Re: Charge Gel Cell In Car


From: Lee Mairs (
Date: Thu Nov 14 2002 - 12:15:17 CST

There may be a problem here. Gel cells and flooded batteries are not the
same chemistry. Every gel cell I've checked on has a maximum charging
voltage of no more than 14.1 VDC. I am very careful to avoid mixing flooded
and gel cells in the same system on boats. Occasionally, there is no
choice, but I make sure the customer is aware of the potential problem.
73 de Lee, km4yy

----- Original Message -----
From: <>
To: "Low Power Amateur Radio Discussion" <qrp-l@Lehigh.EDU>
Sent: Thursday, November 14, 2002 12:37 PM
Subject: Re: Charge Gel Cell In Car

> I have a Walmart gel cell in a plastic case that I intend to use
> one can charge it also (for very short time) using a cable to the
> car's cigarette lighter.
> When I fabricate my own cable, will I need to include a series
> resistor inside one plug, or is direct connection to the car
> battery through the lighter appropriate?

Since both the car battery and the gel cell are the same chemistry,
no dropping resistor should be needed. However, be aware that some
cigarette lighters are "hot", not switched with the key. This
effectively puts the gel cell in parallel with the car battery
which might cause some problems when starting the vehicle. So
fusing the charging cable would be a good idea. As far as charge
times, the only time any current would be flowing is while the
engine is running. I doubt there are many trips you'd take with
the engine running long enough to overcharge a gel cell (24+hrs).
I think their "very short time" warning was just so people wouldn't
leave the power pack permanently connected.

Mark K5LXP
Albuquerque, NM

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