So I ordered a car replacement LiFePo4 Lithium battery that is of similar size to the one (which is not a group 35) that is in My 1985 GSLSE. It is made by Xing cell and was advertised as direct car battery replacement 42AH 550CCA. It's instructions state that it has to be kept at charge voltages no higher than 13.8 Volts. My battery when running has 14.05 Volts at the terminals. So I guess this is not going to work. Is there a way to adjust charge voltage through the regulator or is there a battery charge management device to run in series with the alt output? Anyone try Power tex battery replacements?

 

I'd go with an AGM instead.

 

I've been using a lithium battery from Lithiumax for some time now. Great little monster.
As I read on their site about one of their products:
"Direct drop in replacement for NS40L size batteries compatible with 13V-15V charging systems and alternators"

 

These are strictly for weight savings, yes? I see they are 20% of the weight of lead acid, according to the website. I also see they are 500% of the cost, and there's a bluetooth app, lol.

 

they also don't leak acid, which is nice

 

I agree with KanasCityREPU, AGM is the way to go unless unit weight is an issue that can "justify" the cost. While the AGM battery's "up-front" cost is higher than a regular battery they handle temperature extremes better, and last longer than lead-acid batteries.

 

Op asked about charging voltage over 13.8.
Just answered on that.