Is this a big battery?

[melts]

scratching my head as to why this was overlooked, everyone got CCA - cold cranking amps, but no mention of RC - reserve capacity which is how many minutes it can deliver 25 amps before falling below 10.5v (or possibly 10.9v, but either way its the usual battery cutoff voltage)

so to convert it to A/hr just quickly, its RCx25/60, so this one is = 140x25/60. or 140x25 = 3500, then divided by 60 you get 58 A/hr.

as someone pointed though, running a non deep cycle battery that low will wreck it pretty quickly. I've used and abused marine combined deep cycle starting batteries for years and wish I had one for my current patrol. They last longer and are more robust to boot.

[DX grunt]

Thanks melts.

I bought my truck from a car yard and I'm thinking that they changed the battery. I really don't think Telstra would have put a cranking battery in as the 2nd battery, knowing it has to power lotsa stuff. Think I might have been 'ripped off', but I can't prove it, so I'm up for about $230 for a deep cycle one.

[the evil twin]

scratching my head as to why this was overlooked, everyone got CCA - cold cranking amps, but no mention of RC - reserve capacity which is how many minutes it can deliver 25 amps before falling below 10.5v (or possibly 10.9v, but either way its the usual battery cutoff voltage)

so to convert it to A/hr just quickly, its RCx25/60, so this one is = 140x25/60. or 140x25 = 3500, then divided by 60 you get 58 A/hr.

as someone pointed though, running a non deep cycle battery that low will wreck it pretty quickly. I've used and abused marine combined deep cycle starting batteries for years and wish I had one for my current patrol. They last longer and are more robust to boot.

Uuuummmm, have to disagree with you on that... your math is OK but the relationship is wrong

There is pretty much no specific correlation between RC and AH rating other than a rule of thumb that the Amp/Hour Capacity of a battery is better than 1/2 the RC or if going the other way the RC is approx 2 times the Amp/Hours.

The actual relationship varies dpending on battery construction and technology IE Wets V AGM V Calcium V Cranker V Marine V all rounder.

The reason being that the way the two "ratings" are determined is different. The rule of thumb I have always used for a wet cranker like Roscoes to get from RC to AH is RC rating divided by 2 add 15... which is how I pulled 85 Amp Hours outa my butt. Not saying its right but that will be close.

Have a quick Google if you wish here is one result From the University of Hawaii...

Many batteries today are rated in CCA or RC. CCA is Cold Cranking Amps. CCA is approximately equal to the RC of a battery times five. [1000 CCA is about 190 RC]. RC is Reserve Capacity. You can convert RC to amp/hours by the following formula:

Amp/Hours = (Reserve Capacity / 2) plus 16

[melts]

I see what you mean, but i've always used my maths with the marine deep cycle units and been happy with it, probably because it gives you a lower value than actual haha

Just wondering why testing RC is pretty well defined as fixed amp draw to volt x to give you a time as RC, as amp-hour is amount of amps y to reach voltage x by fixed time 1hr.
I know that as you draw power from a battery you have a curve to deal with, and batteries have a sweet spot for how much power you can take from them (usually amp-hours is based on a 20 hour draw rate for SLA batteries, for example, and drawing the same amp-hours faster from a SLA can be bad for it, and in some cases impossible)

actually, as interesting my train of thought there was (and why i've left it there) i think its got a lot to do with the nature of the discharge rate, and the RC test is generally harder on batteries than the loads people use on them, so amp-hour gives a better / more optimistic reading of how much power the battery can provide. I tried to find info on discharge rates and was promptly reminded of the curve you see with batteries and lead me to learning about the Peukert effect which explains the difference between amp-hours and RC.

the short of it, you'll only get 100% of your Amp-hours if you use it over 20 hours. you'll get 10% more if you use it over 100 hours, and 10% less if you use it in 8 hours. and so you can get from that you'll get even less using the RC rate, which is roughly around 2hrs for the battery posted.

so silly me i assumed it was linear over time, even though i knew SLAs suffer from the faster you take the less you get syndrome.

[growler2058]

WOW info overload for me hahahahahhahahahaha....... I need a drink

[the evil twin]

Gotta agree pretty much 100% with ya there, Melts.

Crankers are easy to suss out as CCA is pretty much God. It is Aux's where all the brainwork comes in. What are they running, how long for, duty cycles yadda yadda yadda... what suits one dude is hopeless for someone else. Is RC of more relevance than Capacity for what the individuals use the battery for.

Oh and Growlers... can't have too small a battery mate... the Beer might get warm. Hehehehe

[Cuppa]

Ross, have a look here.
I agree with him that the best reference is Collyn River's books. Very easy to read, all the info presented in a friendly manner. I know both Val (website) & Collyn personally & have 3 of Collyn's books.

FWIW - and there are always multiple opinions on batteries, I wouldn't be putting an AGM under the bonnet. It get's pretty hot under there. There are many good reasons for using AGM's but they don't like to get too hot. Stick with a wet battery under the bonnet.

Cuppa

[the evil twin]

Thanks melts.

I bought my truck from a car yard and I'm thinking that they changed the battery. I really don't think Telstra would have put a cranking battery in as the 2nd battery, knowing it has to power lotsa stuff. Think I might have been 'ripped off', but I can't prove it, so I'm up for about $230 for a deep cycle one.

FWIW - and there are always multiple opinions on batteries, I wouldn't be putting an AGM under the bonnet. It get's pretty hot under there. There are many good reasons for using AGM's but they don't like to get too hot. Stick with a wet battery under the bonnet.

Cuppa

Thats an NRMA (NSW) Roadside assist Battery they would have had lying around or whatever so don't read too much into it.

I totally agree with Cuppa... AGM's and hot engine bays are not an ideal mix. I would go an All Rounder or similar.

I am spec'ing up some Solar Powered Data Collection sites for work ATM and chatting to another engineer today (seems Thursday is Battery Day) who reckons the vast majority of sealed batteries die an early death because of electrolyte issues.

He was of the opinion that for general Automotive use good old open Wet Cells which you can check the levels and replenish electrolyte will last significantly longer than sealed valve regulated jobbies that all seem to fail 1 or 2 days after the warranty runs out.

[my third 256]

Thanks melts.

I bought my truck from a car yard and I'm thinking that they changed the battery. I really don't think Telstra would have put a cranking battery in as the 2nd battery, knowing it has to power lotsa stuff. Think I might have been 'ripped off', but I can't prove it, so I'm up for about $230 for a deep cycle one.

just purchaced one from local dealer i asked if he had any scratched ones or lables had fallen off /yes was the reply and only cost $150 instead of $230