Sics Consolidated Faded Moderns Thread - 2004 BMW Z4 2.2 & 2005 BMW 330i

Talk about your cars etc here. Keep it sort of sensible and on topic please.
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Eddie Honda
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by Eddie Honda »

SiC wrote: Thu Nov 16, 2023 11:37 pm As I said above, AGM ready apparently means you just don't need to add acid to use.
Seems cheap, but then there's calcium VRLA AGMs and TPPL VRLA AGMs.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by AutoshiteBoy »

I thought a battery was a battery and that was it.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

Nope definitely not. Different types require different charge profiles.

Lead acid come major types as flooded, AGM, Gel.
Generally Flooded and AGM used in vehicle starting/leisure. Gel in golf carts/mobility scooters/alarms/etc.

Different cell construction on each. Starting batteries have many thin cells to provide a high surface area - thus high current. This is why high discharge damages these quickly. E.g. using for leisure. Lead acid oxide and breakdown with heavy discharge. Hence thin cells don't have much meat to survive this.

Leisure packs or modern stop/start have thicker cell plates to provide less high current but more longevity.

Deep discharge (e.g. back up batteries in telecoms/submarines/etc) have very thick plates. Much less peak current but far better withstanding deep discharging.

Variations also on plate design. E.g. modern stop/start often uses EFB. These have better tolerance to discharge than a starting flooded battery. Not as good as AGM but much cheaper. I actually read recently they are much better withstanding heat than AGM. So actually a battery in an engine bay is better off with EFB than AGM. AGM doesn't like heat and probably a major reason why you often see them in the back of a vehicle.

AGM need a higher charge voltage than flooded. Gel more than both.

Even charge voltage varies on application. 14.0v or so commonly used on flooded starting batteries is fine for properly charging but long periods (weeks/months) will cook a battery. This is why it's important to have a proper maintenance charger if hooking up for a long period. These drop to around 13.0v when charged to stop the cells cooking. I.e. float voltage.

It's common for emergency backup battery systems to run constantly at that 13v charge voltage. The cells will gas but for the most part can recombine and not lose electrolytes.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

Charging a lead acid is relatively simple. Constant current limit until it hits a set voltage and then constant voltage until the current tails off. Most lab power supplies will do that.

Same charge method as for lithium cells. Except it's critical on those to not exceed a maximum voltage. 4.20v was the accepted maximum voltage to at which start reducing current on the pouch Lithium-Polymer type cells. However I think many applications do it lower to lengthen the life of the pack. Cylinder cells I think are lower too. Lithium cells don't like being fully charged and will damage them.

Go above 4.25v (so literally 50mv) and you'll start the cells breaking down then puff up. Much more and you risk fire.

Lead acid can tolerate higher voltage over charging. Handy when fully charging a pack as you can over charge the ones that fill up first. This is why you get six cells in a car battery but only a positive and negative terminal to worry about.

Lithium packs have individual tap offs on each cell. This allows if one cell is fully charged then it bleeds off power to prevent it being over charged while the others are being charged. Look at your Makita/Milwaukee/DeWalt/etc pack and you'll see positive /negative main terminals and the additional connector. That extra connector is taps into individual cells.

Nicad/ni-mh are different again. These tolerate over charging well. Nicad much more than ni-mh. This is handy as they're a bitch to charge.
Their charge voltage barely changes as they charge. So detecting when they're full is difficult.
Primary methods are delta-temperature and delta-voltage. In voltage you're looking for a peak and then a slight drop down. However this difference is tiny for some cells (NIMH especially) and easy for a control circuit to miss. Temperature you're looking for a steady state as it's charging. When fully charged the temperature will rise really quickly and that is when to cut the charge.

Alternatively if you charge at a lower rate on nicad/nimh, you can basically keep them over charging all the time. Excess energy get turns to heat. They recombine inside if the current is low enough and doesn't kill the cells (instantly at least). Very wasteful on power but makes the circuit really simple. This is what a lot of consumer goods do over the years - e.g. house phones and such. Does damage the cells a bit though and a few years doing it constantly will kill them.


Anyway there is loads more on batteries but that's the basics in using them.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

Battery arrived this morning (plus our fourth fridge in a month but that's a different side quest). This was £32 and the cheapest I could find. Because I ordered from Tayna it arrived today on a Saturday.
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Voltage looked good out of the box.
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Stuck it on charge anyway.
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Cleaned out under battery tray to find ... Rust 😱
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Cleaned and dried that out and spolshed some metal enamel down there. I tried red oxide spray but couldn't get the angle. Then heat gunned it to give a chance to dry. As usual I'm messy with paint but can't see it here anyway. 🤷‍♂️
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Gave up waiting for the charge to say full. It had been on for a few hours so only at a float charge point and if already full, might take a while to detect full. New battery terminals didn't look healthy so gave them a scrub down with sandpaper.
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This came with nuts instead of threaded terminals. A bit of a pain to get into place to then do the terminal clamps up. So used a bit of blue roll to keep them up and in place. Then long noes pliers to pull it out once the thread had caught. 
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Then simply a case of bolting it all up.
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Realised the wire above the air intake was in the wrong place. So move it back to where I think it should go. Probably disturbed when the windscreen was replaced last. (It's not an original screen)
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Dash warning cleared itself. Cleared the code on the module and checked the battery was still reading good on the battery control module. 
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Done! Super easy job.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by Eddie Honda »

SiC wrote: Sat Nov 18, 2023 2:07 pm Cleaned out under battery tray to find ... Rust 😱
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Are you still sure you don't want that box of Swans?
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

Nope still good. Only a £32.99 battery. Not exactly a big spend.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by Hooli »

Little sections of washer hose under the nuts in the terminals is what I do. Lasts the life of the battery too.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

This explains why the lights seem a tad low.
The ball joint on the top piece to the bracket is seized up completely.
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Fixed*
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When I get time I'll get the bracket off the suspension arm, free up the ball joint and weld the bracket back together again.
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Re: Sics Consolidated Moderns Thread - 2003 Mercedes-Benz E320 Estate

Post by SiC »

This car isn't one that you can really love, however I do really like it. Something about it feels like a really nice place to be and chills me out. 
Spent a hour or so giving it the wood a good polish inside. Also run it over the trim to clean some scuff marks off.
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Also degunked the soft touch on the light controls. Elbow Grease works really well here and used it on a Clio 172 to sort the same problem. I think this is the only part that has this soft touch on. 
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Definitely nicer to touch and use now - even though you can tell why Mercedes put it on. Without the finish it looks a bit AliExpress knock-off now. But at least you don't stick to the controls now. 
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