PDA

View Full Version : New batteries for scooter



podolefsky
20 September 2011, 1628
My R Martin's lead batteries are finally on their last legs. I get maybe 10 miles of range before they sag to dangerous levels.

So...what to replace them with. The lead pack is 60V, but it can handle up to 80V. A 40Ah, 72V pack would be perfect.

My options, as I see it, are:

- 72V, 40Ah GBS pack. ~$2500 with charger and BMS. Rated for 2000 cycles (or more) if treated nice. Easy to build, pretty much turn-key solution.

- 76V, 40Ah LiPo. ~$1000 plus BMS/charger(s). From what I recall, expect around 1000 cycles. PITA to build. But very light and small...and it would be a good learning experience.

Both of these would fit in the existing battery box without modification.

I'm not interested in Headway - as I see it, not a significant advantage over GBS (for my scooter that pulls <100A).

What do y'all think?

frodus
20 September 2011, 1646
$1000 for lipo? 18 cells, 8 parallel of the $8.50 turnigy's?

podolefsky
20 September 2011, 1704
About - prices fluctuate. 4s1p Turnigy packs come up for $25 each on occasion. 40 of them to make 20s8p is $1000.

frodus
20 September 2011, 2041
ugh.... laborious and lots of connections.... good luck!

podolefsky
20 September 2011, 2117
yup - that's why i'd lean toward the GBS. simple and reliable.

but it's also going to be winter soon...nothing else to do than solder about 1000 connectors

frodus
20 September 2011, 2152
watch out, you'll turn into Ted!

Nuts & Volts
20 September 2011, 2234
watch out, you'll turn into Ted!

Well yea, we all get old and crazy at some point :D


Noah,
To be honest I would strongly consider the LiPo path just because of the potential money savings. However I would wait on some data from Ted, Coniscan or someone else running these 20C cells. I have only used a small pack of them. The power rating was good, but I am still hesitate on whether the full (well 80% DOD) Ah can be pulled from them. I have gotten about 70% capacity out of them and to me that still makes them worth the cost savings and extra time.

I would actually go the manual BMS route too. Cell-logs with bulk charging and then RC charger to balance every 10 cycles or so. Something like that would allow you to use any standard charger and would only cost you about ~$150 ($85 cell logs, $40 RC charger, misc) plus charger cost.

If you want the scooter to be a super simple turn key ride that wont require routine tinkering then the GBS would be the way to go. I take the tinkering for the money savings 80% of the time (well actually, I give up on the tinkering solution 20% of the time :))

teddillard
21 September 2011, 0328
ugh.... laborious and lots of connections.... good luck!

Yeah, if you use Andersons. :p
(or the individual cells...)

I used the hardcase packs. http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=18631
$23 for a 4s1p

You're completely off the mark on this Travis, due respect. The Turnigys are a dream. Even making up those miniblocks took about 15min per block, and everything is easily connectable and unconnectable. The balance tab block I made is also really simple and works great. The 4mm bullets carry crap tons of current. I don't see any need to run the individual cells, frankly. The occasional balance charge with a routine bulk charge is a strategy rc and others have been using for over a year now.

I think Kyle is dead nuts on. Except for waiting for data. If you're waiting for me to provide it, it's gonna be a loooong wait. And hell, this is a frikkin scooter, right? You figure you're gonna need more than 20C?

...but then, I'm old and crazy. :)

Nuts & Volts
21 September 2011, 0412
On the data side of things I just meant you may not get as many Wh out of a 72V40Ah Turnigy pack as you will get out of a 72V40Ah GBS pack before LVC kicks in (at the same power draw). I dont have much data to argue either way on this point. The Turnigy will have less voltage sag so maybe that will make up for potentially lower Ah.

We need Travis to test one of these Turnigy cells on his nice CBA thingie :) pretty please

podolefsky
21 September 2011, 0814
Hmmm...now you all have me thinking...damnit.

My scooter is only 3kW. At 60V, that's 50A. 1.25C on a 40Ah pack, so the 20C Turnigy's are overkill by a factor of, um, 16x. The only reason I'd want 40Ah is range.

So is the charging strategy something like:

- Balance charge all the packs first time
- Bulk charge most of the time (no balancing)
- Unplug the packs and balance charge them with an RC charger (say every 10-20 charges)?

The other thing I'm wondering is, does the 1000 cycles rating sound about right? I couldn't find any data on that, just heard Lipo is less than LifePO4, especially compared to prismatics.

frodus
21 September 2011, 0902
You're completely off the mark on this Travis, due respect.

Nah, you just don't like my opinion....

Yes they're great cells with great performance, but how they're connected using hobby packs/lots of cheap barrel connectors (high resistance) that can come loose easily and balance leads for every parallel pack isn't a very robust and efficient way of putting a pack together.

Take a look at Crodriver, Cellman, Viktor, John Wayland, Ripperton who've used pouch cells....

frodus
21 September 2011, 0904
The Turnigy will have less voltage sag
[citation needed]


We need Travis to test one of these Turnigy cells on his nice CBA thingie :) pretty please

I've offered several times to test anything people send me if I keep it, they pay for the service otherwise. Some people said they would, but I never got anything.

teddillard
21 September 2011, 0924
... barrel connectors (high resistance) that can come loose easily...

(citation needed on both counts)


Nah, you just don't like my opinion....


Well, my friend, I love your opinion, but when it runs contrary to my experience, yes, I guess you could say that if you wanted to. :D



Yes they're great cells with great performance, but how they're connected using hobby packs/lots of cheap barrel connectors (high resistance) that can come loose easily and balance leads for every parallel pack isn't a very robust and efficient way of putting a pack together.

Take a look at Crodriver, Cellman, Viktor, John Wayland, Ripperton who've used pouch cells....

Links would be great if you have them on the pouch cells.

Nuts & Volts
21 September 2011, 0938
[citation needed]



I've offered several times to test anything people send me if I keep it, they pay for the service otherwise. Some people said they would, but I never got anything.

Travis, I need to find my alltrax data again to double check, but I know I was able to pull 280A from a 10Ah pack with the cells falling to ~3.32V. So that is 28C. I will check the data and find the actual voltage drop from the resting voltage that goes with this data. I believe Noah has seen 10C on GBS cells falling to 2.8V ?? but hopefully he can correct my numbers.

PM sent on the turnigy testing.

podolefsky
21 September 2011, 0950
I believe Noah has seen 10C on GBS cells falling to 2.8V ?? but hopefully he can post them.


I've seen 500A (8.3C) from my 60Ah GBS cells, with sag to 2.8V / cell (68V / 24 cells). Haven't seen 10C.

http://www.colorado.edu/physics/EducationIssues/podolefsky/EV_project/batt_motor_amps_data.png

frodus
21 September 2011, 0950
Don't really need a citation.... I've got direct experience with anderson connections, tamiya connections, molex, deans plugs and barrel plugs against bolted or soldered connections. For 1 battery it's not that much, put a few in series, then it compounds. Every time I've used connectors, they always heat up more than the soldered or bolted connections in the same exact application.

As far as the connection "looseness" .... just give em a tug. I've had several RC vehicles with barrel connectors on the motor/controller, I'm well aware of their strength. Most of my meter leads are of the same type as yours. If you secure them properly this isn't an issue, but it's still an issue with the connector itself if you don't watch out.

frodus
21 September 2011, 0952
I was able to pull 280A from a 10Ah pack with the cells falling to ~3.32V. So that is 28C. I will check the data and find the actual voltage drop from the resting voltage that goes with this data.

PM sent on the turnigy testing.

Yeah, you need the rest voltage, the 1C voltage and the 10C voltage to compare correctly. Surface charge is a bitch and very misleading.

will reply on that PM asap

podolefsky
21 September 2011, 0955
So...getting a little astray from topic of "what should Noah put in his scooter?"

I agree lipo is a lot more work...but Ted is making good progress on refining pack building. And others (as cited by Travis).

A separate lipo thread on all the solutions people have come up with would be great (wasn't there a thread started on that already?)

teddillard
21 September 2011, 0959
Every time I've used connectors, they always heat up more than the soldered or bolted connections in the same exact application.

I guess I'm still thinking of your previous comment on the Andersons vs the bullets. My understanding is that the bullets handle more current, and plenty for the pack, than the Andersons you mentioned there.

But I'm still going to go back to the purpose of the build and the original question. This is for a 40ah 72V scooter pack. We're not building a car, or a race bike, we're building something that will probably not pull over 200 amps. Is that fair? It doesn't need a pouch pack, the Turnigys will do just fine.

(cross-posted, I'm right there with you Noah...)

podolefsky
21 September 2011, 1004
More like 50A (as stated above, my scooter is rated at 3000W at 60V).

Honestly, at this point the only reason I would go with lipo is for fun and learning experience. Pretty clear GBS is the simplest and most robust solution, and more than enough battery for my needs.

frodus
21 September 2011, 1004
fair enough Ted.... but I'd still like a datasheet on those bullets if you can email me one.... I'd like to see what peak and continuous ratings are. For me, I'd keep it simple.... especially after going through 4-5 different designs on my headway pack.... I should have gotten some GBS or CALB!

Noah,
Not to sway you either way, but just wanted to let you know about headways, prices are $15 each from Current EV Tech right now.... $1440, bussbar and the building blocks in stock.

podolefsky
21 September 2011, 1022
Travis, I doubt you would have fit 115V of GBS in your bike. Maybe 40Ah. 72V, 60Ah is a tight fit in mine, and it's a very roomy frame. Headways are more energy dense.

Good to know about the deals at currentevtech. Once I add charger and BMS, it's close to the GBS package price...but still worth considering.

frodus
21 September 2011, 1035
I'm only doing 40Ah, 144 cells, 40Ah 36 series. Yeah, they're a little more energy dense though, but not when you add all of my connections and battery frames.... it's almost a wash.

podolefsky
21 September 2011, 1038
I'm only doing 40Ah, 144 cells, 40Ah 36 series. Yeah, they're a little more energy dense though, but not when you add all of my connections and battery frames.... it's almost a wash.

Hmmm...good point.

I think the reason I determined I could fit more kWh in Headway is the small format. Easier to build around the frame constraints.

podolefsky
21 September 2011, 1040
Anyway...scooter...it's my main mode of transportation, so reliability is pretty high. I think I'll go with GBS (when I can afford it). Save Lipo for a go-kart :D

Allen_okc
21 September 2011, 1049
OK Noah - where's those photos of your scooter?

inquiring minds wants ter knows...

frodus
21 September 2011, 1056
I think you'll be fine either way. I mean go with turnigy if you want, but spend some time thinking about the most robust way ot connecting everything so problems with connector losses, loose connections and rats nest of wires can be avoided or minimized.

email me, I can try to source a few options on batteries.

podolefsky
21 September 2011, 1116
OK Noah - where's those photos of your scooter?

inquiring minds wants ter knows...

over here (http://www.elmoto.net/showthread.php?1638-Picture-Thread!-Where-our-bikes-are-at-now!&p=20494&viewfull=1#post20494)

DaveAK
21 September 2011, 1216
I'm going to suggest SLAs, just because no one else has. :D

podolefsky
21 September 2011, 1218
That would be the cheapest easiest route...but since the last SLAs I had lasted barely a year, it's a waste of money in the long run.

DaveAK
21 September 2011, 1221
That would be the cheapest easiest route...but since the last SLAs I had lasted barely a year, it's a waste of money in the long run.
Yeah, I was just being a smartass. I'd put my money into LiPo. If for no other reason than I haven't done it yet. Single cell or RC packs would just be one of the design decisions to make.

Nuts & Volts
22 September 2011, 0434
I know this is a little bit off topic, but here is the data I promised. This is taken straight from the log files from my Alltrax 7245 and the numbers are in order of occurrence on the ride. Pack setup was 20s2p

My turnigy cells were at 3.71V resting and dropped to 3.32V at ~255A. Another data point is 3.675V resting, dropped to 3.305 at ~277A. Hell here is one more 3.615V resting, dropped to 3.34V at 215A. These numbers put the cells+wiring at 2.5 to 3 mOhm internal resistance.

Allen_okc
22 September 2011, 0706
:confused:

teddillard
22 September 2011, 0822
Want to have some fun? One word. Shorai LFX36L3-BS12 Lithium Iron Battery. Wait. More than one word. :D

http://www.shoraipower.com/p-210-lfx36l3-bs12.aspx

frodus
22 September 2011, 0826
Now that's data!
Can't wait to test those cells you're testing.

podolefsky
22 September 2011, 0829
I know this is a little bit off topic, but here is the data I promised. This is taken straight from the log files from my Alltrax 7245 and the numbers are in order of occurrence on the ride. Pack setup was 20s2p

My turnigy cells were at 3.71V resting and dropped to 3.32V at ~255A. Another data point is 3.675V resting, dropped to 3.305 at ~277A. Hell here is one more 3.615V resting, dropped to 3.34V at 215A. These numbers put the cells+wiring at 2.5 to 3 mOhm internal resistance.

Cool, thanks. So just to get this straight, those are 5Ah packs, 2p to 10Ah total. So about 21-28C...are those 20C rated packs, or higher?

I think (as Travis has said) that you need two data points at different currents, say 250A and 100A, to get a good estimate of IR. Resting voltage gets thrown off by surface charge and pack discharge. (I think).

Anyway, more related - how are your cells all wired up Kyle?

Remotecontact
22 September 2011, 1552
1000 cycles at what DOD? A cycle number alone is kind of meaningless without DOD.

That's mostly right, you don't need to unplug the packs to balance charge. Take a look at my modules, notice the separate balance port. Also during the bulk charge I charge to a more conservative 4v/cell which acts as some electrical "slop" in case the cells to get slightly unbalanced in between balance charges.

I also set a conservative LVC. You lose available energy but I find that completely fine because lipo is so energy dense, in kwh/L and kwh/kg meaning in the same space and weight of another chemistry you can have more energy with lipo which more than compensates for the available energy loss due to conservative (pack level) LVC and HVC. Not to mention Wh/$.

In the same weight and cost of a GBS package you can have much more kwh of lipo so that your DOD becomes much lower each cycle, therefore extending cycle life of the cells greatly. The difference in cycle life from 80% DOD to 40% is huge.

podolefsky
22 September 2011, 1615
thanks rc. i was thinking a typical DOD like 80%. just so i could compare to other cells rated to 80%.

everything else you say makes a lot of sense. and yeah, on an average day I'd probably take them to like 25% DOD, just running around town...so they could last a very long time.

Remotecontact
22 September 2011, 1934
Despite that entire post...if this is a main mode of transit, and if you already used it with SLA (making any kind of lithium a huge improvement) then I would go with large format cells. Especially that you already have experience with running them on your elmoto and this being a relatively low current machine. I just wish those GBS cells were a tad cheaper.

DaveAK
22 September 2011, 1942
Despite that entire post...if this is a main mode of transit, and if you already used it with SLA (making any kind of lithium a huge improvement) then I would go with large format cells. Especially that you already have experience with running them on your elmoto and this being a relatively low current machine. I just wish those GBS cells were a tad cheaper.
See, this makes sense. However I'd go with LiPo 'cause it'd be fun. :D

podolefsky
22 September 2011, 2011
Yup, simple and reliable is probably the way to go. I think the SLAs will make it through the winter. In the meantime, I have a couple lipo cells on the way to play with. I'll find out how much fun it is, then decide.

GBS cells alone aren't that bad. 60Ah are $245 for a 4-pack. About the same as TS or CALB. If you get the whole kit it includes BMS and charger, and ends up about the same as other prismatics with a similar setup.

Remotecontact
22 September 2011, 2300
See, this makes sense. However I'd go with LiPo 'cause it'd be fun. :D

Exactly my point.

podolefsky
24 September 2011, 1630
question on charging lipo: can the rc balance chargers be used on packs in parallel? like say i but 6 5Ah packs in parallel and buss all the power and balance leads together. will an RC charger still balance and charge the packs correctly? or will they fail because they're expecting 1p?

Coninsan
25 September 2011, 0246
question on charging lipo: can the rc balance chargers be used on packs in parallel? like say i but 6 5Ah packs in parallel and buss all the power and balance leads together. will an RC charger still balance and charge the packs correctly? or will they fail because they're expecting 1p?

Works just fine, though it'll take more time the more cells in parallel. Many RC dude do this to save having to plug in 10 or more batteries and charging them individually.
Series charging should also function just fine, the batteries should stay in balance (DeltaV +/- 10mV) due to the low cell resistance. A bi- or tri-weekly maintinance balance charge with an RC unit should keep them nicely in balance over time.

teddillard
25 September 2011, 0427
Noah? Dude? You haven't been paying attention... :D

http://www.elmoto.net/showthread.php?1453-The-LiPo-Project-%28The-R5e%29

podolefsky
25 September 2011, 0940
Noah? Dude? You haven't been paying attention... :D

http://www.elmoto.net/showthread.php?1453-The-LiPo-Project-%28The-R5e%29


um...yeah...just not close enough attention. i got distracted by bullet connectors...

I did read through the thread, the one thing I didn't see is how it's working out over time. I assume just fine?

teddillard
25 September 2011, 0945
um...yeah...just not close enough attention. i got distracted by bullet connectors...

I did read through the thread, the one thing I didn't see is how it's working out over time. I assume just fine?

Remotecontact has been using it for street riding and commuting for a lot longer than I (me?), I'll defer to him...

Remotecontact
25 September 2011, 1040
question on charging lipo: can the rc balance chargers be used on packs in parallel? like say i but 6 5Ah packs in parallel and buss all the power and balance leads together. will an RC charger still balance and charge the packs correctly? or will they fail because they're expecting 1p?

This goes back to understanding how a charger works. Chargers don't know what P is. In a set of well matched say 2.5ah cells in 6s2p, it's the same as a 6s1p pack of 5ah cells to the charger.

All that these chargers care about is voltage. CC/CV. They're going to keep on chugging until the voltage rises, not until it hits 60ah or whatever.

Right now on my desk I'm cycling/balancing one of my 6s8p modules with one 35 dollar 200w hobbycity charger and it works like a champ. On the display on the charger right now I have 41.846AH in. Each cell is at 4.20v, on the cell readout display on the charger and manually checked by me with a multimeter.

podolefsky
25 September 2011, 1208
thanks. that makes perfect sense.

Remotecontact
25 September 2011, 1723
Anytime brother.

dazarooney
03 October 2011, 1030
Yup, simple and reliable is probably the way to go. I think the SLAs will make it through the winter. In the meantime, I have a couple lipo cells on the way to play with. I'll find out how much fun it is, then decide.



Yeah I agree, that'll be best.