APC Back-Ups CS 650 - modify battery charge voltage

[ro0ter]

Hello all,

Haven't paid this forum a visit in a long time, glad to be back.

I face a problem (more of a curiosity) regarding one of my APC Back-Ups CS 650 (the one that is still working, the offerin other one curiou chirps for about 2 weeks then it dies with the battery deeply discharged inside.. could be the acid that affected way back one of the battery connectors):
- I am exchanging its lead-acid battery (12V 7Ah AGM) for a LiFePO4 one (4s2p x 32700 6.5Ah, 5C discharge rate, so 13.3v@13Ah)
- the problem is that the UPS floats the battery at 13.5V, which is beyond the long-life recommended voltage....

I would like to:
1. Understand the charging model of this UPS;
2. Change the maximum charging voltage (13.25V) and the inverter shutoff voltage (12.8V) of the UPS (eventually also the shutdown message voltage to 13.0V).

Not sure whether this can be done from software out hardware changes are required...

I do have technical expertise (I'm a so-called electronics hobbyist, DIY-er), it's just that the circuit seems to be too hard to reverse-engineer and I hope there is someone having more experience with these UPS-es that can give me some hints.

I have already chewed through every thread about my ups model, haven't found much useful stuff, though...

I am hereby thankful for your help,
ro0ter

 

[onpa]

Hi ro0ter,
any progress ? I'm facing with battery charging issue - no current is flowing into battery. If I don't charge battery, after couple of days is beeper announcing low battery voltage...
Unfortunately, no schematic of this UPC was found.

Regards,
Ondrej