testknight

So I'm working on an issue with wife's 2013 GL450 where it will just not start. Everything lights up and looks normal, no codes or warnings/errors....it just won't start turning over. I replaced the battery under the seat about 2 years ago. If I trickle charge the car, it will start and run just fine for a couple days but then it won't start again. I have it charged up now (12.5v while not running) and am going to check voltage tomorrow to see if anything was draining it while it sat overnight (I don['t think that's the issue as last time it wouldn't start was right after a drive cycle that I'd expect would have charged it up). My obvious assumption was the alternator, but did do some testing see below and my questions, if anyone here has an idea and would share feedback I'd appreciate it:

- When I start up car and then test voltage (I'm using the jumping posts under front hood) it reads about 14.7v. Anyone think that's too high? Anyone ever test their own car? I typically expect 14.0-14.2 but haven't done much at all on this platform. Normal? (or regulator issue?)

- So this Aux battery in the trunk.... I've not replaced that. I don't believe that would impact the car starting (I am using the key, not the button), but does anyone know for sure? Did you ever have need to replace that battery and if so were you having issues starting before you did?

- Anyone replace the alternator on these cars? I'm not so sure it needs replaced as the voltage to battery is higher while engine running (but see my high voltage question above), but if I do need to, any quick suggestions? I've done 3-4 in my lifetime, so am really just looking for best practice...pull from top? Bottom? Will I need ot take fan out? Any other suggestions? I could buy the shop guide, but usually alternators are simple enough to eyeball it, IMO. Just wanting quick ideas.


So anyway, I'm going to see what the battery indicates tomorrow as it sits overnight to see if its much lower (doubt that's the issue). I will then play around with watching voltage on battery as I let radio run while engine is off to drain it a bit, then running engine for a while to see if its being charged back up, etc.

Any thoughts, ideas, experiences? Can't have the wife stuck somewhere but also can't handle paying dealer for work I can do (and get parts so much cheaper). Thanks for any advice/help

testknight

OK Just tested it again and it is reading 14.8-14.9 now while running. Seem to high to anyone?

I've not done it before but could it just be a matter of needing to replace the voltage regulator? If so, isn't that part of the alternator so is it something you can replace by itself or do I need to get an entire new alternator? (I've not replaced a voltage regulator, only alternator entire assemblies).

At any rate, I'll revisit here to let folks know how things go down for future searches. Again, any ideas/advice is appreciated.

acetaylor

I don't think your running voltages are too high. Just out of curiosity, what voltage do you get under load with the lights on, a/c running, fan on high speed, etc?

I don't fully understand the purpose of the small aux. battery, but just maybe, that may be your problem. I believe it too is under the seat on the right side of the service battery. Hope that helps.

testknight

For those searching on this in future...I found the battery in the trunk. I removed the spare tire and all that and was able to access it by forcefully popping a couple push pins out (on right side of trunk floor where spare used to be). It was mounted to a bracket that was mounted on car by 4-5 10mm bolts. Once you get bolts off you have to lift it out but there isn't much clearance above it to do so. I ended up using a screwdriver to pop it up and out.

The battery is WAY smaller than I expected. The local parts store sold me a battery that was supposed to be for the 2013 GL450 but it was about 5" tall, 6" wide and about 3" deep (estimated from memory, but looked like the AUX battery I replaced in my CLS55) This battery that I pulled out of car, looks like it came out of a toy...it is about 1.5 inches tall, maybe 3.5" wide and about 1.5" deep. I've never seen such a small battery come out of a vehicle. I can't imagine this will have an impact on starting car but will likely replace it anyway. I now need to order one from MB dealer as no local big box parts store seems to carry it.

Gill Senderov

https://www.batteriesplus.com/produc...BoCECMQAvD_BwE

chsu74

You may just have a faulty big battery. 14.7V is what your alternator will put out in the beginning and then will drop as you drive a bit. The small battery is to power the gear selector when the large battery fails.

testknight

thx

Yeah I'm heading in that direction. I am letting it sit overnight and will double verify nothing is drawing from battery while car is off. If its still holding at 12.5v range (as it has for almost a day already), I'll run radio and lights while car is off to drain battery, then run the engine to verify alternator is charging it back up.

If alternator is doing its job, I'm looking closer at main/big battery. The thing is right at 2 years old so just couldn't imagine it would be crapping out already, but I think that would be the last thing for me to look at if everything else checks out ok.

geniushanbiao

This is a typical sign of your main battery getting weak. It either doesn't hold charge well or charges too slow due to increased internal resistance. The voltage when running shows the charging system is working properly. You need to get the battery replaced. I replaced the one on my 2015 GL350BT with one from advanceautoparts for $150+tax. No need to break your wallet for it. AAP typically has 25% off if you order on their website.

The main battery is located underneath the passenger front seat. You access from the back by pushing the front seat all the way forward. You can check if the carpet has been cut. If it's not cut then you have the factory installed battery that's 7 years old. The first time replacing the battery requires cutting the carpet underneath the passenger seat.

Hillj4

New to GL550. How long should a battery last? My GM cats generally get 5-6 years, but have much less tech in them.

geniushanbiao

Based on the information from various sources, I'd say on average auto batteries last about 5 years with typical usage pattern. But it depends on a lot of factors including the usage pattern. I've personally experienced/seen as short as 2 years and as long as close to 10 years.

On other cars hot climate tends to shorten the lifespan of battery due to the increased engine bay temperature, but MB batteries are mounted in passenger compartment so not affected too much by climate though. Auto batteries are not designed to do deep cycle so if you happen to discharge the battery once it shortens the life a lot. If it's frequently deep discharged it probably won't last past 2 years. Also the way it's equipped has effect as well. For example if one puts a small battery on a large engine it tends to last shorter, and vice versa.

testknight

I usually expect a battery to last 3-4 years. I'm pretty sure my issue is the main battery now. I charged it up and it was reading 12.4v, I then, while car was off, turned headlights on a couple minutes and turned back off (get rid of that surface charge). When I retested the thing dropped to 10.x volts which went to far down too fast.

I'd share that the battery in there now, as I found the receipt, is only 18 months old. I'd also share that I read today that 30% of car batteries don't make it 3 years.

I got the little trunk battery in today (a bit smaller than a cigarette pack I'd say), though I am certain it had no impact to this issue. I've had the car a few years no and figured it won't hurt to replace since I already had that part of trunk opened up (easy job btw). I'll be replacing the big battery tomorrow. I've done it on this car before and twice on our 2008 R350, which is same process under the seat. SUPER easy, though I tend to bust a knuckle or something each time I do.

I'm of mind this will fix issue, but will report back to verify for anyone searching around in future.

geniushanbiao

What brand and model battery do you currently have in the truck? If it's only 18 months old it should be still under warranty. I buy my battery from AdvanceAutoParts and they have 3 years free replacement. I have had very good experience with their Autocraft batteries and they always have 25% off coupon that brings the price to very reasonable. X166 GL uses H8 AGM that's listed as $200 so with the coupon it brings down to $150 and I'm covered for at least 3 years. Autozone's Duralast H8 battery also provides 3 years warranty and is also priced at $200 but I didn't find any way to save $50 like AAP.

Those don't make 3 years are most conventional VRLA ones been trashed by the owner. AGM batteries last way longer. My 2013 C300 original AGM battery was still strong in late 2019 when it involved in an accident and totalled. I bought my 2012 ML350BT with its original AGM battery last year and it didn't have any issue. I got it replaced last year at 90k miles since I feel it was getting weak but it never gave me any issue to be honest. That's a 7 years old one.

I agree that on GLs the battery tends to last shorter. I bought a 2015 GL350BT at the beginning of this year with 72k miles and the battery was not holding charge very well. Got it replaced anyways.

testknight

Yeah I got mine at Advance auto as well. I'll be lugging the old one in there tomorrow.

fabbrisd1

Like this is a "surprise" - with auto part's store brand Battery - my experience maybe 25% make it thru warranty without replacement - and then the kicker you only have the balance of the original warranty to cover the replacement.

Manufacturer's are not stupid - it's their "design" that this battery lasted 18 months - and when the replacement goes out 18mo down the road on "cue" 1 month after your battery warranty goes out - you buy your 2nd.

In short - you are buying $100 batteries that last 18 mos - it like being addicted to crack - you "feel" you're happy - and think it's a great deal !

testknight

Advance Auto, fortunately, provides new replacement, no charge for 3 years after purchase (its not like a tire warranty, its straight swap). That's why I bought it there for $144 (after discounts) vs other options. Buying from dealer is just plain dumb, IMO. Where would u buy?

CD

Gill Senderov

https://www.samsclub.com/p/auto-grou...ee/prod9510087

Gill Senderov

alternatively here, where your warranty will be 4 yrs instead of 3. Excellent battery & don't forget to use the 10% coupon.
https://www.batteriesplus.com/productdetails/sli49agm

testknight

Thanks, I'll look into those in future as options. to be fair I've used Autozone or Advance for most of my cars over the years and this is the first that I ever had that I ever needed to swap while still under warranty. At end of day, I usually get the cheapest with same specs/size (not saying that's the way to go, but has never been a thing for me).

I got the battery in wife's car today so will be driving it over next week or so and will report back later to verify this did the trick. I was bit hung up on that voltage being so high while running, so was looking at the alternator pretty close at first (still seems pretty hi though compared to other platforms I've worked on). I appreciate the input from everyone to nudge me away from that.

One last comment, I mentioned that the battery replacement was super easy...in terms of complexity it definitely is...just push seat all the way forward, pull back carpet (may need to cut it a bit) pull of plastic coverings/vent, pull of vent line, undo terminal clamps, take out the space bracket at floor of battery compartment, and just pull it out. I would share its not easy in other ways. The battery is heavy and its in a position where you have no leverage so really just use your arms to get it out and back in. Unfortunately you can't just grab the handle and pull it out (which then it would have been easy) as lifting it with the middle handles don't tilt it enough to pull it out. I'll spare more detail here but would suggest that unless you have some strength, you may not be able to get it out (if I thought on it more I may have figured about a way to make it easier). I'll put my strength at above average (used to lift a lot, don't do it nearly as much anymore at 48 years old) but could see some people just not being able to get it out. Next time, if there is one, I may consider if I could have done it another way.

geniushanbiao

I have bought like 10 batteries from Autozone or Advanceautoparts and the shortest life one lasted for 3.5 years and that was due to that my wife (girlfriend at that time) left the headlights on and drained the battery for like 3-4 times that basically killed it. There are lots of things to take care of to make the most out of them, including clean the terminals and connectors.

geniushanbiao

Sam's club offers 36 months replacement as well and it requires membership.

BlownV8

Got mine from them and it was the cheapest source with the best warranty.

chsu74

Most car batteries are only made by a few manufacturers. OEM porsche battery is made by Johnson Controls which is also the same as Walmart Platinum Plus AGM. The similarity is down to the exact shape and design if the exterior battery case.

geniushanbiao

This is a well known topic but it's a little complicated. As a matter of fact most batteries we buy from major suppliers are made by either Johnson Controls or Exide. However it doesn't mean they share the same quality. Some of them are simply same products branded differently but some are actually from different product lines. MB new cars are equipped with Varta batteries. Varta is a child company of Johnson Controls but they produce different products. I have to say that Varta batteries have better quality than others generally, but I don't think it worths the 2-3 times price difference, plus the dealers don't give as good warranty to the Varta batteries compared to others.

chsu74

If a battery cost 3X and only lasts twice as long, then it makes little economic sense for DIYers. I find trickle chargers to extend battery life regardless of quality. You can abuse an expensive battery driving short trips with AC or heated seats and it will not last. Trickle charging will help recharge and rebalance battery health.

geniushanbiao

Exactly but there are much less DIYers than laymen who don't know how to turn a bolt. I got the CTEK charger that's basically the same thing as the official MB charger and it has battery maintenance function specifically designed for AGM batteries.