Issues with battery drain and draw

[Gregs///M]

When I disconnected the instrument panel, the amperage was 30mA lower.
When I disconnected the clock, the dong, the check panel, the difference was 2mA or so.

I think it's a good idea to cut the wire that goes from the fuse 21 to the instrument panel and install a switch between the wires.
If a battery switch is installed, nothing will work. This switch may cause the depletion of the SI batteries, but the main battery will stay intact for months.

30ma sounds about right.

If the SI board is properly refurbished, it will not drain the starting battery. I have about several thousand customers that do not report battery drains with our SI boards and clusters including the four E30's we have. If you remove only the LED checkpanel, that will probably eliminate most of the drain on a failing SI board.

[Vincenze]

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.

When I disconnected the instrument panel, the amperage was 30mA lower.
When I disconnected the clock, the dong, the check panel, the difference was 2mA or so.

I think it's a good idea to cut the wire that goes from the fuse 21 to the instrument panel and install a switch between the wires.
If a battery switch is installed, nothing will work. This switch may cause the depletion of the SI batteries, but the main battery will stay intact for months.

[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.

[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.

[Vincenze]

Why do you guess?

Disconnect the dome lights and measure the amperage.

[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]

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.

[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]

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]

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]

A larger Group 49 battery fits into the trunk location.

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

[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.

[ThomasE30]

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

[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]

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!