Drill batteries

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XMod
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Drill batteries

Post by XMod »

So I have a really old Bosch drill and not enough cash to get a new drill. The old alarm batteries I was using are a bit battered so I was thinking of replacing them with two gel motorcycle batteries or alternatively lead carbon batteries. I will look into Li-Ion but I'm thinking it will be expensive to get a belt made up of cells (I want the batteries off the drill).
The drill is 24Volt 270Watt so draws 11.25amps - the question is - What amp/hour rating should I aim for? Is a 6.5 amp/hour enough? I won't want to drill more than 15 or so holes in a day (too much pain hanging in a harness - one route a day is plenty!).

6.5 amp/hour battery weighs 2kg each (x2) - sounds good
8.5 amp/hour weighs 3kg each - getting a bit heavy
12 amp/hour weighs 5kg each - too much - Ive carried this size batteries before! Ouch! And too hard to handle on abseil. They do drill forever though.


BAbycoat
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Re: Drill batteries

Post by BAbycoat »

@XMod,

A few years ago I put a lot of 12mmx100mm glue-ins into bullet-hard limestone with a Bosch GBH 36V-LI compact professional. The combination of rock, drill and bits "cost" me approx 0.2Ah per hole: the 1.3Ah battery drilled 6 holes and the 2.6Ah battery drilled 12 or so.

Looking at it another way - the 430W drill ran at ~12 amps. Each hole took me about a minute, so 6 holes = 0.1 hours, at 12A = 1.2 Ah

Based on that - the 6.5Ah battery will give you >30 holes per charge!

However ... it's the combination of rock, drill, bits and volume that all matters. I don't know what rock, bit or volume you'll be drilling. But your 24V (I guess you're using a Bulldog?) has a lower impact force than the 36V I used. I believe the lower impact force means you'll need more time, amd more Ah, per hole.

None of which answers your question directly - but hopefully it gives you points to consider.
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Re: Drill batteries

Post by XMod »

Thanks that actually helps. The stone I'm drilling is ridiculously hard quartzitic sandstone. Holes will be either 10 or 12mm by 100mm,
The original 13amp/hour batteries were still going strong at 27 holes but I will probably never want that level of performance unless we are doing anchor replacement in which case there will probably be other drills on site to share the work load.

Yes it is an old bulldog (slow as all heck but makes a hole). Two alarm batteries (14.5volt) last long enough at 7 amp/hours but they aren't the right type of battery or voltage. I'll probably opt for the 8amp/hour but will see what they cost. Lugging a couple of extra kg's up the hill is better than running out of juice halfway through a route (which REALLY sucks!). The lines I am looking at are 30m and longer (so 11-12 bolts plus anchors or more). Hmmmm wish I had the $$ for a petrol driven Honda but at R40 000 or there abouts it's a pipe dream at present.

Please feel free to add comments all - every bit of info helps - thanks.
BrianG
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Re: Drill batteries

Post by BrianG »

Howzit

Not sure if you are aware of this company in Cape Town which repacks and makes custom battery packs: https://www.ipp.org.za/ I use them for work related stuff and they do good work. They will also assist with spec/design. Might be worth giving them a call....
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Re: Drill batteries

Post by XMod »

:thumleft: Shot Brian, will check them out. My old alarm batteries I fear have died a horrible death - they aren't holding charge anymore :(
mokganjetsi
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Re: Drill batteries

Post by mokganjetsi »

Off-topic but something I'd love to get some views on; will quality 18v impact drill get the job done?
Something like a Bosch GSB or Makita. Will add a couple of 3Ah or 4Ah batteries. Mostly used for western cape sandstone and some DIY (just feel I'll get a lot more general use our of a drill like this as opposed to a rotary hammer 36V beast exclusively for bolting).
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Re: Drill batteries

Post by XMod »

Will probably drill a hole (one or two guys use these) but I think it will take a hammering and not last very long and you will have the hassle of slow drilling times requiring even more battery life to get the job done. Rotary hammer is the way to go - I've tried using regular impact drills on high mpa concrete and they fail dismally whereas the rotary hammer chomps through the stuff without a second thought. If you are worried about cost (new is bleddy expensive!!) then look for a second hand one in reasonable nick. Second hand the batteries may be pap (easy to get new ones - or better yet build an off-drill battery pack) but the mechanical workings of the thing will probably still be fine (they're built tough).

One things is sure my old 24volt drill is kak slow compared to the new 36V models which fly into the rock. If I had the $$ I would not hesitate to grab a 36volt and would not even look at smaller.
Marshall1
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Re: Drill batteries

Post by Marshall1 »

I used to have an 18V Metabo for bolting. It was ok-ish, bolted plenty of routes with it. It worked reasonably well for 10mm holes, but was terrible with 12mm. It was cheap & very light weight. Smaller machines turn faster with a lower impact. This means that they burn drill bits.

22V Hilti is the optimal machine.
BAbycoat
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Re: Drill batteries

Post by BAbycoat »

@XMod,

IF your current batteries have enough juice, time yourself drilling a hole in your target rock. Multiply the time per hole, in minutes, by 3, and you've got your Ah requirement for 15 holes.

I know - seems too simple to be true. I brushed off some high school physics/algebra and derived a formula which matched my experience with the 36V Bosch. ( in statistician speak ... predicted = actuals )

Ah Needed = (Number of Holes) *(Minutes per Hole) * (Hours per minute) *(Amps)
= 15 *(Minutes per Hole) * 1/60 * 12A (for your Bulldog)
= 3 * (Minutes per hole)

:hapban
Last edited by BAbycoat on Wed Sep 02, 2020 6:20 pm, edited 1 time in total.
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Re: Drill batteries

Post by XMod »

Cool that helps. Unfortunately my old batteries are definitely dead. Ive been performing CPR (trying to charge them) for three days (on one of them!) and there is no pulse (not holding charge). I couldn't even test if the repairs I had done to the motor (burnt out brush and cracked retainer for magneto [a silly plastic part]) had been successful although the circuitry all seems fine according to my (admittedly limited) testing with a volt/ohm meter.

From what I remember it takes much less than 3mins per hole in that rock so 12 a/h is probably overkill and in practical terms the weight of that size lead acid batteries is too much (about 10kg's). We originally had two 13a/h batteries and they did 27holes without slowing down ( we ran out of steam before they did). I will probably go for a sealed lead acid or gel battery (cheapest option) at 8a/h which will weigh 6kg for two cells. Still quite heavy but manageable.

There are better options for people with money. Instead of Lithium Ion I would recommend people look at LiFePo (Lithium Ferrous Pottasium[?]) which handles deep cycle use or at the top end Silver Cadmium batteries which are usually used in Solar power installations and are designed for deep cycle use. Consult a specialist - they will need to build your battery pack.

The simple lead acid start at around R450 each (2 cells needed) going up to the Silver Cadmium at a grand per 12v cell. A custom off-drill set-up will probably set you back a bit more than that BUT for people who need new batteries for an existing or second hand drill I would thoroughly recommend building one (or having one built). I know Jason had a belt made with LiIon cells in it and that was awesome. Makes the drill light to handle and the power pack lasted forever without charging. Just dont drop the battery pack on the ground!!! (it might explode!!! :shock: )
BAbycoat
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Re: Drill batteries

Post by BAbycoat »

Sounds awesome :thumleft: . Let us know how it goes.

PS - wearing my lawyer hat, I take no responsibility if my "formula" isn't perfect.
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Re: Drill batteries

Post by XMod »

@ BAbycoat - no your formula is actually pretty good. The thing with any battery is that you should not drain more current than the battery is rated for or it will have a very short lifespan indeed. This is especially important when building a pack of the more modern (and expensive) type batteries - see below.

So this entire topic is proving to be very complex with a rage of factors to consider.

Cost: The old lead acid are by far the cheapest but you dont want to carry a liquid acid battery in your pack (been there), any spillage will ruin very costly climbing gear permanently. A better choice is a sealed lead-acid (lead alloy plates are wrapped in fiberous material) or better yet a gel electrolyte. The first can still spill if the case breaks whereas the gel will do minimal damage. Modern batteries are a lot more expensive but have the advantage of being lightweight as well as other advantages (and drawbacks - told you it was complicated!). Lithium Ion (LiIon) are the lightest at under a quarter of the weight of lead acid batteries, Lithium Ferrous Phosphate (LiFePo) are in between at about half the weight for the same power and Nickled Cadmium (NiCd) fall in between the two lithium types.

Lead acid are bad at holding charge and discharge themselves with a more or less linear voltage drop (so make sure you charge them regularly or keep them on a drip charger for storage). They handle deep cycle use fairly well.

Lithium Ion holds charge very well and can be kept for up to six months with little charge loss. They do not handle deep cycle well and you must not drain them below 60/70% of their full power. They also come in very small units of 3.7 volts each (3xfor 12volts) with a low current rating so you need to build a substantial pack to cover your current needs (which on a drill are quite high) and avoid damaging the batteries. Like all modern batteries the pack must be built with a control unit to ensure even charging and prevent excessive charging and discharging. They are sensitive little things and you MUST protect them from abuse (fire or explosion can result!!). They do not handle high burst demands of power well (another reason to build a large pack - to spread the load) so are not ideal for power tools. That said a rotary hammer drill does not draw peaks of large current the way a saw would as the load is more or less constant, but it still uses 'bursts' of power when compared to say a computer or cell phone. The have a better lifespan than lead acid and handle about 200-300 charging cycles. These would be a good choice for the person who wants a lightweight pack (disclaimer: - consult a specialist. I am not an expert. This post is meant as an introduction to help people decide which route to go only).

LifePo is the most reliable of all the batteries. It is relatively safe from abuse (being bashed around). They have the longest lifespan by far and handle thousands of charging cycles 3000-4000. They also do not like producing bursts of high power so you would need to build a substantial pack again to avoid exceeding the current ratings. That said they have much higher current ratings than LiIon but come in 3.2volt units (4xfor12volts). These are probably the top choice for someone who wants the least maintenance and hassle (again consult a specialist before spending the big bucks - they are expensive!)

Nickle Cadmium is probably still the best suited battery for power tools. They can produce bursts of high power easily (which is why they are still widely used). They hold charge reasonable well. They do not however like being drained to much and one should not go below 60% of full power. They are also tempramental types and require regular attention and maintenance. They must be drained down to 10% of power every three months to break up dendrite formation which severely limits power production and can lead to shorting and a fire if unattended. They do not like being used just a little then charged again as the build a "memory" of the discharge/charge cycle. These are the battery of choice for people who do not mind doing the maintenance required to keep the things running properly (again consult which type is best suited to your own drill).

Two other possibilities are Lead Carbon (cheaper than Lithium and suited to deep cycle) and the Silver Cadmium (uber expensive - used in solar installations and well suited to deep cycle use) however I have not come across these guys in small units that would be suited to a drill battery pack.
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Re: Drill batteries

Post by XMod »

After all this I will probably just be a cheap bastard this time round and simply buy two more alarm batteries (very broke after lockdown) which are by far the cheapest at R190 each. They are a poor choice for deep cycle use and will likely have a very short life but I'm just gonna buy them as a stop gap until I can afford a more permanent solution (like maybe a new drill - :mrgreen:). Whatevs, they work and will get me back into equipping routes which is the important part :) :)
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