Inverter questions

2oldman wrote:
2 batteries will be marginal. 4 is better.

I would agree with that... you should be ok with a K-Brewer but man that's a lot of non degradable trash (there is a company that makes bio-degradable K-Cups but even those have non degradable wrappers)

I like my 4-Cup Auto Drip much better. Cheaper too Plus I have an "Take your pick" brewer (Use filter basket or K-Cup holder)

There are other things I do not like about MOST of the Kurig units as well Save I think for the 10)

But I really like my auto-drip
And I have a french press too.

Based on my experience it might work if you are fully charged. I have a 1000 watt inverter and tried to run a 700 watt coffee maker off of it when the batteries were at about 70%. Drained the out rush of power dropped the battery bank too low and shut the inverter down due to a low power warning.

I still think 4/0 is goofy for a 2000w inverter. I use the divide by 10 rule for DC amps so that would be 200 amps draw at full load.

By comparison, my Vector MSW 2000w inverter that is heavy duty for running motors too (now in the attic), has these specs for 6 ft and 10 ft:

1500w version- #2AWG, 2/0 and a 300w ANL fuse (they cover for the surge rating of 3000w it seems)

2000w version- 1/0, 3/0, and a 500w ANL fuse.

If you don't cover for the very brief surge time, you can use the ampacity/gauge for 150 or 200 amps.

On voltage drop, first you get the instant drop, but then you get a slow drop as the load continues running and battery voltage comes down, bringing inverter voltage down with it.

The trick is to have enough "room" for the load to finish running before the inverter sees 11.0 volts and starts alarming.

So in my case above, I can start with the batteries at 12.1v in the morning and see maybe 11.4v with the toaster at first, and by the time the toast pops up, I am still above 11.0v.

So IMO there is no need for over-doing the wire gauge unless you are operating closer to the margins. EG, running the MW for 10 minutes instead of just 5 minutes. You need more "room" after the initial drop with the longer run.

Keep in mind that a coffee maker has a very high initial draw. On my previous setup, I would frequently get the low voltage 'beep' from a 2000w PSW inverter off of 4 batteries when using a Tassimo (which is similar to the K-cup). That was with 4/0 wiring and full solar. The weak point was the inverter.

2manytoyz wrote:
I still have to use a DC-DC converter to take 48V and make 12V for the lighting and accessories..

Yes, so do I. I run high-draw appliances, even the air, and hundreds of amps at 12v heats things up, including the batteries.

2oldman wrote:
Higher voltage beats fat wire.

Twice the voltage, half the current to do the same work. Very true, but that also comes at a cost. The battery bank would have to be configured for a higher combined voltage, but most RVs are 12V.

12V PSW inverters are cheap and very common. 24V and 48V are less common, and typically cost more. I put a 48V inverter in my golf cart, which uses a 48V battery bank. Thin wire by comparison (1500W inverter, using 6 ga). I still have to use a DC-DC converter to take 48V and make 12V for the lighting and accessories.

As my other recent post mentioned the cost of the fat wire is $51 total. Deduct the cost of thinner wire required for a higher voltage inverter.

Now take $352 for the Xantrex PSW 2KW inverter, and compare the cost to a higher voltage inverter. Is there a cost savings?

Higher voltage is more efficient, but not necessarily cheaper or easier.

But different strokes for different folks.

BFL13 wrote:
4/0 wire at 6 ft is crazy IMO. I saw that table from Xantrex. They appear to want too small a voltage drop.

If you're not FULLY loading the inverter, then the wire requirement is less.

But if you want to be able to supply a full 2KW from this inverter, then it NEEDS fat wire.

Here's a pic from the 2000 Watt load test I did with my Xantrex:



That's almost 208 Amps! A fully charged battery bank is 12.7V at rest. Under a heavy load, even fully charged, the voltage drops. A less than 1V drop causes the inverter to shutdown. Furthermore, as the voltage drops, the current requirement to do the same work goes UP. All wire has a voltage drop too. Thinner wire loses more voltage per foot.

This topic has come up a lot on the solar forums. It's also comes up in the inverter reviews on Amazon. People claiming their inverter won't supply the rated capacity. The two things that will cause this is undersized wire, and too small of a battery bank. That's not crazy, it's science. Same thing as hooking a garden hose to a fire hydrant. Fine for watering flowers, but if you need to use the higher flow for fighting a fire... you're hosed. :p

So what kind of expense is properly sized wire? I buy 4/0 welding cable (very flexible - 2054 strands) from Wesbell: https://wesbellwireandcable.com/Welding/Welding4_0.html

It's $4.26/ft. 6' of black + 6' of red = 12ft x $4.26. $51.12 total. Go cheap, limit your inverter capacity. Spend $51, use it as advertised. Your choice.

2oldman wrote:
2 batteries will be marginal. 4 is better.

+1

Depends on state of charge also. Running the furnace all night and want to wake up to some K-cup coffee may leave you disappointed.

Hi,

It depends on the state of charge of the battery bank. How will you recharge?

Higher voltage beats fat wire.