question

Bruce Richard avatar image
Bruce Richard asked

Hooking up +B1 and +B2 on Bus Bars

I have Nissan Leafs 48 volt - being wired to Busbars
Screen Shot 2019-04-06 at 1.42.18 PM.png

I am trying to place the +B1 and +B2 wires in the best place using the Battery Monitor / Shunt / Temp Sensor.

I am adding additional batteries to the bus bar later and wanted to keep adding them to the bus bars with same cable sizes.

Where would be a good place to install these 2 wires from the shut in this diagram?

I see the midpoint diagram that came with the Battery monitor, but I have 2 - 48 Volt cells instead of the diagram in the brochure that appeared to be wired using 12v cells.

I will be wiring up 4 total Leafs as extra budget allows until I find my ah requirements met.

BMV Battery Monitorwiring
screen-shot-2019-04-06-at-14218-pm.png (117.9 KiB)
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.

2 Answers
Mark avatar image
Mark answered ·

Wire B1 to somewhere on the positive battery bus bar.

Your diagram shows 4x 48v batteries/banks wires in parallel - so I cant see any point where you can physically access the 'mid-point' of the batteries (which would be ~24v).

Accordingly, I don't think that you can monitor the mid-point voltage of these particular batteries.

However, if you can somehow access the the link between central cells (and there are an even number of cells in each battery), then you would have to also link all the 4x battery mid-points together.

But even if this is physically possible, it may not be a good idea if you have a separate BMS for each battery or cell - it might get confused since the each bank/cell will not act independently after linking the mid-points.

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.

boekel avatar image
boekel answered ·

Like Mark says: you need a bms (slave) for every string of batteries, the midpoint connection for the BMV is not for these batteries, you can use that for a temperature sensor or something.

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.