Amt12-2 oddity

[Duckato]

One primarily for @wildebus
I recently bought the annoyingly expensive BT interface for my AMT12 because I could not make sense of the way the unit was performing.

So much so that temporarily I reverted to my tried and tested diode, fuse and lightbulb!

It simply wasn’t doing what I wanted to I.e keep the chassis battery charged.

I want it to maintain the battery 24*7 overnight or during extended periods without solar in between the sun coming out typically when my lithium battery is then sitting at 13.2v

Using the BT interface (and the unbelievably flaky app that loses connection constantly even when only a metre away) lead to a couple of observations, on first connection I noticed the ‘user voltage difference’ value was 2.24v

Setting the unit to default which I assume can’t be done without the bt interface? reset the ‘user voltage difference’ value to a far more sensible 0.32v

The unit then started charging again but not for long and seemed to stop once the battery dropped to about 13.18v
That didn’t make sense.

The app showed that the ‘Leisure battery guard threshold’ was set to 13.06v (prior to gettin the BT interface I had to use the default AGM profile for this exercise because the lithium default was way to high )

At 13.06v the unit should still be charging.

Then I decided to measure the true voltage at the units connections incase I had any volt drop which I don’t and voila it clicked, there is about a 200mV discrepancy between the actual voltage on the supply pins and what the units internal electronics is measuring.

Hence the unit is switching off prematurely.

I have now tweaked that voltage down a bit more and so far it’s behaving

So mine could be faulty, could you check the actual versus app reported voltage on yours please?

 

[wildebus]

Firstly, the AMT12-2 is primarily designed to be active when there is charging occuring. This is why the Lithium Profile's voltage is set where it is. It is not way too high, it is correct UNLESS you want to change the functionality of the AMT to operate regardless of charging state.

Now as far as the User Voltage Differential goes, TBH I have no idea! I've never looked or altered this.
What you should be able to do is connect to the AMT with the ABB and select one of the original default profiles to load. I don't have a AMT+ABB setup handy I can connect to to do this but you should see profiles relevant to the product you have available to choose from. Do this and then maybe tweak just the voltage on threshold.

 

[MarkJ]

Firstly, the AMT12-2 is primarily designed to be active when there is charging occuring.

Yes, and it also has an ability to keep the vehicle battery from dropping below 12.2v so long as the LB is above 12.4v (IIRC).

Ive found mine is also slightly ‘out’. My VB is kept at about 12.16 rather than 12.2v, but that’s ok.

 

[MarkJ]

PS…

annoyingly expensive BT interface for my AMT12

Not sure I’ve seen this. Is it something Ablemail do?

 

[Duckato]

PS…

Not sure I’ve seen this. Is it something Ablemail do?

Yep, after realising there was something odd with my unit I contacted their suppprt team asking how much the serial interface cable would cost or could I have a pin out as I am more than capable of making one, so I could check the settings after all a cable and a couple of connectiors shouldn’t be that expensive perhaps £5 in parts! They never gave me a price or even offered to help with the problem I reported and instead their salesman suggested I buy the bt thingy

ABB-07 Bluetooth Vehicle and Secondary Battery Status Monitor | eBay

Battery status monitor which allows monitoring of your secondary battery. There are 2 versions of the app a " Viewing" version and a "Updating" version. Connects to your smartphone via Bluetooth. Check your battery status anywhere from your phone.

www.ebay.co.uk

 

[wildebus]

Yes, and it also has an ability to keep the vehicle battery from dropping below 12.2v so long as the LB is above 12.4v (IIRC).

Ive found mine is also slightly ‘out’. My VB is kept at about 12.16 rather than 12.2v, but that’s ok.

The voltage chip that is used has 'steps' in its settings of around 0.05V, so that sounds about right in fact. When you choose a voltage and send the setting to the unit, when you read it back, it has saved to the closest available setting (as an example, one one of the devices Ablemail makes exclusively for me, I have to chose a voltage of 13.41V rather than 13.40V)

PS…

Not sure I’ve seen this. Is it something Ablemail do?

It is the ABB-007 Bluetooth Module. Plugs into the 4-pin Green connector and allows you to adjust the settings and also monitor the voltages.
It talks to an Ablemail App called "Battery Manager", available on Android and iOS. It is not the greatest of Apps and not close to say the Victron Connect App, but it is getting better and they are constantly improving it (so worth while uninstalling and reinstalling from the Apple or Google stores on a regular basis)

 

[wildebus]

Yep, after realising there was something odd with my unit I contacted their suppprt team asking how much the serial interface cable would cost or could I have a pin out as I am more than capable of making one, so I could check the settings after all a cable and a couple of connectiors shouldn’t be that expensive perhaps £5 in parts! They never gave me a price or even offered to help with the problem I reported and instead their salesman suggested I buy the bt thingy

ABB-07 Bluetooth Vehicle and Secondary Battery Status Monitor | eBay

Battery status monitor which allows monitoring of your secondary battery. There are 2 versions of the app a " Viewing" version and a "Updating" version. Connects to your smartphone via Bluetooth. Check your battery status anywhere from your phone.

www.ebay.co.uk

Serial Interface is around £100 for cable and PC Programme but not generally available to end-users (specific company decision).

 

[MarkJ]

Hmmm. £78 is a bit expensive I’d have thought: a tool if you install these for others but perhaps not if you’ve just got one of their gizmos. Shame, I do like a nice bit of monitoring….

 

[wildebus]

Hmmm. £78 is a bit expensive I’d have thought: a tool if you install these for others but perhaps not if you’ve just got one of their gizmos. Shame, I do like a nice bit of monitoring….

Mine are £70
But I say to anyone who asks me about them that it is 100% an optional device and not needed to use the AMT, but is handy for those who like a fiddle
It is handy for installers indeed as handier than getting the laptop out for special setups but for the AMTs I don't tend to use the ABB module to configure but just programme using the appropriate pre-set same as an end-user would do. (those pre-sets have been set with a bit of pre-thought )

 

[xsilvergs]

I was very happy with my AMT12 while using an AGM leisure battery. When I changed the AGM for Lithiums I became disillusioned with it. I discussed this with Jonathan and it was reprogrammed with different voltage settings. Unfortunately it still can't detect the small voltage changes of my Lithiums and it is now set to charge continuously at the boost level by attaching a lead to one of the terminals.

I don't wish to invest more money and purchase a Bluetooth Interface. Detailed written instructions on how to put it into programming mode so it can be setup over its RS485 connection would be useful.

Victrons programming capability through their VC app has spoilt me I guess.

 

[wildebus]

I was very happy with my AMT12 while using an AGM leisure battery. When I changed the AGM for Lithiums I became disillusioned with it. I discussed this with Jonathan and it was reprogrammed with different voltage settings. Unfortunately it still can't detect the small voltage changes of my Lithiums and it is now set to charge continuously at the boost level by attaching a lead to one of the terminals.

I don't wish to invest more money and purchase a Bluetooth Interface. Detailed written instructions on how to put it into programming mode so it can be setup over its RS485 connection would be useful.

Victrons programming capability through their VC app has spoilt me I guess.

I don't think it is really feasible to base any switching activity on voltage levels with Lithium Batteries as the voltage varies so little as the state of charge varies, and different Lithiums are slightly different as well, which would make an pre-set off-the-shelf product very tricky to do.

 

[xsilvergs]

I don't think it is really feasible to base any switching activity on voltage levels with Lithium Batteries as the voltage varies so little as the state of charge varies, and different Lithiums are slightly different as well, which would make an pre-set off-the-shelf product very tricky to do.

I agree with you. Mine was programmed with 0.2v steps but 0.1v would have been better for experimenting. Detailed instructions on how to get into programming mode would help as I have the lead.

 

[Duckato]

I think it’s worth pointing out that the firmware in the AMT I bought from wildebus was for whatever reason corrupted and it internally under reads the true battery voltage further interfering with operation.

So without buying the stupidly expensive and dreadfully flaky Bluetooth/app combo I would never had known why it wasn’t working as expected

In my own van, the connectivity of the app is dire even when only a foot away its constantly losing connection but the important thing is I was eventually able to use it successfully after many attempt to firstly factory reset the firmware and then to modify it to suit my expectations and allow for the fact it is not measuring the input voltage correctly

I did try to get assistance from the manufacturer, I has assumed the serial cable would have been significantly cheaper but at the time they didn’t want to know and obviously at that time I didn’t know what the problem was either!