Building a large capacity battery for bicycle trailer

[john61ct]

Yes but it is more like cargo trailer than a camper!
I am intending to carry additional weight on the trailer. Recommended max weight for the trailer is 25kg.

That limit is not compatible with your dreams of high Ah capacity no matter what chemistry.

If you get more realistic about the required payload weight, then it is worth looking at the pro's and cons of your choices, and

the true density differences of li-ion vs LFP given specific cell choices.

Flippy is definitely overstating the case for li-ion, but when every ounce counts that is what most people choose.

 

[TrotterBob]

660 grams each x 14 = 9240 grams or 20.37 lbs. So yeah, a bit on the heavy side.

 

[azad]

Your current horizon covers 2 hrs in moped mode at 40 km/h. You cannot scale that up and assume, that with more energy on board you could do that all day long. If you have no experience in endurance sports, you will encounter mental, physical and material limits soon. F.e. he cheap trailer you suggest, is not suited for 40 km/h all day, with 50 kg of batteries on board, it will not even survive a single day.

Try to start with something realistic you can do right now without buying additional stuff. You cannot buy physical and mental physical fitness, you have to aquire it by training.
Try to make 200 km in two 100 km stages, charging your 13s8p battery at halftime.
Then you have an idea, how long you can sit on the bike, and if you ENJOY it.

13s8p alone can not give 100km specially when attached with a 15kg trailer. I was talking about 2 batteries that I use when I take longer trips. The extra battery is EV battery (li-ion) but each cell is 20Ah. I have tested only ~100 km only without any additional load such as a trailer.

Charging battery on the side of the road takes a lot of time. With current charger (4A) it takes about 6 hours to charge one battery and 5 the other. If I move to a 10A charger then one battery would charge in 2h and other 2.5 although I am not sure if I can charge cheap china 18650 battery with such high charge rate. In any case travelling for 1h and then waiting on the side of the road for charging atleast twice as long as the distance travelled seems a bit too difficult.

 

[gobi]

Your current horizon covers 2 hrs in moped mode at 40 km/h. You cannot scale that up and assume, that with more energy on board you could do that all day long. If you have no experience in endurance sports, you will encounter mental, physical and material limits soon. F.e. he cheap trailer you suggest, is not suited for 40 km/h all day, with 50 kg of batteries on board, it will not even survive a single day.

Try to start with something realistic you can do right now without buying additional stuff. You cannot buy physical and mental physical fitness, you have to aquire it by training.
Try to make 200 km in two 100 km stages, charging your 13s8p battery at halftime.
Then you have an idea, how long you can sit on the bike, and if you ENJOY it.

13s8p alone can not give 100km specially when attached with a 15kg trailer. I was talking about 2 batteries that I use when I take longer trips. The extra battery is EV battery (li-ion) but each cell is 20Ah. I have tested only ~100 km only without any additional load such as a trailer.

Charging battery on the side of the road takes a lot of time. With current charger (4A) it takes about 6 hours to charge one battery and 5 the other. If I move to a 10A charger then one battery would charge in 2h and other 2.5 although I am not sure if I can charge cheap china 18650 battery with such high charge rate. In any case travelling for 1h and then waiting on the side of the road for charging atleast twice as long as the distance travelled seems a bit too difficult.

op. pls watch this
https://www.youtube.com/watch?v=Mfpa8KYLqnw

for me the Pros are:
1. I can charge at 25a rate max
2. no welds

Connecting 2 batteries in Parallel:
1. Put in a switch to select battery
2. Or MATCH battery voltage


Charger:

Look at the size of a mean well hrpg 500-48

 

[Felixaustria]

13s8p alone can not give 100km specially when attached with a 15kg trailer.

Many users here (including myself) could ride not just 100 km, but 200 km with your 13s8p, not at 40 km/h, but at 25 km/h, and with some pedalling. This is feasable with a normal ebike and some training.

Let us return to your goal:
You want to make 300-400 km per day at 40 km/h without pedaling with an electric bicycle.
Aside from other prerequirements for 400 km/day on a bicycle we can regard your question as a technical issue and try to solve it.

Energy:
You would need about 10 - 15 kWhrs of energy.
If we assume a specific energy of 200Wh/kg for Lithium Ion cells, we would need about 60 kg of battery cells.
Let us add 20 kg for a rigid case, and calculate about 80 kg for the battery.

Bicycle:
A cargo bike can carry that additional weight. A tandem bike could do it as well. Neither of them is build for continous 40 km/h. Some parts have to be upgraded, you need spare parts and the skill to repair your bike on the road

Charging:
When you arrive at your destination with a single charge, you still have to charge your batteries for the next day. Let us assume, that you have 10 hrs time. Then you need about 1,5 kW of charging power. Divide your monster battery into 5 partitions and you can use 5 pcs. of a 300W charger like Meanwell HLG320. the 5 sub packs should be indentic if you want convenience

Other prerequirements:
the fitness to sit on a bike for +10 hrs a day, good navigation skills, bicycle mechanic skills, a budget of 10k USD for reliable quality of all components

 

[fatty]

Charging battery on the side of the road takes a lot of time. With current charger (4A) it takes about 6 hours to charge one battery and 5 the other. If I move to a 10A charger then one battery would charge in 2h and other 2.5 although I am not sure if I can charge cheap china 18650 battery with such high charge rate. In any case travelling for 1h and then waiting on the side of the road for charging atleast twice as long as the distance travelled seems a bit too difficult.

It doesn't have to. Schuko outlets give 230V * 16A = 3680W.

You just have to design your system to meet your goal.

 

[fatty]

Many users here (including myself) could ride not just 100 km, but 200 km with your 13s8p, not at 40 km/h, but at 25 km/h, and with some pedalling. This is feasable with a normal ebike and some training.

Let us return to your goal:
You want to make 300-400 km per day at 40 km/h without pedaling with an electric bicycle.
Aside from other prerequirements for 400 km/day on a bicycle we can regard your question as a technical issue and try to solve it.

Energy:
You would need about 10 - 15 kWhrs of energy.
If we assume a specific energy of 200Wh/kg for Lithium Ion cells, we would need about 60 kg of battery cells.
Let us add 20 kg for a rigid case, and calculate about 80 kg for the battery.

Bicycle:
A cargo bike can carry that additional weight. A tandem bike could do it as well. Neither of them is build for continous 40 km/h. Some parts have to be upgraded, you need spare parts and the skill to repair your bike on the road

Charging:
When you arrive at your destination with a single charge, you still have to charge your batteries for the next day. Let us assume, that you have 10 hrs time. Then you need about 1,5 kW of charging power. Divide your monster battery into 5 partitions and you can use 5 pcs. of a 300W charger like Meanwell HLG320. the 5 sub packs should be indentic if you want convenience

Other prerequirements:
the fitness to sit on a bike for +10 hrs a day, good navigation skills, bicycle mechanic skills, a budget of 10k USD for reliable quality of all components

Great analysis -- this is the type of detail that would have been helpful on the first page.

However, to further quantify, 40km/h on a draggy e-moto will require 20Wh/km, and you want to travel 400km.
20Wh/km * 400km = 8000Wh required

LG Chem N2.1 automotive LiPo cells are 60Ah, 198Wh, and weigh 900g
8000Wh / 198Wh/cell = 40cells, arrange as 2p20s to maximize controller power density and minimize resistive loss
40cells * 900g/cell = 36kg bare cells

I would target packaging at 10% of battery weight, not 1/3rd
36kg * 110% = 40kg complete pack


However, breaking up into sub-packs to charge is sort of the definition of inconvenient -- and not necessary.
Elcon HK-J-H99-40 3.3kW charges at 40A for 650EUR
60Ah in 2p = 120Ah / 40A = full recharge in 3h

 

[Chalo]

However, to further quantify, 40km/h on a draggy e-moto will require 20Wh/km,

That's optimistic. According to my favorite power and speed calculator, 20Wh/km at the wheel is about what he'll need to maintain 40km/h on flat ground with no wind, on a city bike. Include slopes, winds, stops/starts, and efficiency losses between battery and wheel, and I think it will be quite a bit more than 20 Wh/km.

 

[Felixaustria]

However, to further quantify, 40km/h on a draggy e-moto will require 20Wh/km,

That's optimistic. According to my favorite power and speed calculator, 20Wh/km at the wheel is about what he'll need to maintain 40km/h on flat ground with no wind, on a city bike. Include slopes, winds, stops/starts, and efficiency losses between battery and wheel, and I think it will be quite a bit more than 20 Wh/km.

This is why I estimated a total consumption of 10-15 kWh for 300-400 km in 40km/h moped mode
I use this tool http://kreuzotter.de/deutsch/speed.htm (you can switch to English language)
For a quick estimation I assume a 2% slope, then divide the result by 0,75 system efficiency

I also take into consideration, that our friend does not want to or maybe he is physically unable to use the pedals, and therefore needs some reserves of capacity.

@ fatty: no matter if the batteries are about 50 kg (Lipo in bags) or 80 kg (LiIo in cases). Both figures are too much for a regular bike and trailer. Our friend would need to carry additional stuff with him, let us assume 10 kg. The total weight points to a special bike like modified cargo bike or tandem

 

[Chalo]

However, to further quantify, 40km/h on a draggy e-moto will require 20Wh/km,

That's optimistic. According to my favorite power and speed calculator, 20Wh/km at the wheel is about what he'll need to maintain 40km/h on flat ground with no wind, on a city bike. Include slopes, winds, stops/starts, and efficiency losses between battery and wheel, and I think it will be quite a bit more than 20 Wh/km.

This is why I estimated a total consumption of 10-15 kWh for 300-400 km in 40km/h moped mode
I use this tool http://kreuzotter.de/deutsch/speed.htm (you can switch to English language)
For a quick estimation I assume a 2% slope, then divide the result by 0,75 system efficiency

That's the same calculator I use, and it confirmed my suspicion that 8 kWh would not do the trick.

 

[flippy]

8kWh would weigh 30 kilos even with the best 18650 cells. 33 with a nice case and waterproofing.

 

[Felixaustria]

@flippy
My 10s4p 21700-50E has about 700Wh nominal and weighs 3,6 kg. It is build into a rigid ABS box, IP66.
Scaling up to 8 kWh i get 41 kg
Scaling up to more realistic 15 kWh i get 77 kg
The cases still have to mounted to the frame or trailer.
So we talk about something like 50-80 kg for the batteries alone. Too much for a regular trailer at 40 km/h

Therefore I would recommend a cargo bike if I had to reach the unrealistic goals of 400km in moped mode on a single charge.

Honestly: the goal is absurde. If the thread owner was my uncle I would recommend:

• Drive slower
  Charge at half time
  Use the pedals
  Try to get along with less weight and energy

 

[Felixaustria]

My 10s4p 21700-50E has about 700Wh nominal and weighs 3,6 kg

This battery gives me reach of 100 km at 27 km/h on a flat road, with pedalling.
I can charge it in about 2 hrs with my Meanwell HLG320 (almost 2 kg)

This comparatively lightweight setup still feels like a normal bicycle.
It allows me to go 200 km per day.
I really love a long brake for charging at half time, because I need to eat, drink, relax and regenerate.

400 km require to be in the saddle for more than 10 hrs.
I doubt that a person not willing or able to pedal will be fit enough because I know from my own experience, what it takes to do that. 5 hrs per day is ok. 10 hrs require some fitness and experience in endurance sports, f.e. in using the pedals of a bicycle :wink: .

 

[john61ct]

13s8p alone can not give 100km specially when attached with a 15kg trailer. I was talking about 2 batteries that I use when I take longer trips. The extra battery is EV battery (li-ion) but each cell is 20Ah. I have tested only ~100 km only without any additional load such as a trailer.

Charging battery on the side of the road takes a lot of time. With current charger (4A) it takes about 6 hours to charge one battery and 5 the other.

So are you absorbing yet that your goals are unrealistic?

Any decent battery can charge in 90min without harm.

Better ones can charge in 45min only sacrificing a small percentage of lifecyles off the back end.

Either reduce your total miles per day goal, or accept you need to recharge en route.

Buying a high-amp charger, and better quality batteries

are absolutely necessary to get anywhere in the goals you've set for yourself.

Stop arguing, start opening your mind to the facts being so generously offered to you by people that know hundreds of times more than you.

 

[azad]

Honestly: the goal is absurde. If the thread owner was my uncle I would recommend:

• Drive slower
  Charge at half time
  Use the pedals
  Try to get along with less weight and energy

I like your through analysis. The only reason I wanted to do a moped mode is because here bicycles are not allowed on highways. Actually not even on most of the bigger streets interconnecting the cities and I aim to do intercity travel. The faster travel means I can get quickly back to bicycle route and my exposure to getting in trouble would be minimum.

Charging is difficult because I am still not sure how can one charge a battery so quickly on side of the road. Waiting for 2-3 hours for 1h travel mean you only get to travel 2-3h in the day and rest the wait.

 

[azad]

13s8p alone can not give 100km specially when attached with a 15kg trailer. I was talking about 2 batteries that I use when I take longer trips. The extra battery is EV battery (li-ion) but each cell is 20Ah. I have tested only ~100 km only without any additional load such as a trailer.

Charging battery on the side of the road takes a lot of time. With current charger (4A) it takes about 6 hours to charge one battery and 5 the other.

So are you absorbing yet that your goals are unrealistic?

Any decent battery can charge in 90min without harm.

Better ones can charge in 45min only sacrificing a small percentage of lifecyles off the back end.

Either reduce your total miles per day goal, or accept you need to recharge en route.

Buying a high-amp charger, and better quality batteries

are absolutely necessary to get anywhere in the goals you've set for yourself.

Stop arguing, start opening your mind to the facts being so generously offered to you by people that know hundreds of times more than you.

90min for how long? I guess you are suggesting again 100km @ 25km/h. Well it would mean 4h travel and then 90 min charging and then 3-4 hours of travel to end the day. Ofcourse this would mean max 200km per day. Which is actually not very significant to what I could already do with my batteries at 40km/h. I can go to 100km within 2.5h but then charging them is altogether different matter.

I am not arguing, I am just discussing. I appreciate all the good answers.

 

[azad]

400 km require to be in the saddle for more than 10 hrs.
I doubt that a person not willing or able to pedal will be fit enough because I know from my own experience, what it takes to do that. 5 hrs per day is ok. 10 hrs require some fitness and experience in endurance sports, f.e. in using the pedals of a bicycle :wink: .

It only requires 10h of saddle sitting if you do it at 25km/h. If it is 40km/h it should be just 4-5h and I have already replaced the saddle to chopper motorcycle

 

[flippy]

or just build/buy a moped/scooter at that point...

 

[john61ct]

>> Any decent battery can charge in 90min without harm.

>> Better ones can charge in 45min only sacrificing a small percentage of lifecyles off the back end.


> 90min for how long? I guess you are suggesting again 100km @ 25km/h.

No, I am talking about refilling your pack(s) to 100%

regardless of your Wh per km efficiency

regardless of your Ah capacity.

Waiting for 2-3 hours for 1h travel mean you only get to travel 2-3h in the day and rest the wait.

Where are you getting these ridiculous numbers?

You need to recharge en route, period.

So you buy the gear required to do it quickly.

 

[TrotterBob]

I would love to see an ebike and trailer parked at a Tesla charging station. That would be cool.

 

[Felixaustria]

400 km require to be in the saddle for more than 10 hrs.
I doubt that a person not willing or able to pedal will be fit enough because I know from my own experience, what it takes to do that. 5 hrs per day is ok. 10 hrs require some fitness and experience in endurance sports, f.e. in using the pedals of a bicycle :wink: .

It only requires 10h of saddle sitting if you do it at 25km/h. If it is 40km/h it should be just 4-5h and I have already replaced the saddle to chopper motorcycle

I hope we agree that 10*25=250 while 10*40=400 and 4-5 times 40 results in 160 - 200 (which is less than 400)
You wanted to make 400 km / day, and this would require 10 hrs / day at 40 km/h

You say that highways are the only connection between two cities A and B and forbidden for bicycles. Why do you insist on using a bicycle there? It makes no sense to me. You could use a car/bus/train to cover these highways, and carry your bicycle with you or rent a bike. When the nice bike path your actually want to reach, starts at City B, you can start your bicycle tour at B. This should be cheaper, safer and more fun.

 

[azad]

Waiting for 2-3 hours for 1h travel mean you only get to travel 2-3h in the day and rest the wait.

Where are you getting these ridiculous numbers?

You need to recharge en route, period.

So you buy the gear required to do it quickly.

Suppose, you start the travel and drain both batteries in 2h (i.e. at 40km/h). Now even two 10A chargers shall charge the batteries in minimum 3h). Considering we call 8 hours a day, we have already past 5h and we can hardly repeat the same again. Which mean at best you can get 3h (~150km) of actual travel time out of 8h.

 

[azad]

or just build/buy a moped/scooter at that point...

Don't have a license and don't want one either Peddles are good to have!

 

[john61ct]

You need to recharge en route, period.

So you buy the gear required to do it quickly.

Suppose, you start the travel and drain both batteries in 2h (i.e. at 40km/h). Now even two 10A chargers shall charge the batteries in minimum 3h). Considering we call 8 hours a day, we have already past 5h and we can hardly repeat the same again. Which mean at best you can get 3h (~150km) of actual travel time out of 8h.

Again, you use the charger you need, to get the job done in the desired time.

10A is nothing, think big, 80A is common.

~1.5 C-rate total is what to look for, ability to do a healthier 0.4C when you're not in a hurry.

Smaller than that, there is no point.

 

[azad]

You need to recharge en route, period.

So you buy the gear required to do it quickly.

Suppose, you start the travel and drain both batteries in 2h (i.e. at 40km/h). Now even two 10A chargers shall charge the batteries in minimum 3h). Considering we call 8 hours a day, we have already past 5h and we can hardly repeat the same again. Which mean at best you can get 3h (~150km) of actual travel time out of 8h.

Again, you use the charger you need, to get the job done in the desired time.

10A is nothing, think big, 80A is common.

~1.5 C-rate total is what to look for, ability to do a healthier 0.4C when you're not in a hurry.

Smaller than that, there is no point.

So you suggest I change the batteries because I don't think these batteries can support 80A and perhaps none out there can. One EV battery that I have can only support 1C max (20A) and the other one is china 18650 which came with a 4A charger and I am sure might blow if you charge it that fast.