Re: Changed my Battery, increased MPG by 10%
 

^Probably because it seems like the alternator is overvolting, but the device is assuming the problem is with the alternator and not the battery holding a charge/simply being discharged?

I'm going to try to make it to this winter on the current battery. It's a silver DieHard 51; C2 code(not the 51R like I should have go figure), but it was from 2008 according to the sticker on the front. So, I'd imagine had I not killed it and not knowing what the previous owner did before purchasing the car at the end of 2009...perhaps it would have went another 2-3 years. Not a bad battery, but can't take abuse and live through it. I'm hoping the Mega Tron Interstate or perhaps an Optima can handle it.

BTW: Charged the battery for 13 hours at 12V 2A, now currently finishing off the charge at 12V 6A for another 2 hours.

Re: Changed my Battery, increased MPG by 10%
 

If anything is damaging the battery, it's that battery charger. You need to use a multi-step battery charger so you don't cook the battery plates. The chargers I listed keep the charge voltage constant while automatically varying the charging amps down to about 1 amp where from there it does a float charge at 13.5v.

Re: Changed my Battery, increased MPG by 10%
 

It figures that I'm finishing off the overall life of the battery, so that's why I'll be replacing it very soon. I suppose there is no need to do what I did just now again, but I went on the advice of my dad. He used the type of chargers you mentioned when he worked for Interstate Battery and serviced distributors. He used the term 'cook' the battery as well. I guess my method with this particular 'manual' charger(not really) is too aggressive and less user-controlled?

Re: Changed my Battery, increased MPG by 10%
 

The reason for that is that you likely have a 'dumb' charger while if you intend to preserve your battery, you need a 'smart' charger. The steps involved to use a 'dumb charger' in a 'smart' way would mean you'd be spending too much of your time trying to charge the battery yourself. Frankly, I think it's better money spent on a good battery charger that will double the life of this battery then to buy another battery and continue what you're doing. I've got a bank of batteries that are 10 years old that still work great primarily because they've been float charged their whole lives and so aren't sulfated like the car batteries we're talking about which do not receive such nice treatment. Assuming the lead plates haven't shed themselves and fallen to the bottom of the battery, the sulfation is the primary reason for diminished battery capacity. You can get rid of the sulfation either through this special liquid you put in each battery cell which I can't attest to or you can try a battery charger with a de-sulfate function which sends a 2-6mhz signal through the battery after it has charged the battery in order to break up the sulfate crystals so that you can utilize the battery again.

Re: Changed my Battery, increased MPG by 10%
 

I had my battery tested at a local Interstate Battery and it came back as 'marginal'.

Their device gave a printout. The battery; once the engine was shut off(from home this was a 6-7 mile drive), the battery tested at 13.4v, it was 95 degrees outside or so. The technician mentioned something about the temperature being 123 degrees or something to that effect, not sure if he meant the battery internally or the engine bay? Anyway, their printout said exposure to extreme heat or 21 degrees F or below could cause the battery to fail. I'm not sure if it matters, but he also mentioned that he entered the CCA into the device as 550, the battery registered 473 CCA. Does this mean it's alright? I believe this model 51 Die Hard came with 465, so it doesn't seem exactly right to me. Perhaps it's either Cranking amps or the number was randomly chosen based on the percentage of CCA vs the number it was given(86% remaining CCA from stock 550 = 473)???

Anyway, upon restart the alternator was shown putting back 14.1-14.2 or so, also testing via the device at the battery terminal. So...see if it makes it through the summer? Stock this car needs 410 CCA to start.