Boat Battery (not for motor starting)


Cool. I don't really feel authoritative enough to do a tut on it. I follow battery technology developments with a passion because it's fascinating, and basically driven by the need to develop the electric vehicle market, but I don't consider myself "clued up" on the subject... But I'll do a tut on installing a VSR (voltage sensitive relay). I have ordered some online but they will take time getting here. Basically, it's a relay that, installed in your 2 battery system, automates the charging of the secondary (house) battery. I currently have a manual switch and my memory is getting bad ;-)

Incidentally, there are some battery boosters that work entirely with ultracapacitors. They don't have their own internal battery, instead, using residual low voltage from your "dead" battery to load up a capacitor. This takes anything up to about 3 minutes, but if your battery is at say 10V, it could take as little as 10 seconds. It then provides enough energy from the ultracapacitor to start the car. Biggest benefit from capacitors is their charge and discharge rates... Instant compared to a normal lead acid battery. In time, I believe we will see much smaller batteries used in cars but in conjunction with supercapacitors purely for cranking power.


New member
Hi TKbaby

Most common size on the batteries are 100ah and 105ah.

Here you have a choice on going exide or Gel, but it will all depend on your budget. To keep things simple, the exide is "semi-deep cycle" and the Gel is "deep cycle". The "Semi deep" you will be able to discharge at 50% of the total ah rating and the Gel at 70-80%.

Summing this up in a nutshell
100ah on the "semi-deep" you will have 50ah of use.
100ah on the Gel you will have 70-80ah of use.

You also get the hybrid Gel which is a chameleon among these which are a mix between the exide and gel. You get them cheaper than true Gel batteries.

Batteries recommended are First national battery, Dixon and even Delco. With the AGM I will suggest the Omnipower.

With these batteries I would suggest getting a decent smart charger in the likes of Victron, C-tek or National luna. The great thing about these chargers are you can leave it on the battery when not in use as it will maintain the battery without overcharging it causing damage to the battery.

I hope this helps. This is just my simple opinion.

Good advice - my (pot bellied beer drinking flip flop wearing) experience don't go anything under 100Ah for marine purposes.