Is there anything special or unusual about the SLA battery cells used in ebikes?

I'm curious if, when my battery pack begins to wear down, I really have to go off and buy a new battery pack from the same manufacturer - or for that matter, any ebike manufacturer at all.

I believe that my bike's '48v/20AH' power is most likely 4 seperate 12v/5AH cells (I haven't pulled the lid off the battery case yet). It seems to me, from looking at battery dealer websites, 12V/5AH SLA cells are a fairly common and not terribly expensive type of battery.

Could I just buy a handful of these and replace the cells myself, or is there something special about the type of cells used in ebikes that I'd need to look for beyond simply providing the correct voltage and amp hour rating?

Is it better that the cells in the battery all match (replace them all at once)? Or could I replace them one at a time and still expect things to work properly (say, buy a new 12V/5AH every 3-4 months and swap them in individually)?

I've been offered 12V/5AH batteries for 16.00$ by one dealer. If those would, in fact, work, then that's 64.00$ to rebuild my battery instead of the 250.00$ the ebike dealers charge. If that could be done, it would be a lot cheaper for me.

(I don't need to actully do this yet, my bike is new - just planning in advance)

Greg.

SLA batteries used in e-Bikes are deep cycle batteries as opposed to the starter type batteries used in cars or motorcycles.

Your batteries will likely be 4 x 12V 20Ah batteries, connected in series to give the 48Volts. 5Ah batteries won't get you very far. E-bike dealers are quoting you a price for 4 x 20Ah batteries.

As far as replacing goes, you can use any manufacturer as long as they physically fit in the bike or case. I would suggest they all be replaced at the same time when that day arrives.

There are many entries scattered throughout this meetup site about battery technology/characteristics/maintenance, etc.

Watt Fred Said

Is there anything special or unusual about the SLA battery cells used in ebikes?

The truth is, they aren't really designed for ebikes! But the two basic types, "starter" versus "deep cycle" are distinguished by the thickness and number of lead plates in each battery. Starter batts have thin plates and more of `em as this increases the exposed surface area of lead so higher amps can be extracted faster. Deep cycle batts have fewer, thicker plates...

Ebike use is still hard on the "standard" 12V sealed lead acid batts that are used in ebikes where the charge is commonly run down over just a couple of hours. The Amp-Hour ratings given for batts are actually based on the batts being discharged over TWENTY hours... In practical terms as the rate of discharge increases the actual amount of Amp-Hours the battery provides becomes less than their rated Ah.

I'm curious if, when my battery pack begins to wear down, I really have to go off and buy a new battery pack from the same manufacturer - or for that matter, any ebike manufacturer at all.

Like a chain, a string of batts connected in series (4x 12V = 48V) will have a "weakest link"... In a perfect world a pack of batteries are matched with the same batch codes and manufacturing dates. There are small differences between different batteries, even from the same manufacturer, and these differences magnify over time as the pack ages.

You will read that the new lithium flavoured packs demand a "battery management system" which monitors each cell in the pack to keep them all "balanced" within close tolerances to each other, and to protect each cell from too high or too low a voltage.

The same is true for the folks that drive large EVs (cars with 96V or 120V etc packs made up of 6V or 12V batts in series) and they commonly use battery monitoring devices for the same reasons.

The little ebikes with their smaller 48V etc lead packs do NOT (yet) come with battery monitors but they can and do suffer from packs where one battery in the string is not performing as well as the rest. For many reasons.

I believe that my bike's '48v/20AH' power is most likely 4 seperate 12v/5AH cells (I haven't pulled the lid off the battery case yet). It seems to me, from looking at battery dealer websites, 12V/5AH SLA cells are a fairly common and not terribly expensive type of battery.
Could I just buy a handful of these and replace the cells myself, or is there something special about the type of cells used in ebikes that I'd need to look for beyond simply providing the correct voltage and amp hour rating?

As Fred pointed out, your 48V 20Ah pack will likely be four 12V 20Ah batts connected in series.

Ya have to consider how much stored energy you need for the distances you need to travel. This is commonly measured in Wh/km... Another here (Eric P) recently reported that his Dad is seeing about 13Wh/km from his scoot (which seems exceptional to me.)

Your 48V 20Ah pack works out to 960Wh nominal, but ya can't run these SLA batts down below less than 20% of their rated capacity, and most ebike controllers watch the voltage level (drop) and cut power to the motor when batt capacity hits about 20% remaining.

So ya have to knock 20% off the rated capacity of your pack. 960Wh turns into 768Wh... And IF you see 15Wh/km as average consumption, then in theory the 768Wh pack will see you 51km on one charge.

Aging packs, cold ambient temperatures (cold batteries) tires not pumped to the max etc etc will all shorten the distance you will see on a charge...

So ya *might* get by with four 12V batts that are only 17Ah or 15Ah, but this WILL reduce your range, and if this means the pack is "working harder", regularly seeing deeper discharges than the 20Ah (as a percentage of nominal pack size) then the life of the pack will be reduced.

In a perfect world ya wouldn't ever discharge your pack below 50%!

Is it better that the cells in the battery all match (replace them all at once)? Or could I replace them one at a time and still expect things to work properly (say, buy a new 12V/5AH every 3-4 months and swap them in individually)?

See above. If you monitor the pack occasionally the simpliest way to do this is to buy a little 12V charger and "top up"/charge each battery separately once your big charger says "full"... The little 12V charger applied to each battery separately will tell you if you EVer have a runt in the litter, and in fact will help to extend the life of the runt.

I've been offered 12V/5AH batteries for 16.00$ by one dealer. If those would, in fact, work, then that's 64.00$ to rebuild my battery instead of the 250.00$ the ebike dealers charge. If that could be done, it would be a lot cheaper for me.

Ya well, now ya know... Ya can't use those 5Ah batts, unless you buy sixteen of them! Ya could hook `em up in "buddy pairs" (actually four in parallel to give 12V 20Ah) then series connect the four packs to get back to 48V... lots more wires, connections... not good.

For most ebikers, about the best/most important "upgrade" would be to a top notch charger, and a little 12V one too as a way to test/top up each batt in the pack from time to time. If ya do monitor your pack in this way then you should see them all wear out about the same time. Ya wouldn't be replace just one or two at a time.

If ya want yer batt pack to last, the way to do this is to NOT discharge it routinely below 50%. Pedal from starts before applying batt power, accelerate slowly (eg pedal bike speeds) and slower max speeds (wind resistance at higher speeds drives your Wh/km up, shortening range and again is a higher discharge on the batts so they'll wear out sooner.) Keep yer tire pressure up.

Believe it or not most of the "ebike" batteries out there are of dubious quality. The way to compare prices is Dollar per Wh capacity. But have a look first at watt real quality costs, as for some Trojans for example:
http://www.trojanbatt...

...or Odysseys:
http://www.odysseyfac...

Cheers
Lock

If it was me, after my batteries died, I'd go looking for better batteries, not just cheaper.

In an ebike, batteries are NOT the gas tank.

They're more analogous to the fuel injectors + fuel pump + carburetor + turbocharger + gas tank.

A cheap motor with really good batteries

outperforms

A really good motor with terrible quality batteries.

Look into having a lithium pack made, it won't be cheap upfront, but it will last you years, and every day you'll feel the difference.

If you get confused, ask for someone to do it here:

http://endless-sphere...

They'll give you a good price, and (if you choose the right offer) good work.

Gordon

Yeah, I'm not intending on buying now - just doing research and planning for when the cells in the current pack eventually die.

I'm certainly hoping that there might be slightly better batteries available (or even just slightly cheaper) to replace them with.

As far as going lithium, how easy is it to accomplish? What's required out of the controller? I'd certainly consider the option if it's as simple as just wiring up some lithium cells to the controller that's already in the bike - replacing the controller seems like it might be tricky, as it seems like identifying the actual part I'd need to get to work with the rest of the parts on this bike might be a pain (the bike is what Emmo calls the G550, which seems to be a Nicom bike).

I've been emailing back and forth with the folks at Total Battery, and they seem quite knowledgeable so far. Their initial suggestion of a battery to replace theones in the pack right now is actually a little more capacious than the cells it came with, if only marginally (21AH instead of 20AH), but that's not bad considering they're slightly cheaper than getting a new pack at the bike shop would cost. Hopefully the situation will be even better by the time I need them.

I haven't yet ordered anything from them, so can't really speak of that... I am considering ordering a small one to use in adding a stereo system to my bike, though, so if I do I'll report back on that.

The truth is, they aren't really designed for ebikes! But the two basic types, "starter" versus "deep cycle" are distinguished by the thickness and number of lead plates in each battery. Starter batts have thin plates and more of `em as this increases the exposed surface area of lead so higher amps can be extracted faster. Deep cycle batts have fewer, thicker plates...

That they weren't originally intended for ebikes is what I was hoping - glad to have further confirmation. The 'deep cycle' part I hadn't initially known about, so that's good to know.

Like a chain, a string of batts connected in series (4x 12V = 48V) will have a "weakest link"... In a perfect world a pack of batteries are matched with the same batch codes and manufacturing dates. There are small differences between different batteries, even from the same manufacturer, and these differences magnify over time as the pack ages.

If I were interested in investigating this and discovering which cell is the 'weak link', what's the proper way to test this?

The little ebikes with their smaller 48V etc lead packs do NOT (yet) come with battery monitors but they can and do suffer from packs where one battery in the string is not performing as well as the rest. For many reasons.

I've heard you discuss manual tuning in another set of posts here. Curious, have you heard about anyone adding a battery monitor? How involved is it? To me, it seems like that's the sort of feature that could potentially be integrated into the controller if the manufacturer chose to implement it, but it seems like adding one yourself should also be theoretically doable.

As Fred pointed out, your 48V 20Ah pack will likely be four 12V 20Ah batts connected in series.

Yeah, stand corrected on this part. Basic electrical knowledge fail.

Your 48V 20Ah pack works out to 960Wh nominal, but ya can't run these SLA batts down below less than 20% of their rated capacity, and most ebike controllers watch the voltage level (drop) and cut power to the motor when batt capacity hits about 20% remaining.

One thing I'd like to work out is where that position in the charge level falls in terms of the voltage meter on the bike's instrument panel. Is the point where the bar changes from white to red 20%? Or is the end of the red section what should worry me? So far I've been dreading going into the red section of the meter at all in the name of caution.

So ya *might* get by with four 12V batts that are only 17Ah or 15Ah, but this WILL reduce your range, and if this means the pack is "working harder", regularly seeing deeper discharges than the 20Ah (as a percentage of nominal pack size) then the life of the pack will be reduced.

Yeah, I'd definitely want to meet if not exceed the Ah rating of the original pack.

Ya well, now ya know... Ya can't use those 5Ah batts, unless you buy sixteen of them!

Yep, see the previous failure of basic electrical knowledge on my part.

For most ebikers, about the best/most important "upgrade" would be to a top notch charger, and a little 12V one too as a way to test/top up each batt in the pack from time to time.

Yeah, I think I'm convinced on getting a small 12V charger. I think I'm going to need one for the stereo installation I plan on doing anyhow.

If ya want yer batt pack to last, the way to do this is to NOT discharge it routinely below 50%.

Sadly, I'll probably have to. Getting downtown from my home seems to need perhaps a third of the charge on the still new pack*, and I usually won't have time for a full charge while I'm down there before heading up. I'm alright with having to replace the cells every now and then - it's still cheaper than gas, the TTC, or any of my other alternatives.

(*: At least, the voltage meter is dropping to about a third of the way in by the time I arrive downtown... whether that corresponds directly to the portion of the charge remaining I'm still uncertain)

I've been following most of those driving tips so far (other than the pedaling part, but that's because I need to put the chain back on properly), as well as mostly coasting when going downhill. I've also been doing a fair bit of 'pulse and glide' driving - though trying for smooth pulses, of course, as I've heard being jerky on the throttle can overwork the controller and risk burning it out.

Believe it or not most of the "ebike" batteries out there are of dubious quality.

Oh, I'm willing to believe it.

The way to compare prices is Dollar per Wh capacity. But have a look first at watt real quality costs, as for some Trojans for example:
http://www.trojanbatt...
...or Odysseys:
http://www.odysseyfac...

The guys at Total Battery recommended these, when I asked for a 12V20AH SLA deep cycle battery: http://power-sonic.co.... Have you heard of them? What do you think of the specs? I haven't yet measured them to ensure they'd physically fit, this is just the first thing they suggested that fit the electrical requirements.

If I were interested in investigating this and discovering which cell is the 'weak link', what's the proper way to test this?

The only real way to test is by "load testing" where ya start discharging a batt on a standard load (eg 75W light bulb) then measure voltages over timed intervals...

I've heard you discuss manual tuning in another set of posts here. Curious, have you heard about anyone adding a battery monitor? How involved is it? To me, it seems like that's the sort of feature that could potentially be integrated into the controller if the manufacturer chose to implement it, but it seems like adding one yourself should also be theoretically doable.

PowerCheq for example:
http://www.evsource.c...

...and ya need N-1 for your 4 batt pack, so three of those, about $200 total. Makes more sense when the investment in batts is much larger as in a converted car or truck. These don't just "monitor" but shunt bits of current around to equalize the pack "on the fly"...

Is the point where the bar changes from white to red 20%? Or is the end of the red section what should worry me? So far I've been dreading going into the red section of the meter at all in the name of caution.

Not sure *dread* is the right word, but how accurate those "gas guages" are can vary. Even using voltage alone as the measure is an imprecise way to do it. If ya really want to "nail it" ya would invest in a separate watt meter like the Cycle Analyst:
http://www.ebikes.ca/...

or a Watts-Up, seen here:
http://www.cyclone-us...

The CA counts UP (accurately) as you consume Whs... Knowing how many Whs ya have to start with lets you keep an eye on things that way.

Yeah, I think I'm convinced on getting a small 12V charger. I think I'm going to need one for the stereo installation I plan on doing anyhow.

Actually, this *sounds* like yer talking about a DC to DC converter... Ya plug it into eg 48V and 12V pops out the other side? Not quite the same thing as a "12V" charger as chargers need to output about 14.5V to max charge a 12V battery... Plus chargers have (hopefully) the logic to be monitoring things and to cut back and cut off charging as appropriate...

The thing about the load testers is they'll point out a problem but not fix anything. If ya use your regular charger to recharge the pack, then try charging each batt separately w/a little 12V charger and one batt takes more charge (longer time than the others) this shows one batt is weak BUT also tops that batt up to bring it back in balance with the other batts.

If ya want yer batt pack to last, the way to do this is to NOT discharge it routinely below 50%.

Sadly, I'll probably have to. Getting downtown from my home seems to need perhaps a third of the charge on the still new pack*, and I usually won't have time for a full charge while I'm down there before heading up. I'm alright with having to replace the cells every now and then - it's still cheaper than gas, the TTC, or any of my other alternatives.

In my experience with North/South commutes in Toronto I get about half the range per charge headed north than headed south, cause of the topography. Google Earth etc can tell you the diff altitudes, but I know the distance from the tarmac at the Island Airport to the tarmac at Downsview airport is 401 feet - straight up/down, and most of this happens south of Lawrence...

If yer worried about this, this is an example where ya might add a second smaller pack eg 4x 12V x 5Ah. Series them up as 48V 5Ah then parallel connect to your main pack. So ya end up with 48V 25Ah. Not only will this extend possible max range, it'll also mean that the pack as a whole sees shallower discharges on average, so this will increase the number of cycles (charge plus discharge) you get out of the pack as well. If you have the room to cram more lead in there somewhere...

Somebuddy else here recently pointed out someone is selling 25A batts that are the same physical size as the 20A sold by others. If this is true then is would be the simpliest "drop in replacement" to increase Ah.

The guys at Total Battery recommended these, when I asked for a 12V20AH SLA deep cycle battery: http://power-sonic.co.... Have you heard of them? What do you think of the specs? I haven't yet measured them to ensure they'd physically fit, this is just the first thing they suggested that fit the electrical requirements.

Ya, I've been sold Power-Sonics before. I like to use `em for reference simply `cause they do publish specs for their batts. I hope as North American/Euro folks they have that western ethic about quality control and customer service...

But I've always just trashed my batt packs over the years, rarely getting more than a year out of them, so didn't worry too much about which were "better"...

So do as I say, not as I do

loCk

...and ya need N-1 for your 4 batt pack, so three of those, about $200 total. Makes more sense when the investment in batts is much larger as in a converted car or truck.

Hmm, yeah. Definitely seems to be a bit overkill when a whole new pack would cost only marginally more than the balancing circuitry.

Is the point where the bar changes from white to red 20%? Or is the end of the red section what should worry me? So far I've been dreading going into the red section of the meter at all in the name of caution.

If ya really want to "nail it" ya would invest in a separate watt meter like... (etc).

Ooh, handy. I certainly may have to pick one of those up.

Actually, this *sounds* like yer talking about a DC to DC converter... Ya plug it into eg 48V and 12V pops out the other side?

Nah, I was intending on keeping the stereo's electronics completely seperate from the motor's. That way, if I drive somewhere, park, and turn on the stereo, I know that I'm still going to have the same amount of juice left for the motor as I did when I parked. I'd rather have the stereo stop and lose my music than have the motor run out of juice.

If I did something like you mentioned further on in your post, and added a couple of cells to the pack to increase it's AH level, then I'd certainly consider linking the two systems, since it'd make charging simpler. But I'm not really sure if I want to always be carrying the weight of a couple of extra cells, so for now I may forego that and keep the electronics separate.

Maybe I'll set it up using separate power for now and then, when my current cells start to die, replace them with larger capacity ones (don't happen to have a link to those 25A ones, do ya?) and rewire things to add a DC-DC and let them share the enlarged main pack.

As far as chargers, I've been glancing at these two over at Canadian Tire. Any reason to prefer one over the other for purposes of pack balancing? If I'm reading the specs right, the second one might be a little quicker at it.

http://www.canadianti...

http://www.canadianti...

Thanks for all the advice so far, you're a wealth of information.

Seems like 12V24Ah cells are a lot more common than 12V25ah cells, at least upon a quick Googling. Maybe those are the way to go as far as a more powerful replacement cell, if ones can be found with suitable sizing.

Edit: 28Ah also seems widely available, though I'm guessing sizing those would be even trickier.

There's a nice battery chart here:

http://www.mobilityun...

-Vic