What battery(s) I should get, and charge?

Allan B (Member, SunCoast) replied:

Hi Shane, I thought it was universally agreed that putting AGM batteries under the bonnet was perilous, although some do it and get away with it.

For my own part, I have prematurely destroyed a couple of flooded deep-cycle batteries in the engine bay even though they were away from the exhaust. It is possible that charging regimes may have played a part.

So now I have fitted an AGM in the engine bay with a heat shield and good cool air flow so we will see how that goes. At the same time I fitted an identical AGM in the cabin and each is charged via an Redarc DC to DC charger from the alternator which cares better for the batteries than brute-force charging. Time will tell if this is an improved setup.

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The Bantam replied:

Personally I think while AGM is a great technology and there are some very nice batteries out there, BUT it is oversold particularly in non-marine applications.

Likewise I believe deep cycle is often specified without a good understanding of its strengths and weakness.

a combination of both will often fail without people undertsanding why.

Many Deep cycle AGMs have very low maximum initial charge rates.
I have seen reputable N70 size batteries with maximum charge rates of 20 amps, people also fail to look at the recommended temperature ranges on AGM batteries..some quoted as low as 45C in charging cycles.
Put one of these under the bonnet connected by a simple solenoid and you have a guaranteed failure.

Deep cycle batteries are no mirricle and realy are strong where they are charged and discharged slowly.
Cycle them hard every day and you are realy more into a cyclic application rather than a deep cycle application.

personally after a great amount of thaught and looking at the specs and the prices I have standardised on good quality sealed marine cranking battery for all applications.

I can buy twice as much capacity in standard sealed wet marine batteries as I could in AGM, and that is a game changer.

Double the capacity you halve the drian on each battery making it perform better and give more capacity, for the same load and duration you cycle half as deep, that will extend the life of the battery no end.

Personally I like the Supercharge Seamaster Gold, because I have had a good trot with Supercharge..and although a "sealed" battery, once out of warranty, the top sticker can be removed and the vent valves unscrew and the battery can be topped up just like a basic screw top battery.

so my recoendation for what it is worth is go with as many N70 sized marine batteries as fits your need.

If you are going to paralell 2 up for more capacty make sure you buy them at the same time and periodiclay charge them seperately.

Oh and a good multistage charger is a great investment, but there is no need to leave a battery on them all the time..a good heathy battey should hold its charge if treated right for 2 months if leaft in peace.

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Member - Shane D (QLD) replied:

Thanks for the replies,

Shane Thumbs UpThanks 0