Topic: Why NiCad batteries for FARS? Why not NiMH?

[bro931]

Just did some cleaning and PM on my VP2 with FARS.  The fan was not running at night.  Charged the batteries and it's been working 24/7 since.   Anyone know why they use NiCads to drive the fan at night and not NiHMs.  Nicads have that awful memory problem and if they discharge completely, they will not recharge.  I think that was my problem.  I can get C-cell NiMHs locally, but C-cell NiCads are not so available.

[nincehelser]

In general, a NiCd battery can handle many more charge-discharge cycles than NiMH.  We're talking thousands vs hundreds.

NiCd is also more resistant to damage if deeply depleted than NiMH.

You might try substituting a NiMH for NiCD, but it likely won't last as long.  Another unknown is if the existing charging circuit will work well with NiMH.

 

[SlowModem]

Another unknown is if the existing charging circuit will work well with NiMH.

I've got a switch on my inside battery charger for the different types of batteries.  I've always wondered what the difference was?

[Strgazr27]

Just did some cleaning and PM on my VP2 with FARS.  The fan was not running at night.  Charged the batteries and it's been working 24/7 since.   Anyone know why they use NiCads to drive the fan at night and not NiHMs.  Nicads have that awful memory problem and if they discharge completely, they will not recharge.  I think that was my problem.  I can get C-cell NiMHs locally, but C-cell NiCads are not so available.

I've discharged NiCads completely and never had an issue charging them again. In fact they should be drained and than fully charged to help prevent the memory issues.

[Bushman]

Discharging a NiCd battery below 1 v per cell will wreck it.

[nincehelser]

Discharging a NiCd battery below 1 v per cell will wreck it.

Well....maybe.   The real issue is reverse-charging among multiple cells.  NiCd might form dendrites (which can possibly be burned off).  NiMH can expand and rupture.

For single-cell applications it's not much of an issue.  I've even heard of some people storing NiCds shorted out (not charged, of course) for long-term storage.  (I'm not sure that's possible with NiMH.)

[jerryg]

Well i was going to stay out of this discussion but having been in the twoway radio business for over 40 years i am well versed in the battery pros and cons. Nicads will indeed get a memory if you keep charging the battery before it is fully discharged. We used to rejuvinate them by popping them with a twelve volt supply, this forced the battery to get over the memory and most of the time it worked unless the battery was pretty old and on its last leg, lol. Keep in mind the charging circuit on the fars is pretty simple, a resistor and a diode is all it has. The fan runs off of the solar panel during the day and batteries at night. So during daylight the batteries are being charged depending on the amount of daylight and sun that is available, not really a great way to treat nicads. You are right about storage of nicads, they should be discharged fully and for long storage they should be shorted out. The only thing about discharging the nicad is if you get the voltage down real low alot of chargers need a certain minimum voltage to start the charge and will indicate bad battery. Again you can zap the battery to get enough indication so the charger will start. If you use nimh batteries you need to the same current as the nicad. Davis uses 2000 ma and the charge circuit is designed to charge that size battery given the amount of daylight available. One thing about nicads is they are real good about maintaining the 1.2 volt rating for a long period of current draw where as the nimh will start dropping voltage with current draw. Keeping in mind the fan has a 1 to 3 volt rating the nicads should keep the fan running faster most of the night by maintaining a higher voltage. 

[dj1111s]

It could also be that NiCads perform better in cold weather than NiMH.  I know when I need to use a cordless drill outside during the winter I gotta get out my older NiCad powered one.

[Aardvark]

When I got my 24 Fars from Archer this summer, the batteries were dead as dead can be.  After a week  they didn't charge, so I ordered from Amazon new NICADS  and a charger that would first discharge the battery to zero  and then charge it up. I then replaced the batteries that came with the unit with the new charged ones and so far they do work day and night.

Maximal Power FC999 Universal Rapid Charger for Alkaline, RAM, Ni-MH, Ni-CD, AA, AAA, C, D, N, 9V Batteries   from Amazon.  I did contact Davis and they sent me out 2 new batteries although I already had the unit installed plus a backup fan.  I am guessing that the batteries  have a shelf life/charge life and yours might have been past their prime.

This will be the first winter with the FARS and I am curious how they will hold up after winter here.  It can be brutal

[dj1111s]

This will be the first winter with the FARS and I am curious how they will hold up after winter here.  It can be brutal

A local meteorologist from Milwaukee just stated today he's predicting a colder than normal winter.  Should be fun.

[Cienega32]

We used to rejuvenate them by popping them with a twelve volt supply, this forced the battery to get over the memory and most of the time it worked unless the battery was pretty old and on its last leg, lol.

Could you explain this process a little more for me?

[W3DRM]

Here's a link to some information about NiCD battery charging issues.

• http://www.buchmann.ca/article10-page1.asp

[jerryg]

A nicad battery is lazy and if you keep charging it up before it gets low capacity then it will get a memory say you have a 12v battery and you keep charging it when it half down, it will get a memory around 6 volts and when you charge it it will charge from that point to the 12 volt point and never get the full capacity back. When it has this memory you will find you have to charge the battery alot more because it is working with less than full capacity. We have high dollar battery conditioners that cycle the battery several times to break the memory and get full battery capacity back. The poor boy way is to use a higher voltage than the battery to force a large current into the battery to break memory. Say a 12 volt battery you might use 16 volts or so and just tap the contacts several times. It works most of the time.

[Cienega32]

The poor boy way is to use a higher voltage than the battery to force a large current into the battery to break memory. Say a 12 volt battery you might use 16 volts or so and just tap the contacts several times. It works most of the time.

Good to know! Thanks for that info.

[Aardvark]

I have an electric tooth brush. Wheee..  and it uses an induction charger, however..  I have noticed that unless I let it go down to stop, no motor phase, when it is charged  before,  the frequency between recharging is less days .      I found it interesting that when I had the old one that just wore out, it had in the instruction manual to once a month let it go to a zero operation state then recharge it,  but the new manual has no mention.

such is life

[Old Tele man]

I have an electric tooth brush. Wheee..  and it uses an induction charger, however..  I have noticed that unless I let it go down to stop, no motor phase, when it is charged  before,  the frequency between recharging is less days .      I found it interesting that when I had the old one that just wore out, it had in the instruction manual to once a month let it go to a zero operation state then recharge it,  but the new manual has no mention.

such is life

The new tooth brush manufacturer wants you to have to buy ANOTHER unit...SOONER...ala' Caveat Emptor (wink,wink).

[Aardvark]

of course, that is called economic success. 

[Ranger4]

of course, that is called economic success. 

I think it's more like customer rip off. Seems to be getting more of a problem these days.

[Bushman]

Planned Obsolescence is what it is.