Low temperature reduces battery power capability. In heavy equipment, that can lead to voltage sag, controller trips, and avoidable battery damage during charging.
This case study outlines how Holo Battery redesigned a 48V 400Ah LFP battery system for a Norwegian electric excavator fleet operating in winter conditions down to −25°C.
The Problem
The customer operated 50 electric excavators in the Oslo region. The original machines used standard 48V 400Ah LFP battery packs with no active preheat function and no effective low-temperature charge interlock.
A -25°C, la impedancia celular aumentó bruscamente. Durante el levantamiento de objetos pesados, las bombas hidráulicas generaban corrientes explosivas de hasta 300 A. En esas condiciones, el voltaje del paquete cayó lo suficiente como para activar la protección contra subvoltaje del bus de CC de 36 V de la máquina. Los operadores informaron de cuatro a cinco reinicios por turno.
La carga creó un segundo problema. Debido a que el sistema original no imponía una secuencia de precalentamiento antes de la carga, la carga podía comenzar mientras las celdas aún estaban por debajo de la ventana de temperatura segura. Durante una temporada de invierno, las mochilas perdieron aproximadamente el 30% de su capacidad utilizable.
El rediseño de la batería
Holo Battery developed a thermally managed LFP system for low-temperature field use. The pack uses a 15S configuration with a nominal voltage of 48V. The design addressed three areas: pack heating, heat retention, and charging control.
1. Distributed Heating
Polyimide heater films were integrated between cell modules. The heating network provided up to 0.8W/cm² of controlled heat flux.
When connected to grid power, the pack could be warmed from −25°C to 15°C in about 45 minutes.
2. Thermal Insulation
The module assembly was insulated with 3mm aerogel to reduce heat loss during outdoor use. After preheating and typical operation, the pack maintained core temperature above 15°C during a two-hour idle period at −25°C ambient.
3. Preheat-Before-Charge Logic
El BMS controlled charger access based on internal temperature feedback. When the machine was plugged in, incoming power was routed first to the heaters. Charging remained disabled until the pack reached a validated minimum temperature of 15°C.
The 15°C threshold was selected based on internal test data showing acceptable charge acceptance and negligible plating risk at this temperature for the cells used.
This prevented charging at unsafe cell temperature and reduced the risk of lithium plating.
Test Results
Test condition: 300A pulse discharge at −25°C ambient.
The original pack was tested at ambient temperature. The Holo Battery system was preheated before pulse testing.
| Métrico | Original Standard Pack | Holo Battery Engineered System | Practical Impact |
|---|---|---|---|
| Pack core temperature at test start | −25°C | 18°C | Higher usable power |
| Voltage sag during 300A pulse | 14.2V drop | 3.1V drop | Fewer shutdowns under lift load |
| Charge control in sub-zero conditions | No effective preheat interlock | Charging enabled only above 15°C | Reduced low-temperature charge damage |
| Capacity loss after one winter-equivalent season | 32% | <2% | Longer service life |
Note: Capacity retention was measured at room temperature before and after one winter-equivalent operating season. One season represents about five months of use at eight hours per day. Actual results depend on duty cycle, charging behavior, and thermal exposure.
Business Impact
El cliente estimó el coste del tiempo de inactividad en aproximadamente 150 dólares por hora. Según la pérdida de productividad reportada, las interrupciones por clima frío costaban alrededor de 600 dólares por máquina al día.
El reemplazo de la batería agregó un costo adicional. Los paquetes originales a menudo requerían ser reemplazados después del funcionamiento en invierno, a un costo aproximado de 4.500 dólares por paquete.
Después del rediseño, la flota monitoreada completó dos temporadas de invierno sin reemplazos de baterías atribuidos a daños en la carga por baja temperatura y sin reportes de paradas por clima frío durante el funcionamiento normal.
El cliente recuperó el coste adicional de ingeniería en unos cuatro meses.
Por qué es importante
En entornos bajo cero, la confiabilidad de la batería depende de algo más que la capacidad nominal. Las baterías de equipos pesados deben diseñarse como sistemas termoeléctricos.
That means accounting for:
- cold-start temperature
- peak current demand
- insulation strategy
- idle heat loss
- charge interlocks
- BMS logic
- service conditions in the field
For construction and off-highway equipment, these factors directly affect uptime and total cost of ownership.
Next Step
If your equipment operates below freezing, send Holo Battery your peak current profile, duty cycle, charging method, and minimum ambient temperature atventas@holobattery.com.
Our engineering team can provide a thermal architecture recommendation within 48 hours.
