Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 
 


Reply
 
Thread Tools Display Modes
 
Old 11-15-2019, 07:02 PM   #1
Platinum Member
 
@Michael's Avatar
 
Join Date: Oct 2018
Location: MN
Posts: 497
Default Lead Acid Battery testing advice?

I have two 100AH lead acid batteries that came with my one year old 2019 Coachmen Crossfit that I don't think are healthy.

Here's what I know (or think I know):

If I leave the coach plugged in for a long time (a week) the charge current from the WFCO converter & solar panels tapers off and the batteries presumably are 100% charged.

If I then draw a moderate current from the batteries (5-8A) the battery voltage drops down to 12.2V in a few hours and triggers the low voltage disconnect. Presumably I'm getting something less than 20AH capacity from 200AH of battery before hitting the 12.2 volt threshold. That doesn't sound right to me.

It been cold - say about 40F when I tested. I'm assuming that at 40F I should have been able to extract around 40% of the batteries capacity befor hitting 12.2V, but I'm only getting a fraction of that.

The batteries are a no-name 12v deep cycle battery that was presented as 'sealed' but in reality have flush screw-in caps for the cells. Actual brand is "Xpedition 31DCM deep cycle battery".

I dropped them down from under the coach and have them on the bench. Cells are full to within 1/8" or so of the fill marks. Specific gravity at 40F is 1.28-1.3.

I'd like advice on steps to take to determine if the batteries are working as expected or not. I.E. - if at 40F a lead acid battery only is expected to have 10% of it's labeled capacity then the batteries are good and I just need to move a thousand miles south.

If they are junk, I'll probably put new AGM's back underneath the coach and call it good. Getting at them is a PITA - it's not possible to reach the terminals or caps while they are mounted under the coach.
@Michael is offline   Reply With Quote
Old 11-15-2019, 07:42 PM   #2
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 11,914
Default

Quote:
Originally Posted by @Michael View Post
I have two 100AH lead acid batteries that came with my one year old 2019 Coachmen Crossfit that I don't think are healthy.

Here's what I know (or think I know):

If I leave the coach plugged in for a long time (a week) the charge current from the WFCO converter & solar panels tapers off and the batteries presumably are 100% charged.

If I then draw a moderate current from the batteries (5-8A) the battery voltage drops down to 12.2V in a few hours and triggers the low voltage disconnect. Presumably I'm getting something less than 20AH capacity from 200AH of battery before hitting the 12.2 volt threshold. That doesn't sound right to me.

It been cold - say about 40F when I tested. I'm assuming that at 40F I should have been able to extract around 40% of the batteries capacity befor hitting 12.2V, but I'm only getting a fraction of that.

The batteries are a no-name 12v deep cycle battery that was presented as 'sealed' but in reality have flush screw-in caps for the cells. Actual brand is "Xpedition 31DCM deep cycle battery".

I dropped them down from under the coach and have them on the bench. Cells are full to within 1/8" or so of the fill marks. Specific gravity at 40F is 1.28-1.3.

I'd like advice on steps to take to determine if the batteries are working as expected or not. I.E. - if at 40F a lead acid battery only is expected to have 10% of it's labeled capacity then the batteries are good and I just need to move a thousand miles south.

If they are junk, I'll probably put new AGM's back underneath the coach and call it good. Getting at them is a PITA - it's not possible to reach the terminals or caps while they are mounted under the coach.

You would need to get a temp compensation allowance chart for the specific gravity, but I think that your readings are very close to full at 40*F.


Your actual capacity does seem very low, though, so something is not right. I think at 40*F you should have over 80% capacity.


I would start with a load test for reference although not the best for deep cycle battery testing, and then do a 20 hr rate, in amps, capacity test to 10.5v to see what you are really getting.



My bet is that the batteries are toast.
booster is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 02:44 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.