Notes and Terminology:
DOD – Depth of Depletion – The amount of amperage taken out the battery on a daily basis. If you have a 100Ah battery and you use 50Ah, then your DOD is 50%. Ideally you would want to impact or drain the battery as little as possible as it has a direct impact on the number of cycles you can obtain. By default 50% is common on all lead acid/Gel/AGM type batteries but using a 30% DOD will greatly extend your battery life span. Its different for lithium type batteries where its more common to cycle deeper (think 80/90%) while retaining cycle life. As with all things, checking the spec sheet is a useful guide to obtain information to best cycle life vs depth of depletion.
kWh – Kilowatt Hour – This is the total amount of energy required over a 24 hour period.
Voltage Notes – Voltage selection has a direct implication on overall system efficiency and cost (cable size etc). As a rule of thumb you can work on the following FLEXIBLE rule set:
- 0-3kWh = 12v
- 3-5kWh = 24v
- >5kWh = 48v
Days of Storage – This is self explanatory. By default most solar companies will operate on a single day but for off grid (no utility/eskom) you would generally add a day or two for weather underproduction days.