Auxillary Battery. Comments & Opinions please

Batteries have slightly different chemistries and number one rule is to match these unless the batteries are truly independant.

This requires knowledge of how you plan to charge and discharge it.

E.G. Some batteries are just connected in parallel , others use a simple voltage based relay to connect the aux battery when charge is needed or may be switched together to winch - either of these scenarios are bad for dissimilar types.

Aux battery may by seperately monitored by a step up charge controller maxing say 15 amps or so and used only to power accessories - different types are less of an issue here.


Have used the Century Overlander as a good all rounder - as I prefer 1 big battery for simplify and low weight.

Change it regularly and now use the Exide Calcium/Calcium N70zzl which is stronger at 730 cca and fully sealed AGM in a petrol patrol.

I think whether a AGM is suitable would depend on your vehicle, where the second battery is in the engine compartment and how hot it gets and whether you can insulate it or cool it.
I am now on my third AGM in about 15 years , and the second latest lasted 5 years ( in My Range Rover Classic) and was only changed because I suspected it had lost some capacity.
AND in this time I drove the GRR< Kalumburu, Strz, Oodnadatta, And around the Gulf. Some rough roads there. My Supercharge Allrounder main battery died from internal short but the AGM had no problem.
I have just done the Cape with my current AGM , no problems.

The good thing about an AGM is that the energy density is fa rgreate rthan a similar size flooded cell. An N70 AGM is 90-100 AH whereas a Century N70 would be 70.

Now the Classic has a second battery tray next to the radiator which is a cool place and it gets some air in through the bonnet gap, along with the cats. if you have a battery tray up against the firewall next to the exhaust /turbo I would say forget it. As for corrugations I do not agree, although old Rangies do have a magic carpet ride, and AGMs may not like a Toyota ute.

Get an AGM and put in the rear, my personal experience is that you will get 1/2 the life under bonnet along with a crowded engine bay. I see you can get a 120 A/H Power Sonic off eBay delivered for $350. I have used Excide Orbitals, 2 1/2 years life under bonnet, 5 years in the rear. These are a great battery but only 50 A/H and expensive as they cost over $300 a piece.
Can anyone vouch for the Power Sonic?

Cheers

Lyndon

You might want to shop around. That Century battery (N70ZM) can be bought at half the price you were quoted:

No batteries like heat - it shortens their lifespan - but as for AGM's handling rough roads there is no problem.

You can pick up Fullriver 120's for around the $330 mark and people seem to be getting 5+ years from them.

mh