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dump truck batteries, replace in pairs?

apm

Well-Known Member
Joined
Apr 1, 2011
Messages
171
Location
Northeast Tennessee
I've got a chevy 7500 dump truck with Cat diesel. It has a pair of batteries. Just started going dead after sitting a few days. First thing I did was to put in a heavy duty battery disconnect, suspecting parasitic drain. That didn't help. I load test the batteries and one checks good, one indicates replacement needed. Do I need to replace both as a pair, or can I get by with just replacing the one that checks bad?

Thanks,

Greg
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
The short answer is to replace them in pairs.

The long answer could be that if it is a truck that gets used very frequently and the good battery is not that old, you might get by with replacing the bad one. But if it sits a lot then one can drag down the other. But if you put an AC powered battery tender on it then it might be OK anyway.

Not a completely straightforward answer.
 

Ct Farmer

Senior Member
Joined
Dec 8, 2016
Messages
322
Location
Connecticut
I don't know if it is true, but it makes sense, my battery supplier told me to do in pairs because the new one will do most of the work when you replace only one. Has to do with discharge rate and reserve capacity. Said the new one will have a shorter life.

Maybe he just wants to sell batteries.
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,863
Location
WI
Both or none, it may start just fine with one battery, especially if you plug it in on the colder days, and for sure if you plug it in and add a battery warmer. If that one battery won't start it, then something is wrong.

You can replace one battery, but you might regret it.
 

Bls repair

Senior Member
Joined
Jan 21, 2017
Messages
1,612
Location
S E Pa
Occupation
Equipment operator,mechanic
12 volt or 24 volt ,were the battery connections clean and tight? If not you may have been drawing more from one battery then the other.
 

apm

Well-Known Member
Joined
Apr 1, 2011
Messages
171
Location
Northeast Tennessee
I replaced them both. The old ones were Exide 31XHD. When I removed them they both had tags on the sides that said November 2016, so a little less than 3 years old. I've only had the truck a few months. One of the batteries still checked good and I should have kept it for some of the other equipment, but had to bring in the core to get the price on the new batteries. The truck doesn't get used that much, so hopefully with the battery disconnect, now, these will last. It's a 12 volt system and the connections were clean and tight.

thanks for the advice,

Greg
 

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,257
Location
Canada
Those batteries may have still had some warranty left but replacing them isn't a big expense in the grand scheme of things.
 

rsherril

Senior Member
Joined
May 2, 2009
Messages
264
Location
Far West Colorado
Occupation
Geologist, Retired from teaching sciences
Similar situation here. Two batteries from 2016 with disconnect switch, 500 cca each. Load test after a failed start showed batteries were equal. Replaced both because I'll not want to mess with them this winter. Got a new lesson with a Capacitance Test. Each battery was 12.2 V which charrted out to 200 cca each. Problem is that I used the machine less than 200 hour since since 2016. Maybe time for a battery maintainer.
 

Centexhoe

Member
Joined
Dec 23, 2016
Messages
5
Location
Texas
Occupation
Crane operator, Crane mechanic, welder, machinist
Battery tenders/maintainers are the ticket! We use them on race and show cars all the time. I always replace batteries in pairs when they are paired. I also use CAT batteries in all heavy duty work. They seem to last longer than most others, even after abuse. Just my 2 cents
 

old-iron-habit

Senior Member
Joined
Nov 22, 2012
Messages
4,233
Location
Moose Lake, MN
Occupation
Retired Cons't. Supt./Hospitals
I use a separate disconnect on my dual batteries. One for each battery. Here in the cold country the bad battery usually drains the good battery and then that one freezes and breaks. I shut the switches off alternately when using them to insure both batteries get full charge. Of course this only works with batteries hooked in parallel's.
 

56wrench

Senior Member
Joined
Dec 4, 2016
Messages
2,074
Location
alberta
if two batteries connected in parallel are used, they should be replaced at the same time for maximum efficiency. they should be exactly the same-therefore they will have the same internal resistance and will be recharged at the same and equal rate. otherwise the battery with the least internal resistance will accept most of the charge if only being used for a short time assuming the connections and cables are good. if they are a matched pair they will both be drawn down at the same rate and recharged at the same rate.
 

edgephoto

Senior Member
Joined
Aug 13, 2019
Messages
727
Location
Stafford, CT
Battery warranties are pro-rated. They use MSRP to calculate the warranty amounts. So if you are past 75% of the warranty period you usually end up paying for most of the battery anyway.
 
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