Can someone help w/the math of the power output on the bed outlet?

So I'm planning to do the 400W anytime mod but in the meantime I would like to know a few things about draw and what not as it applies to what I plan on running. I have a rechargeable lawn mower that has a 36v battery that I plan to charge in the truck from time to time. What I want to know is what the draw of this charger will be when I have a battery on it. I can't seem to find very good specs on the charger/battery combo online but if need be I can go out and take down the specs that are printed on the charger's label if need be.

Will I need the 400 watts or will the 100 watts be sufficient? Will it charge any faster with the 400 watts versus the 100 watts or will the 100 watts supply all that the charger needs to charge at full capacity or will the charger revert to a slower charge at only 100 watts? How long can I leave this charger running with the truck off before the truck's battery is depleted to a level that might leave it unable to crank the engine over? Are we talking many hours or a matter of 15-20min?

Thanks for the help.

 

In 400W mode (which I am assuming is RMS), the current is roughly 3A. In 100W mode, the current is roughly 0.83 A. You need to check the 36V battery charger label (should be on the charger base or on the DC power plug that comes with it) to determine what the current requirement is when its plugged into a 120V AC outlet.

If its less than 3A, then its allowable for you to use only the 400W mode. If its 1A or less, then its allowable for you to use either 100 or 400W mode. If its (much) greater than 3A, then you risk damaging the inverter.

 

Perfect. Thanks for the simple explanation. I was pretty sure that the amps were the important piece of the puzzle but wasn't sure how to arrive to that number from volts and watts. Here's a picture of the charger for the mower in question:



The input says 45 watts so I assume that means no conversion required since the low output is rated at 100 watts, correct? That means that this sucker draws a little under half an amp at maximum, right? I guess they also make a 'fast charge' charger and specific batteries that I may look into since this takes like 10-12hrs to charge from empty which is just way too long for my needs.

I also have a 24v weed eater that may get a charge from time to time as well but the label doesn't say anything about the draw. I may do some research but I would also assume that as long as it doesn't exceed 55 watts I could theoretically plug in BOTH the mower charger AND the weed eater charger and both could happily run off of the 100W low setting, right?

 

Watts is watts... its a measure of power. Volts x amps = watts. For reference.

It should handle the 45+55 in theory but you might as well just do the 400watt mode since when devices first start up...they tend to draw a little more for a split second which may trip the breaker or whatever protects the system.

 

I'm planning to do the mod as soon as my new jumbo cup holder shows up so I don't have to take the center console off multiple times for simple tasks. I'm more curious for my own knowledge if it can handle both on 100W since it will likely be close. In addition I would also like to know how long I could charge both of these items simultaneously with the truck off before I'm in danger of depleting the truck's battery to the point of not being able to turn the engine over. This last thing will be important even once I do the 400W anytime mod. Based on my guestimations from what's been said here I would guess that if I'm drawing 1-3amps it would take many hours to drain my truck's battery even a noticeable amount, right?

 

Ya just be careful not to drain the battery... i think like was metioned above that if the amp draw is to much it should trip a braker to protect somthing?haha....

However i used mine camping last week and plugged in a coffee grinder.. .(very low draw and it drained my brand new truck battery?... less than 8k on it.. and i used it intermintly for like 45 seconds....)Kinda of a piss off in the middle of the mountains....grrrrrr

 

Your battery has an ampere-hours rating. You can determine how many hours the battery will theoretically provide the current you need. I would take those calculations with a grain of salt. As the battery ages, the capability will decline. I don't know what the draw of your starter is, but if you can find out, you could use that number to determine approximately when you should turn off the load on your inverter.

If I were in your shoes I would test all this out at home or where I had a charger for the truck battery before trying it in a remote area.

BTW, the input current will depend on the efficiency of the converter. 80% efficiency would mean 125 watts (a bit over 10 amps) drawn from the battery at 100 watts out.

 

I thought the max draw avail at the outlet would be 3.3 amps? max at 400 watts. 400/120v=3.3? or im probably mis understanding your interpretation....but your totally right..I'll check the ampre hour rating... good point! thank you

 

Yes, the amps at your bed outlet is the important piece.

The math is simple. Watts = Volts x Amperage.

A 12v battery has to put out 33 amps to get 400 watts.

You'll have to plug an ammeter in at the bed outlet and see what your max amperage is.

There's dual-battery setups you can check out to get the amperage up to meet the requirements for a 120v appliance. It's the amps that count.

 

Your Black and Decker Charger should draw about 0.375 amperes

 

At 110 v.

45W / 12v = 4A.

It'll draw 4A on your 12v battery system.

 

Correct.

Plus the parasitic losses from the inverter.

A dome light can dump a battery overnight... I'd be VERY careful with an inverter-on-anytime mod. Even just leaving the inverter at idle will dump the battery overnight.

For comparison, your headlights draw about 8 amps.
How long would you leave your headlights on without the truck running?

 

It states in the owners manual the the engine is to be running when using the
power outlet. Try to think of it as a generator, and not using the truck battery to power your appliances.