DIY - Custom range extender

[PSaibot]

Hello Guys,

So here I am to make my first post, apart from the introduction one.

Some context first.
I ride a 2021 Cube Stereo Hybrid HPC 140 TM 625Wh. It's my first ebike and I bought it in second hand few month ago still in 2023.
This ebike its simple gorgeous and very well equipped, I never gave attention to Cube as a brand but now I am a fan. Cube delivers very high end ebikes at very competitive prices comparing both equipment and price with other brands.
So I got positive surprised.

Now Buying a 2021 ebike in current year 2023 means that I will face a 625Wh VS 750Wh Smart System (SS) challenge.
Two of my friends bought a recent 2022 KTM's Macina Prowler Master 750 SS and so they have +/- 25KM more in battery range comparing with me.
This means that every time we have a long ride (more than 50km) I have to be extra careful managing and switching the assist modes in order to arrive home with Battery.

That's why I started to search for battery range extenders. Quickly I found out that Cube doesn't has one and I found a new brand called Volabike that make them but with an high cost (at least for my wallet).

Since I am an electronics enthusiast I start thinking in a way to build my own range extender and I was successful.

Here what its needed:

- Soldering Iron
- Electric tape
- Silicon Electric Wire 18 awg
- XT60 Plugs (Male and Female)
- 10S 30A BMS
- 18650 Lit-Ion Cells
- 18650 Spacers
- 18650 tape
- Spot Welder DIY Kit
- Nickel Stripe
- Side way bottle holder

Seems too much but it isn't.

Usually ebikes, scooters, etc use LG MJ1 18650 cells because they have 10A discharge rate and has 3500mah capacity.
Since LG cells were too expensive I have used Panasonic NCR18650BD cells.
I have built a 10S2P battery, 36V with 6,36Ah and 229Wh that weights +/- 1,2Kg.

For all that concerns Spot Welding and BMS Soldering part there's plenty of videos in youtube explaining step by step.

I have coupled it direct in the Black (negative) and Red (Positive) wires that are in the big plug that connects to bosch motor, so making positive with positive and negative with negative (Parallel=Same Voltage and sum the capacity of each battery).
The battery its hold in the Side way Bottle holder with Velcro.
The setup has a very minimalistic and simple sigh view.

Now I am happy to say the with less than 50€ I have built my own range extender, and now I have 625Wh (from Bosch PowerTube Battery) + 229Wh (from range extender) = 854Wh in total.
I am heavier (body) comparing to my friends and still has more riding range as they have.

I will soon attach some images.

So For those who are thinking in spending thousands in buying a new ebike because of the extra range that 750 ones provide, think twice as with +/- 50 to 100€ you can build a range extender and keep your ebike.
The more cells you add the more range you will have but more heavier the battery will be, and of course you need to respect the maximum Wh that Bosch Motor supports, in what regards to Performance Line CX its 11XX WH but to be in safe side try not to exceed 1000Wh in total.

This not a detailed DIY, I know and sorry for that, but its more to show you that it's possible to build your own a cheap custom battery to improve the range of our ebikes and avoid wasting thousands in a new ebike just to follow the marked tendency.

Regards

 

[Stevewild31]

Hello Guys,

So here I am to make my first post, apart from the introduction one.

Some context first.
I ride a 2021 Cube Stereo Hybrid HPC 140 TM 625Wh. It's my first ebike and I bought it in second hand few month ago still in 2023.
This ebike its simple gorgeous and very well equipped, I never gave attention to Cube as a brand but now I am a fan. Cube delivers very high end ebikes at very competitive prices comparing both equipment and price with other brands.
So I got positive surprised.

Now Buying a 2021 ebike in current year 2023 means that I will face a 625Wh VS 750Wh Smart System (SS) challenge.
Two of my friends bought a recent 2022 KTM's Macina Prowler Master 750 SS and so they have +/- 25KM more in battery range comparing with me.
This means that every time we have a long ride (more than 50km) I have to be extra careful managing and switching the assist modes in order to arrive home with Battery.

That's why I started to search for battery range extenders. Quickly I found out that Cube doesn't has one and I found a new brand called Volabike that make them but with an high cost (at least for my wallet).

Since I am an electronics enthusiast I start thinking in a way to build my own range extender and I was successful.

Here what its needed:

- Soldering Iron
- Electric tape
- Silicon Electric Wire 18 awg
- XT60 Plugs (Male and Female)
- 10S 30A BMS
- 18650 Lit-Ion Cells
- 18650 Spacers
- 18650 tape
- Spot Welder DIY Kit
- Nickel Stripe
- Side way bottle holder

Seems too much but it isn't.

Usually ebikes, scooters, etc use LG MJ1 18650 cells because they have 10A discharge rate and has 3500mah capacity.
Since LG cells were too expensive I have used Panasonic NCR18650BD cells.
I have built a 10S2P battery, 36V with 6,36Ah and 229Wh that weights +/- 1,2Kg.

For all that concerns Spot Welding and BMS Soldering part there's plenty of videos in youtube explaining step by step.

I have coupled it direct in the Black (negative) and Red (Positive) wires that are in the big plug that connects to bosch motor, so making positive with positive and negative with negative (Parallel=Same Voltage and sum the capacity of each battery).
The battery its hold in the Side way Bottle holder with Velcro.
The setup has a very minimalistic and simple sigh view.

Now I am happy to say the with less than 50€ I have built my own range extender, and now I have 625Wh (from Bosch PowerTube Battery) + 229Wh (from range extender) = 854Wh in total.
I am heavier (body) comparing to my friends and still has more riding range as they have.

I will soon attach some images.

So For those who are thinking in spending hundreds in buying a new ebike because of the extra range that 750 ones provide, think twice as with +/- 50 to 100€ you can build a range extender and keep your ebike.
The more cells you add the more range you will have but more heavier the battery will be, and of course you need to respect the maximum Wh that Bosch Motor supports, in what regards to Performance Line CX its 11XX WH but to be in safe side try not to exceed 1000Wh in total.

This not a detailed DIY, I know and sorry for that, but its more to show you that it's possible to build your own a cheap custom battery to improve the range of our ebikes and avoid wasting hundreds in a new ebike just to follow the marked tendency.

Regards

Hi, Nice write up, so the bike draws power from both batteries simultaneously, Have you ridden to depletion to check actual range and is the extra power reflected in your controllers estimate of power/range remaining? Looking forward to pics of your build (and placing an order lol).

 

[PSaibot]

Hi, Nice write up, so the bike draws power from both batteries simultaneously, Have you ridden to depletion to check actual range and is the extra power reflected in your controllers estimate of power/range remaining? Looking forward to pics of your build (and placing an order lol).

Hi Steve,

I have only a comparison, so far, because I haven't had yet the opportunity to drain all the batteries juice in an extended long ride.

First of all I forgot to mention that our bikes are unrestricted, and we are maybe 50% of the time above the standard cut off, so continuously draining battery.
And I weight 100kg.

In my first ride in the woods with only the 625 battery, we made almost 65km always pedaling and many times above the speed cutoff limit, using mainly emtb mode and I ran out of battery in the last 5kms coming home.

Now with the custom range extender similar route, using Tour (for straight roads - 30%) and Emtb (for high climbs - 70%) we made a 55km ride and I have arrived home with still 49% of battery so I drained only 51% in the ride.

Its an huge improvement in range extender, I would say that my extra battery provides me +/- 30km extra range.

About the other question, no, this extra battery does not show on Kiox, I mean the range doesn't increase, it's still the same 625 standard.

Bosch (motor and Battery) are an ecosystem and I cannot add the extra battery to this ecosystem.
Bosch has a way to recognize its own battery.
The Powertube battery don't provide any voltage, the motor must first to send a 5v signal to the battery so it knows that its time to deliver the full power, and it uses 2 thin wires as the signal (green and yellow).
So here I just added the extra battery in parallel to the main power wires red and black on the motor.

So basically both batteries are balancing each other charge while they are at same time both discharging to the motor, so the drain its now also being supported by the extra battery, so the effort its spited in 2 and means that the main bosch battery will be more cooler.
You can only notice in Kiox that the current battery % it's not decreasing as fast as it was before without the extra battery.

 

[funnel]

Nice. Did a similar thing on my previous Giant 500Wh ebike. Except I didn't connect them in parallel. I first rode only the extender battery and then I stopped and uplugged and replugged in the original battery. I used a beeper on the extender to see when it discharged.

 

[PSaibot]

Nice. Did a similar thing on my previous Giant 500Wh ebike. Except I didn't connect them in parallel. I first rode only the extender battery and then I stopped and uplugged and replugged in the original battery. I used a beeper on the extender to see when it discharged.

Hi,

Seems also a reliable solution, to use the batttery casing to store the custom One.
The only thing its that you have to carry a the big 500wh powertube batttery on your black bag.

In my case with parallel system the bike carries both batts for me.

 

[funnel]

Hi,

Seems also a reliable solution, to use the batttery casing to store the custom One.
The only thing its that you have to carry a the big 500wh powertube batttery on your black bag.

In my case with parallel system the bike carries both batts for me.

I did it similarly as you and put the lipos in a 2L frame bag. All I needed to do is stop and replug the connector because I didn't find any good small high current switch.

 

[PSaibot]

I did it similarly as you and put the lipos in a 2L frame bag. All I needed to do is stop and replug the connector because I didn't find any good small high current switch.

Lipo? Lipos are small but with high discharge rate, and very ustable on what regards bumps and heat, they are much more likely to easily get on fire comparing with the lit-ion ones.

Are you sure that those lipos do not discharge more than 10Amps at constant current? Just be on safe side to avoid burning the motor.

Also lit-ion and lipos have different charge levels and on parallel since both Will charge each other the original bike battery might suffer a little and have its life reduced due to lipos.

Anyway in order to preserve the main battery health, i connect both in parallel since the begining of my Ride. Because on parallel if you discharge too much the main batt, example you Ride ONLY using main batt and at middle of the Ride you connect the extra batt on parallel, since the main batt its much more discharged it will receive an high current peak from the extra batt and they will balance and wont deliver great power to motor. And this high peak will harm the main batt and reduced its long term life time and will give you a big Sparks when you connect the extra batt.

So the best its to start the Ride already with both batts connect in parallel and do not power off the bike during the Ride breaks.

 

[Mabman]

Good work @PSsaibot! Love a good hack that is cheap and efficient.

 

[maddchadd]

Great work @PSaibot ! Was wondering how/where exactly you connected to the motor? Also, do you charge both batteries through the normal charging port or you charge the extender seperately? Thanks!

 

[PSaibot]

Great work @PSaibot ! Was wondering how/where exactly you connected to the motor? Also, do you charge both batteries through the normal charging port or you charge the extender seperately? Thanks!

Hello,

I have connected the plug for the extender directly on the main plug that connects to the motor.
When you remove the motor plastic protection, on the left side you will see 3 plugs connected to the motor, the 2 small/thin ones are the signal plugs that interact with the display and control buttons (it's where we connect the chip as well) and the remain plug it's the biggest one has 4 wires on it, 2 thik wires (Red and Black) that are the wires that provides all the power from the main battery to the motor and other 2 thin wires (Green and yellow) that are the signal wires (for battery % measure, etc).
So on the thik Red (Positive) and Black (Negative) wires on that plug I cut out a little the wire cape to expose the wires and soldered there my red and black wires from my extender plug, so red on red and black on black (Parallel) in order to keep the same voltage but increasing the Ah (capacity).

About the charger, Yes I can charge both batteries at same time using the Bosch charger, but since the bike only recognizes the main powertube battery when it reaches the 100% and stop charging it doesn't mean that the extender is as well fully charged that why I prefer to charge in separate.
For that I use a scooter/hoverboard 36V (42V 2A) charger from my kids ones and just added there a second output plug (the female XT60) so I can continue using it to charge the kids kick scooter and when needed to charge my extender battery as well and it will act like it was charging a scooter, it stops charging when the battery is full.
These chargers are really cheap, mine its unbranded and costed 10€.

 

[maddchadd]

Wondering how this is currently holding up...any errors or issues in general? I would like to take this on but thinking of using Bosch's own dual battery y cable to create a removable solution. I know I saw another forum member (@TrailwattsUK) testing a range extender set up for bosch that used this cable but they added something to the cable (fuse? capacitor? voltage regulator?). @PSaibot

 

[PSaibot]

Wondering how this is currently holding up...any errors or issues in general? I would like to take this on but thinking of using Bosch's own dual battery y cable to create a removable solution. I know I saw another forum member (@TrailwattsUK) testing a range extender set up for bosch that used this cable but they added something to the cable (fuse? capacitor? voltage regulator?). @PSaibot

View attachment 117222 View attachment 117223

Hello,

I also thought about that Y Bosch cable, but happens that that cable its more expensive than my custom extender battery!!!

I have always the chance on adapting that cable any time as i kept all the original stuff in place.

Zero errors, yes.

Has I explained in some previous replies, this extender is invisible to Bosch ecosystem, and what it does in reality its to support the drain of the main battery by draining as well (split the drain effort) and help to keep both batts balanced on charge, so you will ONLY notice that the battery charge % on display wont reduced as fast as it was without the extender.

Now o am confident enought to go for long rides with my 750wh friends because I have more than 800wh

 

[maddchadd]

Got it, thanks again. I'm guessing what is attached to that wiring harness there is an "ideal diode" so that current cant flow between the batteries. Shouldn't be an issue unless there is a discrepancy between voltages though right?

*or maybe it's a fuse

 

[PSaibot]

Hi,

To be honest I don't know either.
I doubt it would be self balance protection because both batteries have the same chemistry and voltage output.
In my opinion the current should flow between both batteries so they can balance each other and split the discharge effort, i is healthier for the cells.
I see in your image near your red circle that that mysterious thing has 3 red wires and 1 black, it is almost for sure a fuse.

 

[funnel]

You don't need any diode as long as you connect them both charged at about the same amount. You could put a fuse if you wanna be really safe. Even if you accidentally do it most probably nothing bad will happen. The full one will charge the empty one. Initially with high current but for a short time until they equalize. I parallel charged my hobby lipo batteries for more than 10 years even 10 at once without any problems. As long as you do it correctly it's all good. Even if one is full and others are empty never anything bad happened in my case.

 

[maynard]

Very impressive. My understanding
Of electronics is a bit poor. So not an option for me I . Well done mate

 

[Zimmerframe]

Very impressive. My understanding
Of electronics is a bit poor. So not an option for me I . Well done mate

But you just admitted in the other thread that you own some electrical tape !

 

[mike_kelly]

There is some risk in doing this. When you parallel two batteries one will have a slightly higher voltage than the other and that battery will tend to discharge into the the lower voltage battery. If they are very close in voltage that will work fine. But if one battery is much lower voltage than the other the higher voltage battery can discharge at a high current rate and cause damage to both batteries or a fire.
The safer way to do this is to use a Parallel Battery Switch. The device monitors the voltage on both batteries and turns off the lower voltage battery until the higher voltage battery is used for a while and it's voltage drops to match the lower voltage battery. They it turns them both on. If one battery drops lower then again it turns it off until they match again. This prevents the two batteries from getting too much of a voltage difference and stops violent discharge of one into the other.

 

[maddchadd]

Ok, so I have been wanting to do something like this since I first got my niner wfo e9 (same bosch system as the cube) and after the inspiration and motivation from @PSaibot I decided to go for it. Instead of splicing and soldering to the motor wires, I wanted a removable solution so I went with Posi tap connectors (very reliable and good connection). I went with a 10s3p 8000mah battery with a built in bms I found on amazon for about $100 (I've built lithium packs in the past but just didnt want to deal with it right now). So I wired everything up, charged the batteries up ran some tests and all seems good to go. Went out for my first actual ride last night and unfortunately every time I attempted a steep climb in "turbo" mode, the system shut down and threw a "550" error (impermissible load)...after rebooting it worked again but subsequently threw the same error every time I was climbing a steep grade. Im not ready to totally scrap the idea so thinking of trying an "ideal diode". Seems like maybe the motor is able to draw too much current now that it has the batteries combined? Or maybe the system has a newer firmware and is more sensitive to tampering? Any ideas or thoughts are much appreciated! @PSaibot @funnel @mike_kelly @TrailwattsUK

 

[mike_kelly]

Wild guess is that it is the opposite your system is wanting more current for the climbs and can't get it. Maybe your wiring is to small for the current demand.

 

[maddchadd]

Wild guess is that it is the opposite your system is wanting more current for the climbs and can't get it. Maybe your wiring is to small for the current demand.

When I unplug the external battery, I dont get the error anymore. I didnt really do anything to the existing wiring, just "tapped" it with the posi tap which is rated for more current than the existing wiring and the external battery has bigger gauge wire than the Bosch Motor wires.

 

[funnel]

In theory the battery could transmit data about the amount(in mAh) it discharged to the motor. If the motor checks if the amount discharged from the battery is about equal to the amount it received and consumed by the motor it could trigger an error. This is just a guess how an internal check could work. I never modified a bosch system so I don't know.

 

[mike_kelly]

The Bosch battery is also 36v?
As noted above if the Bosch battery is a "smart battery" i.e. transmits data via canbus etc to the controller that could be your problem because your DIY is not able to communicate.

 

[maddchadd]

The Bosch battery is also 36v?
As noted above if the Bosch battery is a "smart battery" i.e. transmits data via canbus etc to the controller that could be your problem because your DIY is not able to communicate.

Yes, both 36v and I thought the same thing and why I was hesitant to try it in the first place but decided to go for it as Psaibot had success. Again, the only time I got the error was when I was climbing in turbo mode on a steepish grade so in my mind it has to be connected to that extra load somehow.

 

[funnel]

The Bosch battery is also 36v?
As noted above if the Bosch battery is a "smart battery" i.e. transmits data via canbus etc to the controller that could be your problem because your DIY is not able to communicate.

For example the Giant motors don't trigger any error and don't check anything over the canbus com like mentioned above. I made 20000km with custom external batteries on the Giant without any issues, still works fine. Not sure about the Bosch since I don't have any experience modifing it. Maybe a custom canbus man-in-the-middle type of hack would be needed if this is the case.

 

[mike_kelly]

The big difference is the load when you are climbing steeply. So I think the problem is not being able to supply the power. Maybe the voltage sag under load is greater for the DIY battery than the original.

 

[maddchadd]

The big difference is the load when you are climbing steeply. So I think the problem is not being able to supply the power. Maybe the voltage sag under load is greater for the DIY battery than the original.

Ok, but the system still has the original battery in parallel to supply needed voltage always, so theres never a time when it doesn't have that power available as far as I understand.

 

[maynard]

But you just admitted in the other thread that you own some electrical tape !

Yeah my whole life is being held together with that stuff

 

[mike_kelly]

Ok, but the system still has the original battery in parallel to supply needed voltage always, so theres never a time when it doesn't have that power available as far as I understand.

No not true. The difficulty with Lion batteries in parallel is that the higher voltage battery will always try and "charge" the lower voltage battery. When both batteries are nearly the same voltage everything is ok. But if your DIY battery sags badly under load the internal battery may be discharging into the DIY battery as the motor is demanding high current. The current from the internal is being split between the motor and the DIY battery....

 

[maddchadd]

I understand what you are saying but from my tests so far, it looks like the external battery always has a higher voltage after they have both been connected for a short period of time. Even if there is no load, the internal battery is coming to a resting voltage that is lower than the external. Could be that it is older and has more cycles causing it to sag faster BUT it never has an error when running by itself. Before ever installing the external battery I remember checking voltage on it and getting around 38-39v when the bike is just sitting after being fully charged. Anyone else with a bosch ebike if you get a chance could you check voltage with a multimeter from the charge port after the bike has been sitting for awhile?

No not true. The difficulty with Lion batteries in parallel is that the higher voltage battery will always try and "charge" the lower voltage battery. When both batteries are nearly the same voltage everything is ok. But if your DIY battery sags badly under load the internal battery may be discharging into the DIY battery as the motor is demanding high current. The current from the internal is being split between the motor and the DIY battery....

But you are right, could still be a voltage sag issue under load either way. My intuition tells me it is the opposite though and the motor is able to draw more current than it normally would OR the system is detecting some extra voltage from the external somehow. I know this can happen with external lights and what not if they short circuit.