DIY - Custom range extender

[mike_kelly]

Nothing can enable the motor to draw more current. The amount of current it draws is fixed by the design of the motor. The resistance of the windings etc. THe only way it can draw more current than by design is if there is a short somewhere. Since the batteries are in parallel there can't be any "more voltage".
Is the observation of the charge with the original battery or with both?

 

[maddchadd]

Nothing can enable the motor to draw more current. The amount of current it draws is fixed by the design of the motor. The resistance of the windings etc. THe only way it can draw more current than by design is if there is a short somewhere. Since the batteries are in parallel there can't be any "more voltage".
Is the observation of the charge with the original battery or with both?

I'm more so wondering if the motor/controller are built for higher wattage than they are rated (I know bosch gen4 cx performance is rated at 250w but can go much higher at peak power) and the fact that I have 2 batteries in parallel, each with their own 30a bms = 60a potential now, could allow for a higher draw than designed thus triggering the error. I dont know really, just thinking about potential possibilities and taking yours into consideration as well. I guess its possible that the external battery is "weaker" than the bosch powertube but I doubt it as its rated for a 500w nominal motor. As far as the voltage of the system after charging I found ANOTHER new piece of data...the voltage reading from the charge port itself falls rapidly after charging to around 38-39v but the voltage of the bosch powertube battery is higher. Since I have those wires connected directly to the motor wires I checked there and it was the same voltage as when it was fresh off the charger. Very odd.

 

[funnel]

Wait a second. I rechecked your picture and seems like you connected the external battery to the charging port? You need to connect to the wires that go from the battery to the motor. What you're trying to do is charge the battery from the other battery like an external charger. That won't work. You need to tap to the other wires between battery connector and the motor.

 

[maddchadd]

Wait a second. I rechecked your picture and seems like you connected the external battery to the charging port? You need to connect to the wires that go from the battery to the motor. What you're trying to do is charge the battery from the other battery like an external charger. That won't work. You need to tap to the other wires between battery connector and the motor.

Not sure what you are looking at, but I didn’t connect into the charging port, I connected into the red and black wires on the big plug that goes into the motor

 

[mike_kelly]

@maddchadd With all due respect. I am not dissing you. But you don't understand everything you are working with here. LION batteries are dangerous and you can burn down your house if not careful. It is not something you should be experimenting with.

 

[maddchadd]

@maddchadd With all due respect. I am not dissing you. But you don't understand everything you are working with here. LION batteries are dangerous and you can burn down your house if not careful. It is not something you should be experimenting with.

I understand your concern and appreciate it. I have been working with lithium batteries for over 10 yrs and have built several of my own packs from 18650, 21700 and originally a123 cells. I have also been working with lithium polymer packs and discharging/charging them in parallel for over 10yrs as well. What exactly did I say that leads you to believe I shouldn't be doing this? The only "experiment" here really is with the bosch system itself. There isn't anything wrong with my wiring or how Im charging/discharging the batteries, the bike is throwing an error when both of the batteries are charged to the same voltage. Both batteries have 18650 cells and their own bms built in so honestly I dont see any danger to the batteries themselves in this scenario.

 

[mike_kelly]

The problem with using two parallel batteries without a parallel battery switch is the risk of one battery catastrophically discharging into the other. The bosch system clearly has some smart features making it more than just a standard BMS controlled battery. So there are unknowns. Unknowns can lead to hooking something up in a way that might cause problems. You are guessing, as i would be, as to how things are working.
Just saying be careful, meaning charge it outside with a way to disconnect things fast if something starts to go south.

 

[maddchadd]

The problem with using two parallel batteries without a parallel battery switch is the risk of one battery catastrophically discharging into the other. The bosch system clearly has some smart features making it more than just a standard BMS controlled battery. So there are unknowns. Unknowns can lead to hooking something up in a way that might cause problems. You are guessing, as i would be, as to how things are working.
Just saying be careful, meaning charge it outside with a way to disconnect things fast if something starts to go south.

I get it. As I said I have quite a bit of experience running lithium batteries in parallel. A parallel switch won't work with the bosch system because the controller won't give any power to the motor if the bosch battery isn't supplying current. I'm thinking of installing an ideal diode on just the external battery line so that current cant flow from the internal battery into the external but the external battery current could still flow to the motor. That would determine whether or not the error was caused by the bosch battery discharging into the external battery while simultaneously sending power to the motor.

 

[PSaibot]

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

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Hi,

I see similar setup as mine the difference is the battery and the way you join the power wires to the main plug (I soldered and you press connected them).

My honest guess here it's that your battery has different discharge rate comparing with the bosch battery.
Before I build my DIY battery I did some research on the internet and I checked something that might be critical.
All the batteries must/should have the same discharge rate per cell, in this case bosch cells have 20A of continuous discharge rate, and so I bought similar cells to build mine, and you are having that error probably because your custom battery has cells with less discharge rate and it's not compensating the discharge and demanding of the motor because that DIY battery its as well high demanding from the main bosch battery.

Also, Your board computer its different than mine as well as the motor casing too, its your bosh a Gen4 Motor?

Other thing that might be the issue.
Your custom battery has 2 main cords, probably one its for charging/discharging and another one for "discharging ONLY" and you are using that Discharge only plug to connect to the bike. Means that that battery will deny the charge from bosch battery and will send a denial signal back and this causes the 550 error.

I had similar error at the beginning because my BMS had a separate charge and discharge plugs.
I realized that the charge port it's as well a discharge port, so what I did was eliminate the discharge ONLY port and used only the charge plug for both charge and discharge, and the error never came back.

Check this as if so this might be the root cause.

 

[maddchadd]

Hi,

I see similar setup as mine the difference is the battery and the way you join the power wires to the main plug (I soldered and you press connected them).

My honest guess here it's that your battery has different discharge rate comparing with the bosch battery.
Before I build my DIY battery I did some research on the internet and I checked something that might be critical.
All the batteries must/should have the same discharge rate per cell, in this case bosch cells have 20A of continuous discharge rate, and so I bought similar cells to build mine, and you are having that error probably because your custom battery has cells with less discharge rate and it's not compensating the discharge and demanding of the motor because that DIY battery its as well high demanding from the main bosch battery.

Also, Your board computer its different than mine as well as the motor casing too, its your bosh a Gen4 Motor?

Other thing that might be the issue.
Your custom battery has 2 main cords, probably one its for charging/discharging and another one for "discharging ONLY" and you are using that Discharge only plug to connect to the bike. Means that that battery will deny the charge from bosch battery and will send a denial signal back and this causes the 550 error.

I had similar error at the beginning because my BMS had a separate charge and discharge plugs.
I realized that the charge port it's as well a discharge port, so what I did was eliminate the discharge ONLY port and used only the charge plug for both charge and discharge, and the error never came back.

Check this as if so this might be the root cause.

So I tried an ideal diode and still got the same error, so its definitely not an issue of the main battery discharging into the external. The external I have can be charged from the dc port or the xt60 discharge cable so thats not the issue either. I remembered I had another smaller 10s2p pack from a hoverboard I was messing with awhile back and decided to toss that into the mix (yes, I made sure they were the same voltage @mike_kelly ) and low and behold, no errors running that pack in parallel! Its a 4.4ah pack so 2400mah cells but I dont remember the exact details on them. Very interesting stuff. A couple other things to note...when running the bigger 10s3p 8ah external, whenever I checked voltage with my multimeter during test rides, the external was at a lower voltage than the bosch internal battery. Now, with the smaller pack that doesn't give the 550 error when I check its voltage during a test ride, its HIGHER than the internal battery. This is after riding for about an hour. As I said before, clearly the packs arent discharging and balancing into each other as previously suspected. Oh and yes, I am running the bosch gen4 cx performance motor with the 625w power tube, same as your cube @PSaibot I am back to believing its a matter of the larger external pack providing too much current when combined with the bosch battery

 

[kezcelm]

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.

Hi, what bike do You have? I try to connect 3rd party battery to my giant trance '19 and it looks that motor is working ok but there is a battery error on ridecontrol. I'm sure this is because lack of canbus messages from battery, because when I short connect only Can_H & Can_L to bike from original battery, everything works very good. Bike read data from original battery, but energy goes from this not original.

 

[funnel]

Hi, what bike do You have? I try to connect 3rd party battery to my giant trance '19 and it looks that motor is working ok but there is a battery error on ridecontrol. I'm sure this is because lack of canbus messages from battery, because when I short connect only Can_H & Can_L to bike from original battery, everything works very good. Bike read data from original battery, but energy goes from this not original.

I left the original battery in. I split the red power cable and soldered a ground cable inline with the existing one that goes to the motor. So I basically disconnect the red power cable and connect my own external battery in place, the canbus remains from the original battery. When the external battery is discharged(monitored by a beeper) I reconnect the power cable back directly to the motor so the original battery gets discharged.

 

[shmulik]

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

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Hi,
I'm starting my DIY range extender projet. Current, Bosch gen 4, Kiox, 2020 Focus Jam2.
Received from Ali a pack, 4p10s, stating 100 Ah.
I intend to connect it the way you did, bur have a concern. I've disconnected the power plug from the motor and checked if there is 36v there prior to activation of the Kiox. No voltage. So if I connect the extender bettery there will be power supplied to the motor all the time. I'm worried about it.
A solution for that will be a manual switch that will connect the battery only after activation of the Kiox or a relay that'll do it automatically.
Please advice me. I'm totally new to Emtb.