Alternator charging combo with solar panel via B2B and isolator

[Logan]

I have read thru many posts but cant find one that relates to my situation.
If this has been answered in another post or thread please direct me to it.

I have a 96 ford transit that I think had a dual battery system from the factory with what I think is an isolater. I think it was called a smart charger, perhaps. The label is long gone off it.
I draw power for leds, laptop and portable fridge (12V-3/6A) from the second battery and the start battery remains the same voltage and the second battery goes flat and then recharges either from solar or the alternator when Im driving. Cloudy days I simply let the diesel engine idle and do what I need to do on the laptop or to get my fridge down to temp and then turn everything off overnight.

The lead acid is most likely quite damaged as I have accidental run it down to under 10 V several times by not paying attention to the volt guage.

The second battery is a lead acid, unsure of size as no labels visible. I'd hazard a guess probably 25ah-40ah.
I am awaiting the arrival in the next few days of a new lithium ion 150ah battery. Being as the van is short wheelbase and limited roof space I have just one solar panel that is about ten years old and (open circuit) middle of sunny day putting 33v and 8.5A.

It also has fitted one of those blue $20 10A solar chargers that Will says "looks like a toy" in one of his videos. I have a mppsolar unit coming in the mail.

My question is the charging of the 150A LI.
I am on the road (stealth van life) and have no access to mains power to use via the inbuilt charger in the mppsolar unit at this sime so I would like to simply run a B2B dc-dc charger from the second lead acid battery straight to the solar inputs connections going into the mppsolar.
My thoughts being the existing lead acid battery and smart isolater will protect and manage the alternator side of things and the power going into the mppsolar unit via the same connection as the power coming from the solar panel will be managed by the mppsoalr unit and charge the 150A li battery safely.
Is this correct?
and if so will any B2B charger do the job?

I dont do a lot of miles but it would be great if the few miles I do help top up the Li battery.

Thanks in advance.

P.S. I'm willing to spend $200 to $800 for a viable working easy drop in solution.

 

[FilterGuy]

I can't quite follow what you are describing, can you provide a diagram?

 

[Logan]

I can't quite follow what you are describing, can you provide a diagram?

sorry dont have the tech skills to do a drawing.
which part dont you understand and i can rewrite that bit in a different way?

 

[Dzl]

Like Filterguy, I'm not 100% clear on what your are describing/asking.
Am I correct in understanding you are wanting to run a DC-DC (Battery to Battery) charger from your starting battery (and alternator) through your MPP all-in-one's solar charge controller, to your lithium house battery bank?

If so why not just use the DC-DC (B2B) charger, afaik, the situation you are describing is precisely what B2B chargers like this one from Victron and this one from Renogy are designed to do without jury-rigging anything.

 

[FilterGuy]

OK..... This is what I *think* you described for current set-up

\

If you are buying a charge controller, DC-DC converter and 150Ah battery, this is what you would end up with


Warning: These are conceptual diagrams and do not show all details like fuses, and wire sizes.

 

[Oneeyedjackass]

I had a similar install on our RV. I went with a Victron Orion-tc smart dc-dc charger (From Bay Marine) I already have Victron solar controller & bat. temp. that works via bluetooth. You could also go with Renogy DCC50S charger. The main idea (as i understand) is to save your alternator.
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/
https://www.12voltplanet.co.uk/auxiliary-battery-charging-in-vehicles-with-smart-alternators.html

 

[FilterGuy]

Note: Renogy makes a DC-DC charger that also has an MPPT built in. You may want to look into that.

 

[Logan]

OK..... This is what I *think* you described for current set-up

View attachment 10793\

If you are buying a charge controller, DC-DC converter and 150Ah battery, this is what you would end up with
View attachment 10794

Warning: These are conceptual diagrams and do not show all details like fuses, and wire sizes.

Thanks for your reply.
Yes, that is what the current setup is, if the "combiner" in your diagram is a 'smart charger' that separates the two existing lead acid batteries (starter and house?) and only connects the house battery to the alternator car circuit when the house battery is needing a charge.
So the vehicles alternator never accesses the house battery other than to charge it, and the start battery never accesses the house battery ever.

My friend who has limited skills did this image for me.

This is the question I was asking in the OP.

Is this safe for my alternator, mppt and new LiFePo battery, to add a dc-dc charger in this configuration?
Or do I need to add other components to ensure the safety (not counting wire size and fuses). ?

 

[Logan]

I had a similar install on our RV. I went with a Victron Orion-tc smart dc-dc charger (From Bay Marine) I already have Victron solar controller & bat. temp. that works via bluetooth. You could also go with Renogy DCC50S charger. The main idea (as i understand) is to save your alternator.
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/
https://www.12voltplanet.co.uk/auxiliary-battery-charging-in-vehicles-with-smart-alternators.html

Thanks for your reply, yes, protecting the alternator is the main aim as being a 1996 new ones off the shelf are likely not available.
Also dont want to damage the mppsolar unit or the battery, of course. In the future I will instal a second marine alterator, as I want to go to 4x150Ah, 24v system). So this solution with dc-dc is just a temporary for the next 6-12 mths.

 

[FilterGuy]

The short answer is NO. That will not work well.

However, If you hook the output of the DC-DC charger to the battery, it should work OK..... maybe.

What is the reason for leaving the existing house battery in place? Are there things it is powering?
What kind of DC-DC charger do you have? What turns it on? If it is turned on by a signal from the key being on, it may work OK. If it is turned on when it sees charging level voltages, it may work OK. If it is always on, it will try to totally drain the lead acid house battery and destroy it.

 

[Logan]

Like Filterguy, I'm not 100% clear on what your are describing/asking.
Am I correct in understanding you are wanting to run a DC-DC (Battery to Battery) charger from your starting battery (and alternator) through your MPP all-in-one's solar charge controller, to your lithium house battery bank?

If so why not just use the DC-DC (B2B) charger, afaik, the situation you are describing is precisely what B2B chargers like this one from Victron and this one from Renogy are designed to do without jury-rigging anything.

Thanks for your reply, I've added a new drawing a friend did for me. Yes, sort of, only running from my existing house lead acid via dc-dc charger to my mppsolar unit.
I'm hoping that the house lead acid battery and the smart charger isolator inbetween the lead acid house battery and the alternator will give some extra protection against any damage to the alternator.

 

[Logan]

The short answer is NO. That will not work well.

However, If you hook the output of the DC-DC charger to the battery, it should work OK..... maybe.

What is the reason for leaving the existing house battery in place? Are there things it is powering?
What kind of DC-DC charger do you have? What turns it on? If it is turned on by a signal from the key being on, it may work OK. If it is turned on when it sees charging level voltages, it may work OK. If it is always on, it will try to totally drain the lead acid house battery and destroy it.

I thought by leaving the lead acid house battery in place would provide some extra alternator protection as the smart charger would still be in place. Also I'm concerned that the one solar panel will not provide the power I need and be able to charge the LiPo battery at the same time, especially on cloudy days. The lead acid house battery currently runs my non-car electrics and I would use it as a backup for power if I have to let the lipo battery charge on the solar panel and idle my engine to feed the lead acid house battery with the alternator so I can continue to work on my computer.

Also why I am exploring a dc-dc /alternator option as I know Will is dead against this last option and perhaps the smart chager aspect would make a difference.
I have not purchased a dc-dc yet but I can certainly buy one that is only active when key on as I was aware the battery would get sucked dry when engine off.

 

[Logan]

I am going to go rewatch Wills video now on this as I know a bit more now than I did when I first watched it weeks ago.

 

[Dzl]

Logan, I think you are overcomplicating things, there are products made specifically for what you are trying to do.

Here is a diagram from the Victron Orion-TR Smart DC-DC Charger manual:

This product is specifically designed to safely charge lithium batteries from the vehicles charging system and to protect the vehicle's alternator from damage. You woudln't need to run it through your MPP controller or through another lead acid battery.

@Justin Laureltec is knowledgeable about this product (and is a licensed Victron tech and distributor I believe) has started a thread on this product here

 

[Logan]

Logan, I think you are overcomplicating things, there are products made specifically for what you are trying to do.

Here is a diagram from the Victron Orion-TR Smart DC-DC Charger manual:
View attachment 10859
This product is specifically designed to safely charge lithium batteries from the vehicles charging system and to protect the vehicle's alternator from damage. You woudln't need to run it through your MPP controller or through another lead acid battery.

@Justin Laureltec is knowledgeable about this product (and is a licensed Victron tech and distributor I believe) has started a thread on this product here

Thanks for your reply, I remember seeing a video by Will about that unit but not the specific details as it was some time ago.
I will go check out Justins thread now. Thanks

 

[Logan]

Logan, I think you are overcomplicating things, there are products made specifically for what you are trying to do.

Here is a diagram from the Victron Orion-TR Smart DC-DC Charger manual:
View attachment 10859
This product is specifically designed to safely charge lithium batteries from the vehicles charging system and to protect the vehicle's alternator from damage. You woudln't need to run it through your MPP controller or through another lead acid battery.

@Justin Laureltec is knowledgeable about this product (and is a licensed Victron tech and distributor I believe) has started a thread on this product here

am I right in assuming if I purchase one of these units that are a lower amperage then I can create even more safety for my alternator given that it should be able to handle 200w of spot lights so should be able to handle 200w via this unit?

Is there a specific reason why I can't run it off the lead acid house battery, and have to run it off my starter battery?

 

[Logan]

Thanks for your reply, I remember seeing a video by Will about that unit but not the specific details as it was some time ago.
I will go check out Justins thread now. Thanks

Will was talking about the mppt version from that company

 

[FilterGuy]

am I right in assuming if I purchase one of these units that are a lower amperage then I can create even more safety for my alternator given that it should be able to handle 200w of spot lights so should be able to handle 200w via this unit?

Is there a specific reason why I can't run it off the lead acid house battery, and have to run it off my starter battery?

I believe the Victron is voltage controlled (It turns on when it sees the high level alternator voltage. In the diagram you did you have the battery protect between the Alternator and the DC-DC charger. I assume the voltage will be high enough on the output side of the battery protect to trigger the DC-DC Charger, but it is something to check.

I *think* this is now what you are proposing:

This would *probably* work, but if the LiFePO4 battery is drained, it would not use the lead acid house battery till the engine is running.
Furthermore, the battery protect is not protecting the alternator any more than just the DC-DC charger would. Consequently, you would do just as well to wire it this way:



However, the lead-acid house battery is only charged by the alternator (not the solar). Consequently, I would dump the lead acid house battery and simplify everything like this:

 

[Bob B]

I was thinking about doing something similar with a unit that has multiple MPPT inputs. What I found was that most .... maybe all ... MPPT charge controllers won't start charging until they see .... battery voltage +5 V on their input.

 

[Logan]

However, the lead-acid house battery is only charged by the alternator (not the solar). Consequently, I would dump the lead acid house battery and simplify everything like this:

Thanks for the time and effort you are going to with the diagrams.
This image above is my preferred. I'm aware that the house battery is not connected to the solar, only the engine.

A few questions to try and fine tune my understanding.
1. In the image above when the vehicle is being driven will "load 2" be drawing from the charger or the battery?
2. Is the DC charger connected to the same wire that is connected to the "load out" on the mppt?
Or is it more correct to say: DC Load 2, mppt load out and the LiFPo are all connected together?

I had always assumed that mppt had a load out and a battery out like the $20 PWM that is fitted on my van at present.
It however has a "load out" but is not connected, it has been wired to pull load straight from the battery which I have seen the load draw the lead acid house battery below 10V if I am not watching the volt meter because the pwm can not disconnect the power as the load is not being pulled via the load terminal on the pwm.
So I assume I have to pull the load thru the load out on the mppt or am I missing something?