i've been thinking that there may be a market for inverters that are above the standard value inverters of 12v, 24v, and 48v. you already have a controller that is capable of handling the higher battery voltages up to 93v and the higher battery voltages would also bring efficiencies better in line for the input to output ratios on the classic. i see guys with large systems having to parallel many strings of batteries for the larger inverter draws at 48v. this would make it more manageable. i know you're looking to have systems growable, but there may still be a market for inverters in the 4kw to 8kw range with higher battery voltages as an input option. how about super sized modules at say 72v or even 84v that are growable with increments of say 2kw? with the max of the classic sitting at 93v you can't double it like the 12-24-48 trend goes.
i know it presents a larger range of models to be engineered, but the higher voltages are best utilized as a starting point for most expanded applications. maybe the forum readers can input their thoughts on higher input voltage inverters that are expandable. i am seeing many inquiries on going higher than 48v for the inverter as people are getting it that the lower voltages aren't always cutting it for high power uses being they have to parallel battery banks to accommodate it and that gets messy at times.
Niel, Midnite makes the Classic 250KS that charges a
120V nominal battery bank up to 150VDC maximum.
There are 120V inverters out there. Exeltech for instance
makes one in the states. There are also some 120VDC inverters
made in Australia and down under.
I don't see us making a 120V DC inverter though in the near
future anyway.
boB
yes, i'm aware of the exeltechs, but they also make standard inverters that are modular too so why are you delving into the modular aspects then? i did forget about the mks model, but i think there may be a market for modular in the higher voltage ranges for you guys. if you want people to go to exeltech then they could do so for all other models as well making it moot for you to go into it at all then with your same argument. up to you though.
With PV prices going the way they are I could definitely see say a 96v inverter. Wire size is now starting to hit us again like it did 20 years ago on 12 volt systems. It is nothing now to see a 24kw inverter system in a normal off grid system. That said it will be tough just do to listings etc.
Ryan
I am ready , I could do a 120 - 150 vdc inverter today , I have designed my own , but would like a off the self one
that does not cost so much , I have 40 120ah batteries right now and will have more , and 6kw of solar , I have been making my turbines at 100 -200v , with the cost of copper , higher volts off sets that cost , I work in a datacenter that runs 400vdc battery banks for UPS
you get more watts out of a turbine at higher volts , less lost
I am a friend of Tom W
Hi ibedonc ! Welcome ! A friend of Tom's is a friend of ours !
What kind of inverter topology did you use on your inverter ?
I have heard of 400V UPS's for server farms and have seen large ones
but don't know what the voltage was. One was an Emerson.
Good to see you here.
boB
I used a sinewave chip to supply the 60hz sine , crystal ref
used a current sink to create a triangle wave and then a op amp to integrate into a PWM , that went to a H-bridge MOSFET using IR mosfet driver chips , pwm freq is 30khz
made my own low pass filter
so no cpu in my design
it works
I have run it off of a bank of 7ah gels with +- 200v
Would you have a trace of your inverter's waveform? Also, what kind of conversion efficiency do you get with it?
I have to find the jpegs this was 3 or 5 years ago and I have not tested the eff yet
i agree with the market for higher voltage inverts but i think guys like Bob have to initiate something like that ,i can safely say there is market in the Caribbean and South America since alternative energy is just catching on and prices are becoming affordable(slowly but surely) .48 volts max limits us here and its a major factor when setting up solar or wind systems.So definitely higher voltages inverters would be really nice.
Quote from: niel on May 31, 2013, 04:21:07 PMi've been thinking that there may be a market for inverters that are above the standard value inverters of 12v, 24v, and 48v. you already have a controller that is capable of handling the higher battery voltages up to 93v and the higher battery voltages would also bring efficiencies better in line for the input to output ratios on the classic.
As an additional benefit, there will soon be a large number of 200-400 volt battery packs available as hybrids and EV's replace their battery packs (or are junked.) Even a Leaf battery that has degraded significantly (say to 50% of its capacity) is still good for 12kwhr, and is designed to be fairly light, well protected and very high power output.
Quote from: billvon on January 06, 2014, 11:20:18 PM
As an additional benefit, there will soon be a large number of 200-400 volt battery packs available as hybrids and EV's replace their battery packs (or are junked.) Even a Leaf battery that has degraded significantly (say to 50% of its capacity) is still good for 12kwhr, and is designed to be fairly light, well protected and very high power output.
Maybe those can be broken down into lower voltage and then paralleled ?
boB
Quote from: boB on January 07, 2014, 01:18:45 AM
Maybe those can be broken down into lower voltage and then paralleled ?
Don't these battery banks have BMS (battery management systems)? If so, you would have to redesign the BMS to support the change in configuration.
--vtMaps
Quote from: vtmaps on January 07, 2014, 03:49:36 AM
Quote from: boB on January 07, 2014, 01:18:45 AM
Maybe those can be broken down into lower voltage and then paralleled ?
Don't these battery banks have BMS (battery management systems)? If so, you would have to redesign the BMS to support the change in configuration.
--vtMaps
Yes and maybe the BMS isn't included ?
I think that if the batteries are worn out, they should be recycled. Probably not worth all the hassle for
depleted batteries ?
boB
>Maybe those can be broken down into lower voltage and then paralleled ?
Perhaps - but a lot of the value of those packs is that they are monolithic, well protected and relatively safe. Disassemble them and you lose those features.
>Don't these battery banks have BMS (battery management systems)? If so, you would have to redesign the BMS to support the change in configuration.
I don't think you'd have to do much. Those batteries are designed to accept charge/discharge at 4C rates so the BMS wouldn't get upset by the lower rates in RE systems. Perhaps you'd have to spoof the CAN bus a bit.
i will say this one more time in hopes all understand. the whole industry needs to quite thinking more watts at low voltage as it does not serve well for any real autonomy. that requires too many ah that make it difficult to configure a battery bank in many cases for longer use times. many are wishing to have the ability to utilize present day batteries with typical capacities, but can't design for long term due to the limitations the industry is putting on them with low battery voltages. more batteries in series allows more useable power capacity to the inverter without having to go with paralleling more than 2 strings of batteries or really expensive uncommon batteries. it isn't always high power inverters that are needed so much as inverters that allow for longer operations by being more compatible with more typical batteries that are available.
for clarity i'm not saying a 120v system is mandatory, but come on as 48v is very limiting for a 4kw or 6kw inverter to have good autonomy from most common type battery setups. the industry follows this dumb rule of thumb of 12v battery for every kw of inverter. it's not the output kw capacity of an inverter so much as the consistent power delivered over 24hrs and longer that needs addressed. that power comes from the batteries. few need a constant 4kw and heaven help them in trying to configure a battery bank to suit at 48v.
with that i'll drop it and probably take boB's advice for my future system.
I would have to agree.
We are offgrid and running a 6kw (continous) Selectronic inverter at 48v with 4kw of PV. At first I was thinking it was way over the top Over time our needs changed and our demand for energy keeps expanding. Electric car, workshop, Air Conditioners, swimming pools pumps. All part of a modern life in 2014. The 6kw continuous and 48v doesn't feel so accommodating now.
We just added a additional 4.2kw of pv to meet the growing energy demands. I have to say while PV prices are very reasonable purchasing the copper wire for big arrays when long cable runs are involved when working with 48v sure became a significant expense and bottle neck of the design of the additional PV. MPPT controllers help but I'm sure there is a point when that high to low DC/DC conversion starts to get inefficient within the controller.
I plan to replace my 63kwh of flooded cells with LIFpo4 lithium cells in about 4 years and I did give higher voltage some consideration perhaps 96v as my two classics could handle that. Just doubling up on the voltage and 1/2 the amps and copper has to be a good thing. I know selectronic make several 120v inverters up to 20,000w continuous but the several thousand dollars tied up in my 6kw 48v selectronic unit is holding be back.
If I was starting from scratch on a large system I don't see why you should limit yourself to 48v when 120v inverters are available at similar cost . Well (10% more expensive) to there same spec 48v versions. But that decision needs to be made on initial design stage or when a product needs replacing.
Kurt
I hope midnite ponders this some. New product R&D these days all seems to be chasing the bigger grid tie market, eg SW, Half Radian with all their grid AC modes. While one way to look at this is that "Off grid will always be a small market" another way is that power decentralisation may be the next big thing. Large grid distributon systems are predicated on big base load nuke and fossil infrastructure. Read any of Herman Scheer's books, and youll conclude, as i did that those days are about done. Mini grids, commercial park, village scale grids and the like is something those old players are scared of for good reason, they are rapidly becoming cost effective.
Mppt is something of a mixed blessing as you say, its great because it allows you wiring flexibility and the potential for wire size reduction, but when i did the math here the controller losses at higher voltages bit harder than the wire losses did. So we all have this mppt tech, and then go and try to minimise the array voltages.
Midnite have several times said that high voltage stuff is hard. I guess thats so, but the grid tie world seems to manage it. The new generation of DC optimisers manages it. Efficiently.
I think its fair to say that theres still a fair bit of room for innovation yet.
Quote from: zoneblue on June 10, 2014, 04:33:21 PM
Midnite have several times said that high voltage stuff is hard. I guess thats so, but the grid tie world seems to manage it. The new generation of DC optimisers manages it. Efficiently.
Well, that's somewhat debatable. Optimizers are great if you have a fair amount of partial shading but if not, they can hurt efficiency because they have to heat up to do their magic. i.e. they have some conduction and switching losses.
Better option for partial shading if possible is to get rid of the shading.
There is definitely room for innovation but it's tough when there are so many compromises to efficiency. One is size and price and another is that all the parts we use have resistance and losses etc. Basically we have to design around defective parts.
boB, you left off the part about '' and it still has to work to some point, and produce usable power''
Some inverters allow load sharing between several inverters (up to 4, or possibly even more with Exeltech) These inverters can feed off different battery banks, so I would argue there is already a safe and modular solution out there that allows the system to scale up. I am personally spooked by high voltage DC, and because of this I am not very keen on having high voltage DC in my car or my house.