silverbullet wrote: ↑11 Jun 2025, 06:32
I have recently bought a 110L AGM for the white shed on wheels, they also need a smart charger that can deliver 14.8v, usually the "winter" setting.
Will probably add a simple solar array but the main draw will be running the blown air heater over a chilly weekend in spring or autumn so might not even need it.
Rather than spend a lot of money on a smart dc-dc charger just to do a balancing charge on an AGM now and again, if you use a dual sensing split charge relay (ideally a Cyrix-ct, £40) that'll keep the cost and complexity down.
Instead, rely on the solar charger to push them to 14.8V.
This way you'll also have the benefit of the solar panel keeping the starter battery charged, and a "boost" function which manually ties the batteries together so you can jump start off your leisure battery if required, just by pressing a switch.
AGM don't really need to be charged to 14.8V
every time, the 14.2 ish you'll get out of your alternator will charge them up to 99% of their total capacity. Holding them at 14.8V for 30-60 minutes every 5-10 cycles to balance the cells is probably healthier for them than doing that every time, and a decent solar charger (again, Victron - Smartsolar, £55) will do this only when required.
A few other benefits of doing it this way is the Solar charger has temperature/voltage compensation to keep the equalisation voltage at the optimum, and they have a 15A switched load output with current sensing, allowing you to see how much power you're using and also automatically shut off the load to protect the battery if the voltage gets a bit low.
(im not knocking their use. I'm considering getting one myself)
