Power inverter question

menudude · 08-26-2009, 11:16 PM

Alright guys i appologize if this is in the wrong section

I have a 500 watt inverter running my mini tower in my car and it seems to only last about 15-30 minutes with the car off... so i was curious

if i switch to a 200 watt inverter instead do you think it will greatly increase my battery life? How much do you think?

The PC specs call for 180 Watts

Thanks guy!

soundman98 · 08-27-2009, 09:38 AM

the computer should only take what ever it needs to run-- it should not be drawing any more than 180 watts- regaurdless of the inverter it is hooked up to.

a dc-dc power supply might help more-- it will definatly be more efficient

menudude · 08-27-2009, 10:15 AM

arnt those like 200+ dollars?

DarquePervert · 08-27-2009, 03:17 PM

Have you even bothered to look?
As low as seventy bucks, depending on what you need/want.

menudude · 08-27-2009, 03:19 PM

i looked everywhere about 4 months ago... any help with directing me would be greatly appreciated

SjLucky · 08-27-2009, 04:14 PM

What more help do you need? You know your watt draw, DP tossed you a link to the store that sells dc-dc power supplies... Want me to buy it and install it for you? Geez Ums...

seport · 08-27-2009, 05:37 PM

http://www.theinverterstore.com/12_volt_inverter.php

seport · 08-27-2009, 05:46 PM

180Watts is like having all your lights including both front and rear fog lamps ON, so you can make a test by switching the headlights and see for how long the battery survives. If it survives for more than it does with your "PC power inverter", than most probably it's the losses with the power inverter, typically a power inverter has an efficiency of 85%.

menudude · 08-27-2009, 10:39 PM

thank you all for your help minus the useless post by sjlucky... if i purchase a power supply from those links would it just completely bypass the one on the pc? where would the power wires go that power each individual component on the desktop?

soundman98 · 08-28-2009, 09:50 AM

don't mind sj- he just gets annoyed re-answering questions that have already been answered a couple times, which would be why you will need to search around, and find the answers, and most of the power supplies in the mp3 car store also include a picture of the wiring harness that comes with it, so look at the links and you should be able to see how everything hooks up...

menudude · 08-28-2009, 09:55 AM

Thank you... I honestly tried searching but I must not of used the right keywords

IssaquahWA1979 · 10-13-2009, 05:13 PM

the wattage of the inverter does not play any impact on the lack of amp hours the battery can provide and although I agree the DC supplies are more efficient you are not talking about changing the run time by hours more like minutes. Regular vehicle starting batteries are designed to crank an engine for a short period at very high discharge rates they do not like being slowly discharged down to dead as this over time kills them and its why they do not do the job well.

menudude · 10-13-2009, 06:21 PM

Quote: Originally Posted by IssaquahWA1979

the wattage of the inverter does not play any impact on the lack of amp hours the battery can provide and although I agree the DC supplies are more efficient you are not talking about changing the run time by hours more like minutes. Regular vehicle starting batteries are designed to crank an engine for a short period at very high discharge rates they do not like being slowly discharged down to dead as this over time kills them and its why they do not do the job well.

Thanks for your help, you think i should replace the battery?

IssaquahWA1979 · 10-13-2009, 07:13 PM

if you are planning to use the system with the vehicle off for durations of time then yes I would or put a secondary battery on a battery isolator and use a deep cycle battery for the pc. I know many like the optima line but I have found them to be disappointing when it comes to long term durability and output performance I myself prefer odyssey batteries although expensive will last a long time and give some exceptional performance, Sears has a house brand that is actually Odyssey.

Based on your 180 watts of usage you can roughly figure 18 amps of current draw (adding in some room for inverter and cable losses) so if you add that up per hour and multiply by 2 that is what size battery you should be using. So for example if you want to run your system for say 10 hours you would need a 180 amp hr. battery at full discharge. So in reality you need two of them in order to only pull the battery down 50% which is about as low as you want to go for repeated discharge cycles. If it sounds expensive it is, not to mention not very practical when it comes to the weight of such sized batteries.

One other thing I might add is you may want to use a watt meter to see how much power you are really pulling with the PC or a ammeter to see exactly what you are pulling from the battery, this will give you some real numbers to base your run times and battery needs in order to fill your run time expectations.

menudude · 10-13-2009, 07:16 PM

Quote: Originally Posted by IssaquahWA1979

if you are planning to use the system with the vehicle off for durations of time then yes I would or put a secondary battery on a battery isolator and use a deep cycle battery for the pc. I know many like the optima line but I have found them to be disappointing when it comes to long term durability and output performance I myself prefer odyssey batteries although expensive will last a long time and give some exceptional performance, Sears has a house brand that is actually Odyssey.

Based on your 180 watts of usage you can roughly figure 18 amps of current draw (adding in some room for inverter and cable losses) so if you add that up per hour and multiply by 2 that is what size battery you should be using. So for example if you want to run your system for say 10 hours you would need a 180 amp hr. battery at full discharge. So in reality you need two of them in order to only pull the battery down 50% which is about as low as you want to go for repeated discharge cycles. If it sounds expensive it is, not to mention not very practical when it comes to the weight of such sized batteries.

One other thing I might add is you may want to use a watt meter to see how much power you are really pulling with the PC or a ammeter to see exactly what you are pulling from the battery, this will give you some real numbers to base your run times and battery needs in order to fill your run time expectations.

Thanks for your help. It looks like the cheapest route would be a laptop or small carputer. I appreciate the time you took to answer my questions.

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