AGM doesn't like heat
I need a starting battery ASAP for my 2014 D4.
I sometimes tow a off road van (1840 kg up to 2500kg with water etc.). The van has two 252 w solar panels and two 120 AG AGM batteries. Due to the electronics in the van, getting a proper charge to Lithiums batteries was not possible. Also I was not able to easily squeeze in bigger deep cycle batteries, plus the sweet spot for caravan deep cycle batteries is either 105 AH or 120 AH. In most cases ... but I read a l ot of stats on batteries. Their characteristics vary a lot. Some take charge quicker (Lithium iron by far quicker, then AGM, Gel is slowest of typical lead acid batteries but for deep cycle they are able to take much more of their capacity with less van use due to slower charging but more critically they cost a lot more than AGMs), some are sensitive to heat (most AGM warranties are qualified not to in the engine bay), and the stats on their capacity is often marketing claims than reality, plus the construction materials vary a lot. Also retailers get differing wholesale prices on batteries, typically with deals or ownership which steers them to sell limited brands in order to be competitive. Plus the wholesalers vary the prices with specials etc IMO and hence one has to be lucky with a start battery good buy if one decides on one particular battery.
The statement made about weight is correct. It points to the overall capacity of the battery. However deep cycle batteries are quite different to the requirements for high short term power for a starting battery. The AGM that does both though is still the cylindrical Optima batteries. Interestingly the Optima batteries understate their capacity - one has to read their stats to realise their capacity in AH is much greater than they claim. One needs to measure them on the weight basis. Their feature though is that due to the varying thickness of their wound cylindrical AGM design, they can crank well, but they can also tolerate lots of discharge. A decade or so ago they were used in electric vehicle development, although a major reason for that was they can re-charge very quickly.
The plate design of AGM with fibreglass holding the acid, does mean that with a thin layers of glass heat might cause an AGM to vent through its valve some gas, and hence, many AGMs are not suitable for engine bay use. I think that if an AGM has thicker glass then that would make it less likely to be effected by heat ... but the warranty would be the key I guess.
For me, I will look at good AGM brand that will work in the hot engine bay (warranty should indicate that), and also its tolerance for running my fridge in the back (and I have a 2nd battery already which is a yellow top Optima).
My thinking at the moment is that if I go for an AGM, because the fibreglass holds the battery plates firmly and hence they handle rough roads better - but it must be heat tolerant. Evidently the case material effects that heat issue to. Due to the 2nd battery which can also assist in cranking the battery then I am not so dependent IMO on cranking power. A lot of top AGMs seem now designed for restarting motors when one stops the vehicle, which my 2014 D4 doesn't suffer from. I would have liked to get another yellow top (as one is the 2nd battery) - bbut the height for the D4 compartment is too low for a decent sized Optima yellow top. Darn. I do wonder if a Lithium might do the job too.
Incidentally for my deep cycles AGMs for the van I bought two Full River batteries 120 AHs, and while most 120AH batteries weighed 32 or so kg, the Full Rivers weighed 36.5 kg although I have not weighed them! It's one thing to claim 36.5 kg or whatever - with marketing these days its best to actually weigh them. As is its best not to trust many of the claims battery makers make. And the construction quality, the materials used, the purity of the lead used, the design of the bridges between the plates - those things are all compromised if a maker is chasing price. The Full Rivers cost more but are well made, and many are sold in Australia which means they are well priced in Australia and worth their extra cost IMO.
My wife's grandfather worked at Varta - but they seem expensive al right!! The Delkor LN5 though seems a very good fit for the space available.
2014 HSE White;Tint; Windsor Lthr; 18" Compo & 265/65/18; ARB-Summit B Bar, roof racks, ARB air, Bush’r 9" spots, Llams Traxide & Yellow Top, Ritter T Bar Air jack Max Traxs, Redarc TowPro, GME Uhf, Autofridge sat phone, AOR Matrix V3 off road van
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