Batteries

[BradC]

While I was doing the HPFP the battery was sitting in the garage for 6 days. When I put it back in the car I had to jump start it. I also had to jump it after a couple of days camping over the Christmas break, so I decided it was time for a new one.

The battery in the car was a Cobra MF88H, which looks very much like a re-badged Supercharge. So I replaced it with a new Supercharge MF88H. The old battery had a broken seal on the -ve terminal and it bred corrosion, so I wasn't too unhappy to get rid of it, and I got the new one at Autobarn during a 30% off sale. Win.

I charged the old battery up fully and gave it a capacity test using 2A load. By rights it should have given me somewhere in the order of 80-100AH at that load . It died at about 20AH. So down to ~25% of its original capacity.

It had no problem starting the car if it was charged up, it just wouldn't do it for very long or it'd go flat pretty quickly over a couple of days.

Wish I could decode the date code on it. It'd be interesting to see how old it is (I've only owned the car for about 29 months).

[loanrangie]

i'm a fan of the supercharge batteries and will most likely get the same when my OE LR battery dies.

[DiscoJeffster]

I put the Varta AGM into my D4 but at $500, I can get two non-AGM supercharge. I bet I’d get longer from two Supercharge than one AGM. My AGM is now 26 months old and I’m already seeing signs of a loss of capacity.

[kero]

I put the Varta AGM into my D4 but at $500, I can get two non-AGM supercharge. I bet I’d get longer from two Supercharge than one AGM. My AGM is now 26 months old and I’m already seeing signs of a loss of capacity.

I just put a Delkor AGM in last Friday $370 fitted and $35 of that was for the reset

[scarry]

I just put a Delkor AGM in last Friday $370 fitted and $35 of that was for the reset

That is the one my Indie now uses.

As for Supercharge,we find in our vans they generally last 3yrs and a month or two,thats it.One of my brothers has replaced two in his Honda,in the last 2 yrs,both under warranty.

i actually had to replace the Supercharge in the van i drive on Saturday,3 months out of warranty.

The JLR one in the D4 is an Exide AGM battery,its actually 6 yrs old,but has been in the vehicle almost 5 yrs,fitted by LR under warranty.It is just about shagged and needs replacing before our next trip away.

The D4 battery doesn't get used a lot,so gets a much harder life than the Supercharge batteries in our vans,as they are on the road,fully charged all the time.

[BradC]

The JLR one in the D4 is an Exide AGM battery,

Interestingly enough Exide & Supercharge come out of the same factory. I looked at the Exide before I bought the Supercharge.

I'll be watching this one carefully. The last 2 Supercharge batteries I bought lasted 5 & 6 years respectively but they were in 4 cylinder Petrol vehicles that are much easier on the battery than the D3.

I've owned the old one for ~29 months and it was looking fairly aged when I bought the car. Admittedly it doesn't have a Supercharge badge on it, but the spec plate is the same, the stamped numbers look the same and it's an identical moulding.

[letherm]

Mine's the original oem. Bought the car new in Nov 2013 so I must be getting close to needing a replacement. It has a lot of short trips so I use the Ctex 5 amp ?? charger occasionally. I am surprised it has lasted this long and would be quite happy to replace it with another the same as the original. Obviously don't want to buy off a dealer. Anyone know what the oem is or its equivalent so I'm prepared when I do need to replace?

Martin

[BradC]

. It has a lot of short trips so I use the Ctex 5 amp ?? charger occasionally.

That makes a huge difference in keeping sulphation at bay and is a good way to make a battery last longer.

[ATH]

The OEM in our 2016 D4 has just been replaced under warranty. We kept getting the "Low battery, start engine" warning even after the Ctek said it was fully charged and although I got good advice from members here, I left it to the stealer to fix and they changed it.
I'm quite happy with that.
AlanH.

[letherm]

That makes a huge difference in keeping sulphation at bay and is a good way to make a battery last longer.

It was advice on this forum that sent me down this route.

Certainly seems to have been good advice. [bigsmile1]

Martin

[DiscoJeffster]

That makes a huge difference in keeping sulphation at bay and is a good way to make a battery last longer.

I have a cal entry and at minimum once a month the ctek 7000 goes onto the car for 24 hours.

[BradC]

Just to round this out I did another 2 charge/discharge cycles, and it's taking about 24AH to charge and giving about 19.5-20AH to the load. That's about where it should be.

The battery is down to ~25% of its actual capacity but was perfectly capable of keeping the vehicle running provided it was driven a couple of times a week.

[Chops]

[biggrin]

[Eric SDV6SE]

Must be jinxing things BradC, I had the "charge system fault" come up tonight, still drove home fine, the battery is now on the charger, still have to get the code out of the car, but suspect it's the alternator calling it a day after 188,000kms. Car has run fault free for over 10 months.

[BradC]

Car has run fault free for over 10 months.

It's pretty sad when we get excited about the number of *months* between faults.

[Eric SDV6SE]

It's pretty sad when we get excited about the number of *months* between faults.

Haha, can't say I'm excited, but I get your point.

I should qualify that statement in that the car has not ever "simply stopped". There's always ample warning and so far in 5 years of ownership has ALWAYS gotten us home safely.

For that I applaud the error messages and info system, it allows you to have a place to start fault finding from.

[Sven94]

Re battery date code.. post what you have got.

also google will help to decode it if I cant.

[BradC]

Re battery date code.. post what you have got.

also google will help to decode it if I cant.

Existing battery was : 5051941

New battery has 2. 722358535 / 1183711

[DiscoJeffster]

Varta stamp their manu date on the lead terminal. I found out my Audi car battery was 11 years old from that!

[scarry]

The old wet cell supercharge in the S1 in my sig is 14 yrs old.

Kept on charge a lot,it only gets a run every month or so.

i ended up replacing the battery in the D4 with an Austral battery,AGM.

It was six yrs old by the date code,and had been in the vehicle for 5 yrs,a genuine JLR battery,replaced when the vehicle was under warranty.

I have a cig lighter voltage display,and it was sitting around 12.2 to 12.3 after a good overnight charge with the C tech,so i knew it was a bit tired.

It now sits on 12.7V,all the time.

Apart from the weight,the battery was pretty easy to change.

[DiscoJeffster]

So I spent a lot of time playing batteries and IID while I was on a recent trip to Exmouth and back caught out in poor solar weather. The D4 is a trick beast when it comes to voltages.
The IID can show you the battery voltage (the voltage applied to the battery by the BMS), battery current (current being consumed or being drawn into it (charging)), alternator current (everything sucking its life), State of charge, and body battery voltage (voltage as shown to accessories etc).
I noted that it charges the battery as per a battery charger with high voltage being applied, lower during absorption etc. These voltages did not reflect the voltage displayed in cabin. Interestingly the in cab voltages fluctuated as has been said before, with them rising on decel presumably to take advantage of fuel saving.

What I took away was that you can’t assume the in cab voltage has any reference to the battery. When the battery was charged (0A inflow), the battery voltage was maintained at 14V yet the in cab voltage was 12.2V.

Also it showed that over 24 hours of driving my 2.5 year old AGM could not get higher than 84 percent SoC on the car. I’ve yet to try and Ctek it and check to see what it reports after a Ctek charge.
All very interesting.

[BradC]

Interim update for the MF88H after 1259 days (3.45 years) in service.

I got bored/interested, so I disconnected the battery and charged it at 14.8V until the current dropped below ~200mA (it's full mate). Let it sit for an hour or so and then commenced a constant current discharge test. The battery is rated at 90AH (C20) or an RC of 160 Minutes. If I conflate the 2 (90AH @ 4.5A & 66.6AH @ 25A) that gives a Peukerts exponent of about 1.17 for a new battery, which this isn't.

The problem I have is when I tested the original cast-off back in 2019, I tested at 2A to 10.8V. Thats a C45 rate, and with the Peukerts exponent means the battery should show ~102AH (which it didn't because it was ****ed). Back then it returned ~20AH. So it was down to 20% of new and still *serviceable.

So, this time I'm testing at 4.5A (C20) to a cut off of 11.5V because Supercharge says "don't discharge below 11.5V". Now I recently characterised ~20 UPS batteries between 7 & 55Ah and reviewing the logs there's maybe 5-8% available between 11.5 & 10.8V on a really generous day. Additionally it's cold outside (average temperature over the test has been 13C) so I'd expect a best case of ~81AH (5% for the high cut off and 5% for the low temp).

I've had 3 "severe discharge" incidents where it wound up below 9V due to "operator error" over that time, but nothing catastrophic, so this should be pretty "typical". I figure if I see 50% (40.5AH) after 3 and a half years I'm probably doing ok and should be good for another year or so.

*where serviceable meant it'd start the car after a few wakeups but no more.

It sustained 4.5A for 8 hours 50 minutes for a total of 39.698AH (close to my target). It got very close to starting the car, but due to the low voltage the car wouldn't engage the glow plugs and it was cold this morning. It spun it over for quite a while but wouldn't fire.

I reckon it'll do me for another year but I might start keeping my eyes on the sales.

180910

[BradC]

48 and a half months (1482 days). Down to 30.7 AH. Not seeing any issues yet, but it does sound like it's turning over a bit slower on a cold morning. the discharge test behaviour is odd. The voltage bounces around +/- 200mV once it gets right into the meat of the discharge. That's why the curve is fuzzy and there is 4142 data points in the test. I've never seen that before. The test in September had 51 data points (it only logs a point if the voltage or current changes). The internal resistance must be increasing, because as soon as I put the charger on it jumped up to ~13.4V at 10A.

185106

Haven't been watching the sales, but I suppose I should really start doing that.

[drivesafe]

Hi Brad, have you by any chance carried out a Maintenance Charge routine at all.

The reason I ask is that your battery is still showing a decent CCA behaviour but as you stated, the voltage jumping around like that is a bit strange.

[BradC]

Hi Brad, have you by any chance carried out a Maintenance Charge routine at all.

Yep, for the last week the car has been backed into the driveway and straight on charge every time I got home. That's what prompted me to re-test after I started to see no improvement in the charge behaviour.

I charge using a 10A bench supply with reasonably accurate metering. It took about 5 days for the float current to gradually drop to ~80mA, and it certainly recovered faster after each drive. I probably should have done a test before I started, but the reality is at > 4 years in a car where it's the only battery it lives a relatively hard life.

Bulk charge at ~4A, absorption at 14.8V and float at 13.8V. Temp has been cool enough to not need to apply much compensation to the voltages.

[josh.huber]

I have quickly read through this.. So I may have missed a point or two.

I had a supercharge mf88 in my d4. I used to put them in everything (still do) it was excellent. But it always had a resting voltage of 12.3v even when not in the car.. I tested it multiple times and it passed on CCA. Didn't do a AH test. I changed it out of fear it's now at dads and still going as a battery for his pump on his sprayer.

I'll be going back to one when my ss88 fails me.

[drivesafe]

48 and a half months (1482 days). Down to 30.7 AH. Not seeing any issues yet, but it does sound like it's turning over a bit slower on a cold morning. the discharge test behaviour is odd. The voltage bounces around +/- 200mV once it gets right into the meat of the discharge. That's why the curve is fuzzy and there is 4142 data points in the test. I've never seen that before. The test in September had 51 data points (it only logs a point if the voltage or current changes). The internal resistance must be increasing, because as soon as I put the charger on it jumped up to ~13.4V at 10A.

185106

Haven't been watching the sales, but I suppose I should really start doing that.

Been racking my brain about your graph as I have never seen a battery behave like that.

I am not ruling the battery out as the cause, but and just a suggestion, even though you are probably connecting your load, for the test, directly to the battery's terminals, have you checked all your cable connections, particularly earth connects?

Or, and this might be more feasible, could you have a relay oscillating ( continually cutting in and out ) and the reason I suggest this is because your first test had no initial negative spike ( for want of a better name ) and while the second test has that initial negative spike and then as the voltage dropped, you got that oscillation with about a continuous and comparatively even 3 second cycle?

[BradC]

Yeah, it's certainly an odd one.

The first test I let the battery rest for an hour. The second I didn't.

The load device is a SykyRC BD200 electronic load (up to 20A or 200W whichever comes first). It connects directly to the battery terminals with decent size croc clips and has nice short fat cables. In this instance it was only imposing a ~4.5A load.

I wrote some custom software that sits on a laptop to drive it. So aside from not letting it rest for an hour between charge and discharge the test methodology was identical.

[drivesafe]

Do you test the battery while it is connected or do you disconnect one of the leads?

[BradC]

Always disconnected. Can’t get an accurate test when you don’t know what else is waking up.

[BradC]

Well, I've gone and done something I've never done before and bought a new battery before the old one started causing "trouble".

Autobarn/pro have a 20% sale on, so I picked up another Supercharge MF88H. The one in the car is still doing the job, but as the last test showed it's "not as good as it was". The Mrs is taking the D3 for a "girls weekend" out to Southern Cross in June, and the last thing I want is a phone call, so I bit the bullet.

I was going to wait for a 30% sale, but they tend to be later in the year and the extra ~$40 saved didn't seem worth it. The last one was $223 and this one $287. Still for a battery that has lasted > 4 years I'm not unhappy replacing it with the same.

This give me the opportunity to test the new one before I put it in and also try out my new Carbon Pile load tester. I can then similarly torture the old one when I eventually swap them over.

I can't find a date code on it, and it's currently on charge (another thing I rarely get the opportunity to do before putting a new battery in). I'll see how long it takes to really charge up.

[ATH]

I'm just about to fit a new battery as I constantly get the warning coming up even after a decent run. New Delcor AGM has been on charge with the C-Tek overnight. Is there any resetting with the GAP Tool required after taking the old one out and fitting it's replacement?
AlanH.

[DiscoJeffster]

I'm just about to fit a new battery as I constantly get the warning coming up even after a decent run. New Delcor AGM has been on charge with the C-Tek overnight. Is there any resetting with the GAP Tool required after taking the old one out and fitting it's replacement?
AlanH.

Yes. There is a service item to reset the BMS.

[ATH]

That's strange. I plugged in the GAP tool but no warnings or anything else about the battery. Started immediately, had to reset date and time etc. but nothing else.
AlanH.

[DiscoJeffster]

That's strange. I plugged in the GAP tool but no warnings or anything else about the battery. Started immediately, had to reset date and time etc. but nothing else.
AlanH.

There won’t be any warnings but you should still reset the BMS so it charges your new battery correctly.

[ATH]

I'll do that today after I've taken The Cook on her usual trip to empty Woolies food shelves.... :) Thanks for the tip.
AlanH.

[ATH]

I did everything the GAP told me to under replacement battery and a message came up saying 'Operation Succeed' - 'Continue'. I tapped Continue but nothing else happened! Should the message have read 'Operation Successful' instead?
AlanH.

[DiscoJeffster]

I did everything the GAP told me to under replacement battery and a message came up saying 'Operation Succeed' - 'Continue'. I tapped Continue but nothing else happened! Should the message have read 'Operation Successful' instead?
AlanH.

It’s done. Yes, not grammatically correct but it’s sorted [emoji106]

[ATH]

Great. I thought that may be the case. Thanks for that. I did the same thing for the dual battery which I also changed recently.
At the rate I'm spending money I think I may well keep the Disco after all instead of someone else reaping the benefit of it. :)
Cheers.
AlanH.

[DiscoJeffster]

Great. I thought that may be the case. Thanks for that. I did the same thing for the dual battery which I also changed recently.
At the rate I'm spending money I think I may well keep the Disco after all instead of someone else reaping the benefit of it. :)
Cheers.
AlanH.

This is my thinking. I’m probably going to get a daily runner and park up the Disco for touring

[ATH]

I'm thinking of an electric bike to give my left ear a rest. :)
Actually I've been a bit frightened when reading of no new engines available if the worst happens, or the gear changing knob cacking itself through lousy workmanship, but on the other hand it's such s good car to drive and nothing disastrous has happened so I've kept it far longer than I normally do a vehicle.
AlanH.

[josh.huber]

I'm thinking of an electric bike to give my left ear a rest. :)
Actually I've been a bit frightened when reading of no new engines available if the worst happens, or the gear changing knob cacking itself through lousy workmanship, but on the other hand it's such s good car to drive and nothing disastrous has happened so I've kept it far longer than I normally do a vehicle.
AlanH.

If I had the later model with the gear knob. I'd just buy one and keep it in the boot. That way you're sorted and can have someone do the repair if it does go bad.

[ATH]

Good idea Josh but then the only prob you have is finding someone who is willing to even look at a Landie when away from the metro area. Maybe I could do it myself as I did heaps of soldering during my apprenticeship many many moons ago. :)
Maybe I'll buy yet another tool like a good soldering gas torch. Keeping the vehicle is becoming more likely the more I spend. :O
AlanH.

[Tombie]

Good idea Josh but then the only prob you have is finding someone who is willing to even look at a Landie when away from the metro area. Maybe I could do it myself as I did heaps of soldering during my apprenticeship many many moons ago. :)
Maybe I'll buy yet another tool like a good soldering gas torch. Keeping the vehicle is becoming more likely the more I spend. :O
AlanH.

I’ve not recently experienced the “we don’t look at Landy” mechanic comments.

I did years ago and he was quite taken aback by my “so you aren’t a competent mechanic” response.

Nowadays they seem to be a lot lore flexible.

Having said that, no mechanic has worked on my vehicles in the last 5 years. All in house nowadays.

[hiker]

Love your wry humour Alan - we think along the same lines - haven't heard about the lack of replacement engines - thats a worry!
As I've always said - you don't just buy a Land Rover, you enter into a marriage contract!




I'm thinking of an electric bike to give my left ear a rest. :)
Actually I've been a bit frightened when reading of no new engines available if the worst happens, or the gear changing knob cacking itself through lousy workmanship, but on the other hand it's such s good car to drive and nothing disastrous has happened so I've kept it far longer than I normally do a vehicle.
AlanH.

[BradC]

I've been playing with battery charging. I bought a programmable bench PSU so I could experiment with charging algorithms.
This is a log of the "monthly top up", I'm not sure how it'll display on the forum so this is an experiment (it's really, really wide). The battery took just over 16Ah until it was "full". 12.2Ah in the bulk phase, the remainder effective in the boost phases.


186866

Edit : The forum scaled it. Original here (use open image in new tab or similar to view full size): https://www.fnarfbargle.com/private/230906-D3Charge/example.png
I found an interesting algorithm on a Russian web site for "flooded low maintenance Calcium batteries" and I modified it a little. I expect when I explain it there will be screaming, but as the magic Ford/Lucas smoke is still inside the wires and ECUs I'm still willing to take the chance.

- Bulk charge is fairly conventional at 14.4v to C/20 and current draw is stable for 5 minutes. (00:00-4:45 on the graph)
- Wait until voltage drops to 13.8V and then apply a float of 13.8V. Wait until current drops to C/20 and is stable for 5 minutes. (4:45-4:50)

This is the contentious bit.

- Apply a boost charge of 16V @ 1A. This terminates when the battery reaches 16V or the time exceeds 1 hour.
- Wait for battery to float down to 13.2V

This cycle repeats up to 7 times or if the battery reaches 16V within 10 minutes.
This is the dump from last nights boost cycle.


['B 3610', 'W 1354', 'B 3610', 'W 2174', 'B 3610', 'W 3494', 'B 1110', 'W 2034', 'B 755', 'W 2484', 'B 625', 'W 2489', 'Bend 545']


It terminated on both cycles and time simultaneously.

So the first cycle it boosted for just over an hour (and hour and 10 seconds) and it took 22 minutes (1354 seconds) to float down to 13.2v (4:50-6:12)
Second cycle boosted for the same and it took 36 minutes to float down to 13.2v (6:12-7:49)
Third cycle boosted for the same and it took 58 minutes to float down to 13.2v (7:49-9:47)
Fourth cycle boosted for 18.5 minutes and it took 34 minutes to float down to 13.2V (9:45-10:40)
Fifth cycle boosted for 13 minutes and took 41 minutes to float down to 13.2v (10:40-11:34)
Sixth cycle took 10 minutes and took 41 minutes to float down to 13.2v (11:34-12:35)
Seventh cycle took 9 minutes and terminated. (12:35-12:45)

- Maintenance charge. Float at 13.2v. (12:34->)

It'll be interesting to see how long this battery lasts. The previous one managed just over 50 months before it died. That only got a 14.8V every couple of months.

On the graph you can clearly see each time something in the car wakes up as a dip in the voltage.

[shack]

I expect when I explain it there will be screaming, but as the magic Ford/Lucas smoke is still inside the wires and ECUs I'm still willing to take the chance.

The smoke may still be in the wires, but you will have damaged it genetically!

What PSU are you using?

I'm getting more fascinated with battery health as time goes on...

I've been charging unhappy batteries on a timer for the last couple months with some successes and some failures, but the failures were already failed.. So only the successes count I guess.

[drivesafe]

I expect when I explain it there will be screaming, but as the magic Ford/Lucas smoke is still inside the wires and ECUs I'm still willing to take the chance.
Hi Brad and not sure what you mean, but if this is a reference to your vehicle's electrics tolerating that 16v.

Then all is well as most vehicle electronics are designed to tolerate at least 18v without any issues.

Boosting the voltage on Calcium/Calcium batteries is actually commonplace and you can do the same with older type Wet Cell/Flooded batteries.

It was actually commonplace to do this years ago with older type deep cycle batteries, but the process has been lost in time.

SPECIAL NOTE DO NOT do this to any form of AGM battery. It will damage them.

[BradC]

Hi Brad and not sure what you mean, but if this is a reference to your vehicle's electrics tolerating that 16v.

Then all is well as most vehicle electronics are designed to tolerate at least 18v without any issues.

You and I know that, but we also know when it comes to forums and keyboard warriors there's always wailing and gnashing of teeth!

My issue is I couldn't find a battery charger I could make do exactly what I wanted. I was running out of cost effective options and had seriously considered building something when this came along.


What PSU are you using?

One of these : https://www.aliexpress.com/item/1005005060176198.html

https://ae01.alicdn.com/kf/S5c6414c1220745ab8f73fb0be559a29eA.png

I haven't taken a close look at the output for noise, but as a programmable battery charger it's great. 30V/10A. It's reasonably accurate +/- ~30mV and there's an odd 30mV jump when it switches from CC to CV mode (you can see the spikes at the end of the last 3 boost cycles).

I have many lab power supplies which I've used for battery charging in the past, but I really wanted one I could remotely control and monitor. For about $150 landed this one does a great job. I had to poke the vendor hard to get the software, and the software it comes with is pretty crap. Like my SkyRC discharge tester I had intended to reverse engineer the protocol and write some software to drive it, but the software came with a "reasonable" doc file with the protocol in it. Win!

[shack]

So I've done a little fiddling around the last 2 days, we probably currently have 20-30 "dead" batteries, we usually take them to the scrap place every couple of years, and it's getting due again shortly.

However, this leaves me a lot to play with at the moment - and waste time on.

Our normal procedure when a battery fails is to pull it out of the car, then repurpose it with a less demanding job such as the trackers on the solar arrays, after they can't do that anymore, they get taken to the battery graveyard.

So by the time they get there, they really are cactus.

I have possibly 5 batteries that haven't made it that far yet, but are no good for starting cars, so I'll have a go at them and see what happens.

Yesterday I started charging a battery that was sitting at about 12 volts, I left it charging overnight at 0.2 amps, and max voltage set at 13.8 just to see what happened.
This afternoon I checked on it and it had gone from 12 volts resting , to 13.8 with 0.2 amps being pushed in at the start of the process, to 11.8 volts with it still being charged at the 0.2 amps now.

What is it the cause of this? Is it desulphation happening, or further dying?

[drivesafe]

Hi shack, seeing as you want to play with charging older batteries, if you have a lithium battery, anything of 50Ah or bigger, full charge the lithium battery then disconnect the charger.

Now get a set of jumper leads and connect the lithium battery in parallel ( + to + and - to - ) to any type of lead acid battery ( AGM or Wet Cell ) in any state of discharge and leave them like that for a week.

Before connecting the lithium battery, do a load test of the lead acid battery you are going to charge.

After the week, disconnect the lithium battery and load test the lead acid battery again.

You might be in for a big surprise.

[shack]

I haven't got any 12 volt lithium batteries unfortunately.

I guess what you are suggesting is similar to what I'm doing, so I shall keep at it and see what happens.

I'm hoping I'm having a positive effect.

[RANDLOVER]

More power to you, but I thought desulfation would need a higher voltage as IIRC my battery charger puts out 16 volts in ''repair'' mode.

Oops originally my post said,''battery'' instead of ''battery charger''.

[drivesafe]

More power to you, but I thought desulfation would need a higher voltage as IIRC my battery puts out 16 volts in ''repair'' mode.

Hi RANDLOVER, 16v is fine for Wet Cell batteries but is a No-No for many AGMs.

Using a lithium battery connected in parallel supplies a constant 13.3v.

This constant voltage will desulphate the battery and charge it VERY SLOWLY.

This is good for any lead acid battery and does not harm the lithium battery.

I had this setup in my Tiguan for 2.5 years and it not only recovered a stuffed Lead Acid cranking battery but maintained it in a fully charged state.

After removing the lithium battery, the stuffed lead acid cranking battery lasted another 6 months before finally needing to be replaced.