Living on mostly 12v and reducing power

Could you elaborate a touch?  Personally, I've converted as many items to DC power as possible, and it really does lighten the inverter load.  I have the following items 100% powered by DC:

• 48v: all LED lighting
• 48v->24v: water pumps
• 48v->12v: laptops, (hacked) computer monitor, speakers, clock, phone chargers
• 48v->12v: tankless propane hot water heater (not an easy project!)

Larger appliances tend to require a lot more power than can feasibly be run at lower voltage DC setups--or to convert them becomes unfeasible/extra costly.  But I've still hacked several...

• GE Profile Advantium 120 convection microwave...ALL logic runs on 12vDC (boy was that a challenge!), 120vAC is only used for the heater coils / magnetron / circulation fan.
• Kenmore Elite French-door fridge: internal lighting and logic already ran on 12v, though from an AC power supply.  Was very easy to disable that and directly wire it to 12v.  Only uses AC for the compressor and defrost heaters (note that I'm not using the icemaker...that'd be another whole story!)
• simple chest freezer: added a 12v thermostat to control the compressor (which runs on 120vAC).

Other appliances such as a washing machine have such a short use cycle that it's easier to just unplug 'em when not in use.

Still have yet to hack that induction cooktop to run off 12vDC when in standby...

Hi Sid,

Anything that requires a transformer / wall wort, those devices were replaced with similar devices that used 12v supplies, then I skip the wall worts.

Low voltage variable color & brightness LED lighting strings I use are 12v powered. The strings are extendable, use a wireless control, so eliminating the wall wart transformer is a big savings.

Multi-cell battery chargers are 12v run.

Anything that heats I moved to gas, to avoid electricity.  

Since I have this 12v infrastructure, if I wanted to use a GS inverter, is there a way to boost my 12v battery system to 24v so I can run my 240v A/C compressor? (I will not need to run other 240v appliances.)

Could I somehow charge a 48v battery bank for a GS inverter from my existing 12v system?

Could I use my non-sine wave 120v inverter from my 12v system to charge/feed the 48v  battery bank?

Thanks!

Will try to get back with you later...

Technically the GS 6k inverter can be configured for 12v, BUT the maximum current (and definitely the surge current) will be considerably limited due to the high amperage.  If the A/C is a mini-split with a variable-speed compressor, it'd probably be alright...but if it's an old-style single-speed compressor, maybe not so much.

What about...converting the battery bank to 24 or 48v (doubling or quadrupling the maximum wattage of your exiting MPPT units, assuming they support the higher voltage)...and using 15-20A step-down converters for 12v appliances?  If you're working with a small RV, a 12v system would probably work fine...but if a larger house, you'd have considerably less voltage drop with 24 or 48v "bus" lines, and point-of-service step-down converters to 12v.

I personally use the "60v->12v" 10/15A step-down converters that can be found on eBay/Amazon/Aliexpress...their no-load current seems to be around 15mA, and I haven't had any issues at all with them.  Pretty amazingly powerful, too.

Pragmatically, I have multiple small 12v UPS’s wired in parallel, able to drive my WAN, LAN, lights, and security system for over 24 hours with no power. When I lose batteries, I have redundancy to wait for batteries to arrive in the mail. It works well.

There was a 66 hour power outage that drove me over the edge, I added a quiet 12v generator with 3000W inverter system in a pinch, to save 2 refrigerators of food and get the heat back on - that met my budget. (One outlet supplied 1500W, with 3000W peak, two outlets would do 3000W continuous with 6000W peak.) When I bought the unit, there was a sign that said “pure sine wave”, but ”sine wave” turned out to only apply to the low end unit. It ran the heat & refrigerators, but very disappointed that it would not recharge my UPS’s when they were running out of capacity. (I knew it could not run my A/C due to split-phase need.)

I have several 24v UPS’s to handle larger compute loads, off-the-shelf external  battery pack on my pure sine wave unit supply my compute needs for ~24 hours during an outage. I originally considered getting a second identical sine wave unit, do a mod to split-phase with another off-the-shelf battery pack, but this would only get me ~2400W running compute equipment for 24 hours. The external battery pack vented & literally melted down (just sitting around charging, no power outage) - a huge disappointment since I was depending on off-the-shelf equipment to give me a degree of reliability & safety. (Even this path would not get my A/C running… although I contemplates mods to add 2x more and sync up the split-phase to eventually get there… leaving the gap of charging the 24v batteries when we had no power for long periods of time.)

A 240v split phase generators are so noisy and noise was a factor for my approach. (Everyone hears a neighbor’s 240v generator, no one hears my 12v DC generator.)

I go through this explanation to illustrate that reconfiguring this 12v system is less feasible, I am not married to extending my 24v system after the melt-down (with it’s gaps), but there are 12v components that are helpful & proven reliable.

I am thinking about effectively replacing my 12v 3000W inverter and reducing big battery dependency on 24v UPS’s with a GS (more off-the-shelf, more capacity.)

Over time, I plan to add solar panels, but that is not a priority.

I understand the input current limitations if a GS is configured for 12v. I have massive cables on my [non sine wave, non split phase] 3000 Watt inverter.

That being said, adding a battery system to the GS, backed with capacity from my 12v system seems possible. I was thinking a dozen of these (ignore the W, the limiting factor is 40A 12v input or 480W each):

https://www.ebay.com/itm/1800W-40A-DC-DC-Converter-Step-Up-Buck-Boost-Power-Adjustable-Constant-Current-/383901055938

Since this is only needed during long power outages (~2x a year), I am considering temporarily paralleling some off the shelf EGO 56v batteries (used weekly in my yard, kept charged all the time.) I may commission a friend to build higher capacity packs using old 56v EGO BMS’s (14s of SPIM08HP batteries) while adding a 3D print an extended top case. I figure if the smaller batteries can power my chain saw, a half dozen bigger batteries can handle surge capacity of the house. (I do not expect the GS to charge the batteries in this configuration, but the batteries to supply the load spike when cranking up the A/C compressor.)

This offers some wonderful dual use capabilities, easy modular replacement, and fast replacement with a trip to Lowe’s during a crisis.

I never want to have to deal with ripping apart a melted down battery pack again… I resorted to a hammer & crow bar to open up the case, to get access to the batteries, so they could be appropriately recycled. Destroyed my external UPS battery case, what a shame.

This being said, since you brought it up, I am also wondering how much loss there would be on the top end of the GS 6K split phase pure sine wave inverter if configured to 12v. If still supported, my compressor is rated at 19.5 RLA and fan rated at 1.3 FLA. See photo. Do you think it would work? It is a new unit, just 1.5 years old.

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Well, if you've seen the latest YT videos Sean's posted...for comparison, the A/C unit that's giving us such grief with the 12kw GS prototype unit...is rated at 114 LRA (the important number, this indicates the maximum possible surge current).  Sean's A/C is also fairly new: it was brand new when he moved into his current house 2 years ago.

LRA = locked rotor amps.  The nameplate of your A/C is 130A, which is 16A more than the current A/C we can't seem to get started.  A GS 6kw @ 48v can't start it (doesn't blow up, it just can't start the compressor)...but technically, the 6kw GS is rated for 50A surge...with 130A being nearly 3x the GS 6's surge rating.  (It manages to start Sean's 77LRA smaller A/C unit without too much difficulty, which was rather surprising.)

Keep in mind: we're talking an order of many times' difference in the power requirements of a cordless chainsaw vs trying to start a 130LRA A/C unit.  A chainsaw might run 400-600W tops.  To start that A/C unit?  31,200W...or roughly 50 times the estimated power requirements of the chainsaw.

Hi Sid,

My question was just before the gs12 test. I was hoping for a good result on the gs12.

The 56v batteries I am targeting come in 14s and 1p, 2p, and 3p configurations… each parallel bank capable of 20Ah sustained discharge rate (individual cell rating my mfg), BMS for charging only, no BMS on output terminals, so much higher peak current is possible.

I think I can get enough straight chemical capacity to handle the LRA. I figured to get a soft-start module, anyway.

I was thinking about your control board and telemetry. Dropped a note on YouTube.
 

I didn't quite understand what you were getting at on the YT comment.  Could you elaborate further?

I'm not quitting on the 12kw.  Have 3 things to try...should be able to get it working one way or another!  For one, FET crosstalk/drive issues are the bulk of it...need to figure out how to get the best drive signals on the gate without punching the gates out with overvoltage...AND limit the maximum throttle.  I recall that @ben managed to explosively blow out a set of FETs with no load on the inverter...by connecting the AC output wires up wrong.  That tells me that these high-wattage transformers won't accept a square wave input...they'll basically dead-short the battery and blow the FETs out.  So I need to determine what a safe maximum throttle is...and go 20% less than that.

Then that big A/C should roar to life with nary a whimper...

It seems like with all the money spent with boost converters and cordless tool batteries and blow ups and melt downs that you could have just bought some batteries to make a  36 or 48 volt system. A golf cart place near me has a special offer for six Crown 205 Ah 6 V batteries for $655, which would get you 36 V. Or six Crown 165 Ah 8 V batteries for $815, which would be 48 V.

Don't get me wrong. I'm all about cobbling things together, but I don't have any critical needs. If I did, I'd bite the bullet and get a good set of batteries and a charge controller as the foundation of my system, and then cobble on top of that.

It seems like with all the money spent with boost converters and cordless tool batteries and blow ups and melt downs that you could have just bought some batteries to make a  36 or 48 volt system

I  started  with  12v system  3 years ago  because 12v  battery  are  easy to buy  .  I  try  boost converters from China   to go to  48v   from 12v battery .   5  boost  converters caught   fire  before  I  finally  get   4 to  work at  48v .  Now I use ebike chargers with  regulator .   

I'm not quitting on the 12kw.  Have 3 things to try...should be able to get it working one way or another!  For one, FET crosstalk/drive issues are the bulk of it...need to figure out how to get the best drive signals on the gate without punching the gates out with overvoltage   Then that big A/C should roar to life with nary a whimper

I  know  your 12kw GS  inverter will run Sean  4 ton AC  with no problem  .     My   15kw  PS  inverter  run my  4ton heat pump  with no problem  but it  is using more power  than I first   think .  My battery  run down  in  2 hours .  I   have  picture  of  LRA  117   which is 4 times  more than I   thought  the  surge of  28000 watts  should be  .   That is why  the ASL9  transformer  get so hot  and  the  mosfet  135 F degree .   L1 and L2 is balanced and    is directly wire  with  breaker  to  heatpump .    Heat  pump may not start if  L1  N  L2  to transfer switch and not be balanced  .   

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Nice, very good to know.  That means we have zero excuse here on GS inverters 😉

Can you provide a photo of the transformer model tag?  I seriously doubt it is an ASL9; for a 15KW PJ, it will likely be an ASL6.5, one step larger than the core used in the GS 6.

Should be somewhere over 120A on your batteries.

Should be somewhere over 120A on your batteries

Yes  120a  to 180a   I  start  at 60 v  and  run down to 50 v because of square wave  or  when transformer  temp go to  165 degree F .    One third  of battery on  charger  and one third on standby and one third  being use .   I let the  transformer  cool  for 2 hours  and then use the standby battery  and  recharge  the first  group .