Battery charging

[ColinMerc]

Only doing a short run to shops once a week until this C19 over... Is this enough to keep battery fully charged, or do I need a longer blast every few days?

 

[alecmascot]

How far is "the shops" ?
My W204 stood for a week until yesterday and it started fine. I drove "round the block", 30 - 40 mph, for 15 minutes.
I expect the charge to last for another week.

 

[Chrishazle]

Rather doubt it, and I found out the hard way that MB's can be finiky about battery voltage - about 3 weeks ago wife wanted to drive to the surgery, all seemed normal (opening doors etc) until she tried to start the car, no reaction at all to Pos. 3 with the key. Battery condition tester said battery 50% charged.

Do you have power available where your car is parked? If so I'd get a battery conditioner and have that connected while the car is parked up. Lidl/Aldi do cheap ones, there's one on Amazon https://www.amazon.co.uk/dp/B009A83P1E/?tag=amazon0e9db-21
or the most popular more expensive choice is CTEK.

 

[ColinMerc]

How far is "the shops" ?
My W204 stood for a week until yesterday and it started fine. I drove "round the block", 30 - 40 mph, for 15 minutes.
I expect the charge to last for another week.

2miles return

 

[ColinMerc]

Rather doubt it, and I found out the hard way that MB's can be finiky about battery voltage - about 3 weeks ago wife wanted to drive to the surgery, all seemed normal (opening doors etc) until she tried to start the car, no reaction at all to Pos. 3 with the key. Battery condition tester said battery 50% charged.

Do you have power available where your car is parked? If so I'd get a battery conditioner and have that connected while the car is parked up. Lidl/Aldi do cheap ones, there's one on Amazon https://www.amazon.co.uk/dp/B009A83P1E/?tag=amazon0e9db-21
or the most popular more expensive choice is CTEK.

cheers!

 

[DSM10000]

2miles return

Then you are taking more out of the battery than you are putting in.

 

[Chrishazle]

I can attest to the benefits of using a battery conditioner, I've been using one on my weekend toy for many years - and in my working days it would be parked up for anything between 2 weeks and 3 months, but always started first time, plus the battery lasted far longer than before I had the conditioner. 968 coupe I bought in Nov 98 at 4 1/2 years old had already had 1 battery change, 2 years after I bought it I had to change the battery again - and got the conditioner. 10 years later that battery was still in the car and going strong, so the £40 the conditioner cost me saved me possibly 2 replacement batteries at about £100 each - and the replacement battery for my S204 cost £158 last November!

 

[BlackC55]

Alternators are not good at charging low batteries. Charge it with a charger if you can.

 

[Deleted member 149005]

As a rule of thumb, I was told you need c30 mins driving to recharge a battery from a cold start, assuming it starts first time.....

Of course there are many variables - other electrical draws (wipers, air con etc) and the output of the alternator...

 

[190]

I think you should charge the battery. I'm doing something similar with a 7 mile round trip once a week. I charge the battery and it takes 1 - 2 hours to get back to full charge.

If you start a journey with a fully charged battery and the engines starts instantly then the 2 miles is more than enough to put back what the starter takes out. Last time I did the calculations it came out at a few hundred yards

The starter isn't the issue but there are several other factors:-

Unless you use a lot of revs the car will most likely not have finished the previous journey with a 100 % fully charged battery because the smart alternator won't allow it to.

Every time you open a door the car wakes up and pulls something like 8 amps from the battery for several minutes so if you access the car between journeys that won't help.

The alarm current is small but it adds up over 168 hours in a week. I only have accurate figures for my old car which drew 5.7 amp hours per week. Newer cars may be less but it's no surprise that it can need up to 2 hours on the charger.

Try it. Put a charger on your battery and see how long it takes to reach full charge.

 

[Chrishazle]

Since having my battery changed under warranty last Sunday I've kept my battery condition tester attached and visible. In the week the car has had the follorwing use :
Sunday Halfords to home, 8 miles.
Tuesday 3/4 mile to village surgery, 1 mile home
Thursday 3/4 mile to village surgery, 1 mile home
Today 4 miles to Tescos, 4 miles home
so 7 starts and just shy of 20 miles driven - and the condition tester gave a couple of brief flashes of the half charged light before going back to the green fully charged light, so I've now got the sharger on it on fast charge for a few hours then will drop it to slow charge overnight (or swop the charger for my conditioner).

Battery is a 100AH Yuasa identical to the original that I had replaced in November.

 

[GLK]

I'm facing a prospect of going to the office maybe once a week, or a fortnight more likely - a 28 miles round trip, which was okay to keep the battery going, when done five times a week ...

I also seriously dislike driving to the shops nowadays (as in not going to - village shop will suffice), so today I fitted a Maypole charging connector, the charger - 4A Smart MP7423 - arrived yesterday from Amazon.

I've tested it already - works fine, as far as I can see: up from 12.7V ah hour ago to 13.0V.

I fitted a new VARTA Silver Dynamic battery in Sep 2017, and want to keep it in its best condition for as long as possible, so not going to risk it relying on an occasional drive.

 

[ColinMerc]

I think you should charge the battery. I'm doing something similar with a 7 mile round trip once a week. I charge the battery and it takes 1 - 2 hours to get back to full charge.

If you start a journey with a fully charged battery and the engines starts instantly then the 2 miles is more than enough to put back what the starter takes out. Last time I did the calculations it came out at a few hundred yards

The starter isn't the issue but there are several other factors:-

Unless you use a lot of revs the car will most likely not have finished the previous journey with a 100 % fully charged battery because the smart alternator won't allow it to.

Every time you open a door the car wakes up and pulls something like 8 amps from the battery for several minutes so if you access the car between journeys that won't help.

The alarm current is small but it adds up over 168 hours in a week. I only have accurate figures for my old car which drew 5.7 amp hours per week. Newer cars may be less but it's no surprise that it can need up to 2 hours on the charger.

Try it. Put a charger on your battery and see how long it takes to reach full charge.

Do you charge once a week ?

 

[Chrishazle]

If the car can be safely locked and alarmed (like in a garage) with the conditioner connected, just leave it like that until you need the car. I've done that for probably 20 years now with our weekend toy, leaving the toy untouched for anything from 2 weeks to 3 months (working away/overseas). I've also discovered that with my S204 I can close the boot lid over the cable of my extension lead, so like right now the car is on the front driveway where she lives, conditioner on but car locked and alarmed, extension lead under the locked side gate to an outside earth leak protected weatherproof power point!

 

[Gazwould]

Outside charging I've got a plastic box that covers the extension reel .

 

[190]

Do you charge once a week ?

Yes, always have done for the 5 years I've had the car. At the moment it's only being used once per week anyway.

 

[Stratman]

Serious question for those who have fitted a permanent connector and leave it charging.

Have you any failsafe system to prevent driving off with it still connected?

 

[pmcgsmurf]

Serious question for those who have fitted a permanent connector and leave it charging.

Have you any failsafe system to prevent driving off with it still connected?

Only procedure: If E55 is cable Off

 

[GLK]

Serious question for those who have fitted a permanent connector and leave it charging.

Have you any failsafe system to prevent driving off with it still connected?

My battery is under the driver's feet, so the charger is [almost] blocking the pedals ...

The connector is tiny, and comes with a safety cover, so should be alright under the seat:

 

[Dave Richardson]

I use a Ctek charger on our CL203

Great pictures & description Dave GLK