I'm pretty pleased with my Painless set-up. No delicate electronics to get damaged by heat, dust, vibration...
Disagree, Ash. Having a separate back up has saved my butt a couple times miles from anywhere.I just miss the dual alternator set-up I had on the 2F. Now that was real redundancy.
That's because you had a crappy battery.

If you have a good quality battery with killer specs and a decent electrical system, a single battery with the following spec is plenty sufficient.
For a cost of $250, you're getting a battery that has better specs and a warranty than two POS Optima Yellow tops and cash to spare.
DieHard Marine Battery, Platinum PM-1 - Group Size 31M
Product Overview:
Item Weight: 75.0 lbs.
Battery Type:
Transportation Type: Marine and recreational vehicle
Battery Group Size: 31M
Temperate Zone: North or South
Power Configuration:
Voltage: 12.0
Power Ratings:
Cold Cranking Amps (CCA at 0 deg.F):
1150
Reserve Capacity (RC):
205 min.
Amp Hours at 20 Hour Rate:
100
Design & Construction:
Container Material: Polycarbonate/polyester
Warranties & Coverage:
Months in Use Free Replacement: 36
Dimensions:
Height: 9-1/2 in.
Width: 6-4/5 in.
Length: 13 in.
If you want to spend more money on even a better battery, then get the real deal
PC2150 S and PC2150 T - Odyssey batteries
* PHCA: 2,150A at 80°F (27°C); for 5 seconds
* PCCA: 1,500A at 0°F (-18°C); for 5 seconds
* CCA:
1,090A at 0°F (-18°C)
* CA/MCA: 1,370A at 32° (0°C)
* HCA: 1,545 at 80°F (27°C)
* Reserve capacity:
205 minutes on 25amps <<<<<<< pay attention to this one!

* Short circuit current:
5,000A
* Deep cycling capability: 400 at 80% DOD
* Design life: 12 years
* Typical service life: 6 to 8 years
Isn't it a coincidence that both batteries have a reserve capacity of 205 min?

I wonder if they're both identical batteries but with a different casing......