Backyard Aquaponics
A place to discuss aquaponics

I have 240v power at my AP greenhouse... I was wondering if it is expensive/difficult to add the function of charging a solar/lithium battery system from 240v when the batteries get too low... would this be done through the BMS and does it mean a great deal of extra cost? as I see that a big cost is the batteries and to have the AP completely off grid would mean allowing for those very cloudy days/weeks by having a very expensive large battery bank... i fiigure I could always add batteries later?

240V (230V is the Aust standard since 2000) Lithium battery chargers are available- thats what all the DIY electric car people use.
The BMS doesn't handle the charging, it is a separate unit that gives warnings or disconnects when a cell or the whole battery is out of its safe voltage range. Each of the 16 cells in my system has its own module that tells the BMS that things are ok or not. The cell module also drains away some current to stop the cell from going over voltage if it is running a higher voltage that other cells in the battery. If any one cell goes out of range, there is an initial warning for some things, but then the battery bank is isolated, meaning there is no load on it and no charge going in. However, the BMS should only ever be the backup disconnect- other means must be used first, and this is where some systems probably fail- there is no backup plan! The battery has a 160A fuse on it ATM to protect against short circuits, and I also have fuses between cell pairs which I run in my 24V system, to protect against a cell discharging into its twin due to an internal short circuit.

My inverter disconnects at 24V, well above where the BMS will do a low voltage disconnect. Afer years of monitoring I am fairly sure that my 3 MPPT charge controllers wont go on overvoltage excursions (unless I do something silly with the settings!), but do plan to use a spare channel on my relay driver to cut charging if the battery does go overvoltage. The BMS is only the backup for when all else fails.

Yeah bilge pumps suck! An autopsy of my dead one is here:
viewtopic.php?f=8&t=1409&start=645

The brushless pump I bought was off ebay, roughly similar to this one:
http://www.ebay.com.au/itm/1300L-H-12V- ... 3f1865183f

Good luck with your build

Make sure you add a fuse from the battery.
That will stop most battery fires. Li, Pb, NiMh, generally fire is from excess current draw from a short somewhere.

BYAP have a solar system too.

viewtopic.php?f=51&t=13060&hilit=solar