Howto convince your partner to let U build an EV

[Adverse Effects]

A suggestion that worked well with hunter gatherer was to design house with drive through kitchen (EV access, no oil drip or fumes) for unloading after shopping. Strangely well received so take note.

lol priceless

[markrmarkr]

Matt,

how about this 1.5KW Inverter on Ebay for $600.   It'll operate with 100 - 550 V DC, which should cover most EV's

The payback time for $600 should be less than a year, though there are other costs....   This is still the only approach that seems to get through to her.

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I actually scored a pile of second hand SLAs from work which I could use with this inverter, and when the car is built use them for a fast charge (at least in theory).   A poor man's CHAdeMO.   I wouldn't put them in the car except for the service battery , but they will be handy for testing etc.

Cheers

Mark

[T1 Terry]

Actually I've already trialled that using 5 lithium ferrous cells in series charged from nom 12v solar panels to recharge 4 cells of a demo pack. The results were outstanding, the limitation was the 1/0 cable used as it would only flow 85 amps but that was enough for proof of concept. I did try 4/0 cable 1 mtr long feeding through a 100amp solid state relay to try charge control etc but even though the heat sink was substantial complete with fans the smoke came out so I think I'll limit it to 1/0 cable in future. No idea how many amps tried to go through the SSR my poor little shunt was only a 200 amp job and well and truly out of it's depths.
One of the side findings was that the 5 cells can handle unregulated 12v nom. panel input as long as the cells remain balanced. I won't elaborate on the cell balancing system we evolved but it works extremely well, the whole system makes MPPT regulator for low voltage extremely inefficient and energy wasteful in comparison.

T1 Terry

[markrmarkr]

Terry,
that's good to hear. I think using the cable gage to limit charging rate is an excellent, almost foolproof way of doing it.   The potential to destroy your pack if your distracted for like 30 seconds, is a real possibility which worries me no end.

I understand the CHAdeMO DC fast charger is a 500V, 120amp, 50KW.   I'm not planning to do anything even close to this level of power, but it's very interesting to think about isn't it.   I can probably get to 500V with my SLAs but 120 may be a bit out of reach for more than a couple of seconds (before some batteries blow-up).

cheers

Mark

[antiscab]

The payback time for $600 should be less than a year, though there are other costs....   This is still the only approach that seems to get through to her.

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I actually scored a pile of second hand SLAs from work which I could use with this inverter, and when the car is built use them for a fast charge (at least in theory).   A poor man's CHAdeMO.

Thats exactly what I'm going to do with my stockpile of Vectrix cells

what other costs are there for the inverter?
Just wire a domestic plug to it and plug it into a power point (don't tell any electricians about it )

an old motor controller with an inductor is a pretty good charge controller, or buy new kelly

failing that, a contactor while matching voltage by how many cells you hook up is the proven method by Rob

Matt

[jonescg]

Matt - plugging the 240 V output from the inverter into the grid...

As non-recommended as this may be, how would you ensure the phase matched? I've often thought it could be done, but no doubt the fancy grid-tie inverters are already doing this to some extent?

[markrmarkr]

Jonescg,
all grid connected inverters take care of this for you.

[coulomb]

all grid connected inverters take care of this for you.

Just to make this crystal clear for all readers: all inverters that are designed as grid interactive inverters take care of this for you. You can't take an inverter from Jaycar (say) that is designed to run your beer fridge and plug it into the mains; the phases and voltages won't be matched, and nothing good will happen. (Plenty bad will happen, though .)

The grid interactive inverters have to do this dance with the mains; they have to monitor it for a minute or so, and the mains has to be within a certain voltage and frequency range. It has to spend this time synchronising phase and amplitude. Once it connects, it has to do some checks to see that the mains is still there, so it doesn't fry some line worker who expects a piece of mains cable to be safe to work on. This is actually harder to do than it sounds. Basically, you have to periodically "push" the mains in voltage or frequency, and see if it moves. If it does, then the grid isn't there, and the inverter has to shut off, and start testing again. Inverters that do this have to be accredited, and this is expensive and time consuming.

[markrmarkr]

Other costs are the charger - I was thinking of a bad-boy with a high voltage cut-out, turned on and off by a timer. Similarly the inverter will need its own timer to turn it on and off, and a low voltage cut-out. Add in a couple of contractors - though the current shouldn't be too high, at least when its working properly. All this stuff costs too.

I was thinking I could size the pack for optimal charging from the bad-boy, which should simplify things a lot.

Of course if I had a controller, justified because I need it for this Battery to grid (B2G) project I'd have a lot of the stuff I'd need for the car project too (batteries and controller). What a coincidence!!! I suppose I could refine the B2G project so that I need a DC2DC somehow, and instrumentation should be easy to justify. But I don't know if I could justify buying a motor or a glider....   hmm.. I'll have to think about that.

Of course the long term goal is the car in my sig bellow, but if I have to get there one step at a time so be it.   I can start with DC lead, and evolve to AC LFP.