Charging NiCad batteries

[cindersailor]

I recently bought a Standard Horizon HX260 hand-held VHF. Quite impressed with it so far, but have yet to test it very extensively. I noticed that on charging the battery it became quite hot, much more so than I am used to with mobile phones etc. The battery is 7.2 V and the charger says its output is 12 V, however when I measured it it was almost 16 V which will probably explain the heating. If I use an alternative charger which does measure as giving 12 V there is no heating at all. Although the charger was supplied with the VHF, I do not think it is the normal one as it is one which is used with a 12 V DC charging lead which is useful as I can use it to charge on the boat. Being curious I also checked the output of my nominally 14.4 V drill charger and found that it gives 20 V!

A couple of questions:
1. Is it normal for mains chargers to to have voltages way above their rating, or is what I am finding because I am testing them "off load"?
2. Has anyone else experienced this type of heating and am I doing the battery damage as I am assuming?

 

[steve28]

is the charger dc ?, maybe the regulation is done in the radio ?

Possibly could have had the charger muddled up if it was a display item ?





this is only a suggestion and several others will no doubt dissagreee /forums/images/graemlins/smile.gif

 

[cindersailor]

I assume it must be DC as it can be charged from a 12 V battery. Also my multimeter was set to measure DC volts!

 

[gjeffery]

I too have a Standard HX260E handheld VHF. A good set, but my charger is badged as Yaesu, who of course are Standard Horizion, and is rated at:

Input 230V AC 50 Hz 30mA
Output 9.4V DC 80mA

Part No 954915

I suspect you may have the wrong charger! When I contacted Yaesu at Winchester, I found them most helpful. You might try Googling their e-mail.

 

[cindersailor]

Thanks for this info, my charger is certainly not from Yaesu. Whether anyone could tell me the the output of their genuine HX260 charger was going to be my next question.

I think I will get in touch with the supplier, they seem to have sent the wrong charger.

 

[Talbot]

I suspect that the charger is similar to unregulated supply from a solar panel or wind charger. Thus much higher voltage than expected when not under load (i.e. not connected to the battery) I dont see how you could measure this unless it was under no load, thus would appear to be wrong. I would expect the regulator to be an integral part of the H/H. Quite frequently the battery and charger will get quite hot as they are massaged to 100% charge - try a laptop charger and its battery for comparison. Thus the charger may be correct!

 

[bonny]

Since you received the wrong charger with the VHF and the battery became hot, almost certainly due to overcharging it is possible that the battery may have been damaged. Although it may still work and appear to be OK, it's life may have been somewhat shortened. I would request a replacement battery aswell, or if it's integral to the set then a replacement VHF.

 

[Otter]

My HH VHF charger has a rated output of 12v for an internal battery of 9.4v. This is normal isn't it? When we charge our on board 12v batteries the voltage goes up to about 14v.

 

[Avocet]

Did you measure the voltage when it was charging or with no load? As Talbot says, most unregulated chargers can give rather higher voltages under no load. Discharge the batteries and measure it again when it is working hard. I think the voltage will be muh lower.

 

[ShipsWoofy]

Some useful advice for the future here

I do not want this to come across as a lecture but some interesting things have been brought up here regarding regulated and unregulated power supplies. The fact that the unregged will drift high when the load fails.

For any of you reading this, it is very important if you are sourcing an AC/DC power supply for delicate equipment such as digi cameras, mobile telephones PDA's and laptops for example to pay that little extra for the regulated supply.

Sorry for jumping in, but modern equipment may be fried by cheap supplies, an example suck as running a digi camera with the batteries removed on a cheap supply may be RIP for it.

Sorry if I am teaching you all to suck eggs, just thought it might be useful to someone one day.

 

[William_H]

Re: Some useful advice for the future here

There is always a conflict with NiCad battery chargers. The public demand a fast recharge but that recharge rate can be detrimental to the batteries when left on long term. So warm batteries may be fine provided you limit your charging time to like 3 hours but an overnight may be bad. A charger for any battery must be higher in voltage than the battery voltage at full charge and the charging current is limited by a resistor or complex regulator arrangement. Your best way to decide if you have a problem is to remove one battery lead and insert your muultimeter on current range and measure charging current. The battery hopefully will specify charging current. Old Nicads used to be rated at one tenth of the Amp hour rating but charged for 14hrs. This rate was also considered ok for long term. so if the battery is rated 1400maH then a charge rate of 140 ma is OK. now newer batteries can be charged at higher rates for say 3 hrs at 500 ma but I wouldn't leave them longer than 3 hrs.
if you think you are charging at too much current then a fix to do yourself is to cut the wire of the charger and fit a resistor in series. 30 ohms (1 watt)would be a good start. of course it is a pity to cut the wire and it will always be a source of potential failure but will save the batteries. As said before measuring the voltage presented by the charger when not connected to the radio is a bit pointless although obviously a higher voltage probably produces high charge current. good luck olewill

 

[Porthandbuoy]

Ni-Cad batteries require a constant current charger, so measuring the voltage of the charger is of very little value (other than telling you it's not working at all).
Modern Ni-Cads, in an attempt to speed up the charging process, can tolerate higher currents; and that means heat.
It's not a bad idea to remove rechargeable devices from their cases during charging; that helps the heat to dissipate.
William_H is correct when he says old Ni-Cads could be left connected to the charger "long term". I wouldn't recommend doing that with the latest generation of batteries though.