Homebrew battery tester ideas? - UK Vintage Radio Repair and Restoration Discussion Forum

Tractorfan · 27th Dec 2018, 1:44 pm

Hi,
As is usual in our house, there are loads of AA and AAA cells kicking around; Alkaline, ni-mh, ni-cd. And it's a job keeping track of their state of charge.
Therefore, I'm looking for a circuit for a homebrew tester that will give me a fairly good idea of what's what. The cheapo one I have only has a lamp, and it's difficult to judge from the brightness (dimness?) thereof.
Therefore, I'd like to build one using suitable switchable load resistors for each type of cell, and having an analogue meter to indicate the terminal voltage, and to monitor any fall in voltage.
Any ideas, Gents and gentesses?
Thanks in advance.
Cheers, Pete.

Bazz4CQJ · 27th Dec 2018, 2:32 pm

Before they disappeared, many people on the forum bought the £9.99 analogue multimeter which Maplin were doing, which has loaded test positions for both 1.5 and 9V batteries. The Model no. was Pro's Kit MT-2017. Maybe see if you can find a circuit diagram for that, just to copy those two elements? I have found those functions to be really quite useful.

That meter is still available elsewhere, but the price has shot up !

B

Refugee · 27th Dec 2018, 2:48 pm

I have got a Maplin digital one with a battery test function.
The ball park figure is 33ma and 18 ma for 1.5V and 9V.

mickm3for · 27th Dec 2018, 3:03 pm

manual for mt2017 says load 270ma 1.5v and 25ma for 9v

mickm3for · 27th Dec 2018, 3:14 pm

Hi resistors =1.5v 5.5 ohms and 9v 360 ohms checked on a pcb from said meter hope this helps Mick

Andrew B · 27th Dec 2018, 3:31 pm

If we are on about battery voltage under load, it's going to need "nihd" and "dry" battery positions on the switch to account for the different chemistries, also "9v" ni-mh are usually 8.4v.

A good 1.2v ni-mh should allow at least 250mA to be drawn without voltage sag.

Oldcodger · 27th Dec 2018, 4:48 pm

Don't forget about NiCad ,which are about 1.2 per cell . I've thought about something that I could load a cell with and watch on a DVM , but on reflection this project becomes more like the childs swing one.

27th Dec 2018, 5:34 pm

It is very hard to tell the state of charge/left capacity of a cell with a voltmeter, all you can do is load it and hope for some volts. This will not indicate how much is left, may as well use the item they are in until it stops working, then replace. Easier to have spares in stock. The dear MT2017 does a good "is the cell/battery still alive enough" job as would a 'normal' meter with a bit of a load, I like them so much I have three.

G6Tanuki · 27th Dec 2018, 6:13 pm

You used to be able to buy cheap little portable battery-testers that had a meter [one of those 'edgewise' types often used as record-level meters on cheap cassette-recorders] that was simply calibrated red/green to indicate bad or good.

Similar things are still available for a fiver or so - google "rolson 28101"

saddlestone-man · 29th Dec 2018, 7:56 pm

Hi Pete

I had a similar idea for a project then realised that life was too short and family members were unlikely to search around for the missing test leads, etc and so I invested a massive £3 or so for a 'Universal battery tester' (made in China of course) from ebay. The analogue version is only £2.70 post paid now. It's so easy to use that the grand children check batteries for me.

There's also a digital version for a 50p or so more money, but you have to look on the back to work out if your battery is good or not, rather than look at the coloured bands on the analogue meter.

You soon get to know if a battery is good or not by comparing where it is in the coloured bands compared to a fresh one.

I guess rechargable batteries are trickier, but most things that you put them in (cameras, tools, etc) tell you when they are low, and you can always pop them onto the charger that you have to have anyway and it will indicate the state of charge.

Photos of my tester attached here so you can see the loads it applies to 1.5V and 9V batteries.

best regards ,,, Stef

saddlestone-man · 29th Dec 2018, 8:14 pm

Just taken a look at the rolson 28101 and I see that it also tests bulbs and fuses. Very useful.

Of course it needs a battery itself so that's one more potentially (no pun intended) to worry about.

Best rgds .... Stef

broadgage · 29th Dec 2018, 8:15 pm

For a single cell, I use a 1.5 volt torch bulb in parallel with a one ohm resistor, this draws just over an amp from a good cell and the brightness of the lamp is easily and quickly observed.

For small 9 volt batteries I simply use a 6 volt 0.3 amp indicator bulb. No parallel resistor is needed, the 0.3a lamp current is a reasonably severe test for these small batteries.

27th Dec 2018, 1:44 pm	#1
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,183	Homebrew battery tester ideas? Hi, As is usual in our house, there are loads of AA and AAA cells kicking around; Alkaline, ni-mh, ni-cd. And it's a job keeping track of their state of charge. Therefore, I'm looking for a circuit for a homebrew tester that will give me a fairly good idea of what's what. The cheapo one I have only has a lamp, and it's difficult to judge from the brightness (dimness?) thereof. Therefore, I'd like to build one using suitable switchable load resistors for each type of cell, and having an analogue meter to indicate the terminal voltage, and to monitor any fall in voltage. Any ideas, Gents and gentesses? Thanks in advance. Cheers, Pete. __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

27th Dec 2018, 2:32 pm	#2
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: Homebrew battery tester ideas? Before they disappeared, many people on the forum bought the £9.99 analogue multimeter which Maplin were doing, which has loaded test positions for both 1.5 and 9V batteries. The Model no. was Pro's Kit MT-2017. Maybe see if you can find a circuit diagram for that, just to copy those two elements? I have found those functions to be really quite useful. That meter is still available elsewhere, but the price has shot up ! B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch. Last edited by Bazz4CQJ; 27th Dec 2018 at 2:41 pm.

27th Dec 2018, 2:48 pm	#3
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Homebrew battery tester ideas? I have got a Maplin digital one with a battery test function. The ball park figure is 33ma and 18 ma for 1.5V and 9V.

27th Dec 2018, 3:14 pm	#5
mickm3for Heptode Join Date: May 2015 Location: Chatham, Kent, UK. Posts: 964	Re: Homebrew battery tester ideas? Hi resistors =1.5v 5.5 ohms and 9v 360 ohms checked on a pcb from said meter hope this helps Mick

27th Dec 2018, 3:31 pm	#6
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Re: Homebrew battery tester ideas? If we are on about battery voltage under load, it's going to need "nihd" and "dry" battery positions on the switch to account for the different chemistries, also "9v" ni-mh are usually 8.4v. A good 1.2v ni-mh should allow at least 250mA to be drawn without voltage sag. __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

27th Dec 2018, 4:48 pm	#7
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	Re: Homebrew battery tester ideas? Don't forget about NiCad ,which are about 1.2 per cell . I've thought about something that I could load a cell with and watch on a DVM , but on reflection this project becomes more like the childs swing one.

27th Dec 2018, 5:34 pm	#8
Guest Guest Posts: n/a	Re: Homebrew battery tester ideas? It is very hard to tell the state of charge/left capacity of a cell with a voltmeter, all you can do is load it and hope for some volts. This will not indicate how much is left, may as well use the item they are in until it stops working, then replace. Easier to have spares in stock. The dear MT2017 does a good "is the cell/battery still alive enough" job as would a 'normal' meter with a bit of a load, I like them so much I have three.

27th Dec 2018, 6:13 pm	#9
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Homebrew battery tester ideas? You used to be able to buy cheap little portable battery-testers that had a meter [one of those 'edgewise' types often used as record-level meters on cheap cassette-recorders] that was simply calibrated red/green to indicate bad or good. Similar things are still available for a fiver or so - google "rolson 28101"

29th Dec 2018, 7:56 pm	#10
saddlestone-man Hexode Join Date: Mar 2009 Location: Cirencester, Gloucestershire, UK. Posts: 391	Re: Homebrew battery tester ideas? Hi Pete I had a similar idea for a project then realised that life was too short and family members were unlikely to search around for the missing test leads, etc and so I invested a massive £3 or so for a 'Universal battery tester' (made in China of course) from ebay. The analogue version is only £2.70 post paid now. It's so easy to use that the grand children check batteries for me. There's also a digital version for a 50p or so more money, but you have to look on the back to work out if your battery is good or not, rather than look at the coloured bands on the analogue meter. You soon get to know if a battery is good or not by comparing where it is in the coloured bands compared to a fresh one. I guess rechargable batteries are trickier, but most things that you put them in (cameras, tools, etc) tell you when they are low, and you can always pop them onto the charger that you have to have anyway and it will indicate the state of charge. Photos of my tester attached here so you can see the loads it applies to 1.5V and 9V batteries. best regards ,,, Stef Attached Thumbnails

29th Dec 2018, 8:14 pm	#11
saddlestone-man Hexode Join Date: Mar 2009 Location: Cirencester, Gloucestershire, UK. Posts: 391	Re: Homebrew battery tester ideas? Just taken a look at the rolson 28101 and I see that it also tests bulbs and fuses. Very useful. Of course it needs a battery itself so that's one more potentially (no pun intended) to worry about. Best rgds .... Stef

29th Dec 2018, 8:15 pm	#12
broadgage Nonode Join Date: Jan 2010 Location: North Somerset, UK. Posts: 2,129	Re: Homebrew battery tester ideas? For a single cell, I use a 1.5 volt torch bulb in parallel with a one ohm resistor, this draws just over an amp from a good cell and the brightness of the lamp is easily and quickly observed. For small 9 volt batteries I simply use a 6 volt 0.3 amp indicator bulb. No parallel resistor is needed, the 0.3a lamp current is a reasonably severe test for these small batteries.