Manual 3rd party battery replacement

BillP · ‎2021-06-28

Hi,

I have an old APC BackUPS CS650 where the battery died and it's been out of warranty for 5 years. So i was wondering whether it was possible to just connect a bigger 3rd party battery externally? or parallel connect 2 12v 7Ah batteries?

Has anyone got any experience with this?

I have CBS and Gaston 12v 7Ah batteries locally for $18, seems like a no-brainer price wise.

Is the electronics/charger inside capable of charging bigger batteries or double of the same battery or will I set my house on fire?

Brad_C · ‎2021-06-28

It's not recommended to increase the battery capacity of those BackUPS units.

It is generally not an issue charging, but when on battery the units rely on a constrained runtime. As they don't have active cooling, they rely on the thermal intertia of the switching components and transformer to not reach meltdown temperatures. When you extend the runtime, they will continue to get hotter and may be damaged.

I put an extra battery on a BackUPS CS650, but it was powering an ADSL modem and network switch (combined load of ~20VA). I ended up with all sorts of issues with the UPS flagging a battery error. I suspect something to do with the additional battery leads, but I never bothered to really track it down. I did do thermal checks and with a very small load there was no issue with heat, but with anything approaching rated load bad things would have happened.

I ended up replacing it with an old SU2200 to get some *real* extended runtime.

See Answer In Context

Brad_C · ‎2021-06-28

It's not recommended to increase the battery capacity of those BackUPS units.

It is generally not an issue charging, but when on battery the units rely on a constrained runtime. As they don't have active cooling, they rely on the thermal intertia of the switching components and transformer to not reach meltdown temperatures. When you extend the runtime, they will continue to get hotter and may be damaged.

I put an extra battery on a BackUPS CS650, but it was powering an ADSL modem and network switch (combined load of ~20VA). I ended up with all sorts of issues with the UPS flagging a battery error. I suspect something to do with the additional battery leads, but I never bothered to really track it down. I did do thermal checks and with a very small load there was no issue with heat, but with anything approaching rated load bad things would have happened.

I ended up replacing it with an old SU2200 to get some *real* extended runtime.