I have an bit of a conundrum and would like some opinions...

I am busy with my own install of 2x parallel Axpert MKS 5000 with 10x 310w panels each, for the battery bank I have dug deeper than intended and gone with 24x Ritar OPz-2v-490ah in a single string.

Balancing the battery bank is what currently has me scratching my head. I am a firm believer in the HA-02 for balancing of series connected batteries, but doing this for 2v cells is a bit of a puzzle. The HA-02 manual says that the system kicks in at a voltage above 2.4v, and then has a low voltage lock-out at 1.8v. The batteries I am using recommend a (cycle use) bulk charge voltage of 2.37v to 2.4v at 25'C.

I would very much like to use 6x HA-02 with balancing over individual cells, but in order to do this I would need to set my charge volts to 57.9v which equates to 2.4125v per cell, as apposed to the 57.6v recommended which equates to 2.4v per cell. By using the higher charge rate I would expect the HA-02 to kick in when the bank voltage exceeds 57.6, and then continue to operate because I don't ever expect to reach the lower voltage of of 1.8v (43.2v for the bank).

My question is what negative side effects could I expect from employing the slightly higher bulk charge voltage?

My other options would be the following;

• Set a high charge voltage initially to allow the HA-02 to kick in (maybe 58v), and then once the HA-02 appear to be operational I could lower the bulk charge rate to that recommended,
• Forget about individual balancing and use 3x HA-02, with each of terminals balancing 2 cells.

What say ye?

 

Battery - Ritar OPZV2-490ah.pdf

My suggestion:

3x HA02 across 2 cells.

Don't mess with the recommended charging parameters of the very nice and expensive battery bank.

May also void warranty of the bank if you don't follow the spec's.

 

Hi Pilotfish

@incagarcilaso had the exact same problem with his 2V 1500Ah cells. A solution that I put forward to him (which he ended up implementing) was to pair the cells. Since his batteries were in two rows. He arranged the HA02s between the two rows and so had the cells paired up as following

HA02 A 1) Cells 1-2  2)Cells  23-24 3) Cells 3-4 and 4) Cells 21-22

HA02 B 1) Cells 4-5  2) Cells  20-21 3) Cells 6-7 and 4) Cells 18-19

HA02 C 1) Cells 7-8  2) Cells  17-18 3)Cells 9-10 and 4) Cells 15-16

HA02 D 1) Cells 9-10  2) Cells  15-16 3)Cells 11-12 and 4) Cells 13-14 

With this arrangement  each HA02 is "linked" to the one next door and so the whole bank should be even.

Cells 9-10  and 15-16 are common to both C and D  but that doubling up can be between any of the junctions.

Initially @incagarcilaso's Spanish speaking electrician did not have the wires wired up correctly and the HA02 were in fact causing more of a problem.  I had about hour's Skype call and sorted it out. Within days the bank was balanced.

 

 

 

Thanks @Mark and @Chris Hobson for the input - sometimes I know I am being a dummy but I just need someone to remove any lingering doubt!

I will pair the cells