Hey I might be able to get the Victron balancers at a good price! Is it worth the money? 48v would need 3 of them?

2 hours ago, Fnm said:

This is the layout of by batteries, 2 banks of 4 on top of each other.

What is the best way to connect the BMV 702

All your cables should be the same length. I would not wire it this way. 

You also need a bazz bar or a common connector on the side to bridge the 2 banks.

This is totally wrong.

lol Kleva yes I know " moes vir 2 maande maar brood vreet om my batts te beskerm"

Get a chainsaw man and cut it down, just don't ask TTT for help as the smoke might escape from your house.

PS stay away from beer that day as you don't want to let the tree fall down the wrong way as you connected the shunt first 

No chance, both the last two guys have estimated over 8 tons, and thats not cutting it down, thats TRIMMING! Not to mention that it covers 2 properties and a pool. Nope thats a pro job with proper insurance!

1 hour ago, Camel said:

Hey I might be able to get the Victron balancers at a good price! Is it worth the money? 48v would need 3 of them?

What is your price ?

Not sure yet, will check tomorrow,  is it worth it? 

26 minutes ago, Camel said:

Not sure yet, will check tomorrow,  is it worth it? 

For sure

What's the going rands on them?

@jdp, can you please give advise on the buzz bars.

Will it be better to turn the batteries that the termanels face in the same direction?

Unfortunately they can not stand in a 90 deg orientation, I do not have place for that, would be the best.

Hi Fnm - Yes or No with a catch. Just make the cable lengths the same, catch - as short as possible. It's the cable length between terminals that is key to keeping the voltage drop even, shorter cable length keeps it as low as possible. The cable to "buzz bar" doesn't have to be the same length as the ones between the terminals (although better if it can be to get even voltage drops), but must be the same length for all 4 (or 6 if connecting midpoint to a "buzz bar) connections (2 each) to the "buzz bar". For clarity, my pic showed my batteries horizontal like yours, but physically they are vertical, alternating the pos/neg terminals to keep cables as short as diagram. I don't have a seperate midpoint "buzz bar" in my setup (BMV and midpoint only wired a week or so ago), but I should install one.

15 hours ago, Fnm said:

I have the same setup with my batteries but I see you have a wire connecting battery2 neg to battery7 pos.

I do not have that cable in. I believe it is for the victron midpoint reading.

Any other reason for that?

Jip otherwise you will only have the midpoint of one string.

11 hours ago, Camel said:

Hey I might be able to get the Victron balancers at a good price! Is it worth the money? 48v would need 3 of them?

Have a look at HA01 or HA02 battery balancers about a third of the price of Victron BB

Best for me would be to turn batteries in the same direction, that will make the distance between terminals the same length.

My wires from the negative to the fuse and positive to the fuse is also not the same length, need to fix that also.

 

Any body with a photo of how there batteries is connected with a buzz bar?

Just to clarify something. All the battery interconnect cables do not have to be the same length.

However, if you are connecting something like the BMV to measure the mid-point voltage, then the total length of cable on each side of the mid point must be equal. If you have parallel strings of batteries the total length of cable per string must also be equal. The reasoning behind equal lengths of cable is because the cable has resistance and at higher loads higher currents are flowing through the cables and therefor you will have higher voltage drops over the cable and these voltage drops needs to be equal on each side of the mid-point of the battery string if you are measuring the mid point and also needs to be equal in each parallel battery string to ensure the same current flows through each parallel string of batteries.

The reasoning behind the bussbars are the for the same reason - to have equal lengths of cable per parallel battery string to ensure that you have equal resistance and equal voltage drops over the cable and equal current flow through each string.

Thanks superdiy, I will leave the batteries as is and add buss bars both sides and ensure that the length

of cable is equal length both sides. I do understand that having the cable as short as possible is best but

my setup just have to work this way.

1more question, the cable between pos and neg to measure midpoint need to be equal length to any other

or just as short as possible between the terminals. I think of using a copper connector in the middle to connect

the BMV, will that be fine?

4 hours ago, Fnm said:

buzz bar

Okay... I've supressed this knee jerk long enough. It's a 'bus bar'. If it's a buzz bar, you're doing it wrong :-P

Ok seems that one can use any terminal for midpoint as long as it is connected to the other bank as well.

Kleva I see you have connected the pos and neg for your midpoint but the installation diagram shows that you have to bridge the negatives and b2

is connected to the neg terminal.

Thanks plonkster, I suppose it should not making a buzzing noise

 

23 minutes ago, plonkster said:

Okay... I've supressed this knee jerk long enough. It's a 'bus bar'. If it's a buzz bar, you're doing it wrong :-P

I really wanted to say this when I first saw it

2 hours ago, Fnm said:

1more question, the cable between pos and neg to measure midpoint need to be equal length to any other or just as short as possible between the terminals. I think of using a copper connector in the middle to connect the BMV, will that be fine?

I think you have maybe mis-read my explanation. The total length of cable between the batteries on either side of the mid-point must be equal, not only the length of cable connecting the mid two batteries - see below.

Using thick copper bars between the batteries instead of cables should work very well.

 

 

31 minutes ago, Fnm said:

Ok seems that one can use any terminal for midpoint as long as it is connected to the other bank as well.

Kleva I see you have connected the pos and neg for your midpoint but the installation diagram shows that you have to bridge the negatives and b2

is connected to the neg terminal.

It is not about the positive or negative pole, but rather the true mid point of the string of batteries.

Parallel battery strings on its own is something to avoid and by tying the midpoints of different strings together is even worse. If you have multiple strings and want to tie the mid points do it via no more than 5A fuses - that way, if something goes wrong in one string, one or more of the fuses will go open and protect the remainder of the strings.

@superdiy, thanks now I understand 100%

4 hours ago, Fnm said:

1more question, the cable between pos and neg to measure midpoint need to be equal length to any other

or just as short as possible between the terminals.

What I want to know is length of the wire (sorted now) and thickness. Looks like I can use same size as supplied by victron  for the mid connection by connecting the victron wire

directly to a terminal and the another wire of same size to the other terminal with a fuse in(5A).

Sorry for all this but I am not so clued up with all these shenanigans. I rather ask 10 times before I make a F-UP here

Hahaha that is my fault. We call it Buzz bars as we have high voltage bus bars at work. So I am so used to calling it Buzz.as ours really do make a buzsound, OK it is more the high voltage UPS room that holds up the SANReN POP

On 4/26/2016 at 2:13 PM, Fnm said:

What I want to know is length of the wire (sorted now) and thickness. Looks like I can use same size as supplied by victron  for the mid connection by connecting the victron wire directly to a terminal and the another wire of same size to the other terminal with a fuse in(5A).

Sorry for all this but I am not so clued up with all these shenanigans. I rather ask 10 times before I make a F-UP here

No harm done for asking. Yes, you can use thin wire, similar to what they've supplied with the BMV. If a current of more than 5A flows in either cable the fuse should go.