GEL or AGM battery

[apetrov1x5]

Originally Posted by HPIA4v2

From what I can gather on this AGM battery so far is that it's not far superior in cold temp but it has very small self-discharge curve (around 1-3 percent of capacity per month). That;s why BMW switch to this on newer models since those tend to have more electronics (i.e comfort access, that can drain battery while sitting in garage if the FOB is within 30ft in many cases).

The problem for older X5 would be charging (or over charging in this case) of AGM battery possibly shorthening the life of it. That's why on newer BMW there is inteligent charging algorithm that register the batt mfg date and the car adjust the charging current overtime (being more toward the end of batt life).

I am reading on the net that GEL battery are suffering more from that than AGM

[HPIA4v2]

Originally Posted by apetrov1x5

I am reading on the net that GEL battery are suffering more from that than AGM

It maybe, AGM and gel is similar technology (instead of using the liquid sulfuric acid as electrolite it uses gel, while AGM added glass insulation to reduce self-discharge between cells further). Maybe also the glass insulation may be able to absord the gas forming while charging/over charging.

Again assuming you have E53 (not E70) X5, the car alternator/regulator provide up to C/4 (C being the full capacity ~ 80Amp) while GEL/AGM never like anything more than C/8 or C/10 of charge current. Newer BMW like E60/E90 with IBIS circuitry will limit the current by looking at the date stamp of the batt and gradually adjust the charge current over the life of the batt (hence the registration upon replacement to reset this algorithm is required or customer will be back for new AGM batt in 3-4 years due to over-charging).

I am not sure you'll see the benefit of GEL/AGM under severe weather though, does the batt mfg claims that? I never look into bad weather situation since my car always garage and Seattle weather is not that bad.