Parallel batteries (again!)

[Yak]

I just wondered if you had run tests where the extender has a higher initial voltage?

 

[AntonioAlfaro]

Yes I did, but I avoid that condition because Extender provide current to the Main battery . This scenario is no necesary to use.

 

[AntonioAlfaro]

DIY Extender is made to provide current to the motor not to charge the main battery. This is safety and friendly operation mode ( sharing the load with the main battery) .
I think that Mahle Extender works in another way, but for me it is not the case.
The DIY is a system that works perfectly with the Mahle system, but at no time should it be understood as exactly the same functionality as the Extender Mahle. The operating approach is different, although the power interface is the same.

 

[Yak]

I have the name and contact information of the special Ebikemotion charger cable connector manufacturer. The minimum order is 200 units. I thought about making these myself but it is not for me. Would you like this, to make millions of euros . For free, of course?

 

[AntonioAlfaro]

Yako, I really appreciate your offer. My days of R&D engineer belong to the past, I am old and just want to enjoy my last days doing cycling. DIY extender was my contribution to your initial project. Enjoy the extender and have very nice rides with more battery capacity. Do not hesitate to contact me if further comments or help.

 

[AntonioAlfaro]

Hi Chamzamzoo, have you come across this, it might do what you want:

DC 10-70V to 5-58V Buck Boost CV CC Voltage Regulator Adjustable Power Module | eBay

The circuit structure of the buck module cannot be adjusted by short circuit. Constant current adjustable: 0.5-8a. 70 52 46mm (with radiator and fan). Weight: 70g bare board, 120g radiator, 135g fan.

www.ebay.co.uk

The extension battery feeds this regulator which you adjust to give up to 2A at up to the fully charged voltage of the original battery. Then to the original battery it looks like a charger and supplies the first 2A of {charging current + motor load}, if any.

Unlike the 'batteries in parallel' method no mods are needed to the original battery, no diode in other words, which I'd guess is why the bike's makers chose the 'extender' route.

The battery voltages needn't be matched, the extender battery's voltage can safely be higher, or it can be lower and will be boosted as needed (up to a point).

This does rely on the external battery cells having a generous current rating, and on its LVC protection, and on the original BMS working with an extender (tick). You should gain about 80% of the extender pack's capacity.

I'd fit a diode in the regulator's output, just in case, and choosing similar battery voltages should make for a stable, efficient regulator. I've not used this one myself but maybe it's worth a punt.

Anthony

Hi Antonny,
I have made an extender for Orbea Gain D50 working in parallel with the main battery. In fact the parallel approach work well sharing the load demanded by the the motor. It is not a charger so some initial conditions must be taken into account to avoid main battery damage.
Agree with you that the "charger"approach extender is more safety, clean and easy to use and at the end 75W to charge battery or to the load is generous power.
I would like to test this approach, so I would like to know your experiences and learning and any feedback you can provide. Thanks a lot.

 

[AntonyC]

It's not something I'd want to use because of the low efficiency but it solves a problem where you can't tap into the bike's wiring. There's some good advice in this thread:
https://endless-sphere.com/forums/viewtopic.php?t=106269