CHARGING A BATTERY
- Thread starter walshypw
- Start date
Henrick
Active Member
Why don't you want to disconnect/remove the battery? That'd be the proper way to do it.
It all depends on the time you have and conditions for it.
The absolutely correct way, which I believe is:
1. Disconenct the battery from the car, bring it inside.
2. If the battery is colder than ambient temps, let it sit inside to warm up naturally.
3. Meanwhile give it a good clean.
4. Open up the cell caps, check water level. All the plates should be submerged. If MIN/MAX marks are visible on the side of battery, ensure the water level is between those. Might need a powerful torch to see the actual water level on the side of battery as that plastic is not very transparent.
5. If necessary, add or remove water.
6. If the battery is totally flat, use a smart charger. Put it in VERY LOW charge current. Less than 1 A if possible.
7. Once the initial state has passed, you can switch to higher charging power. I would not recommend going over 5 A.
8. Check density of electrolyte periodically. It should be 1.28 for 100% charged battery. See the density table to introduce correction factors if needed.
9. Remove from the charge, check the water level, add/remove if necessary.
10. Put the cell caps back.
11. Neutralize the acid spilled on the battery (during charging process). Baking soda + water mix is a good solution
12. Clean the terminals with wire brush or special tool
13. Reinstall the battery into the car.
It all depends on the time you have and conditions for it.
The absolutely correct way, which I believe is:
1. Disconenct the battery from the car, bring it inside.
2. If the battery is colder than ambient temps, let it sit inside to warm up naturally.
3. Meanwhile give it a good clean.
4. Open up the cell caps, check water level. All the plates should be submerged. If MIN/MAX marks are visible on the side of battery, ensure the water level is between those. Might need a powerful torch to see the actual water level on the side of battery as that plastic is not very transparent.
5. If necessary, add or remove water.
6. If the battery is totally flat, use a smart charger. Put it in VERY LOW charge current. Less than 1 A if possible.
7. Once the initial state has passed, you can switch to higher charging power. I would not recommend going over 5 A.
8. Check density of electrolyte periodically. It should be 1.28 for 100% charged battery. See the density table to introduce correction factors if needed.
9. Remove from the charge, check the water level, add/remove if necessary.
10. Put the cell caps back.
11. Neutralize the acid spilled on the battery (during charging process). Baking soda + water mix is a good solution
12. Clean the terminals with wire brush or special tool
13. Reinstall the battery into the car.
This is indeed correct way -- if the battery has removable caps. Many modern car batteries don't.
-Uwe-
Get a decent charger. Many cheap ones will do stupid things like run the voltage up high enough to set fault codes in some modules.
Connect the positive lead lead to the battery's positive terminal.
Connect the negative lead to a chassis ground, not to the negative terminal of the battery. If you connect the negative lead directly to the battery, the car's BEM/BMS will not see the battery being charged and will not be able to properly evaluate the battery's state of charge. Of course this assumes the car has a BEM/BMS, which I would consider pretty likely in an Mk.7.
Not specifically for you, but for others reading this: If the car has the battery in an inaccessible location, it will likely have a dedicated set of jump-start terminals under the hood. It's OK to use those for charging.
-Uwe-
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I was about to recommend the CTEK. I was sceptical about a small device - but they are really good. One 'recondition' charge each year will eek more life out of your battery too.
Remember, distilled water.
Remember, distilled water.