GellCell Charging with bulb

[Thom LaCosta]

Realizing certain pitfalls, can someone tell me what typle of bulb I can put in
series between a dc source and a 7 ah gell cell to maintain a charge on it...I
have more gell cells than proper chargers, and my thought was to get them up to
full charge with a "real" charger and then use the series bulb to maintain the
charge.

Thanks

73,Thom-k3hrn
www.zerobeat.net Home of QRP Web Ring, Drakelist home page,Drake Web Ring,
QRP IRC channel, Drake IRC Channel, Elecraft Owners Database
www.tlchost.net/hosting/  ***  Web Hosting as low as 3.49/month
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Brown-4]

Hi

Maybe I can help. Gel cells should not be allowed to discharge below 10
volts and charged above 14.5 volts or damage may result. If you want to
maintain a float charge on the battery you should set the power supply to
13.8 volts and limit the current to about 1/3 of the rated amp hour of the
battery. You can do this with a current limiting power supply or you can use
a resistor in series with the battery to limit the current. When the battery
is fully charged the current draw at 13.8 volts will be only a few mA. If
the battery is discharged then the current can be quiet high without some
form of current limit. The difference between 13.8 volts and say 11 volts in
a discharged state is 2.8 volts. So in the worst case you need to calculate
the the resistor value that would limit the current to 1/3 of the amp hour
rating of the battery. In the case of a 7 amp hour battery that is 2.33
amps. 2.8/2.33 is 1.2 ohms. I have some 4 watt 12 volt lamps used in low
voltage outdoor lighting that read 3.4 ohms cold this should work for you or
a dash lamp for a car or even a car tail light as long as it is 1.2 ohms or
higher. Do not set the power supply higher than 13.8 volts even with the
limiting resistor (bulb) as the battery will continue to charge to whatever
the power supply is set to.

Don Brown

KD5NDB




----- Original Message -----
From: "Thom R LaCosta" <[hidden email]>
To: "Elecraft email" <[hidden email]>
Sent: Wednesday, November 01, 2006 4:40 PM
Subject: [Elecraft] GellCell Charging with bulb

> Realizing certain pitfalls, can someone tell me what typle of bulb I can
> put in
> series between a dc source and a 7 ah gell cell to maintain a charge on
> it...I
> have more gell cells than proper chargers, and my thought was to get them
> up to
> full charge with a "real" charger and then use the series bulb to maintain
> the
> charge.
>
> Thanks
>
> 73,Thom-k3hrn
> www.zerobeat.net Home of QRP Web Ring, Drakelist home page,Drake Web Ring,
> QRP IRC channel, Drake IRC Channel, Elecraft Owners Database
> www.tlchost.net/hosting/  ***  Web Hosting as low as 3.49/month
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com