Selecting the incorrect cells for your solar PV or backup application can be a costly mistake, as many people and many inexperience installers have already paid dearly by being haste full in their cell selection for new PV systems and also when upgrading old gel and lead acid batteries to LiFePO batteries
The LiFePO battery uses a lithium-ion-derived chemistry and shares many advantages and disadvantages with other lithium-ion battery chemistries. However, there are significant differences. LFP chemistry offers a longer cycle life than other lithium-ion approaches, however charge and discharge control is paramount for longevity.
This is not so simple as two different manufactures might offer the same capacity and the same warranty, but if you look closely the one model might only provide 20A while the other may be able to provide up to 250A and these ratings might be influenced by temperature and time curves. Which in leamans terms means, that there must be a big difference between the two brands.
So in order to better understand this issue we need to look closely at the different model and determine what model will work best under the conditions require.
The important facts to consider when selecting LifePO4 are the Battery Chemistry that will give you the power you need and the number of cycles you require offer the lifespan of the product.
The requirements must be found as follows:
- Operating power requirements at high demand
- Charge and discharge peak times
- Maximum operating current required during Grid-Power failures.
- Discharge and charging protection
- Temperature monitoring and safety
- Number of cycles required
- Data logging for fault-finding and planning
- Under voltage protection
- Over voltage protection
- Short Circuit protection
In order to make the proper selection, planning need to be done that include loads assessments and power requirements, as well as charging and discharging.
Its also very important to monitor the batteries against any internal failures as well as the temperatures. Charging current must also preferably use temperature compensation when charging the cell during cooler and hotter days, this will greatly improve the lifetime of the cell.
So what it all boils down to is make sure before you purchase expensive batteries that you get what you pay for and that the charger will be able to meet the requirements of the cell, else you might have to buy new batteries sooner than what you planned.
We provide detailed designs and specifications at a reasonable price, and will defnitly help you safe a fortune, by desiging a system that will use the correct equipment form day 1.
Please contact us should you want to plan properly before embarking, or if you already made a mistake and want to correct it.
Comments by Orbic Solar
4KW Grid-Tied Solar System in Somerset West
Unfortunate we are currently only in Cape Town area. We ...