I have posted somthing similar before but I have a development and a potential soloution that I need the knowlegable to tear appart

I have a Hilti TE 6a 36v cordless
The batteries are dead
\New batteries cost £187.00 each
At work I have just carried out an emergency lighting maintaince
Changing alll the batteries.
I now have in my shed. 14 yuasa 12v 7AH batteries that have exceeded their legal back up life.
However I currently have no charger for them.

I was wondering ( for digging purposes)not me though!
could 3 of my batteries be rigged in series and would they run my drill.
could my 36v charger for my drill be adapted for charging the 3X 12v in series, without blowing up.
I also have a plastic battery thing that came with the drill .It is a battery case with a curley chord and a clip that would attach to a remote battery, say on a belt . its just for weight reduction on your arm.

so gents could it be done and would it be worth my time.
I dont care about the drilll as it is of no use to me for work now.

three 12v batteries in series on your drill will be fine

lead acid batteries require different charging characteristics to the metal hydride in the original packs - modifying the original charger would not be practical

cheapest way would be to charge them individualy with a car battery charger - this is not recommended - over charging will knacker the batteries

for a couple of quid you could knock up a regulator to use with a car charger to enable safe charging

alternative £15 should get you a cheap and cheerful dedicated sealed lead acid charger

Make sure all cables are of sufficient thickness to have a high enough current rating or you'll have various problems. Your batteries will not do a large number of cycles as they are probably the type used for standby applications. They don't like deep discharge, so try not to drain the last spark out of them during use! Then again if you have a reliable free supply this may not be an issue (other than an environmental one).

One big advantage of what you are proposing is that in really awkward caves you can split up the weight of your drilling system among several team members; bear this in mind when spending coin on any connectors etc.

Does it mention what type of batteries they are?

I, and a few people i know, have done exactly this using 2 sets of 10 1.2v ni-cad cells taken from oil rig emergency lighting. We use them with Bosch 24v gbh drills and i see no reason why an extra set to bump it up to 36v would hurt. You will certainly want to put some more hefty wires in than the ones that come attached (if its the same as mine). If you have 14 sets then it would be worth taking one apart and putting a few extra cells in to make it 38-39v. Hardly any more weight but a hell of a lot more power!

Hi

I'm assuming that the Yuasa batteries are Sealed lead Acid (they usually are). If so, yes they will work, but they will be heavy!!

I also assume that your Hilit works on Ni-Cad batteries

if so your charger will NOT charge the Yuasa's.

Lead acids need constant voltage charge, Nicads need constant current. using a Ni_cad charger on Lead acids is BAD ( = Very hot batteries, followed by explosion or fire )

Have you considered opening up the dead Hilti battery container and just replacing the cells themselves, you could probably do that cheaper than a new battery...?

the emergency luminaires from which you took the batteries should have an integral charger....

steal one of those :twisted:

Salty said:

the emergency luminaires from which you took the batteries should have an integral charger....

steal one of those :twisted:

Click to expand...

It will be a trickle charger though - take a looong time to charge

yeah, about 24 hours per battery.

better steal 3 8)

Andy f Is it possible to get replacement cells of a decent capasity
Im visualising 30 aa batteries!!!
but that would still only give me at best 2.5 amp hours

Sewer Rat said:

Andy f Is it possible to get replacement cells of a decent capasity
Im visualising 30 aa batteries!!!
but that would still only give me at best 2.5 amp hours

Click to expand...

Do you know if the batteries are Nickel Cadmium (NiCad) or nickelMetalHydride (NmHi) (It should say on the battery somewhere)

You can't get good batteries on the high street, except at Maplin..

http://www.maplin.co.uk

this lot also have good selection (GP is a good brand)

http://www.batteriesplus.co.uk

Are the original batteries "AA"'s?

AA's are not great as they have a maximum current handling capacity that makes them inefficient for high current applications. The high capacity AA cells are worst for this!

Better off with "C" or "D"cells (or better still "F" cells).

30 decent NiCd C cells would only be £90 or so. If you get "tagged" ones you can solder them together, which helps avoid losses at connectors.

NmHi are more expensive, but much higher capacity. More fussy about charging though..

I've never had much success with sealed lead-acid batteries - it appears that they don't like the vibration which results from being bashed about on the way to/from a dig. However, if you have a cheap source of these batteries then only getting a few trips out of them doesn't really matter.

I'd be interested to hear from anyone who has used NiMH cells. I've been unimpressed by the ones I have on the cordless tools in my garage but I've never tried 'big' ones on my digging drill.

My digging battery is made up from 22 'F' cell NiCads. I use a TE5A (24V nominal) and the extra couple of cells really give it some whizz. Personally, I've always found that you get what you pay for with batteries, so I tend to go for the more expensive options. I believe it's worth saving up for some really good gear rather than go for the cheaper options and then have it fail on you at the sharp end.

Nick.

nickwilliams said:

I believe it's worth saving up for some really good gear rather than go for the cheaper options and then have it fail on you at the sharp end.

Nick.

Click to expand...

With you on that one.
I've been to too many remote digs with duff batteries. there is nothing worse really. Waste of time and effort.

Another place that sells tagged NiCds is:
http://www.budgetbatteries.co.uk
Hit the 'Industrial/Tagged' link on the left-hand selector

They don't do NiCd F cells, but their Ds and sub-Cs do seem cheaper than batteriesplus, albeit their D cell is heavier with a slightly lower capacity.

I've been running my 24v sds drill (cheap Black and decker off eBay) on lead acid cells for over a year now. I'm using 2 12v 7Ah Yuasa batteries in a cheap copy of a pelicase (wrapped up with some old carry mat). I've abused this through several caves (droppped it three meters on one occasion) and the worst that has happened is that the cables come off the connectors.

Charging wise I use a charger from Maplins that is rated from 6-15Ah (I think) and charge a battery at a time. I'd be careful about adding extra cells to a lead acid pack since the internal resistance of the lead acids is a lot less than the NiCad and NimH cells.

biffa said:

I've been running my 24v sds drill (cheap Black and decker off eBay) on lead acid cells for over a year now. I'm using 2 12v 7Ah Yuasa batteries in a cheap copy of a pelicase (wrapped up with some old carry mat). I've abused this through several caves (droppped it three meters on one occasion) and the worst that has happened is that the cables come off the connectors.

Click to expand...

I know several other people who have had success with a similar setup, but I also know that in the days when I tried it, the batteries only lasted 10 or so trips and then they went goosed. Since I was doing two or three trips a week at that point, it wasn't really satisfactory. Mind you, this was (I hate to admit!) over ten years ago and it may be that Yuasa and similar batteries have got more robust in that time.

Charging wise I use a charger from Maplins that is rated from 6-15Ah (I think) and charge a battery at a time. I'd be careful about adding extra cells to a lead acid pack since the internal resistance of the lead acids is a lot less than the NiCad and NimH cells.

Click to expand...

You can do 'battery at a time' charging with lead acids fairly successfully, but I would not do it with NiCds - they need to be evenly matched because once a cell starts to get out of sync with the rest of the battery, it will rapidly go downhill. You obviously can't just add 'a couple of cells' to a 12V 7Ah battery since the cells aren't available individually. I suppose you could put a couple of individual 'Cyclon' cells in series with the Yuasa batteries but it's certainly not a good idea to mix different cell types and capacities in a single battery. It's not really a matter of the internal impedance (and you are wrong, incidentally, about the resistance of NiCd's - for a given capacity NiCd's are much lower resistance than any other technology, which is one reason why they have the potential to explode if you short circuit them) but unless you maintain the same cell voltage across all cells in the battery you will end up reverse charging the lowest voltage cell as the battery goes flat and this will very rapidly knacker it.

So, for lead acid batteries, the 'extra couple of cells' isn't really a runner in most cases, but if you are making a pack out of NiCd's or NiMH cells then it's easy to do and I can confirm it makes a very real difference to the performance of the battery/drill combination. I also ought to say that it's not my idea - it's another success story for the Research Department at the Faculty of Bang and Sparks, University of Thornton in Lonsdale. (Those in the know will know who I mean and others will have to guess!)

Nick.

nickwilliams said:

I know several other people who have had success with a similar setup, but I also know that in the days when I tried it, the batteries only lasted 10 or so trips and then they went goosed. Since I was doing two or three trips a week at that point, it wasn't really satisfactory. Mind you, this was (I hate to admit!) over ten years ago and it may be that Yuasa and similar batteries have got more robust in that time.

Click to expand...

Further to which, I have just exchanged three 12V 7Ah lead acid batteries out of UPS's here in my office, and if anyone here has a use for the old ones (two Yuasa, one Exide) and can collect them from Great Hucklow, please drop me a line.

Nick.

On the topic of batteries, would anyone know if there is *any* harm in completely flattening NiCd/HiMH cells (to near-zero volts) on an individual basis, if they are charged reasonably quickly?

I've read various debates and comments elsewhere about completely flattening battery *packs*, but there's always the problem there of pushing a reverse current through a cell that discharges before the rest.
I was just wondering if flattening an individual cell did any damage to the chemistry or physical makeup - does it let nasty crystals form, or substances migrate away from where they are supposed to be?

potholer said:

On the topic of batteries, would anyone know if there is *any* harm in completely flattening NiCd/HiMH cells (to near-zero volts) on an individual basis, if they are charged reasonably quickly?

Click to expand...

Think you'll kill the cell. It's supposed to make the crystals increase in size, hence lower surface area, lower capacity, higher series resistance etc etc. Mind you cells aren't too expensive so you could just try doing it. I doubt you'll gain much performance wise since NiCad/NiMH voltages fall off so quickly.