supercapacitors + battery

[jimmyhackers]

argh....looks like the chinese cheap parts strrike again. in its favour it does do the job as standard. even with all my new caps im still at half of the minimum needed farads u said id need :S i could add more but as you said diminishing results.... i tried two packs on one battery and the extra battery sag reduction wasnt anywhere near as noticable.

it does make me wonder about where they've cut corners in the rest of the build. i plan on going up to 60v and possibly 96v eventually..... i have a pretty good feeling the controller wont hack it : ) and i will eventually need a new one. but in the meantime for about a tenner worth of electrical parts (mosfest transistor things) and a much better heatsink added. i wonder if i could squeeze some more torque and another 50% runtime out of it heck, id be happy with another 5% runtime and torque if i could get it.

i read the hotrodding article and it links etc and.... 5%, i think did seem the amount of efficiency you could get from changing mosfet/transistors to better versions.

thanks again for the help....i might take another trip to maplins

 

[Stalkingcat]

Jimmy, have you got any pics of your build of late?

Even though it's less of a headache to just buy power ready componants, I'm still interested in squeezing the max out of a basic ebay kit.
The lesson learn can then be transferred upwards and onward...

 

[jimmyhackers]

lol......it wouldnt be that interesting.... if youve seen my new front forks ive welded on in another post (springer forks) youve pretty much seen most of it.

looks like an old cafe racer now

the booster packs ive made are just a few capacitos in parrallel with a red a black lead going to the + and - terminals of each battery. they're hidden in the battery bags aswell so you cant notice it from the outside.

im still waiting for the "booster" packs from ebay/china. in heinsight im not too sure if i want to attach them.....mainly due to size compared to what i made.
they dont fit in the bags at all and will make the bike look a mess of cables.

search daizin volt stabilizer in ebay....they are the "booster" packs i ordered. i have a very old version from the same company (raizin warped named) that doesnt have a digital led volt meter built in.

 

[jimmyhackers]

i was just talking about pwm with my friend... he runs an ecig shop and ecigs use pwm... he too confirmed a massive initial powerspike when engaging the ecig (thats why they use li-ion batteries aswell). i used to work for an led street lighting company and im pretty sure the same happened with the pwm of led's. i remember a 100w led light spiking at around 350ws for a spilt second on startup before settling to its intended 100watts.

if the same was the case for my 1000w watt motor it could be spiking at a shocking 3500w for a split second from standstill.

in my electronics lessons at school the teacher always referenced water in explanation of electricity. thusly ive always viewed this initial spike when switching on most electrical things as the pipes (wires/electrical components) needing to fill up with water (electrical energy) before they can actually start flowing.

i dont think theres any real way to get around or reduce this "start-up" spike. the load will always be what it is....but you can choose where it gets it all from. lipos probably can handle this, 1-2c seems an acceptable discharge rate for lipos before you encuur the peukert effect.

for my sla i need a discharge rate of 1/20 c to not encuur peukerting. which just aint gonna happen

i dont think ive made a lipo replacement.....lipos win hands down on everything but price. ive probably just found a way to make my size/application sla's less pants.

i guess its been the nature of usage of lead acid batteries in their main commercial usages, where the current draws been so high (starting cars) that adding caps is a mouse fart in a tornado so it isnt done. then on the other end (alarm systems) the current draw is so low caps arnt needed.

both of which are usually constantly charged and kept topped up

my size batteries wager into the middle sized sla "leisure" end of the market, so golf trollies and mobility scooters. where (no offense to golfers, the elderly or salesmen) if one is able to afford to play golf theyll buy another battery. and the second is too old to know/care they are being ripped off and will buy another battery in a few months,maybe even a whole new scooter. the third being the salesman rubbing his hands together, loving every minute.

its gets to the point when you start calculating things out... batteries are the main limit to electric vehicles. when you work out roughly a kw equals 1.6hp

then you calculate energy output from batteries (even new tech).. and get disgruntled realising power to weight/size is about a third of an equivalant petrol powered vehicle. then you realise the range is about the quarter of the quivalent in petrol : S

there is hope though, i cant help thinking the "petrol salesman" has scewed things in his favour. a 30hp petrol engine has 30hp at peak hp. the rest of the time its has a lot less!!, as all internal Combustion engines do. A 30hp electric motor will pretty much do 30hp all the time. i guess this why IC needs a gearbox and EM seem to explode "comparable" gearboxes.

so comparing a petrol engines "peak" kw's or hp or torque to an electric engines "constant" kw or hp or torque always falls short in favour of petrol.

range....still sucks, but i get 30miles out of one charge which costs all of 2p in electricity. doing that in a petrol car cost about...100 times more.

all i can say is.....bring on tony stark and the arc reactor. which is honestly the main reason im drawn to electric vehicles.

when that "miracle battery" comes out, all i have to do swap over two wires and im laughing.

 

[jimmyhackers]

i redid my booster packs... heres a pic of one... 4x 4700microfards caps in parrallel. just imagine one of these connected across each battery terminal.

 

[Stalkingcat]

I don't know much about capacitors but understand what you're trying to do.

If price wasn't in the equation, then the same space taken up by your LA's could be used for more quality lipo in parallel, which at 20amps continuous shouldn't run into that much peukert effect?
Maybe I'm wrong, where did you find the figure of 1-2c for lipo before draining efficiency levels?
Depending upon how you ride, peak amp draw usually doesn't last long before the volts kick in.

Have you connected this up yet, would be interested in if it works.
It's done in F1 but with super caps and from what I gather, the energy comes from regen.

EDIT, just read the first posts in this thread and most has already been covered, oops
Fill her with Lipo Jimmy!

 

[jimmyhackers]

thanks for the interest....this isnt regen like the F1. or regen at all. that stores up the energy from braking to release it at the press of a button.

my caps are storing up energy and releasing it automatically under demand.
however.....the limitation is they dont really recharge unless i come off the throttle completely.

the puekert effect is....pretty noticeable on a lead acid. have a look/play with this website
http://www.csgnetwork.com/batterylifecalc.html.

at 20amps of draw current my 20ah battery only has 14.8ish amphours of juice in it. at 10 amps they hav 15.8ish ah of juice. put in a peukert rating of 1.2(probably what they're closer to) and i get 12.6amphours and10.9amp hours.

as i dont have a shunt, or cyclecomputer ive estimated my current draw using fuses and seeing how/why they blow. essentally i can get to full speed tentitively and not blow a 10amp fuse. at full tilt the largest i can pop is a 25amp fuse. meaning my amp draws varies between 9ish-26ish amps.

so the higher my current draw from the batteries the less they have in them.
meaning if i can reduce my peak current drawn (from takeoffs) from the batteries ill have more ah left overall.

the 2c rating...ive noticed on many lipo life cells that are above the 10ah range on ebay and are rated at between 0.5c to 2c.

rc lipos (small ones)......from my experience still suffer from the peukert effect. i have 12v lipos rated at (30c) 3300mah. my imaxb6 charger tells me exactly how many ah its put into or out of them after each charge (or discharge) and its a lot closer to 1600mah. meaning nearly 1700mah is actually still in the battery and only available if i completey discharge it (destroy battery). If i increase my discharge rate the number of amp hours i get out of the battery is less than at a lower rate.

basically......battery companies use numerous misleading tactics to make you think you have more than your actually paying for. the 20hr rating with lead batteries, and the actual usable ah in lipos (if you want a long servicelife).

 

[Stalkingcat]

Here's an interesting one to calculate SLA vs other cell types

http://www.ebikes.ca/tools/simulator.html

If you use the simulator above and have the same settings (motor 9c, controller 20a etc) they choose Battery type SLA 48v 12ah.
Then choose custom battery 48v 12ah with a lowish internal resistance.
Then compare the two range readings.

Maybe the battery companies are misleading us as C rating is apparently measured by them at a fixed rate, to make them look good. However if you don't mind splashing some cash, then there is much better cell chemistry to be had.

If you just want to experiment, then go for it!

 

[Stalkingcat]

A shameful copy and paste

There is a thing called Peukerts effect, basically the SLA has a high number which means the higher the discharge the lower the capacity the battery will supply, an SLA at a 10C discharge will supply less than half its nameplate capacity where as a Lipo will supply almost all its capacity, so a 5000 mAH LI-po will give the same run-time as a 12000 mAH SLA at a 10C discharge,

 

[D8ve]

A shameful copy and paste

There is a thing called Peukerts effect, basically the SLA has a high number which means the higher the discharge the lower the capacity the battery will supply, an SLA at a 10C discharge will supply less than half its nameplate capacity where as a Lipo will supply almost all its capacity, so a 5000 mAH LI-po will give the same run-time as a 12000 mAH SLA at a 10C discharge,

But a SLA run down to 1% charge may not recharge at all and will have a reduced life span. Lithium is much more tolerant of deep discharge

 

[jimmyhackers]

ive had a play with that calculator....its seems to rather underestimate my top speed compared to my real world figures.

whereas,

http://www.electricbikesimulator.com/

this one seems to be a lot closer speed/wise to what im getting in the real world. including my recent trip upto 60v (cheack other post for my results).
plus you get a cool moving picture with it.

on the note of lithiums reliability....and deep discharge....my friend used (past tence now) his lipos very disrespectfully, deep discharge, fast recharge, ect ect

and i used past tence because his batteries (same make/model as mine) all either set on fire or puffed up and stopped working. i still think lipos are overrated, like sla you get the "described" lifespan if you use them respectfully. fast charge or deep discharge seems an early death sentence for any battery.

its like a car salesman saying this car does 200mph and gets 40mpg "just not at the same time" (he wont tell you the bit in speach marks)

 

[Stalkingcat]

ive had a play with that calculator....its seems to rather underestimate my top speed compared to my real world figures.

These calculators are based on laws of physics. Because the exact windings of your motor aren't known and along with other variables, they will always only be a ball park figure.

Like you say, I have loads of puffed lipos, however they are the ones that i have either ridden down too low, or where ive forgot to turn the controller off and they have been slowly drained over days.
The ones that have escaped my lack of care, last for years.
I always charge at 8amps through the balance leads.

fast charging does have a big effect on life span but hey, they are pretty cheap to replace and unlike welded together packs, a dodgy cell can easily be found and removed.

 

[Stalkingcat]

But a SLA run down to 1% charge may not recharge at all and will have a reduced life span. Lithium is much more tolerant of deep discharge

The rule is, never above 4.2v never below 2.7v
however once they get to around 3.2v the drop is rapid and pretty hard for them to survive if drained right down.

 

[jimmyhackers]

i dont go below 3.8v on my lipos. my friend who blows them up does go below closer to the 3vs :S.

maybe if i went lower id get more ah....but it seems risky

ive have a set of 6 lipos for my tyco rc rebound mod. bought them about 4 years ago. hardly use them (mainly summer time) so i make sure they go on storage charge and check em every other month.

ive only lost one and that was because a clone/fake version of the imax b6 charger skitzed out on me and puffed one up like a baloon.

so hands down, properly treated a lipo battery lasts a long. long time.
but then again so can a lead acid.

i had a semi revalation today, about why possibly lithium tech has a better lifespan compared to lead acid etc......because they have balance leads and lead acid doesnt.

ive gone through a fair few lead 12v "dead batteries" in my time and there is always that really annoying part in the diagnosis.

when you check each cell (out of the 6) to find one of them is caput (possibly 2) and the rest are all fine.

makes me wonder if they made a lead acid with a balance lead they too would last longer?

 

[trex]

...
i had a semi revalation today, about why possibly lithium tech has a better lifespan compared to lead acid etc......because they have balance leads and lead acid doesnt.

ive gone through a fair few lead 12v "dead batteries" in my time and there is always that really annoying part in the diagnosis.

when you check each cell (out of the 6) to find one of them is caput (possibly 2) and the rest are all fine.

makes me wonder if they made a lead acid with a balance lead they too would last longer?

yes, but the result is only justified wheen the battery is used for long life low current applications. A balancer does not fix a bad cell, it simply removes the positive feedback effect of a poor cell(s) in a string. You do get more charging cycles with a balancer if the battery is not abused.

 

[jimmyhackers]

i get the whole new lithium tech has more cycle life...but hear me out

a balancer wont fix a bad cell, but it will stop a healthy but unbalanced cell from messing up and going bad and putting more stress on other cells lowering their lifespan.

seeing as lead acid batteries "never" came or come with balance leads and therefore never get balance charged. they are "always" in a state of abuse

when they make lead acid batteries they aways come with more than one cell
3 for 6v 6 for 12v and so on...

so id imagine when they test the lifespan of a lead acid battery. they test a full battery and not a single cell, discharging it then "not" balance charging it but "abusive" "regular" "old fashioned" charging it back up.

if i didnt balance charge my lipos at least after about 3 cycles id be damaging them.
after every use they're always out anyways so i have to balance charge.
Then we go and do that same abuse to lead acid every day all day and it doesnt bat an eyelid

which battery tech really is tougher/longer lasting...when you think about like this?

i might be wrong here and making an ass of myself and they do test a single lead acid cells lifespan individually?anyone know?
might be a marketing strategy mr leadacid missed and are kicking themselves about

on the other side the lipo lifepo4 etc batteries all come balance leaded up and when tested for lifespan are tested in optimal conditions with a non abusive balance charge.

all of which makes for a percieved higher cycle life of the battery.

i guess the lead acid companies would have a large amount of infrastucture to change and customer resistance if they added balance leads to new leadacid batteries and the requirement of customers to buy a new special balance charger.

and all new cars now need a new fangled silly alternator or a balance charger. then all old cars now need to be modified to accept.... and hassle hassle hassle... (not gonna happen)

whereas lipo lithium etc is "new" so the creation of a new infrastructure is accepted by the customer as a nessesity of the new tech.

bit of a rant again. sorry

as i said before about diagnosis of dead leadacid batteries...it appears one cell gets low (unbalenced) over time.

 

[Perrone]

Does anyone know the difference between running 1 large capacitor that is 16v 500 farads or 6 - 2.7v 500 farad capacitors in series to reach the 16v? It seems the individual capacitors would need to be soldered together along with circuit boards to balance the charging and current flow, yet 1 capacitor that is large enough would be much simpler and cheaper to purchase and install?

 

[oyster]

as i said before about diagnosis of dead leadacid batteries...it appears one cell gets low (unbalenced) over time.

You could be right about one cell. Last failed lead acid I returned to the shop as it was within warranty. On counter, put their tester onto it, looks fine. Then he did it again as I looked so surprised - almost completely dead. At most, it had been slid a few inches across the counter. I strongly suspect a single dead cell.

Yes - I did get a free replacement.

 

[Danidl]

Does anyone know the difference between running 1 large capacitor that is 16v 500 farads or 6 - 2.7v 500 farad capacitors in series to reach the 16v? It seems the individual capacitors would need to be soldered together along with circuit boards to balance the charging and current flow, yet 1 capacitor that is large enough would be much simpler and cheaper to purchase and install?

Unfortunately capacitors in series obey a different law. 1/ctot= 1/c1 + 1/c2 + 1/c3 etc.... So your 6 of 500 farads would be 1/ctot = 6/500 or ctot 500/6 or 90 farads... Not what you wanted!. But the total voltage difference allowed accross the stack is the sum of the voltages in this case 6 x 2.7 or 16.2v

 

[Danidl]

i get the whole new lithium tech has more cycle life...but hear me out

a balancer wont fix a bad cell, but it will stop a healthy but unbalanced cell from messing up and going bad and putting more stress on other cells lowering their lifespan.

seeing as lead acid batteries "never" came or come with balance leads and therefore never get balance charged. they are "always" in a state of abuse

when they make lead acid batteries they aways come with more than one cell
3 for 6v 6 for 12v and so on...

so id imagine when they test the lifespan of a lead acid battery. they test a full battery and not a single cell, discharging it then "not" balance charging it but "abusive" "regular" "old fashioned" charging it back up.

if i didnt balance charge my lipos at least after about 3 cycles id be damaging them.
after every use they're always out anyways so i have to balance charge.
Then we go and do that same abuse to lead acid every day all day and it doesnt bat an eyelid

which battery tech really is tougher/longer lasting...when you think about like this?

i might be wrong here and making an ass of myself and they do test a single lead acid cells lifespan individually?anyone know?
might be a marketing strategy mr leadacid missed and are kicking themselves about

on the other side the lipo lifepo4 etc batteries all come balance leaded up and when tested for lifespan are tested in optimal conditions with a non abusive balance charge.

all of which makes for a percieved higher cycle life of the battery.

i guess the lead acid companies would have a large amount of infrastucture to change and customer resistance if they added balance leads to new leadacid batteries and the requirement of customers to buy a new special balance charger.

and all new cars now need a new fangled silly alternator or a balance charger. then all old cars now need to be modified to accept.... and hassle hassle hassle... (not gonna happen)

whereas lipo lithium etc is "new" so the creation of a new infrastructure is accepted by the customer as a nessesity of the new tech.

bit of a rant again. sorry

as i said before about diagnosis of dead leadacid batteries...it appears one cell gets low (unbalenced) over time.

Its not a rant, but there are very large different chemistries at play. The classic lead acid battery has been going on for 120 + years and is optimised for particular uses. There is a world of difference between the battery you have in a car, where the need is to have an enormous surface area of lead, in order to have a large cranking current capacity and the batteries which were used in telephone exchanges where the requirement was for long life high reliability but low current demand. The physical structure of the lead panels is completely different.. the car uses packed granules of lead in plastic frames, the submarine traction batteries use solid plates of lead etc... These lead granules disintegrate with time and make a sludge in the bottom of the cell
In comparison with lithium, low voltage or over voltage accross a cell does not lead to a fire hazard or an explosion. The lead battery is pretty immune to rough handling. It is only destroyed by leaving it in a discharged state for a long while a chemical reaction takes place which coates the surface of the lead with an insulating layer. A sheet metal battery could be resuscitated by scraping the plate, but you cannot scratch the individual granuales.
. Over voltage just causes electrolysis of the water in the acid making hydrogen and oxygen gas . So they dont need a battery management system. They do need the electrolyte to br tested periodically
It used to be part of the ships radio officer training to take these measurements and top up batteries as needed.