How can I charge disposable alkaline batteries?

[teknuts]

I would like to make my own circuit to recharge alkaline batteries. I am interested in doing it from a small solar panel. I understand rayovac now sells rechargable alkaline batteries. I checked out the online msds for alkaline and rechargable alkaline batteries and they are very similiar except for a small amount of silver. Does anyone have any circuit ideas?

[Chris Smith]

You can only re-charge the rechargable type. The other type is a "chemical break down" type, which is not reversable. <p>Think of it like a match, once your light it, you cant make it back into wood and a match head, with out a miricle or a million bucks?

[Michael-love-electronics]

You can recharge the rechargable types by connecting them to a higher voltage source, but the source must be DC.

[L. Daniel Rosa]

From what I've seen, I'm lead to believe that disposable alkalines are 'charge extendable', but once they're dead they stay that way (much like rechargable alkalines). The disposable ones are (so I've heard) engineered to spend their electrodes as they discharge, so that there isn't enough to re-form them on while recharging. I didd once have a device for 'charge-entending' on disposables, but I wasn't impressed by their performance.<p>IMHO, NimH cells (not to be confused with the rooms in one particular sanitarium) are an excellent option. If you like you can re-invent NiFe cells, they're pretty cool sounding (from what Ive read on them).

[josmith]

I was one of the suckers that bought rechargeable alkalines when they first came on the market. I’ve found this type of cell, even when charged with the specially designed charger, have about one half the initial service life of a regular alkaline and much less after recharge. The claim was 25 recharges. The reality was much less.<p>My idea is to use proven products like ni-cad nmh or gel-cell.

[bodgy]

I could throw a spanner in the works here and say that in the 70's (when companies and people were not trying to make a cheap buck off each other and people were expected to at least attempt to use their own reasoning powers - soap box off), one of the very large battery producers, would if you spoke to the engineering department send a nice little circuit on how to recharge standard throw away batteries. <p>It can be done though there are a number of drawbacks and if done incorrectly then the chance of making your own weapon of immediate destruction would be much higher.<p>However the battery life is much shortened, not all will recharge and you need to recharge the batteries of the same Amh at a time.<p>Colin

[Chris Smith]

If all you want is a few extra minutes life, toss them in the oven at "warm" setting and they will live again?<p> However, the chemical process can not be reversed with any significance, any more than you can reverse a match, once lit. <p>It is a chemical process at work here, and thus not reversible with out dissecting the battery, and re filling it anew.

[teknuts]

Does anyone know where a schematic of circuit that Bodgy speaks of may be?

[HomeBrew]

You have to be very carefull when you try to re-charge any type of common Alkaline battery. They are not vented and can explode if the charging process is not controlled. At the very least,they will leak and damage your equipment. I have even seen the re-chargable RAY-O-VAC batteries leak after a few recharges. They re-charge pretty well as long as you don't drain them too much and re-charge early. But the leaking problem turned me off pretty quick.

[bodgy]

Well I have one, or a very ancient copy of EPE magazine when it was Practical Electronics 1990 or there abouts had the project - in fact I have the 4.5 transformer and most of the heavy duty resistors still.<p>Basically it uses half wave rectified mains at 4.5v so that the batteries are charged via a dropper resistor and when the low voltage mains reverses, the action stops the electrolyte from becoming polarised - not quite the right term, but my brain isn't firing today.<p>so MAINS -> TRANSFORMER-> A-->K [_R__] +Batt - Transformer return<p>Never was good at ASCII art. The batteries must not be totally flat and you must charge the same size cells - I'll dig out the schematic and refresh my memory. <p>I don't have a scanner so I can't scan it for you and EPE, even though the copy I have is not out of the magazine, probably would have a fit at the thought of it being copied.<p>Colin

[Dimbulb]

I have wondered if you could go in and stir up the goop there could be some advantage.