SLA battery question: real world expectations 48V

[renstyle]

First time poster, long-time lurker. Looking for any real-world experience with a similar setup.

I need to whip up a quick and dirty e-bike to assist with a 5-mile commute. I fully expect to assist with the motation by pedaling. I want a throttle setup, and doing without the cadence-sensor pedal assist. I just need something to help offset the wind, very slight hills, etc.

Max speed on level ground: 15-20mph tops
Desired Max range at 20mph: ideally 5-10 miles (with me helping by pedaling, *not* with traditional pedal assist)
26" MTB
Brakes MTB stock V-brakes
Rider weight: 245lb
Terrain: mostly flat, some short hills under 20% grade
Budget: sub $300 (I know it's low, please read on)

Looking to get this kit to start (rear wheel): http://www.ebay.com/itm/48V1000W26-...hash=item43e88e6b02:m:mZNivwLXJUmsCcYH_lRzZCA

No need for a display, already own a decent digital speedo/odometer. Battery life indicator would be nice above the 3-light indicator in the kit, but not necessary now (no long trips).

Batteries: to start I am going SLA. The reason for this is because I have access to about 3 dozen 12V 7.2ah cells that have been reconditioned (former UPS batteries). I can get them for next to nothing. I'm saving up for a Lunacycle Shark 48V, but SLA will do for a daily commute (for now).

I already have two 3-stage 12V smart chargers, and there is a 48V charger included with the kit.

I'm going to use some Anderson Powerpole connectors with 10GA cable to tie 4 of these 12V batteries together with a harness that will let me charge as either:
4 batteries wired in series (48V) or as 4 batteries in parallel (12V).

A 7.2Ah, 48V pack weighs in at 21.5lb.

My plan is to have a pack on trickle charge at home, another on trickle at work (5-6 miles away), and a third pack on the bike itself. It sounds crazy, but I am blessed with an abundance of lead for the time being.

I know SLA is old news, but could anybody lend their opinions and experience as to whether a 7.2Ah pack could get the job done for a while? Bumping up to 8 batteries on the bike at one time (44lb !) seems a bit too much.

What do you think?

 

[Chalo]

That's too much motor kit for your performance requirements. The controller in particular is at least a 25A unit, which will be needlessly hard on the batteries you have in mind, and which will take away some of your more economical choices when you choose to get a lithium battery.

For your stated goals, a 500W or even a 350W kit will do the job, giving you more range and going easier on your batteries in the meantime.

I stuck with lead acid batteries for a decade. Now I wish I had dumped them much earlier. You can get by with them in the short run, but don't waste your time or beat up your bike needlessly with them once you have the budget for something better.

 

[renstyle]

Thanks for the info! I see your point about the lower wattage motor options, I wanted to get a 48V kit to make the Lunacycle 48V shark pack an easy drop-in replacement for the SLAs.

NOTE: I mentioned in my first post "pedal assist" but I had it all backwards. I do *not* intend to use a cadence-sensor assist setup. I just want to have a throttle to give me a little bump if and when I need it. Sorry, I should have known better.

What if I lower my performance requirements? Say I keep it under 15MPH, a nice leisurely pace?

My plan was to use a pack to commute one-way, swapping for a fresh pack for the return trip. I completely understand that a 25A controller will really tax these packs if I don't baby them. 7.2Ah for lead is on the low-end to begin with, why I was assuming full-time pedal assist while still using these SLA batteries.

My only real cost is the anderson powerpole connectors, the batteries are basically free, so I figured it was only my time building another pack as my loss.

Basically I'm torn between having to purchase either a 36V/500W kit now, roll with SLA batteries which will keep my packs in better shape, then having to get a 48V kit and battery when I am able to afford the 48V shark pack vs. buying the bigger 48V kit now and expecting my cheap SLA batteries to live short lives?

That's a $200.00 swing I'll have to think about. I suppose I'll have two full kits at the end of the day though...

 

[Ykick]

I used enough lead back in the day to offer some real world experience. HR (high rate) 7Ah SLA’s will only deliver 3-4Ah at 25A eBike C rates. And that’s only when new and fresh. Let ‘em sulfate even for a short period time and things will go downhill from there.

Go gentle and you might see 5 miles from a real 3-4Ah 48V (4 packs) arrangement? But mine (7Ah SLA) ran flat about 4 miles into my commute.

12Ah SLA would do somewhat better and deliver about 6-7Ah fresh. 9Ah is hardly worth the trouble stepping up from 7Ah.

To add, if you think you can get any performance from standby lighting SLA, forget it. Gotta be HR for wheelchairs, scooters, etc.

 

[The fingers]

Welcome to the forum! I'm still running on free culled used lead for the foreseeable future (500 watt kit). I do pedal along and only go around 10 mph to extend my range.
P.S. My mom's best friend lived in Ankeny; sadly after searching just now, I found out that she passed away a year ago at the age of 98. We used to drive through there on our many visits to all our relatives throughout Iowa.

 

[renstyle]

I'm starting to understand a bit better now.... The 36V kit with the 15A max controller is about all these low-end 7.2Ah SLAs can get away with for the 5-6 mile commute range I'm looking for.

Now you've got me thinking. If I doubled up a 36V pack (6-pack, 14.4Ah, 7-8Ah usable), is considering a heavy-duty pannier setup laughable? Would they all have to sit on the rear rack? Weight would be about 32.5lb for the lead...

 

[gogo]

Hey fellow Iowanian! Its possible to keep the amp draw low by judicious use of the throttle (slow accelerations), but it takes uncommon self-control to actually achieve.

 

[Chalo]

For what it's worth, most 36V controllers can be used at voltages up to 52V, provided you're not depending on the low voltage cutoff to protect your pack. If you get a 36V kit to use with your SLA batteries, you can fit it later with a 48V lithium pack that has its own low voltage cutoff built in.

 

[Rassy]

Renstyle, you mentioned hills up to 20% grade. I would be concerned that the motor you are looking at might not be up to that task. I would seriously consider a mid drive, such as a Bafang BBS02. Based on my experience with the 48V 500W BBS02 it would handle your weight on the hills along with a little pedal assist. Another advantage would be the lower draw on your current SLA batteries. Another important advantage is that you could easily pedal the bike without using any assist.

I'm aware that the cost of the BBS02 is double that of the kit you are looking at, but for anyone with real hills to get up you need something that is up to the task.

 

[Chalo]

I'd be extremely surprised if there are any 20% grades longer than a block anywhere in Iowa. If the only such grade you have to tackle is the first block up from the riverbank, you don't need a bike for that. Just walk it up and then off you go.

Don't spec your system for the worst 200 feet you could choose to ride. Spec it for the worst mile.

 

[LockH]

Hi Ankeny. You said "I just need something to help offset the wind", etc watt nobuddy here has addressed yet? Myself, I'm kinda big on aerodynamics these days. With an object of minimizing watts consumed per mile... etc. Lessee:
https://weatherspark.com/averages/30584/Ankeny-Iowa-United-States

Anyway, I'm currently riding recumbent and thinking velomobile-style. So a thin/light-weight shell. At least some sort of windscreen. The shell can get you stuff like cabin heating/cooling. And maybe no snow and rain.

And now back to usual stuff. Sorry `bout that SLA.

Cheers

EDIT: " a 5-mile commute". Much stop and go?

 

[wesnewell]

No, Get the 48V 1000W kit you listed in your first post. I've got ~15K miles on one just like it. I started with a 48V 500W kit and then bought the 1000W kit a week later. If you keep your speed down to 15mph, you can probably get 5 miles out of a 48V 7ah sla pack. i got 8 miles out of my 7.2ah old ups batteries at 12 mph. Pick your best batteries then just use 1 pack. Put on charger after each way of the commute. Will take no more than 2 hours to charge. That kit will also run well on a 12s rc lipo pack. a 10ah 12s lipo pack will get you 20 miles at 20 mph. You can buy that for under $100 on sale.

 

[dogman dan]

Agree with Wes, the kit you planned on will be fine. Just try not to ride it so fast, till you get better batteries. Keep it below about 20 mph.

You will need to carry 8 cells on the bike, 14 ah. Panniers, with 4 cells on each side may be the best way to carry them. Charge it again at work.

 

[LockH]

" Just try not to ride it so fast, till you get better batteries." Yah. Watt he said. Just be advised that "old" batteries rarely get "better". And that adding MORE weight to ANY vehicle is rarely a "good" thing. EVs are a great education in how NOT to use your batteries. To use them as little as possible. Def. impliment regenerative braking. And btw. For that skin/shell/wind screen/etc? Check out "thin film" (lighter weight, flexible) solar cells.

 

[gogo]

No, Get the 48V 1000W kit you listed in your first post. I've got ~15K miles on one just like it. I started with a 48V 500W kit and then bought the 1000W kit a week later.

Wes, have you ever investigated whether there are physical differences between the 500W & 1000W hubmotors? I've got two 9c clones from ebikeit that I've never used that look identical except for the 500W/1000W markings and have always wondered if they are actually the same. I ask here because I'm right up the road from Ren and have offered them to him.

 

[johninclaflin]

I'm riding a recumbent ez1-sc on a 9 mile one way commute with a hill on one end. The bike has a 250w 36v 206 rpm motor in a 20" rear wheel, overvolted to 48v from 4 (used) SLA 7.5 ah batteries. Controller comes limited to 11 amps, measurements with an inline watt meter. 4 ah is about what a trip draws with some wind, and 4 ah is about all the pack can deliver. I charge at both ends, using a Cyberpower 12v charger for each battery, and every 3rd day I need to give the rig a day off. I get the batteries and charger for free, and work has concerns about charging lithium un-attended, so until I can beat free or save up enough for a round trip capable lithium pack I can charge in a safe spot at home, its ride a lead sled. By the way, the motor is never hot to the touch at the end of the trip. I had the batteries behind the seat for awhile, but had trouble with popping rear spokes, so moved them to low between the wheels, and everything is better. So it sounds a lot like the ride and constraints you are thinking about.

 

[USAEBIKECO]

You should invest in some good solid tires and a solid bike frame if you add all that weight.

Weight is not an ebikes friend.

 

[wesnewell]

Wes, have you ever investigated whether there are physical differences between the 500W & 1000W hubmotors? I've got two 9c clones from ebikeit that I've never used that look identical except for the 500W/1000W markings and have always wondered if they are actually the same. I ask here because I'm right up the road from Ren and have offered them to him.

Yes, I have. They are different motors. At least the ones I got from yescomusa were. Although they both looked identical except for the part number on them, the 1000W motor weighed more, had more power and speed on the exact same controller and battery setup. The only other noticeable difference was the motor phase wires were larger on the 1000W motor. I didn't compare the insides, but they had to be different, otherwise there wouldn't be such a big performance difference. And there was a big difference in performance.

 

[renstyle]

As far as terrain goes, it is mostly flat, there is one hill next to my workplace that I will ride down in the AM, up in the PM. Being an Iowan, I may have underestimated how big a 20% truly is. That one hill is the only area that concerns me, and I'd be willing to walk the bike up if I truly had to, it's 3/4 mile top to bottom. The rest of the trip will all be on the level. (Gogo, what would you rate the grade on West 13th where it connects to Ontario St in Ames, under the UP bridge? My one hill is very similar to that one just longer)

There isn't much stop-and-go other than the normal you get traveling back streets residential, will have to cross a single 4-lane road (signal controlled). I fully expect to start the bike from a dead stop with leg power every time, using the motor only while in motion to minimize power consumption of accelerating.

It does get windy here at times, no windscreen is planned, just alot of head-down.

I'd love a Bafang mid drive (the HD) someday, once I have a decent lithium pack and a worthy bike to go with it. This one is strictly a basic work and grocery-getter for the time being.

I did have another question about charging times. I have a pair of these, which are 3-stage http://www.shorepowerinc.com/chargers/powerizer-ch-unla1230ul.html 12V chargers, with the clips replaced with anderson powerpole connectors. Since these are merely UPS batteries, it seems reasonable to expect only a 3-4Ah total useful current, even if I keep the speed down.

The bulk charge (stage 1) is done at 3.0A, up to 90%. A 4-pack of 7.2Ah should be fully charged in less than a normal workday. Two chargers could easily keep 2 4-packs at the ready...

Is two 4-packs stowed in panniers is even worth considering? I know there are weight considerations which could negate some advantage the increase in Ah would provide. A 14.4Ah (assuming 6-7Ah usable) would offer a little more headroom, but I'm not sure panniers could handle the weight (21.5lb on each side).

I can really see how a simple lithium pack + charger makes life easier, which is why I'm trying to low-ball this in order to save my nickels for a shark pack.

 

[LockH]

Just sayin'... In a search of ES Bible "Search found 135 matches: +vetter". Or give a Giggle Images search for "Vetter bike" maybe:
https://www.google.ca/search?newwin...2.5.0....0...1c.1.64.img..0.4.467.GDYACsYfbAQ

 

[renstyle]

Those enclosures look pretty sweet! They would rock on a recumbent. You're definitely in "Bike 2.0" category there, I like it!

 

[dogman dan]

Yes, 20 pounds in each pannier will be rough on em. I don't expect the rack, or the bags, to last very long packing that much lead. It may be worth it to do a home made steel rack, including trays to hold the batteries on each side. Using that lead is just a temporary thing for sure.

If you buy one of those prototype e bike kits, you can then run 36v or 48v. This might help, allowing you to carry a lighter 36v 14 ah lead pack.

 

[Shanefe]

Another thing to think about is running off a lower Voltage. At 24V you double the AH for the same weight. A lot of the motors will run off any of the common Voltages (24,36,48,+) so if you get a shark pack in the future, you will get a big speed / power boost.

I ride a Charger GT 24V bike 10 miles to work with a fairly steep hill at each end (think Seattle), and draw about 5-10 AH over 10 miles. I built a 20+ AH battery from Laptop cells, so I have been working on getting more power out of the system as I have a lot of spare power. Currently I am averaging a constant draw of 15-18Amps. Before optimizing the bike for power, the commute was about 6 AH to work and 4.4 AH on the way home (skipping one hill).

Lowering your Voltage will lower your speed, which is easier on batteries. Reading the Ad for the Hub Motor you posted, they want a minimum of 17AH of battery, not for distance, but because of the Amp Draw (i.e. 17A would be 1C on a 17AH battery, and 2.5C+ on the little 7AH that you have).

 

[dogman dan]

Yes, but you don't have to lower the voltage to ride slower. You just have to get control of that right hand. Or use a three speed switch if the kit has one. Best bet with lead is to ride under 20 mph, preferably under 15 mph. So you get there without ruining your lead in one trip. I pushed lead as hard as it would go when I got started, and wrecked my lead in 30 days. You'll need to do better than that, starting with old used lead.

But yeah, if he can get a kit that runs on 36v or 48v, run it on 36v so you can pack enough watt hours to get there, without the fourth battery( or 7th and 8th in this case)

 

[LockH]

"... wrecked my lead in 30 days." Hehe... Yah. Back in the daze, lead bats were cheap and easy to replace. Over and over. Discovered they made great door stops... but ran out of doors. (Collecting dead batts up to recycle.) These days, I figure on lowest cost per mile, before replacement. Stuff like how long before I need to worry/think about replacement. And finally have arrived at Comfy Style, as recumbent. Started out on stand up scoots. Worst aero on the planet. Any sit up bike only a little better. One hidden cost to going fast maybe, yer Funky-Style helmet: