Rechargeable batts - NiMH charging?

[Mdemon]

I bought a Mares Arturo 12v torch on ebay for a few quid.  It takes 10 x NiCad 4.5Ah D cells and comes with a charger (24v 450mA output).  Instructions say the charge will take 14-16hrs. (Charger part number is NC 4-510. )

So, I want to put NiMH cells in.  And I want to put bl**dy expensive 9.0Ah NiMHs in!  The question is, a) would the charger that was for the 4.5Ah NiCads charge the NiMHs and (MOST IMPRTANT!!!!), do these sorts of chargers have a cut off or do I run the risk of frying £££-worth of batteries?!!!

The Mares website sucks.  No technical data whatsoever on their products.    

Any clues?

[Dr Stevil]

Try Maplin's I reckon you're better off asking an electrical supplier

[Reeve]

<font color='#000F22'>Nimh &amp; Nicad require different chargers, or more importantly different charging features. It is possible to use the same charger as long as you switch between battery types. A typical example are the 4AA rapid charge chargers that have a switch on the front for desired battery type.

Most but not all are intelligent chargers that'll fast charge then once charged trickle charge, there'll be a limit say 24 hrs not to damage batteries.

One question to ask yourself is if the current batteries arn't knackered why bother, and are the new batteries compatable with the electrical circuitry. You may find you fry your resister. There's a cost to this which may not be worth it. Use the new batteries to build an unbilical HID.

Gareth
(p.s) I have plans to build a HID, £5 for the plans

[gblades2]

If the charger takes up to 16 hours to charge the nicad batteries then this is a slow charger and the batteries can be left on charge at this rate indefinetly.

You can therefore put 9AH NiMh batteries in the torch and the charger will work fine but will take 28-32 hours to charge.

[steve-k]

<font color='#000080'>if it is an unintelegent charger you cant swap batary types


you can buy standard nimh chargers that will do the job fine and wont cook your expensivenimh cells

i have herd that some bulbs dont like nimc cells and blow (due to the high initial voltage) so if yours blows dont replace with the same make

i have the greenforce 12v with nimh cells, thay will sell you all the spairs you want, even the charger, may be worth a ring
http://www.lumb-bros-das.co.uk/acata...e_Torches.html

[Dave Crampton]

<font color='#000080'>I've just spoken to a collegue, who said the charge cycle for these two types of batteries are very similar. He recons you should be able to charge the Nicol Metal Hydride Batteries in the Ni-Cad charger. He did say to watch the batteries periodically on first charge to ensure they don't get too hot. If they get very hot to touch they should be OK but if they become so hot that you actually burn yourself then stop charging. But from the charge current of 450mA they should not get very hot if at all. As the charge current is very low this would indicate a trickle charge type, so there is little chance of frying your batteries.
Gblades is right about the charge cycle time. As the newer batteries are twice the capacity they will theoretically take twice as long to charge.
With respect to Reeve's coments about frying your resistor, My collegue says this should not happen. The only difference between the two batteries is the capacity. The voltage and current should be similar (you know 1.3 volts as apposed to 1.5 volts say) and this should have no bearing on the resistor as the only difference is the capacity or life of the charge. The new batteries should last longer and take longer to charge as you already know.

Try it and let us know how you get on. You do know that before first proper use you should charge and discharge a couple of times. This is to bring the batteries up to top efficiency as they will have been stored for a while before they were sold and will as I said require a couple of charge and discharge cycles to get them back to shape. I found with new batteries you can discharge them in your torch whist its weighted down in a large bucket of cold water to stop your torch over heating and possibly melting parts of the casing.
These batteries have approx 1000 charge cycles of Life time, i.e before they expire. To get the best out of the life of your batteries, ensure they are discharged (not fully as this could cause damage to them) but very near to fully before charging them again. I don't know a lot about NiMH barreries memory but charging and discharging properly will help to prolong their working life time. Memory by the way is where you charge the battery up before its fully discharged and it gradually starts to have a lower output voltage than it would do if maintained properly, i.e. proper charge/discharge.

Good luck.

[Mdemon]

Thanks all. &nbsp;I was concerned since I'd been told that once NiMHs are charged, continuing to charge will quickly kill them - so you need an intelligent charger to switch to trickle charge. &nbsp;Negative Delta V or something!

These batteries are nearly a tenner each, so I think I'll chicken out and buy a charger for £18. &nbsp;Seems a reasonable insurance policy &nbsp; &nbsp;...though I hate spending this much cash... &nbsp;

Still, cheaper than HID!

[Reeve]

<font color='#000F22'>not if you make your own see - make your own HID for some ideas. Theres also a book available US side that provides more info. another DIY link is DIY Projects  For cheap (apparently effective) bulbs see bulbs and ideas

Finally taken from another thread - The usual, plus 75w, 85w, 100w and (wait for it) 150w! And for those of you into retina burning, there is a 250w, 24v call Anne Pengelly at Stage Electrics in Exeter (01392 255868)

hope this helps.

gareth

[Mandlebrot]

Oh by the way NiMH's have v.little memory effect and some leading bat engineers/manufacturers recommend that they are kept in better condition by being topped up rather than the complete discharge/recharge cycles that NiCad's need.

[Doug Parker]

Originally Posted by [b

Quote[/b] (Reeve @ Feb. 07 2004,23:59)]

Finally taken from another thread - The usual, plus 75w, 85w, 100w and (wait for it) 150w! And for those of you into retina burning, there is a 250w, 24v call Anne Pengelly at Stage Electrics in Exeter (01392 255868)

hope this helps.

gareth[/quote]


Well done Gareth, take his own thread and use it against him.