# Introduction

The problem all gps receivers need electric power to work. Some of them use more than others and some of them have big accumulators to work longtime. For all whose gps receivers don't work as long as desired you can find a solution here, you can mount easily on your bike or mountain bike.

## Calculate the electric power you need

Before you start you have to estimate the electric power you need. The simplest way without any instrument is to find the electric power your accumulator or battery has. Test how many hours the unit works with this power. Ask yourself how many hours you need more than this?

### Example

Your Accu has 1400mAh with 4.5V. And it works 4 hours. You would like to map 3 day's without regarging 4 hours a day. The total power you need the 3 days: 1400mAh / 4 hours * 3 days * 4 hours = 4200 mAh The electrical power you need from a external supllier 1400mAh / 4 hours * 3 days * 4 hours - 1400 mAh = 2800 mAh

If in 4 hours the 2800mAh are used you need a current of 700mA.

All this information you need before you have a look to a solution.

# solutions

You the following solutions 4 solutions to solve this electric power problem:

## bicycle dynamo charger

This solution is specially for cyclist interesting. A lot of bicycles have already a dynamo hub and as most people cycle on day the dynamo have enough power to charge the GPS Unit. You just need to exploit the energy.

### Dynamos

Attention you have to check the output voltage of the dynamo. Some of them have a included voltage limiter. If you need a higher voltage you need to remove the voltage limiter. Here is a description how to remove the voltage limiter for the EDH-2 dynamo: User:Zapfen/EDH-2-Mod

Reviews: Review of some dynamos

## battery pack

In this solution you have a big battery pack you charge at home or in a restaurant. They only thin to do is to chose the right battery pack.