|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
22nd Mar 2017, 10:26 pm | #1 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Battery reverse polarity?
Listening to my small Grundig Solo Boy yesterday afternoon, after about an hour or so of listening it started to go very quiet and distorted. I had only put new batteries in just after Christmas and it was only used for a couple of hours since, so I was a little disappointed that they had run out already, or so I thought. I removed them, they were all installed correctly, and put them across the meter to find 3 of them were still very good and one was reverse polarity. They are the Kodak Xtralife alkaline C size 1.5v almost certainly from Poundland. Has anybody ever had this happen to them? Also could it cause any damage? The battery on the left is the culprit and if you look you can see the pressed part at the top is ever so slightly rounded/bulged compared to the battery on the right.
Regards Poppydog |
22nd Mar 2017, 10:37 pm | #2 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
|
Re: Battery reverse polarity?
I have experienced cells being reverse charged when connected in series before. I think it happens when one of the cells runs flat before the others do. This is why they always say to replace all the cells at the same time and don't mix cells of different type or old and new ones. Saying that I once had a new motorbike battery which was incorrectly marked polarity wise. It was only by luck that I connected it to a charger before putting it on the bike and found the charger meter reversed and the cut out tripped. So it has been known.
Alan. |
22nd Mar 2017, 10:51 pm | #3 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
|
Re: Battery reverse polarity?
Yes i have had it happen. Occasionally with dry/primary cells (but also with Ni-Cads that have been flat for too long.) I don't imagine it would ruin the other cells in the stack, but i have nothing other than instinct to back this up.
|
22nd Mar 2017, 10:57 pm | #4 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
|
Re: Battery reverse polarity?
I have very rarely had this happen too, even with sets of fresh batteries from well-respected makers that were installed from the same pack. I think the only type of battery where serious damage would arise from reverse charging is Lithium rechargeables, where reverse charging would cause the production of metallic Lithium. Lithium metal is extremely reactive and will readily ignite or even explode. That is why individual cells are not normally available to the public, only made-up sealed battery packs where the individual cells, being permanently connected, cannot accidentally become reversed and incorporate suitable protection. I do wonder if the exploding laptops that featured in the news a year or so ago, were caused by unscrupulous battery manufacturers omitting safety components to save money, just as some cheap switch-mode power supplies omit the components that would deal with the RFI once they have got their CE approval.
Some years ago I acquired a couple of ex-equipment 12V battery pack made up of 10 SAFT 4Ah NiCads. Across each cell was a inverse-connected diode, evidently to prevent reverse charging if the pack were to be discharged to exhaustion. Last edited by emeritus; 22nd Mar 2017 at 11:06 pm. |
22nd Mar 2017, 11:15 pm | #5 |
Dekatron
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 3,301
|
Re: Battery reverse polarity?
Yes I had this happen with an "Energiser" alkaline AA battery. Perfectly good but in reverse!
__________________
"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly." |
22nd Mar 2017, 11:56 pm | #6 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
|
Re: Battery reverse polarity?
Yes , quite recently, not seen it before though, alkaline Tesco one if I remember correctly. The others of same age were ok but the lot were replaced.
Frank |
23rd Mar 2017, 7:03 am | #7 |
Heptode
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 663
|
Re: Battery reverse polarity?
Kodak batteries are rubbish. I had mass problems with them when I was servicing.
The folks bought them because they were cheap. Philpott has it correct on the cause. Never saw any other brand do that, excepting reverse charged NiCad's. |
23rd Mar 2017, 9:20 am | #8 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
|
Re: Battery reverse polarity?
Standard problem with series strings of NiCad and NiMh rechargeables. The one that gets reversed is very quickly ruined. With primary cells it doesn't matter so much, because the one that has charged backwards is rubbish anyway
This is the reason I am very cautious about more than two rechargeable cells in series unless the load has low battery switch off/warning, which they seldom do |
23rd Mar 2017, 10:42 am | #9 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
|
Re: Battery reverse polarity?
Hi.
I also experienced this a couple of months ago with some AA alkaline cells made by GP. I had 3 in series supplying those timed LED Christmas lights. GP cells are generally very good and I've so far not had any leakage problems with them so would continue to use this make. Regards Symon. |