My latest EV project

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Regular Member

Joined: 12/08/2016
Location: Australia
Posts: 99
Posted: 03:16am 20 Sep 2021      

  Davo99 said  
  galderdi said   Am I missing something though 48v at 600ah is 24kwh. That would be massive and $1200 is very cheap.

I wasn't thinking of your requirements so much for your Vehicle as Godoh's for his Home.  You certainly wouldn't want to be carting round  1100Kg of batteries in a sports car! I presumed you would understandably need something more light weight and power dense like a Lipo derivative.  LA is still a very viable Tech for many things, I don't think mobile application's is one of them however!  :0)

Yes, it is cheap for the reserve you get and makes the Commercial lithium battery derivatives look like a joke IHMO.  There seems to be a LOT of deliberate Misinformation about Traction Batteries parroted by the lipo obsessed, which I believe is the apt term for the way many go on.

We have discussed the Fork batteries here for home use  and the reality is they are VERY cost effective with few drawbacks for STATIONARY/ off grid application.
When one considers a power wall is  12Kwh useable and costs $15K and a $1200 (plus ancillaries) 24Kwh pack gives 19Kwh useable, it puts things into perspective.
Double your spend on another Forklift pack and you have 38Kwh  Reserve and you would rarely have to dip below 50% DOD if that ( They are rated to 80% DOD which is often maligned) and they are going to have a Very long life and give a lot of reserve.

If one threw a generous size solar array at the things which would also be cheap as chips now, I'd say people in the typical weather conditions of Oz, (Barring maybe tassie or mountain areas) would rarely have to rely on a generator.

To this end, I'm currently playing with an idea  for running inverters mainly off solar.  It's hard ( and expensive) to find controllers that will supply the kind of amps an inverter will pull.  My idea is to have a Smallish/ low cost Controller and by pass it with heavy loads.

I bought some Battery charger boards off Fleabay. They simply switch on and off at a set voltage parameter. Using a large array and small batteries with a decent  Inverter, The voltage monitor bypasses the controller when the voltage drops, say when the inverter is running.  When the batt voltage comes up after being fed whatever amps the panels can produce ( possibly hundreds) the voltage monitor drops the 500A relay and the charging is all handled at a much lower rate but the controller.

I don't see a need to run through a controller when there is big amps being pulled that can come straight from the panels. There are panels that are suitable for both 24 and 48V setups so it's relatively straight forward. The Chyneese Hybrid Inverter/ Chargers I have been looking at will charge at a rate less than they will supply so create a negative drain on the batteries even if there is sufficient solar input available to power the load. This way would by pass that road block and keep the batteries seeing as little discharge as possible.

Would be interested to hear what sort of batteries you are intending to use and the reasons behind them.  Seem to be different ones coming out much more regularly these days.

Cool, thanks for clarifying. I haven't narrowed my options just yet. I am still tentatively aiming for Mar 2023 on the road so I don't want to purchase the batteries too soon and have them sitting on the shelf all that time.

One option I am considering are 45 x LiFePo4 3.2V 100Ah. Giving about 14kwh.
Based on early measurements they will fit. I do need to redo those measurements as I now have the motor and gearbox in place. They will be about the 100kg I require. The plus side is LiFePo4 are resistant to fire. They to do burn, but not in the same explosive way as many other chemistries. But the down side is they are only rated for 300amp bursts. I can probably go a shade higher because it would only be a second but I will still be struggling to support the 1000amps I spoke about earlier. Having said that I have driven my previous EV set to 500amps output and it was ok but not all that inspiring. By my calculations I would expect 300amps input to support about 573amps output and limit the power to about 51Kw. Not ideal. So I am hoping I can find a better option in the next 12 months.

I think if I can find a combination that would support 400amps in I could squeeze about 750amps out. That would be a good compromise.