What's possibly more important is the process I went through in selection
, this takes into account the application/purpose of the installation, the physical and electrical 'environment' it's being installed into as well as overall cost, weight and capacity for future re-configuring. It's worth noting that I'm a retired technician who worked in a low voltage, high current battery environment for many years so I tend to 'over cook the goose' somewhat when dimensioning and building my own stuff
In my case the application/purpose of the installation was to upgrade the existing house battery in our Oka mobile home. The original 4 X 66 ah Optimas were now up to 7+ years old (from memory) and even though they were still at 90+% my justification was that they were approaching end of life so needed replacing. That was an excuse really as I was just itching to have a play with LiFePO4
The basic electrical environment in the Oka is a bit different to most 4WD's. From factory it has two 100 ah lead acid batterys, one is a dedicated start battery, the other does everything else. In my case add to this a lead acid house battery of 130+ ah. Vehicle battery coupling is by alternator W+ activated solenoid with a generic Bosch 1485 alternator and 440 watts of solar with separate solar reg. It's worth noting that solar is the primary charging source for the house battery with alternator fed DC-DC convertor as a backup and that the
only load on the house battery is an Everkool 145 litre fridge/freezer. The vehicle mounted winch is powered by the two lead acid vehicle batterys and
not the house battery. With cable lengths and layout the set up is similar to a 4WD towing a camper trailer.
The physical layout is cabin roof mounted solar of 320 watt being upgraded to 440 watt in conjunction with the battery upgrade, one vehicle battery located just behind each front wheel and the house battery relocated from approx. 300 mm behind the drivers seat to above the drivers side rear wheel.
I figured 200 ah of LiFePO4 was about right for what I wanted, though I found it weird to dimension a system that uses more than 50% SOC from the battery which is something I've never done before as I've mainly dealt with lead acid batterys and is probably why I got such good life out of my Optimas
There's good reason with LiFePO4's to have as few cells in the battery as possible so normally a single 200 ah battery would have been my choice but instead I went for 2 X 100 ah batterys so that I could go 24 volt if required. The advantages of 24 volt efficiency wise is significant, especially in high current (>100 amp) applications and cabling costs/size/power loss is reduced for the same outcome. This isn't something that's an issue now but I wanted this option for 'down the track'.
This may seem a bit of
waffle or making it harder than it needs to be but I told you I tend to overcook the goose
. Anyway, from this I was in the market for 2 X 100 ah LiFePO4 batterys with the capability of being series connected to make 24 volts (not all LiFePO4's have this capability). As Tim points out it's worth reading the specs, '
the devil is in the detail' and even if it's hard to comprehend comparisons can be made between batterys. More is always better
.
I went with a supplier I'd bought from previously and who has been around for many years. My batterys are the same brand and capacity and similar spec as these but are now a superseded item and
NOT the same.
Solarking 12V 100ah Lithium Battery -11KG- Active Cell Balancing - FREE FREIGHT | eBay
They also offered a five year warranty and had a 'smoking good deal' via eBay at the time. I bought two for the same price as one of these
and consider them to be a 'middle of the road' choice.
IMO the battery's that Tim was offering at the time were a much better battery and better suited to a
proper installation, but for a
fiddler like me with low power/current requirements these do the job.
At the end of the day you get what you pay for, only time will tell if I made the right choice
.
The end result (Mark.1)
House battery(s) on left, AEG charger for chainsaw battery, 500 watt inverter and leads etc on the bottom. HF main unit and Milwaukee charger at rear. Votronic MPPT reg and DC-DC charger (both with LiFePO4 profiles) on right.
The power distribution panel is mirror imaged left to right with house battery(lithium) on the left and main vehicle (alternator) on the right.
Deano
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