How to integrate batter/charger into portable unit

[showcaser]

Hello,

I am developing a portable data acquisition system and am looking for advice on integrating a battery/charger. The unit consists of a Laptop with DAQ, a variety of sensors, a 12volt fan all in a custom carrying case. The sensors are powered via the laptop. I have 2 ways of going at the moment.

1) A small capacity battery just to power the fan (say 1Ah-12volt) the limiting factor being the laptops battery runtime.

2) If feasible a larger battery to power both the fan and act as a supplement to the laptop (3+Ah).

The system would be used daily and charged overnight so the batteries would need to be able to have a good number of charge/discharge cycles.

My question is what kind of battery suits best this application and how would I go about integrating a charger? I don`t want the user to have to take batteries in and out. They should just be able to plug the unit into the wall for charging.

Thanks for any advice that can be given.

Showcaser

 

[andrewg85]

Hey Showcaser, the best way to go about it would be to put a connector going into the carry case for a battery charger, that way the carry case can just be plugged into the charger overnight.
Modifying the charger - you can use a quick connector (such as one off a DC plugpack). Just take the clamps off the charger and put the connector on instead and watch the + / - connections as reversal can kill the appliances. These can be bought from most electronics stores (Jaycar, Dick Smith) and can be easily mounted. You can get away with using just a $20 charger from the shops.
With the batteries, it is not a good idea to run them completely flat all the time by using 3Ah batteries as it shortens their potential lifespan.
This is common to Sealed lead acid (SLA) and lead acid batteries that they don't like being flat.

I would recommend one 7Ah battery or two smaller batteries in paralell (if there is insufficient space for the 7Ah) to power the laptop and fan. I hope this has been of good use to you.
Andrew