Problems with Portable radio when running off Ni-MH batteries

[Clunkclick]

My two year old Roberts Stream 205 has suddenly developed a problem when running-off slightly discharged NI-MH batteries (It takes 6 "D" Cells - "Extreme" 10,000Mah units fitted, bought the same time as the radio).

 

When on battery, Its starts up OK, the LCD display panel illuminates, you can still switch bands and tune to a specific frequency and set the pre-sets, but NO SOUND !

 

This has only started recently, it used to be fine on batteries.

 

It stillworks OK when running off the manufacturer's mains adapter.

 

I've tried doing a factory reset on the radio's software. No change. And I've confirmed that the boot software is the most recent.

 

I suspect its a voltage problem with failing batteries.

 

So, I've got a set of Duracell alkaline's on-order and the E-mail response I received today from Roberts's Tech support suggests that batteries might be the cause.

 

2 year life seems a little short for Ni-Mh batteries.

 

Is there a common  performamnce degradation cascade/regime that applies to modern radios of this type if they sense that the power input is non-conforming ?

 

 

Nick

Edited 31 July, 2013 by Clunkclick

[Breezy_Pete]

The user manual suggests on its page 7 that you may not have a lot of joy with NiMH, though it would lead one to believe that the issue is purely of capacity.  I suspect that the fundamental problem is that there isn't a lot of 'headroom' for the voltage regulators inside the thing with NiMH cells at a nominal 1.2V each, versus alkalines at 1.5V each.  Two years use doesn't sound too bad for rechargeable batts; it depends how often they get discharged/recharged.

 

The power amplifier chip that drives the speaker(s) will use the highest voltages available in the unit, and so will tend be the first thing to 'fall over' if the voltage dips too low.

[rotodiesel]

DAB radio is an utterly stupid concept. In a portable, the energy consumption is so high that massive batteries are required with limited operating time. There are no lightweight DAB portables. For Hi Fi use, FM sound is better than DAB as the bandwith of the latter is so limited. Reception in the limited number of cars in which it is available, is very patchy and totally unforgiving of poor reception. Finally, thanks to poor groundwork by the BBC, the UK uses an obsolete format.

 

It's high time the BBC took its corporate head out of the sand and scrapped this lousy system rather than trying to promote it by limited access broadcasting. I suspect they're too pig-headed to do this and will soldier on spending our money until they are forced to scrap it due to obsolescence.

 

For most radio users, DAB solves no problems and creates several others.

 

rotodiesel.

[goonybird]

DAB radio is an utterly stupid concept. In a portable, the energy consumption is so high that massive batteries are required with limited operating time. There are no lightweight DAB portables. For Hi Fi use, FM sound is better than DAB as the bandwith of the latter is so limited. Reception in the limited number of cars in which it is available, is very patchy and totally unforgiving of poor reception. Finally, thanks to poor groundwork by the BBC, the UK uses an obsolete format.

 

It's high time the BBC took its corporate head out of the sand and scrapped this lousy system rather than trying to promote it by limited access broadcasting. I suspect they're too pig-headed to do this and will soldier on spending our money until they are forced to scrap it due to obsolescence.

 

For most radio users, DAB solves no problems and creates several others.

 

rotodiesel.

 

What a load of carp. No format is ideal. Vinyl, cassette, CD, AM(stereo) FM DAB etc.   

 

Dab is MP2 which is old technology BBC should have waited for MP3. But try receiving Jazz FM in Northampton on FM from Croyden. £1000 plus Revox tuner with 8 element yagi and antenna amplifier an I was still lucky to get hissy stereo.  Now with a reasonable quality MArantz tuner, now have good sound quality near to CD/Vinyl and other stations eg Planet Rock.

Same in car quality sound from Noerthampton to Yorkshire wiithout a single dropout. It works FM doesn't. And until DAB+ then its fine.

Note at the Mega meet i had difficulty convincing people the hi fi in car was on DAB. Most would have sworn it was CD.

nuf said.

 

[Clunkclick]

 FM's become  unusuable here and it seems to have got worse since the completion of the digital switchover and that's the same whether its captured by the Roberts portable's aerial or by the Denon Radio Receiver through a loft aerial pointing at Crystal Palace.

 

IMHO,  the DAB radio ouput is just as good as the radio outout that the Sony Freeview TV (Not DAB) produces, without the sound pixellation effects that come with interference on Freeview. The power consumption of the Roberts portable @120 Watts surprised me. As i"m home most days now,  I was hoping to save power by not using the radio facility on the Sony TV which consumes 60 watts in normal operation (And that"s with the screen on) - no chance of that.

 

Thinking about it, I"ve only recharged the radio's batteries two or three times in the two years since I've had the set and, conveniently,  and probably used it as a true portable for not more than a couple of  hours .

 

It will be interesting to see, when the alkalines arrive, whether normal service is restored.

 

Nick

 

 

[Clunkclick]

I don't think high current usuage is something that"s restricted to DAB.

My  previous Roberts Radio, a 9921 pocket portable (FM/MW/SW), was even worse with batteries - you were lucky if you got three hours use from a set of 5 x AA cells. But that was due, I understand, to the excessive power consumption of the early version PLL tuner.

 

When I bought the latest set, I was hoping, that like the laptops before them, the processors that the radio manufacturers were now using would have evolved into low power consumption types -obviously not.

 

One wonders, if low power consumption reduction in radios isn't on the horizon, why aren't they using minature accumulators, like Yuasa make, for the power supply.They would have the advantaged that the battery coukd be recharged in situ and its unlikely that it would weigh anymore than 6 x "D" cells.

 

Just thinking back to the 1960s, the old table top portable's, like the original Bush TR82, had a Zinc-Carbon power-pack battery (PP9), which was similar in size to 4 x "D" cells, but even with an hour a day's use of the radio, the battery would last a good 18 months.And that battery was running large scale component, pre-integrated circuit units.

 

Is radio technology going backwards ?

 

Nick

[Clunkclick]

New Alkalines in ( All (6 x) 1.6 v, 6.6-8.5 amps) and all's now OK with the sound.

 

The problem, it would appear was that 2 of the six rechargeables had completely discharged ( 0.2-0.5 volt, 0.02-0.05 amps). The other 4 cells were fine (1.2 Volt, 13.5 amps).

 

I think the two duff cells are the lead supply cells, as they were located in a seoarate part of the battery compartment. I wonder if the link between the two parts of the battery compartment has gone u/s. Time to get the multimeter out.

 

 

Nick

 

 

[Clunkclick]

No, the circuit between the sections of the battery compartment seems to test OK.

 

I"ll attempt to re-cbarge all of them, and see what happens.

 

I never before come across a situation before where batteries in. series discharge so unevenly. You usually expect the cell nearest the positive terminal to discharge the more than the trialling cells, but I've never seen a case where the lead batteries are completely discharged and the remainder are almosr fully charged after a period of use.

 

Anybody any ideas what may cause this ?

 

Its also odd that cells 4-6 in the series, are all rated 10mah, but are showing 13 amps i.e. One-third over rated cspacity. I'm wondering whether there is some sort of reverse flow going on, where charge is being leeched from cells 1-2 into cells 4-6. I'm thinking this may be o curing when the radio is not in use.

 

Again, has anybody beard of that happening ?

 

 

Nick

Edited 3 August, 2013 by Clunkclick

[Breezy_Pete]

Just stick with alkaline cells, or buy a couple of new NiMHs to replace the duff ones - better still, the full set.  Don't worry about which battery might be where in the series, it's all the same to them. :wonder:

 

From your above post, it seems like you may be attempting to measure the capacity of cells by short-circuiting them through your multimeter, with it set on 'amps'. This is potentially dangerous, and will not give you the information you are seeking. 

[Clunkclick]

Alkalines are fine, at the moment. Only trouble is tbat they have only 50-65% of the capacity of tbe Rechargeables according to my "Testing". So at the maximum usuage of the Radio, 1.5 amps per hour (According to the plate on the mains adapter), then, I will only get 4 hours out of them.

 

According to the internet, current consumer electronics radios and similar devices are usually  designed to stop working (In part or whole) when the voltage falls below 1.1 volts in a system rated flor a 1.5 volt supply i.e. At 73% of full rating. The rechargeables I was using packed up when the voltage on the two lead batteries showed between .25 and .5 of a volt i.e. 16-32% of full rating, so by that measure they did pretty well. And the fact that when fully charged they have a capacity of sligthly over 8 hours, means that they are sligthly more convenient to use. And they are considdrably cheaper to recharge than the alternative, buying a new Alkaline.

 

I've got alkalines in at the moment, but I think I'll its worth re-charging the Ni-Mhs.

 

Advice on the internet recognises that uneven capacity and uneven discharge whilst not in use/in use is a common feature of Ni-Mhs and ennumerateswhat can be done to remedy this - see thd camera and modeller forums. Most of then recommend complete discharge of Ni-Mhs before recharging and that the discharge and recharge is done individually in order to maximise capacity - Unfortunately that means that you can only discharge/recharge one battery at a time, as far as the cheaper rechargers (Sub £25) are concerned - though more exoensive rechargers like Maha and Powerex are reputed to be able to discharge and recharge multiple batteries at one time on an individual battery basis.

 

I"m also lead to understand tha t by battery. "Matching". I.e. Singling out batteries with similar discharge/recharge/capacity,  one may be able to recharge to full capacity like batteries by recharging them together - that's something I may try with my rechargeables, which appear to have naturally seoarated themselves into two groups.

 

I don't anticipate any problems using the ampage circuit of my multimeter as a battery discharger. Although its only rated 10 amps DC, unfused, I'm only testing each battery for max 10 - 15 seconds at a time (Enough to get a consistent reading), neither the meter or the batteries are getting warm and the meter is a 35 year old rugedised Fluke which has seen eorse than that and survived.

 

It will be interesting to see whether the alkalines discharge pattern will be tbe same as the rechargeables i.e. Two lead cells fully discharged and the remainder near fully charged.

 

I'm windering if Maha/powerex do rechargers fo D cells.

 

 

Nkck

Edited 4 August, 2013 by Clunkclick

[Yearofthegoat]

I have a Powerex/Maha charger and it can manage up to 4 batteries at once.  You can set each one individually, so you could be charging one, breaking in another, cycling a third etc, all of different types if you wish.

 

Ordinary NiMHs don't keep their charge very long, so I use Sanyo enerloops, and they're great for kids toys like my daughter's little Storio thing.  It might be a couple of weeks between uses but the batteries keep their charge fine.  I don't know if enerloops or the like come in D size, however, and of course you'd need an appropriate charger.

[Clunkclick]

The Sanyo batteries have got good reports on them.

 

I don"t think maha do a recharger for "D" cells, in which case iI have to resort to battery matching.

 

Can anybody recommend a goox discharger for D cells ?

 

 

Nick

[Yearofthegoat]

You can get adapters for AA to D size. Obviously AAs don't last as long, but the adapters are cheap and let you use the more 'user friendly' batteries.

[Clunkclick]

Adapters sounds good, if only for the fact that it will reduce the re-charge time.

 

It took 24 hours for the fully discharged 10,000 Mah "D" cells to recharge completely, whereas the 1200 Mah AA cells topped-up in an hour !

 

I'll take a look on Amazon/Maplin

 

Nick

[Clunkclick]

Re-charged all the 10,000 Mah Ni-Mh cells now. The partially discharged ones re-charged to 100%. However, the two that were completelty discharged will now, only recharge to 80 and 90%  of full capacity respectively ( As measured on the recently acquired AnsMann) - that's despite cycling them about three times through the charger.

 

Any ideas how to restore these two batteries to 100% function ?

 

 

Nick

Edited 10 August, 2013 by Clunkclick