Dead batteries!

[fireball]

100-series brethren,

I am hoping someone might be able to help educate me about my dead batteries. The 100 has been tucked away in the garage for almost 2.5 months now, I finally got back into town today and checked the batteries and they were both dead! The main battery was below 7v! The aux battery was at 11.4 and when linked barely enough to get the interior LEDs on dimly.

Since the main is so low I can only assume some type of rather major parasitic draw. Strange that the aux was so low as well - it runs only the amp and an aux fuse panel with CB, back up lights, rear interior LED. None of those were on and pretty sure nothing was left on.

Any advice or help on how to diagnose the issue would be greatly appreciated.

FWIW, both of the batteries are less than 1yr old Sears DHP marine. Grp31 main, 27 aux. T-max controller.


Thanks in advance for any help!

(P.S. I am going to do some more searching so please don't yell. The past few months I've seen numerous thread repeats come up, so this should at least be a relatively fresh discussion

 

[Sandroad]

Well that's a bummer. It would not take a major parasitic draw to pull a battery way down over 75 days, so look for small problems too. I have no experience with dual battery set ups in a LC, so I won't try to help there. However, I have lots of experience with the Sears DHP Marine and I suspect you may not be able to fully resurrect the one that sat for so long in so low a state of charge. I'm pretty sure those batteries are unusually susceptible to sulfating when left discharged for a long period of time. It may charge back up, but I think you may find that it will take only a "shallow" charge and not be useable as a deep cycle battery anymore. Not sure about the one that sat at 11.5 volts, but there is probably some damage there too. If they in warranty, it would be worthwhile to have Sears test them. If not, there are some "de-sulfators" available that might help (or not). You'll find lots of info on possible parasitic draws when you do the searches.

http://www.solar-electric.com/badebysocoin.html

 

[jcrandall]

Not sure of the term, but the first place I would look is the remote wire that controls when the amp is on or off.

 

[fireball]

Maybe I am not using my meter correctly or maybe I don't understand how to use it....

I have removed the negative battery cable and set my meter to read Amp or mA. With doors closed and everything off I put my wires on the negative terminal of the battery and of the negative battery cable and it reads 40-50mA. Strangely when I put the meter on it reads closer to 100mA, and then slowly over the course of 5-10s levels out at the 40-50mA reading.

I put the charger on it and its back up at 12.5V, so I will leave the negative battery cable disconnected and see how quickly it drops down. I'm thinking the big battery is faulty and perhaps the small aux battery just can't handle 75 days of slow drain from the USB outlet illumination and possible stereo/amp slow draw?

 

[AimCOtaco]

With that much invested in batteries I would recommend a good charger/maintainer for storage of more than a couple of weeks. Lead Acid AGM batteries don't like to be discharged that low, getting down to 7.5 v best case will reduce life, worst case they won't come back.

 

[PADDO]

Maybe I am not using my meter correctly or maybe I don't understand how to use it....

I have removed the negative battery cable and set my meter to read Amp or mA. With doors closed and everything off I put my wires on the negative terminal of the battery and of the negative battery cable and it reads 40-50mA. Strangely when I put the meter on it reads closer to 100mA, and then slowly over the course of 5-10s levels out at the 40-50mA reading.

I put the charger on it and its back up at 12.5V, so I will leave the negative battery cable disconnected and see how quickly it drops down. I'm thinking the big battery is faulty and perhaps the small aux battery just can't handle 75 days of slow drain from the USB outlet illumination and possible stereo/amp slow draw?

You're reading your meter correctly. When you hook up the meter you're completing the BAT circuit so everything that's connected to the BAT bus will be energized, things like the immobilizer cct, dome cct, remote unlock cct, multiple ECUs that have keep alive memory etc - I don't have an EWD in front of me but you get the idea - so they all have an "inrush" current albeit in mAs. That's what you're reading. Even a Tmax controller has about 5mA drain when in standby, and closer to 150mA when the display is active. Normal, steady state "off" power consumption is in the 30-50mA range and extra electronics that's on the BAT cct may well add to the vampire power consumption.

 

[PADDO]

With that much invested in batteries I would recommend a good charger/maintainer for storage of more than a couple of weeks. Lead Acid AGM batteries don't like to be discharged that low, getting down to 7.5 v best case will reduce life, worst case they won't come back.

This^. Batteries were easier when you could measure the specific gravity and temperature correct and know what your state of charge is. Not so simple now with more sophisticated maintenance free batteries with their unique charging profiles and needs.