[Elecraft] Charging LiFePO4 Batteries

[Jim Brown]

This is what I got from Kevin.  We also spoke on the phone.

On the phone, Kevin clarified that as long as the charger was "proper" 
for LiFePO4 chemistry and charge current was safely limited, an LiFePO4 
battery will NOT be damaged if charged during discharge. His only 
concern was that the battery might not reach full charge simply because 
more current was being drawn than was being supplied by the charger.

SO -- the bottom line is that LiFePO4 batteries ARE suitable for use as 
the main power source in a station where a charger is always connected 
as long as the charger has the proper charging characteristics for the 
LiFePO4 in use.  In general, battery life is maximized if the maximum 
charging current is no greater than the 4-10 hour discharge current. For 
example, a 10A charger is sold by Bioenno with their 40 - 100Ah 
batteries. Higher charging currents reduce battery life.

Kevin also said that they have taken our concerns seriously with respect 
to RFI from chargers, and that they have begun working on sourcing 
chargers that are RF quiet. He noted that it typically takes 3-6 months 
to find potential candidates, evaluate them, and get them in inventory. 
I've volunteered to evaluate them in my station for noise.

Bioenno also works with Powerwerx, so they are generally aware of 
connector issues. He said that they are using the larger connector as 
standard because some of their customers need the larger connector with 
the higher current rating.  The grey SB50 connectors used in the ham 
world are rated for 50A.

73, Jim K9YC


  On Tue,7/12/2016 11:39 AM, Kevin Zanjani wrote:
> Hi Jim,
> I needed to clarify my response.  Maybe it's easier to explain over 
> the phone.  My number is 714-336-2953
>
> The batteries with the bundled chargers, use constant current, 
> followed by constant voltage to charge the batteries.  Generally, with 
> these chargers, if the battery is loaded while the charger is 
> attempting to charge the battery (under a high load condition), then 
> the battery may not be able to achieve a full charge as its loaded 
> under a high load condition  (it would certainly charge).  If the load 
> is fairly low amperage, that is less than the charge current, then yes 
> the battery can take the full charge.
>
> With the PWR gate, you can certainly charge and discharge the battery, 
> because there is a separate power supply that can provide a large 
> enough charge current to the battery, while also supplying power to 
> the radio from that supply .  So in that setup, it is perfectly fine.
>
> So it depends on the charge current available to charge battery versus 
> the load power to ensure the battery takes a full charge.
>
> -Kevin
>
> On Tue, Jul 12, 2016 at 10:52 AM, Jim Brown 
> <k9yc at audiosystemsgroup.com <mailto:k9yc at audiosystemsgroup.com>> wrote:
>
>     Kevin,
>
>     I've been using the battery for about a week. Some correspondence
>     you had with Wes Stewart concerns me greatly -- in effect, it
>     negates the use of the battery in my station. I bit of background.
>     Most ham gear is designed to run from a DC source in the range of
>     12-14V, and its performance is best near the top of that range.
>     For many years, I've used flooded lead acid cells that are
>     float-charged as the primary power source for the 12V equipment in
>     my station, but had to accept the fact that for most of their
>     discharge, they are at 12V or less. The primary reason for going
>     to LiFePO4 chemistry is the discharge curve, with most of the
>     battery's capacity above 12.5V.
>
>     I am a contester. Typical contest operation for me is with two
>     radios, each drawing about 1.5A in receive mode and between 10-20A
>     in transmit mode, depending on the contest. Only one radio is
>     transmitting at a time. The 10A contests are 36 hour events, the
>     20A contests are 10 hours long. It doesn't take much arithmetic to
>     realize that a 100Ah battery must be charged during operation to
>     handle the load.
>
>     Your response to Wes seemed to indicate that LiFePO4 batteries
>     cannot be charged during use -- that is, that they must go through
>     a discharge cycle. I can find no technical references online for
>     this statement, so I'd like to know the basis of your advice to
>     Wes. Can you point me to technical references for this?
>
>     Some other comments now that I've been using the battery in my
>     station for several days. The PowerGate controller seems to work
>     fine -- IF the power supply is set to a high enough terminal
>     voltage to provide 10A charge current.
>
>     The 4A charger you provided for my 20Ah battery pack works fine,
>     but generates significant levels of RF noise. I can suppress that
>     noise somewhat, but not well enough, by winding multiple turns of
>     both AC and DC cables through ferrite cores to form common mode
>     chokes. I've seen comments online from other users of your
>     chargers indicating that they are too noisy to use in a radio
>     environment. As I told you last week, it is important that you
>     find chargers that produce far less RF noise. This is also
>     critical for the pro audio market, especially for video production
>     work.
>
>     The Power Pole connector for charging is well chosen; the larger
>     connector for the load is not. Ham applications have standardized
>     on the smaller Anderson SB50 series for use with power sources.
>     It's no problem for a technical user to replace the larger
>     connector that you ship with, but it's added cost and time. And,
>     of course, the technician must mount only one conductor at a time,
>     inserting it in the connector shell, so that there is no
>     possibility of shorting the battery in the process.
>