
Amps.

We'll do that below, with best guesses.

Lights: I'm sure your talking 12V ones. The anchor light is the
biggie, with incandescent at about 1.5 Amps for 12 hrs.

[ 18 Amp Hours ]

LED would be about 2 Amp Hours, but cost more than a couple more
battereis.

Inside lighting. Varies, but say 2.5 Amps for 5 hours.

[ 12.5 Amp Hours ]

Same as above for LED inside lighting, but not as expensive.

Charging cell phone: Negligible if you have a 12V charger.

Coffee:

We had a 10-cup with thermos type carafe. It drew 75 Amps and ran for
5 minutes. Just to make it easy, let's say 6 minutes, 1/10 of an hour
or 7.5 Amp Hours per pot. Morning and afternoon then are

[ 15 Amp Hours ]

Microwave: We get a bit iffy here. Our 800 or 900 Watt one, I forget
which, drew about 95 Amps. That works out to about 1.6 Amp Hours per
minute of use ( 95 / 60 ). So you don't want to use it too much.

Let's say a couple meals reheated and a few cups of coffee and put it
at 15 minutes. 15 X 1.6 =

[ 24 Amp Hours ]


TV/DVD: Ours, using both was about 5 Amps as I recall. Figuring 4
hours in the evening and 1 hour of news in the morning, that's

[ 25 Amp Hours ]


Adding it all up, the total is:

[ 94.5 Amp Hours per day ]

So you're looking at basically 2 days with your batteries.

With LED anchor and inside lighting,

[ 68 Amp Hours per day ] Quite a difference.

Basically almost 3 days.

Remember you don't want to totally kill your batteries.

Adding another pair of batteries will of course double that and is the
less expensive route then LED lighting.

Rick


I'm not sure of US prices but LED anchor lights are cheaper then
batteries over here :-) We can also get pin based LED replacements for
hi-intensity bulbs for reading lights.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Thu, 14 Oct 2010 05:24:56 -0500, Rick Morel
wrote:

Adding it all up, the total is:

[ 94.5 Amp Hours per day ]

So you're looking at basically 2 days with your batteries.

With LED anchor and inside lighting,

[ 68 Amp Hours per day ] Quite a difference.

Basically almost 3 days.

Remember you don't want to totally kill your batteries.

Good point.

If you want normal life from your inverter batts it is important to
limit the discharge level to less than 50% (about 11.7 volts when
under load). The net result is that you need twice as many amp-hours
as your energy budget, perhaps more if your recharge time is limited.
It take quite a while to bring the charge level back to a full 100%
because the acceptance rate tapers off once you are above about 80%.
A good design point for A-H capacity is 3 times your energy budget.

AGM batteries have a higher charge acceptance rate but cost about
twice as much. They are worthwhile however if limited by size and/or
weight. Gel cells have good acceptance rates also but are easily
damaged by higher charging voltages. Not worth the risk in my opinion
since AGMs are coming down in price.

On Thu, 14 Oct 2010 08:43:16 -0400, Wayne.B
wrote:

If you want normal life from your inverter batts it is important to
limit the discharge level to less than 50% (about 11.7 volts when
under load). The net result is that you need twice as many amp-hours
as your energy budget, perhaps more if your recharge time is limited.
It take quite a while to bring the charge level back to a full 100%
because the acceptance rate tapers off once you are above about 80%.
A good design point for A-H capacity is 3 times your energy budget.

Wayne, the 50% rule doesn't really apply to golf cart batteries. Back
in my electric car days there was a "trick" we used when we were
stupid and came to a stop from totally discharged batteries. Wait 10
to 20 minutes for the batteries to "self charge", then play
egg-on-accelerator and we'd get another mile or two. Wait and repeat.
Sometimes it took three or four of these cycles to get home.

Having said that, it's a good idea to limit to 20%, simply because
most inverters will shut down around that point.

A good point on taking a while to bring to a full charge. A lot of
folks think you can just pump in the Amps with a big alternator, but
it doesn't work that way in the real world.

A bit of golf cart battery advice. There are two battery manufacturers
in the USA, and they pretty much do the same thing. We bought the
same batteries from Sam's for $72 each as the local dealer had for
$160 each. By same I mean the same brand and model.

Re microwaves and coffee pots. It boils down to personal preference
and the boat systems. In our case we had enough solar so it was "free"
renewable energy as opposed to burning propane that we had to replace.

Rick

On Fri, 15 Oct 2010 08:19:56 -0500, Rick Morel
wrote:

Wayne, the 50% rule doesn't really apply to golf cart batteries. Back
in my electric car days there was a "trick" we used when we were
stupid and came to a stop from totally discharged batteries. Wait 10
to 20 minutes for the batteries to "self charge", then play
egg-on-accelerator and we'd get another mile or two. Wait and repeat.
Sometimes it took three or four of these cycles to get home.

Having said that, it's a good idea to limit to 20%, simply because
most inverters will shut down around that point.

I'm sure that it's possible to get away with an 80% discharge for some
period of time. I've seen some fairly convincing life cycle charts
however that seem to indicate greatly increased battery life at the
50% level as opposed to 80%. I like to baby our house batts as much
as possible given the expense and difficulty of replacing them.

See "Cycles vs Lifespan" at:

http://www.windsun.com/Batteries/Battery_FAQ.htm

http://img32.imageshack.us/img32/9595/batterydod.gif

(from site: http://www.mpoweruk.com/life.htm )

The microwave goes overboard.

Use the stove for cooking.
When heating water, make extra and store in a thermos.

I'm still using my laptop for "TV".
No external display yet.

All lights converted to LED.



Remember you don't want to totally kill your batteries.

Adding another pair of batteries will of course double that and is the
less expensive route then LED lighting.

not so sure about that one...


Rick


--

Richard Lamb