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I'm trying to do the math of what size of a charger I should purchase.

The battery specs say they can recharge at 1.5C when fast charging. I will be recharging at Level 2 EVSEs and Level 1 EVSEs. However, I would like to know how fast it will recharge because if it can recharge in under 3 hours, that is something. Recharging in 6 or 9 hours doesn't matter because I wouldn't be sitting there waiting in that case.

So, going from the 40A circuit breaker in the houses fuse panel with two hot legs putting out 240-250V AC it plugs into the EVSE. I don't have a level 2 EVSE installed yet, but there are different models out there with different amp ratings. And the public one 35 miles away from my house has this label saying that it's max output is 30A.


On the car, the Elcon PFC4000 and PFC6000 chargers say their max input is 30A AC. Which correlates with the public 30A AC output rating. And that means that at 240V * 30A = 7200 Watts would be the theoretical max. That is unless I wanted to get way to complicated and break the pack in half or into thirds in order to use multiple chargers to reduce the charging time when there are two or more open EVSEs.

Now the harder decisions to make. What size and limitations are there when using the 4kW (4000 Watts) or 6kW(6000 Watts) models. And what amperage do I recharge my pack at? I have 48 cells broken up into sets of 16. Each cell is at (3.75 x 2 = 7.5V DC nominal), but should be charged to 4.1V x2 x 16 = 131V DC.

The 4kW is available in a 168 model that can do (120Vmin*-170VDCmax, 30A max) which would be set at 131V x 30A = 3930 Watts (under the 4000 Watts limit)

*Different sources say different things. One says the minimum is 120V, the other says the minimum is 145V. The other model that I would consider is the 145 model that can do 131Vmin-145Vmax they say at 32A max. (131V x 30.5A = 4000W limit)

The 6kW is available in a 168 and 145 models that can do (131V x 45.8A = 6000W or 131V x 45A = 5895 Watts)

Now I don't care about the hundred watts or so, but I do care about having the minimum voltage be settable to the 131V that I require. Does anyone here know if the 168 one can be set lower?

The next question is, can the batteries handle 45.8A at 131.2V DC? The battery pack will have a capacity of 180Ah or so. So, it could recharge 45.8 Ah in one hour of charging with the 6000W charger or 30.5 Ah with the 4000W model. But that is a (45.8A/180Ah = 0.25C and 30.5A/180Ah = 0.17C recharge rate respectively if I did the math right. It isn't Ah/A is it?) That is well under the 1.5C max rate that these battery cells are spec'd at.

And assuming that I will leave 20% capacity in the batteries that will mean that there will be 144 Ah to replace at 131.2V = 18.9 kWh (a day and a half of my solar panel generation by the way). 144Ah/45.8A = 3 hours. 144Ah/30.5A = 4 hours and 45 minutes to recharge.

Now, I'm not planning to routinely take this truck long distances, but there are some cases where I would need to use public EVSEs to make it somewhere. And if I try to go 300 or 400 miles on a special occasion, I need to know what the trip time would be. It would be nice to be able to have two 6000 Watt chargers running at the same time when there are two EVSEs at the public stations on separate circuits. If you could wire it in such a way to break the pack in two (90 Ah, 72Ah drained max) and still charge it at 45.8A, it would only take about an hour and a half and charge at a 0.67 C rate...

I don't know what the range would be yet until I calculate how many watt/hours per mile it will take. And how the regen, lightweight parts, and efficient driving techniques will work out to increase that range. If the range is around 100 miles, taking 6 hours to recharge the pack twice to get 300 miles away wouldn't be that crazy. It would make a 5 hour trip into an 11 hour one. More likely, the 60 mile trip to the next town over would be able to be done much easier by stopping for half an hour at a charger there and a little over an hour on the way back to charge up with the 6000W charger. Then finish charging at home.
 

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With Lithium batteries the limitation is usually the charger. You are saying that the batteries are 180 AH and they can be charged at a max of 1.5C. This means to charge them in the shortest possible time your charger must be able to do 270 amps. At a max voltage of 131 volts this means the charger will need to be able to do 35kw. That happens to also be about the limit on typical home electrical service in the USA after you account for efficiency losses.

At a 1.5 C rate you would expect to see a full charge in around 3/4 of an hour.

With your 24kwh pack and a 6kw charger expect a full charge to take something more than 4 hours, probably closer to 5 hours.
 
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