Want to change from SLA to lithium

johnwalt · Mar 4, 2018

Hi all, I'm sorry if this seems like a stupid question but I've spent hours searching to figure it out myself. I pretty much grew up in a bike store in the 60s and 70s but of course we didn't have ebikes then much less lithium batteries. I've been using my Mongoose (Currie) CB24V450 as my only transportation for 11 years now. 3 motors and too many SLAs later I'd like to know what lithium battery would replace the 2-12volt 12ah SLAs (in series 24volts). Motor is 450 watts and I'd like similar performance. Any simple advice appreciated, I don't know what BMS, 6s 10s etc mean. Thanks, John.

Jon NCal · Mar 4, 2018

First thing I would do is figure out where you want to mount your batteries. Do you want to put them where your existing lead batteries are? Or perhaps mount to a downtube mounted bottle battery? Or rack top? Look at some of the 24v batteries on bmsbattery.com to get some ideas:
https://bmsbattery.com/73-24v-battery

johnwalt · Mar 4, 2018

It looks like I can put it behind the seat tube where my SLAs are. What is probably a dumb question to most of you is---since I have two 12V 12AH SLAs in series do I need a 24V 12AH or a 24V 24AH lithium ?

999zip999 · Mar 4, 2018

24v 12ah or more. Not all battery cells are the same. Cheap laptop cells or Hi Power or high capacity cells. Meaning the batteries you buy at the 99 cent store or Duracell. This is just an example. Make sure you know what brand name and model number of the cells that are used in the battery pack. Lots of Amazon and eBay junk batteries out there.

LockH · Mar 4, 2018

Hehe... Hi NY... My first electric two wheels were 2x 12V SLAs... "Cheap" to buy, they wore out "too fast". "Dead" batts used to make great door stoppers (saving up to recycle) but I ran out of doors. [grin]

So lithium the "way to go". More expensive to buy, but much cheaper per mile in the long term. About anything lighter per stored Wh vs lead... although "straight" Lithium-Polymer being sorta tricky to look after. Fav. lithium includes Lithium Iron Phosphate ("LiFePO4") and LTO... lithium titanate oxide). Check re highest power density per pound. Then check # of times to recharge... and don't exhaust/run flat every time.

G'Luck
L

speedmd · Mar 4, 2018

6s (six lithium polymer or ion cells in series) will be slightly less voltage (4.2 x 6 = 25.2v hot off the charger) than the 2- 12v ( 2x 13.6v = 27.2v hot off the charger) lead bricks. This will not be very noticeable as your lead bricks drop quickly and sag much more than the LI bricks will. You also will be able to use a much higher percentage of the capacity allowing a lower capacity battery to effectively replace the lead bricks. You can read a bunch of threads on converting but it would be safe to say the one 10ah 6s lipo brick would more than equal the two lead bricks in real use. https://hobbyking.com/en_us/multistar-high-capacity-6s-10000mah-multi-rotor-lipo-pack.html

johnwalt · Mar 4, 2018

Thanks all but another dumb ? question.What are the 7 small wires coming out of the Hobbyking battery for ? I only have a pos and neg going into my controller.

speedmd · Mar 4, 2018

They are balance leads. There is a negative and others connect to each cell voltage step (positive side of cell or - cell group if that voltage step is made with more than one cell in parallel) in increasing order. You use them to charge, monitor when balance charging or monitor individual cell voltages in use or storage.

LockH · Mar 5, 2018

Hehe... ES Search "Search found 71127 matches: bms" aka "Battery Management System" ie "watching" individual cells. :wink:

dogman dan · Mar 5, 2018

since most commercially produced e bikes these days run 36v or 48v, your best bet might be pingbattery.com

There you can still get a reliable 24v 10 ah battery, with bms. It will have approximately double the range of your sla setups. If you can afford it, go for a 15 ah and really extend range while also likely increasing the lifespan in years.

http://www.pingbattery.com/servlet/the-4/LiFePO4-Lithium-Iron-Phosphate/Detail

LockH · Mar 5, 2018

Hehe... The quickest "recharge" I know is to just swap batteries. :mrgreen:

A "spent" one for a "full" one. Were it I? I'd buy two smaller packs, then ride while the other is recharging. BTW, re charging - and discharging - "slower" is "better", chemistry-speaking. Then for longer distances yah can just parallel connect your two packs together to double yer Ahs. So generally "lighter" is "better" as requiring less energy to accelerate from stops, "lift" up hills/against gravity... See "kinetic energy".

Know any friends at the "other end of town"? Leave THEM one pack "fully" charged w/charger to trickle charge on standby. "Drop by" for a "recharge"/swap pack and keep on traveling. Or not. :wink:

Raisedeyebrows · Mar 5, 2018

The 450 watt motors in the Mongoose seem to be able to handle 36v no problem with an upgraded controller, this modification combined with a Lithium-ion battery really peps them up.

I changed these two parts on a bike with the same motor on it so I could use 36v lithium-ion batteries (easier to find than a 24v one), the two parts along with using a 36v battery result in a bit higher top speed and better performance, the two plug right in to the Mongoose 5 pin wiring, plug and play:

ctl-101197 36 Volt Controller with 5 Pin Throttle Connector (Model: XK-022D)
1 $59.95 $59.95
THR-101117 Currie - Half Twist Throttle with 5 Pin Connector and 36 Volt LED Meter Currie - Half Twist Throttle with 5 Pin Connector and 36 Volt LED Meter
1 $28.00 $28.00

http://electricscooterparts.com/speedcontrollers36volt.html

Purchased one of these 36v batteries with quality Panasonic cells, great price but not a lot of amp hours, works great though:

https://www.ebay.com/itm/Panasonic-NCR18650PF-2900mAh-36V-Rechargeable-Li-Ion-Batteries-Battery-Pack-NEW/152923892419?hash=item239af96ac3:g:eoAAAOSw5VtaPE6n

wesnewell · Mar 5, 2018

In Sept. 2016 I replaced the 2 12v 7ah sla batteries in my UPS with 5 year old 10ah of 7s rc lipo from HK. They are still working great today and expect them to last another 5 years. If I were you, I'd do the same for your situation. Now my ups only charges them to ~28V, which is 4.0V per cell. I'm assuming your charger won't exceed the 29.4V max charge for a 7s lipo pack, so it should be perfectly safe to use it even without a bms, although you could just get a separate 7s lipo charger to use if you want, or just put a 7s balancer on it. Lot's of safe ways to do it. I don't use any balancing for the pack in my ups. 10ah of 7s lipo will provide more power and range than your current sla battery pack, and will only take the space of less than 1 of your 12ah 12v sla batteries. IIRC, the curie controller draws ~35A max. A 10ah 20C rc lipo pack is rated for 200A continuous and 300A burst, so you won't see the sag in voltage you do with the sla batteries either. Whatever you decide to use make sure it's rated for at least 10C imo.

LockH · Mar 5, 2018

^^ Oh oh... "Lipo"... Lithium-polymer... Like many perhaps, I'm too lazy and stupid to maintain "carefully"/"properly". But EG LiPO... I'd be recharging in an outdoor/separate fireproof box. Probably with fire extinguisher handy. :wink:

[youtube]CnNId0mDnBo[/youtube]

wesnewell · Mar 5, 2018

The above video proves nothing more than anyone with the knowhow can start a lipo fire. It's not hard. Nor is it hard to get an SLA battery to explode, or an 18650 battery for that matter, Same goes for most any battery type made, including all the lithium batteries recommended in this thread. If you want to be totally safe, walk. Even your car can be made to explode and catch fire. Of course walking can be dangerous too, so just stay at home. How safe is that anyway. All this lipo fire crap is just that, crap. I guess if you have the intelligence of a 3 year old, you probably shouldn't use it, or any other battery. Here's another take on how dangerous they are, and what it may take to cause a major problem.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=27241

LockH · Mar 6, 2018

Hehe... ESB "Search found 17500 matches: fire"... may appear a popular topic?

... or how `bout ES thread "There was a fire at my house today while I was not home.", to date "viewed 167,000+ times".

Hehe... On YouTube, "About 146,000 results" for "lipo fire"

So even thought "it" "never happens", still fun to talk about! I know... it's a plot from the folks that wanna sell fossil remains for the hydrocarbons content aka gasoline and diseasal...

As the energy content density goes up and up... more and more to play with! ... just don't release it all at the same time? Maybe goggle search "vehicle fires" from gasoline getting "out of hand" from accidents or other stupid human tricks... :wink: :wink:

dogman dan · Mar 6, 2018

FWIW, Amberwolfs fire was not caused by his batteries, or chargers.

But mine was,,, a "safe type" 18650 pack with bms. :roll:

So all my shit is outside now. When I burned my house I got a nice lipo bunker in the process, the old ruined kitchen stove.

I totally advise all lithium to be charged and stored outside your living area. Attached garage was not good enough for us, we could have died in the fire real easy.

Charge it outside, even the "safe" lifepo4 from ping.

johnwalt · Mar 6, 2018

Does lithium charge ok in subzero temperatures ?

Jon NCal · Mar 6, 2018

johnwalt said:
Does lithium charge ok in subzero temperatures ?

No, charge at room temperature only. See: http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

Li ion can be fast charged from 5°C to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures because of the reduced diffusion rates on the anode. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. The internal resistance of all batteries rises when cold, prolonging charge times noticeably.

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a sub-freezing charge. This is permanent and cannot be removed with cycling. Batteries with lithium plating are more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers (Cadex) prevent charging Li-ion below freezing.

speedmd · Mar 6, 2018

Most Li cells are safe to charge down to freezing temps. Below that some types will be damaged. Some types can be charged safely at low current levels below freezing. Looks like some battery preheating should be standard operating procedure in colder areas for those using regen.

dogman dan · Mar 7, 2018

Above froze, meaning the battery is above freezing, ok.

Below, when the battery itself is froze, you must thaw it, which will take forever, before you use it, or charge it.

It does not take a ton of insulation to keep a battery warmer than 32F, if its only 25F overnight. So the best way to go is not letting it freeze solid unless its under long term storage.

Best bet for keeping a battery thawed overnight in a real cold climate is a reptile heat pad. Gentle heat, won't burn the thing, but enough to keep an insulated box toasty in really cold weather.

Bring a battery that is warm from inside back out, and you can charge it in very cold weather. Lots of thermal mass, so it takes time to freeze it. Again, some insulation would be needed though.

LockH · Mar 7, 2018

One "problem" perhaps... Gotta handle "stupid human tricks". So I'm always more in favour of any tech that's "bullet-proof" (as much as possible...) :wink:

speedmd · Mar 7, 2018

Below, when the battery itself is froze, you must thaw it, which will take forever, before you use it, or charge it.

It does not take a ton of insulation to keep a battery warmer than 32F, if its only 25F overnight. So the best way to go is not letting it freeze solid unless its under long term storage.

Best bet for keeping a battery thawed overnight in a real cold climate is a reptile heat pad. Gentle heat, won't burn the thing, but enough to keep an insulated box toasty in really cold weather.

Some good points Dan. Will make the new Li battery box enclosure for the UTV that sits outdoors or unheated shelter with heater and some removable winter side panels so we can deal with the cold start / charge issues more easily.

LockH · Mar 7, 2018

^^ Watt he said. At one point, living in the "Great White North", one Canadian guy has plans to sacrifice some Whs to power a nickel chrome wire ceramic heating pad to keep my cells warm... you know, when the pack wasn't indoors/aka "warm". :wink:

mark5 · Mar 7, 2018

dogman dan said:
since most commercially produced e bikes these days run 36v or 48v, your best bet might be pingbattery.com

There you can still get a reliable 24v 10 ah battery, with bms. It will have approximately double the range of your sla setups. If you can afford it, go for a 15 ah and really extend range while also likely increasing the lifespan in years.

http://www.pingbattery.com/servlet/the-4/LiFePO4-Lithium-Iron-Phosphate/Detail

johnwalt could look into using Kobalt 24V tool batteries. vuaeco's Youtube channel has videos on using them. A Kobalt 24V 4Ah battery is $50 right now.

Want to change from SLA to lithium

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