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DIY Battery Monitor Tests Electrical Capacity of Disposable Batteries

Even if you have no intention of building this well-executed battery meter, the results creator Denis Hennessy got from his tests of over 100 battery brands are an interesting read.

Hennessy was underwhelmed by the lack-luster information displays and packaging provided about batteries:

I needed a couple of AA batteries and found the display at the supermarket where they were all arrayed. Normally when I’m shopping in the supermarket, I tend to look at the price/kg or price/l when comparing similar products. In the case of the batteries, there was no such indicator. Fine, I thought, I’ll work it out myself. I grabbed a few different makes and scanned the packaging for some measure of their capacity. Nothing. Not a single one of the batteries had any indicator of how much energy they would provide. Instead, they all had terms like ‘PLUS’, ‘SUPER’, ‘ULTRA’ and of course had wildly differing prices. So, I decided that it was time for an experiment and bought one pack of every type I could find.

To that end he build an Arduino-driven battery meter and went on to test over 100 brands of batteries to see exactly what kind of energy they would output and for how long. Hit up the link below for a full run down of his process as well as his results.

Measuring Battery Capacity with an Arduino [via Wired]

Jason Fitzpatrick is warranty-voiding DIYer and all around geek. When he's not documenting mods and hacks he's doing his best to make sure a generation of college students graduate knowing they should put their pants on one leg at a time and go on to greatness, just like Bruce Dickinson. You can follow him on if you'd like.

  • Published 04/16/12

Comments (11)

  1. LadyFitzgerald

    I’m amazed by the number of people who still use dispopsable batteries. A good quality prechargeable is, by far, more economical in the long run. I use Sanyo Eneloops in my devices that use AA and AAA batteries. I also make it a point to use devices that use AAs and AAAs whenever possible.The only things I have that do not use AAs or AAAs are my truck, netbook, watch, and cell phone. If (I know, a HUGE if) I could find ones that did, I would be all over them.

    Regular NiMH rechargeable batteries will self discharge in 4-6 weeks, meaning one has to constantly be recharging them. Prechargeable batteries are a newer class of NiMH that will hold up to 80% (or more) of their charge for at least a year, meaning spare batteries do not have to be constantly recharged to keep them usable. Since rechargeable battery life is measured in the number of discharge and recharge cycles they can take, battery life is increased by a factor of over 10. The prechargeables do not have as much ampacity as conventional NiMHs (which, in turn, do not have as much ampacity as alkaline or lithiums) but, since they are rechargeable, all one needs to do is change them out a little more often. I’ve never found that to be a problem and spares do not take up much room. Another advantage of prechargeables is they are less prone to leakage over time. I’ve been using Eneloops for several years and never had one leak. I’ve had alkalines leak even when setting in an unused device that shouldn’t have discharged them. When I get a new device that comes with alkalines included, I give them to someone who will use them up quickly and, instead, use Eneloops in the new device.

    Sanyo Eneloops will charge up to 1.5v but, during the first week or two, will self discharge down to 1.35v. They then hold that voltage for up to a year in storage. I’ve seen people complain that prechargeables will charge up to only 1.2v but that hasn’t been my experience with Eneloops.

    One thing to keep in mind with all rechargeables: heat kills batteries. The faster one charges a battery, the hotter it will get. Fast chargers literally cook batteries. I rarely charge mine at a higher rate than 200mA. Even that rate will noticeable warm a battery but that’s the lowest setting my chargers have (and I doubt anyone makes a charger that charges more slowly). I have a couple of LaCross smart chargers that regulate the charging rate, tapering it off as the battery approaches 1.5v, then drops to a trickle when it is fully charged. In the three years I have been using Eneloops, I’ve yet to have a battery fail or show significant signs of aging.

  2. LadyFitzgerald

    Btw, I know disposable isn’t spelled dispopsable. Pity we can’t edit after submitting.

  3. r

    -Lithium are best for things that use large & short bursts of energy : like digital cameras
    -Alkaline are best for things that use little power : like remote controls
    -Rechargeable are good for things that use energy for long periods of time : like electronic toys

  4. Frank

    interesting – fast charging cooks batteries ? maybe that’s why my NiMh rechargeable AAs no longer work in my digital camera. Not sure because I tried some brand new pack batteries and same problem from first use.

    I understand disposable batteries typically start out at 1.5V while rechargeables are more like 1.2V – perhaps for that reason my camera manufacturer, Canon recommends against rechargeable batteries.

    The other uncertainty is I used rechargeables for ages before my camera suddenly refused them – so anyhoo – I bought an $8 box of like 50 disposable AAs, and just back from 2 weeks overseas holidays and hundreds of photos and videos taken, I only probably emptied about 10 batteries – tho’ not sure as I take them out and try again later and they seem to refresh – anyway at this rate, compared to the $20 charger and $16 pair of AA NiMh rechargeable batteries, cheap disposable batteries at about $1 seem to be more cost-effective for me !

  5. LadyFitzgerald

    @ Frank. Canon recommends against rechargeable batteries? Curious. Page 34 and 36 of my Canon SX10 IS camera manual lists an optional battery charger and battery kit that includes a charger and four NiMH AA batteries (the camera uses four AAs). The batteries are also available separately, per the manual. Page 8 of the manual for my Canon 430EX II external flash also states that NiMH batteries can be used (it use four AAs).

    I use Eneloops exclusively in both of my cameras and flash (I also have a Canon SX130IS that uses two AAs that I keep in my purse; I don’t have the manual handy but I’m pretty sure Canon also sells a charger and batteries for it) and they work just fine.

    If you are paying $$16 for two AA NiMH, you are being ripped off! A four pack of Eneloops cost $10.89 at Amazon. Shipping is free on orders of $25 or more (I keep a wish list of items I want or need but do not need immediately to pad out orders to get to the $25 minumum).

    I spent more than $25 for my smart chargers (LaCrosse BC-700U and BC-900U; although I didn’t need the higher, battery cooking charge rate of the BC-900U, it came with a nice soft case that has room for both chargers and their wall warts, and 16 each of AAs and AAAs, all in cute little cases of four). They also measure ampacity, recondition NiCads, etc. Each charger will charge up to four batteries, each one independently of the others, and the display shows each battery simultaneously (essentially, four independent displays). Voltage, charging rate, etc. are displayed. A good charger will go a long way toward making batteries last longer.

    I see the 1.2v figure for NiMH thrown around a lot, but, as I said, my experience has been the Eneloops settle in at roughly 1.35v. Even new ones come out of the package at that voltage although I still charge them just to make sure they have a full charge. After the initial drop from 1.5v to 1.35v, the eneloops maintain a fairly flat voltage during use then drop off quickly when pretty much discharged.

    @ r. I use Eneloops in my cameras, remotes, a medium sized Casio keyboard, flashlights, my e-book reader (it’s a Jetbook Lite, an odd duck that uses four AAs), wireless computer mice (or mouses, if you prefer; I don’t want to get into that controversy), alarm clock, wall clocks, etc. All work just fine on them.

  6. T

    Call me old fashioned, but I use the 10A DC scale on my volt-ohm meter to test batteries. Just put the battery directly across the meter leads, plus to plus, negative to negative. Any disposable battery sized AAA to D will read 2A (or more) if it has “good” life left in it. Don’t leave the battery on longer than needed to get a reading as this is a “destructive” test and does draw a little capacity from the battery. But faced with a drawer full of unknown batteries, this method will find the good ones very quickly.

  7. kf Lee

    where can I found info on prechargeable batteries. Google search only lead me to rechargeable!

  8. LadyFitzgerald

    @ kf Lee.

    http://www.stefanv.com/electronics/low_self_discharge.html

    http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery (granted, not the best source in this case)

    http://en.wikipedia.org/wiki/Nickel%E2%80%93metal_hydride_battery#Low_self-discharge_cells (better source but outdated on battery capacities)

    You can also do a Google search using “low self discharge nimh batteries” (without the quotes) fora search word.

    I saw at least one review that claimed that prechargeables weren’t cost effective but that contradicts my own experiences. My Eneloops have paid for themselves over alkalines many times over and are still going strong. I wonder if the tester used too high of a charging current?

  9. LadyFitzgerald

    Forgot to mention…many chargers can’t recharge a battery that has dropped below 1.0v (the circuitry doesn’t recognize it for some wacky reason) so many otherwise good batteries get tossed. The easy cure is to take a second battery of the same size that has a full charge, hold them side by side, then place a coin across each end so the terminals are shunted together. What you are doing is pulling current from the charged battery to the discharged one to build up the charge enough to enable the charger to “see” the battery. Depending on the state of discharge, it can take anywhere from a few seconds to a minute. I have rarely had to do this but it has saved a few batteries for me.

    Just for excrement and merriment, I grabbed my VOM and put it across a AAA that had been setting in my battery/battery charger case for a while (a few months) and it showed 1.32v.

  10. LadyFitzgerald

    @kf Lee. I posted some URLs with infor on prechargeables but it’s been awaiting moderation all day. You can do a Google search for yourself using “low self discharge nimh batteries” (without the quotes) for a search word.

  11. LadyFitzgerald

    I guess whoever is supposed to be moderating this thread is out to lunch.

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