Whilst driving home from my recent camper trailer snagging trip I considered the battery replacement issue. The 'dead' 150Ah slim line AGM battery had been carefully mounted by me in a secure and sealed custom made case under the rear of the trailer. The first two consideration were; should I replace it with another slimline AGM battery or opt for a slimline Lithium battery?
My electrical demand is rather modest. The combined load for the fridge and freezer is less than 6 Amps. Added to that is a small amount of LED lighting and the very infrequent use of the 500W 240V inverter.
When not moving, the single 150W solar panel provides sufficient energy to meet the requirements to power the fridge and freezer. Assuming the panel can produce a max of 10 Amps and there are 15 hours of daylight then the production would be 150Ah. This is probably optimistic. Assuming the fridge/freezer consumes 6 Amps for 24 hours then the load is 144Ah. Of course the fridge and freezer don't run continuously so the consumption will be less. Assume the consumption is 100Ah.
It's only possible to use 50% of an AGM battery before damaging it. This means the old battery had 75Ah available. This is insufficient if I was to rely on the solar panel.
Lithium batteries can provide 80% of their rated capacity. Well they can provide 100%, but this significantly reduces the number of life cycles. It stick with 80%. Therefore, for the 24hr load of 100Ah a replacement Lithium battery would require a minimum capacity of 125Ah.
The price of Lithium batteries is slowly reducing. A good quality 100Ah lithium battery costs approximately $1500 and the budget end around $4-500. You get what you play for and if it was essential for me to have a very reliable battery system (ie, continuous cruiser) I'd opt for a more expensive quality battery. However the camper trailer doesn't fall into that category and a budget battery should suffice.
There are three essential criteria with lithium battery construction
- Quality of the assembly/construction
- Quality of the lithium cells (some manufacturers use second hand or second quality cells
- Quality of the inbuilt Battery Management System (BMS). A poor BMS can result in cell imbalance leading to premature battery failure.
I'm not going void a warranty by tearing apart a newly purchased lithium battery to inspect the quality of construction. Instead I will read the results of others who have done this already.
An initial search revealed Aldi has a 'VoltX' brand lithium 100Ah battery on sale this weekend for $449. Purchasing an Aldi 'Special Buy' in Perth is very "hit and miss". We're on the other side of the continent and often the special Buys aren't in stock.
Another option was a battery from iTechWorld. They are a local, Perth company who design and develop lithium batteries. Note they don't state 'manufacture'. No doubt their batteries are made in China.
I've previously purchase a number of camping items from the 4WD Supacentre chain of stores. they specialize in budget priced 4WD and camping equipment made in China. Their website stated they had a current special on many items; including lithium batteries.
I could purchase a slimline lithium battery from the 4WD Supacentre and fit it into the old AGM battery compartment under the trailer. That's when I realised it wasn't necessary to fit the replacement battery under the trailer. If I purchased a lithium battery it would be lighter than the old AGM which would enable me to more easily move it around. When I was going on a trip without the trailer I could place the battery in the rear of the 4WD, along with the fridge. I'd need to make a battery box, but that wouldn't be too hard. Then I realised the 4WD SupaCentre had a special on battery boxes. They were selling them cheaper than I could purchase the components.
Off to the local 4WD SupaCentre
Our new 120Ah lithium battery
The battery box
Internal 30A fuse.
Isolation switch, voltage meter and red 10A reset button.
On the opposite side is a 12V cigarette socket and two usb charging ports
On the top are two Anderson Plugs
I fitted the battery inside the case noticing there was a gap on the side and end. The last thing I want is the battery bouncing around inside the box and I fitted some packing to eliminate that from occurring.
Then the cables were connected to the battery terminals and the lid fitted.
The voltage meter was showing 13.2V which indicated the battery was approximately 70% charged.
Accordingly to the battery specifications the maximum charging current is 60 Amps. But the fuse in the box is rated at 30 Amps. I elected to be cautious and used our 240V charger which has a maximum output of 15 Amps.
Whilst the battery was on charge I made a start on modifications to the trailer .
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