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Discussion Starter · #1 · (Edited)
If fast charging stations had there own large bank of batteries, they could "slow charge" their batteries from the grid, but could then "dump charge" from their batteries to a customer's car battery. Ie the jumper-cable concept.

The station batteries would have to be useful for many cycles, and there would have to be some sort of current limiting device to control the charge rate to match the capability of the car battery... They would also have to communicate the "full" DC voltage to match the car... Think heavy DC cables with a spark-controlling on-off switch to initiate the dump.

Ideally if batteries could handle a very high charge rate, then charging would only take a minute or so (comparable to or better than filling your tank with gasoline). Even faster than battery swapping schemes.

Ideas? Has this been done?

What would be the charging times for popular batteries (ie are charge rates even posted - would impulse discharge rates apply)? TS200AH cells have a 20C impulse discharge rate (4 kA) - that would mean charging in 1 hour divided by 20 = 3 minutes!

Garth
 

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Hi Gdirwin

That would work, a couple of years ago I got to the point of writing this up for a patent application - then somebody wrote an article suggesting it! - blowing any patent out of the window!

20C is unlikely - 5C should be doable and would only take 12 minutes

With a 30Kwhr pack 5C is 150Kw, 20C would be 600Kw!!
 

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Discussion Starter · #3 ·
Thanks Duncan - do you know if anyone has tried to build this? Do you recall which post you saw?
 

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Hi again

It was not a post on this site -
I think it was linked to an article on Grid to Car and reverse (G2V)

Some of the advanced AC controllers have feature where the cars battery pack can be used by the power company as a power store when the car owner does not need the capacity

With a few thousand cars with that feature and a power grid becomes enormously more robust and peak power (most expensive) demand drops hugely

I have seen an article about China planning on putting in thousands of recharging stations - the stations were to have their own battery farms - I would bet that they would be used for helping the power grid as well as charging

I have not heard of an actual built charging station using this method - but if I was building a commercial charging station I would include a big battery for that purpose

I have heard of people using a household battery pack (like a solar powered house would need) without the solar panels and saving money by only using night rate power
 

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Thanks Duncan - do you know if anyone has tried to build this? Do you recall which post you saw?
This is well known and even has a name: Level III Charging.

BTW - we've had a number of inquiries over the last couple of years about using a Soliton1 for this application. We tacitly, but unofficially, support this usage, though not in "direct offline" connections (ie - we don't like to see the controller directly connected to the rectified AC mains).

The Soliton1 regulates motor current by default, and because it can also limit output based on RMS motor voltage, it can act as an ad hoc CC/CV charger - just add an inductor to the output terminals. I wouldn't expect it to do this with the finesse of a purpose-built charger, but if you want to rapidly replenish, say, 60-80% of your pack's capacity it should work like a champ.

We have too many backorders to catch up for me to be fooling around with stuff like this right now, but once it gets cleared out I am planning on doing some high current charge/discharge tests of LFP cells/packs and this is how I plan on rapidly cycling them - both charging and discharging as the Soliton1 is capable of operating as a boost converter and not just as a buck. Well, if I can convince Qer to write the code for it, that is... ;)
 

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Remember guys that grid-to-battery and the other way around give cycles to the batteries. Okay, with slow C rates there is muchos cycles in good batteries. But still it might not be a good idea unless you get paid peak energy price for the Wh you sell to the grid...
 
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