Thread: 1 panel, 2 controllers ?

2 separate controllers will likely work but i would expect that the output would be halved which might make it under perform depending on the panel size and output.

Hi,
The crank battery is now 5 years old and of late, is not getting as much use as I would like. I occasionally charge it, but was looking for a way of keeping it charged up.
Jaycar have a solar trickle charger that should so the trick and is cheaper than getting a solar controller to wire in, so I will try that
Cheers

A 10w panel can be connected without a regulator.

Hi Austastar, how is your setup wired at the present.

If you can, simply parallel connect the lithium to the cranking battery and set the solar regulator to lithium charging.

This setup will keep your cranking battery fully charged and in top condition, without effecting the lithium battery's performance.

This setup will more than likely add a few years to the life span of your cranking battery.

Hi,
Li is charged via a controller giving alternator/battery source priority when engine is running, over solar panel on roof.
To hard wire the two batteries in parallel (presumably only while parked up for a while) would be possible, but a fair bit of work disassembling a working system.
I had thought of a trickle charger off 240V, mains or inverter, but extension cords are a hassle and the inverter is extra drain on the Li battery. And if the camper is not on the tray, the Li and inverter are some distance away.
Thanks for the idea though, I'll file it away for any future needs.
I'll post my findings on the Jaycar gadget in a week or so.
Cheers

You could leave the existing setup as is and just link the batteries via a Change-Over type relay, which is very similar to a standard headlight relay except the relay has both a Normally Open and a Normally Closed circuit.

You would use the Normally Closed-circuit to link the batteries together while the motor was off, and as soon as the ignition was turned on, the relay would turn on and disconnect the batteries, allowing your existing setup to operate as normal.

Again this would mean you only need the one solar regulator, set to charge the lithium battery but both batteries would be kept charged while the motor was not running.

NOTE this type of setup, where you connect the two batteries in parallel would not draw as much as 20 amps at a worst case situation, running from a fully charged Lithium to the flat cranking battery, and in the most part, once the batteries were fully charged, would only see about 150 to 200 milliamps flow continuously from the lithium to the cranking battery.

I have been using this type of setup, to maintain two different size AGMs ( 60 Ah and one 85Ah ) connected two two separate 100Ah lithium batteries, both lithium batteries separately charged off 25 watt solar panels via a basic solar regulator set to lithium battery charging cycles.

I have used this periodically for the last few years, and it has kept the two 4 year old AGMx fully charged and at maximum capacity.

Hi,
Hmm, I'm warming to your idea. I just happen to have a spare 12V relay and that would save faffing about storing the Jaycar gadget before driving off .
Yesterday's Li solar charging curve below is just for interest.
Many thanks for your input
Cheers

The chart clearly shows that your Lithium battery is fully charged and the regulator is set to a genuine lithium battery charging algorithm.

Note, if you use the setup I suggested, check the chart again both when you first connect the two batteries and then about a week later.

You should be able to determine from the chart, when both batteries are in a fully charged state.

Those BM2 Bluetooth Battery monitors should be used with every RV battery setup.