Regen Brake and Ampere meter installation

[Infinity]

Hello my eFriends,

My MP3 eBike is nearly finished  ,  now I have questions about the regen brake system and Ampere meter installation.

I use 48v Lifepo4 and its rated with max. 10A charge current. The charger uses 60V.
What will get to the lifepo4 if I use regen brake? 60V ? or variable?
Can it get over 10A?
Is this regen brake system shortage the cycle lifetime (DOD) for the lifepo4 akku?

I would find it useful if I get infos about the current Ampere usage while riding.
I have seen that the cable for light has the 48V if I activate light button.
Can I get from this cable the Ampere usage from the MP3 or where I has to place it?

best regards,
infin

[Bikemad]

Hi Infin andto the forum.

With a 48V battery, the regen current is unlikely to be as high as 10 Amps unless you are travelling very fast.

I have not been able to test my MPIII properly yet, but the regen current on my 26" MPII is only just over 5 Amps at ~30mph with a 48v Pack, but nearly 17 Amps with a 24V pack.

The voltage and current produced will vary according to the road speed and wheel diameter, but it should not harm your battery pack.

To measure the current, the ammeter (or its separate shunt) needs to be wired into the battery feed wires so that all the current used by the motor passes actually through it.

Unfortunately the battery voltage from the thin lighting cable cannot be used for an ammeter, but it could be used to power a digital voltmeter which could even be turned on and off using the lighting switch if necessary.

Alan
 

[Infinity]

Hi,

Thanks Alan for the fast and good reply.

What if the V from regen brake is lower than from the lifepo4? My understanding from what I know is that the charge V must be greater than the battery cell V. Or will the BMS from the lifepo4 manage the right charge?

I want to install a DC/DC step down Converter to 12V from the lifepo4 for light and a car charge plug.
Is it possible that the regen brake can effect this negative when its variable energy goes to lifepo4? Should I install a Diode?

best regards,
infin

[Bikemad]

If your DC/DC converter has a maximum input voltage at at least 60V, and you don't use regenerative braking while going down a very long steep hill at more than 25mph with a fully charged battery, it is unlikely to have any detrimental effect on the converter, as the battery voltage should remain well below the converter's maximum input voltage.

The BMS cannot boost the voltage from the motor, so if the voltage being produced during regenerative braking is not greater than the battery voltage, then no charge will be transferred to the battery, but the motor will still perform as an electromagnetic dynamic brake.

There should be no need to install a diode for the DC/DC converter, other than to protect the converter from reverse polarity in the unlikely event of it being connected to the battery with its input wires reversed. 

Alan