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A 48V 100Ah telecom battery appears easy to understand. Multiply voltage by ampere-hours, and the nominal energy is approximately 4.8 kWh.

But that does not mean the site will receive 4.8 kWh of usable backup energy.

Actual backup performance also depends on the discharge window, load current, temperature, battery age, conversion losses, BMS limits, charging conditions and the voltage range accepted by the telecom equipment.

That is why two batteries with the same Ah rating can behave very differently at the same site.

In discussions with overseas telecom project teams, I usually begin battery evaluation with the operating conditions rather than the catalogue capacity.

Ah does not equal backup time

Before selecting a battery, the project team should confirm:

• the normal and peak DC load;
• the required backup duration;
• the frequency and length of grid outages;
• the minimum voltage accepted by the telecom load;
• low-voltage disconnection settings;
• the available rectifier charging capacity;
• generator and solar operating logic;
• ambient and cabinet temperature;
• expected future load growth.

A battery may have sufficient nominal energy but still be unsuitable if it cannot deliver the required current, recharge before the next outage or operate within the existing system’s voltage window.

Battery sizing should therefore consider both energy and power.

Energy determines how long the load can be supported. Power and current capability determine whether the battery can support the load without triggering protection or excessive voltage drop.

When standard lithium is usually sufficient

For this discussion, “standard lithium” means a telecom lithium battery connected to a compatible DC power system without an additional battery-level DC/DC coordination layer.

It is generally the simpler option when:

• the site is new;
• all batteries are installed at the same time;
• the batteries use the same model and capacity;
• the existing rectifier supports the required charging profile;
• the old battery bank is being replaced completely;
• future expansion can use compatible battery units;
• the BMS can communicate with the site controller or monitoring system.

This creates a relatively uniform battery bank. Current sharing, charging and protection are easier to manage because the batteries have similar electrical and ageing characteristics.

A standard lithium solution can be entirely appropriate for a planned new deployment. “Smart” does not automatically mean “better” for every site.

What smart lithium changes

A smart lithium battery normally adds more control between the internal battery pack and the site’s DC bus.

In the ZTT smart lithium architecture, this includes a DC/DC module. The purpose is not simply to collect more monitoring data. It is to manage the battery’s electrical interaction with the existing power system.

This becomes useful when the project must deal with:

• new and old batteries operating at the same site;
• lithium batteries with different capacities;
• staged replacement rather than full replacement;
• lithium batteries operating alongside legacy lead-acid batteries;
• differences in voltage behaviour or internal resistance;
• controlled output or boost-voltage requirements.

Without suitable coordination, batteries connected in parallel do not necessarily share current equally. A newer battery with lower internal resistance may carry more of the load, while an older unit contributes less. During charging, differences in voltage, SOC and protection settings may create additional imbalance.

A DC/DC-based architecture can provide greater control, but its exact operating logic must still be verified during technical evaluation.

Mixed-battery deployment is a migration strategy

Mixing batteries should not be treated as the default design simply because the equipment can support it.

Its main value is often economic and operational: an operator can introduce lithium batteries without immediately removing every usable legacy battery.

That may help when:

• a network contains thousands of sites with different battery ages;
• only part of the existing bank has failed;
• replacement must be completed in phases;
• the operator wants to reduce site visits;
• immediate full-bank replacement would create excessive capital expenditure;
• disposal and logistics need to be spread over time.

However, mixed deployment also introduces more variables.

The project team should verify:

• which battery chemistries and models may operate together;
• whether each battery has independent current control;
• allowable capacity and age differences;
• charging and discharging priorities;
• current-sharing behaviour;
• fault isolation;
• low-voltage disconnection logic;
• BMS and controller communication;
• alarm visibility;
• recovery after a protection event;
• behaviour during mains failure and restoration.

A supplier should be able to explain the control philosophy, not merely state that different batteries are “compatible.”

Do not ignore the charging system

Battery replacement is also a rectifier-system evaluation.

The existing telecom power system must provide enough current to support the load and recharge the battery within the available recovery period.

This is especially important in weak-grid markets where outages may occur several times per day. A large battery bank that cannot fully recharge before the next outage may gradually operate at a lower SOC, even though its nominal capacity appears sufficient.

The charging assessment should include:

• rectifier capacity after redundancy;
• simultaneous load and charging demand;
• current limits;
• temperature compensation where applicable;
• generator operating periods;
• solar availability;
• permitted recharge time;
• battery communication and charging commands.

Monitoring should support decisions, not only alarms

SOC and SOH are useful, but buyers should ask how those values are calculated, displayed and used.

The site controller or power-management platform should help the operator identify:

• batteries that are not contributing normally;
• abnormal temperature;
• repeated protection events;
• capacity deterioration;
• communication failure;
• imbalance between parallel batteries;
• sites that may fail the next long outage.

Zhongtian Technology Group Co., Ltd. (ZTT Group) provides 48V lithium batteries, smart lithium systems, telecom power equipment and power-management functions. Its standard 48V lithium range includes 100Ah, 150Ah and 200Ah product categories, while its smart lithium solution uses a DC/DC-based architecture intended for mixed-battery applications.

The broader value is system coordination. Battery selection needs to be connected with rectifiers, DC distribution, monitoring, cabinet conditions and the site’s actual outage pattern.

A practical procurement sequence

Before approving a battery supplier, I would ask for five things:

1. A calculation based on the real load and outage profile, not only the requested Ah value.
2. Confirmation of compatibility with the existing rectifier and DC voltage range.
3. A clear explanation of the BMS, alarms and remote monitoring interface.
4. Test evidence for the proposed parallel or mixed-battery configuration.
5. A lifecycle plan covering expansion, replacement, fault isolation and end-of-life management.

The correct decision is not always standard lithium or always smart lithium.

It depends on whether the project is building a uniform new battery bank or managing a gradual transition across an existing, mixed-age telecom network.

Procurement FAQ

1. Does a 100Ah battery always provide the same backup time?

No. Backup time also depends on nominal voltage, usable discharge range, load current, temperature, ageing, losses and protection settings. Two 100Ah batteries may provide different usable energy under the same site conditions. The calculation should be based on the complete discharge profile and the telecom load’s permitted voltage range.

2. When should a telecom operator choose standard lithium?

Standard lithium is generally suitable for new sites or complete battery-bank replacements where all units use the same model, capacity and installation date. The rectifier charging profile, BMS communication, cabinet environment and future expansion plan must still be confirmed.

3. What makes a smart lithium battery different?

Smart lithium commonly adds active control, often through a DC/DC stage, between the battery pack and the DC bus. This can help control output, charging and current sharing when batteries with different characteristics must operate together. Functions vary by manufacturer and model.

4. Can lithium and lead-acid batteries be connected in parallel?

They should not be connected together unless the proposed equipment and control architecture are specifically designed and tested for that configuration. Their charging behaviour, voltage characteristics, internal resistance and protection requirements differ. A project-specific technical assessment is required.

5. Can new and old lithium batteries be mixed?

Some smart lithium systems are designed to support batteries of different ages or capacities, but this is not a universal capability. The buyer should verify current control, charging priorities, fault isolation, communications and the permitted differences between batteries.

6. What information should a buyer provide before requesting a battery proposal?

The supplier should receive the load profile, peak load, required backup duration, grid-outage pattern, existing rectifier information, battery-cabinet conditions, temperature range, current battery configuration, monitoring protocol and future expansion requirements.