System Sizing: Balancing enclosures and getting the desired kW of rated power and kWh of energy storage
Aloha from the Blue Planet Energy Technical Team,
We are glad that you are here, thank you. This document is for those of you that are getting creative with larger system designs, adding capacity to existing systems or helping your customers understand what options are available for future expansion to help close a deal. For what ever reason you are reading this, we are grateful for your commitment to your education and your commitment to representing Blue Planet Energy. We are committed to changing the way we power the world by making energy awareness delightful. When you have read this document, please let us know if we can help you better understand anything outlined below.
As a general guideline, the number of battery modules that can be installed in each Blue Ion enclosure for a given system is recommended to be the same, but it is not required. Each BMU has independent cycle count, state of charge, and cell balancing algorithms that operate and track data independently over time. Charging and discharging one battery enclosure more than another does not have a negative effect on the other surrounding batteries in the same way that it would with a traditional lead acid battery or another inferior lithium product that doesn't have the same power electronics that we do in our systems. That said, when you have the option to balance the systems then it's a good idea to create a balanced system for an even wear pattern on the entire system. Please also keep in mind that customers must add a minimum of 4 kWh of capacity at a time to any given system (2 battery modules per addition). The resulting capacity per enclosure can only be in increments of 8 kWh, 12 kWh or 16 kWh. There are no other creative combinations available for each battery enclosure.
Please also remember that each battery enclosure has one Battery Management Unit (BMU) that is capable of 8 kW of rated power. Please size the system appropriately for the larger of either charging or discharging requirements in each system. One of our enclosures has more power for loads than any 48 Volt inverter on the market and is adequate for ~10kW@STC of photovoltaics depending on your climate. A good guideline to remember is one inverter per enclosure as a maximum. If you have two inverters, you will most likely need two enclosures to maintain the rated power requirements regardless of your desired kWh of storage requirement. Even with larger inverter systems we have found that designers are using one or more enclosures per inverter to achieve large power and energy storage capacities.
Enclosure combination examples to illustrate sizing options
Example 1:
24 kWh of energy storage is the desired or target system design for your customer.
Two preferred options are available with Blue Ion.
Option 1 - 2 enclosures with 12 kWh of batteries (6 battery modules) in each enclosure.
This will correspond to 16 kW of rated power and 24 kWh of energy storage.
Option 2 - 3 enclosures with 8kWh of batteries (4 battery modules) in each enclosure
This will correspond to 24 kW of rated power and 24 kWh of energy storage.
Example 2:
40 kWh of energy storage is the desired or target system design for your customer.
Now there are two acceptable options to match exact target design for your customer; one with an even number of battery modules per enclosure and another that is not balanced between enclosures. You could either choose 40kWh with 5 enclosures or 40kWh with 3 enclosures to achieve your desired energy storage design target with different power capabilities.
Option 1 - 5 enclosures with 8kWh of batteries (4 battery modules) in each enclosure.
This will correspond to 40 kW of rated power and 40 kWh of energy storage.
Option 2 - 3 enclosures, two enclosures with 12kWh of batteries (6 battery modules) in 1 enclosure with 16kWh of batteries (8 battery modules)
This will correspond to 24 kW of rated power and 40 kWh of energy storage.
NOT RECOMMENDED- Alternatively, you could have two enclosures with 16 kWh and one enclosure with 8 kWh to meet your target of 40 kWh. Although technically this would work, we recommend that you use the previous options where the enclosures are more closely balanced and the pricing from BPE reflects this desired solution as well.
Adding battery modules to an existing system
If a customer wishes to add on to a system they already own the same rules apply, they must add two battery modules at at time (4 kWh) and it is preferred to keep the enclosures balanced as you add more battery modules into the system.
Example 1:
64 kWh of energy storage is the desired or target system design for your customer.
The customer already has a 48 kWh system configured with 4 enclosures for a total of 32 kW of rated power with 12 kWh in each enclosure. The customer wishes to add on 16 kWh of new storage. The customer can have this option by adding 4 kWh of batteries to each enclosure (2 more battery modules to each enclosure). This will increase the system energy storage capacity to 64 kWh but the 32 kW of rated power will remain the same.
Example 2:
68 kWh of energy storage is the desired or target system design for your customer.
A customer already has a 48 kWh system configured with 6 enclosures for a total of 48 kW of rated power with 8 kWh in each enclosure. The customer wishes to add on 20 kWh of new storage. The customer can have this option by adding 4 kWh of batteries to 5 of the enclosures (2 more battery modules to 5 enclosures). This will increase the system energy storage capacity to 68 kWh but the 48 kW of rated power will remain the same.
Thank you for your attention to details with system design. Please email technical support for any further clarifications.
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