Otto Bock myoelectric arm - What does the Otto Bock battery contain? Battery replacement by 4 x AA rechargable cells (Ni MH, 2500 mAh)

[Article in German]

Otto Bock myoelectric prostheses are sold at staggering prices, parts are mind numbingly expensive. The battery - rechargeable - is a particularly expensive item (~700 USD) and my old one that was included in my own parts was out of order for some reason.

Now, I was not interested in getting overpriced electronics so as you can see on my test socket, we fixed the problem.

This is the original Otto Bock battery (at least as original 'Otto Bock' as it ever gets). It is sold for around 700 CHF, a recharger costs about just as much. And that is a big problem because it is what I personally call crappy old technology.

So, what does the skin colored miracle box contain?

It is hard to get it open without damaging the beautiful plastic. 'Quality for life', eh. So what do we contain? Surprise surprise, nothing but el-cheapo rechargeables, five parallel Varta 6V 260mAh NiCd (yawn!) delivering ~1300 mAh (street price around 10 USD, Otto Bock sales price around 700 USD).

The prosthetic hand indeed runs with 6 V DC. So I figured that it would be an easy feat to replace this hugely expensive setup of the jokesters that thought up that pricing scheme and that does nothing else than providing Varta type electricity. I figured we could easily use some cheap stuff that also does nothing else than providing electricity itself.

For that, we hooked up four regular AA rechargeable cells (Ni MH, 2500 mAh, delivering some 2500 mAh as the batteries are serially linked) on my experimental test socket:

The hand works fast and well with the rechargeable batteries, no doubt about that:

Side by side comparison:

Battery comparison Battery type total V total mAh Price
Otto Bock 5 rechargeable Varta 6V 260 mAh cells, NiCd (how bad!) 6V 1300 mAh ~700 USD
Any brand you see fit
4 rechargeable 1.2V, e.g. 2500-2800 mAh cells, NiMH or whatever you like 6V 2500-2800 mAh

or whatever you can get

~12-30 USD

If you prefer the Otto Bock batteries, you now know better what you got.

For everyone else: You read it here first ;) Have a nice battery :) Now we can go buy cheap or luxus class batteries, get AA batteries or AA rechargeable cells, and recharge as many replacement sets as we like while wearing the arm. And: Conrad Electronic sells such an AA-battery frame.

If I was responsible for a health or disability insurance and if I would find out that Otto Bock or other manufacturers sell such cheap batteries at such prices, I'd derail and get active right here and now and file a formal complaint.

Even if Otto Bock also sells Lithium-Ion-Technology for their batteries these days, the same principle applies: make sure they show you the insides of one of these batteries first and see whether you can find these elsewhere cheaper. After all, most of these are produced by an OEM somewhere and so they will necessarily be available elsewhere at a mere fraction of the cost. - Me personally? I'm just after cheap electricity :)

To understand the implications of such observations you should consider that Otto Bock makes money in exactly this way and spends it to build design architecture at Berlin's most prestigious - and obviously very expensive - location: they built the Science Center Medizintechnik. By that they use public and insurance money to generate massive income for themselves rather than using technology for the benefit of the disabled. The downside is that at such prohibitive prices, amputees can only get a minimal amount of batteries paid (imagine wasting 2100 USD for three lousy battery packs that are not worth more than 30 bucks) and due to that, amputees end up remaining considerably restricted. On top of that, this is most definitely not a free market.

Obviously, these guys are extremely clever in packaging stuff to make it look neat. This means that for the future:

  • Otto Bock and other manufacturers' parts will have to be scrutinized very closely as to parts and function. Try to go way past the first impression.
  • The parts will be tested as to durability, function, price/performance and safety.
  • Alternatives will be used to conduct the evaluation rather than doing a 1-object-appreciation.

Spending more money for power supply does not necessarily have to be a bad thing. But for 700 bucks, I'd expect something like a well shielded little Plutonium energy source that could power that arm for 5 years flat, because for about 350 USD one can actually get fuel cell technology:

Cite this article:
Wolf Schweitzer: - Otto Bock myoelectric arm - What does the Otto Bock battery contain? Battery replacement by 4 x AA rechargable cells (Ni MH, 2500 mAh); published 25/01/2010, 03:48; URL:

BibTeX: @MISC{schweitzer_wolf_1638593770, author = {Wolf Schweitzer}, title = {{ - Otto Bock myoelectric arm - What does the Otto Bock battery contain? Battery replacement by 4 x AA rechargable cells (Ni MH, 2500 mAh)}}, month = {January}, year = {2010}, url = {} }

1 thought on “Otto Bock myoelectric arm - What does the Otto Bock battery contain? Battery replacement by 4 x AA rechargable cells (Ni MH, 2500 mAh)

  1. With LipoFe batteries becoming safer than standard Lipo.. and considerably lighter than Nicad AA's - one could use those.
    One of the complaints that I read about is weight in limbs.

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