What Size Inverter?

[BlueSovereign]

Originally Posted by GordMay

I trust you mean 70 square mm cable, or 138,100 circular mils (a little larger than #2/0 AWG @ 133100 cm); which should allow you to mount the 2kW inverter about 10 feet from the batteries.

Good question GM!

Candidly, as I am from "up north", and I'm "down under", I suspect not all is created equal, which is what in part concerns me. The other part is I don't understand as yet is your wire size chart and the difference between that and "circular mills" table which I could not find. Where is it?

Wiring size down here goes from 50 mill, to 70 mill, with the next size 90 mill, and I've been told 70 mill will be OK .... but I want to understand why!

What I can tell you is the distance is more like 14 feet, not 10, and there is nothing I can do about that!

The newer versions of a B48s have primarily 24v systems and I certainly now understand why.

I know that 2500watts @ 12v DC = ~200 amps, what I must be able to carry. I also know that combining the 100amp/2000watt (or 2500watt) charger/inverter with a matching 100amp charger again dictates I must be able to carry 200amps.

I also know that my ac system is 230 not 110!

Beyond that I'm currently not adequately familiar with what I need to know and why I need to know it .... and that worries me!

That's why I started this thread ... knowing I was probably only exposing the tip of the ice-berg .... in terms of my own ignorance!

[Zanshin]

Try looking at Line Losses Calculator - Storage to calculate your line losses and get a recommendation for wire sizing (in mm). I was amazed at how much loss I got using my original, undersized, wires!

[BlueSovereign]

Originally Posted by Zanshin

Try looking at Line Losses Calculator - Storage to calculate your line losses and get a recommendation for wire sizing (in mm). I was amazed at how much loss I got using my original, undersized, wires!

Just plugged in numbers based on a max of 14v charging (think that would be about right) and a 70mill wire JUST works (@3.11% loss)

Measured the diameter of the piece of 70 mill I have and it measures ~ 9.5diameter listed in the calculation.

Thanks for this!

Now what about the inverter related line issues????

[Badsanta]

Dont forget that you have to measure the wire both ways. So if your appliance is 2 meters from your battery you have to figure it at 4 meters of wire. Figure the wire size from battery to appliance and back to complete the circuit. You will need a larger wire if you only figured it one way.

[CharlieJ]

Blue Sovereign-I would recommend running 103 sq mm (AWG 4/0; 205,500 CM) cable since you are going to be stressing the I/C very hard. By the way, the Xantrex MS2000 I/C Installation Manual is in agreement with me. Don't scrimp on the Class T fuse or an isolation switch in the B+ conductor. And remember to install a case ground. ABYC Standards allow the case ground to be one cable size smaller than the DC conductors.

[BlueSovereign]

Originally Posted by Badsanta

Dont forget that you have to measure the wire both ways. So if your appliance is 2 meters from your battery you have to figure it at 4 meters of wire. Figure the wire size from battery to appliance and back to complete the circuit. You will need a larger wire if you only figured it one way.

I may be crazy but I'm not stupid!

I knew that was necessary, but thanks anyway for the advice.

[BlueSovereign]

Originally Posted by CharlieJ

Blue Sovereign-I would recommend running 103 sq mm (AWG 4/0; 205,500 CM) cable since you are going to be stressing the I/C very hard. By the way, the Xantrex MS2000 I/C Installation Manual is in agreement with me. Don't scrimp on the Class T fuse or an isolation switch in the B+ conductor. And remember to install a case ground. ABYC Standards allow the case ground to be one cable size smaller than the DC conductors.

Thanks for the advice. Could you convert that into the wire sizing for me using mm's???: Line Losses Calculator - Storage to calculate your line losses and get a recommendation for wire sizing (in mm).

I've calculated I can just get away with 70mm to limit voltage loss to ~3%.

However I am tempted to explore installing 90mm (the next size up), if it can be shown or explained to me how much better that would be (which will also require two costly battery boxes just made to be modified to handle the larger diameter).

I won't be doing the installing but will be looking over the shoulder of the marine electrician and will be sharing your above advice with him.

[GordMay]

Originally Posted by Blue Sovereign

... I've calculated I can just get away with 70mm to limit voltage loss to ~3%. However I am tempted to explore installing 90mm if it can be shown or explained to me how much better that would be ...

According to the linked Line Losses Calculator:
The next arger 95mm (?) wire size would reduce your Voltage Drop from 3% (/w 70mm) to only 2.5%, and would reduce your Line Losses (Power) from 2.42% to only 1.75% (a 30% improvement).

I'm not an IEC (metric) guy, so not familiar with a direct calculations.

70mm2 = 10.9mm∅ = > 2/0 ➛ Power Loss = 2.42%
95mm2 = 12.8mm∅= > 3/0 ➛ Power Loss = 1.75%

[BlueSovereign]

Originally Posted by GordMay

According to the linked Line Losses Calculator:
The next arger 95mm (?) wire size would reduce your Voltage Drop from 3% (/w 70mm) to only 2.5%, and would reduce your Line Losses (Power) from 2.42% to only 1.75% (a 30% improvement).

I'm not an IEC (metric) guy, so not familiar with a direct calculations.

70mm2 = 10.9mm∅ = > 2/0 ➛ Power Loss = 2.42%
95mm2 = 12.8mm∅= > 3/0 ➛ Power Loss = 1.75%

Thanks for this GM.

BTW, you are corect, the next size up is 95mm not 90mm (I just learned that yesterday).

Candidly, I do not entirely understand the significance of the figures you mentioned (i.e. Voltage Drop to 2.5%, and Power Loss to 1.75%).

Could you share a real world example involving the system I've described and how that would impact more positively my using it?

Gracias in advance

[BlueSovereign]

An addendum to this thread which i am very interested in learn about.

What precipitated my original query (2000 watt vs. 2500 watt inverter)was my desire to use my "still plenty of life in it" home kettle on my yacht, which draws the standard electric kettle down here of 2000 - 2200 watts.

What I've learn from this thread, amongst other things,is that there are "power spikes" (?) when you start things up (like a microwave, or kettle).

The reason for an inverter was to eliminate the need for starting up the Genset simply to micro something or to heat some water for tea, thus saving my limited supply of propane gas for mainly cooking.

Given I just learned the incremental cost for an extra 500 watts larger inverter is rediculousy high, I investigated a finding a new kettle.

I found one that ranges betwen 1650 - 1800 watts. Is that margin of 200 watts sufficient to avoid my frying something in my electrical system if I go with just the 2000 watt inverter?

[GordMay]

BlueSovereign:
The cheaper 2000 W inverter should be more than adequate to start and run a 1000W Microwave Oven.
Buy the new kettle, not larger than 1800 Watt*.

* Ni-Chrome resistance heating elements have less than 110% (for 1-3 seconds) cold start inrush current, due to the element’s lower resistance when at room temperature vs hot operating temp. Current varies inversely /w resistance (I = E/R).
Hence 1800W x 1.10 = 200W max. inrush*

I presume the 2000W (continuous) inverter also has a surge rating, which will provide an additional buffer.

[GordMay]

Originally Posted by BS

... Candidly, I do not entirely understand the significance of the figures you mentioned (i.e. Voltage Drop to 2.5%, and Power Loss to 1.75%).
Could you share a real world example involving the system I've described and how that would impact more positively my using it?...

The difference represents about 35 Watt/Hours consumption in use at 2000W.
The Voltage Drop, attributable to wire size, will consume nearly 3 Amps of 12V Battery power, or about 1/6 Amp of available inverter output power (230VAC).
Low Voltage can have other deleterious affects on electrical equipment.

[Rick]

Even if you overload the inverter there is more than one level of internal protection to prevent "burning" anything up. For example, if a peak start-up current is demanded, like when starting a compressor motor, that the inverter will not deliver (like if battery volage at the input is too low) you will hear a hum and then an overload condition will shut down the unit. Reset may be automatic or manual depending on the model inverter as long as the load is removed.

[BlueSovereign]

Originally Posted by GordMay

The difference represents about 35 Watt/Hours consumption in use at 2000W.
The Voltage Drop, attributable to wire size, will consume nearly 3 Amps of 12V Battery power, or about 1/6 Amp of available inverter output power (230VAC).
Low Voltage can have other deleterious affects on electrical equipment.

GM, I must be having a "Blond Moment", as I still don't understand how you arrived at the above numbers in your post I've quoted.

Could you be kind enough to detail the math a bit more please. Again, while I have mechanical and the like appitudes, this (electrical stuff) is an area I seem to not have an appitude for which takes a while for me to assimilate it (though I've learned a hell of a lot thanks to the likes of you and others through your responses to my queries).