Super capacitors to save battery life?

Batteries, Chargers, and Battery Management Systems.
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Re: Super capacitors to save battery life?

Post by Hillhater » Dec 08, 2017 12:18 am

You are really striking a poor compromise .
Double the weight
Much bigger volume
2/3 the capacity and range
All for a slight reduction in charge time ?
As was said early on, your 15ahr pack is capable of dealing with 500W of regen and a 1hr charge occasionally if that is needed.
You just have to make sure its well assembled with known quality cells.
Building new technology packs using unknown Chinese suppliers of unproven cells, sounds like a step into the unknown.
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Re: Super capacitors to save battery life?

Post by Sunder » Dec 08, 2017 12:42 am

You might have forgotten he also needed to lower the effective internal resistance of some aging cells.
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Re: Super capacitors to save battery life?

Post by lwik » Dec 08, 2017 1:41 am

Hillhater wrote:
Dec 08, 2017 12:18 am
You are really striking a poor compromise .
Double the weight
Much bigger volume
2/3 the capacity and range
All for a slight reduction in charge time ?
As was said early on, your 15ahr pack is capable of dealing with 500W of regen and a 1hr charge occasionally if that is needed.
You just have to make sure its well assembled with known quality cells.
Building new technology packs using unknown Chinese suppliers of unproven cells, sounds like a step into the unknown.
The one thing I didn't do when I built my touring bike was to go cheap. I realized cheap can leave me stranded in the middle of nowhere. Those 52V 15AH were $1K each and built by High Power Cycle in LA. They have good gear and a good reputation and are repairing the battery for my Christmas 320 mile tour from LA to LV. I have thousands of touring miles on it with really only battery problems to this point.

I am still reading about the LTO and I have to say if I can charge an LTO battery at 1000w/h or more VS. a Lipo at 360w/h with my Satiator, that is a much better deal. I can hold a lot more power during the day with 1/3rd less capacity because I might be able to charge them 3 times faster or more, that is what I am trying to find out. My rig has plenty of storage space as you can see. Instead of a 2 hour lunch break to charge 700 watts, I can take a 45 minute break with the same results. Then take a break at 3p at a gas station and plug in another 20 minutes for 300 more watts. That is a huge difference when touring by spending less time charging and more time riding. That would have allowed us to reach our campsites 1-2 hours earlier.

Not that this is the same situation but from when I started my bike build I met opposition left and right because I wanted to do things more unconventional. 16 more pounds to have 1 52v 22AH battery is not bad, heck I lost 18 pounds biking across America so that should make up the extra weight of LTO's :) I never even heard of LTO's until I started this thread looking for Super Capacitors to help save these $1K batteries.

Anyway, thank you for your help I appreciated all input.
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Re: Super capacitors to save battery life?

Post by Hillhater » Dec 08, 2017 3:08 am

A good quality beyyery shouldnt have weak cells/other problems after 300cycles....so i question the qyality of the packs you paid so much for. Ask what the problem was.
For the same weight as those 22ah LTOs you could carry 60 ah of 18650s which would have 3000Wh of capacity likely lasting you all day without any need to stop for recharge at all , or could take any amount of charge you could find.
Unless you find some lto packs with a proven record of reliability, you risk being a "early adopter"/ ginea pig, for a new technology.
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Re: Super capacitors to save battery life?

Post by flippy » Dec 08, 2017 4:27 am

with your "desired" weight target of around 30 pound you are basically on the same weight as my battery i have built for my 30mph scooter. if i were to re-build that battery with high capacity B panasonics instead of the PF cells i used then i could make a 4+kWh battery that would still be under 40 pounds total. if you use B cells and want to remain within spec you can charge that pack with 2,5kW of power. and if you use a intelligent BMS you dont need to bother with a expensive and large dedicated charger and you can just use a few high quality mean well supplies to bulk charge i am using such a setup built into my scooter and i am running that setup for more then 3 years now for my daily driving to work (80miles a day at 30mph, 50k total so far) without incident or issue. (at least none that i did not cause myself).

these are quick back-of-envelope calculations but in my opinion MUCH more reliable and practical on the road. being able to bulk charge at 2.5kW without going out of spec on the cells and being able to fill the huge battery in 2 hours should be a very nice bonus. so you can also deal with 2.5kW of regen and have 3.5kW of output at 1C discharge. that should get up up that hill pretty "brisk" :mrgreen:

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Re: Super capacitors to save battery life?

Post by lwik » Dec 09, 2017 4:58 pm

Hillhater wrote:
Dec 08, 2017 3:08 am
A good quality beyyery shouldnt have weak cells/other problems after 300cycles....so i question the qyality of the packs you paid so much for. Ask what the problem was.
For the same weight as those 22ah LTOs you could carry 60 ah of 18650s which would have 3000Wh of capacity likely lasting you all day without any need to stop for recharge at all , or could take any amount of charge you could find.
Unless you find some lto packs with a proven record of reliability, you risk being a "early adopter"/ ginea pig, for a new technology.
I talked to a buddy of mine who's an electronics engineer for the military on helping me build an LTO trial battery pack. I see the appeal for the same weight having 3000w using 18650 vs LTO's, but even when I have used up those 3000 watts I have to charge them. That means sitting in some fast food restaurant or gas station for hours, or when I get to a campsite you can normally charge at the only place they have power, the bathrooms, which means I sit outside the bathrooms for hours while they charge making sure no one steals them.

When you are bike touring it's a time game. Up at 6a, eat, pack up the campsite then 11-1 break for lunch at the closets town. If batteries are dead, sit there for 2+ hours while charging then back on the road. 4-5 arrive at a campsite, set up, make dinner, eat then 7p head to the bathrooms with a chair and charge till 9 and off to bed, repeat. If the sites don't have power and I need more power to reach the next town then it is a late start the next day because I break out the solar panels first thing in the morning while I pack and get a late start that day.

So out of a day of bike touring I can spend 3-5 hours just charging which causes less riding time. If I can build an LTO battery pack that can charge 1000w+ from a standard 110v safely, now I can get almost a full charge for a 1 hour lunch break. Then stop at gas station for a 20 min break, that's another 300 watts. Some places even have 220v and LTO batteries have a high C rate, so even faster charging and a much higher cycle rate then then batteries I am using now. It really sounds like what is limiting the charging of LTO's is the power coming out of the wall. If I could plug in to an EV fast charging port at a grocery store, maybe I could fully charge in 10 minutes as long as its safe. It really sounds like LTO's are just limited to what power source you have available.

Thanks!

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Re: Super capacitors to save battery life?

Post by Sunder » Dec 09, 2017 7:12 pm

Would you mind asking HPC what cells they use? The goalposts seem to have moved on this one. we've gone from using LTO to reduce voltage sag on ageing batteries and soaking up regen, to using it for rapid charging.

Its possible that if you always use you batteries in parallel, and get a bigger charger, you could charge fast. Most cells can cope with a 0.5C charge at 25*C, which means 7.5A on a single 15Ah pack, or 15A on both packs together. Good quality cells list 1C as their charge rate, so you could even go a 30A charger.

The key would be never to use that charger in very cold days, or first thing in the morning on moderately cold days. High rate charging and cold batteries shorten their life.
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Re: Super capacitors to save battery life?

Post by flippy » Dec 09, 2017 7:17 pm

there is absolutly no reason to use those LTO batteries. a 3kW pack made of regular 18650's can be charged with 2kW+. st such a large capacity the question is not "can you carge it fast enough", the question should be "can the outlet deliver the wattage without popping the breaker of the establishment you are visiting".

pulling 2kW from a regular 110 outlet is alsking for problems. most outlets are rated for 15A. so anything above 1.5kW is asking for problems. personally i would stay below 1.25kW in order to make sure the breaker does not pop anyway due to heat soak when you load it for 2 hours at full tilt. if you have a 220v outlet you can do 3kW easy but those are rare in america.

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Re: Super capacitors to save battery life?

Post by liveforphysics » Dec 09, 2017 8:09 pm

Maybe I'm not understanding correctly, but if you had a pair of 15Ah packs and you only connected one at to your bike when discharging, just connecting both of them in parallel to be a 30Ah pack would be the greatest return on useful cycle life and cost nothing.
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Re: Super capacitors to save battery life?

Post by flippy » Dec 11, 2017 6:20 am

For the weight balance it would logical to have 2 batteries on either side of the bike. But it would indeed be prudent to both batteries at the same time. It would extend the life of both packs and increase range.

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Re: Super capacitors to save battery life?

Post by billvon » Dec 11, 2017 1:28 pm

flippy wrote:
Dec 09, 2017 7:17 pm
pulling 2kW from a regular 110 outlet is alsking for problems. most outlets are rated for 15A. so anything above 1.5kW is asking for problems. personally i would stay below 1.25kW in order to make sure the breaker does not pop anyway due to heat soak when you load it for 2 hours at full tilt.
FYI the NEC says this about the issue:

"Unless otherwise marked, circuit breakers should not be loaded to exceed 80 percent of their current rating, where in normal operation the load will continue for 3 hours or more."

That's 1.44 kW. That's also why EVSE's limit current from an 5-15 outlet to 12 amps, even though many external outlets are capable of 20 amps.
if you have a 220v outlet you can do 3kW easy but those are rare in america.
Many people have dryer outlets rated for 220V. I carry a few adapters for my EV so I can use dryer outlets where available.
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Re: Super capacitors to save battery life?

Post by dustNbone » Dec 12, 2017 1:26 am

There's also public charging stations that use J1772 connectors (at least here they do) and deliver 32A at 240V. I'm considering building an 11Ah LTO battery and matching charging system that will allow me to charge very quickly when I'm around town.

I guess it's not like this everywhere but at least here (Vancouver) public charging stations are all over the city and surrounding metro area, I suspect at least some other cities are similar. 10 minute charge while I grab a coffee and another 25 miles range seems fairly practical to me.

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Re: Super capacitors to save battery life?

Post by amberwolf » Dec 12, 2017 2:49 am

FWIW, I'd skip the caps; not enough benefit for the extra volume and weight.

First, I'd parallel your existing packs so the load on each one is only half of what it would normally see, so it's voltage sag would be that much less as well. This should also get you more total range out of them, because the BMS won't trip as early due to load-sag.


If you need to replace the existing packs for any reason, I'd go with a simpler type of battery made of larger cells, which while it would probably be different in shape and possibly larger in some dimension than you'd like, less parallel cells makes for less potential connection issues. Generally the larger cells are also made for higher currents as well, though that's not universal.

There's a thread in the for-sale-used section where someone is selling EIG NMC packs, and based on my experience with them over the last few years, they're a good cell and interconnect method--though they may not be as power-dense as the packs you have now (so bigger for the same Wh).

I'm using a 14s2p (about 35+lbs for over 2.2kwh) on the SB Cruiser trike, which probably weighs (with me on it) similarly to you and your rig, and I regularly pull 120A from it for up to a few seconds during acceleration to 20MPH from a stop, around a dozen times each way on my daily work commute, then it drops down to a more reasonable 15-20A for cruising at 20MPH.

I don't use a BMS, I just use a Cycle Analyst (v2.3) to monitor Ah/Wh/Volts to be sure I don't run them down too far, and periodically check cell balance (which so far has not been a problem on the trike's 2p pack. On CrazyBike2's much older 1p pack, commonly hit with 80A+ peaks under the same conditions as the trike's 120A, I had one cell that developed higher resistance / greater voltage sag, but it is still working in the lighting pack (a 4s1p even now, and still gives full capacity at the lower currents that pack sees). All of the cells I have were used (in unknown conditions) when I got them, yet they're still holding up fine, and have stayed balanced. This doesnt' guarantee every pack made from these cells would, but so far it's been good enough for me. ;)

One of the reasons I like these cells, though, is that they are very easy to reconfigure, so if a cell does go bad, taking it out and replacing it (if you bring any spares) is easy. Or if the controller/etc can run on 13s, the cell can simply be removed and bolt the pack back togehter to run it at less voltage / wh / range.




The one issue might be balance of weight, since you have a bike, not a trike, and nowhere in the center of it to mount a pack (like I did on CrazyBIke2)--so you'd probably want to split the weight between the two sides. Depending on the capacity you need, you could either run a 14s2p pack on each side, if you need 4-5Kwh, or if you only need half that you could run a 7s2p pack on each side and series them with a fat cable. :)



They can be charged at 0.5C, so 20A for a 40Ah pack like mine, though I've charged it at 24A several times without apparent issue. I usually use a 12A charger that's built into the trike (meanwell HLG-600H-54A becuse it can be used on 220v or 110vac), but have also used the Cycle Satiator at 5A. At 24A it's about 2 hours to full charge. Closer to 2.5 hours at less than 20A (0.5C).

If really fast charging (<1 hour) is a goal, then the LTO is probably a better bet.

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Re: Super capacitors to save battery life?

Post by lwik » Dec 12, 2017 5:04 pm

amberwolf wrote:
Dec 12, 2017 2:49 am
FWIW, I'd skip the caps; not enough benefit for the extra volume and weight.

I don't use a BMS, I just use a Cycle Analyst (v2.3) to monitor Ah/Wh/Volts to be sure I don't run them down too far, and periodically check cell balance (which so far has not been a problem on the trike's 2p pack.

If really fast charging (<1 hour) is a goal, then the LTO is probably a better bet.
Thanks for the reply amberwolf. It's interesting that you don't use a BMS, I have seen a couple youtube videos about people not using them too. On my Cycle Analyst 3.0 its set to 42 volts as the cut off to keep keeps the batteries BMS from kicking in to shut the battery off. I was tempted in an LTO battery build to not use a BMS, but in the end I decided to include one. The batteries aren't just for the bike, they also power my camp at night charging my 5v devices, laptop and on hot nights runs a small fan in my tent. On a few occasions I wake up to the fan off since I tripped the low voltage cut off on the BMS. Letting that drain to far would be harm full to the the batteries so a BMS is needed.

One thing in the 'don't use a BMS' video the guy made a really good point, you simply don't know if your BMS has gone bad or not. This can do damage to the cells and you don't know it. It should balance but is it? So in searching for BMS's I discovered this one, so far http://chargery.com/BMS24.asp I would need 2 of them since I would have 42 cells in total but it works with LTO batteries and also has an external LCD you attach. Now I can see what the cells are doing and know if I have a problem if they are not charging or balancing correctly.

Mid February I'll have the time to start an LTO build.

Thanks!

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Re: Super capacitors to save battery life?

Post by lwik » Dec 12, 2017 5:29 pm

dustNbone wrote:
Dec 12, 2017 1:26 am
There's also public charging stations that use J1772 connectors (at least here they do) and deliver 32A at 240V. I'm considering building an 11Ah LTO battery and matching charging system that will allow me to charge very quickly when I'm around town.

I guess it's not like this everywhere but at least here (Vancouver) public charging stations are all over the city and surrounding metro area, I suspect at least some other cities are similar. 10 minute charge while I grab a coffee and another 25 miles range seems fairly practical to me.
That is what I was thinking too. Build in an EV charging connector to the battery pack and use public EV charging stations when applicable. I found adaptor kits on amazon that will do 110v to 220v using adaptors.

https://www.amazon.com/Electric-Vehicle ... v+charging

So if I end up at a McDonalds ( I use McD's a lot because they are everywhere), inside I can pull 110v and charge the LTO's at a safe 1000-1200 watts i'm guessing. If I am around a 220V source inside which happens from time to time, use that. Or if they have a EV fast charger outside, use that! But many times I pull into a restaurant and they have plugs outside that are just out of reach. Those cords from Amazon are around 25 feet, perfect to reach places and not have to remove the batteries from the bike to charge every time! So 1 connector to the battery from multiple power sources.

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Re: Super capacitors to save battery life?

Post by Sunder » Dec 12, 2017 5:52 pm

This isn't fully relevant, but it is a bit relevant, and I think a bit amusing.

My dad used a 11S (24v) LTO pack to charge a 12v battery, unregulated.

1. The 12V battery died, unsurprisingly.
2. The 24v battery "recharged" with some cells at 3.6v, and some cells at 1.8v, so heavy unbalanced (no BMS or balancer).

I had no idea whether the pack was still salvageable, so I was going to take it apart and charge/discharge each cell to 2.7v. These are cylindrical cells. Stacked on top of each other. Connectors are 3mm x 20mm copper bars held on by bolts.

I am not usually this careless, but it was a long day at work, and I was tired and not thinking... Now, imagine this. Like all good mechanics, you use a breaker bar to loosen every nut, then a standard ratchet to take the nut off. All nuts are loose. You completely remove one side of the bar, remove that cell, and the other side of the bar is now held on by a loose bolt... In other words, the remaining bolt is effectively a pivot... Guess what is directly below each row of batteries. Another row of batteries. Guess what happens when one of those copper bars falls and touches another copper bar that it's not supposed to?

1. A huge shower of sparks
2. The bar is blown back up by the force of the spark
3. Gravity acts on the bar again and it falls
4. It touches the bar below
5. Go to step 1. Repeatedly.
6. Eventually, bar fuses to other bar. I grab an insulated tool and smack it loose - after maybe 9-10 seconds of ~4 cells @ 300Amps (rated short circuit currents). More sparks ensue, until I can eventually stop contact. I now am "holding" a really hot copper bar with a pair of pliers... Use my other hand to put a cloth between the two so they can't contact again...

Those were the cells I tested first. Still hold full capacity, and internal resistance is still very low. These LTO cells are virtually indestructible.
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Re: Super capacitors to save battery life?

Post by Inwo » Dec 12, 2017 7:22 pm

Completely agree.
In a previous batch of lto, were 6p2s 65ah packs built for 10 minute charging in city bus.
The terminal were solid copper 1/2" thick and 3 1/2" wide.
One of the bars was burned half off on the end by the bolt holes.
I wasn't around when that happened. Bet there's a good story behind it! (or bad)
Can't find a picture.
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Re: Super capacitors to save battery life?

Post by lwik » Dec 13, 2017 4:30 pm

Sunder wrote:
Dec 12, 2017 5:52 pm
This isn't fully relevant, but it is a bit relevant, and I think a bit amusing.

My dad used a 11S (24v) LTO pack to charge a 12v battery, unregulated.

1. The 12V battery died, unsurprisingly.
2. The 24v battery "recharged" with some cells at 3.6v, and some cells at 1.8v, so heavy unbalanced (no BMS or balancer).

I had no idea whether the pack was still salvageable, so I was going to take it apart and charge/discharge each cell to 2.7v. These are cylindrical cells. Stacked on top of each other. Connectors are 3mm x 20mm copper bars held on by bolts.

I am not usually this careless, but it was a long day at work, and I was tired and not thinking... Now, imagine this. Like all good mechanics, you use a breaker bar to loosen every nut, then a standard ratchet to take the nut off. All nuts are loose. You completely remove one side of the bar, remove that cell, and the other side of the bar is now held on by a loose bolt... In other words, the remaining bolt is effectively a pivot... Guess what is directly below each row of batteries. Another row of batteries. Guess what happens when one of those copper bars falls and touches another copper bar that it's not supposed to?

1. A huge shower of sparks
2. The bar is blown back up by the force of the spark
3. Gravity acts on the bar again and it falls
4. It touches the bar below
5. Go to step 1. Repeatedly.
6. Eventually, bar fuses to other bar. I grab an insulated tool and smack it loose - after maybe 9-10 seconds of ~4 cells @ 300Amps (rated short circuit currents). More sparks ensue, until I can eventually stop contact. I now am "holding" a really hot copper bar with a pair of pliers... Use my other hand to put a cloth between the two so they can't contact again...

Those were the cells I tested first. Still hold full capacity, and internal resistance is still very low. These LTO cells are virtually indestructible.
That's crazy, but in the end it sounds like the LTO's still kept going. From thinking super capacitors were the answer to saving batteries to now considering LTO's because they are virtually indestructible sounds like another good reason to test them out. Thanks for sharing!

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Re: Super capacitors to save battery life?

Post by flippy » Dec 14, 2017 5:26 am

i would seriously recommend against using LTO cells in a ebike setup. they are WAY too big, heavy and overkill for this application.

i know for a fact that a dual pack setup (for weight distribution) made from 18650's can deliver a dozen times more power then you would ever need on a bike and can charge faster then a normal 110 outlet can supply and with a decent programmable BMS deliver the reliablity you need to do the trips you want. i have build dozens of packs now for various uses (everything from long haul ebike to uphill mounainbike hill climb and hardcore racing) and i never had a pack failliure that was not caused by either a major crash or gross user error.

TL;DR: a 18650 pack is your best option for reliabliity as long as the pack is designed and built to handle the abuse (electrically and shock). my guess is that your pack failliure is simply poor build quality.

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Re: Super capacitors to save battery life?

Post by Inwo » Dec 14, 2017 8:53 pm

lwik wrote:
Dec 12, 2017 5:04 pm
amberwolf wrote:
Dec 12, 2017 2:49 am
FWIW, I'd skip the caps; not enough benefit for the extra volume and weight.

I don't use a BMS, I just use a Cycle Analyst (v2.3) to monitor Ah/Wh/Volts to be sure I don't run them down too far, and periodically check cell balance (which so far has not been a problem on the trike's 2p pack.

If really fast charging (<1 hour) is a goal, then the LTO is probably a better bet.
Thanks for the reply amberwolf. It's interesting that you don't use a BMS, I have seen a couple youtube videos about people not using them too. On my Cycle Analyst 3.0 its set to 42 volts as the cut off to keep keeps the batteries BMS from kicking in to shut the battery off. I was tempted in an LTO battery build to not use a BMS, but in the end I decided to include one. The batteries aren't just for the bike, they also power my camp at night charging my 5v devices, laptop and on hot nights runs a small fan in my tent. On a few occasions I wake up to the fan off since I tripped the low voltage cut off on the BMS. Letting that drain to far would be harm full to the the batteries so a BMS is needed.

One thing in the 'don't use a BMS' video the guy made a really good point, you simply don't know if your BMS has gone bad or not. This can do damage to the cells and you don't know it. It should balance but is it? So in searching for BMS's I discovered this one, so far http://chargery.com/BMS24.asp I would need 2 of them since I would have 42 cells in total but it works with LTO batteries and also has an external LCD you attach. Now I can see what the cells are doing and know if I have a problem if they are not charging or balancing correctly.

Mid February I'll have the time to start an LTO build.

Thanks!
Any chance of using less cells?
I'm looking for an easy way to use multiple bms-24. Not easy to do safely, as one will be 50v above B-.
The chassis are floating (poorly). There have been issues with chassis grounding. I recommend complete isolation.

If you csn use <32s use a 32s bluetooth bms. Optional lcd.
HTB1QZX1SVXXXXchaXXXq6xXFXXXe.jpg
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This is the 24s model. I had the picture, as I'm planning a 30s or 40s project. And have 2 of them here.
One lcd and switch from bms-1 to bms2.
This won't work with chargery.

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Re: Super capacitors to save battery life?

Post by SamRich » Jan 17, 2018 12:17 pm

Hi Iwik,
Searched for this thread after you commented my LTO build.

It's a very interesting thread to me since not many do touring on ebikes and the trade offs are different than for a trail and commuting bike. I used to do a bunch of touring (before the kiddo) and I have thought of how I would maybe do it on an ebike. I had this idea to ride around lake Ontario in 3 days - 200 miles a day! I looked at tradeoffs between battery weight/ time charging during stops/average speed / and overall time on the saddle. I wish I could find that table to share it (I will if I find it) In the end I think 52V and 30Ah with a 15A charger seemed like a decent solution...Anyway I kinda gave up on the idea when I thought about being on the saddle for so many hours (and mind you I've done a few centuries).

Point is, not sure if LTO is the solution for your touring application. LiFe might be a better solution -some models have a few 1000 charge capacity and so it would be cost effective. In my comparison chart I omitted LiFe but with a back of the envelope calculation it should be nearly as cost effective as LTO but not nearly as heavy.

The reason I chose LTO is because I have a fixed /short commute that I do 250 days a year and also wanted high power. If I needed longer range I would go with either LiFe or 18650 as other have suggested. It sounds like you payed a lot for a somewhat average quality battery pack - so I understand the frustration, however a properly built pack with a quality BMS should give you a much longer battery life than what you experienced.

With a 20-40 lbs budget you could have up to 3kWh battery that you could charge at 1500W with a high current power supply. You are pretty much limited by the outlet which will provide maximum 1.5kWh per hour independent of chemistry. So you could charge every time you stop while still having some spare energy in case you need it whereas with LTO you'd likely already run out of energy for the same weight.

my two cents :)

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