Lets start with the Objective
1.To increase the backup time of my Double conversion Online UPS
2.Ensure fast recharge for both internal & external batteries
3.Make sure external charger remains completely isolated from the UPS internal charging circuit.
A brief description:
The UPS internal battery is connected to a AC powered timer relay.
The AC powered timer relay also connects to the external battery bank and an external battery charger.
This is a DPDT( Double Pole Double Throw) Relay. Contact rating is 120A@28VDC. Relay Coil runs on 220 AC and directly powered by utility power.
So, when the relay is powered, it will connect the external batteries(75A Batt @ 24VDC) to the external battery charger.
But when power goes out the relay looses power and connects the external battery bank to the internal UPS battery in parallel.
There is a 60mv voltage drop due to relay contacts on both contacts (+ & -) Is this something I should be concerned of?
I've applied this with a Online UPS which has two 9A SLA(Yuasa) at 24VDC bus. Which roughly gives around 30 minutes@ 160 watt load. The internal charger can put put out max 1A.
The two 75A flooded lead acid batteries connected in series with an external SMPS charger which only charges the 75A batteries with a float voltage of 27.29V
A hand sketched design is attached which illustrates the whole modification.
Looking forward to your suggestions, tips to improve my mods.
Thanks in advance.
1.To increase the backup time of my Double conversion Online UPS
2.Ensure fast recharge for both internal & external batteries
3.Make sure external charger remains completely isolated from the UPS internal charging circuit.
A brief description:
The UPS internal battery is connected to a AC powered timer relay.
The AC powered timer relay also connects to the external battery bank and an external battery charger.
This is a DPDT( Double Pole Double Throw) Relay. Contact rating is 120A@28VDC. Relay Coil runs on 220 AC and directly powered by utility power.
So, when the relay is powered, it will connect the external batteries(75A Batt @ 24VDC) to the external battery charger.
But when power goes out the relay looses power and connects the external battery bank to the internal UPS battery in parallel.
There is a 60mv voltage drop due to relay contacts on both contacts (+ & -) Is this something I should be concerned of?
I've applied this with a Online UPS which has two 9A SLA(Yuasa) at 24VDC bus. Which roughly gives around 30 minutes@ 160 watt load. The internal charger can put put out max 1A.
The two 75A flooded lead acid batteries connected in series with an external SMPS charger which only charges the 75A batteries with a float voltage of 27.29V
A hand sketched design is attached which illustrates the whole modification.
Looking forward to your suggestions, tips to improve my mods.
Thanks in advance.
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