Watts Help Needed.

[Community Alumni]

I am trying to figure out how long a battery will last. I have Googled it and read a few sites but I still have a few questions.

I have a small TV that I plugged into my Kill a Watt meter. That shows 22 watts. I plan on using a 1000w inverter hooked to one 12v battery. I havn't purchased a battery yet so i'm not sure how many AH I will have to work with.

At 12v that would be 1.8 amps.
at 124v that would be .18 amps.

Which amp usage would I use, the 1.8 amps or .18 amps?

Thank You
Jim

[MrWizard]

they are often used as chargers
they are SOLD as power Supplies for 12v DC electronics

there is small adjustable control (tiny screw driver needed-set it and leave it)
to adjust voltage from 13v to 15v
for correct charging, set at 14.4 to 14.7 and leave it,
use a digital volt meter at the output, with nothing/no battery connected, adj for 14.4v
shut off, then connect to battery with some alligator/battery clamps
turn on , will reach correct volts at full charge,


Megawatt on Amazon



megawatt on ebay

[pianotuna]

Hi,

I would spend the extra 100 dollars for the 1800 watt unit. It is much more capable than the 1000 watt.

Consider this manual charger instead of the automatic:

https://www.harborfreight.com/10250-amp-12v-manual-charger-with-engine-start-60581.html

Do use a coupon to reduce the price.

The Megawatt may be a better choice. Have a look here:

https://www.amazon.com/MegaWatt-S-350-12-9-5-15-Adjustable-Supply/dp/B00JZBE97U

[time2roll]

jbfoster wrote:
Generator - Westinghouse iGen1200. Rated 1,000 watts. $379
Inverter - BESTEK 300 Watt Pure Sine Wave Power Inverter. $45.99
Charger - Ampeak 2/10/25A Smart Battery charger. $67.99
Battery - still need to look but I'm guessing around $120

Jim

List is fine. Not top shelf but will work for what you need.

[Community Alumni]

MEXICOWANDERER wrote:
"SMART" portable battery chargers are just about useless. Save up a bit more then something that works -- a 400 watt Megawatt connected to a 4 hour wind-up timer like an INTERMATIC.

Possibility of a SMART charger ruining your battery = 100%
Possibility of a Megawatt ruining your battery = only if you are unbelievably careless (takes a lot of effort and stubbornness even at that)

The timer saves the day. The INTERMATIC timer does not have a continuous on setting -- 4 hours is it. If you keep the generator running for a month or so and rewind the timer 400 times you probably will damage the battery. This is NOT an old-fashioned uncontrolled garage charger. It has a finite voltage limit where you fix it -- recommended 14.7 volts for wet cell batteries and 14.4 volts for AGM.

I just did a quick look on Amazon and Google and did not find any of those chargers.

Jim

[MEXICOWANDERER]

"SMART" portable battery chargers are just about useless. Save up a bit more then something that works -- a 400 watt Megawatt connected to a 4 hour wind-up timer like an INTERMATIC.

Possibility of a SMART charger ruining your battery = 100%
Possibility of a Megawatt ruining your battery = only if you are unbelievably careless (takes a lot of effort and stubbornness even at that)

The timer saves the day. The INTERMATIC timer does not have a continuous on setting -- 4 hours is it. If you keep the generator running for a month or so and rewind the timer 400 times you probably will damage the battery. This is NOT an old-fashioned uncontrolled garage charger. It has a finite voltage limit where you fix it -- recommended 14.7 volts for wet cell batteries and 14.4 volts for AGM.

[Community Alumni]

oops.... Sorry for the double post.

I got the error so I didn't think it posted the first time.

[Community Alumni]

Keep in mind i am on a small budget. I looked but didn't see much in the 30 to 40 amp range for a battery charger. Didn't see many 150w pure sine inverters either. I think I have decided on the below items. I'm sure there is better quality out there but that comes at a higher cost. I think my usage will be at 80 watts or less usage at any one time. Not sure how long my usage will be every day. I guess that depends on battery size. I think I will be getting around a 100Ah battery. I need to stop by Costco to take look. I would like to stay around $100 for a battery.

Generator - Westinghouse iGen1200. Rated 1,000 watts. $379
Inverter - BESTEK 300 Watt Pure Sine Wave Power Inverter. $45.99
Charger - Ampeak 2/10/25A Smart Battery charger. $67.99
Battery - still need to look but I'm guessing around $120

Jim

[Community Alumni]

Keep in mind i am on a small budget. I looked but didn't see much in the 30 to 40 amp range for a battery charger. Didn't see many 150w pure sine inverters either. I think I have decided on the below items. I'm sure there is better quality out there but that comes at a higher cost. I think my usage will be at 80 watts or less usage at any one time. Not sure how long my usage will be every day. I guess that depends on battery size. I think I will be getting around a 100Ah battery. I need to stop by Costco to take look. I would like to stay around $100 for a battery.

Generator - Westinghouse iGen1200. Rated 1,000 watts. $379
Inverter - BESTEK 300 Watt Pure Sine Wave Power Inverter. $45.99
Charger - Ampeak 2/10/25A Smart Battery charger. $67.99
Battery - still need to look but I'm guessing around $120

Jim

[MEXICOWANDERER]

The A.C. watts vs DC V.A. only works when POWER FACTOR does not enter the scene. Then trying to factor V.A. into ampere hours is another miscue. And yes it all matters and not to a minor degree. Try a 15 to 20% error maximum with an inductive load. This is why I had to extrapolate to watt hours when testing batteries.

Allow for 30% maximum error when trying to make calculations. Favor the battery as -30% can kill it off like a cockroach.

[MEXICOWANDERER]

The A.C. watts vs DC V.A. only works when POWER FACTOR does not enter the scene. Then trying to factor V.A. into ampere hours is another miscue. And yes it all matters and not to a minor degree. Try a 15 to 20% error maximum with an inductive load. This is why I had to extrapolate to watt hours when testing batteries.

Allow for 30% maximum error when trying to make calculations. Favor the battery as -30% can kill it off like a cockroach.

[pianotuna]

Hi,

I would stick with Champion for an inverter generator.

I would not buy a 500 watt inverter. Just not enough oomph and a small price difference. Another reason is if a 500 watt is running flat out it may be stressed (and let out the magic blue smoke), where as a 1000 watt will run such a load all day long til the cows come home.

If you are on a tight budget I'd consider getting the Harbor Freight 3500 watt inverter generator for about $600.00

[BFL13]

Yes, my 75 amp charger (0.7 PF) runs with my gen at absolute max at 1700VA --the gen's "continuous" rating

Westinghouse gens are made by Ford AFAIK, which also makes the same gen for other brands, so you can shop around and see who has the best deal.

EG, this one on sale is the same as the Westinghouse 2000. Always compare shipping costs (ISTR this one has free shipping--but confirm that with seller!)

https://powermaxconverters.com/product/inverter-generator/

[time2roll]

jbfoster wrote:
The bigger one says it does 1800 watts and 15amps. I was looking at the rating of 15amps. Is the 15amp rating for AC current so DC amp rating would be higher?

1800 watts / 120 volts = 15 amps

1800 watts / 12 volts = 150 amps

Although between power factor and efficiency losses I would count on half as the maximum charger rating or 75 amps.
15 to 20 amps charging per battery is plenty. 30 would be a practical maximum.

[Community Alumni]

pianotuna wrote:
Hi jbfoster,

An 1800 watt generator is capable of doing 12 volt charging at up to 120 amps, if the charger is power factor corrected. It will easily work with a 45 amp charger with a power factor of 0.7.

Charging a lead acid battery comes with an "acceptance" charging rate. For a 100 amp-hour battery at 85% of fully charged that is approximately 12.5 amps. As the battery gets closer and closer to 100% the charging rate drops.

Which 1800 watt generator are you considering purchasing?

jbfoster wrote:


I was going to get a 1000 watt generator but I am now getting a 1800 watt generator. It's rated at 15amps so I don't want to use a charger more than 10amps. I don't have an RV. We will be tent camping for a while.

Thank You
Jim

I will re-think the 500 watt inverter. I will consider a smaller one.

I am looking at the Westinghouse iGen1200 and Westinghouse WH2200iXLT generator. The bigger one says it does 1800 watts and 15amps. I was looking at the rating of 15amps. Is the 15amp rating for AC current so DC amp rating would be higher?

Sorry for all the questions


Thanks
Jim

[MrWizard]

Volts times amps equal watts
Stick to using watts, maybe you will better understand

10 amps times 14 charging volts = 140 watts

If your charger used 10 amps at 120v input power that would be 1200 watts ( actually 1200VA aka volt amps, but we won't get into that right now )

You don't need 1800 watt generator for want you have described so far
Although 1800 will be better if you get a MW or a bigger coffee maker

jbfoster wrote:

MrWizard wrote:
you have the use time figured correctly

however it 'ALWAYS' takes more energy than what was used to replace the used wattage aka ampHrs and its not linear
it won't be 10amps for 5 hours, it will start out higher amps and decrease/get less the closer the battery gets to being fully charged
the reversing of the chemical reaction that makes electricity uses power while doing the conversion/restoration

thats why you want a 30-45 amp charger
it will start out high and go down,
you will get charged faster
a 10amp charger will take 7 to 12 hrs to get too full charge
replacing 50 ampHrs
it will start at 10 and go down, making for a long charge cycle

I was going to get a 1000 watt generator but I am now getting a 1800 watt generator. It's rated at 15amps so I don't want to use a charger more than 10amps. I don't have an RV. We will be tent camping for a while. We are inbetween RV's right now due to finances being tight. This is all I can afford for now so I will have to deal with what I can do with what I will be getting.

Thank You
Jim