Wednesday, Apr 23, 2008 at 10:36
Mainey,
I been research battery topic for quite a while and experimenting with different set-ups before I have came to what I use now.
There is no such thing as “specially design cranking” battery. Starting battery in fact no more then bastardized cheap version of “normal” lead-acid batteries known as “deep cycle” one. To achieve more cranking amps and reduce cost they develop thinner plates, thus they can pack more of them in the same space achieving more amps because amps directly related to surface of plates. To make plates thinner (and cheaper) they drastically reduced usage of lead in plates, but instead use specially developed paste. It is true that “cranking” batteries produce more amps for the same size of battery (remember – more plates = more amps) and they are cheaper and smaller for CCA given, but we have to pay for this. Such batteries have two main disadvantages that in my eyes make them absolutely useless for 4WD applications. First they not tolerant at all to deep discharge – if such thing happens paste get detached and fall to bottom ultimately making short circuit and killing battery. It is not even necessarily to all banks fail to make battery useless – one fail and it is dead. On this fact alone I would not use cranking battery in winch application. Second fact also related to usage of this paste – such batteries not like shaking much – again paste gets detached and it doomed. Therefore in my opinion such batteries only good for suburban cars.
There is nothing wrong in usage of deep cycle batteries for starting. They pump slightly less amps *FOR THE SAME SIZE*, because they use lesser and much thicker plates made from lead (less plates = less amps). Answer is simple – install upsize battery. Or even better two of them running in parallel. I do not use “cranking” battery even in my passenger car – have bigger sized deep cycle one. Yes, it is more expensive, but in long term it pays itself by much longer life and heck, I do not pollute our land with unnecessarily big numbers of used batteries. Also they much more robust and easier tolerate abuse.
I can accept that my setup is not for everyone - some have amnesia for example. So when I will eventually develop one, I probably will install an isolator. As for my method of charging fridge battery – probably it is a bit more expensive, but it does not suffer from voltage dropping and with proper setup guaranteed to charge supplemental battery fully even if it totally different kind of. Plus supplemental battery can be installed in cargo area (or even better can be made easy movable with fridge) without necessity to run thick expensive and potentially hazardous cable and without any negative consequences.
Also it is possible to figure out how much AH left over pretty accurately by using high-precision voltmeter and take into consideration battery temperature.
Cheers
Serg
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