Battery Selection Problem

[trebor8255]

Hi,

I am currently building a small project which will have the functionality of an emergency light. The Emergency light will consist of a single white LED ( 20mA - 40mA ). I was looking for button type batteries which are also rechargeable. Since size is a problem, I am confused whether I should go for NiMH or LI-ION.

I know that LI-ION is a bit complicated for recharging due to safety procedures. So should i go for NiMH?

Thanks in advance,
Rob Grech

 

[itsmoked]

If the application isn't portable then go with the NiMH. If the application is portable it gets a little harder to choose but I'd try to to stay with NiMH.

The issue that is hardest with Li-ion is that if the battery ever over-discharges it becomes suspect as a future fire hazard. It's not easy to guarantee never under-discharging.

Re-reading your post; If you really need size to be minimum, Li-ion is likely the route you'd have to go.

You might consider regular nonchargeable batteries for an app like an emergency light. Notice that the most common emergency product in the world is a non-rechargeable smoke detector. The replacements are ubiquitous and more reliable than most rechargeable solutions. Rechargeable units imply either being plugged in all the time or that some human's contemplation is required to assure charging is occurring. With the non-rechargeable solution use the same blink to warn of a dying battery state.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[vikasbly44]

DEAR...
You could probably do a lot bettery in size and weight with Li-on batteries but it would bend you over to pay for them and you would need a fully engineered system to keep it safe enough to minimize liability.
Inverter Battery

THANKX...

 

[trebor8255]

First of all thanks for your reply.

This project that I'm designing will always be plugged in to the socket wall. So that's why I am working for a rechargeable solution. While I was making some research I found an IC from Microchip (MCP73831/2) which is a Li-ion charger management controller. So I guess that will solve some of the preoccupation regarding the charging circuit. However, I will have to include certain safety features such as high temperature cut-off and low voltage cut-off.

Is there anything else I should be concerned about?

Thanks for your help

 

[itsmoked]

I suggest you reverse engineer your solution. There are dozens of plug-them-in-an-outlet emergency lights on the market. Find one that matches closely your ideal, buy it, and hack it. You will likely be seeing the UL aspects needed in the device you dissect.

[URL unfurl="true"]http://www.amazon.com/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3Aplug%20in%20emergency%20lights[/url]

Keith Cress
kcress -

http://www.flaminsystems.com