how to use Solid State relay (or normal relay) with sbms0

[luka grimbergen]

Hello,

I'm looking at the sbms0. I want to use it in a rc solar boat I'm building for a school project (I'm 17 years old and from the netherlands). To turn the load and mppt of I want to use relays. The battery type i'm using is LiPo. Is this possible with the sbms0. And how do I connect the sbms to the relay. And can the sbms handle the current of the coil (or the current of de SSR).

Thanks!

[Dacian Todea]

Luka,

LiPo is not a type of chemistry but I guess those are high energy density cells maybe LiCoO2 but may also be LiFePO4

The SBMS0 can not handle more than 50mA so no direct relay coil but it can handle solid state relays or something like Victron BP65 for Loads.

If MPPT is from Victron then those have remote ON/OFF that SBMS0 can control directly.

What will be the battery voltage and also capacity and what solar panels will you be using ?  

[luka grimbergen]

The battery will be 18,5 volt (5s). The capacity is 8Ah. So it is a small battery but that's all I need in the boat. The solar panels will be 2 100W solar panels in series. the specs are: 16,7 V, 5,99 A. I was reading about the BP100 (I need a 100amp or more relay) but I could not figure out if my setup would be possible with that product. I only saw the possibility to use it with 12v/24v systems. Do you know more about this?. I believe the chemistry is LiCoO2 because the lipo cell voltage is 3.7V. I want to use the victron 75/10 MPPT because that will be more efficient in my setup.

Op zondag 15 november 2020 om 18:47:07 UTC+1 schreef electr...@gmail.com:

[Dacian Todea]

On the charging side you can use this remote ON/OFF cable https://www.victronenergy.com/accessories/ve-direct-non-inverting-remote-on-off-cable this will alwo SBMS0 to stop the charging when any cell gets to set limit (default is 4V) but you can set at 4.2V in your case as you do not care about battery longevity and have very high charge rates.

Based on this https://community.victronenergy.com/questions/26934/difference-between-li-ion-and-relay-mode.html  when battery protect is set in Lithium mode it will work as a solid state relay and both under and overvoltage limits are disabled so it should work  condtroled by the SBMS0 in your application.

SBMS0 is not waterproof as it was designed for indoor use thus you will need to take measure to make sure the SBMS0 stays completely dry if you want to use in this sort of application.

[luka grimbergen]

Thanks for the reply. So if I understand correctly I can use the battery protect in Lithium mode. What the right way to connect the sbms0 to the battery protect and remote on off cable? 

Op zondag 15 november 2020 om 19:23:30 UTC+1 schreef electr...@gmail.com:

[Dacian Todea]

Yes it can be used but considering your application it may be better for your speed controller to take the SBMS0 signal that it needs to stop discharging and maybe send an info to the remote that battery is empty and boat need to be retrieved and not just cut power. Similar method as on EV's where user is warned about low battery and instructed to pull over when it is safe to do so and maybe reduce the power available to motor gradually.  

[Philippe Damour]

Hello. Just a quick note. LiPo stands for Lithium Ion gelified Polymer electrolyte. 

Voltage 3.7V 

Discharge rating: 50C max, 20C continuous
Charging: 1C  with CC/CV charger. Max voltage 4.2V

Pro:  very light because no metal casing, such very good for planes.

Con: average only 150–250 cycles  

[Dacian Todea]

Hi Philippe,

LiPo says nothing about chemistry it can be LiCoO2 or NMC in witch case nominal voltage will be in the 3.6 to 3.7V range with max charge of 4.1 to 4.2V usually but it can as well be LiFePO4 or even LTO

And yes I know what most people refer to when saying LiPo but I can never assume :)  
Same as people that say they have a Li-ion battery thus saying nothing relevant as all the ones mentioned above and more will be Li-ion cells but with very different characteristics.