Why are batteries so expensive?
- Thread starter sopht
- Start date
It's the lot sopht.
Since none of them have been entirely satisfactory there's been a continuous program of research and development into each successive type by all manufacturers, generating high costs that have to be recovered.
The scale of manufacture of high discharge rate high capacity cells is relatively small, meaning higher costs.
The more recent technologies like NiMh and Lithium have considerable potential for dangerous failures and fires, so high levels of quality control and testing are necessary.
Lithium batteries aren't just collections of cells but incorporate complex controlling electronics known as the BMS (battery management system), which regulate the charge in order to carefully balance the cells and ensure they have good life. This webpage on my site shows the content of a typical Li-ion battery.
Much of the world's current lithium production is from a rich deposit in Bolivia, but mining it causes considerable environmental damage. Accordingly, Bolivia is understandably rationing output which is forcing up the price.
The current world economic crisis has meant the nations like Britain in the biggest mess have their currencies failing to hold value. Therefore the exchange rates with much of the rest of the world are very poor and the cost of imported goods has leapt to very high levels. That alone has increased a £300 battery to around £400.
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Since none of them have been entirely satisfactory there's been a continuous program of research and development into each successive type by all manufacturers, generating high costs that have to be recovered.
The scale of manufacture of high discharge rate high capacity cells is relatively small, meaning higher costs.
The more recent technologies like NiMh and Lithium have considerable potential for dangerous failures and fires, so high levels of quality control and testing are necessary.
Lithium batteries aren't just collections of cells but incorporate complex controlling electronics known as the BMS (battery management system), which regulate the charge in order to carefully balance the cells and ensure they have good life. This webpage on my site shows the content of a typical Li-ion battery.
Much of the world's current lithium production is from a rich deposit in Bolivia, but mining it causes considerable environmental damage. Accordingly, Bolivia is understandably rationing output which is forcing up the price.
The current world economic crisis has meant the nations like Britain in the biggest mess have their currencies failing to hold value. Therefore the exchange rates with much of the rest of the world are very poor and the cost of imported goods has leapt to very high levels. That alone has increased a £300 battery to around £400.
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Thanks Flecc - as a daily user of power tools, I'm surprised at the relative costs of these batteries compared to, say, the complexities of a PC.
I'd like to make an electric bike that enabled me to use the same batteries as for my drill etc - have an array on the top of a rear rack that I could plug say 1 - 5 ish 3Ah batts according to journey on the way to work and back (I think it'll have to be a trailer for the chop saw!). The advantages would be - non-duplication of costs and weight, battery failures staggered over time.
It seems reasonably easy in my head - motor, controller, switch, batteries, but do you really need to know all the ins and outs of quality and compatibilty of components, not to mention a degree in electronics engineering? Plus, how to make that array? Plasticine?! Where should I go for advice?
The batteries I use every day (as a carpenter) never fail or give the trouble that bike batteries often seem to by repute.
I'd like to make an electric bike that enabled me to use the same batteries as for my drill etc - have an array on the top of a rear rack that I could plug say 1 - 5 ish 3Ah batts according to journey on the way to work and back (I think it'll have to be a trailer for the chop saw!). The advantages would be - non-duplication of costs and weight, battery failures staggered over time.
It seems reasonably easy in my head - motor, controller, switch, batteries, but do you really need to know all the ins and outs of quality and compatibilty of components, not to mention a degree in electronics engineering? Plus, how to make that array? Plasticine?! Where should I go for advice?
The batteries I use every day (as a carpenter) never fail or give the trouble that bike batteries often seem to by repute.
Those A123 lithium-iron-phosphate batteries do seem to have a good reputation, but it's always been true in batteries that small works best. The problems come when cells and batteries are made large capacity and larger voltage.
For example, several e-cars are delayed due to lithium battery problems, but the Tesla electric sports car has been running successfully on them for about three years. It's secret is that is uses thousands of small cells in series/parallel banks, charged via an immensely complicated system. The outcome is that the car costs around £70,000, a bit much for most of us.
The one-off US Killacycle superfast electric motorcycle uses banks of those tool batteries in an equally complicated setup.
The technical problem is that multiple cells in lithium batteries have to be managed by a complex internal electronic system that balances the cell state at all times during charging, and it's also important that the cells are pre-matched anyway. To create a 36 volt bike battery out of A123 pack cells would mean 10 of them in series per bank to reach the required voltage 36 volts, or 7 packs for 24 volts, with 3 or 4 banks in parallel to reach the required Ampere-hour capacity of around 10 Ah or more.
You'd need battery management circuitry to maintain balance between all the packs during charging, plus Schottky diodes isolating all the parallel couplings to prevent cross charging between cells which could destroy the whole pack. I'm not sure of their voltage, but it might be difficult to have a number to exactly match your bike voltage.
To all this add the potential for intense high temperature fire if anything goes wrong, and you'll see it's not something to be lightly undertaken.
The same kind of LiFePO4 batteries are on the way for e-bikes in the future, and it's already possible to buy one with a charger from one dedicated supplier, Li Ping. Some forum members are using these and one battery has now reached a year old and still going well. They have the potential for at least 1000 charges and possibly much more but are no cheaper than current bike batteries. They are slightly larger and heavier than existing Li-ion types so won't fit into existing cases and casings and mountings have to be devised.
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For example, several e-cars are delayed due to lithium battery problems, but the Tesla electric sports car has been running successfully on them for about three years. It's secret is that is uses thousands of small cells in series/parallel banks, charged via an immensely complicated system. The outcome is that the car costs around £70,000, a bit much for most of us.
The one-off US Killacycle superfast electric motorcycle uses banks of those tool batteries in an equally complicated setup.
The technical problem is that multiple cells in lithium batteries have to be managed by a complex internal electronic system that balances the cell state at all times during charging, and it's also important that the cells are pre-matched anyway. To create a 36 volt bike battery out of A123 pack cells would mean 10 of them in series per bank to reach the required voltage 36 volts, or 7 packs for 24 volts, with 3 or 4 banks in parallel to reach the required Ampere-hour capacity of around 10 Ah or more.
You'd need battery management circuitry to maintain balance between all the packs during charging, plus Schottky diodes isolating all the parallel couplings to prevent cross charging between cells which could destroy the whole pack. I'm not sure of their voltage, but it might be difficult to have a number to exactly match your bike voltage.
To all this add the potential for intense high temperature fire if anything goes wrong, and you'll see it's not something to be lightly undertaken.
The same kind of LiFePO4 batteries are on the way for e-bikes in the future, and it's already possible to buy one with a charger from one dedicated supplier, Li Ping. Some forum members are using these and one battery has now reached a year old and still going well. They have the potential for at least 1000 charges and possibly much more but are no cheaper than current bike batteries. They are slightly larger and heavier than existing Li-ion types so won't fit into existing cases and casings and mountings have to be devised.
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If you use the page below to enter the forums each time Sopht, you'll be able to choose which forum you want. For questions about any electric bike matters it's always best to use the Electric Bicycles one at the top:
http://www.pedelecs.co.uk/forum/
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http://www.pedelecs.co.uk/forum/
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To get back to my main question - how to make an electric bike that I can plug tool batteries straight into.
To take your points above, Flecc, - tell me if I've mis-read... but I don't want to take the batteries apart - I want to plug them into a rack, array, whatever you call it, on my bike to work as a carpenter, take them out and plug them into my tools.
I've seen a clip on youtube (where else!) entitled "Ultimate hybrid electric bicycle" where a guy in Seattle seems to have done just this. He says he wired pairs of 36v DeWalt batts in series for 72V and can have 2, 4 or 6 pairs in parallel according to journey length. Exactly what I want, if not perhaps to that power level. (whatever's legal)
The problems are, as non-engineer, is this for real? Plus how to achieve it, practically? Plus, referring to my initial question about battery cost, I don't see why this necessarily has to involve particularly expensive brand batteries, as opposed to my experience with, say, Toshiba batts?
If I may jump in here, Flecc - perhaps I can be of a little more help....
DeWalt do a 36 volt 2.2 amp hour Li-Ion-Phosphate battery for their tools. This seems to be the battery of choice for special projects to do with electric vehicles, and is listed as being part of the range available in the UK. I would not like to guess at the price of these though...
To get back to the idea of an array of these for an e-bike, fairly obviously 5 or 6 of them in parallel would make a good basic battery for an e-bike with 11 or 13 amp hours. To do this it would be necessary to use Schottky diodes (one per battery). The reason for needing the diodes is that due to slight manufacturing differences between the individual batteries they would have slightly different terminal voltages, and because of their low internal resistances this would mean that the battery with the highest terminal voltage would discharge through its neighbours unless diodes were used to prevent this.
The reason for using Schottky diodes is that they have a very low forward voltage drop - around 0.3 of a volt or less - compared with a normal diode which will drop 0.7 of a volt or maybe more. This forward voltage drop is important as it gets subtracted from what's available to drive the bike.....
You can certainly have a plug-in backboard to achieve this, but you might have a problem getting hold of the appropriate sockets for your batteries. DeWalt tools will have exactly one each, and the chargers will have exactly one each, but getting hold of 'spare' battery sockets for your bike is likely to be difficult.
You definitely would not be able to recharge your batteries on the bike. They would have to be unplugged and plugged into the DeWalt charger for this, in order that they could be recharged in the correct way. The construction of an appropriate charger for recharging the bank of five or six batteries in situ would be a job for a serious development engineer. So, you'd need to recharge the batteries one by one unless you had several DeWalt chargers available.
As far as connecting banks in series is concerned, once again the complexity does jump by an order of magnitude. For one thing motors and controllers which will handle 72 volts reliably will be hard to find. I know there are some about, but it's probably beyond the average gifted amateur to source and set up such a system.
The second problem with series banks of batteries has to do once again with manufacturing tolerances. You would need to make sure that every bank was fully charged at the same time before use (so that you would start from a known point for all of them) and even then you would need to have a conservative cut-off point well before any battery became discharged. This last is because in a series array the same current passes through all series components, and if one element goes flat while another is still supplying power, you get a reverse-charge situation, which will soon destroy batteries of pretty well any technology.
So, to sum up, a 36 volt system would probably be doable if you could get some suitable battery sockets and maybe had more than one charger to hand (though I understand that the DeWalt recharge time is quite short - around an hour). A 72 volt system is probably best left alone unless you have very deep pockets and a good fire suppression system wherever you're doing this (and probably following in a van while you're out riding)!
Rog.
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Thanks Rog, I concur with everything Rog has posted Sopht.
Four or five of those packs in parallel via Schottky diodes would make a decent 36 volt bike battery, getting the mechanical parts and creating a reasonable looking and functional platform more a problem than the electrical side.
P.S. My reason for saying the Electric Bikes forum is best for all questions in order to get answers is that it's the only one that everyone visits, many never coming into these sub forums so not seeing questions here.
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Four or five of those packs in parallel via Schottky diodes would make a decent 36 volt bike battery, getting the mechanical parts and creating a reasonable looking and functional platform more a problem than the electrical side.
P.S. My reason for saying the Electric Bikes forum is best for all questions in order to get answers is that it's the only one that everyone visits, many never coming into these sub forums so not seeing questions here.
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Thanks a million for making things clearer for me
I'm both encouraged, and discouraged.
A 36 volt system would be ideal, but 36V batteries for tools are heavier than I want to wield all day - which means 2 x 18v in series which could be a problem.
It's so far outside my field I need to digest it all
As someone said, I'll be back
thanks again, Soph
...a lot, but I was thinking of other makes, Panasonic or Hitachi (did I say Toshiba before, weird).. or Dewalt, whichever tools I go for, but at 18V for their lighter weight. I thought it'd be good to factor in the cost of new tools against the cost of a complete ebike...
Ooooh... I see, sorry to Flecc, I get it now, although of course it raises other questions (cost, where to get, what do they even look like etc)
That 's one of the puzzles - thus my comment about the plasticine! I assume some kind of DIY affair from scratch or getting old compatible chargers on ebay and amending.
I wasn't thinking of recharging on the bike - I recharge spare batteries at work as I go, so as long as I didn't discharge them too far on the journey there and could still use the first one for a bit, I'd be OK. I might have to pedal a lot more on teh way, and coast back! I suppose I'm thinking in the order of 4 x 18V batteries, ideally 3Ah Li-ion and two chargers (ie buy separate tools rather than a kit)
Hmm, this sounds like a real problem, and brings me up again to wondering if this is a project only suitable for specialists, unlike me? I think that guy in Seattle actually is an electrical engineer, but whether he'd be up for saying how he overcame this, I don't know. (I could try)
I'm both encouraged, and discouraged.
A 36 volt system would be ideal, but 36V batteries for tools are heavier than I want to wield all day - which means 2 x 18v in series which could be a problem.
It's so far outside my field I need to digest it all
As someone said, I'll be back
thanks again, Soph
Some good news....
A further observation on the possible problems with series connected batteries, which might encourage you....
Most people who come unstuck doing this are those who buy a basketful of 1.2 volt NiCads or NiMH batteries and connect 30 of them in series to get 36 volts. These tend to give out the full 1.2 volts per cell right until they are almost completely flat, which means in a typical situation, when one cell in a large stack goes flat before its neighbours you only drop from 36 to 34.8 volts, and that can happen even when a cell is NOT flat just due to the load of the motor. It's very difficult to tell therefore that you are reverse charging a cell.
If you use 2 x 18 volt batteries in series, the problem is much easier to deal with, because if either of these goes flat there will be a significant drop in the overall voltage long before you get to the reverse-charge situation. A normal 36 volt e-bike controller which cuts off as the battery voltage drops will probably be OK therefore.
Although each of these 18 volt batteries comprises numerous cells, the batteries always have internal protection which ensures that the cells never get reverse-charged as the whole battery goes flat. You know that the average workman will kill his cordless tool battery completely several times a day (whenever he's not drinking tea) and they have to withstand this. In general, the more cells (or batteries) you have in series, the more difficult it becomes to avoid the reverse-charge problem.
The Schottky diodes are relatively cheap electronic components. You might have to shop around a bit for suitable ones which will handle the sort of current which may flow, but that information will be readily available on here if you get to that point.
That sort of gets rid of the technical points - now all you need to worry about is the logistics of it - how to mount everything, battery sockets - etc....
Rog.
If you're planning to use 4 x 18 volt batteries in series/parallel you would probably be OK, and that would give you a smallish (6 amp hour) e-bike battery.Thanks a million for making things clearer for me
I suppose I'm thinking in the order of 4 x 18V batteries, ideally 3Ah Li-ion and two chargers (ie buy separate tools rather than a kit)
I'm both encouraged, and discouraged.
A 36 volt system would be ideal, but 36V batteries for tools are heavier than I want to wield all day - which means 2 x 18v in series which could be a problem.
It's so far outside my field I need to digest it all
As someone said, I'll be back
thanks again, Soph
A further observation on the possible problems with series connected batteries, which might encourage you....
Most people who come unstuck doing this are those who buy a basketful of 1.2 volt NiCads or NiMH batteries and connect 30 of them in series to get 36 volts. These tend to give out the full 1.2 volts per cell right until they are almost completely flat, which means in a typical situation, when one cell in a large stack goes flat before its neighbours you only drop from 36 to 34.8 volts, and that can happen even when a cell is NOT flat just due to the load of the motor. It's very difficult to tell therefore that you are reverse charging a cell.
If you use 2 x 18 volt batteries in series, the problem is much easier to deal with, because if either of these goes flat there will be a significant drop in the overall voltage long before you get to the reverse-charge situation. A normal 36 volt e-bike controller which cuts off as the battery voltage drops will probably be OK therefore.
Although each of these 18 volt batteries comprises numerous cells, the batteries always have internal protection which ensures that the cells never get reverse-charged as the whole battery goes flat. You know that the average workman will kill his cordless tool battery completely several times a day (whenever he's not drinking tea) and they have to withstand this. In general, the more cells (or batteries) you have in series, the more difficult it becomes to avoid the reverse-charge problem.
The Schottky diodes are relatively cheap electronic components. You might have to shop around a bit for suitable ones which will handle the sort of current which may flow, but that information will be readily available on here if you get to that point.
That sort of gets rid of the technical points - now all you need to worry about is the logistics of it - how to mount everything, battery sockets - etc....
Rog.
LOL, it's true (on both counts). Can't say for the guys, but I certainly get a perverse pleasure from making a battery last to the 500th screw
Actually, I can't remember anybody's battery failing on site for ages.
Yep, all I have to do now is buy all the right bits, put them all together right, not fry the batteries, get all my tools onto the bike, and wobble off.
It's the last that's giving me some pause for thought - I would need a trailer for many journeys, and although I've come to terms with the near death experience that is cycling in London, if I ventured out often with a trailer into Brixton traffic, I don't think it would be accidental.
It may be that I should aim instead for a Cytronex for pleasure, and an electric car/van whatever for work, but in the meantime, I'm still planning. I wonder if anyone has a similar project in mind on this forum?
all the best, Soph
I do use a very big trailer in heavy traffic on the fringe of London, but I must admit Brixton with one would scare me more than a bit, being familiar with the area. That said, if it's suitable, the Bike Hod type of trailer is very compact as it sits much closer to the bike than most designs so safer in traffic. Pricey though:Yep, all I have to do now is buy all the right bits, put them all together right, not fry the batteries, get all my tools onto the bike, and wobble off.
It's the last that's giving me some pause for thought - I would need a trailer for many journeys, and although I've come to terms with the near death experience that is cycling in London, if I ventured out often with a trailer into Brixton traffic, I don't think it would be accidental.
Bike Hod
If you are using a trailer and don't need to climb any very steep hills, so weight doesn't matter too much, another source of cheap power would be a trio of lead acid batteries in the trailer to give the 36 volts. No special diodes needed, just wire them in a series row and use. You'd still need to sort out the charger(s) though.
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Absolutely, and because of the way lead acid batteries work it's not too difficult to build your own charger, which is usually not the case with the alternative technologies.
Now it so happens I have these three identical (and therefore matched) 12 volt 65 amp hour Drifits sitting here, rescued from a removed fire alarm installation, several years old, but still with almost their full capacity having been well treated and little used.....
I am joking - they might be more appropriate for the electric van you were mentioning, having a combined weight of some 66 kilos. Just a bit OTT for an electric bike trailer unless your daily commute was London to Brighton.
Rog.
Do you find that the trailer holds up traffic most or just some of the time? I'd need a trailer more like the Roland Jumbo etc. for all my gear - chop saw, skil saw, drill, nail gun, router etc, plus hand tools. Weight wise I don't know off hand what that tots up to, but it's not peanuts - I'd guess at least 35kg. Is this feasible? Plus, if off-site my transformer alone is 20kg. It's amazing what I throw into the car without thinking.
The self weight of lead acid batteries puts me off for bikes.
Of course, chippies didn't have chop saws to hoick etc in the past, but I wonder how they got around with their tools, not to mention materials? Horse and cart? Shanks pony? Hand barrows maybe? How do you balance short term efficiency against long term unsustainability?
I think (based on experience in foreign parts) that they had just hand tools - many home-made - which they easily carried in a carpenter's canvas bag. It's all the modern aids and health and safety crap which bumps up the weight. If you work with Sikh carpenters on site, ask one of them how they do things in India - you might find it interesting, and I'm sure they'll be happy to tell you.Of course, chippies didn't have chop saws to hoick etc in the past, but I wonder how they got around with their tools, not to mention materials? Horse and cart? Shanks pony? Hand barrows maybe? How do you balance short term efficiency against long term unsustainability?
Rog.
35 kilos is definitely feasible, the 55 kilos with the transformer getting a bit much, mainly from the stability and handling point of view, the trailer wanting to control the bike. In my area there's usually enough room for traffic to swing out to get past me, so not as much holding up as in your area. I always have a mirror on the bike and that helps a lot for me to avoid holding things up too much. This webpage shows my trailers and loads.
Traders often used hand barrows. The Jones brothers who invented tubular steel scaffolding and the band and plate coupling used a hand barrow out of Mitcham to do all their jobs at the outset, imagine the weights they must have pushed around South London. They eventually became SGB (Scaffolding Great Britain), and members of the Jones family were on the board up into the 1990s, so the hand barrow did the trick for them!Of course, chippies didn't have chop saws to hoick etc in the past, but I wonder how they got around with their tools, not to mention materials? Horse and cart? Shanks pony? Hand barrows maybe? How do you balance short term efficiency against long term unsustainability?
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this was certainly the case in Britain in the 1940s/1950s. I one saw in a copy of a newspaper of that vintage a wonderful cartoon of a grinning "British Lion" carrying a carpenters tool bag on his way to the pub, with the caption "After a Good Day's Work For Britain - that's when BEER is best"
In India and other foreign countries, (probably non-EU mostly) the biggest difference is they do not follow the safety regs about 110V equipment. Power tools are plugged straight into the 230V mains and if the worker is lucky there is a RCD, I've seen pics of two bare wires (no earth) pushed in to a 15A round pin socket (still the standard in India)
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