question

grsinva avatar image
grsinva asked

US Van Drawing BJE-300D Design Problems

The BJE-330D design was almost perfect for my travel trailer. I purchased two 200Ah LiFePO4 batteries, the Lynx DC Distributor, VE Bus BMS V2, Cerbo GX, Smart MPPT 100/50, Orion-Tr Smart 12/12-30 DC/DC charger, Smart Battery Protect 100, 500A SmartShunt, 2 200W Solar Panels, 8ga cable, MP4 connectors, and assorted fuse holders, fuses, buss bar - that's most of it. I did not purchase the MultiPlus-II Inverter/Charger. I've encourtered two immediate problems:

1) My trailer uses a AC/DC Converter Charger, so it appears I cannot use the Smar Battery Protect for my DC loads - my DC connection to the DC fuse panel is bi-directional. Is there an alternative, or do I just omit/return the Smart Battery Protect?

2) The VE.Bus BMS V2 manual says "...the BMS obtains battery from the VE.Bus. As such, the BMS connot be used without a VE.BUS Inverter/charger or a VE.Bus Inverter." Is there an alternative to using an Inverter/charger? I am not ready to purchase an Inverter, and may in fact never need one.

Thank You - Greg

Multiplus-IIBattery ProtectVE.Bussystem design
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

4 Answers
pwfarnell avatar image
pwfarnell answered ·

1. Load disconnect

You MUST have a disconnect on your DC loads and non Victron chargers to protect the battery from under or over voltage and low or high temperature as the Victron batteries do not have cut offs in the batteries. If you had separate charge and discharge lines you would need 2 battery protects, one for loads and one for chargers controlled from the ATC and ATD connections. Can you split the charger to a separate connection. The Battery Protects are good as they have low power requirements. As an alternative you can use BOTH a Victron Cyrix-Li-charge PLUS a Cyrix-Li-Load disconnect relays on the common line working from the ATC and ATD signals so both loads and charging are covered. However, the problem here is on under voltage where you really want to disconnect the loads but not the charger as you need to recharge the battery. The same applies on over voltage, you need to keep the loads on to discharge. If you follow this route, the Cyrix-Li-Load goes closest to the battery. You then need to prepare restart methods in either under or over voltage situations. Best option is to split the loads and charger and get a second Battery Protect. See links for Cyrix relays.

https://www.victronenergy.com/battery-isolators-and-combiners/cyrix-battery-combiners

and

https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-120-A-EN.pdf

2. VE Bus BMS

See an earlier post about connecting negative to the VE Bus BMS without an inverter.

https://community.victronenergy.com/questions/206038/vebus-bms-v2-not-powering-up.html

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

grsinva avatar image
grsinva answered ·

My Solution for #1: I will isolate the AC/DC converter, run the output through a Battery Protect, and into the Lynx Distributor. I will then have a separate uni-directional DC Load coming out of the Lynx Distributor and through another Battery Protect. Will this suffice?

I'm still studying the Small BMS. It appears I need a "VE.Direct non-inverting remote on-off cable" to handle my MPPT 100-50 SmartSolar solar controller.


1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

pwfarnell avatar image pwfarnell commented ·

#1 your solution will work.

#2 I do not have experience with the small BMS, you will have to check the manuals and schematics but you are correct it will need a connection as the Small BMS does not do DVCC. Could you put the Solar through the same Battery Protect as the ac/dc charger.

0 Likes 0 ·
grsinva avatar image
grsinva answered ·

The max current of my Solar Controller + AC/DC converter is less than the max allowed by my Battery Protect. If that's my only constraint, I think it will work.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

grsinva avatar image
grsinva answered ·

Will my Cerbo GX disconnect my SmartSolar MPPT100/50 via the VE.Direct connection in the event of battery over-temp/voltage? My smallBMS is not hard-wired to the Cerbo GX, so I'm assuming (hoping) the Cerbo or Solar MPPT obtain this information via Bluetooth.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

pwfarnell avatar image pwfarnell commented ·

No, the small BMS does not manage items via the Cerbo as it does not connect to the Cerbo. You either need to put the MPPT output through the charging Battery Protect, which is not ideal as the MPPT can spike up in voltage on a disconnect or you connect the ATC output of the small BMS to the remote terminal on the MPPT. Look at the manual Figure 3.3.2, this shows a Victron non inverting remote on off cable for your exact need.

https://www.victronenergy.com/battery-management-systems/smallbms#manuals

2 Likes 2 ·