Regen effect on battery blender

[Cryingmadman]

Hi,

I built a 1500 watt rear direct drive ebike for a family member it has a 35 watt controller with dual 48 volt 20 ah batteries. The batteries are not hooked up together as of yet. My relative wants to buy a 60 amp battery blender for me to hook up batteries in parallel .

I took the bike out yesterday to test and tune, a 50 mile jaunt in mountains the bike performance was super. The regen on motor seems to be a great help coming downhill.

My question is what effect will battery blender he wants me to install have on electric system?

Cryingmadman

“Ideas are easy execution is a bitch”



Marie Antoinette

 

[Chalo]

Those things are bull puckey that block both the benefits of putting batteries in parallel and also the possibility of regenerative braking. Even without regen as a feature, they put the controller at risk of overvoltage failure when a direct drive bike rolls down a hill faster than the motor's unloaded speed.

Battery food processors are not a substitute for due diligence, and they come with several disadvantages.

 

[lnanek]

Yeah, with the cheap AliExpress blender I have, any input into the batteries is blocked. So if I set my Baserunner controller for regen, it just trips a fault on the first downhill and has to be plugged into a computer to clear the fault in Phaserunner suite.

I've seen battery blenders that claim to support charging, though. If that happens through the discharge connector, it would support regen as well. Takes double the MOSFETs though, to support both directions, I think. So it is extra circuitry they typically don't have.

 

[docw009]

Good idea, Inanek. Add a two way control and enable it off a brake lever with some additional smarts,



.

 

[calab]

They would claim anything for a sale.

 

[E-HP]

I took the bike out yesterday to test and tune, a 50 mile jaunt in mountains the bike performance was super. The regen on motor seems to be a great help coming downhill.

My question is what effect will battery blender he wants me to install have on electric system?

Tell them that they will lose regen if they use the blender, but you recommend the blender anyway.
I don’t usually see the point of using them, but in this case, for safety, it’s probably best to protect the user from themselves.

 

[lnanek]

Good idea, Inanek. Add a two way control and enable it off a brake lever with some additional smarts,

The ones that have a charging function typically have it on a separate cable from the discharge cable, unfortunately. It's the small cable here:

So that's a lot of current to switch between cables if you want to move the controller back and forth between the two. BMS' typically use a half dozen MOSFETs in parallel to be able to switch that much without building up too much heat. I suppose I've seen some rotary battery selector switches that could handle it, though. Or a pair of physical contactors driven like relays. Too complex for me to wire up reliably on any of my bikes.

I'd recommend just getting matching batteries. Battery blenders are mostly useful for combining different voltage or capacity packs which you can be stuck with in upgrade situations. Some systems support range extension batteries that plug into the charge port of the main pack too.

 

[Chalo]

I'd recommend just getting matching batteries. Battery blenders are mostly useful for combining different voltage or capacity packs which you can be stuck with in upgrade situations.

Actually, they don't help at all for different capacity packs of the same voltage. Those will faithfully stay with each other as long as they remain connected in parallel. The only precaution you have to take is to avoid connecting then when they're at different voltages.

The only thing of value that battery food processors do is to let you use packs of different voltages without having to switch them out. The solution for that situation is don't do it. Use packs one at a time if they're different voltages. Duh.

 

[E-HP]

The only thing of value that battery food processors do is to let you use packs of different voltages without having to switch them out. The solution for that situation is don't do it. Use packs one at a time if they're different voltages. Duh.

While I agree that unless the two packs have different nominal voltage there’s no technical reason to have one; I think there’s an argument that anyone that thinks they needs one, probably does, for the safety of all involved.

 

[Chalo]

While I agree that unless the two packs have different nominal voltage there’s no technical reason to have one; I think there’s an argument that anyone that thinks they needs one, probably does, for the safety of all involved.

Whoever thinks he needs one, needs to use one battery at a time, full stop. Nothing good can come of willfully ignorant people messing around "creatively" with high energy batteries they don't understand.