Construct

iTrader: (4)

Has anyone measured the battery current draw of an Evo VIII or IX with the car turned completely off and all of the doors closed?

My mini battery holds up fairly well for the most part. The only time it failed to start the car was when I forgot to connect the trickle charger prior to a 4-week trip out of the country. That still didn't seem right, so I decided to measure the current draw with the car turned completely off:

I put my meter in between the ground cable and the negative battery terminal. I began with a jumper across the meter terminals to prevent any inrush current from blowing the fuse in my meter, then pulled the jumper cable after a few seconds.

With the car off and all doors closed, the current draw jumped between 17mA and 19mA. That seems like a lot.

I pulled the yellow fuse holder up to disconnect the radio and dome light, and the current draw fell to 0.83mA, which seems perfectly reasonable.

Does the Mitsubishi OEM radio really draw 16-18mA when turned off? That seems high.

Construct

iTrader: (4)

Now that I think about it, I also have two ProSport gauges wired to the radio standby power line as well. Next time I pull the dash apart I'll have to measure the current draw of the individual gauges to make sure they're not the source of my relatively high standby current draw.

I'm still curious to hear if anyone else has measured the standby battery current draw in their cars.

josh_evo9

iTrader: (1)

I always thought that if it was under 50mA then it wasn't a problem. But I've never measured it

Construct

iTrader: (4)

Depends on your battery capacity and how long you leave the car sitting. Also, lead-acid batteries last longer when they aren't drained much (10% or so) during each discharge cycle.

My mini-battery has a capacity of 19Ah, which is 19,000mAh. Assuming 18mA draw, that leaves me with 44 days until the battery is fully discharged. But a fully discharged battery is useless to me, because I still need a lot of capacity to actually start the car, so my upper limit is probably half that.

Furthermore, lead-acid batteries last a lot longer when they're only cycled through about 10% of their capacity with each discharge cycle, so I'd like to keep my discharge within that range. 10% discharge happens in only 4.5 days, and that doesn't include the discharge from starting the car.

On the big OEM battery you can get away with a lot more abuse, of course. Unfortunately it looks like I'll just have to keep connecting my CTek charger whenever the car will be sitting more than a few days.

Jerry321

iTrader: (2)

It's it's over 20-25 ma it's too much parasitic batt. Draw. Make sure your leaving t multimeter on there to take the readings for at least 10 mins to me sure sure all the cars systems turn off. And also make sure all the cars doors are closed. If there still is higher draw start pulling fuses until it drops, if it drops when you pull a certain fuse there's the area you should look into.

Construct

iTrader: (4)

Thanks, but that's what I did. In fact, I said all of that in my first post.

Anyway, like I said I narrowed it down to the circuit with the OEM radio and two Prosport gauges by pulling fuses. I was hoping that someone else had measured the current draw of the OEM radio for comparison.

CkoTuHa

Dude, its the gauges. I put a relay that powers the circuit to gauges when the key is in ACC position. Now, my battery lasts a month easily.

Construct

iTrader: (4)

That's what I'm afraid of. I'll put my meter on it next time I have the dash apart to confirm.

The Prosport gauges pull standby power to handle memory retention, and unfortunately they default to having the annoying start-up and threshold buzzer turned on. If I don't keep standby power applied, they beep loudly for five seconds every time I start my car. Obnoxious. I wish that had just used a non-volatile part to store settings. Or alternatively, designed the gauges properly to minimize standby current draw (assuming they're the culprit).

CkoTuHa

You don't need to put a meter in series anywhere in vicinity of your dash, you could instead put it between the clamp and battery terminal. It is pretty easy to do. Like 10 minutes job:

Pop the hood, close all the doors, make sure no accessories are drawing any current
Loosen the nut securing the clamp to the terminal so that you can easily pull the clamp from the terminal
Arm the car if you have an alarm. Wait like 30 seconds-1 min, in case you have a cellular tracking feature in your alarm.

Now, put your meter to read current and stick it in series between battery and the car wiring. You can do so by connecting one probe to the battery terminal, and connecting the other probe to the car harness/clamp that you loosened, pull the clamp off the battery terminal so that all the current goes only through the meter.

There should be at most like 0.5Ah current. In fact, it should be less than 20mAh if your car is not sporting devices with excess parasitic current draw.

Observe the current draw. Put the clamp back on the battery terminal. Go to the fuse box inside the car and pull the fuse that powers on the accessories, as that thing powers the media system.

Measure the current again.

Disclaimer: You know, be safe, use your brain. Do it at your own risk, nobody is going to be liable, except yourself in case things go south. Common sense. Wear protective gear. At least some googles, just in case.


You will see for yourself that it is the freaking cheap gauges that draw the current. F their settings and the memory, just stuck some switch that powers them on/off or a relay.

Since you bought these cheapo gauges in first place, it is only reasonable to expect that you will have to live with the annoyances that those gauges come with. However, it is much more annoying to not be able to start the car imo.

Construct

iTrader: (4)

Thanks, but that's what I did already as I explained at the top of this thread.

A couple additions to your method:

Consider adding a jumper across your meter terminals when you first connect it to avoid blowing the fuse, then pull the jumper after a few seconds after the inrush current has subsided. I used the 440mA range on my meter for maximum resolution, but the inrush current when you first connect the battery can easily exceed that and blow the fuse. This probably doesn't matter if you're using a single-range meter with a 10A or 20A fuse, though.

Also, you've got your units mixed up:

Ah (amp-hours) is current times time. We're just measuring current here in amps or milliamps.

Also 0.5A would be a crazy high standby current draw. You can estimate battery run time by dividing your battery capacity (in Ah aka Amp-hours) divided by the current draw in amps. For example, if you have a 50 Amp-hour battery and 0.5A current draw, your battery would be 100% drained after 100 hours or four days. Realistically you don't want to be draining your battery more than about 10% each cycle to avoid the stress of a deep-discharge, so if your idle current draw was 0.5A you wouldn't want to leave your car unattended for more than 10 hours on a regular basis.

Did you read my opening post? My current draw is 17-18mA, which is still a bit on the high side for using such a small battery. In my third post I calculated draw-down times vs. my mini battery capacity. It's usable, but not ideal.

Anyway, I still haven't had time to pull the dash and measure the gauges separately. I'll report back when I do.

Grimgrak

iTrader: (3)

My car is a weekend car but it wont last thru a week of sitting, can't find solar panels big enough to combat the draw even 1amp capacity jumping from 16-20v goes to like .05amps when actually plugged into the cigarette lighter :P

Construct

iTrader: (4)

Are you on a small battery or the stock battery? Either way, you should at least be able to get a week of standby out of the car. Have you measured the current draw directly? You could just have a bad battery.

Solar panels have interesting current/voltage output curves. Each panel will produce maximum output power when the output voltage is held at the maximum power point, which varies from panel to panel. Your panel may have a 20V open-circuit voltage and a 18V (for example, random guess) maximum power point, but when forced down around 12-13V of your battery the current will fall off quite a bit.

Still, 50mA of charging current during the daylight hours should be enough to maintain your battery. That would, in theory, be enough to offset the 18mA draw I'm seeing as long as you live somewhere sunny. I'd look a little deeper and make sure you don't have something drawing a lot of idle power in your car. Either that, or you just need to buy a new battery.

Go_Lancer_Go

iTrader: (13)

lol @ "i explained it in the first post" "did you read my first post" rofl!!!!