How did it come to have no electrolyte in it? Was it just poured out? If so, then you would need to refill with sulphuric acid, not distilled water.
TBH, it really isn't worth it. A new battery with a 3 year guarantee will cost you ~£40.
Pretty much all modern battery chargers do the same job. You won't notice a difference. Just make sure it has built in current limiting.
You haven't done any harm, but it may not work.
I don't really use Halfords - the only good thing they sell is their own brand sockets (which are v. good value imho). Go to a motor factor - it's where the trade get their stuff, and they all happily deal with the public. You'll get a much better deal.
If it just dried out before, and you only needed half a pint, then it may well be ok. But you ought to charge it for 2-3 days before using it. Even then, I still wouldn't use it in a road car - a new battery is the price of a full tank of petrol, so not worth risking a no-start on a cold morning.
Er, it was left for ages, and I (before you wrote - woops) put some distilled water in: it took about half a pint between all the cells - have I goofed.
Halfords ? Its a big heavy Varta - can I really get it for such a good price ?
The battery is slow charging now - only time will tell (tomorrow) if its gonna be ok. I wonder.
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