I have a stock 1999 100 series…I had an “inexpensive” 24F battery from Autozone that was on its last legs and today I installed a new 27F group battery from X2 (old Northstar Brand I think?). I noticed that while the new battery passed the battery test it was only at 13.8volts according to the battery tester the shop had. Should I be concerned that this more capable new 27F group battery needs some sort of beefed up alternator to be adequately charged? Thanks for any guidance.
Switched from Group 24 to 27 Battery - Alternator Mods? (1 Viewer)
- Thread starter BenM
- Start date
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No. The factory alternator can easily charge either battery. Was the 13.8 volts at idle or high RPM? Loaded (lights and fan running) or unloaded? If your alternator is dead or dying, that's a different issue from needing an upgrade. Also, your new battery may not have been fully charged, so test it after a couple days of driving (or after charging) before making any conclusions.
The X2 is an AGM battery. It's my understanding that an AGM battery needs a higher voltage output from the alternator to fully charge. You'll need the GM diode in the link below to help your alternator adequately charge your AGM battery.
www.cruiserpatch.com
AGM Battery Voltage Boost Regulator (GM 12135037)
*Expect 1-2 week lead time when out of stock Adding a voltage booster is a necessary upgrade for anyone running an AGM battery in their vehicle. Cruiser Patch uses this GM diode to increase alternator voltage output at idle and under load from 13V to 14.6-15V. See photos for proper orientation...
www.cruiserpatch.com
- Thread starter
- #4
Steve, the 13.8 was at idle with minimal load , I think the AC was off and the lights were off for sure (daytime), I have no other accessories. I checked again today and
off: 12.8v
idle no load immediately after start: 14.0v
idle no load after about 1 mins since start: 13.8v
idle full ac and lights : 13.77v
Does that seem acceptable?
GTV
SILVER Star
You went from an undersized battery to a stock sized battery. There is no need to upgrade anything.
@BenM - those numbers seem good for a working alternator and running a lead acid battery. You want solid charging voltage with 'everything' on, as if you were at idle in a blizzard, running headlights, heater fan, wipers, rear defroster, etc. Weak/bad alternators can sometimes show decent voltage unloaded, but fall flat on their face under high load conditions. Fortunately, you usually get a little warning before they totally die.
If you're going to run an AGM, you may need some mods to create higher voltages, but I'm not familiar with them.
If you're going to run an AGM, you may need some mods to create higher voltages, but I'm not familiar with them.
@BenM - as others have mentioned, it boils down to the chemistry of your new battery. The stock battery is a bog standard, Lead Acid battery. Your X2 _might_ be an AGM (Absorbed Glass Mat) battery, but you'll want to investigate to confirm.
Ideally an AGM battery should be charged with 14.4-14.8 volts, whiich is about .5 volts higher than the stock alternator/charging system is designed to produce. This results in the battery never quite getting fully charged which is less-than-ideal for capacity and longevity. Here are some of the common workarounds for the problem:
* Purchase a smart battery charger which is capable of charging AGM batteries. Hook up the charger every 3 months or so to ensure it's topped off.
* Swap out the alternator fuse for a diode/voltage booster to increase the voltage sent to the battery.
forum.ih8mud.com
Ideally an AGM battery should be charged with 14.4-14.8 volts, whiich is about .5 volts higher than the stock alternator/charging system is designed to produce. This results in the battery never quite getting fully charged which is less-than-ideal for capacity and longevity. Here are some of the common workarounds for the problem:
* Purchase a smart battery charger which is capable of charging AGM batteries. Hook up the charger every 3 months or so to ensure it's topped off.
* Swap out the alternator fuse for a diode/voltage booster to increase the voltage sent to the battery.
Alternator Voltage Booster
Haha thanks, I am in America. I am just looking for the other option where I can keep the fuse as well. Has the solution from O'Reilly's been reliable for you? Going on a year and a half now now and hasn’t skipped a beat.
forum.ih8mud.com
7.5A MK3 Mini Blade (Electronic fuse version) | HKB Electronics
The Alternator Voltage Booster was the first of its type on the market and is the only unit available that was has been purpose built for alternator voltage boosting.
www.hkbelect.com
Last edited:
TreatSmash
SILVER Star
I love this group, I have been running a group 31 AGM for 3 years now and always thought my voltage was a bit low at 13.8ish, just ordered the cruiser patch fix.
- Thread starter
- #9
- Thread starter
- #10
Thank you all for your input. What is the cruiser patch fix, is this about a different Diode or Volt Reg for the Altnerator? That seems reasonable to bump up voltage towards 14.3. Something I might do.
AGM Battery Voltage Boost Regulator (GM 12135037)
*Expect 1-2 week lead time when out of stock Adding a voltage booster is a necessary upgrade for anyone running an AGM battery in their vehicle. Cruiser Patch uses this GM diode to increase alternator voltage output at idle and under load from 13V to 14.6-15V. See photos for proper orientation...
www.cruiserpatch.com
It's just a GM diode you replace a fuse with. You'll need to trim the sides of it slightly to fit it, super easy if you already have a pair of snips lying around.
