AAA/AA NiMh battery capacity meter - has anyone seen such a thing?

I have lots of AAA and AA NiMh batteries which have been through quite a lot of discharge/recharge cycles. I have a tester which tells me if they're charged or not but I'd really like to check their actual capacity. Some of the AAA ones at least have very little capacity now but it's difficult to check.

I could rig up a simple resistor discharge with some sort of computer monitoring via an AtoD interface but surely someone out there must produce and sell such a thing for not very much.

Has anyone come across anything like this?

Reply to
cl
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Yes, I have exactly that in the form of a x4 x AA or AAA charger, discharger and capacity tester.

As a rule, whenever I buy new (AA/AAA) rechargeables I run them though the 'Test' routine and see how they fare against their rated capacity.

I think mine is a 'BC 700' although they may appear under different names.

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Cheers, T i m

Reply to
T i m

I think 7DayShop have the Uniross which I believe is the same hardware. It's much cheaper there, £18.99.

Reply to
cl

Yes, sorry, I didn't spot the price of that one till I looked again! Yes, the Uniross seems to do the same sort of thing but goes to higher currents.

This is the sort of thing I've got:

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But it too could be an 'uprated' version as I got mine a while ago now.

I bought one for a good mate who was regularly 'cooking' his batteries on a rapid charger and he uses his every day (but really just as a good charger).

Cheers, T i m

Reply to
T i m

Its called a torch bulb I think... There are two issues with rechargeable. Self discharge over time and capacity. To stop one from affecting the other you need a big drain that takes a known time on whatever battery type it is. Of course this takes no count of internal resistance which may make the actual current limit quite low when you use it in series with others. Finding the duff one in a set is quite hard, and there usually is one that dies first causing reverse charging by the others through the load and making it worse. In the end when I could see, I rigged up an open battery holder for four of the type I used, ni cads in those days, and put a plug on the other end that could run say, a cassette player via its adaptor socket. I'd then use thin probes to measure the voltage of each cell as they went down, chucking out the ones that went down first.

Brian

Reply to
Brian Gaff

That charger looks like a bargain at ?20.

Would it be worth getting that unit if you already have the Lidl Tronic charger?

It's based on the Ansmann Energy 8 Plus.

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chargers/energy-8-plus

Reply to
pamela

How I wish someone would come up with a charger that had extendible bays. By which I mean you could add on any number of very simple cell holders. The charger would look at the first set of cells, do whatever and go on to the next set.

That would allow you to have all your rechargeable cells nicely stored and kept at whatever charge level, discharge cycling rate, etc. you might want. Might need some way of indicating which cells are being processed right now, etc., but surely nothing particularly clever.

Sure it would still only charge up to four at a time - but that is enough for many of us!

Reply to
polygonum

Yes, I'd be interested to know - I've got the Tronic too.

Didn't know that!

Is the battery capacity readout of Tim's useful/accurate?

Reply to
RJH

I also have the Ansmann Energy * and 16 models and think they are great chargers. They will also do C and D cells of course.

As for accuracy on the BC 700 type units, I would have to say 'yes', they do seem to be pretty accurate.

By that I mean if I put a batch of 4 x AAA's that are marked as say

900mAh, if they are on spec the charger will typically report capacities around that value (+_ maybe 2% on good quality cells).

As I tend to do the full/ refresh test it can keep cycling the cells until it stops seeing an increase in capacity, it can take a while (a day / days), especially if you set the rates low so as to keep the temperatures as low as possible.

When testing both AA and AAAs I try to mark the tested capacities on the cells themselves with a fine Sharpie, that way I can use combinations (or the same make and model) that have similar tested capacities.

The tester can be very revealing ... both informing you of any cells that are being 'oversold' but also the condition of any sets of cells you are using as one 'battery'. I have been able to discard a few duff cells that I wouldn't otherwise have been able to isolate, giving the remaining cells a better life.

The BC 700 I gave to my (non technical) mate was to try to get him to understand that just taking any combination of (typically) different (marked) capacity cells and using them together wasn't a good idea. The idea was for him to test all his cells, mark them and then use them in matched sets (2's and 4's typically). I think he may have tested a couple but judging by the mix of cells I often see in the charger, I'm guessing he isn't using them as I suggested. At least he isn't cooking the cells like he was before in a rapid charger (as seen by the number of cells with split or crinkled skins). ;-(

Cheers, T i m

Reply to
T i m

It would have to have connections to each of the cells (as the better fixed bay chargers generally do) and I'm not sure if that would then bring in it's own issues (voltage drops over the leads affecting accurate voltage detection)?

There is no reason you couldn't 'cycle' a basic / lower rate charger over various sets of cell-packs, as long as they were all the same type etc (chemicals and capacity).

I love my Ansmann Energy 16 because not only does it handle up to 16 cells / batteries at once (12 x AA/AAA (or 6 x C/D) + 4 x PP3) it charges them slowly and individually. There is nothing more rewarding than buying a set of 12 new AA's, putting them in the charger and seeing them all indicate 'charged' at similar times. Take an old batch of 12 that are supposed to be the same and you would be surprised how much difference there can be in the finished times.

Put the quickest cells in the BC 700 and that generally confirms under (marked) capacity.

On the subject of charging multiple targets, I built a 12V charger / switcher designed to maintain up to 4 x 12V Lead acid batteries as typically found on 4 motorcycles. Some of these intelligent chargers (line the Opitmate series) ...

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... can be quite expensive and so it would be quite costly to have 4 off to cover 4 bikes. So this solution switches the charger around as many of the 4 outlets have batteries on the end (so you don't waste a 'slot' when a bike is disconnected) and you can set what period it stays on each (6 - 48 hours or so).

Cheers, T i m

Reply to
T i m

There are 10 bay chargers around which don't cost all that much.

Reply to
cl

I count 3 chargers, so far. Are you building a collection? :-)

I can never work out quite what logic is used by the Lidl/Ansmann charger. Sometimes it drains the cell and sometimes it tops them up. Do you know what the difference is between Refresh and Pre-Charge in the Ansmann 8 instructions below?

================ BATTERY QUICK TEST

After inserting the batteries, the state of charge is displayed: LED green: capacity over 80% of the nominal capacity LED orange: capacity between 25% and 80% of the nominal capacity LED red: capacity lower 25% of the nominal capacity

After 5 seconds, if the batteries are not removed, the unit switches over to automatic refreshing/charge mode.

LED INDICATORS / CHARGE MODES

LED flashes red/green "Refreshing" -> Refresh mode LED flashes green "Pre-Charging" -> Pre-charge mode LED lights red "Charging" -> Fast charge mode LED lights green "Ready"? -> battery fully charged/top-off or trickle charge mode LED flashes red "Error" -> faulty battery or alkaline battery detected ==============

It's smart that it can cycle until no more capacity is detected. Presumably this is for each individual cell.

If you test for actual compared to advertised capacity then doesn't that presume there's only one standardised end-voltage as a cutoff point but I'm not sure if that's the case.

Your friend reminds me of a charger I had which didn't switch off soon enough and the cells would often get very hot. I decided to cool the finished cells by wrapping them all over in kitchen foil because aluminium is a good heat conductor. I wondered why they didn't seem to cool down! I'm probably lucky the cells didn't explode.

Reply to
pamela

Erm, yes. I probably have more like 20+ chargers here of all different types inc the ones I've mentioned and bigger car, Electric Scooter (24V lead acid and 26V Li-Ion) plus model car / boat / aircraft chargers etc. But then I have spent most of my life playing with batteries, RC models and even my road going electric car so it's not surprising. ;-)

I think it (well mine do) drain first, it's just if they are already pretty flat that won't take very long?

Ok, seen that and it makes sense.

Is that the discharging phase?

Working out how to best charge that cell?

Bulk charge phase.

As it says, trickle charge mode.

Duff. ;-)

It is but I think it's more pertinent for NiCd than anything later.

Yup. I don't think I've still got any chargers that charge 'packs' other than those found inside equipment (where the battery stays in the device) or the very low current jobbies for slow charging RC gear.

I'm not sure if it can detect the difference between NiCd and NiMh but may just look for the drop in voltage that normally occurs around the fully charged point (negative delta V, NiCd) or that plus other factors for NiMh (like temperature).

My Ansmann 'Energy' chargers can still cause a (typically 'iffy') cell to get quite hot but any that do I put on the BC 700 and let that determine what's going on.

If you wrapped them tightly it may not have made matters much worse. Wrapping them loosely would be like putting them in an emergency blanket. ;-)

I think once off charge they wouldn't have got much hotter ... assuming you didn't short them out with the aluminium foil that is ... ;-(

Cheers, T i m

Reply to
T i m

Looks more like it's based on the Ansmann Powerline 4 Pro or Powerline 4 Lite.

Reply to
Andy Burns

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I've managed to 'kick start' error reading AA/AAA batteries using a cheap 'dumb' charger. Batteries seem to recover fine. I think they discharge to such a point that the smart charger can't do anything with them?

In fact I've successfully done this when the smart charger failed with a car battery recently.

Reply to
RJH

You don't need a second charger, you just parallel connect the "duff" one and a charged battery together for a second or two.

If it doesn't work after a couple of goes chuck the battery away.

Reply to
dennis

Had that with the Lidl one on once-used, not fully discharged, Eneloop Pros. Used the 7-dayShop 'dumb' charger for a few minutes and then the Lidl one was OK. BTW, my Lidl charger packed up after 2 years and 10 months. e-mailed, sent relevant details, got a new charger. Felt slightly guilty - until I realised I'd just saved about 10 Wetherspoons pints worth.

Reply to
PeterC

I think in this (error) case is more the 'I don't seem to be able to get it to full charge in the time set' more than the 'I'm not going to start charging because I don't like the battery for some reason'.

Whilst I have had some cells that initially appeared 'dead' recover to the point where they seem to work again, I think in most cases they continued to be duff in time.

Like, the previously considered 'duff' cells works ok when you are using the pack at a reasonable rate and regularly but if you leave them for a while, that same cell will go bad again.

I think I can depend on how 'smart' the smart chargers are. Like the later Optimate (12V) chargers first test to see if there is a voltage there (and there may be a minimum threshold but if below that the battery is probably a goner anyway (especially with Lead Acid) and then will do all sorts of high voltage pulsing and other cycle - test

- cycle type processes in it's attempt to recover it. Now, whilst I have pulled a few batteries back from the brink with chargers like that, I'd say they would generally be either very low capacity or high levels of self-discharge after that.

I now look upon lead acid batteries (particularly) as straight consumables.

Yes, some of the more basic smart chargers do sometimes need a bit of a helping hand to get started if the battery terminal voltage is below a certain threshold. I do what others here have mentioned and either (carefully) put a good battery in parallel for a while or use my bench PSU on a lowish current but a high voltage (well, sub 30). ;-)

It's interesting to see the current climb and then the voltage drop as the battery 'wakes up'. ;-)

The thing with the small individual cell charger, discharger and calibrator is you can mark the cells with the outcome of the tests and it's then very easy to spot the runt of the litter and discard it. If you have say 12 identical cells and they can be used in 2's and 4's but taken randomly from the pool, you never know where that weak one or two cells are and they will make the whole set (they are with at the timer) appear bad and will be being made worse themselves at the same time (reverse charging etc).

The 'You can manage what you can measure' saying is very appropriate here. ;-)

I would like such a charger for the C and D sized cells but I'm guessing it would be pretty expensive (and to be fair I don't have that many C/D's, compared with AA/AAAs anyway.

Cheers, T i m

p.s. When I designed, built and raced my electric motorbike (endurance racing rather than speed) I was able to borrow a batch (10 or so) identical 12V car batteries from my local car spares place. I put them on my test jig one at a time and measured the reserve capacity, finally picking the two batteries that had the highest capacity and the most matched characteristics (as they were used in series on 24V).

Reply to
T i m

I have two (sometimes three) chargers of varying degrees of smartness, they all use deltaV to detect full charge. I often find that some batteries won't start charging in one charger but will start in another, the trouble is that there's no consistency as to which charger works.

Reply to
cl

I meant it's the Lidl charger, not the 7dayshop one, which looks like the Ansmann Energy 8.

Reply to
pamela

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