Henry111's free tech support thread

[Henry111]

Assume a 36V/12Ah SLA battery compared with a 36V/10Ah Lithium:
Because the Lithium is a lower Ah of only 10 would it deliver less range than the SLA of 12?
If so, how much less--all else in the ebike system being equal?


Moderator edit: merged your duplicate threads, cuz, like, not supposed to create multiple threads for the same thing!)

 

[wesnewell]

Lithium will get about twice the range as sla per ah, but with lithium you need to make sure you get a high enough C rate to match your controller. So if you have a 30A controller you'll need a 3C 10ah lithium pack to put out 30A. C rate times AH= max amp output.

 

[eva-michael]

There's lots of threads discussing this sort of thing, but probably the SLA would get half (or less) the range of the lithium, assuming you use both to 100% DOD, which will kill the SLA pretty quick (a few dozen cycles, most likely for the cheap SLA types).

Realistically, you can only use about half the Wh in SLA and expect any kind of lengthy life, so really you'll only get about a quarter the range, and even then the Li pack will probably still last more cycles.

Very good answer!
No mater which type of battery we are using, we should know how to maintain it and keep them a a good cycle life. It's not expensive to buy a few ah biger battery. But it will be more expensive to replace one without good use habits.
For Li type, we use no more than 80% in more of time.

 

[dogman dan]

Double the range, or more. Much of it because lead is nearly unusable below 50% depth of discharge. So think of a 12 ah lead as really about 7 ah.

 

[SamTexas]

Assume a 36V/12Ah SLA battery compared with a 36V/10Ah Lithium:
Because the Lithium is a lower Ah of only 10 would it deliver less range than the SLA of 12?
If so, how much less--all else in the ebike system being equal?

A 36V/12Ah SLA has roughly the same USABLE energy as a 36V/6Ah Lithium battery when completely discharged in 1 hour (typical for ebikes).

So 10Ah/6Ah = 1.66. All else being equal, your range will increase by 66%.

 

[TexasTuff]

I'm saving for a lithium battery but in the meantime I'm stuck with a couple of 12 volt 20 ah sla batteries in series. When I leave on a ride it is about 26 volts. I've been running it down to about 21/22 volts. Is this too much? If you can use 80% of the lithium battery what is safe for the sla batteries?

 

[wesnewell]

10.5V per 12V battery is safe as long as you don't let it sit there. You need to charge SLA as soon as possible after use the keep the sulfur crystals from hardening on the plates.

 

[dogman dan]

What is safe? Those that run lead for years tend to swear by 50% depth of discharge. Likely that is closer to 12v than 10.5. I don't know exactly when your pack would be 50% discharged. Depends on how many real world Ah you get, compared to spec Ah.

It depends on how long you need to wait for that lithium. If it's a year, start stopping even sooner would be my advice.

The low tech thing to do, would be to consider 21 volts to be 100%, then start riding half that distance by the bikes odometer. So if you got 7 miles, start riding no more than about 4 miles.

 

[Drunkskunk]

I'm saving for a lithium battery but in the meantime I'm stuck with a couple of 12 volt 20 ah sla batteries in series. When I leave on a ride it is about 26 volts. I've been running it down to about 21/22 volts. Is this too much? If you can use 80% of the lithium battery what is safe for the sla batteries?

In reality, you can use 100% of Lithium, but for the best life, you should try to use only 80%. Consider the last 20% a reserve tank. It won't hurt to use it every now and then, but the battery will last much longer if it rarely happens.

You can also use 100% of SLA, but due to Peukert's law, the capacity of the battery will be reduced by 40 to 60% under loads experianced with an Ebike, so it's 100% will actualy be 40% to 60% of what it was rated at. And the same rules apply about use. You realy only want to use about 80% of what the battery can actualy give you for the best longevity of the battery, So you should only use about 80% of that 40% to 60% of the original capacity.

So a 24V 20AH SLA can give you, lets call it 50% after Peukert effect. So it acts like a 10 amp battery. You can use all of that, but should only use about 8 amps normaly for the best life. It will weigh roughly 25lbs

A Lithium ~24v 10AH battery will give you the same power, but weigh roughly 4 to 6lbs.

 

[wesnewell]

10.5V per 12V battery is safe as long as you don't let it sit there. You need to charge SLA as soon as possible after use the keep the sulfur crystals from hardening on the plates.

Need to clarify this. An LVC of 10.5V per cell is safe. I'm not sure what the resting voltage will be, but it will be more than 10.5V I'm sure.

 

[galvatron1]

I was about to buy Panasonic 18650 LiNiCoMnO2 chemistry, & pay a hefty price, b/c I was told they can do 1000+ recharges & are the best on the market from a China vendor. (36V 14.5AH 2.5KG USD 335.00 + about $150 to ship, using panasonic cell 3.6v 2900mah (single cell). She also told me that LiFePO4 is last years technology, & that this is the latest tech & are better than LiFePO4. So you're saying there's a safer, better alternative on the horizon? Please, tell me more, spinningmagnets. & when will these batteries become more affordable through mass production in the near future, maybe Summer 2014?

 

[melodious]

I'm about to embark on a 2nd ebike build. I will purchase all the parts and install them. The last purchase I will make will be the battery. I will take my time and patiently wait for the new 18650-20R cells to arrive to EM3EV.com (cellman's website). They have a better C-rate for more performance oriented builds and still keeps the safe chemistry allowing virtually anyone to use them with no risk of fire hazard.

TBH, from my readings on the next wave of NCM coming to the creative pack builders such as cellman, the real solution is getting the most kWh into your frame. These will be custom packs, for frames such as the stealth, phasor, greyborg, etc. But, If you have a "run of the mill" bike you want to convert, then you can simply click "buy" on a plug & play triangle pack.

The larger A123 pouch cells are another source, but the size of them can be a limiting factor especially if fitting them in a regular bike.

 

[Henry111]

Other than the difference in weight and longer life (more cycles) can someone please answer the following five (5) SPECIFIC questions regardng the difference between a Lithium battery and an SLA battery? Percentages are OK.
Please assume that both are 36V/12Ah. The Lithium is a LiFePO4. The SLAs are Gruber Power.
One: How much more range, if any, would one get from a Lithium compared to the SLA?
Two: How much more speed, if any, would one get from a Lithium compared to the SLA?
Three: How much more climbing power would one get from a Lithium compared to the SLA?
Four: How much longer does it take to charge a Lithium compared the SLA?
Five: As one rides and the charge on an SLA battery runs down one loses power. I have heard that a Lithium retains its full power (speed and climbing ability) right up until the Lithium charge is practically depleated. IS THIS TRUE?

 

[dogman dan]

1 Double for sure, and likely more. You won't get 12 ah out of lead at a 15 amps rate. You'd get at least 11 ah from the lithium.

2 About the same, but with lifepo4, faster in the middle of the ride, Limn has a more linear dropoff, but either kind of lithium don't drop voltage as fast as lead will.

3 About the same, but similar to above. Less voltage drop as you ride, especially with lifepo4.

4 About double since you will be putting back the full 12 ah, if you use a slow charger for both. You can't use all 12 ah with a lead pack, or rather you can only if you plan on throwing it away in a few weeks. lead in that size can stand no more than 2 amps. No problem to use a 5 amps charger with lithium. Get the 5 amp charger.

5 YES, for lifepo4. A typical 48v lifepo4 pack will start at 56v, and many miles later still be at 52v. A lead pack will start at less volts, drop to 50v in a few blocks, and get worse and worse from there. Limn will do a more steady drop in voltage as it discharges, but still has a large time when the voltage remains higher than lead.

 

[Henry111]

1 Double for sure, and likely more. You won't get 12 ah out of lead at a 15 amps rate. You'd get at least 11 ah from the lithium.

2 About the same, but with lifepo4, faster in the middle of the ride, Limn has a more linear dropoff, but either kind of lithium don't drop voltage as fast as lead will.

3 About the same, but similar to above. Less voltage drop as you ride, especially with lifepo4.

4 About double since you will be putting back the full 12 ah, if you use a slow charger for both. You can't use all 12 ah with a lead pack, or rather you can only if you plan on throwing it away in a few weeks. lead in that size can stand no more than 2 amps. No problem to use a 5 amps charger with lithium. Get the 5 amp charger.

5 YES, for lifepo4. A typical 48v lifepo4 pack will start at 56v, and many miles later still be at 52v. A lead pack will start at less volts, drop to 50v in a few blocks, and get worse and worse from there. Limn will do a more steady drop in voltage as it discharges, but still has a large time when the voltage remains higher than lead.

Thank you dogman. I always appreciate your concise yet clear answers:
But:
Just to make sure I have it all clear in my head please confirm or correct:
With Lithium, my range will double, possibly more!
With Lithium, I will have about the same speed, but will enjoy it for a longer period of time during any given ride.
With Lithium, I will have about the same hill climbing ability, but will have it for a longer period of time during any given ride.
With Lithium, I can charge it faster than an SLA providing I use a 5 amp charger.

 

[Ypedal]

Also factor in how much lighter and less bulky your bike will be, that also translates into how much easier it is to pedal it meaningfully ..

 

[ColinB]

I want to point out the differences here. Lipo comes out on top because typically Lipo packs are able to deliver the power needed for electric bikes. Most? SLA batteries can't. You'll have to check YOUR Lipo pack to see if it can deliver what your motor will demand. If you have a 1000 watt motor, you need a pack that is happy delivering 1000 watts. (And not just 1000 watts peak, for a limited time.)

Colin

 

[RoadWrinkle]

The simple answer is if you have a budget for lithium, there is no good reason to use SLA. Would you prefer a horse cart over a model T?

 

[Ykick]

Good stuff here and with regard to charge rates SLA requires a fairly slow rate to survive more than a handful of cycles. OTOH many Lithium based cells can accept high rate charge and in some hearty cases nearly as many amps IN as can be pulled OUT.

In almost all cases Lithium there's opportunity for far less/shorter recharge time compared to SLA over same distance - W/mi parameters.

Weight and size is the real allure though and everythng stacked up, SLA's hard to justify in just that regard. Nevermind the advantages of charge/discharge.

 

[el_walto]

SLA is actually expensive because you will get less than 100 recharge cycles out of it while using it on an ebike. You likely can get 5x charge cycles out of lipo.

Four Max Charge rate of a 12Ah SLA is 4amps. Many would charge a 12Ah lipo at 12amps(3x faster than sla). Hobbyking nanotech lipo 12Ah would be rated at 60amps charge rate(15x faster than sla)

 

[Henry111]

I'm looking for one of those rear racks that has two sections (upper and lower). My thought is to mount the battery in the lower section and I could then mount the speed controller on top. Thus, I would not have to find a way to mount the speed on the bike frame. Any leads or links will be sincerely appreciated. The battery in question is a 36V/12Ah carton style that comes in an aluminum case.

 

[wineboyrider]

bmsbattery.com

http://www.bmsbattery.com/accessory/485-rack-for-our-03-and-05-battery-case-.html

 

[Henry111]

I have a single-speed bike and want to mount a motor on the rear.
It seems that most rear motor kits come with several cogs in the cassette, but I want to keep the bike as a single speed.
Will I have a problem with that?
If so, can I fix it and how?
Your help please.

 

[dehoov]

Well - I'm no ebike expert but I know a few things about bikes - as far as I know as long as your crank and chain are compatible with the freewheel on the motor then it makes no difference about whether or not you have extra gears there - you just won't use them - ie the chain will stay on the smallest cog (harder to pedal) all the time. But then anytime you can upgrade by adding shifters and compatible rear derailleur. Others on the forum can advise but I'm pretty sure you can get a rear motor wheel with just the one cog.

 

[wesnewell]

Most come with a freewheel, not a cassette, which goes on a freehub. You can buy single gear freewheels, or you could just lock a rear derailleur to a single gear. The dropout width may be a problem with aluminum dropouts, but with steel ones, there wouldn't be a problem that one couldn't handle.