Gear / Technical Help > Remote Power
12V Power Inverter Question
LeftoverSammy:
Hey Now,
I just purchased a 12V, 400W/800W peak power inverter to charge my SLA's at Festy shows during the summer months while camping ;D. My question is for those who have run these P-inverters via their car or deep cycle battery......how long can you run the inverter to charge your SLA without having to start the car to charge your battery?
In the instructions it says to start your car or RV every 60~90min. to avoid draining your battery and run the car to charge the battery for 10min. However I think this is a general rule of thumb only if you are pulling some serious power (over 150W??).
For example: my older style Eco-charger SC-61 pulls about 20W, 120V @ .18A (180mA). The specs on the inverter say it has an “idle current draw” of .4A (400mA) - meaning it draws this current without any devices attached.
Is it correct to assume that when I hook my SC-61 to this inverter it will draw the .18A (20W) plus the load rated at idle current of .4A for a total of .580A or 580mA? That would be a total power of 70W or so (120Vx .580A = 70W). Is this right?? If indeed this is about what the inverter will pull in terms of power how long will the inverter run @ 70W off a standard automotive battery?
If you consider a standard 12V 12AHr SLA and applied around a 580mA current draw the SLA would only last about 21hrs or so run time wise (roughly). Most of the time my 7.2AHr SLA’s only take about 5hrs or so to charge so wouldn’t an automotive battery which has a much bigger amp hr rating pretty much last all night long?? ??? Does anyone know roughly how much a standard automotive battery is in terms of amp hr ratings?? I don’t want to have to wake up every 2hrs during the night to run my rig for 10min. at a time to recharge my auto battery if its just not needed. >:(
Thanks for any info folks!
LoS
leegeddy:
--- Quote from: LeftoverSammy on January 23, 2004, 12:53:11 PM ---Hey Now,
I just purchased a 12V, 400W/800W peak power inverter to charge my SLA's at Festy shows during the summer months while camping ;D. My question is for those who have run these P-inverters via their car or deep cycle battery......how long can you run the inverter to charge your SLA without having to start the car to charge your battery?
In the instructions it says to start your car or RV every 60~90min. to avoid draining your battery and run the car to charge the battery for 10min. However I think this is a general rule of thumb only if you are pulling some serious power (over 150W??).
For example: my older style Eco-charger SC-61 pulls about 20W, 120V @ .18A (180mA). The specs on the inverter say it has an “idle current draw” of .4A (400mA) - meaning it draws this current without any devices attached.
Is it correct to assume that when I hook my SC-61 to this inverter it will draw the .18A (20W) plus the load rated at idle current of .4A for a total of .580A or 580mA? That would be a total power of 70W or so (120Vx .580A = 70W). Is this right?? If indeed this is about what the inverter will pull in terms of power how long will the inverter run @ 70W off a standard automotive battery?
If you consider a standard 12V 12AHr SLA and applied around a 580mA current draw the SLA would only last about 21hrs or so run time wise (roughly). Most of the time my 7.2AHr SLA’s only take about 5hrs or so to charge so wouldn’t an automotive battery which has a much bigger amp hr rating pretty much last all night long?? ??? Does anyone know roughly how much a standard automotive battery is in terms of amp hr ratings?? I don’t want to have to wake up every 2hrs during the night to run my rig for 10min. at a time to recharge my auto battery if its just not needed. >:(
Thanks for any info folks!
LoS
--- End quote ---
if i'm reading you correctly, you're going take a 12v DC-AC converter to run your 12v AC-DC charger to charge your 12v SLA?
why don't you just charge your 12v SLA via your RV's battery?
seems like an aweful lot of wasted energy in heat dissipation from your 2 conversion steps.
marc
LeftoverSammy:
No, you are missing the point. ::) I used the 12V SLA as a COMPARISON illustrating current drain on a 12V SLA vs. one an 12V automotive battery. MY SLA's that need to be charged are 6V not 12V. So I DO need a DC/AC converter to run my AC charger in the field.
Now if I had some sort of DC charger that stepped down from 12V to 6V then I would not need a power inverter would I now?? I'm pretty sure ANYONE who is charging 6V SLA's while at festy's are using 12V power inverters to run their AC to DC 6V chargers...... ;)
If my math is correct one could expect to run this power inverter that is only drawing a meger 70W for many hours on a standard auto battery....I'm just looking for feedback to those of which who have.
LoS
rustoleum:
The invertor I use has a "low" power light that will alert me when I am approaching the point that I won't be able to start my car. I'm going to guess that yours doesn't have that nifty little feature?
Rusty
leegeddy:
--- Quote from: LeftoverSammy on January 23, 2004, 02:02:26 PM ---No, you are missing the point. ::) I used the 12V SLA as a COMPARISON illustrating current drain on a 12V SLA vs. one an 12V automotive battery. MY SLA's that need to be charged are 6V not 12V. So I DO need a DC/AC converter to run my AC charger in the field.
Now if I had some sort of DC charger that stepped down from 12V to 6V then I would not need a power inverter would I now?? I'm pretty sure ANYONE who is charging 6V SLA's while at festy's are using 12V power inverters to run their AC to DC 6V chargers...... ;)
If my math is correct one could expect to run this power inverter that is only drawing a meger 70W for many hours on a standard auto battery....I'm just looking for feedback to those of which who have.
LoS
--- End quote ---
i see your objective now.
may i suggest a voltage regulator circuit that will take your 12v and drop it down to what ever voltage you need? you can get a those gadgets in many places.
i think you're making it more difficult than it really is, IMHO. no offense by my statement. it's just that you want to take a DC voltage > convert it to AC voltage > back to DC voltage to charge a DC voltage supply. you're taking a loooong detour to reach your destination.
>>Now if I had some sort of DC charger that stepped down from 12V to 6V then I would not need a power inverter would I now?? I'm pretty sure ANYONE who is charging 6V SLA's while at festy's are using 12V power inverters to run their AC to DC 6V chargers...... ;)
perhaps people like to take long detours or show of their nice shiny power inverters.
which route would i rather take?
DC > AC > DC > DC or
DC > DC? the latter is MUCH more efficient, according to laws of physics.
marc
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