Cell count, charge state and room airflow were kept in one gas-risk calculation
The worked bank uses 24 PowerSafe DDm 2 V cells for a nominal 48 VDC string and separates published battery data from assumed room values. Equipment record: EnerSys PowerSafe DDmP 125-33 LP, companion identifier DDmP125-33 LP. Decision: Accept the preliminary ventilation design only when the exact DDm cell count, applicable charge-current basis and verified room airflow are entered into the manufacturer and code calculation.
Twenty-four cells in one room
VRLA construction reduces normal gas release compared with a freely vented battery, but it does not remove the need to assess charging, fault ventilation and room accumulation. The battery manual controls installation clearances and charging limits. The mechanical record controls the actual room volume, exhaust path and fan status.
For EnerSys PowerSafe DDmP 125-33 LP, the applicability boundary is anchored to 2 V/cell, 200 m3/h and part DDmP125-33 LP. The 5 worked inputs remain assumptions until they are recorded at the equipment.
Confirm availability and catalogue details for EnerSys PowerSafe DDmP 125-33 LP or DDmP125-33 LP on the catalogue of UPS replacement batteries page.
Figure 1. EnerSys PowerSafe DDmP 125-33 LP equipment and power path
Battery, charge and airflow inputs
The controlling numerical record is: Nominal cell voltage: 2 V/cell; Worked series cell count: 24 cells; Worked nominal string: 48 VDC; Worked charging input: 1 A; Worked room volume: 30 m3; Worked verified exhaust flow: 200 m3/h. Each value has a defined source or assumption status in the engineering ledger. Values from different configurations are not combined as though they came from one installed system.
| Engineering parameter | Value | Evidence status |
|---|---|---|
| Nominal cell voltage | 2 V/cell | Published OEM value |
| Worked series cell count | 24 cells | Worked design assumption |
| Worked nominal string | 48 VDC | Worked design assumption |
| Worked charging input | 1 A | Worked design assumption |
| Worked room volume | 30 m3 | Worked design assumption |
| Worked verified exhaust flow | 200 m3/h | Worked design assumption |
The 24-cell series count establishes 48 VDC nominal, but gas generation depends on the applicable charging condition, not string voltage alone. The 200 m3/h airflow and 30 m3 room volume provide a preliminary dilution-capacity index. They do not replace the manufacturer or code hydrogen calculation.
A preliminary air-change capacity check
The worked check uses air changes per hour = 200 m3/h / 30 m3. With a measured or verified 200 m3/h exhaust flow and a 30 m3 room, the result is 6.67 air changes per hour. This is an airflow-capacity check only; final hydrogen concentration uses the applicable OEM and code gas-generation inputs. The arithmetic is reproducible, but it remains a design check until the listed inputs are confirmed at the equipment.
The 6.67 air changes per hour result follows from air changes per hour = 200 m3/h / 30 m3. If the 24 cells input changes, this check is repeated rather than carrying the earlier result into a different operating state.
Figure 2. Quantified basis for the EnerSys PowerSafe DDmP 125-33 LP decision
Normal charge and abnormal ventilation states
The room check includes normal float, boost or equalize, charger fault and fan-failure states. An airflow value is usable only when the exhaust path reaches a safe discharge location and replacement air can enter without short-circuiting directly to the fan.
Battery quantity and charger current must represent the installed bank. Adding a parallel string or changing the charger setting invalidates the original calculation. Temperature alarms and fan proving contacts are included when the ventilation design depends on powered exhaust.
No field procedure is inferred from the preliminary index. A qualified designer applies the current manufacturer instructions and electrical, fire and building requirements for the jurisdiction before the room is accepted.
| Path | Technical consequence | Disposition |
|---|---|---|
| Apply the stated engineering decision | Accept the preliminary ventilation design only when the exact DDm cell count, applicable charge-current basis and verified room airflow are entered into the manufacturer and code calculation. | Selected basis |
| Generic model substitution | Select by family name or rating alone, without confirming the exact configuration. | Not selected on the stated evidence |
| Unverified operating assumption | Treat a design assumption as though it were a site measurement. | Reconsider only if the input changes |
Confirm availability and catalogue details for EnerSys PowerSafe DDmP 125-33 LP or DDmP125-33 LP on the UPS selection and battery help centre page.
Confirm availability and catalogue details for EnerSys PowerSafe DDmP 125-33 LP or DDmP125-33 LP on the UPS system catalogue page.
The EnerSys PowerSafe DDmP 125-33 LP decision retains part DDmP125-33 LP, the 6.67 air changes per hour calculation result and the manufacturer-published 2 V/cell point in one equipment record. Applicable OEM instructions, qualified electrical authority and the installed single-line or wiring record remain controlling for any executable work.
Proving fan flow and alarm response
Acceptance of EnerSys PowerSafe DDmP 125-33 LP depends on five recorded checks:
- Confirm PowerSafe DDmP 125-33 LP cell model and actual installed quantity.
- Record float, boost and fault charging-current bases from the applicable OEM design.
- Measure room volume and verify the exhaust discharge and makeup-air path.
- Measure or commission the stated 200 m3/h airflow and fan-failure alarm.
- Complete the manufacturer and code hydrogen calculation before acceptance.
The EnerSys PowerSafe DDmP 125-33 LP record is not accepted if part DDmP125-33 LP does not match, the calculation does not reproduce 6.67 air changes per hour, or the final operating state is not recorded. The equipment returns to the approved safe state when a check stops, and the unresolved condition remains open without an invented repair result.
Figure 3. Verification sequence for EnerSys PowerSafe DDmP 125-33 LP
Final acceptance requires the OEM gas formula
The worked 6.67 air changes per hour shows that the assumed fan can exchange the assumed room volume. It is not a hydrogen concentration result. The bank remains unqualified until the exact charging and gas-generation inputs are applied.
GDF’s UPS service page covers field measurements and service work for EnerSys PowerSafe DDmP 125-33 LP.
Decision rule: Accept the preliminary ventilation design only when the exact DDm cell count, applicable charge-current basis and verified room airflow are entered into the manufacturer and code calculation. A different model, load, voltage, battery string, software version or operating state requires a new check against the applicable manufacturer record.
Sources
- EnerSys PowerSafe DDmP product record
- EnerSys PowerSafe DDmP 125-33 LP installation manual
- GDF Technologies, internal engineering reference: UPS Maintenance/UPS Battery Testing and Condition Assessment.md
- GDF Technologies, anonymized field-case library, used only where the text identifies a retained field fact.