Dual Batteries or one single

[Cuppa]

At 12v 2x95Ah in parallel will give a total capacity of 190Ah (Amp hours, not amps).

If your batteries are 100% charged this will give you a useable capacity of about 100 AH, (less if you are drawing large currents from it). It is possible to use more, but if you take the batteries below 40/50% capacity you will be severely reducing their lifespan each time you do.

However as Drew says your alternator alone will not fully charge your batteries, it will only charge them to about 70% capacity, or 75 to 80% capacity for AGM’s.

Lets be generous & say you have new AGMs & that your alternator can get them to 80% capacity. This means you would have an effective total capacity of 152Ah. If you discharge them to 40% (of 190Ah/76Ah) this gives you a useable capacity of just 76Ah. (152Ah - 76Ah = 76Ah). So by following Drew’s advice & fitting a dc to dc charger & thus being able to fully charge your batteries you gain an extra 25% useable capacity, as well as ensuring that your batteries will have a much longer lifespan.

Ctek & Redarc both make good dc to dc chargers.