Bad Batteries?

[Jim]

Please take a picture of one of your batteries so we can see what type and rating they are? 830ah for 4 batteries does not sound right.

Data here.

 

[Neal]

Very interesting! Those are big batteries, mine are 225 Ah @ 20hr rated of which I have 8.

 

[Jim]

Yes, they are big boys. I had to modify the battery compartment to make them fit. Was going to install 6 of them but the weight was a concern.

 

[Jim]

Very interesting! Those are big batteries, mine are 225 Ah @ 20hr rated of which I have 8.

I assume yours are 6-volt configured in series/parallel as well? Or about 450 ah of usable storage?

 

[Neal]

Yes, 8 x 6V batteries each pair makes 12V so you take 225 x 4 for the total Ah of the battery bank.

 

[Jim]

Yes, 8 x 6V batteries each pair makes 12V so you take 225 x 4 for the total Ah of the battery bank.

Roger. Don't forget to divide by 2, don't want to discharge below 50%

 

[sheridany]

This is a really helpful thread as I suspect my batteries are in a similar state however I need to confirm as @Jim has done. I also assume I have the same battery bank as @Neal since our VTDP coaches are only a year apart. What’s the next step in this diagnosis or do you need just need to replace some or one based on the findings?

one question for @Jim so I can replicate, I assume you created the 20 amp draw from lights refrigerator micro other appliances being on? When you mention you are measuring the battery bank with your multi meter could you elaborate on that? At the main terminal or each battery pair etc?

 

[Jim]

one question for @Jim so I can replicate, I assume you created the 20 amp draw from lights refrigerator micro other appliances being on? When you mention you are measuring the battery bank with your multi meter could you elaborate on that? At the main terminal or each battery pair etc?

I connected the shunt and meter (shown in the picture below) to the battery bank. I bought this setup on Amazon but I suspect some of the higher-end coaches (like you're and Neal's) may already have something similar installed. I can't test each battery individually, well not without a lot of effort hooking/unhooking and moving them around, etc., and I'm not going to do that.

So yes, I turned the shore power off and then turned some lights on/off until I found the 20 amp draw I was looking for. (I suspect the inverter was 5-6 amps by itself.) I took a battery voltage reading off the meter, and then came back 4 hours later to take another reading. It' was just math from that point on although I'm going to go back down in a few minutes and get another reading as 4:45 will be the actual 6 hr mark.

I did this same test yesterday using a little over a 6 amp draw and I could watch the voltage dropping. Click here for a 60 second video.

 

[Neal]

What size is the shunt. I think the BMV-712 and ME-BMK are 500’s.

 

[Jim]

The ad says it's a 100A shunt. I'm afraid I don't know what the actually means.

Edit: I didn't necessarly mean that I don't understand the difference between 100 amps and 500 amps, just not sure if the shunt used in a 500 amp application would be more accurate than one that was used in a 100 amp application. (or visa versa)