Keeping two different ah batteries charged?

[Beavo]

Let me see if I can explain this coherently.

I have a small camper van.

We are going to Norway this winter where there won't be much, if any, sunlight.

My 100ah LiFePo4 battery gets charged by the alternator and a 200w solar panel.

The charge controller from the solar panel has the ability to have two individual batteries connected. Although I originally only had the one 100ah battery.

This was all installed professionally.

However I wanted to just have a battery that I could use for just a few small lights and usb outlets so I added a second 30ah LiFePo4 battery to the second outlet of the charge controller.

So this 2nd battery only gets charged by the solar panel and of course there will be no sun.

My question is…

Can I connect the two batteries whilst I'm driving (via a switch maybe) so that both the batteries get charged by the alternator.

A few extra things for info.

The first 100ah battery runs the LPG heater and my CPAP machine whilst I'm asleep, as well as the fridge, normal van lights etc

(A CPAP machine helps you breathe while you're asleep for those that weren't aware. So it's an essential thing for me.)

The van originally had a lead acid 100ah battery but I upgraded it this year as when it started to run low it wouldn't keep the LPG heater going.

I suppose I should add that if I do add a switch, inevitably I'm going to forget to turn the connection off.

I can add some photos if required.

Many thanks

 

[pollenface]

I would go with a dc-dc charger, max charging current depends on bms limits. Possibly 7.5a

 

[Beavo]

what did you upgrade it to?

Then added this one after for a few lights just to negate the usage of the 100ah.

 

[Beavo]

Just to clarify, this is the charge controller that I have and the 100ah battery that I originally had.

 

[Beavo]

I would go with a dc-dc charger, max charging current depends on bms limits. Possibly 7.5a

Sorry I didn't notice this reply.
Do you mean between the two different batteries?

I should add an extra clarification.
I'll only be needing this setup for the Scandinavian countries.
It should be fine on our other trips which are usually in sunnier places.

Cheers

 

[mikefitz]

going to Norway this winter

Solar won't be much use, so regard any solar as a bonus and rely on other charge methods.

controller from the solar panel has the ability to have two individual batteries connected.

What model of controller? Many of the dual output controllers don't charge either battery very well. I can add further comment knowing the actual model. Thanks for the update on the controller, its an uncommon model , ( it would not be my recomended unit)
Since there is no default setting for lithium, what charge perameters have you set up?

Can I connect the two batteries whilst I'm driving

You can leave the batteries connected together all the time, both to main output of the controller and to the alternator charging.

wouldn't keep the LPG heater going.

The LPG heater takes around 1.5 amps, you will be running this for longer periods so take this into account.
LPG is available in Norway and Sweden but not in Finland. Outlets are few and tend to be self service setup, usually in industrial estates. You need to plan carefully, use 'my lpg' and 'Park for the night ' to find LPG outlets. ( bayonet or dish connector).

small camper van.

Do you know the alternator power rating , or van model /year.
It's usual to fit DC to DC chargers where alternator charging is used, do you have this?

100ah battery runs the LPG heater and my CPAP machine whilst I'm asleep, as well as the fridge, normal van lights

100Ah, even with the additional 30Ah, seems a bit marginal, if budget allows fit an additional 100Ah. ( this also alows redundancy if one battery failes)
Since alternator charging is crucial for your power, ( do you have an AC charger if you use campsites?). It would be useful to discuss this.
I think the Ecoworthy has low temperature protection, so it will stop charging at 0C and resume at about 5C.

I guess you are planning for winter conditions, winter tyres, snow chains, perhaps studs ( fit when you are there if the tyres can take studs). I have travelled Norway, Sweden, Finland and Baltic States ( but not In winter). If you wish to discuss anything about the trip use direct message.

 

[Beavo]

Since there is no default setting for lithium, what charge perameters have you set up?

This is my settings via the app.

 

[Beavo]

You can leave the batteries connected together all the time, both to main output of the controller and to the alternator charging

In that case I will connect them so they can charge together. I would like a way of adding a switch of some description to stop me using any of the 100ah battery for anything "unimportant"

 

[Beavo]

The LPG heater takes around 1.5 amps, you will be running this for longer periods so take this into account.
LPG is available in Norway and Sweden but not in Finland.

Our van is dual fuel (LPG & Petrol).
It's a 90 litre LPG tank and our plan is to just use that for heating unless LPG is available regularly.

 

[Beavo]

Maybe I should add that it's only a small converted van.
Not a big RV thing.

 

[mikefitz]

that it's only a small converted van.

I guessed it was a small van. In many parts of Europe its easy to find at normal fuel stations that sell LPG, whilst some fuel stations in Norway/ Sweden have LPG, many outlets are in industrial estates, almost all self service.
As you get further north the LPG points are fewer. There are around 70 outlets in Norway, 60 of these are in the south.

way of adding a switch of some description

An isolator switch could be added to either battery or both.

Panel Mount Miniature Battery Isolation Switch - 100A

Miniature panel mount battery isolation / master switch. 100A continuous, 150A intermittent. M6 terminals. Ideal for isolating campervan domestic circuits.

www.12voltplanet.co.uk

Usettings via the app.

These are not ideal. Since the solar won't be a big contribution its perhaps not too critical. The designers of your controller have different terms for charging than the normal, suggest you change to the following,
Equilization duration 60 min
Equilisation voltage 14.2 volts
Bulk duration 300 min ( its strange for a solar controller to time the bulk process, I assume this is the maximum)
Bulk volts 14.2 volts
Bulk return 13.2 volts
Float volts 13.5 volts
Low volts disconnect 12.0 volts ( if the battery gets fully discharged it enters protection, can be difficult to 'start up' again
Low disconnect resume 12.4 volts

Alternator charging.
Charging lithium from the vehicle alternator requires a different set up than a acid battery. A lead battery is, to some extent, charge current self-limiting, and tollerent to over/ under charge volts. Lithium batteries , with a much lower internal resistance, can 'pull' higher currents from the vehicle charging system, perhaps overloading the alternator and wiring. It's recommended to install a battery to battery charger, configured for lithium, to limit the charge current, provide an ideal charge voltage, and terminate charging when the battery is 'full'.
Battery state.
Although the solar controller displays battery volts, its not a reliable indicator of battery capacity, as the lithium battery voltage does not change much over its capacity range. Its recomended to install a battery monitor, to act as a kind of battery 'fuel guage'. The Victron smart shunt, displaying over Bluetooth and phone app, is useful.
Lithium battery capacity chart for a rested battery, no load or charge,

 

[Beavo]

I guessed it was a small van. In many parts of Europe its easy to find at normal fuel stations that sell LPG, whilst some fuel stations in Norway/ Sweden have LPG, many outlets are in industrial estates, almost all self service.
As you get further north the LPG points are fewer. There are around 70 outlets in Norway, 60 of these are in the south.


An isolator switch could be added to either battery or both.

Panel Mount Miniature Battery Isolation Switch - 100A

Miniature panel mount battery isolation / master switch. 100A continuous, 150A intermittent. M6 terminals. Ideal for isolating campervan domestic circuits.

www.12voltplanet.co.uk

These are not ideal. Since the solar won't be a big contribution its perhaps not too critical. The designers of your controller have different terms for charging than the normal, suggest you change to the following,
Equilization duration 60 min
Equilisation voltage 14.2 volts
Bulk duration 300 min ( its strange for a solar controller to time the bulk process, I assume this is the maximum)
Bulk volts 14.2 volts
Bulk return 13.2 volts
Float volts 13.5 volts
Low volts disconnect 12.0 volts ( if the battery gets fully discharged it enters protection, can be difficult to 'start up' again
Low disconnect resume 12.4 volts

Alternator charging.
Charging lithium from the vehicle alternator requires a different set up than a acid battery. A lead battery is, to some extent, charge current self-limiting, and tollerent to over/ under charge volts. Lithium batteries , with a much lower internal resistance, can 'pull' higher currents from the vehicle charging system, perhaps overloading the alternator and wiring. It's recommended to install a battery to battery charger, configured for lithium, to limit the charge current, provide an ideal charge voltage, and terminate charging when the battery is 'full'.
Battery state.
Although the solar controller displays battery volts, its not a reliable indicator of battery capacity, as the lithium battery voltage does not change much over its capacity range. Its recomended to install a battery monitor, to act as a kind of battery 'fuel guage'. The Victron smart shunt, displaying over Bluetooth and phone app, is useful.
Lithium battery capacity chart for a rested battery, no load or charge,

Wow, thank you for taking the time to share all that information.

Our trip plans change on a daily basis.
We've been talking about The northern lights etc for a while but I'm beginning to think that it might be a bit ambitious with our current setup.
Thinking it might be better to do Scandinavia as a summer trip although the chances of seeing the lights is almost nil.

Thanks again

 

[mikefitz]

chances of seeing the lights is almost nil.

In summer yes, there is no 'dark' in the North.
September and October is a good time, the snow is not back yet and you have darkness. You may have to get north, as far as Tromso, to have a good chance of seeing the lights. It's a long road trip but well worth it, in summer there won't be Northern lights but you get 24 hours of solar.

 

[Beavo]

In summer yes, there is no 'dark' in the North.
September and October is a good time, the snow is not back yet and you have darkness. You may have to get north, as far as Tromso, to have a good chance of seeing the lights. It's a long road trip but well worth it, in summer there won't be Northern lights but you get 24 hours of solar.

Yep, we might try April next year, either that or wait until September as you say.
Great advice, thank you.