Monitoring the charge status of Lead batteries

Prize: Visibility through Acciona Microenergia web and social networks

Status: completed


ACCIONA Microenergia foundation ( is dedicated to bring electricity to isolated and marginalized rural populations in Peru and Mexico using domestic photovoltaic systems.

The challenge

Bringing electricity through conventional power networks to isolated populations in some countries is not economically viable. Acciona Microenergia foundation helps to provide isolated rural electrification using photovoltaic systems. These systems consist on a solar panel (80Wp), a sealed Lead battery (100 Ah) and a charge controller. Through those people get light through LED bulbs and can use low energy home appliances such as 1W radio sets or 6W TVs.

Lead batteries are the most challenging system element due to their cost and short lifespan. Batteries life depends on the number of charge/discharge cycles and the ability to avoid battery charge does not go under 60% of their capacity. Charge controllers read battery voltage as a way to control battery charge. However, voltage is not a reliable method to read actual battery charge after some charge/discharge cycles.

What the client is looking for

Acciona Microenergia Foundation is looking for a reliable, cheap and robust solution to accurately read the actual charge of a Lead battery, its operating regime during a minimum period of one month, and, if possible, at what point of its lifespan it is at that moment.

The objective is to incorporate such solution into these photovoltaic systems to determine the actual battery operating regime, and to establish a strategy to drastically improve the Lead battery’s lifespan.

Please consider that any proposed solution should need minimum battery power to avoid affecting the system available energy (10Wh/day)

The batteries are located inside a wooden box with adequate ventilation that protects it and prevents its manipulation. Ideally, the monitor should be located inside that box, or inside the control cabinet, where the controller is placed.

This is a one-round tournament with the following deliverables:

  • Brief description of the proposed solution.
  • Technical specification:
    • If the solution exists in the market, supplier specification and market price.
    • If the solution is new, target specification including electronic circuits diagram and estimated cost.
  • Solution power consumption.
  • How to fit the solution into the available space and adaptation costs.
  • Some feasibility evidence (e.g. similar solution in other products or countries)

You can find in attachments different documentation such as the current battery and controller specification, photos, dimensions of the control cabinet, etc.

Evaluation criteria

  • Lowest % error for battery charge reading
  • Minimum lifespan cost (manufacturing, adaptation and maintenance)
  • Minimum power consumption
  • Evidence on the robustness of the solution


This is a one-round tournament:

6 weeks to present solutions + 2 week for evaluation

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