Lead acid and Lifepo4 with switch between

[IvanB77]

Hi, i am new to the forum and could not find answers on my question so i will try here.

I have a 2006 Knaus WEINSBERG Imperial on a Renault master mk2 chasis, have a Calira EVS 30/20 -DS/UI electroblock that has 2 x 100ah lead acid batteries, the charger for those can do only lead and agm, i now have made a Diy 12v 280ah Lifepo4 battery that i also use as a backup or extending battery for my Ecoflow delta mini power bank.

So, i wish to be able to connect my diy Lifepo4 battery to my old lead acid motorhome system, when low on lead acid battery bank i can switch over to my Lifepo4 bank, could i make this happen with just a 1-2-off disconnect switch, also at what point to make this connection is the best?

Updated, i just bought a battery isolator with afd, where can i hook up the cables that goes to f1 and f2 in picture diagram below?

 

[mikefitz]

Details of your motorhome 'ElectroBlock' and the method of alternator charging, ( combining relay or battery to battery charger) would be helpful. Also the age and model of motorhome and the base vehicle type.
It's possible the AC charger could charge lithium on the lead setting but alternator charging may need a battery to battery, DC to DC, charger added. Since you have the skills to build a battery pack it should be within your capability to make the necessary changes. Often this needs chargers upgrading and the necessary fuse and cable changes.
You may need to consider low temperature charge disable or battery heating.

Mike

 

[Sirtate]

Just to clarify;
You would like to continue to use the Flooded Lead Acid House battery for most of the time and use the LiPo4 bank when it is exhausted?

If that is the case, you are asking how to tie the two banks together to achieve this goal, as well as charge the LiPo4 bank when not in use?

I assume the FLA bank has a nominal voltage of 12v, as does the chassis charging system.

There are switches available that would do this (1-2-off, as you say)... The battery banks can share the negative pole, the switch needs to be on the positive side.
Proper fusing is a must, between both batteries and the switch.

This would allow you to choose which bank to draw your loads from...

Charging is a bit different.
Charging voltages for FLA and LiPo4 are a little bit different. An FLA charging profile will not get LiPo4 fully charged. (some would say that isn't a bad thing).

To that End, the existing charger could be used, as long as you understand the limitations of a FLA profile on LiPo4 Batts. (cold temperature charging can ruin LiPo4 Batts. Anything below 2C)
To do that, you *Could* use a 4 way switch (1-2-BOTH-Off), using the switch on BOTH to charge both banks, either when running the Traction Engine's Alternator, or plugged into shore power.
This setup could cause issues when only one battery bank is at a significantly lower state of charge than the other, high current flows could occur between the banks in this state.

The more elegant solution is to find a DC-DC battery charger for the LiPo4 bank. Power it from the FLA side. It should have a low voltage cut-off, as well as temperature awareness. Use your original 3 position switch for load switching, and make sure there's an easy way to stop the charger when the LiPo4 bank is in use. (a simple switch beside the 1-2-off switch would do it)

 

[IvanB77]

Details of your motorhome 'ElectroBlock' and the method of alternator charging, ( combining relay or battery to battery charger) would be helpful. Also the age and model of motorhome and the base vehicle type.
It's possible the AC charger could charge lithium on the lead setting but alternator charging may need a battery to battery, DC to DC, charger added. Since you have the skills to build a battery pack it should be within your capability to make the necessary changes. Often this needs chargers upgrading and the necessary fuse and cable changes.
You may need to consider low temperature charge disable or battery heating.

Mike

Thanks, i have updated the thread now with your suggestions.

 

[IvanB77]

Just to clarify;
You would like to continue to use the Flooded Lead Acid House battery for most of the time and use the LiPo4 bank when it is exhausted?

Yes

If that is the case, you are asking how to tie the two banks together to achieve this goal, as well as charge the LiPo4 bank when not in use?

Its not so important at this moment to charge Lifepo4 so just the FLA

I assume the FLA bank has a nominal voltage of 12v, as does the chassis charging system.

There are switches available that would do this (1-2-off, as you say)... The battery banks can share the negative pole, the switch needs to be on the positive side.
Proper fusing is a must, between both batteries and the switch.

Have updated my thread with some pictures and additional information, have bought a battery isolator with ADF, se picture, struggling to find easy way to connect generator / regulator cable to f1 and f2 as explained on diagram

This would allow you to choose which bank to draw your loads from...

Charging is a bit different.
Charging voltages for FLA and LiPo4 are a little bit different. An FLA charging profile will not get LiPo4 fully charged. (some would say that isn't a bad thing).

To that End, the existing charger could be used, as long as you understand the limitations of a FLA profile on LiPo4 Batts. (cold temperature charging can ruin LiPo4 Batts. Anything below 2C)
To do that, you *Could* use a 4 way switch (1-2-BOTH-Off), using the switch on BOTH to charge both banks, either when running the Traction Engine's Alternator, or plugged into shore power.
This setup could cause issues when only one battery bank is at a significantly lower state of charge than the other, high current flows could occur between the banks in this state.

The more elegant solution is to find a DC-DC battery charger for the LiPo4 bank. Power it from the FLA side. It should have a low voltage cut-off, as well as temperature awareness. Use your original 3 position switch for load switching, and make sure there's an easy way to stop the charger when the LiPo4 bank is in use. (a simple switch beside the 1-2-off switch would do it)

 

[Sirtate]

Yes

Its not so important at this moment to charge Lifepo4 so just the FLA

Have updated my thread with some pictures and additional information, have bought a battery isolator with ADF, se picture, struggling to find easy way to connect generator / regulator cable to f1 and f2 as explained on diagram

The generator is 12v? (ie; a vehicle alternator?). If it is a household current generator, it shouldn't go anywhere near this switch.

That switch is a 3 terminal switch. There is a Common terminal and terminals 1 and 2.
f1 and f2 are just feedback posts for voltage regulators, either internal on some Alternators, or external... They aren't for a charging circuit.

This switch would be placed electrically between the wire going to the House Battery (B2) (the COM post on the switch) and using new leads the positive post on the House battery (1) and the new LiPo4 Batt (2)...

I wouldn't play with adding a separate charging system, the Camper's system appears robust enough.
(I had to laugh, I was working my way through the German section of the guidebook, scraping the rust off my almost 40yr old German I learned when i visited Baden-Soellingan with the RCAF, and I then found the English section!)
You could leave the switch in the position for the existing FLA Batt, and the Camper's electrical system wouldn't know the difference.
Likewise, you could isolate the FLA Batt, and use/charge the LiPo4 Batt by using position 2... either when plugged into shore power or driving.

 

[IvanB77]

The generator is 12v? (ie; a vehicle alternator?). If it is a household current generator, it shouldn't go anywhere near this switch.

12v in my RV

That switch is a 3 terminal switch. There is a Common terminal and terminals 1 and 2.
f1 and f2 are just feedback posts for voltage regulators, either internal on some Alternators, or external... They aren't for a charging circuit.

Just for extra safety, i would not switch while having the engine running but i could not find switch without here in town, so i may be setting it up, anyone know if it does work without wiring it up or not?

This switch would be placed electrically between the wire going to the House Battery (B2) (the COM post on the switch) and using new leads the positive post on the House battery (1) and the new LiPo4 Batt (2)...

I wouldn't play with adding a separate charging system, the Camper's system appears robust enough.
(I had to laugh, I was working my way through the German section of the guidebook, scraping the rust off my almost 40yr old German I learned when i visited Baden-Soellingan with the RCAF, and I then found the English section!)
You could leave the switch in the position for the existing FLA Batt, and the Camper's electrical system wouldn't know the difference.
Likewise, you could isolate the FLA Batt, and use/charge the LiPo4 Batt by using position 2... either when plugged into shore power or driving.

I should have told you it has English, sorry for that!

One guy told me i could just hook up the Lifepo4 with my existing FLA battery but would not that make issues

 

[mikefitz]

Switch issues.
The switch you have is intended to connect an alternator, usually a marine alternator, to the DC distribution system. The switch options are: battery 1 or battery 2, or both 1 and 2. There is also an off position where both batteries are isolated from the DC system. Because an alternator can be damaged if a battery is disconnected whilst the alternator is operating, the switch has provision to disable the alternator via connections F1 and F2, these allow disconnection of the alternator field current.
For your motorhome application this is complexity is not needed.

Your requirements.

1. Simple connection to the existing lead acid battery, no AC or alternator charging.
Simply connect in parallel with your lead acid battery with no other wiring modifications. You could use the switch, 'common' to lead acid positive, '1' to lithium positive, lithium negative to system negative.
2. Using the AC charger.
The AC charger at 14.4 absorption and 13.8 float with 4 hours absorption is not ideal for lithium but could be used . I suggest manually terminating charge once the voltage has exceeded 14.0 volts.
The reliability of the charger designed for lead batteries used for lithium is questionable. It may or may not be able to function reliably as it will be operating at maximum capacity continuously over the charge cycle.
3. Alternator charging.
The motorhome electronics simply connects the starter battery and engine battery in parallel when the engine is running. Since the system is designed for a low charge current that lead batteries will take, typically in the order of 20 to 30 amps maximum, the addition of a lithium battery may overload the system circuits, fuses, relays and alternator. The usual practice where lithium charging is required is to use a battery to battery charger. Votronic VCC 12 12 30 . This limits the charge current to 30 amps with a suitable charge profile.

https://www.votronic.de/images/Manuals/04.%20B2B%20Chargers%20Booster/3324_e.pdf.

Comments.

There is no issue connecting the lithium battery in parallel with the existing lead acid where no alternator of engine charging is taking place. The lithium battery will deliver most of the DC load until it gets to a low state of charge, where the lead will start to contribute.

Using the motorhome charging systems will need the above comments reviewed.

Mike

 

[IvanB77]

Switch issues.
The switch you have is intended to connect an alternator, usually a marine alternator, to the DC distribution system. The switch options are: battery 1 or battery 2, or both 1 and 2. There is also an off position where both batteries are isolated from the DC system. Because an alternator can be damaged if a battery is disconnected whilst the alternator is operating, the switch has provision to disable the alternator via connections F1 and F2, these allow disconnection of the alternator field current.
For your motorhome application this is complexity is not needed.

Your requirements.

1. Simple connection to the existing lead acid battery, no AC or alternator charging.
Simply connect in parallel with your lead acid battery with no other wiring modifications. You could use the switch, 'common' to lead acid positive, '1' to lithium positive, lithium negative to system negative.
2. Using the AC charger.
The AC charger at 14.4 absorption and 13.8 float with 4 hours absorption is not ideal for lithium but could be used . I suggest manually terminating charge once the voltage has exceeded 14.0 volts.
The reliability of the charger designed for lead batteries used for lithium is questionable. It may or may not be able to function reliably as it will be operating at maximum capacity continuously over the charge cycle.
3. Alternator charging.
The motorhome electronics simply connects the starter battery and engine battery in parallel when the engine is running. Since the system is designed for a low charge current that lead batteries will take, typically in the order of 20 to 30 amps maximum, the addition of a lithium battery may overload the system circuits, fuses, relays and alternator. The usual practice where lithium charging is required is to use a battery to battery charger. Votronic VCC 12 12 30 . This limits the charge current to 30 amps with a suitable charge profile.

https://www.votronic.de/images/Manuals/04.%20B2B%20Chargers%20Booster/3324_e.pdf.

View attachment 142934

Comments.

There is no issue connecting the lithium battery in parallel with the existing lead acid where no alternator of engine charging is taking place. The lithium battery will deliver most of the DC load until it gets to a low state of charge, where the lead will start to contribute.

Using the motorhome charging systems will need the above comments reviewed.

Mike

Thank you for your clear suggestions and explanation.

Will try this and update when finnish!

 

[IvanB77]

Switch issues.
The switch you have is intended to connect an alternator, usually a marine alternator, to the DC distribution system. The switch options are: battery 1 or battery 2, or both 1 and 2. There is also an off position where both batteries are isolated from the DC system. Because an alternator can be damaged if a battery is disconnected whilst the alternator is operating, the switch has provision to disable the alternator via connections F1 and F2, these allow disconnection of the alternator field current.
For your motorhome application this is complexity is not needed.

Yes, i could only find this design at my local shop, looks like i have to use the F1 and F2 to make this switch to work?

Your requirements.

1. Simple connection to the existing lead acid battery, no AC or alternator charging.
Simply connect in parallel with your lead acid battery with no other wiring modifications. You could use the switch, 'common' to lead acid positive, '1' to lithium positive, lithium negative to system negative.

You mean 'common' to lead acid positive,1 on switch, then 2 to lithium positive, lithium negative to system negative?

2. Using the AC charger.
The AC charger at 14.4 absorption and 13.8 float with 4 hours absorption is not ideal for lithium but could be used . I suggest manually terminating charge once the voltage has exceeded 14.0 volts.
The reliability of the charger designed for lead batteries used for lithium is questionable. It may or may not be able to function reliably as it will be operating at maximum capacity continuously over the charge cycle.
3. Alternator charging.
The motorhome electronics simply connects the starter battery and engine battery in parallel when the engine is running.

Do you mean the motorhome electronics simply connects the starter battery/engine battery to living space battery in parallel when the engine is running?

Since the system is designed for a low charge current that lead batteries will take, typically in the order of 20 to 30 amps maximum, the addition of a lithium battery may overload the system circuits, fuses, relays and alternator. The usual practice where lithium charging is required is to use a battery to battery charger. Votronic VCC 12 12 30 . This limits the charge current to 30 amps with a suitable charge profile.

https://www.votronic.de/images/Manuals/04.%20B2B%20Chargers%20Booster/3324_e.pdf.

View attachment 142934

Will look into that one, thanks!

Comments.

There is no issue connecting the lithium battery in parallel with the existing lead acid where no alternator of engine charging is taking place. The lithium battery will deliver most of the DC load until it gets to a low state of charge, where the lead will start to contribute.

Using the motorhome charging systems will need the above comments reviewed.

Mike