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Batteries ......where to start?

Triggertrevor

New Member
Joined
May 30, 2020
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Hi all this is only my second post on the forum so sorry if i post in the wrong area.

I have been interested in adding a battery bank to my current 4.5kwh solar home setup for some time now but prices of ready made battery banks have put me off so far.
So i would like to build my own with help from a friend who's a electrician. I would like to ask for advise on a battery bank sized from 7kwh-14kwh,i have looked at going the 18650 or the Lifepo4.
pros and cons on both systems would be greatly am thinking of using sofars ME3000sp ac battery inverter as my dc inverter is from sofar so id have continuity and i'd also like to charge the batteries from the grid in the winter months.

Hope ive provided enough info.

Many thanks Kev
 
Welcome Kev,

Here's a Video which you should watch. It is an eye opener.

The truly simplest method is to build your own LFP (LiFePo4) battery bank.
For 24VDC system, it requires 8 LFP cells to make a Pack. For 48VDC you require 16 cells to make a Pack.
You can set more packs into place to increase the overall Amp Hours & kWh of the entire battery bank.
With LFP you can add packs in Parallel over time to increase your storage capacity. Each pack is an independent creature as such and do not suffer issues like other chemistries.
Not all Inverters / Chargers directly support LFP or even Lithium in general. All Tier-1 products do, most Tier-2 products but rarely do "Value or Tier-3 "Value" products (that is changing though).

There is a WIDE Assortment of different types of equipment, from All-In-Ones (Solar Controller, Inverter & Charger all in one unit), to "Families" of gear which interconnect & use common management interfaces, to Separate & Independent components. Many here use EPEver, MPP-Solar & Growatt for the "value but good quality" gear or we step up to pure Victron Solutions which are quite good Tier-1 product (but more $$), Some of us like myself use a mix of Tier-1 product, as I use Midnite Solar Classic Solar Charge Controller and Samlex EVO Inverter/Charger. NOTE IF I was building from scratch today, I'd go all Victron, was not an option when I went off-grid solar.

The most typical configuration is to install the battery cells in Series within the pack, add one BMS (Battery Management System) and drop it all in a box/case and your done. A BMS can be a simpler device with the important basics to more advanced manageable, configurable & monitorable. Of course prices reflect the options & capabilities.

A quick example for a 24V Pack.
8x 280AH Cells Total US $1,093.52 including Shipping & Handling to USA.
1x Smart BMS $75-$150 (there are many choices & options)
1x MRBF Fuse with appropriate fuse size.
1x BOX / Container for cells.

24VDC - 8S "Block Format" pack
8S-24V-Square Pack.jpg

AH to kWh quick ref:
- 100AH @ 24VDC = 2.4 kWh
- 100AH @ 48VDC = 4.8 kWh
- 280AH @ 24VDC = 6.72 kWh
- 280AH @ 48VDC = 13.44 kWh


REFS:
Xuba Electronics "EVE LF-280AH Cells"
https://www.alibaba.com/product-detail/Hot-Rechargeable-3-2V-280Ah-LiFePO4_62401469185.html?
DALY 80-250A Smarter BMS: LINK to Smart BMS Store FORUM THREAD HERE: New-daly-smart-bms-w-communication-80-250a
Blue Sea MRBF Fuses: https://baymarinesupply.com/mrbf-fuse.html

Hope that helps get you going somewhat.
Good Luck
Steve
 
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