Berekening accukosten

Q&A and troubleshooting
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1

als je bij instellingen van DESS de i aanklikt bij de berekening van de accu kosten komt volgende formule: aantal cycli/(prijs accu*capaciteit)

dat geeft als eenheid geen Euro/kWu;

dit zou moeten zijn: prijs accu/ (aantal cycli* capaciteit) om tot de juiste eenheid te komen en dus het correcte resultaat

2

Hi Jan, even though I’m dutch as well, we like to talk English here. Welcome to the forum by the way.
To answer your question, the system needs to know the cost of the battery in Euros per cycled kWh, so the €/kWh is the correct unit of account. How to calculate that is subject to much discussion but leaving all kinds of economical effects (cost of money for instance) out of the equation.
The simplest formula would take the maximum number of cycles before cycling wear degradation requires replacement of the battery, say 2000 (full) cycles (unit: none). Then multiply that by the energy capacity per cycle (unit: kWh) to get the lifetime energy cycling capacity (still kWh). Dividing the up-front procurement costs (unit: €) by that lifetime cycling capacity (unit: kWh) does indeed give you €/kWh.
Where this gets ‘debatable’ is when people take manufacturers cycling guarantees of thousands of cycles, say 6000+, serious while conveniently ignoring:

  • The fact that that would require running a complete full cycle per day, every day, week, month and year for almost 20 years.
  • The cost of money of that up-front investment, including opportunity costs not being able to double spend your hard earned c#sh
  • Technological advancement in battery technology accelerating economic write offs of the batteries in current operation
  • Labour
  • Risks
  • Etcetera

For all practical purposes, if you don’t value (instant write off) your initial investment, 5€ct/kWh is a reasonable number, 10€ct/kWh for recent low cost / DIY Li-FePO4 battery seems reasonable to me. And more even for professional / turn-key / commercial / Victron compatible lithium batteries.

Oddly enough, old school wet lead-acid (when well managed and maintained), you know the lift-fork kind, are still hard to beat from an economics perspective.

3

so 2000 euro /16kWh/6000cycles gives 0.0208 euro/cycle

4 
2000 / ( 16*6000 ) = 0.0208333333

Assuming you meant €/kWh cycle cost (multiply by 16kWh to get cost per (full) cycle
theoretically yes, if you have 20 to 30 years time, no interest, no inflation, no calander aging, no opportunity cost, no maintenace, no nothing basically.

More realistically, you limit economic life to a maximum of five years, like any business writeoff, keep 20% restvalue. That gives €1600 writeoff. Then assume at most 50% cycle average per day, which already requires regular full cycle days to compensate for no cycle days. So that is 5 year * 365 days * 50% * 16 kWh

5 * 365 * 0.5 * 16 = 14600 kWh

And

1600 / 14600 = 0.109589 €/kWh

Pretty close to that €0.10/kWh I mentioned above. Any other calculation only serves to hide the hobby from the boss.

5

Hi @jan59

It turns out this is an error in the Dutch translation. When you view the page with the language set as English, it will show the formula battery price / (battery cycle life * battery capacity), which is indeed the correct formula.

With kind regards,
Thiemo van Engelen