Batteries cooking

[Redland1]

Hello all. My truck is currently boiling the batteries (sulfur smell) and I replaced them this past January. The last 4 did the same thing. Only thing that changed was that I replaced the alternator from a 160 to a 200 something. I did a quick google search and it’s ai said that it might need a remote voltage sense wire from the alternator to the batteries. What do y’all think the problem can be ?

[mikkhh]

How much is the charging voltage?

Cheap crap aftermarket batteries last maximally for a year nowadays, sometimes even less.

[Redland1]

(07-22-2026 )mikkhh Wrote:  How much is the charging voltage?

Cheap crap aftermarket batteries last maximally for a year nowadays, sometimes even less.

According to my Scangauge D it’s 13.8-14.2 at idle. See it go up to 14.5 while going down the road

[mikkhh]

Voltage looks good. On trucks the only batteries that work are genuine truck manufacturer batteries. They are sometimes priced quite well and cost around same as name brand batteries, but are way way better.

On trucks if aftermarket battery lasts a year then you are really lucky and got your moneys worth, but genuine last 2+ years usually.

[Rawze]

14+ sounds high. That high of voltage would cook all but the oldest style of old-school lead-acid batteries.

13.6 - 13.8 is the norm,... not 14+.

You need to put an actual volts meter on the thing while at high rpm ... as those digital devices get it from the J1939 where it is typically less accurate.

If your using AGM's (glass-matts) then they can only handle about 13.2 full time, and 13.6 or so only on peak. They will cook at 14+.

If your using gel-cells... well, I feel sorry for you, as they are horrible in most applications, and also can only handle about 13.2 max.
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As far as the alternator goes, get the paperwork for it and ensure its hooked up correctly.

Also,.. that AI crap, throw it in the garbage... If anything, the sense wire should be jumped to the output right at the alternator so that you get the expected voltage drop by the time it reaches the batteries. If you put that sense wire on the top of the batteries themselves, then you will get the higher voltage all the time.

I.E.> the sense wire does need to always be connected to something.. I always do it right at the alternator to help protect the batteries from getting over-charged.

[Redland1]

(07-23-2026 )Rawze Wrote:  14+ sounds high. That high of voltage would cook all but the oldest style of old-school lead-acid batteries.

13.6 - 13.8 is the norm,... not 14+.

You need to put an actual volts meter on the thing while at high rpm ... as those digital devices get it from the J1939 where it is typically less accurate.

If your using AGM's (glass-matts) then they can only handle about 13.2 full time, and 13.6 or so only on peak. They will cook at 14+.

If your using gel-cells... well, I feel sorry for you, as they are horrible in most applications, and also can only handle about 13.2 max.
===========

As far as the alternator goes, get the paperwork for it and ensure its hooked up correctly.

Also,.. that AI crap, throw it in the garbage... If anything, the sense wire should be jumped to the output right at the alternator so that you get the expected voltage drop by the time it reaches the batteries. If you put that sense wire on the top of the batteries themselves, then you will get the higher voltage all the time.

I.E.> the sense wire does need to always be connected to something.. I always do it right at the alternator to help protect the batteries from getting over-charged.

It didn’t have a sense wire before but I installed one today. So I connect the other end of the wire to the B+ post ?