like mentioned above, standard car batteries are designed for high-amp short duration loads when fully charged. if you fully discharge a battery, you halve it's lifespan and the effect is cumulative. same for long duration small amp draws. That's what deep cycle batteries are for...not so good with the sudden amps to start the car but run lights, sound, TV, etc forever to a low charge and it doesn't mind too much

Hi,
The SuperMID consumes only 0.15A, approx 2W, less than one of small tail lamps(5W).

Yoshi

You can use your SuperMID to tell if your battery is getting low and your alternator is having to work to charge it. If you know what your usual injector pulse widths are when idling a warm engine, if your pulse widths are larger than normal, it is working to charge the battery. On my car the idle pulse widths are very sensitive to the alternator load and only takes a few seconds to show the effects of the lights or fan being turned on/off. If I do a normal warm engine start (2 or 3 turns to start), it has recharged the battery and the pulse widths drop back to normal within 15 sec.

Thank you Basjoos for your Tip. Looks like Supermid can indirectly sense many things.

THank you Yoshi for giving the Power consumption for Supermid.

Regards

CWA

It's more like bajoos is doing the sensing :)

Yes, I did have trouble with a battery when I was hypermileing... at night... with the headlights, heat and fan on... and oh, yeah, it was 6-7 years old and the cheapest of the cheap when new. The advise to run a deep cycle in parallel is a good one, before my car was killed (hit and run) I tracked down a good deep cycle marine battery through craigs list, $5. Don't write off hypermileing, people always want to know what mods they need to make expecting to hear about some new wing or magnet-hydrogen-displaced with bovine excrement modification... but its usually as simple as an upgraded battery, or something along that line.

Just keep learning, your on the right track.

Another thing you can do is get a trickle charger and plug it in at night. This will make sure your battery is topped off and ready to go the next day. As others have mentioned batteries, particularly lead acids don't like to sit on a partial charge. The longer they sit not fully charged the more sulfur builds up on the plates which reduces the capacity of the battery. I trickle charge mine at least once a week. Usually the TDI is right up there and shuts off right away, but our Sienna van charges for about an hour before being fully charged.

As a side benefit the alternator will work less and your starter will turn over easier on a full charge and be more likely to start since the motor will be spinning faster.

Something else to look into, and I mention it because I just did some work with it with good results, is engine grounding. It depends greatly on the make, model, and engine but often adding a ground wire or two can help older cars. sometimes just taking the ground wire off and hitting it with a bit of sandpaper and cleaning the battery terminals will solve seemingly horrible electrical problems.

In my case, I've got a 1990 toyota cressida, an in-line 6 mounted RWD so the engine and transmission together are about 5-6' long. It's also iron block, aluminum head. the last several times I've taken the engine out (yes, I'm like that) it seems I've replaced fewer and fewer of the small ground straps till I had one 18ga and the main 6ga ground. The other day I ran a 4ga wire from the head to the strut mount on one side and the battery ground on the other side. and viola, my electric-read oil pressure gauge started working again...hasn't since the last time the engine was out and I've been too lazy to dig in. I've heard of other cars benefitting from similar treatment but most are older ones that may have dirty ground points

Electrical items need to operate at a specific voltage too.

If you take a light that is supposed to run on 12vdc, and you operate it at 11vdc, you will generate more heat and reduce the life of that item. I'm not an electrical engineer, so one would have to go look up all the electrical information for that, but it will affect lights, motors, ignitions, etc.

Was the battery load tested before being replaced?

yup i will contest to that. im my chevette i had to take off an existing ground to add another ground for its alarm system and noticed that whoever repainted the car never scrapped the paint off before they put the grounds back on! so what i did was get a drill with a wire brush in the end and went to town till they were all shiney. cars lights are alot brighterand seems to run smoother. i did it to my trucks grounds and didnt see too much of an imrovement it cant hurt anything it can only help!:thumbup: