Rechargeable batts - NiMH charging?

[Reeve]

<font color='#000F22'>Oh was it.

In my defence, I'd saved that paticular piece of info on notepad for later reference, without the details of the source.

[gblades2]

Originally Posted by [b

Quote[/b] (Mdemon @ Feb. 07 2004,22:58)]Thanks all.  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.  Negative Delta V or something!

That is correct. However the main point is that as the original charger takes 14-16 hours it is a permanent trickle charger. All batteries can stand being charged at this rate continuously.

[Mdemon]

Forgiven mate - glad to know someone was paying attention!

I've seen the torch link as well - very good. &nbsp;I am trying to find out how much the IP68 waterproof connectors cost for the BIG torch I'm working on... (Retina-burning...)

HID. &nbsp;Interesting. &nbsp;I looked into making ballast etc and it was more than I could do. &nbsp;To be honest, with the bulbs the price they are, I would rather spend money on the torch body and good batteries than on delicate bulbs. &nbsp;If I flood/drop my halogen, the most I lose is a few quid. &nbsp;Then I get a good excuse to go round and pester Anne...

Took the plunge and spent the cash last night - damn late night drinking.... &nbsp;Bought a NiMH charger for £18 too. &nbsp;I hope the tagged ones fit. &nbsp;As Doug says, &quot;you get some more next week!&quot; A philosopher if ever there was one...

For the record, and using the NiCad figures supplied by Mares, I should get the following (@12v):

50w NiCad 4.5Ah = 70mins NiMH 9Ah = 105mins
75w NiCad 4.5Ah = 51mins NiMH 9Ah = 77 mins
100w NiCad 4.5Ah = 33mins NiMH 9Ah = 50 mins
150w NiCad 4.5Ah = 14mins NiMH 9Ah = 22mins

So I should get 2 dives out of a 50w easily. &nbsp;However, NiMHs perform better than NiCads, so I should get better than the figures above. &nbsp;Is it worth twice the money? &nbsp;Well, if I get into difficulty I won't have to worry about light running out. &nbsp;And it works fine on dry land. &nbsp;And it could be adapted to HID if they ever make HIDs bright enough and cheap enough to compare.

The Beast MkII will run at 24v... but that's another thread...

Thanks for your help all - I'll post again once it all arrives and let you know how it goes. &nbsp;

[Mdemon]

Oh, the £18 (ex VAT) Universal NiCad/NiMH charger allows you to set the voltage and the charge rate (up to 1000mAh - I'll need 900mAh), it fast charges and then cuts to trickle once they're full. &nbsp;LEDs tell you what's going on. &nbsp;Charges any battery pack and up to 10 cells at a time.

http://www.powerstoredirect.co.uk/erol.html#270x0&amp;&amp;

[nickjb]

If you want a top notch charger then check out the &quot;pro peak&quot; range.  Mine will fast charge up to about 6 amps, has intelligent control and runs off a car battery for field use.

Edit:
Just found a good link while surfing around:
http://www.gmmodels.co.uk/acatalog/FieldChargers.html

[Mdemon]

That is the mother of all charger sites!

B*gger. &nbsp;I should have got one of those fast charge babys.

But here's the thing... &nbsp;Is shoving 6 Amps into a rechargeable a good thing? &nbsp;Will it reduce their life? &nbsp;These things are a tenner each... &nbsp;Any thoughts?

I like the 12v/240v option too - would work in a car/on a dive boat... (or are they 24v?)

[nickjb]

Some cells are designed for fast charging some aren't. &nbsp;The ones I have are designed for charging at max 2 amps but as I have two sets in parallel I charge at 4 amps.

As long as you cut the charge off at the right point (just as they start to warm up and the voltage starts to drop) then the cells will be fine, hence the need for a clever charger. &nbsp;You just need to have the specs for your cells. &nbsp;Max charge current is usually related to capacity so the larger the cells the more current you can pump into them.

I'm thinking about some of those expesive batteries for my video light, but £120 for a battery pack is pushing it a bit

Nick

[Mdemon]

...especially when an SLA Yuasa @7Ah, 12v is only £20!

Those NiMHs are stupid money.

[nickjb]

You shouldn't discharge an SLA more than half empty if you want it to last, NiMH will give the quoted capacity in actual use. &nbsp;They are still expensive though