Issues with battery drain and draw

[ThomasE30]

So my e30 is modified and the electronics and everything is a bit of a shit show to say the least (rn the radio wiring is just wrapped in electrical tape and sound is coming out of only the driver speaker which was lazily put in door card, and volume will go in and put over bumps, needless to say I hate wiring). When I bought the car the PO installed a dual USB port that is connected to constant battery power at three little switches for “radio, main fuel and power, and then accessory, like the 3 different key positions, as well as a push to start button next to them where the factory cig lighter would be. If I don’t run the car once a day the battery dies and can’t start the car. I just recently replaced it with a brand new 650CCA from autozone. Could this be because there is a battery drain somewhere with all the electronics, or could it be the battery doesn’t have enough CCAs to power all the annoying useless electronics I need to remove? Right now there is a Amp in the back connected to the battery and then some shitty speakers and just lazily done audio wiring which I planned to take to an audio person to wire in my new JBL sub, and Polk speakers I got for free. Thanks for any help. The stupid push button start and switches will also be removed soon I just need to find the time to look at all the wiring under the console and how to wire it back so the key ignition starts the car. The PO is a very kinda guy and has already given me some of the old interior pieces that he had and would have no problem helping me out with those so hopefully that can be out of there soon.

[Vincenze]

You should disconnect the negative connector from the battery, set a multimeter to the 10A setting and connect the wires to its ground and 10A connectors. Close the doors and take out the light bulb from the trunk.
Then, measure the amperage between the battery and the negative connector.
It should be close to 0.035A.

You can set the multimeter to measure mV, and then measure the voltages between the two sides at the top of each fuse. Only the fuse #21 should have small voltage.

[ThomasE30]

You should disconnect the negative connector from the battery, set a multimeter to the 10A setting and connect the wires to its ground and 10A connectors. Close the doors and take out the light bulb from the trunk.
Then, measure the amperage between the battery and the negative connector.
It should be close to 0.035A.

You can set the multimeter to measure mV, and then measure the voltages between the two sides at the top of each fuse. Only the fuse #21 should have small voltage.

To measure the amperage between the battery and negative do I just attach the positive from multimeter to the positive battery and then negative to negative?
and when measuring the voltage on the fuses, should 21 be the only one with a reading or do you mean it should be the only one with a small voltage? Thank you again!

[Vincenze]

You should measure the amperage between the negative cable (or the car body) and the negative battery contact after disconnecting the negative cable.

Normally, there should be small voltage only on the fuse #21. It supplies constant power to electronics and lights. Everywhere else a multimeter must show 0 V.
But it'll work only if there are no unfused connections.
It's a quick way to find a fused circuit that consumes much power.

Or you can start disconnecting fuses one by one and check the amperage.
If there is still drain, then you have to start disconnecting all suspicious devices.

[ThomasE30]

Okay thank you so much. Hopefully it’s nothing big!

[reelizmpro]

I've found that he dome like/glovebox light/trunk lights are common causes of drains. Verify they are turning off with everything closed. There are also relays that can stay on and aftermarket accessories that hog power with the car off. In addition to what was said about testing for amperage draw check your battery size. Autozone designates a T6 battery as a suitble replacement for the E30 but I find they have less CCA's. They work fine in a mild climate but I'd get more amperage. You should be using an H6 group 48 battery with at least 700CCA. I think the AGM's even have 760CCA these days. You don't state where you are located but climate plays a major part. Also, I know I don't drive my E30's as often or as far these days so I keep mine on a tender.

[Vincenze]

A larger Group 49 battery fits into the trunk location.

Though, if a battery dies in 24 hours, it won't help much.

[Gregs///M]

To add, the SI board is also very ultra common to cause a drain, inside the cluster. Remove the SI board or pull fuse 10, 12 and 21 and you may notice the drain go away. If that is the case, you will need to have your SI board refurbished.

[Vincenze]

To add, the SI board is also very ultra common to cause a drain, inside the cluster. Remove the SI board or pull fuse 10, 12 and 21 and you may notice the drain go away. If that is the case, you will need to have your SI board refurbished.

How much does a good SI board consume?
Is it close to 0.030A?

Why do you replace the LDO LP2950CZ-5.0? It shouldn't cause drain if it's old unlike the capacitors.

[Gregs///M]

How much does a good SI board consume?
Is it close to 0.030A?

Why do you replace the LDO LP2950CZ-5.0? It shouldn't cause drain if it's old unlike the capacitors.

Milliamps, We sell only new or refurbished parts not "repaired" or "known working" parts. We replace the batteries, capacitors, transistors, and voltage regulators mainly because we have found them to fail, and they are 30+ years old. Dealing with screw and acid damage is a big one.

What occurs is that the transistors often get stuck, this is why you can get certain gauges / indicators to work when smacking on the dash. The most common is the SI inspection incandescent bulb in the SI LED panel, remains dimly illuminated with key out, barely visible to the naked eye. "Rebuilt" SI boards without new transistors will prematurely fail so watch out for those.

[Vincenze]

Milliamps,

I'm more interested in learning how to lower the energy consumption of the Instrument Panel plus the Service Indicator Board when they are in good working condition.
According to my measurements, they are the main source of the regular parasitic battery drain.

I guess nothing can be done. Probably, the chips consume too much energy in the sleep mode compared to modern microprocessors.

[ThomasE30]

I've found that he dome like/glovebox light/trunk lights are common causes of drains. Verify they are turning off with everything closed. There are also relays that can stay on and aftermarket accessories that hog power with the car off. In addition to what was said about testing for amperage draw check your battery size. Autozone designates a T6 battery as a suitble replacement for the E30 but I find they have less CCA's. They work fine in a mild climate but I'd get more amperage. You should be using an H6 group 48 battery with at least 700CCA. I think the AGM's even have 760CCA these days. You don't state where you are located but climate plays a major part. Also, I know I don't drive my E30's as often or as far these days so I keep mine on a tender.

I just started thinking about it being the dome lights, rn they’re pretty intermittent and it seems as if they work when you move them right so it could be it. I did replace the bulbs with led ones to see if they worked but still had an issue. I’m thinking it’s probably just some of the common e30 issues and probably because the amp is connected directly to the battery. Thank you everyone! Also I live in Virginia Beach, VA so it’s very temperate. Summers are very hot like now it’s humid and mid 90s, winters are cold and reach to like single digits rarely but snow is common, and then the in between seasons feel nice.

[Vincenze]

Why do you guess?

Disconnect the dome lights and measure the amperage.

[Vincenze]

Milliamps, We sell only new or refurbished parts not "repaired" or "known working" parts. We replace the batteries, capacitors, transistors, and voltage regulators mainly because we have found them to fail, and they are 30+ years old. Dealing with screw and acid damage is a big one.

What occurs is that the transistors often get stuck, this is why you can get certain gauges / indicators to work when smacking on the dash. The most common is the SI inspection incandescent bulb in the SI LED panel, remains dimly illuminated with key out, barely visible to the naked eye. "Rebuilt" SI boards without new transistors will prematurely fail so watch out for those.

I found this thread: https://s14net.vbulletin.net/forum/s...ry-drain/page2

It says that a reburbished SI board still drains 50mA, which is too much.

I got the SI board back from Greg. It looks as good as OEM! I installed it and everything worked. Car runs fine, all the gauges work, service indicator lights work and reset etc. BUT, my 50mA parasitic drain is still there.

[Gregs///M]

50ma does not sound right, I cannot say I am 100% confident that he ran the current draw test properly or that another circuit that is associated with the SI board is draining it, such as the OBC or the check panel system. There is no large drain to worry about after we refurbish the SI board.