UKC

Hi, got a Dewalt drill with 18v 2ah battery. Looking at getting a Dewalt hedge trimmer (bare unit) that would come with 18v 5ah batteries. 

Doing a quick Google cross reference, looks like the 2ah can be used in the trimmer but with a ‘degree’ of loss of power and run time. 

Anyone got some experience on this, how much loss of power/run time might I expect? 

Spare 5ah batteries are available at cost so if it’s significant will get one. Just trying to cut down on the number of chargers and batteries lying around the house.

Cheers all! 

its the same charger for both right?

I have 18v dewalt power tools and a mix of 2ah and 5ah. Overall the 2ah are a bit nicer in things like drills as the drill is more manoeuvrable and less effort to use. if I'm drilling a lot of holes in hard brick I'd use the 5ah. I  don't notice much difference between the two when they are fully charged. I have a drill, multi tool and orbital sander. For the multi tool I don't see much advantage with the lighter 2ah.

Simplistically a 2AH battery contains 2/5ths of the energy of a 5AH battery (assuming like for like voltages) so you'll get something like 40% of the runtime, a bit less in reality for reasons not really worth diving into. Power loss should be negligible given they're broadly comparable sizes and should have broadly comparable internal impedance.

The issue is why does the hedge trimmer ship with 5AH batteries to begin with, it may simply be that in recent years prices have fallen so they're now the default, it may equally be it's a power hungry machine and needs the big battery to make it a practical tool with a worthwhile runtime.

There is a risk of overloading low capacity batteries, like for like chemistries and structures will have a 'C' rating, a multiplier of capacity. If for example the batteries have a C rating of 5 you can draw 5x5 = 25A from the 5AH battery, fine if your clipper draws 15A. However we can see there's a problem with the smaller battery, 5x2 = 10A which is less than the 15A your clipper draws. The best case is tripping protection, the worst case is rapid battery damage and potentially with poorly designed packs, fire.

End of they day you can but see how others have got on or try it.

jk

I bought a battery Dewalt hedge trimmer in 2019 ish... shipped with a 5Ah even then

I have both 2ah and 5ah batteries for various Dewalt tools and interchange them without any issues.

The chargers that came with the 2ah and 5ah batteries are different and I only charge the batteries in their specific chargers, though I have no idea if that is really necessary or not.

CB.

Its not

All the Dewalt 18V charges work on all 18V batteries. 

The 2Ah will "work" but as it is supplied with 5Ah it is likely to need more power than the 2Ah can provide as detailed by others, or alternatively you just simply wont get a sensible run time. 

I repair Dewalt batteries in my spare time if you need some cheaper.

Great to know. Thanks.

Sorry to hi-jack, but does anyone know if the non-official batteries are safe to use, or if they are just crap?

Great, cheers!

So just to confirm, in your opinion/experience, the one charger (the one we got with the drill, 18v 2ah batteries) will charge either 2ah or 5ah without issue (even though the different units drill/trimmer) are ‘possibly?’ supplied with different chargers (I assume but aren’t 100% on that as I only have the drill charger in my possession)

Thanks 

Yes

Had a few come across my desk, there are some that are ok -ish. Not many that are dangerous but I have seen some bad ones. The main way you're saving money is that they use vastly inferior cells inside, which absolutely are not even close to the stated Ah, and will not deliver the power you need in the medium term for medium-large tools as they degrade quickly. A genuine 2Ah would be equivalent in performance in the long term. Plus just general overall poorer construction quality etc. 

I investigate fires for a living - items with lithium-ion batteries purchased from eBay or Amazon Marketplace keep me rather busy.

Is it usually when these dodgy batteries are being charged in your experience, or are there loads of scenarios.  

I suspect I have exactly the same hedge trimmer. I have a mix of battery sizes. 

All you'll notice is that the 2Ah will run out faster than the larger ones. 

Allegedly the bigger capacity packs can supply a slightly higher power, but I certainly can't tell the difference. I greatly prefer the reduced weight of the smaller batteries though!  Same story with the Makita ones I use at the wall.

The 18V DeWalt charger happily does all sizes of 18V battery - and can even tell if you've put an older 14.4V pack in too.

I've got the dewalt hedge trimmer and its pretty good, but not a professional machine by a long way. The run time on a 5ah battery is very good, particularly if you're only trimming light material. You'll probably want to stop for a break before its done, so just top it up anytime you stop cutting for a while. 

The differences between the batteries is when you start to push the machines. As someone up thread mentioned, if you're drilling big holes or cutting thick timber the 2ah batteries will quickly stall as they can't keep up, regardless of run time. So in the trimmer, they should be fine as long as you're not cutting really thick stems.

The differences in chargers is the charge speed. They'll all handle any 18v dewalt battery, but if your drill came with 2ah batteries, then that charger will take longer to charge a 5ah one than the more powerful chargers supplied with a tool with 4ah or 5ah batteries. 

Cheers (and to Luke too). 

I'll go for an official one. Could do with a larger one for a strimmer which can't quite get around a full allotment.

Most fire occur while on charge (or sometimes shortly afterwards) - there's a reason why radio control car vendors sell fire-proof pouches for charging!  But, there have been a few cases where the appliance / battery was not on charge or in use - just in storage for days.  And, it's not just batteries from dodgy suppliers, I've seen fires caused by devices made by reputable manufacturers (although they would claim they are counterfeit or have been abused by the owner).

Sometimes defective manufacture can be an issue (some tiny fault in the internal construction that develops with charge / discharge cycles), sometimes mechanical abuse (crushing / puncturing the internal construction), sometimes electrical abuse (overcharging due to a defective Battery Management System, over-discharge can also introduce permanent damage that eventually becomes incendive).  Sometimes a combination of issues.  Often it's impossible to tell why from the physical evidence - defective cells go into thermal runaway and eject flammable materials all over the place, and the heat produced induces other cells to do the same.  So you tend to end up with extensive fire damage and lots of near-empty cell casings - with little / nothing to distinguish the original defective cell from the others that went into thermal runaway as a consequence of the fire.

Good info, thanks. Yeah we have a large and very mature garden (!) we have a mains hedge trimmer for more accessible work but I also take care of the neighbours side of our hedge so need something more manageable (it’s replacing an old and cheap battery trimmer we’ve had for years) also lots of work up ladders etc where the very heavy mains trimmer is just impracticable.

 Thanks 

You'll like the Dewalt trimmer then, as it's very light. The down sides I've noticed are you need a pretty firm grip to keep the safety switches on the handle engaged (although that seems to be the norm for all machines now), and the cutters don't go right to the end of the bar. There's about 20-25mm at the end that doesn't do anything and sometimes catches on uncut stems, but thats a minor gripe.  

If you are doing lots of stuff on ladders, maybe consider Dewalts long reach cutter. I've not used that particular one, but long reach tools can save you a lot of work and often, do so more safely. 

I use lots of batteries for work and have all kinds on site-

Reading this suggests not leaving them on charge overnight?

You might want the smaller batteries for a hedge trimmer. Why not just get another 2 ah and swap batteries if it runs out. The 5ah are bigger and heavier and some jobs where you hold the tool up and move about, drilling overhead, trimming a hedge etc you might find it better

Hi, the drill comes with 2 batteries as it is so no issues with always having a charged battery but my main criteria/question is whether I can ‘get away with’ not needing another charger and battery set if I can use the drill set with the trimmer and only get a bare unit trimmer rather than a complete unit, saving money and reducing the amount of excess electrical stuff around the house.

 Thanks 

The answer to that is absolutely, yes, you can get away with using the batteries you already have.

Hmmm... Being cautious as I use Makita tools/batteries (just because the first one I bought was on a good deal then onwards I kept the same for batteries etc)... but if they are all standard modern (Li-ion) 18v DeWalt batteries you should be good to use in any DeWalt tools.

As long as your drill isn't really old and has NiCad18v batteries (they look quite different from each other, Google a picture) I think you can use the 2ah batteries in the trimmer, which'd be better than a 5ah battery in the trimmer due to weight/balance

Just double check the drill is the standard/modern battery. The bare unit sounds like what you need 

Disclaimer again: I use Makita!!!!

https://www.hpacmag.com/plumbing/dewalt-to-discontinue-18v-nicad-battery/10...

Thanks jk for the detailed response, apologies for not responding sooner. 

Cheers!