Voltage, amps, and watts

I have been doing these 50% to 90% cycles since 2008 alot. My three batteries are just now staring to fall off on their power performance. Even if I do a bunch of full charge states... So I guess they are getting closer to their end life...

Now if you do this to your standard car/truck start battery you find you really only get one cycle of going down real low on the battery charge.

I usually have to replace my truck start battery here about every two years and with my Ham Radio setup I am forever running the start battery down in the truck. Over this last winter I have having to jump start my truck several times over the months. My 2KW generator is secured to the truck bed so I have 120VAC on me all the time and can hook up my portable battery charger and get some juice back in the battery so I can start the truck haha... They gettin used to me doing this in my local WALMART as i sit out there waiting for the wife alot and can't leave my Han radio alone...

2oldman wrote:
Don't expect to be running any toasters or MW's on just 2 batteries. They'll be flat in a couple minutes.

A microwave oven, I agree ... but I with my 8 yr old G27 Interstate battery at full charge I can easily power a 2-slice toaster that pulls a measured 696 watts from my 1000 watt PSW inverter. In a few weeks I'll be replacing that single G27 with a new pair of G31s which together will more than double battery capacity and allow the inverter to easily power any device within it's ratings. :)

As for a coffee machine there's no need to draw anywhere near 1200 watts ... with this same inverter I can also easily power a Cuisinart 5 cup coffee machine that draws a measured 563 watts ... 6 minutes tops and it's done. :)

These are a lot of good replies, thank you all. But guys I am not running coffee pots, toasters, etc. I merely used them for example purposes only. If I use that stuff, I crank up the generator.

clev wrote:
These are a lot of good replies, thank you all. But guys I am not running coffe pots, toasters, etc. I merely used them for example purposes only. If I use that stuff, I crank up the generator.

So that leaves me confused about your original post which began with - "I'm a little confused on inverter use." If you're not using or intending to use an inverter what's the question? :h

I use the inverter just for the tv, TiVo, and dvd. Occasionally, if I'm streaming a movie through my iPhone, I will use my surround system with subwoofer. And there should be no confusion on my initial post. If you read it carefully, I was simply asking how to compute usage time, regardless of what appliance is being used. Others started bringing in different appliances, battery size and number of batteries, and again I tried to steer replies to usage time; as I am doing now.

LOL

clev wrote:
I use the inverter just for the tv, TiVo, and dvd. Occasionally, if I'm streaming a movie through my iPhone, I will use my surround system with subwoofer. And there should be no confusion on my initial post. If you read it carefully, I was simply asking how to compute usage time, regardless of what appliance is being used. Others started bringing in different appliances, battery size and number of batteries, and again I tried to steer replies to usage time; as I am doing now.

rjxj wrote:
LOL

That's constructive. :S

To the OP ...

You yourself introduced the topic of inverters in the first sentence of your very first post - "I'm a little confused on inverter use" so naturally that's going to be the reference point in any following commentary by others. :R Now you're complaining that those of us who took the time to reply to your query aren't being specific enough. :S OK, so to me the answer is obvious but if we have to spell it out ...............

Measure each device you're interested in powering with an inverter using a meter such as a Kill-a-Watt Energy Meter to establish it's average power requirements in watts or amps and multiply each result by the time it's being used so you'll know the watt-hour or amp-hour requirement for each device. You already know your pair of 6 volt batteries offer about 230 AH, half of which is usable if you want to draw them down no more than 50% DOD ... at a nominal 12 volts that 115 AH is equivalent to about 1400 watt-hours.

How you use that reserve is up to you but rather than try to pre-calculate this out I'd find it much simpler to just do a test run, powering what you want for however long you want until your battery bank is drawn down to 50% DOD, keeping in mind that in a normal situation those batteries are not just powering an inverter and it's associated loads but also the rest of the trailer itself. If the results of such a test meet your requirements then you know your setup is sufficient for your intended use, if not you then know you either need more battery reserve OR you need to cut back on usage OR both.

If this isn't the answer you were looking for, my apologies - but at least it's more constructive than "LOL". :W

SoundGuy wrote:

clev wrote:
I use the inverter just for the tv, TiVo, and dvd. Occasionally, if I'm streaming a movie through my iPhone, I will use my surround system with subwoofer. And there should be no confusion on my initial post. If you read it carefully, I was simply asking how to compute usage time, regardless of what appliance is being used. Others started bringing in different appliances, battery size and number of batteries, and again I tried to steer replies to usage time; as I am doing now.

rjxj wrote:
LOL

That's constructive. :S

To the OP ...

You yourself introduced the topic of inverters in the first sentence of your very first post - "I'm a little confused on inverter use" so naturally that's going to be the reference point in any following commentary by others. :R Now you're complaining that those of us who took the time to reply to your query aren't being specific enough. :S OK, so to me the answer is obvious but if we have to spell it out ...............

Measure each device you're interested in powering with an inverter using a meter such as a Kill-a-Watt Energy Meter to establish it's average power requirements in watts or amps and multiply each result by the time it's being used so you'll know the watt-hour or amp-hour requirement for each device. You already know your pair of 6 volt batteries offer about 230 AH, half of which is usable if you want to draw them down no more than 50% DOD ... at a nominal 12 volts that 115 AH is equivalent to about 1400 watt-hours.

How you use that reserve is up to you but rather than try to pre-calculate this out I'd find it much simpler to just do a test run, powering what you want for however long you want until your battery bank is drawn down to 50% DOD, keeping in mind that in a normal situation those batteries are not just powering an inverter and it's associated loads but also the rest of the trailer itself. If the results of such a test meet your requirements then you know your setup is sufficient for your intended use, if not you then know you either need more battery reserve OR you need to cut back on usage OR both.

If this isn't the answer you were looking for, my apologies - but at least it's more constructive than "LOL". :W

Boohoo hoo. Waaaaaaa. Lol.

Good grief, sound, for some reason, almost every post that I make, someone with an attitude, such as yourself has to chime in. I have reread my initial post 4 times and it is very clear. I know how to compute usage with AC electricity, listed a formula, and gave an example. I went on to post my confusion on battery usage time, when using an inverter, and also used an example to assist in computing usage time. And you still don't get it. You get PO'd and link in a meter that measures volts, amps, and watts, which has nothing to do with this thread. Using the device will list volts, etc, but that's the same info that's printed on the appliance and we're right back to my initial question; how do you compute usage time and how long will the battery last with the appliance plugged into the inverter. Now, that question has been answered twice, very effectively, I thanked everyone for the input, and I have not complained. Let it go. OBTW; you did post some good relevant information after the meter reference.

Hi clev,

I've found the listings on appliances are mostly a "guess" at the wattage.

The big problem is that battery discharge is non linear, extremely load dependent, temperature dependent, and other factors such as the age of the battery bank affect results.

Rule of thumb there are about 650 watts of usable power in a group 29 twelve volt jar. Count your jars, multiply by 650 and divide by the total load in watts. That may give you a rough idea of the maximum time under PERFECT conditions. i.e. starting from 100% state of charge with brand new batteries that have been cycled six to twenty-five times with the temperature at 25 C (77 f).