AMT12-2 Advice needed

[PeteS]

Hi, I've just swapped over to Lithium and my VanBitz battery Master has not maintained the starter battery possibly for a number of reasons, no sun for the past week probably but at no point has the red led come on to indicate charging. Lithium has been sat at 13.2 vehicle battery at 12.45v. For the first time ever the starter battery struggled to turn over the engine.
Now as the starter battery is 8 years old and it was 2C outside it probably needs replacing so that will be my first port of call anyway however it got me thinking and looking at the Ablemail AMT12-2 but its modes to me aren't clear, for Lithium the thresholds are leisure at 14.2 and starter at 12.8v.
What does that actually mean? lithium 14.2V is unlikely to be achieved on solar over winter, is that the point it starts charging?

The information on Ablemails website includes this:
The Trickle Charger also feeds charge from the Auxiliary Battery to the Vehicle Battery until they reach 11 .5V & 11 .7V respectively
ensuring that both Batteries are kept as healthy as possible even if no Solar Charger or Main Charger is present.
How does this relate to the 14.2v threshold and I doubt that's correct for Lithium.

To me its not very clear how it works and the way that Wildebus is using it does not come across in the datasheet as far as pulsing is concerned although I do understand it can be programmed but how that happens isn't obvious either.

So is anybody using this in a Lithium set up and can help before I possibly invest.

 

[wildebus]

I think I will reply ignoring the datasheet as some updates in the settings have been made for Lithium recently and I don't know if they have made it to an updated datasheet yet or not.

The Main Purpose of a trickle charger: Maintain the Starter Battery.
What you need is a device that will operate when the Leisure Battery has an active charge (be it EHU or Solar). And is off when there is no active charge. Sounds obvious, but it means the "On" Threshold has to be ABOVE the maximum resting voltage of the Battery, and BELOW the minimum voltage the charger is putting out (and that is the minimum of ANY state - Aborption, Float OR storage if it has that mode).

Lithium resting voltage is usually around 13.1V I think?
A chargers Float voltage is (depending on config) between 13.8V -13.6V. Storage is around 13.4V to 13.5V.
So a trickle charger needs to be configured to activate somewhere between 13.1V and 13.4V. And go off when the voltage drops below the battery resting voltage
So on an AMT-12, it would be programmed to go on at say 13.25V and off at 13.0V on a lithium setup (those numbers are not set in stone, just as long as they are in-between the key parameters as described above).
In a Lead Acid setup, you would have different settings (which would be pre-set in the AMT and you select that config)

Pulsing
The unit works by sending a pulse of current to the Starter Battery rather than being always on. The on and off times are programmable so can be set to anything you want potentially. I changed mine to suit my own setup which is a little different, but the default will suit the majority of people.
The end user would not actually make these kind of specific changes but can select from a variety of pre-set configurations if the shipped default does not suit, but basically the unit will be on 50% of the time while there is an active charger on the Leisure Battery.


Ref "The Trickle Charger also feeds charge from the Auxiliary Battery to the Vehicle Battery until they reach 11 .5V & 11 .7V respectively
ensuring that both Batteries are kept as healthy as possible even if no Solar Charger or Main Charger is present."
How does this relate to the 14.2v threshold and I doubt that's correct for Lithium.
This is separate from the primary Trickle Charge feature. It is a system where if a vehicle has been stored away from any charging and the Starter Battery gets to a relatively critical low voltage where it could start to get damaqed, the AMT-12 will start to provide some trickle charge from the Leisure Battery to try and ensure - as it says - "...both Batteries are kept as healthy as possible even if no Solar Charger or Main Charger is present."
This is totally separate to the charging thresdholds and does not relate to that at all.
The voltages of "11 .5V & 11 .7V respectively" are not for Lithium. The cutoff voltage programmed for a Lithium Battery in this mode would be higher, for as you know, the voltage decline is much more gradual on Lithium, so the cutoff would be set appropriately higher.

One of the key things with the AMT and its great advantage over the alternatives is that everything described above is available on the same physical unit. The only changes needed are to the programme.
People talk about Dumb Chargers and how Smart Chargers are the way to go nowadays. Well the AMT-12 is the 'Smart Charger' in the Trickle Charger/Battery Maintainer/Battery Master world.

 

[PeteS]

As always thank you very much for your input. Does it come with everything to be able to programme it if needed or is that an extra to buy. Apart from on the website I can’t find anyone offering a programming lead.

 

[wildebus]

As always thank you very much for your input. Does it come with everything to be able to programme it if needed or is that an extra to buy. Apart from on the website I can’t find anyone offering a programming lead.

The idea is that it comes with programmes that are pre-set and selectable (via a routine I will agree is not the most obvious - a consequence of a product from an engineering company rather than a marketing company) and you select the mode you want. I can confirm that this unit DOES work with Lithium
You would not typically buy/use the programming lead unless you were a developer. If you had specific parameters, they could be potentially programmed by the reseller (some will, some may not -you'd have to check with them if this was a requirement).
The unit comes without any power leads from Ablemail if buying directly. I bundle in power leads in the units I sell as I like to do a bit of a "one-stop shop" approach.

 

[PeteS]

Thank you. It now depends on wether the vehicle starts on Friday, we’ve been in the Norfolk Broads for a week and I’m not convinced it’s been charged ok. If not I will be in contact.

 

[wildebus]

Thank you. It now depends on wether the vehicle starts on Friday, we’ve been in the Norfolk Broads for a week and I’m not convinced it’s been charged ok. If not I will be in contact.

Something that I think is also a handy thing to have is one of the little lithium Jump Packs. I used one on my Van a while back in 2018 when I needed to start it (I knew the battery had had it but didn't want to replace it until the Spring).
They come and go on Amazon so can't point to a specific one, but worth checking out. (also used it on the car once when that had a random flat battery for an unknown reason).

 

[PeteS]

Yes I have one at home although its bulging a bit now but its quite happy starting a V8

 

[Chris Evans001]

I can recommend the AMT 12. It's pulsing away nicely to my starter battery when on mains hookup or solar to my lithium leisure battery bank.
Works a treat and keeps my starter battery up at 12.8v constantly.

Order it from wildebus and you get the interconnects bundled in with some nice colour coded terminal boots.

Think I've got the hang of the instruction manual now. It might as well have been in hieroglyphics for all the sense it made to me at first.
Fortunately, it's a lot more simple in practice than when it is written down on paper!

 

[PeteS]

Interesting observations this morning on my installed lithium system, I have a raspberry pi running Venus OS monitoring my solar and a BMV712 keeping an eye on state of charge. Over the last two weeks the solar yield has not been great and when it has the tempearure has been too cold to allow charging to take place, its now at 65% SOC on 150Ah of lithium. My monitoring setup including a tracker takes 5Wh so around 10Ah a day.

This is teling me that I do not have enough solar (160W) to maintain my monitoring during the winter months so I decided to put my FLA battery back in today on the basis that with Covid who knows whats going to happen and my vehicle is in storage so I may not get access to it easily. I will also disconnect the monitoring but i'm going to leave that for a few days just to see how it copes.

Interesting result in changing over, I have a Battery Master to trickle charge the starter battery as mentioned earlier in this thread and it is not being charged by the Lithium, the Lithium sits at13.2v so the starter would get 12.4V which for an ageing battery isnt enough, it does start but it struggles. The solar yield is such that it hardly rises above 13.2v when its charging.
Putting the FLA in allows the battery voltage to rise to 13.8 quite easily and there is now a 1A charge going to the starter which was never there on Lithium.

I'm sure that as the days get longer and the solar yield increases again it would have started charging again but in these winter months it doesnt cut it.
So an AMT-12 is definitely in the offing now.

My main reason for disconnecting the Lithium is I'm happy for the Lead Acid to go flat, I definitely didnt want my Lithium going the same way when I may not be able to get there to rescue it, the FLA has been ok for the last 8years.

Just to reiterate the Geek in me wanted to monitor remotely whats going on whilst in storage, I could just have diconnected the monitoring and I'm sure the Lithium would have coped, but I wouldnt have known and it could have been costly!!!

 

[Nabsim]

Why isn’t the solar giving any charge due to temperature, are you up in the Highlands or somewhere below zero? You can charge Lifepo4 below 5 degrees, you just need to reduce the charge rate. Mine have been getting a little on solar but not enough to keep monitoring running for ever. I parked mine up on 6th November for the first time in a long time and it has only had whatever solar was available. I will be moving it again in a few days so no worry’s for me but I wouldn’t worry too much anyway, not like the are lead acid, they can take going flat even if it is best to avoid. Battery’s were around 80% when I parked it

My Votronic mppt has had enough sun to maintain my starter battery at 12.7v so far, that will trickle a 1 amp charge from solar when sun shines and there is enough charge coming in

 

[PeteS]

The interior of motorhome was sat below freezing for about 4 days, a couple of weeks ago, we are in Northamptonshire. Although the outside air temperature climbed during the day, the insulation in the motorhome kept the temperature below zero.
Guess thats life and having spent a huge amount on the battery I wasnt prepared to let it go flat for the first time when I might not be able to get to it.