Controller and Battery compatibility question.

I currently have a Schwinn Ecotour Ebike and I am wanting to get a battery pack for it, mine is SHOT! I can order this:

24V 8Ah NiCad, 5C Max Rate from http://ebike.ca/store/store_batteries.php for $195 shipped, my Schwinn has a 24v 35A controller, will this NiCad battery pack work with my controller? Please advise.

Edit: My Schwinn has a 450watt motor on it

Hello and welcome!

The 24v 8hr battery 5C would be capable of providing 5 * 8 = 40A according to the specs so it should work with your existing 24v 35A controller but if the 5C is a "generous" rating... well the more current you pull, the less the battery actually provides in AH.

Are you looking for compatible stock equivilent replacement or added range, top end speed, etc?

I was curious about your bike so I did some research and for the most part you have an eZip/iZip (they didn't do much differently)... that means this is applicable to you:

http://www.ebikeforum.com/electric-bike-scooter/137788-my-ezip-izip-upgrade-round-up.html

The user upgraded to 36v (there is some log though out of date)... since I assume you have had this bike a while and that it's SLA powered 24v... you should have a viable controller (the newer ones must be replaced, older seem to be fine with upgraded voltages) already onboard... it opens alot of options (and some top end speed, 24mph supposedly).

I would split the difference and go with 8S but you could go as high as 10S (42v hot) with some double checking and testing... HobbyKing offers 8S lipo packs (5AH but 20C rated) and chargers for a comparable price to what you would pay for the NiCD... but the capacity rating is at a much higher discharge rate of 100A (for the lipo)...

So... yes the NiCD will work but, you have a multitude of options available for alternative light weight replacements to your 24v stock setup...

Example of 8S... I would probably spend the extra $$ and get 2 of those 8S packs to run in parallel as a single 8S 10AH power source - that's a 20C rated source so capable of 200A continuous, your 35A maximum would be silly in comparison You will get a FULL 10AH out of a Lipo pack and the weight savings...
Each 8S pack will weight about 2.4 lbs for a total weight of < 5 lbs of battery - less than the weight of just 1 of your 12v slas if I am not mistaken and 4x the capacity (more like 10x the capacity based on the numbers I could find for your bike).

Hope this helps!

-Mike

Ok I found http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=10870 there. Looks awesome, I suppose I am confused on mAh values. 5800mAh is 5.8 Amps right? So wouldn't the 8ah NiCad's go alot farther in range? Also for that pack I linked above do I need to replace my controller? If so then what is a good inexpensive replacement recommendation? Any clue on what I might expect out of one of these packs if I bought 1 just to test? I am SURE that I'll buy another one soon to get 11AH out of a 2 pack setup, please advise, you have me very excited now.

Edit: OMG Its under 140 bucks shipped to get that LiPo4 pack with shipping to me! Let me know about those AH things, I don't know these things.

I did a quick look up of your battery's pack and see that the standard battery is a 24V 10AH sealed lead acid battery. You were probably getting roughly 5AH max out of it before it died. SLA batteries are notorious for giving much less than their rated power because of the Peukert effect.

The 8AH NiCad batteries will give you much closer to the 8AH that it states. Lastly and probably most importantly. You do not need to replace your controller. The controller should work fine with the Nicad batteries. Controllers are normally not battery-type sensitive

Nicads are the battery type that HAS a memory effect. If you recharge the battery before it's fully drained, it will not give you the full power of it's rated capacity and eventually will die. You need to drain it completely fairly regularly in order to maintain full capacity. Other more modern battery types do not have this memory issue. NiMH, Li-Ion, LiMn, LiFEPo4, LiPO do not have this memory effect. LiPos are the current favorite because of their small size/weight and amazingly low price these days.

Ambrose

ambroseliao said:

I did a quick look up of your battery's pack and see that the standard battery is a 24V 10AH sealed lead acid battery. You were probably getting roughly 5AH max out of it before it died. SLA batteries are notorious for giving much less than their rated power because of the Peukert effect.

The 8AH NiCad batteries will give you much closer to the 8AH that it states. Lastly and probably most importantly. You do not need to replace your controller. The controller should work fine with the Nicad batteries. Controllers are normally not battery-type sensitive

Nicads are the battery type that HAS a memory effect. If you recharge the battery before it's fully drained, it will not give you the full power of it's rated capacity and eventually will die. You need to drain it completely fairly regularly in order to maintain full capacity. Other more modern battery types do not have this memory issue. NiMH, Li-Ion, LiMn, LiFEPo4, LiPO do not have this memory effect. LiPos are the current favorite because of their small size/weight and amazingly low price these days.

Ambrose

Click to expand...

So with this pack http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=10870, from the above posted Izip link it seems I should be able to run this 25.9v pack with my factory controller (probably!) can you advise what I'd need to get this running? Just some basic knowhow to wire it up and a charger? Or do I need to buy a BMS and other stuff? thanks in advance all!

Matt,

You will need to buy the battery and a charger capable of 8S - I was thinking more along the lines of an iCharger208B+ or iCharger 1010B+ to keep it simple, safe and automatic.

My friend Ambrose beat me to it on the AH stuff... a single 5AH 8S pack would very likely get you further and surely faster than your 24v SLA pack (which as ambrose points out, never gives what it claims... usually they are rated at 1/2 or 1/4C discharge).

I am going to step up though and say hold it a minute... take a step back and lets work out the details before you pull the trigger on any orders

Scan through the upgrades the guy DarkAngel did on that other forum... on one bike he replaced his controller with a 36v currie controller... He also changed the rear freewheel to an 11t-34t in order to be able to better pedal assist.

Now...

1.) How fast do you want to go?
2.) What kind of range are you trying to acheive? What range do you have now (or when the SLAs worked right)?
3.) What is your technical skill level? Can you use a soldering iron?

If all you want is a little bump in speed the 8S will deliver since it's resting/nominal (where it will spend most of its time, even with a 35A load present) voltage is: 29.6... I would guess it will take you to 22mph sustained and provide better throttle response than you have now but...

You could also replace the motor freewheel sprocket to increase top speed a bit and then 8S would be like a 10S (which is 36/37v nominal and 41.5v hot off the charger) in terms of top end.

No matter what you do, anything beats a 10AH SLA 24v pack - I do mean anything (think hundreds of AA soldered together)

Since there wasn't much going on here tonight (or on TV) I did all the research on your bike (actually a friend from here has one too and wants to upgrade it... so the research is general purpose) and really it seems the best path to upgrade:

1.) Replace stock controller and throttle with 36v version
2.) Upgrade to minimum 10AH 37v LiPo (6lbs total weight, 3 lbs per 5AH block)
3.) Replace rear freewheel with 11-34t

If you just want to TEST a lipo power source... I would strongly suggest you purchase a good charger like the iCharger 1010B+ or 208B+ (these could charge even a 20AH pack in 2hr / 1hr respectively) and a matching power supply and a pair of 8S packs for parallel use (10AH).

The charger can be used for any other batteries you may have or may get / build... and can perform up to 10 and 20A rates of charge.. one advantage of LiPo is 2C charge ability so even with an 8S10AH pack, you could in theory with the 208B+ charge it up in less than an hour at a 20A rate

That setup will surpass (by far) what you have now and the NiCd offering, if you use conservative charge cutoff (setup in the charger) perhaps 4.16v per cell and don't over discharge the pack (I'll explain later if needed) then you could expect perhaps 1000 cycles or even more (I have one pack here, it's ugly but then it has over 1500 cycles on it)... and no memory + 6lbs riding weight (throw the charger and supply in backpack or trunk if needed).

Feel free to post questions back to this thread or PM me directly...

Just give some thought to what you really want to acheive, this is one rabbit hole you can seriously fall into

-Mike

PS:

Gary Goodrum at tppacks.com has an 8S HVC/LVC board (active cutout when too low or high) which can be used to protect your LiPo packs... You could also use a CellLog8 from hobbyking to monitor the 8S pack and set the alarm to 3.2v which can also be wired to interrupt the throttle and cut the motor out.
If you use gary's type of HVC/LVC then you can also get a 40-50.00 24v S-350-36 power supply, tune its output voltage to 33.28v (4.16v per cell X 8 cells) and you will have a BULK CHARGER (no balance though) with approx. a 10.5A charge rate (so 1hr for two of the 8S packs in parallel which is known as 8S 2P).

Right now it seems the best pricing on a charger of sufficient capability from HobbyKing would be:
http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=9005

and you will need a power supply to run it from..

-Mike

Lets rehash a little, ok what do I want to do.. I want to be able to do about 20km's without pedaling at ALL, I want to keep this thing as stupidly simple as possible, I will do mods and everything later on freewheel and stuff, right now I have no batteries at all so I just need something quickly.
I want to be able to travel around 20mph, I was thinking to buy one of the packs I linked above, use it and try it because if what ya'll say is true that the single 8s 5AH pack will be AT LEAST as good as my 24v 10ah SLA pack it came with then thats all I need, and I'll purchase another 25.9 pack later on to run 24v 10AH.

PS. Reasons I am not doing all those mods on the other posting is because this bike will be inherited by my wife once its all up and running and she'll be pulling a baby carrier on our longish bikerides, don't want speed, want a nice low 24v load and tons of AH to go long distances.

mwkeefer said:

Right now it seems the best pricing on a charger of sufficient capability from HobbyKing would be:
http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=9005

and you will need a power supply to run it from..

-Mike

Click to expand...

Dammit I don't have $150 bucks for a charger, guess I won't be ordering the battery pack for awhile.. man.. took all the wind outa my sails.

What about this charger?
http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=7523

OH PS, little more info: I am ok with the recharge taking over-night to complete, I will only be doing the 20km's once a day, then charge them when I get home for the night, let me know if my el-chepo charger would work thanks.

Matt,

Chillax brother - that's why we think it all out ahead of time

The charger you linked to would be fine for the 8S pack and for the price and assuming it will charge 8S at 150w with sufficient input supply (do you have a supply to use - 12-18v?) which would be a charge rate of 4.5A - still quite useable given your overnight schedule and limited commute.

On a single 5AH it would be about an hour, on a 2P (2 packs in parallel) it would be 2+ hours to charge but that's still useable

You would only need some manor of knowing your cell voltages when in use, that could be the HVC/LVC board offered by gary or even a CellLog8 (the one without logging even) - there are circuits posted here on ES for interrupting your throttle from either solution... that would protect the packs from overdischarge.

So you know... the 2 most common issues resulting in LiPo damage, loss of capacity or expansion:
1.) Over charging past 4.2v per cell
2.) Over discharging past 3v per cell

Long as you prevent that (the charger handles the overage, the cell log or gary's lvc handles the underage).

-Mike

-Mike

I do have a power supply I can use that outputs 12-18v (think laptop charger or the like), can you post a link to where I can buy or make or obtain a HVC/LVC board offered by gary or even a CellLog8 (the one without logging even), w/e works I know some basic wiring and stuff, let me know what I can do to make it work, I'm placing the order tomorrow for the 8s 5Ah pack and charger tomorrow, now need that HVC thing or w/e, thanks and hope to talk soon.

So once I have the battery pack and charger I'll have all I need except for the HVC thing to make my basic Schwinn ebike into a lipo4 machine right?!

I'm goin to bed I'll check responses tomorrow, thanks in advance!

update: I was reading online that a few guys had 10ah Li-ions for their izips and the 10AH was not enough juice to keep the bike going, I don't much understand, please check here for reference: http://www.ebikeforum.com/electric-bike-scooter/138663-58-20-9-6ah-25-9v-li-ion-pack.html

He says he has 25.9v and 10ah is not enough, so will the 5AH i'm getting out of this RC pack be enough to be comparable to the range of the factory SLA pack? (Factory this bike got 15-25km's range before charging with the 24v 10ah SLA pack)

Anyone have some info?

Matt,

The 10AH he was citing was Either SLA or old fashioned laptop Lithium Ion... their C rating or "Discharge Capacity" which is the technical proper term is about 2C max, so a 10AH pack would provide up to 20, maybe even 25A without issue but the controllers are pulling 35 peak (which would be uphills, accelleration, etc) which for the battery chemistry he was using.... not really capable.

My personal eBike (my favorite anyway) is a 20" Nova folding bike (http://www.downtube.com) with a rear geared motor running at 18S Lipo which is 75v hot and 66v nominal (so it's about 2x the voltage your looking at)... my current limit is set for 35A and my pack warms up (it's supposed to) to about 95 degrees but remember these batteries are rated for 20-25C continuous and 30C peak... I run this bike on a 5AH pack most of the time with that 35A load and still get 10-12 mi @ 30ish mph without pedaling at all

So where as Lithium Ion or SLA (even NiCd) may not be up to the task at 10AH (because then your controller is pulling 3.5C or 3.5 X the capacity of the pack) - the Lipo in 10AH configuration could handle up to 200A of continuous discharge and 300A peak ! Just shy of 10X what you need

You will want to wire it up better than Dark Angel did (he cited his wiring getting warm, that's a sign the wiring is too small for the power).

The short answer - considering the stock pack is SLA, I doubt you were getting more than 5 solid AH of discharge from it to begin with.. the 8S would get you going a tad faster which may end up using a little more power but... in the end, I would bet ya 1.00 (it's the largest bet I wager) that you will have atleast the same range as the factory 10AH SLA pack and actually you may find that you have better range since the voltage sag under a 35A load will be nearly nothing for a Lithium Polymer pack.

This is lithium polymer, not Lithium Ion (actually chemically those lithium ion cells he used from laptop packs are Lithium Ion Cobalt aka LiCo... the least stable of any Lithium chemistry imho).

-Mike

mwkeefer said:

Matt,

The 10AH he was citing was Either SLA or old fashioned laptop Lithium Ion... their C rating or "Discharge Capacity" which is the technical proper term is about 2C max, so a 10AH pack would provide up to 20, maybe even 25A without issue but the controllers are pulling 35 peak (which would be uphills, accelleration, etc) which for the battery chemistry he was using.... not really capable.

My personal eBike (my favorite anyway) is a 20" Nova folding bike (http://www.downtube.com) with a rear geared motor running at 18S Lipo which is 75v hot and 66v nominal (so it's about 2x the voltage your looking at)... my current limit is set for 35A and my pack warms up (it's supposed to) to about 95 degrees but remember these batteries are rated for 20-25C continuous and 30C peak... I run this bike on a 5AH pack most of the time with that 35A load and still get 10-12 mi @ 30ish mph without pedaling at all

So where as Lithium Ion or SLA (even NiCd) may not be up to the task at 10AH (because then your controller is pulling 3.5C or 3.5 X the capacity of the pack) - the Lipo in 10AH configuration could handle up to 200A of continuous discharge and 300A peak ! Just shy of 10X what you need

You will want to wire it up better than Dark Angel did (he cited his wiring getting warm, that's a sign the wiring is too small for the power).

The short answer - considering the stock pack is SLA, I doubt you were getting more than 5 solid AH of discharge from it to begin with.. the 8S would get you going a tad faster which may end up using a little more power but... in the end, I would bet ya 1.00 (it's the largest bet I wager) that you will have atleast the same range as the factory 10AH SLA pack and actually you may find that you have better range since the voltage sag under a 35A load will be nearly nothing for a Lithium Polymer pack.

This is lithium polymer, not Lithium Ion (actually chemically those lithium ion cells he used from laptop packs are Lithium Ion Cobalt aka LiCo... the least stable of any Lithium chemistry imho).

-Mike

Click to expand...

Your the best! I'm ordering tomorrow then! Damn paypal taking its sweet time sending me their 2 cents to verify my account..

Matt,
What all are you ordering? Spell it out so we can be sure you get all you need.

Also - are you able to solder?

You may want to grab a bag of 4mm gold bullet connectors (about 3.00) and say 2 meters each of 12G red and 12G black wire to wire your packs in parallel and also to make a cable to run between your controller and the pack (remember Dark Angel had wiring warming, we are going to avoid that right off)...

The connectors solder into place and normally I would advise ya to get the sheilded ones but, there are no more so just going to have to shrink tube them

One other thing you will want is a bag of 4S JST-HXT 10cm extension leads... they come 10 to a bag... this is what you will use to build a parallel harness for the balance taps for charging / balancing and discharge... simply put, you need to make a pair of 2 female to 1 male 4S balance cables (easy, trust me)... then connect them to each of your 8S packs in parallel..

Finally the cutout, what are you decided on the CellLog8 or the Gary Goodrum HVC/LVC 8S board?

-Mike
PS: Sorry I crashed out on ya last night.

So far I have:

T5800.8S.25 - Turnigy 5800mAh 8S 25C Lipo Pack $97.95
Accucel8150 - Turnigy Accucel-8 150W 7A Balancer/Charg.. $42.44
BOX-76g - Extra Size Cardboard Box and Packing 76g $0.00
KG55001 - Polymax 5.5mm Gold Connectors (10 pairs/.. $4.99
R12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98 x2 so hopefully 2 meters
B12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98 x2 also

I still need bag of 4S JST-HXT 10cm extension leads I cannot find it on hobbyking, and I need either a CellLog8 or the Gary Goodrum HVC/LVC 8S board, I have no idea what your talking about for this or where to get it or what to do with it :?

matt889 said:

So far I have:

T5800.8S.25 - Turnigy 5800mAh 8S 25C Lipo Pack $97.95
Accucel8150 - Turnigy Accucel-8 150W 7A Balancer/Charg.. $42.44
BOX-76g - Extra Size Cardboard Box and Packing 76g $0.00
KG55001 - Polymax 5.5mm Gold Connectors (10 pairs/.. $4.99
R12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98 x2 so hopefully 2 meters
B12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98 x2 also

I still need bag of 4S JST-HXT 10cm extension leads I cannot find it on hobbyking, and I need either a CellLog8 or the Gary Goodrum HVC/LVC 8S board, I have no idea what your talking about for this or where to get it or what to do with it :?

Click to expand...

The adapters were for connecting 2 x of the Turnigy's in Parallel - since your getting 1 for now, you don't have to get them (but you will when you add another pack in parallel)...

If you were going to do the 2P (2 packs in parallel) you would need to get:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10439
and
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9925
since they are sold out of the 10cm extensions...
All you want these for is their JST-HXT Male and Female ends - the other ends are tossers.

The cell log 8s - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10952 will suffice but it is not programmable (no updates to firmware) and you can't log data with it but it's only 13.26 (platinum price)...

Since you want simple... (IE: Plug and PLay) as much as possible... get 2 of the cheaper ones... each one will directly plug into one of the 4S balance connectors coming off the 8S pack... otherwise you will need to find a 9Pin JST-HXT connector and make an adapter to go from 2 x 4S balance plugs to 1 x 8S balance plug for connecting to a single CellLog8.

Good catch on the 5.5mm connectors - I had forgotten the 25C packs use those not the 4mm, sorry.

-Mike

PS:
The cell log 8s have a plug (2 wire) which works like a switch to drive a relay or somthing and interrupt the throttle output from your throttle (it wires between your throttle and controller) so that if the voltage of any cell drops below a certain point... the alarm triggers and your bike shuts down, this is to protect the Lithium Polymer battery.

You may want to consider adding a Watts Up or Turnigy Meter so you can visually see how many AH you have used - it works 100X better than the LED lights which are supposed to show you how much power you have left... it gives you real time Amps and Watts too... You would watch AH and when you get around 5.3 AH - stop and charge the packs

The meters I am referring to are:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6380
and nevermind, that's the only in stock meter I can find

-Mike

I'll get the watts up meter asap, so for now to get it all up and running does this look like a complete list besides the watts up meter?

T5800.8S.25 - Turnigy 5800mAh 8S 25C Lipo Pack $97.95
Accucel8150 - Turnigy Accucel-8 150W 7A Balancer/Charg.. $42.44
BOX-76g - Extra Size Cardboard Box and Packing 76g $0.00
KG55001 - Polymax 5.5mm Gold Connectors (10 pairs/.. $4.99
R12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98
B12A1062-06 - Turnigy Pure-Silicone Wire 12AWG (1mtr) .. $4.98
Celllog-8M - Cell-Log 8M Cell Voltage Monitor 2-8S Li.. $14.28

You will need 2 of the cell log8s for now - until you make a harness to adapt the JST-HXT 4S duals from your 8S into a single 8S plug (the charger should have a port for 2 4S plugs already so no big deal there)..

Then when you have it sorted to use a single CellLog8 - you can just post your spare up on ES for sale or, grab a meanwell S-350-36 (or a 48/24 and modify the voltage range it's easy)... calibrate it for 33.28v output and use the second cell log to turn the charger off when any cell reaches 4.16v.

I know... you have a charger coming, why would you want to do that?

350 / 33.28 = 10.51 AMP Charge Rate! In truth it would be more like 13.6 Amp CC/CV charger - what we refer to as bulk charging...

Now given that your bike has racks for 2 seperate batteries and if you were to do the 2 or even 4 8S lipo in parallel, they should fit in one of the stock 24v packs... on the other side you build in the FAST charger within a similar looking box...

Now you plug in via a PC cable or somthing anywhere and charge at 2C+ (30-40min)

I know you don't care now... but imagine riding 20-30mi, stopping for coffee (30min) and your off again with a full charge?

Welcome to LiPo!

But for now lets keep it simple, tack on an additional 8S Cell Log.

Combining these together to interrupt your throttle will take me a ride to Toys R Us or some research on the throttle you have... also I will donate a set of optocouplers and figure out how to use them to interrupt your throttle - ie: poor mans LVC (LVC = Low Voltage Cutout, very much what Dark Angel calls Protection ICs.) - I can get a circuit built up for you and shipped (as replacement warranty parts for customs, your in Canada right) in no time...

The other option (if he has them available) would be the Gary Goodrum 8S HVC/LVC - this wouldn't have nice display but it has all the other features and requires only one - available in kit, PCB and BOM or built form I believe.

That watt meter will be your saving grace though, unless a cell fails (it can happen, but rarely has to us) then you know you have 5.8 AH rated output... I would consider by charging to 4.16v per cell and ending discharge at 3.2 (maybe with a manual override for limp home mode) that will deliver about 5.5 AH of solid useable power - more depending on the true load.

So when you see 2.5 AH used from your (lets just for beginners sake assume 5AH capacity - margin of safety) pack, its either time to turn around and go back... back off the throttle or break out the charger (plug in if you do an onboard FAST charger).

If your not cool with modifying a meanwell for use as an Onboard 8S charger - I will be willing to work out your onboard charging needs and can order a supply for ya and modify it's output range to work with your 8S pack but even give ya a switch if you want to work with your 24v SLA packs too... The range on these supplies goes from about 40.00 to as much as 100.00 depending.

The other thing... I have a 24v Meanwell S-24-145 which I have already modified to allow tuning between 17v and 29v... This would be perfect at 17v mode for powering the new Turnigy charger your looking at and I believe i coud mod it to deliver the required 33.28v to charge your pack - you would be seeing approx 4.2A charge rate or just below 1C and although it's convection cooled - you can add a fan (or I can for you) and it will work from 110 or 220.

I paid 35.00 + s&h for it - if you wanted I can do the mods (you pay cost of mods, 35.00 for the unit and flat rate shiping 10.75 I think)

-Mike

thanks man I'll keep you posted, and I'll get 2 of those voltage monitors. Man I'm going to do what you say haha, start with the 1 pack and work up, sounds killer to go that far and just charge up and keep going. With a small trailer of spare parts I could go across Canada free that way! haha. Charge up at gas stations etc

First assuming 10AH 24v probably weighs in about 15 to 20 lbs...

8S LiPo 10AH would weigh in at 4.8 lbs... lets argue and call it 5 lbs (also in 1/4 or less the physical space)
Now since we saved the space and weight... lets go back up to the same weight as your SLA packs...

@ 15 lbs - you would have a 30AH pack (your controller could run at max load, full throttle 35A for 1HR most likely)
@ 20 lbs - you have 40AH pack - I'm going to estimate you got a true 5AH (maybe) out of the 24v SLA under your loads (assume nominal load is 1/2 of the max but a bit less... it's complicated) ... I think you said 10-12 miles range when the packs were working (may have been less than 5AH useable then) - so lets assume 12mi range per 5AH... With the 20lb pack and 40AH that's going to give you 8X the range of your stock pack in the same weight and form factor and with ZERO SAG at < 1C maximum discharge!... that works out to 96 miles per charge in the 20-22 mph range (guesstimate).

Even keeping it simple... lets say you do a 20AH pack (I usually figure 50% of my max load plus 10% for this) - that alone would provide you a 9.6 lb pack (same rough weight as a single SLA 10AH battery) and range to travel an estimated no pedal of 48 miles @ 20-22 mph range or better.

That pack would require 4 8S packs in parallel...

Now get this, I spoke with my friend tonight who has an eZip and turns out he already is running it at 37v on 10S Lipo (2 x 5S packs in Series (black to Red)) and he says it's a cooking blast! I believe he got a 36v controller also...

The fun part:

Here is the 36v Currie Controller and Throttle for $39.99
http://www.monsterscooterparts.com/cu36v30a6co6.html

Although if you wanted to do 36/37v the motor you have wuold probably be fine, these are available:
http://www.electricscooterparts.com/motors.html#36v

From 350w up to 1000w with the gearbox an all ready to go in 36v.

I know you have already made up your mind, just adding to the fire after speaking with a friend I see how simple it could be...

Another option - go RC drive... low kV motor with 3:1 first stage and 11t to stock rear gear for the final stage and you could convert the eZip/iZip clone into a 30-40mph beast which will do wheelies on command

-Mike

You mentioned discharging the Lipo down to 3.2V...I was under the impression that was a bit low? I have only taken my packs (10AH 25C turnigy) down to 3.7 volts so far because I thought 3.6V was the lowest you would ever want to go...

Just wanted to clarify for us Lipo newbies.

BTW, OP, you are going to LOVE the HK turnigy 25C lipo...I have been doing 40 and 50 mile trips on my recumbent with the 10AH pack with power to spare at the end of the trip (maybe even more than I thought if 3.2V is actually safe)

KTP,

Lipo chemistry wants no cell below 3V... that said, the less you use (capacity) the more "in balance" cells will stay and there is thought to be some merit that discontinuing when 40% remains will (maybe) increase cycle life.

Now at rest, after not having a load on a pack... cells may be at 3.2 when previously under load (as in a few moments, 3-4 before) of 30-40A (typical eBike) and when under load any given cell hits that 3V marker.... That's time to stop, as in maximum safe time to stop.

There is another factor - the higher the C rating of the battery, the longer the voltage will stay higher... This also means the cliff effect kicks in sharper so maybe everything is fine at 3.6 then 3.5 but as soon as a cell reaches 3.4 it rockets down to 3v within a few seconds (maybe 20-30)... That tends to be the case with the Turnigy Lipo but then their 5AH packs are made of 5300mah cells... no idea on the 8S packs, but I have not heard any complaints about the packs.

So 3v is the maximum, if you were to charge to 4.2 and discharge to first cell hits 3v... I think you would see more like 6.2 AH out of the 5.8 rated packs, maybe more... but that's the farthest you can really go safely.

Now for maximizing the cycle life of the packs -
1.) Common practice is an LVC between 3.1 - 3.3v, that's when most of us consider our packs empty... you may still have cells at 3.4 or even 3.5v but once you hit this LVC either stop using the pack or do as I do and engage a very current limited mode (I leave it to you to figure it out, but I have some suggestions if you like) - again a limp home mode (like a failed ECM in a car)

2.) Common practice is a HVC of 4.15 - 4.18v per cell... 4.15 seems to deliver more cycles (I've got > 1000 on a pack here) and can't hurt the packs no matter what... however you will loose approx 230 mah worth of potential power or in one of my applications approx 1/2 mi of range.

300-500 cycles @ + 1/2 mi
or
1000 cycles @ - 1/2 mi range - DING DING DING winner.

Now for your situation... 3.7 is the nominal voltage but 3.6 seems far too high for LVC... your missing out on about 18% more useable power (while still leaving 20% remaining)... (my math may be a tad off).

I would go lower towards 3.5v - basically watch your packs past 3.6... when the balance goes > .30mv or a cell hits 3.2v, then do a cutout. This will keep your packs better balanced and also maintain higher cycle life (probably).

Hope it helps!
-Mike

OMG big change. Now going with a Golden Motor 36v 500 watt hub motor. I have a 36v controller for it also and throttle. Would 2 of these work to give me a 5ah 36v battery pack?

http://www.unitedhobbies.com/hobbycity/store/uh_viewItem.asp?idProduct=9174

Let me know, if so I'll buy 4 of them for a 10ah 36v pack.