Leisure battery

Anyone know if it would be worth trying an AGM leisure battery in my cruising cabin or sticking with a wet battery, I only off grid? Thanks

Hello Di Bingles.

Here’s a ‘yes’, ‘no’, ‘maybe’ answer.

An AGM is still a wet battery in my book. The difference between an AGM and a standard / deep cycle ‘leisure’ is in the material between the plates.

Here’s a great video that shows the main types of lead batteries:
https://www.youtube.com/watch?v=e_May8MXy14

I think you can have AGM standard (cranking) and AGM (leisure or deep cycle) batteries.
The thing to bear in mind is that a standard lead battery can only be discharged to about 50% of full before it will suffer (and sulphate) when recharging and its life is shortened. The more it’s discharged the shorter its life will be. Deep cycle or leisure batteries can take a bit deeper discharge and will recover more fully on each cycle and I think AGM deep cycle batteries are about the best, but I don’t think they can be discharged much below 50% or 12.1V.

If you’re regularly going off grid, the parallel question to ask is can my solar (or other charge options) keep my leisure battery above ~50% (12.1V) at least much of the time. I think if the answer is not, then you need bigger battery capacity, more solar (or more other charge capacity) or lower discharge consumers / consumption.

One way to add ‘better’ battery capacity is to use lithium batteries, which have an almost 100% useable battery capacity. The caveat here is that lithium batteries do lose capacity if regularly discharged below ~20%, charged above 80%, overcharged or charged rapidly. They also don’t like being charged if it’s <0C, just ask an EV owner; (in coming year the drop in capacity will likely be more important than the mileage of vehicles).

Lithium is also more fussy in the way it’s charged and is more expensive but it has more useable energy density and they are lighter.

So if you’re swapping a cheap deep cycle battery for an AGM one you’ll still be mostly limited to ~50% discharge but the AGM will likely be a bit more forgiving of being discharged. The AGM should last longer, but it’ll cost more.

If you’re contemplating wider changes to the leisure electrics do think lithium, would be my suggestion.

HTH !!