[agentorange]

I think the title says it all. I need a bit of a top up as I've been using the car very little (working from home) and even when I do it's only short runs.

[dangerus_car]

yes, you can

[im_an_alien]

Actually you're supposed to connect the battery charger while the battery is still in the car! Most modern (consumer level) chargers are designed to charge the battery in situ, no need to remove it.

[sasto]

Sorry for interrupting - I have to activate my profile

[agentorange]

Originally Posted by sasto

Sorry for interrupting - I have to activate my profile

Yep, been there, done that.

[agentorange]

Sounds good. I assume I connect direct to the battery in the trunk rather than the jump start terminals.

[E30M CW]

No need. Connecting to the charging posts in the engine bay works just fine.

[sasto]

Originally Posted by agentorange

Yep, been there, done that.

[Skyhigh]

andysantoro
Did you know your car comes with a User Manual? It even tells you how to charge the battery!

You do NOT connect directly to the battery in the trunk! That is dangerous as it goes around the battery management electronics! You use the provided terminals in the front! (Also detailed in the user manual)

https://f30.bimmerpost.com/forums/sh...11&postcount=1

[im_an_alien]

Originally Posted by agentorange

Sounds good. I assume I connect direct to the battery in the trunk rather than the jump start terminals.

Nope, use the terminals under the hood

[Billfitz]

In winter, when the weather is cold and I only drive once or twice a week, I use a maintainer to extend the battery life. I rigged the maintainer so I can plug it in without opening the hood.

Connect wire to the charging posts, with an in line fuse as close as possible to the positive post. You can unscrew the posts to fit U connectors beneath them.





Run the wire to the lower grille, put a quick connector there, zip tie the connector to the grille. Plug the connector from the charger in there.
Use split loom plastic tubing to wrap the wire (first photo), incorporating as much of the existing wiring as well to protect it.

[agentorange]

What charge rate should I use? My charger has 2A, 4A, and 6A rates.

[Billfitz]

2A for maintaining.

[thejeremyman9]

Originally Posted by agentorange

What charge rate should I use? My charger has 2A, 4A, and 6A rates.

You can also do some back of the envelope math based on how low you think your battery is and how quickly you need to charge it, if you are going for charge and not maintain (based on amps, and amp-hour of battery)

[Skyhigh]

Originally Posted by agentorange

What charge rate should I use? My charger has 2A, 4A, and 6A rates.

It doesn't matter - that's where intelligent battery controllers kick in. Use the highest setting. As soon as the battery is charged (to 80% which is the max the car will allow you to), your charger (assuming it is not from the 90s) will stop charging too. It will restart in e.g. 10 days as this is how the maintainer function works.

If you select 2A as suggested, it will just take 3 times as long to charge, until charging is discontinued.

What you should pay attention to however is AGM! Your charger must support AGM batteries and have an AGM setting you typically need to manually select (i.e. higher V for charging).

[Billfitz]

Batteries don't like being either charged or discharged at a high rate, as both result in heat build up. If the battery is depleted to the point that it won't start the car faster charging is a necessity, assuming you don't want to wait for 24 hours or more to get it charged. Otherwise 2A is plenty. My battery is 8 years old, after a short trip it never takes more than 3 hours to return it to a full charge state. Not that I'm concerned about the charging time anyway. A maintainer's main purpose is to keep the battery from excessive discharging, as the car is never fully off.

[Skyhigh]

All that was true in the “good old days”.
Charging current, rate and level is now fully electronically controlled.

Dealerships use high-amp charger/maintainers too.

[agentorange]

Well, a few hours on the charger has definitely livened up the starting cycle. I will do the same to my ML350 tomorrow.

[Qsilver7]

Ditto the comments above…DO NOT connect directly to the battery in the trunk…use the dedicated jump start terminals in the engine bay.

See info from BMW TIS below:

[agentorange]

Going to put the 328d in the garage and charge it some more tomorrow morning. I think the battery has a little ways to go before it is really up there. The ML wasn't as down as I thought it was, but it gets to live in the garage.

[agentorange]

I think I know now why I got the "battery discharged" warning last week. It took over 11 hours of charging at 4 Amps before my charger said "yep, you're good". That's a chunk of charging.

[Skyhigh]

You could have read out the charge level of your battery with BimmerLink or other similar app. For next time