Alternative trickle charger for the starter battery

eddievanbitz said:
I'm definitely not "Poo - Poo'ing" what Lenny has said (who I hold in high regard) but there would be external reasons, third party equipment complications that led someone to that belief, who then told Lenny what he believed, who in turn has now told you,
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I helped him sort the problem, probably a one off, December in Scotland he had two starter batteries die on him and the airbag ECU.
He's not technical at all & was using a local auto electrician. He didn't really have enough solar for the time of year in Scotland so the Lithium weren't getting above 13.2v with the voltage differential the Batterymaster works at the starter battery was not really getting high enough to protect the airbag ECU. Also he had a highish parasitic drain on the starter battery which the Battery master was struggling to keep up with, I think the auto electrician sorted that.

An odd combination of circumstances led to the problem in this case the AMT worked.
 
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Lenny HB said:
No, I was thinking Lithium, more from an interest point of view as if I go for Lithium, getting tempted to build one with the cell prices coming down. But I would probably stick with Votroinc solar regulator as I want the AES output for the fridge & it has a dual output for starter battery charging.
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That is funny, in that I first replied thinking you were thinking Lithium, then edited reply based on Lead. So ... Back to Lithium reply .... I would say 13.2V would be too low for the following reason:
On the assumption that you want a trickle charger to be active when there is charging occuring, and off otherwise, 13.2V is within the rest voltage of a full/pretty well full Lithium (for example, my Lithium is reading 13.29V currently with no load and no charge).

What 13.2V could give you is a bit of a half-way house though (like in your Scottish motorhomer example)... If in storage say or just unused, it would allow the Starter Battery to receive a trickle from the Lithium until it drops to a certain point, so using that spare capacity more safely as it were. Lithium is known for its flat voltage line until nearly dead, but that line is still one that is gradually dropping as the SOC decreases. And if I take my own Lithium as an example again, the voltage line takes a noticable little dip around (from memory) the 65% SOC point, where the voltage drops down to 13.0V. I don't know how typical that is, but I have noted that on multiple examples of the same model of Battery, so not literally a one-off aberration.
That "half-way house" could be useful for some people where there is inconsistant solar. Taking my own case in the graph I posted, I turned on the AMT manually to boost the Starter .... If I reprogrammed the threshold to a lower voltage, it is possible it would have been active by itself. That could be handy in a van miles away in storage where it is not so easy to pop out and flick a switch.
On the topic of Solar, as an aside I did have the AMT SW2 connected via the Load of a Victron MPPT at one time. This meant I could remotely force it on using the Victron VE.Connect software, which was quite funky. Not the kind of thing maybe the typical camper would be interested in doing, but for me, it just shows the bonus and benefit of having such a flexible product.
 
Hoovie said:
Just to hopefully help, there is a "taskforce" being engaged tomorrow to go right through the instructions and make them a lot more 'user-friendly' so a revised datasheet version in plainer English will be posted up very soon.

Also, something that has not been mentioned, but I think "wildbunch" wondered about? the need for fuses? I used to supply cables with fuseholders, but I don't do so any longer as the AMT is internally fused. And to confirm, the fuse is self-resetting (y)
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Hi,
Did the improved instructions get made? I can't get the settings changed on my AMT!
I did search but found nothing.
Thanks

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I fitted a Ablemail b2b and they could not have been more helpful and if you phone their technical the guys understand the products they make and can advise you đź‘Ť
 
Steve and Denise said:
I fitted a Ablemail b2b and they could not have been more helpful and if you phone their technical the guys understand the products they make and can advise you đź‘Ť
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Thanks......I think I'll be calling them tomorrow.

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Gobsheen said:
Thanks. That is clearer but I still don't know where to connect the other end of the fly lead going to SW1! Maybe it's me?!
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I used another cable connected to a +VE connection so I could then touch SW1 when required. Also make sure the 0V (Negative Connection) is just push onto the spade. You don't have to fight getting the connection on/off the spade. I did a couple of dry runs, so I had built up a bit of muscle memory and had @Wildebus's instructions in front of me. I will admit when it arrived and I read the original fitting instructions, they were as clear as mud.
The tech guy's at Ablemail are very helpful. They didn't leave me hanging when the bluetooth module failed to connect to my iPhone, with phone calls and emails. Hope that makes sense;)
 
Hi, all. I've just got my AMT12-2 today and gonna wire it over the weekend. A couple of questions if I may, it says in the instruction that the cabling should be minimum of 1.5mm2 - what would be the optimal size? Also my set up is 110w panel into a Victron 75 10 MPPT charger to 2x12v leisure batteries - the Ablemail instructions say to wire to the AMT12-2 to the input on the solar charger and then to the main chassis battery. So how do I wire to the main chassis battery? - the only other connectors are the Load terminals!

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My Battery Master worked absolutely fine all through winter topping up the vehicle battery from the Fogstar as expected. Don't care how, it just did.Fitted it myself in 20mins.
 
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mr_mojo97 said:
the Ablemail instructions say to wire to the AMT12-2 to the input on the solar charger
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No they don't.
All you need to do is wire the input positive negative connections to the leisure battery and the output to positive of the starter battery.
Cable size will depend on the lengths of the cables, it only pulses at 3 amps if only a couple of metres 2.5 or 3 mm² should be fine.
 
Lenny HB said:
No they don't.
All you need to do is wire the input positive negative connections to the leisure battery and the output to positive of the starter battery.
Cable size will depend on the lengths of the cables, it only pulses at 3 amps if only a couple of metres 2.5 or 3 mm² should be fine.
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Thanks Lenny. Are you saying it doesn't go through the solar controller at all? I thought that's what the diagram shows?
Cheers



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mr_mojo97 said:
Thanks Lenny. Are you saying it doesn't go through the solar controller at all? I thought that's what the diagram shows?
Cheers
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That diagram assumes that you have a combined Solar Controller and B2B unit. They are taking advantage of the fact that the connections to it include +ve to Leisure battery, +ve to Engine battery and 0v (Earth).

If you trace the connections, you will see that you get the same result by connecting connecting the cables as described by Lenny HB
 
That is a reasonable diagram of how to wire it to a B2B charger, but a totally misleading diagram of how to wire to an MPPT Solar charger. For a start, the input of a solar charger is the solar panels, which will be at least 18V, and may be over 30V. You definitely don't want to connect the AMT12-2 to that. Also most MPPT chargers (including the 75/10) don't connect to the vehicle battery at all, only the 'dual output' ones do that (that's two battery outputs, not one battery output and one load output).

In theory you could wire the 'Vehicle Battery' (VB) terminal of the AMT all the way to the vehicle battery, and fit a small fuse, say 5A, to protect the wire. And then wire the Leisure Battery (LB) terminal all the way to the leisure battery, again with a small fuse. That would work fine, but is more work than is usually required.

The trick is to find some other nearby device that is already wired to the vehicle battery and the leisure battery. There's usually at least one. A B2B charger is the obvious choice, if one is fitted. A dual-output MPPT Solar charger is another possibility: connect the AMT VB terminal to the Vehicle battery output of the MPPT, and the AMT LB terminal to the leisure battery output of the MPPT. Another possibility is the 12V distribution/fusebox: that will have a connection to both batteries. Or if the split charge relay is separate from fusebox, that will have vehicle battery and leisure battery connections that can be used.

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I use a Sterling Power B2B set to half power to keep the starter battery topped up.
Using input from the leisure battery. It works very well.
 
autorouter said:
That is a reasonable diagram of how to wire it to a B2B charger, but a totally misleading diagram of how to wire to an MPPT Solar charger. For a start, the input of a solar charger is the solar panels, which will be at least 18V, and may be over 30V. You definitely don't want to connect the AMT12-2 to that. Also most MPPT chargers (including the 75/10) don't connect to the vehicle battery at all, only the 'dual output' ones do that (that's two battery outputs, not one battery output and one load output).

In theory you could wire the 'Vehicle Battery' (VB) terminal of the AMT all the way to the vehicle battery, and fit a small fuse, say 5A, to protect the wire. And then wire the Leisure Battery (LB) terminal all the way to the leisure battery, again with a small fuse. That would work fine, but is more work than is usually required.

The trick is to find some other nearby device that is already wired to the vehicle battery and the leisure battery. There's usually at least one. A B2B charger is the obvious choice, if one is fitted. A dual-output MPPT Solar charger is another possibility: connect the AMT VB terminal to the Vehicle battery output of the MPPT, and the AMT LB terminal to the leisure battery output of the MPPT. Another possibility is the 12V distribution/fusebox: that will have a connection to both batteries. Or if the split charge relay is separate from fusebox, that will have vehicle battery and leisure battery connections that can be used.
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Thanks for the info, mate. I almost went down the route of a Renogy dual controller but found these instead. Cheers
 
Hoovie said:
Thought I would add some comments to this thread ref the AMT12....

The current AMT12 is the AMT12-2. Photos below:
View attachment 596251View attachment 596252
The key difference between the AMT12-2 and the original one is the style of connections. The original ones uses 6mm studs; the new one swaps those to Feston (spade) connectors.

The instructions do need some "Plain English" re-writing, I would agree. On the plus side, the instructions ARE correct when followed and these devices really are "fit and forget" once setup.

Now Switch 1 and Switch 2 ... These are not switches as such but connections. You CAN connect switches to them to expand the devices usability however.
Switch 1/SW1: (next to Green Plug) This is a connection that allows to to select which one of the 8 preset programmes you want to use, following the (hard to follow) instructions in the Instruction Sheet. You chose the Programme depending on the type of Leisure Battery and Type of Alternator you have:
Setting 1: Standard Alternator and Lead Leisure Battery
Setting 2: Standard Alternator and Lithium Leisure Battery
Setting 3: Smart Alternator and Lithium Leisure Battery
Setting 4: Smart Alternator and Lead Leisure Battery
The setting you choose determines the Leisure Battery voltage at which the unit will turn on and the target charge voltage of the Starter Battery
There are also on the later units an additional 4 Settings (5-8) that replicate the voltage parameters of the first 4 but has a longer active cycle to deal with a greater parasitic drain on the Starter Battery.
SW1 is only ever used for initial setup of the AMT12. The only time you would typically use it to reprogramme is if say you fitted the AMT and then updated your Leisure Battery from Lead to Lithium (so change settings from 1 to 2, or 4 to 3 for example).
Talking about Programming, the 4 pin Green Plug can be used to reprogramme beyond the factory presets. It is possible to buy a USB lead to connect to your Windows PC and run the Ablemail s/w to programme it. Or on the later versions, a Bluetooth Module (ABB07) can be fitted to the plug and a Smartphone App used to reprogramme. You can use the Windows Programme or the Windows App to Monitor as well as programme, which could be of use, but generally is not needed by most folk.

The other connection - Switch 2/SW2: (next to 0V) - is something that can be of use post-installation. If a +12V signal is applied to SW2, the AMT12 is forced on and the preset programme is ignored whilst SW2 is high. It still has an on/off cycle, but is predominantly on, and does not rely on a certain voltage to be enabled.
This can be useful if you are in a situation where charging is poor (maybe over-winter in storage?) and you are ok to use some of the spare capacity of the Lesiure Battery to trickle the Starter to avoid it getting to a very low level?
I have the SW2 on my AMT12 connected to +12V via a rocker switch so I can easily flick the switch and force it on if I feel the starter is getting low and I want to give it a boost.
This graph may help illustrate that:
I was not getting any decent charging via solar this month and the starter was on the usual gradual decline.... on the 6th March, I flicked the switch to force the AMT12 on and you can see the effect on the voltage. I turned the switch off the next day and you see the voltage starting to drop again as expected. On the 12th March I plugged in EHU and the AMT kicks on when the Activation Voltage is attained, but this time the programme parameters are used and the Starter Voltage settles at around the ~12.8V
View attachment 596264

Some other points on the AMT programmes .... As mentioned there are 8 selectable presets to choose from, plus an override option via SW2.
But when running in any of the Preset Settings, there is in addition a built-in "emergency" mode that if the Starter Battery drops to a critical level, the AMT will turn on to try and save it using power from the Leisure Battery (on the basis of better to use available capacity on the Leisure Battery rather than sacrificing the Starter). However, this will only continue until the Leisure Battery drops to a certain point itself (again on the basis that you don't want to sacrifice the more expensive Leisure Battery to save the more basic Starter Battery).

I hope this helps explain the AMT12 a little better?
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Fabulous piece thanks ever so much for posting are you trading under Hoovies Locker selling these on ebay?
 
WildBunch said:
Hi
Thanks to Hoovie, LeneyHB & others for all the feedback. My AMT12-2 is on order & hopefully will be delivered soon.
I must confess I do not fully understand all the different settings that are possible. I am looking forward to the updated instructions.
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Hi can I ask how the Amt12-2 has performed over the last 7 years? had any problems?
 

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