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Readers may recall the issues we have experienced with batteries in our caravan, in 2016 we replaced the original single 100 a/hr AGM (Absorbed Glass Mat) battery with two 120 a/hr batteries....we had hoped to be able to spend at least two days camping away from 240v power...sadly this never seemed to be the case. Running our Waeco freezer, the ocassional water pump useage and some interior lights and the 'lo voltage' warning buzzer would start after about 12 hours, if no sunlight was on our solar panels. I had a number of checks carried out on the system but no issues were found...the situation got worse as the batteries got older....after less than two years I decided to pull them out.
I have replaced the two AGM batteries with a single 100 a/hr Lithium Ion Phosphate battery, the latest in technology (In March 2020). I purchased this battery, and the 240v charger from AMPTRON in WA and cannot fault the pre and after sales service of this small company...I had a number of queries before I brought the gear and after installation.
Currently a lithium battery is around twice to three time the cost of an AGM battery but this can be expected to change as they become more popular, they are already around half the cost of what they were 2 years ago.
AMPTRON have a great email and phone service...the following is record of my lithium experience.
Test conducted March 16th 2020.
With the battery fully charged and sitting on float at 14.6v and with a SoC of 100% I turned off the 240vac charger. The rooftop solar panel is under cover and therefore did not come into play, I turned on the kitchen interior light and plugged in the Waeco, the Waeco was precooled and set on -10 degrees, it is 3/4 full of frozen items.
After 24 hours the battery SoC dropped to 59%, the voltage down to 13.3...the battery temp was 23 degrees, the ambient about the same.
It should be noted that the Waeco cycles on and off via its thermostat, when running it draws around 4 - 5 amps, the LED draws less that one amp, constantly.
Also worth noting that by now my previous AGM battery would have caused the Waeco to shut down due to low voltage....it would usually do so after about 10 hours.
After 48 hours the SoC was down to 20%, voltage 12.7v and battery temp 22 degrees....here we can see the difference with a lithium battery...a SoC of just 20% but still showing 12.7 volts.
At that point the freezer and light were turned off and the portable 100 w solar panels were connected.
The solar panel averaged around 4 - 5.5 amps,for the duration, it was full sun for about 97% of the test period, after 1 hour the SoC had increased to 67% and the voltage to 13.2v....battery temp remained as per ambient at 24 degrees.
After 2 hours the SoC was back to 100%, voltage at 13.3v, battery temp up slightly to 25 degrees.
At this point the solar panels were disconnected and the 30 amp Amptron charger turned on....charging amperage jumped to 29.6a and the voltage to 13.7, the cooling fan within the charger started to run.
One hour later and the charge rate was sitting on 30 amps, voltage to 13.8 and the battery temp had crept up to 40 degrees, about 15 degrees above ambient.
After 2.5 hours running on the charger it peaked at 29 amps and 14.9 v....at this point the charger went into float mode at .09 amps, the fan continued to run but the temp dropped quickly and the fan stopped about 15 minutes later.
And a follow up a few days later
...over the past couple of days I have allowed the battery to sit totally idle for 48 hours, when I turned the charger off the voltage displayed dropped from 14.9 to 13.5, over the 48 hours the SoC dropped to 97% and the voltage remained at a constant 13.5. When I reconnected the charger the charge rate went to 29.7 amps, the fan started and over the next 15 minutes the voltage came back up to 14.9 v the charge rate dropped to +.03 amps and the fan then stopped...with this in mind I possibly don't need to do much at all. The test I did last week where the SoC went down to 20% would be quite unusual.
If I did want to relocate the charger I had planned to move it outside and directly under the battery, this would not require any change to the wiring...I'd need to make a waterproof box however.
Caravans and lithium batteries.
This photo shows the difference between a regular deep cycle battery, commonly used in caravans, and the new lithium battery....the lithium battery is almost the same size but is about half the weight, having them the same size means they do not require any changes to the storing location....a modern lithium battery will have the controlling electronics built in, this also meand the size will be similar. I also purchased an AMPTROM solar input controller (on right) and a 240v battery charger.
The installation...as mentioned above, some noise comes from the cooling fan within the charger. and the additional vent panels I installed below.