Inverter: doubts...doubts...doubts...

[Username25]

Hi all,

I'm in process of choosing inverter and have many doubts which way to go... We have 300W inverter (Mastervolt AC Master) and it worked just fine for small electronics. Plus there are 2 step-up converters 12->19V (laptop, TV, etc.), 12->24V (Wi-Fi antenna, vacuum cleaner, etc.). Our needs are very small; we do not use any power hungry appliances.

Now got Daewoo Mini wall mounted washing machine (3kg), so was thinking of getting just a bit more powerful inverter, 500W would certainly do the job. For cold 29 minute cycle it uses 8A to operate with water and clothes; centrifuge at most 13A and full wash cycle requires 4.5Ah, so even our 300W inverter would be fine. We had no plan to use it in any other mode as hot element pulls approx. 140A for 80°C water heating and 55 minute cycle uses 58Ah, but you never know... Moreover, in some distant future, maybe, getting rid of gas and converting to induction cook top… haunting idea. Our current systems is 360Ah lithium battery (12V) and 230W of solar, so probably a bit too small for using induction cook top…

So first, it was 1500W inverter on the buy list, then 2000W and it ended up with 2500W (something like no more upgrades for life), then back to minimalism and finally ‘f**** I don't know’… So any thoughts, ideas, suggestions are very much welcome.

On a technical side…
-> AC Master 12/1500 (230 V)
Efficiency 93% / No-load power consumption: (ON mode) <1.8A / (energy saving mode) <0.1A
https://www.mastervolt.com/products/...-12-1500-230-v

-> AC Master 12/2500 (230 V)
Efficiency 88% / No-load power consumption: (ON mode) <3.6A / (energy saving mode) <1.1A +++ hard wired, integrated AC transfer system
https://www.mastervolt.com/products/...-12-2500-230-v

[Paul L]

Originally Posted by Username25

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Now got Daewoo Mini wall mounted washing machine (3kg), so was thinking of getting just a bit more powerful inverter, 500W would certainly do the job. For cold 29 minute cycle it uses 8A to operate with water and clothes; centrifuge at most 13A and full wash cycle requires 4.5Ah, so even our 300W inverter would be fine.....

Well you don't say what voltage the washer is running at. If it's 120v then 13amps is 1560watts. If it's 230v then 13amps is 2990watts. Plus you need extra head room for motor startup loads.
Note that 3000 watts at 12v is a 250a draw from your bank.

[Unity]

And keep in mind not only the massive power draw from your battery bank, but also the wire size required. In our case, we have a 3000 watt inverter (short peak loads at 4000 watts possible) and I ended up running wire larger than 4/0 (it is 373 kcmil, called DLO or Diesel Locomotive wire which is tinned and flexible but massive) in order to handle the load from batteries, to fuse, to on/off switch and to inverter (remember, easy connection adds resistance).

4000 watts at 12v is 333 amps! That's a lot of current, but we have 1200 ah house bank, backed by 8 solar panels, 2 wind generators, and an 11kw genset (that auto-starts when the inverter AC draw exceeds 18 amps). It gets complicated (and expensive) as power draw goes up...

[Username25]

Originally Posted by Unity

And keep in mind not only the massive power draw from your battery bank, but also the wire size required. In our case, we have a 3000 watt inverter (short peak loads at 4000 watts possible) and I ended up running wire larger than 4/0 (it is 373 kcmil, called DLO or Diesel Locomotive wire which is tinned and flexible but massive) in order to handle the load from batteries, to fuse, to on/off switch and to inverter (remember, easy connection adds resistance).

4000 watts at 12v is 333 amps! That's a lot of current, but we have 1200 ah house bank, backed by 8 solar panels, 2 wind generators, and an 11kw genset (that auto-starts when the inverter AC draw exceeds 18 amps). It gets complicated (and expensive) as power draw goes up...

I'm aware of wire size... we already have 50 mm² (1/0 AWG), so according to the manual it would be minimum wire size for 1500W (distance max. 3 meters). For 2500W I would have to upgrade to minimum 95 mm² (3/0 AWG). My hydraulic crimper max. is 70 mm², but probably I could use 2x 50 mm² (1/0 AWG) parallel wires.

[Username25]

Originally Posted by Paul L

Well you don't say what voltage the washer is running at. If it's 120v then 13amps is 1560watts. If it's 230v then 13amps is 2990watts. Plus you need extra head room for motor startup loads. Note that 3000 watts at 12v is a 250a draw from your bank.

Washing machine is running 230V and has inverter motor (service manual info: 36189L8000, DWD200BL, DC 310V, 125W). Have no idea about head room for it's start-up loads. Amps usage by washing machine were measure at DC (12V) end.

[Singularity]

Originally Posted by Unity

It gets complicated (and expensive) as power draw goes up...

From my perspective, yes and no.

The famous rocker said that money can't buy you happiness, but it can buy you a yacht to pull up right beside happiness. Having too much power on board to ne is like having too much wealth while you are cruising.

If/when one has a surplus of power, adding extra refrigeration and cooling becomes much more simple (i.e. less complicated). The less you have to think about power...the more it exists in the background...the easier life is.

I purchased a larger Magnum inverter based on the buy once, cry once philosophy. I think it cost $1600 (before the a la carte add ons). As best I can tell, it has sufficient capacity to run absolutely anything I could want to run on the boat (scuba compressor, cabin air con, refers).

Given the hassle (opportunity!) of rewiring with a new inverter/charger, it didn't make sense to save a few hundred dollars instead of installing the last inverter the boat should ever need.

Thread creep:
To me the doubt in the inverter-power-generator axis is regarding the merits (or lack thereof) of an AC generator. My larger inverter charger only dumps I think 125 amps (12v) to the LFP from the 6kw NL generator. At the moment I think I'd prefer something like a MyTGen with a water maker pump +/- freezer plate pump. Running the smaller MyTGen an hour a day could give closer to 200 amps, plus 30 gallons of water and colder freeze plates.

I mention to dino-generation angle as it relates to the nature of the power system in which you're placing the inverter, which also may change inverter desires.

[Unity]

Originally Posted by Username25

I'm aware of wire size... we already have 50 mm² (1/0 AWG), so according to the manual it would be minimum wire size for 1500W (distance max. 3 meters). For 2500W I would have to upgrade to minimum 95 mm² (3/0 AWG). My hydraulic crimper max. is 70 mm², but probably I could use 2x 50 mm² (1/0 AWG) parallel wires.

If you need a bigger hydraulic crimper, check this out: https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1. $45 and works like a charm even on my 373 mm². I've done countless crimps now with it. Doesn't do smaller crimps, but sounds like you've got that covered. Also check out ebay when looking for the crimps themselves - I found surplus large crimps that were a fraction of retail.

[Username25]

Originally Posted by Unity

If you need a bigger hydraulic crimper, check this out: https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1. $45 and works like a charm even on my 373 mm². I've done countless crimps now with it. Doesn't do smaller crimps, but sounds like you've got that covered. Also check out ebay when looking for the crimps themselves - I found surplus large crimps that were a fraction of retail.

Thanks. Just got brand new very similar to yours from Aliexpress, but wire size is 4-70 mm². At the time I thought oh 70 mm² will be through the roof...