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,
Click to expand...
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.
 
Last edited:
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.
Click to expand...
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)
Click to expand...
Hi,
Did the improved instructions get made? I can't get the settings changed on my AMT!
I did search but found nothing.
Thanks

Subscribers  do not see these advertisements

 
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
Click to expand...
Thanks......I think I'll be calling them tomorrow.

Subscribers  do not see these advertisements

 
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?!
Click to expand...
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!

Subscribers  do not see these advertisements

 
Last edited:
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.
 
Last edited:
mr_mojo97 said:
the Ablemail instructions say to wire to the AMT12-2 to the input on the solar charger
Click to expand...
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.
Click to expand...
Thanks Lenny. Are you saying it doesn't go through the solar controller at all? I thought that's what the diagram shows?
Cheers



20240321_230233.jpg
 
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
Click to expand...
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.

Subscribers  do not see these advertisements

 
Last edited:
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.
Click to expand...
Thanks for the info, mate. I almost went down the route of a Renogy dual controller but found these instead. Cheers
 

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Join us

Log in

Already a member? Log in here.

Latest journal entries

Back
Top