Chassis battery voltage dropping, now 4 volts

[bukzin]

Originally Posted by Shallow

The batteries that I removed are Alliance EPM A1031MF batteries. I searched the Alliance website for this model's info and they are listed as 12 volt batteries. I'm assuming replacing them with 6 volt batteries would work fine, but would require wiring them differently from how the 12 volt batteries were wired. Thoughts?

You may want to think about a battery shop. We have one in town
that mostly does ag vehicles and big trucks.

They carry Trojan and InterState. Prices are a little higher but
the install is free (as well as charging system tests) and they
know what they are doing.

I could do that myself but they are super fast and stand behind their work.

Costco used to carry very good batts for good pricing but
no longer have them around here.

[navigator336]

I would strongly recommend using 12 volt starting batteries in parallel just as it comes from Freightliner for the chassis batteries not two 6 volts in series. Although the deep cycle 6 volt batteries would start the engine, they are not designed to be starting batteries. As you've already learned, the Alliance batteries are original from Freightliner. Your plan to replace both, in my opinion, is definitely the way to go. Most likely what happened is one of the two shorted out across the plates causing it to completely drain. It then became a parasitic load on the other one. If one of them was still good, being drained that low makes it doubtful it could be revived anyway. At 8 years old, they are done. One of my Alliance batteries died at 8 years (last year). The other one was still taking a good charge, but I replaced both with Interstates with better specs than the originals. They are group 31, which as mentioned above is not available at many of the normal battery retailers.

[TQ60]

Gp31 is very common as ford f250 diesels use them.

Sams and costco have them

[Shallow]

I ended up going with NAPA. Best price and nearest location. $109 per battery out the door. She fired right up after install. Now let's see if they hold their charge over the next few days or if I have a bigger problem.

[pasdad1]

If you have to use what's close by.....auto zone carries these. You would need two of them, wired in parallel.

[Shallow]

Originally Posted by pasdad1

If you have to use what's close by.....auto zone carries these. You would need two of them, wired in parallel.

Attachment 73192

pasdad1

I saw those listed on the Autozone website. But, seeing how my connections were already set up for 12 volt batteries and NAPA's pricing was going to be $60 less for the pair, I figured the NAPA 12 volts were the way to go.

[dr2casto]

You wouldn't happen to have it connected to a trailer with the emergency brake wire pull off out of position would you? This will cause the batteries to energize the brake system on the trailer until depleted. ..........just a thought.

[Shallow]

Originally Posted by dr2casto

You wouldn't happen to have it connected to a trailer with the emergency brake wire pull off out of position would you? This will cause the batteries to energize the brake system on the trailer until depleted. ..........just a thought.

Good idea, but no. It wasn't connected to a trailer when they failed.

[gemini5362]

There are a lot of unexpected current draws on a battery when the ignition is turned off. I have a small battery tender wired on the battery cable. When I park my coach I plug into a 20 amp house receptacle just to keep the batteries charged. If you have that option it is the best way to go. If not remove the negative cable when it is going to be parked for more than a few days.