Next Can of Worms – Chargers: CTEK, NOCO or Other?
 

So as I have read in my research on a replacement battery for our X5, it seems that maintenance charging the battery with an external charger is recommended for a few reasons. If I am understanding correctly, one being that the car itself is designed (maybe more accurately programmed?) NOT to fully charge the battery. And this gets compounded if the vehicle is not driven enough, or for long enough on each trip. As a result, I am now down the rabbit hole of research on a charger for this purpose. I understand that AGM batteries require different charge voltages than flooded lead acid, and that it is best to have a charger that has specifically programmed modes for AGM charging. Easy enough, no shortage of these available.

CTEK comes up over and over on the BMW forums, and BMW rebrands a CTEK charger to sell it for twice the price, so it seems an obvious choice. The CTEK MS 5.0 seems to be the same charger BMW rebrands, and the CTEK MUS 4.3 also seems to have a popular following. Other than the ‘test’ functions of the MUS 4.3, the charge functions appear to be identical, both having 4.3 A Max outputs.

NOCO also has some chargers of interest, the one being most closely comparable seems to be the NOCO Genius 5, which charges at a max rate of 5 A. There is also the NOCO Genius 2D, that Charges at a max rate of 2 A. I like that both are weatherproof and designed to be ‘installed’ in the vehicle. The Genius 5 has most of the same features of the CTEK, but the 2D is a bit more basic.


The noted battery guru on Bimmerfest (yes, Doug) cautions repeatedly about not charging at more than 4 A. The CTEK he uses charges at a marginally higher rate, and the GENIUS 5 at again, marginally more. I’m not sure I understand where this warning comes from, as it is seems AGM batteries can accept charge rates much higher, and I have to assume the car itself can charge the battery at much higher rates when called for.

I would love to understand this better, but from what I can find online, it seems like the general rule of thumb seems to be to charge at about 10% (.1C) of the rated Ah capacity (about 10.5A for a 105 Ah battery), and that you can charge AGM batteries as high as 30% (.3C) of the rated Ah capacity (31.5A for a 105 Ah battery) occasionally, but not recommended to do so regularly. So throwing out the max permissible and sticking with the typically recommended 10% of Ah guideline (.1C), it seems like up to 10 A would be safe on a regular basis. So is it something in the BMW electronics that risks damage at higher rates?

I have used Deltran Battery Tenders (1.25 A) for decades now on motorcycle batteries as well as an older classic vehicle that doesn’t get out much, with great success. But they don’t seem optimized for AGM, and like they are a step behind the CTEK and NOCO offerings. Maybe there are other charges out there I should be considering as well, I dunno..

I like the idea of mounting a NOCO under the hood, permanently hooked up, so I just have to plug it into an extension cord (our X5, sadly, is not garage kept), and I am leaning toward the NOCO Genius 5, but this isn’t a requirement. I just want to get the best tool for the job. So I’m all ears everyone..

I've been using BatteryMINDers for over ten years. I recently hardwired a

https://www.batteryminders.com/2012a...acid-batteries

in my Ram 2500 diesel. Before that, used a couple of the older "wall brick" models. I still use those ones actually to maintain an eight-year old Interstate MTP flooded-cell battery and a 10-year old Optima Red Top battery.

When I replaced the original eight-year old battery in my 2011 X5d which had been tended by a BatteryMINDer since my ownership in late 2014, I replaced it with an Odyssey PC1350 battery and purchased their OBC-20A charger/maintainer. My X5 is garage-kept so the Odyssey unit made sense to use.

So, there are some of my recommendations.

I use Pulsetech Xtreme Auto Charger's



https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Shows out of stock in that link but thats the ones I use.


I also have a few of these to use with it :


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Pulsetech Quad Link


This allows me to charge 4 cars on one of the pulsetech chargers.


Ive actually brought batteries back to life with this charger. I have never had a battery go bad thats maintained on it. The oldest vehicle batteries that I have on these charger is over 15 years old now.

A 2A fixed charger will restore pretty much any "dead" 12V automotive battery. I have an ancient Schumacher for exactly that purpose.

No when I said dead I mean DEAD. What the pulsetech chargers do is blast the sulfation off the plates in the battery. You will see it actually floating on the battery acid after using it if it has any. The problem you can run into with a very bad battery is it can make the battery worse before getting better since what you caused to come off the plates can actually settle back in a way that is worse that it was.


Repeated chargings will break it up smaller and smaller but it can be right stubborn on some batteries.


I fixed one once that was so bad I had to pour off the scum from the top and add water back.


The things work. The military uses them on tanks and such. These are the consumer versions. You can buy a new car for what the high end chargers they have cost.


The main purpose for me using them is the maintain those $250 plus batteries I run in the my bmw's. Deka intimidator batteries are not cheap with 5 different cars using them I do not want to risk having to replace them.


I have about 30 cars and trucks total. The ones with these charges have never failed. The ones with the battery tender chargers have had 2 batteries sulfinate.



The batteries that were disconnected but not charged ended up showing 12.3 volts or more but would go to 6 to 9 volts when you opened the door on the cars. So volts but no amps. One wouldnt charge over 6 volts.

I don't understand the limit of 4A when charging the battery.... when the alternator charges it, there's way more current going through to the battery. As the battery charge recovers, the current drops - both in the the external charger and alternator cases.

Can anyone explain...?

Actually the 4 amp limit isnt how much you can charge it at as much as how long you charge it at that amount.


You can charge it at 50amps as long as you dont do it but for so many minutes.


Overcharging a battery causes excessive gassing — the electrolyte gets hot and both hydrogen and oxygen gas are generated. On older vented batteries, the electrolyte could cook away, leaving the plates exposed and ruining them. On sealed batteries, the buildup of gases could cause the battery to burst.


Batteries can be a pain. Trickle charging aka using a low amp charger say in the 1 amp or less will actually harm the battery by allowing plate buildup. Above 1 up to 2 amps is ideal most of the time for long term storage.


On the solar setup I have for one of my houses the charger actually blast the batteries at the start of the charging cycle to "clean up" the build up that can form and then it backs off to a normal charge till the batteries are full. So the thing can range between 50 amps down to less than an amp if they are full.

Another thing to keep in mind just because you have a 100 amp alternator doesnt mean its charging the battery anywhere close to that. The alternator varies based on load. Any serious amperage its making is to feed the cars accessory needs or changing the battery back right after cranking. Most of the time there isnt much of a charge going into the battery itself.

I've never run across this concept. Do you have any links to support this? I often use my 0.8 amp CTEK trickle charger to maintain/top-off my batteries. This would indicate I'm actually harming them. Just curious.

AM.

I've used a Battery Tender Jr on my E53 (non-AGM batteries) for the last 18 years. It's almost always plugged in. Batteries have lasted up to seven years. I have an adapter on the B+ terminal, coming out to the right of the wiper, in the engine bay to make plugging and unplugging simple and fast.