Something is draining my battery

Jcparmley · September 22, 2018, 08:14:45 PM

Hello All

How could two new batteries drain down when the main switch is off? Everytime I go to start the bus my batteries are drained just enough to not start the bus. When I hook up the jumper cables to my truck and the bus starts great, The funny thing is I always turn off the main power and the end of the day.

neoneddy · September 22, 2018, 11:08:48 PM

You'd want to get an clamp style amp meter and see if you notice any draw.

Maybe infant mortality on the new battery? Make sure they get a good charge after being drained.

By chance do you have an equalizer? Maybe that is malfunctioning and drawing current?

Busn-Gramps · September 23, 2018, 05:12:25 AM

If you have an equalizer that could very well be your problem !

richard5933 · September 23, 2018, 05:29:44 AM

Double check to nothing is connected to the unswitched side of the main disconnect. We found that the shore power charger and a couple of circuits were on the wrong side of the switch, causing them to never disconnect.

luvrbus · September 23, 2018, 05:40:07 AM

It would be nice to know what year and model of bus we are having the problem with ,without the info it's a WAG some buses will not kill all the power drain even with the master switch turned off.If it's a MCI with the center tap for 12v you will find it on the 12v side,my MCI is electronic transmission and engine there no way to stop the drain even with the master switch off.You will find some baggage bay lights are hot with the switch turn off lol I discovered that at night time

windtrader · September 23, 2018, 09:35:22 PM

Quoteget an clamp style amp meter

Ditto that! Once I got a good multi-meter with a clamp for current readings, life is much much better. So much less guessing. Disconnect the starts from house or any other batteries. Quickly just put the clamp over the positive sides of the different banks looking for draw. If nothing then connect the main start battery. Check again. If you get no reading here then your start side is not pulling any current.

On the house bank, look for current draw. Then start looking for which circuit is drawing. For example, check something like a 24v to 12v equalizer for current.

It won't take much time to discover the source. Good luck

TomC · September 25, 2018, 05:31:47 AM

Charge batteries, then fully disconnect them and check batteries in a couple days-just to make sure the batteries are OK. Good Luck, TomC

luvrbus · September 25, 2018, 06:15:17 AM

Like TomC said you don't need any meters to tell if you have a drain,disconnect the cables when you connect those back up you see a small spark if you have a drain lol it's easier for me to see when it is later in evening and turning dark

buswarrior · September 25, 2018, 09:08:26 AM

The PA amp is a notorious parasite on the older coaches.

Inside the electric compartment under the driver's mirror.

Follow the microphone leads, pull the power plug. Ghost gone?

Happy coaching!
Buswarrior

Jcparmley · September 25, 2018, 10:56:58 AM

I have a MCI 102c3 that I am converting. I haven't gotten to the stage where I am wiring so the bus is still stock as far as the wiring is concerned.

Quote from: luvrbus on September 23, 2018, 05:40:07 AM
It would be nice to know what year and model of bus we are having the problem with ,without the info it's a WAG some buses will not kill all the power drain even with the master switch turned off.If it's a MCI with the center tap for 12v you will find it on the 12v side,my MCI is electronic transmission and engine there no way to stop the drain even with the master switch off.You will find some baggage bay lights are hot with the switch turn off lol I discovered that at night time

Jcparmley · October 31, 2018, 04:14:24 PM

So this past week I went to start the bus and the battery was dead. Not both batteries, just one. I thought that was strange because if they were tied together wouldn't they drain together? I unhooked the two batteries and with a voltmeter tested each one. 12 volts on the left battery and 0 volts on the right. The batteries were purchased at Batteries + in February. So I brought the battery in and in order to receive a new battery they needed to try to charge it overnight. So two days later I called them and they said they would give me a new one, however they said that the "defective" batter had reversed polarity. I asked them how that could have happened and they said that I must have charged the battery in reverse. How can that happen? When I charge the batteries I always disconnect the cable that links the two and charge them separately with a 12 volt charger. So my question is how can one of the batteries go dead when the main switch is off and the batteries are connected together? I want to figure this out before I put the new batter in because they specifically said they won't warrantee the new battery.

richard5933 · October 31, 2018, 04:31:07 PM

What testing did you do before replacing the batteries?

Rather than all of us make the same suggestions over again, could you tell us what you found the last time around and what steps you took before installing the new batteries? It would really help us help you.

buswarrior · October 31, 2018, 05:39:25 PM

Which battery? The one closest to ground, or the one closest to the battery cut-off switch?

Sounds suspiciously like something on a center tap.

happy coaching!
buswarrior

Jcparmley · October 31, 2018, 08:59:59 PM

I have a 1989 MCI 102c3. The first thing I did was disconnect the batteries from each other. Tested both and charged them independently from one another. They both tested at 12 + volts. Then I connected them back up and tested each. Both 12 volt and 24 volt when combined. I then checked to see if the main shut off switch was actually working correctly, it was as far as I could tell with the volt meter. At this point I was able to start the engine. I then checked to see if any of the circuits in the electrical panel under the drivers window was hot while the main switch was off. I could not find a circuit that was live when the main switch was off. I then let the bus sit for a few days. After a few days I came back and checked the batteries again. The left side battery that was under the Vanner box was at 12 volts. The right side batter closest to the main disconnect was less than 12 volts.

I have gutted the PA system and I don't have bay lights. I guess I don't know what else to check in regards to a current draw when the disconnect is off. Perhaps I am missing something.

I waited a couple more days and tested again. This time the right battery showed no volts. So I disconnected it from the other battery and attempted to charge with a 12 volt charger. It would not take a charge of any kind. That is when I brought it in and the tech at Batteries + said the battery had it's polarity reversed. They said it could have happened by charging the battery backwards. However, I am positive (pardon the pun) that I charged them correctly.

It's just weird that one battery would drain when connected to the other battery. Logic would tell me that if there was a draw it would draw equally from both batteries, correct?

Quote from: richard5933 on October 31, 2018, 04:31:07 PM
What testing did you do before replacing the batteries?

Rather than all of us make the same suggestions over again, could you tell us what you found the last time around and what steps you took before installing the new batteries? It would really help us help you.

richard5933 · November 01, 2018, 03:47:21 AM

If nothing in the drivers electrical panel showed current when the battery switch was off, the next step would be to confirm the same at the electrical panel in the rear of the bus. I'm not sure where it is on your bus, but don't MCI buses have a panel in the rear near the engine somewhere?

You can also just check on the master switch itself. With both batteries connected and the master switch off, there should be no current at all on the load side of the switch. You said that you confirmed the switch is working properly, so then I'd check to see if something is connected incorrectly and is tapping into the battery side of the switch.

Sounds like you're still running the Vanner to get 12v from the 24v battery bank. This is where my attention would go. If it's failed or not hooked up correctly you could get the same results as not having an equalizer at all - one battery fully charged and one dead.

What it sounds like to me is that even with the master disconnect in the 'off' position, you've got something drawing power from the center tap - either directly or through the Vanner.

Can you post either photos of how this battery bank is connected or a drawing showing the wiring?