Installing a DC-DC converter for emergency power

[bob2.0]

Perhaps it is the same on all such bikes.

But I can see how adding this feature would work on my bike.

I have a grid tied box that can convert solar panels (up to 55V) into mains power.

I probably would not want to connect it directly to the battery anyway.

By doing this, I can then power the house.

I get cheap power at night, and use a few kWh in the day.

How much life would I take out of the battery by cycling it through 4kWh every day? It would save me a few pounds a week, say £200 a year.

[jeff-jordan]

So you would like to use the battery of your E-Odin as power source to support the mains of your home grid during daytime, while charging it with cheaper power at night.

Now a few thoughts about that .

4kWh would be approx. 0.5 charge cycles. The E-Odin was advertised with about 800 (sometimes 1000, sometimes "up to" 1500 times) charge cycles for the battery (which means that after 800 cycles, the capacity would have dropped down to 80%, a typical value for this kind of battery technology Li-NMC).
So 4kWh every day would last 1600 days to reach that point.
Or 1 year of doing so will cost you 22.8% of the batteries nominal lifetime.

Take in account that the battery charger and the grid converter have an efficiency each.
Let's assume 90%. That means your over all efficiency would be 81%, 19% will be lost.
In this case, you only gain something if the power at night is more than 19% cheaper than during daytime.

[guewer]

So etwas würde sich - wenn überhaupt - eigentlich nur mit LiFePo-Akkus rechnen. Mit Li-Ion Akkus, vor allem extrem teuere "Spezialanfertigungen", wie sie in Elektrorollern zum Einsatz kommen, wo dann 1 kWh Speicherkapazität ein vielfaches des Preises für LiFePo-Akkus kosten, wird sich das nie und nimmer rechnen.

Spätestens wenn der Elektroroller-Akku stark degradiert, wird man merken, welche Fehlentscheidung man damit getroffen hat.

[bob2.0]

I think NMC should be good for a few thousand cycles, but who can say.

If you get 800 cycles of (say) 100 km out of a battery that costs Euro 3,000 to replace, then that is 300,000c / 100000 miles = 3c per km. Also add in another 3c per km for the electricity itself.

I mean, 100,000 km is plenty for the life of such a bike, so I suppose it is enough, and then to recycle it.

But an equivalent petrol, like a Honda 125F that does 120mpg, ~2 litre/100km, is also about 6c / km. The Honda is a far more sensible purchase. It has to be a hobby. It is not financially sensible.

Anyway, the thought to cycle daily was a secondary idea. What I was thinking was about emergency power.

But if there is a power cut, would it make more sense to keep the charge in your bike incase you have to go somewhere?

I think, if there is a power cut, I'll just go to bed until it is over.

[jeff-jordan]

"a few thousand" cycles would be very optimistic for Li-NMC. 800 - 1500 is more realistic.

It's not the best use case for a Li-NMC battery.
I think we all agree that LiFePO4 would be far better (approx. 4000 - 6000 charge cycles).

But it is, lets say, an emergency use case.