ICE Trickle Charger Part 2
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2nd Gear
Joined: Sep 2025
Posts: 55
Likes: 24
From: Colorado
Trickle Charger Part 2
After an exceptionally warm Fall, we are finally getting some cold temps in the teens and twenties here in Colorado.
I decided to break out my trusty Diehard trickle charger/maintainer, as I don't drive my Cooper frequently.
I've used this on many cars in the past that don't get driven frequently. Perfect for keeping the battery topped off in the wintertime....
The battery in the 2025 Cooper S 3 door hatchback is hidden under a protective plastic cover.
There is an exposed positive terminal on top of the cover under a red cap, and a ground terminal attached to the frame, not directly to the negative terminal of the battery.
Just to be on the safe side, I asked CoPilot AI about connecting the charger to this negative terminal connection.
Of course, there is no problem with doing so and, in fact, it is recommended over connecting directly to the negative terminal of the battery.
However, much to my surprise, my old Diehard charger/maintainer is not recommended for my Mini... Why? Our Minis are equipped with an AGM (Absorbent Glass Mat), not a standard lead‑acid battery.
Okay, what is the difference you ask (I did)?
AGM batteries are sealed, spill‑proof and use fiberglass mats to hold the electrolyte, giving them better power delivery and vibration resistance.
Standard lead‑acid batteries use liquid electrolyte, need ventilation and offer lower performance but cost less.
AGM batteries need a special trickle charger because their sealed design requires precise, lower‑stress voltage control to avoid overcharging and permanent internal damage.
An old style trickle charger/maintainer is not recommended for AGM batteries.
I learn something new every day!
There are several very good AGM chargers recommended for these AGM batteries.
I ordered a NOCO Genius1 for a very reasonable price and will use that when it arrives.
The photo below shows the top of the battery....
I decided to break out my trusty Diehard trickle charger/maintainer, as I don't drive my Cooper frequently.
I've used this on many cars in the past that don't get driven frequently. Perfect for keeping the battery topped off in the wintertime....
The battery in the 2025 Cooper S 3 door hatchback is hidden under a protective plastic cover.
There is an exposed positive terminal on top of the cover under a red cap, and a ground terminal attached to the frame, not directly to the negative terminal of the battery.
Just to be on the safe side, I asked CoPilot AI about connecting the charger to this negative terminal connection.
Of course, there is no problem with doing so and, in fact, it is recommended over connecting directly to the negative terminal of the battery.
However, much to my surprise, my old Diehard charger/maintainer is not recommended for my Mini... Why? Our Minis are equipped with an AGM (Absorbent Glass Mat), not a standard lead‑acid battery.
Okay, what is the difference you ask (I did)?
AGM batteries are sealed, spill‑proof and use fiberglass mats to hold the electrolyte, giving them better power delivery and vibration resistance.
Standard lead‑acid batteries use liquid electrolyte, need ventilation and offer lower performance but cost less.
AGM batteries need a special trickle charger because their sealed design requires precise, lower‑stress voltage control to avoid overcharging and permanent internal damage.
An old style trickle charger/maintainer is not recommended for AGM batteries.
I learn something new every day!
There are several very good AGM chargers recommended for these AGM batteries.
I ordered a NOCO Genius1 for a very reasonable price and will use that when it arrives.
The photo below shows the top of the battery....
Last edited by BULLPUP01; Dec 29, 2025 at 09:36 AM.
2nd Gear
Joined: Nov 2021
Posts: 96
Likes: 39
From: York, PA USA
The NoCo Genius 1, one amp charger is an excellent tool. I have had it along with other NoCo chargers for several years and they all work great. It is designed to work on all battery types. Hook it up and forget it. The one amp model is especially great for small lead acid batteries like lawn mower, motorcycle, snow blower, generators etc.
Thread Starter
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2nd Gear
Joined: Sep 2025
Posts: 55
Likes: 24
From: Colorado
Good to know...
This NOCO 1 amp charger probably would not work well to charge a discharged battery, but as trickle/maintainer charger in the Winter, it should do well.
I like the 'Hook it up and forget it'... exactly what I need...
This NOCO 1 amp charger probably would not work well to charge a discharged battery, but as trickle/maintainer charger in the Winter, it should do well.
I like the 'Hook it up and forget it'... exactly what I need...
Thread Starter
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2nd Gear
Joined: Sep 2025
Posts: 55
Likes: 24
From: Colorado
Received the NOCO Genius 1 trickle charger... perfect.
It will charge and maintain a variety of different types of batteries, including AGM batteries, which is what we have in our 4th gen Coopers.
Simple to use, well engineered and it works perfectly.
Highly recommend this brand and model should anyone need a charger maintainer for their car....
It will charge and maintain a variety of different types of batteries, including AGM batteries, which is what we have in our 4th gen Coopers.
Simple to use, well engineered and it works perfectly.
Highly recommend this brand and model should anyone need a charger maintainer for their car....
Yep, we carry them. Glad it worked for you.
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MINI Guru/ MINI Owner Since 2004 | NEW Lifetime Part Replacement | Local Pickup
Milltek | Genuine MINI | Forge Motorsport | NM Engineering | ECS Performance | M7 Speed
Customer Service Hours: 8am-8pm EST|Sales Team Hours: 8am-11pm | SAT 10am-7pm 800.924.5172
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