Hi All,

I know battery cable length has been discussed but I need to triple check. I want to connect my second Hubble AM2 to my Sunsynk inverter.

Positive and negative cable from inverter to battery disconnect same length.

Positive from battery disconnect to first battery 125cm

Negative from battery disconnect to second battery 180cm

Negative and positive between batteries 53cm

Sorry for sounding absolutely stupid, cable length need to be the same length, is it the cables between the batteries or the total length of the positive and the total length of the negative ?

Thanks in advance.

If you add the length of positive and negative cables from each battery's point of view, they must be equal.

Looks like yours are fine.

B1 positive 125cm, negative (53 +180)cm

B2 positive (53+125)cm, negative 180cm

Am I missing something?

I am still confused on the matter

Your jumpers between both batteries should be the same length and also of the same rated amps. (if both are equal length {53cm} in your case = Correct)

Your jumpers between both batteries to Fuse/Isolator should be the same length and also of the same rated amps. (Positive - 125cm Negative - 180cm in your case = NOT Correct)

Same on Total length:

Positive 125cm + 53cm = 178cm

Negative 180cm + 53cm = 233cm

Thanks,

Will replace the positive lead from fuse to battery with same length as negative lead

52 minutes ago, Virwat said:

Your jumpers between both batteries should be the same length and also of the same rated amps. (if both are equal length {53cm} in your case = Correct)

Your jumpers between both batteries to Fuse/Isolator should be the same length and also of the same rated amps. (Positive - 125cm Negative - 180cm in your case = NOT Correct)

Same on Total length:

Positive 125cm + 53cm = 178cm

Negative 180cm + 53cm = 233cm

The extra loss due to the longer cable is about 0.4W on my calculation which is close to nothing more than the shorter cable due to the 44% extra length 😀 180 vs 125

So just leave the positive and negative as they are ?

As long as connecting cables are the same between units?

Edited May 25, 20251 yr by Kevin Lourens

23 hours ago, Kevin Lourens said:

Positive and negative cable from inverter to battery disconnect same length.

Positive from battery disconnect to first battery 125cm

Negative from battery disconnect to second battery 180cm

Negative and positive between batteries 53cm

To simplify I would do the following,

Point A: Battery Disconnect

Point B: Battery One

Point C: Battery Two

From Point A to Point B is 125cm

From Point A to Point C is 180cm

From Point B to Point C is 53cm

So from the battery disconnect to the first battery is 125cm

From the battery disconnect to the second battery is 180cm

And from the first battery to the second battery is 53cm

Unless the negative cable from the second battery to the battery disconnect is one cable of 180cm and the cable linking the batteries negatives to each other is 53cm and that add up to 233cm, because 125cm and 53cm add up to 178cm which is almost 180cm.

Spoke to Hubble. They recommend that the total length of positive and total length of negative be the same. Cables between batteries same length as well.

Don't want to cause a stir around all the many posts on cable lengths. Even with a say 0.1V drop on the + cable and 0.2V on the negative the inverter receives 0.3V less than at the battery terminals. We try to keep them the same but nobody will be able to notice a difference than if both had a 0.1V drop. No risk within reason or performance. All we can see is the measured difference in length.

Even support guys can give answers on what they have to reply😀

If we want to split hairs then the + can be longer as the BMS switching the - does introduce a larger volt drop due to this switch.

Edited May 27, 20251 yr by Scorp007