Lithium and lead on a solar system

[Sonar]

I am sure the answer will be no but I am asking anyway ..

I have solar panels on the Moho roof .
It has a mttp controller At the moment I have 2 lead batteries for the habitation area and one that runs the engine under the bonnet..

The solar charger allows to charge two batteries having two battery charging outlets. so I have used one for the connected habitation batteries
And the other to the engine battery …

The question


I will be changing the habitation batteries to lithium batteries soon including all the assorted bits that go with it .
The solar controller will be altered to lithium using dip switches on the unit.

So I know the habitation batteries will be solar charged . What about the engine battery there is only one set of switches to change to lithium. For both outlets

Will I still be able to charge the engine battery or will I have to disconnect it.
If I have to disconnect it what are my options. .. the only one I can think of is yet another solar. System.

 

[Veloman]

I am sure the answer will be no but I am asking anyway ..

I have solar panels on the Moho roof .
It has a mttp controller At the moment I have 2 lead batteries for the habitation area and one that runs the engine under the bonnet..

The solar charger allows to charge two batteries having two battery charging outlets. so I have used one for the connected habitation batteries
And the other to the engine battery …

The question


I will be changing the habitation batteries to lithium batteries soon including all the assorted bits that go with it .
The solar controller will be altered to lithium using dip switches on the unit.

So I know the habitation batteries will be solar charged . What about the engine battery there is only one set of switches to change to lithium. For both outlets

Will I still be able to charge the engine battery or will I have to disconnect it.
If I have to disconnect it what are my options. .. the only one I can think of is yet another solar. System.

I'm not an expert on battery charging but would have thought what you propose would work. It might not charge your lead acid vehicle battery to its full potential but would charge it reasonably well I would have thought and unlikely to damage it. Its more important that the lithium batteries should be correctly charged. If you have the spec for the solar charger compare the difference between lithium and lead acid charging.

 

[TJBi]

I am sure the answer will be no but I am asking anyway ..

I have solar panels on the Moho roof .
It has a mttp controller At the moment I have 2 lead batteries for the habitation area and one that runs the engine under the bonnet..

The solar charger allows to charge two batteries having two battery charging outlets. so I have used one for the connected habitation batteries
And the other to the engine battery …

The question


I will be changing the habitation batteries to lithium batteries soon including all the assorted bits that go with it .
The solar controller will be altered to lithium using dip switches on the unit.

So I know the habitation batteries will be solar charged . What about the engine battery there is only one set of switches to change to lithium. For both outlets

Will I still be able to charge the engine battery or will I have to disconnect it.
If I have to disconnect it what are my options. .. the only one I can think of is yet another solar. System.

@wildebus will no doubt be along shortly with the definitive answer, but there are definitely options other than a second solar system. For example, there have been posts in the past about various systems that enable a trickle feed from leisure to starter battery as required.

 

[Sonar]

Wildebus is designing a lithium system for me .
As you say I am sure he will no ..

 

[wildebus]

Various options available.

My personal favourite is an AMT Battery Maintainer from Ablemail. Reasons:

1) A Dual Output MPPT will only provide a Starter Battery (SB) charge when there is solar. So if on EHU, it will do nothing for the SB
2) The Dual Output MPPT has usually a tiny secondary current to the SB. Often not enough to actually do the job, especially when it is only provided when the solar is active, so divide that 1A current by half at least as an average.
3) The manual option of a cable plugged into both sides (the "clive mott" solution that will be posted on this thread very soon) is a faff and if you forget to plug it in or fit the fuse when parked up, it does nothing; and if you forget to unplug in or remove the fuse when starting the engine, the fuse blows. Rubbish option IMO except as a temporary solution
4) A wired in dedicated Battery Maintainer/Trickle Charger will work when charging with Solar OR with EHU.
5) The AMT Maintainer can be configured to suit Lithium Batteries or Lead Batteries (different characteristics) so it knows when the LBs are being charged or not; and can be configured for different duty cycles, so tuned for vehicles that have different parastic loads on the SB. And once configured, is fit and forget
6) The AMT can, unlike other Maintainers, be switched to an override position so it can be made active even when no LB charging is happening - useful when van stored up in a pound in the winter when other maintainers won't go on as no solar.
7) It also acts as a 'Battery Guard', so before the SB gets dangerously low, it will automatically kick in to use power from the LB to maintain it to try and save the SB. But it also is a Battery Guard for the LB as well, so it won't sacrifice the LB battery to save a failing SB. You want to try to save all the batteries, but Battery power is finite with no charging, and when it comes to the crunch, the LBs are bound to be more valuable than the SB, and the AMT recognises that.

End of the day, all down to preferences and choices, but I'd recommend the AMT12-2 over all the options I am aware of for the reasons above, and if the above sounds like an advert, so be it, but I see it as a list of reasons why I have an AMT12-2 in my own Motorhome annd would recommend it to anyone who doesn't drive their vans at least once every week.

 

[Sonar]

It may well be a case now of getting that sorted at the same time as the lithium battery system.
I will without doubt be in contact with member wildebus to design another system.

The way I see it is the solar system and the lithium system are two separate systems but connected somewhere .

All I can say it thank goodness the Amplo hydraulic system is a easy install…

 

[trevskoda]

Simple solution is to use your controler to charge the liths, then buy a cheap mppt unit and link to panels to charge the starter battery.
If and when my l acids die im going down the path, simple and easy to do.

 

[Sonar]

Thought the same buy a small panel and go to the battery .

Looking at controller I have now there are only one set of dip switches. Would have been better if there were two sets
But a can’t find a controller that has them so far .. shame really I thought someone may have thought of that ..

 

[Sonar]

I think I am going to end up fitting a 100 w. Solar panel kit just for the starter battery
That’s if I can find space on the roof. If not I am not sure the min size I could fit yet

 

[TJBi]

I think I am going to end up fitting a 100 w. Solar panel kit just for the starter battery
That’s if I can find space on the roof. If not I am not sure the min size I could fit yet

I'd have thought that you'd do better going for @wildebus' favoured option of the AMT12-2.

 

[nabsim]

If you set dip switches for lifepo4 the settings won’t harm lead acid. Just you get no float to speak of

 

[Sonar]

I'd have thought that you'd do better going for @wildebus' favoured option of the AMT12-2.

He is sorting out a new lithium system for me at the moment
I will have to go one way or the other depending if I can sort it all out like what goes where ect

 

[Sonar]

If you set dip switches for lifepo4 the settings won’t harm lead acid. Just you get no float to speak of

Thankyou it’s another option to consider

 

[merl]

Thankyou it’s another option to consider

Depending on how the outputs are configured electronically inside the controller you may find that the lithium setting only applies to the leisure side anyway, the cab battery output MAY be unchanged but a quick check with a multimeter will confirm.
Looking at the DIP switches it looks like the lithium charge voltage is set quite high somewhere between standard Lead acid and AGM (switches 2,3 and 4) with switch No1 disabling the float as Neil mentioned. A lot will depend on how the manufacturers have set the lithium recharge points but personally i'd give it a go 'as is' and monitor things over the first week or so and check the cab battery voltage with a multimeter, you could well be fine.

 

[Sonar]

9

Depending on how the outputs are configured electronically inside the controller you may find that the lithium setting only applies to the leisure side anyway, the cab battery output MAY be unchanged but a quick check with a multimeter will confirm.
Looking at the DIP switches it looks like the lithium charge voltage is set quite high somewhere between standard Lead acid and AGM (switches 2,3 and 4) with switch No1 disabling the float as Neil mentioned. A lot will depend on how the manufacturers have set the lithium recharge points but personally i'd give it a go 'as is' and monitor things over the first week or so and check the cab battery voltage with a multimeter, you could well be fine.

Just found this in a manual

ATTENTION: Only connect LiFePO4 batteries with integrated BMS!
Note: The possible parallel/floating operation with consumers being connected

Not sure what that means .

 

[Sonar]

Just asked an ai system about charging both lead acid and lithium at the same time with one solar MPPT unit with a single set of dip switches ..


That clarifies things a bit. Here's the situation based on your new information:

• Limited Lithium Support: Your MPPT controller with one set of dip switches can likely be configured for lithium batteries, but it might not support charging both lithium and lead acid batteries simultaneously.
• Focus on One Battery Type: You'll need to choose between charging either your lithium or lead acid battery with this controller.

Here are your options:

1. Charge Lithium Battery: Set the dip switches to the lithium profile and use this controller for your lithium battery. You'll need a separate charger for your lead acid battery.
2. Charge Lead Acid Battery: Leave the dip switches set for lead acid (assuming this is the default) and use this controller for your lead acid battery. Find a separate charger suitable for your lithium battery.

Additional Considerations:

• System Requirements: Consider your overall system needs. If your lithium battery is critical for essential systems, prioritizing charging it with this controller might make sense.
• Alternative Charging Solutions: Explore options for charging your other battery type. You might be able to use a simple battery charger or consider a different MPPT controller with more configuration options if you need to charge both batteries simultaneously.

Ultimately, the best choice depends on your specific setup and the importance of each battery in your system.

 

[Sonar]

Can I use two solar MPPT controllers on a single solar panel​

• Then thought maybe two controllers .

No, you generally cannot use two MPPT controllers on a single solar panel. It's not the most efficient way to set up your system and could even damage the controllers.
Here's why:

• Conflicting operations: MPPT controllers work by finding the maximum power point (MPP) of the solar panel. With two controllers on one panel, they could interfere with each other's operations, reducing overall efficiency.
• Potential damage: If both controllers try to draw current from a fully charged battery, it could lead to electrical issues and damage the controllers.

However, there are situations where you might consider a different approach:

• Multiple panels, one controller per panel: This is a common setup for solar systems with multiple panels. Each panel connects to its own MPPT controller, optimizing power output for each panel independently.
• Single controller exceeding capacity: If your solar panel's current rating is higher than the capacity of a single MPPT controller, you might need two controllers with a combined capacity that matches the panel's current. However, this is a less common scenario.

If you're unsure about your specific setup, it's always best to consult with a qualified solar professional. They can help you design a system that maximizes efficiency and safety.

 

[Sonar]

So with most of all avenues now explored member wildebus has the answer and that seems the only route to go down.

 

[trevskoda]

You can fit a inline diode/resister to cut down the charge to the starter battery.

 

[merl]

Just asked an ai system about charging both lead acid and lithium at the same time with one solar MPPT unit with a single set of dip switches ..


That clarifies things a bit. Here's the situation based on your new information:

• Limited Lithium Support: Your MPPT controller with one set of dip switches can likely be configured for lithium batteries, but it might not support charging both lithium and lead acid batteries simultaneously.
• Focus on One Battery Type: You'll need to choose between charging either your lithium or lead acid battery with this controller.

Here are your options:

1. Charge Lithium Battery: Set the dip switches to the lithium profile and use this controller for your lithium battery. You'll need a separate charger for your lead acid battery.
2. Charge Lead Acid Battery: Leave the dip switches set for lead acid (assuming this is the default) and use this controller for yur lead acid battery. Find a separate charger suitable for your lithium battery.

Additional Considerations:

• System Requirements: Consider your overall system needs. If your lithium battery is critical for essential systems, prioritizing charging it with this controller might make sense.
• Alternative Charging Solutions: Explore options for charging your other battery type. You might be able to use a simple battery charger or consider a different MPPT controller with more configuration options if you need to charge both batteries simultaneously.

Ultimately, the best choice depends on your specific setup and the importance of each battery in your system.

As I said previously, the charge potential to the cab battery will depend on the circuitry design of your controller, at the moment no one can answer that apart from the guy who designed it. The wiring image says" set the type of main battery" so there's your answer.
Trying it won't cost you anything and if you feel it's just not keeping the cab battery in a decent level then you can do something different. It could save you quite a lot of expense and faff. It can't possibly overcharge and you'll soon know if it's under charging.