Electronics > Power/Renewable Energy/EV's

Charging a battery with two charge controllers

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Mahmoud_yehia:
Hello,
I am working on a solar car project and i need to charge a 48 V Li-ion battery pack (18650 cells), but i have to use mini-sub arrays (~ 400W) and connect each with a MPPT charge controller.
what i would like to know is :
- Can i just connect the battery pack BMS (Battery Management System) charging leads in parallel to the charge controllers ?
- what battery management system should i use for this 48 V 100 Ah pack ?
- would you recommend a configuration where a use a buck or a boost charge controller ?
i would really appreciate your input.
thank you

Seekonk:
You throw around a lot of fancy terms, do you understand the implications?  I would never let a MPPT controller anywhere near my system.  I do operate at power point which is easy enough to calculate for multiple arrays.  Two MPPT controllers would definitely fight each other.  You need a processor that has central control and not hack together a bunch of commercial crap.

Mahmoud_yehia:
i am new to this, can you elaborate?
are you saying that i shouldn't use a mppt controller!
wouldn't i be losing energy ?, i know it may be a small percentage but in a solar car, you need every bit of energy.

station240:
The issue with multiple charge controllers, is getting them to recognise when the batteries are charged. As they can finished charging and switch to float mode, then see the other charger's voltage still present on the battery assume it's a fault and disable themselves.

Another issue is limiting the charge current, do you set each charge controller to a fraction of what the batteries needs, then lose power if some cells output less ?

What you really need is either a master/slave capable charge controller, or some sort of bigger device with multiple inputs.
I have no idea as to what is available that is suitable.

To be honest, the extra weight of the big inductors required for MPPT could make it pointless in a solar car, especially with multiple inputs. As the extra weight could cancel the extra power gained.

I'd suggest having a talk with electrodacus
and look at his project.
https://www.eevblog.com/forum/oshw/solar-bms-a-solar-charge-controller-for-lifepo4/
It's not 48V though, but I'm sure he can give you some more expert advice.

Mahmoud_yehia:
well, i will use a battery management system so it will be the one that cuts the feed to the batteries when they are full.
i imagine that i will have a power bus where i will connect the output of my charge controllers, battery charging and discharging leads-with a control system to decide which will be on- and the motor controller input.

i think there might be some interface power circuit that i should use but i don't know any.

i am already in contact with electrodacus.

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