Is this power inverter overkill?

[dwh]

The info I'm reading says to not exceed 5ft in power cable length. Is that just manufacturer's CYA, or would it be OK to run the length of the vehicle?

Doesn't matter how long the cable is, if it's big enough.

The inverter will shut down if it detects the supply voltage is too low. The supply wire forms a loop/circuit/circle. When the inverter is operating, it will draw down the voltage on that loop (voltage drop). The heavier the load, the more it will draw down the voltage.

So say the inverter shuts down at oh, 10.5v, and the battery is at 12v. If the voltage drop is 1.5v, then the inverter sees 10.5v and shuts down, even though there is still plenty of juice in the battery.

So find a voltage drop calculator and input the worst case numbers, 10.5v, 2000w*, and the wire length. That'll tell you what size wire/fuse you need to minimize the drop. If you set it up for worst case (full load/min drop), then under less than full load it won't have any problems.

*(2000w ÷ 10.5v = 190a)

 

[Happy Joe]

Overkill?? ...only if you use a significant part of its capacity with a smallish (100AH or less) battery, IMO.
...Tried an electric (120 volt) chainsaw with a small generator (no advantage over a gasoline chainsaw, that I could see) worked fine on up to 8" wood... extension cord was no biggie.
Have considered an induction hobb (single burner cooktop); got one in the kitchen; works fine at home but, so far, I can't convinced myself that it would be any better than the propane stove. It would likely be worse; since I would have to either recharge the battery with the vehicle or carry the genny... Although, if I carry the genny I could run a fridge. I almost always camp in the shade/forest so solar recharge of the battery to run the fridge or induction hobb is not really practical.
For me, at least, the hassle of transporting additional junk is why I don't do these.
...I believe that I'll stick with a battery & small inverter (80 watt), along with small, person portable, solar for trips of 4 days or more; for lights and tunes with propane for cooking and a SvenSaw for firewood...

Enjoy!

 

[DaveInDenver]

Wire length does matter. There's current carrying and for this the length isn't a concern, it's either large enough or not.

But length determines voltage drop and can affect how well the inverter reacts to surges. IOW, shutdowns or alarms may occur. The alarms may only be nuisances depending on how it reacts during transitions, but the LV shutdown could be significant.

Practically speaking with a 2kW inverter you need to use at least 1/0 cable and would need runs (which remember are 2x per foot resistance since it's a loop) to be 10 feet or less due to voltage drop. At full load of 2,000 watts even 1/0 and 10' will be almost 0.5V of drop. You really need the inverter to be as close to the batteries and the batteries as close to the alternator as possible. Put the long cable runs on the 120VAC side.

You can get away with smaller wire in other places since the time is shorter (for example starter cables or even winches where a stalled motor isn't left for long periods) but in this case you'd need to carry the full load for long periods so there's no analysis escape from heavy cable and very short runs.

 

[dwh]

Even a half volt drop doesn't much matter.

First of all, that's only going to happen at max load, and second, if the inverter shutdown is set to 10.5v, the half volt drop would mean it shuts down when the battery is at 11v, which is damned near dead anyway.

If the battery is that close to dead, it's probably not a good time to be hitting it with a max load.


Then again, anyone adhering to the 50℅ rule isn't going to let the battery get that far down to begin with, in which case, the half volt drop would be irrelevant.


Depending on the size of the battery/bank, upsizing the wire to completely eliminate the voltage drop is only going to result in a few extra minutes of run time before the battery is completely dead.

If someone really needs to squeeze the battery dry of every last amp*hour then it might actually matter.

 

[dport]

Thanks for the feedback everyone! Now it's time to start measuring.... The non-fun part.

 

[Joe917]

One thing often not considered when sizing inverters and battery banks: the maximum draw for a standard deep cycle lead acid bank should not exceed 25% of capacity(25ah draw for 100ah bank)
the maximum draw for an AGM deep cycle bank should not exceed 30%(30ah for 100ah bank) This is one of the few practical advantages of AGM over flooded.

 

[dport]

Thank you to everyone for your responses. I'll be doing some measurements once the temp gets out of the teens in a day or two! I'm going to poke around underneath the vehicle, and do some looking along the frame rails. I may attempt to place the battery(ies) midway along the frame, if it looks feasible. In my mind right now, I'm considering 2 group 24 batteries if measurements work out.

 

[BBsound]

I have a 2000watt xantrex in my work truck, and a 200 amp alternator will not keep up (at idle speed) using that thing near full capacity.
ie: I can not run a 12.5 amp shop vac for more than several minutes without the voltage getting down in the 10 range.

 

[dwh]

I have a 2000watt xantrex in my work truck, and a 200 amp alternator will not keep up (at idle speed) using that thing near full capacity.
ie: I can not run a 12.5 amp shop vac for more than several minutes without the voltage getting down in the 10 range.

Yea, 200a x 14.5v would be 2900w. But most alternators don't put out full power at idle.

Also most are rated at 80% when hot, so even at higher RPM you might only see 2200w. Then subtract whatever is being used to power the truck and it gets tough to keep up with even a 1500w load like that vacuum.

 

[DaveInDenver]

First of all, that's only going to happen at max load, and second, if the inverter shutdown is set to 10.5v, the half volt drop would mean it shuts down when the battery is at 11v, which is damned near dead anyway.

For the purposes of calculating capacity Odyssey considers a fully discharged battery to be 10.02V (1.65V/cell). So if you're only drawing down to 11V under load then you'll be leaving capacity unused. That's fine, you'll increase the life of your batteries by not discharging them as deeply, but it also means you need to make sure you're adjusting amp-hour assumptions and bank size to accommodate. Depending on how much power you intend to extract 0.5V can be significant.

 

[dwh]

(Trying again. That's the third time in a week I've had a post disappear immediately after I posted it. At first I thought the mods were screwing with me. Now I'm not so sure.)

For the purposes of calculating capacity Odyssey considers a fully discharged battery to be 10.02V (1.65V/cell). So if you're only drawing down to 11V under load then you'll be leaving capacity unused.

Yes, but most inverters shutdown at 10.5v, so that would still be leaving unused capacity even if there were no voltage drop at all. For Odysseys anyway.

But not much unused capacity either way.

Depending on how much power you intend to extract 0.5V can be significant.

If someone really needs to squeeze the battery dry of every last amp*hour then it might actually matter.

I think we just said the same thing.

 

[plh]

I have the 2000w version and its for sale. No practical use for me. It came with an expo trailer I bought last year.

http://www.expeditionportal.com/forum/threads/161230-FS-Xantrex-PROWATT-pure-sine-inverter

I'll negotiate a bit on price

 

[G35Vortec454]

Overkill only if you don't pair it with a house battery bank, which even adds up to the weight. I have the Prosine 3.0kw in my 25ft vehicle, a 2.5kw in my E250, both having a 3-stage charger which is a great reason enough to have it, even if you don't power anything.

 

[comptiger5000]

IMO, there's no such thing as a too-big inverter. I haven't made the jump to pure sine yet (nothing I run seems to care), but I've got a 1500W modified sine Xantrex Xpower in the Jeep (mounted under the back seats with hard-wired outlets on the center console and in the cargo area). No separate house bank (just a single group 34 deep cycle), but it's rare that I need a high draw item for more than a couple of minutes without the engine running. It's big enough to run an electric kettle and I've run an air compressor from it as well (good enough for light use of air tools), so it's definitely come in handy a few times.

Funniest use I've gotten out of it was to defrost a freezer outside while moving with no outlets nearby... Left the Jeep running at high idle for a good 20 minutes while I attacked the freezer with a hair dryer...