Project Solar

Afternoon Gentleman, I am a newby to this forum .
Just started with my DIY solar project and would like your advise on what not to do. This is where i am and my next purchase will be a 5 kw lifepo4 battery.
Anybody that can recommend the most suitable battery for this Inverter pls.
If i am not mistaken Sunsynk not compatable.
Before i forget to mention i want a flat wall mounted battery as space is a issue.

Thank you in advance and i really enjoy the topics here

Fellow eskom victom


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Start here. That’s the whole list of what is supported. In South Africa, you are probably looking at FreedomWON, Blue Nova, Pylontech, BSL, SolarMD, or Hubble.

Make sure you get the sizing right. You have a 3kVA inverter, ideally you need 5kWh to 6kWh of storage. So 2 x Pylontech US3000C is probably what you want.

Thank you for the reply, i asked for quotes on a 6.4 Kw BSL and a 5.1 Freedom Won. To my understanding they are both compatible with the Victron. Also C1 compliant not that i fully understand what that means.

Do they maybe say “1C”? If so, it seems to be a bit of a marketing gimmick. It means the battery can be discharged from 100% to 0% in an hour. Pylontechs typically are 0.5C, meaning the above in two hours. So the allowed rate of discharge on a Pylontech battery is lower. However, if you have a 3kVA inverter with 6kWh of battery, you really can’t discharge continuously at more than 0.5C, so 1C is pointless. Unless you want to get a smaller battery.

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Thank you Jacques at least i have a better understanding of the C value now.

As @jykenmynie said, it’s the discharge rate. A 1C battery means the entire capacity (hence the capital C) can be discharged in one hour. For comparison, a Lead Acid battery will be somewhere between C/5 and C/20 (discharged over 5- to 20 hours).

There are some quirks involved. The faster you discharge, the more energy is lost in heat and other inefficiencies, so your overal useful capacity becomes less. With Lithium, this is far less of an issue… BUT… most batteries do tend to heat up a little when you work them hard, and it is not good for them to be discharged that quickly.

With that theory aside… a 1C battery is one with a higher discharge rate than a 0.5C battery. But just because it CAN do it, doesn’t mean it is a good idea. And in any case, Victron Inverters are low frequency designs (except for Multi RS and Inverter RS), and they create a 100Hz DC ripple which becomes worse if the battery capacity is too low. For this reason, you will be told to install twice the capacity anyway, hence a 3kVA inverter requires 6kWh of battery, but you can usually get away with a minimum of 5kWh.

I prefer to build a battery out of multiple smaller modules rather than one large module. The reason for that is that the individual BMS components in each module (each rack mount unit) may disconnect that module if there is a problem (eg a high cell). If you have only one module in your system, that effectively disconnects the entire battery. If you have two or more modules, the remaining modules can continue operating, which means the system is more redundant, more stable.

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Understand and thank you for the explanation, i will get quotes for two 3 kw batteries and then do a vost comparison. As you said the redundency makes perfectly sense.

Thank you

Can you perhaps direct me to a sunsynk supplier in the east rand.