Where is house battery isolator lead connected to house battery?

[dogtubs]

Hello, I’m in the progress of ditching the AGM house battery located under the van. Have replaced it 3x since 2002, not bad battery life I guess. But jacking that beast down and up is a real chore. So, I’m installing a LiFePO4 in the “trunk” (a SMB addition) and running 4/0 wire to a new charger/inverter.

What I don’t understand is how the old AGM house battery was getting a charge off the alternator. The original 2/0 wires run from where the old AGM was located, through the frame, and to the old charger/inverter under the gaucho. Both are single wires.

I have a Blue Sea ML-ACR charging relay under the hood that has a terminal that connects to the house battery. Somewhere this wire must be connected to the positive lead on the old AGM under the van, but there’s only one positive lug under the van. This wire must be connected where I can’t see it - like in the frame somewhere? Anybody know where the house battery lead from the Blue Sea is connected to the positive 2/0 wire that connects to the old AGM battery? I can’t find it.

Thanks for any help!

 

[1der]

You are correct that there should be a positive wire from the Blue Sea ACR connection in the circuit to the AGM battery. It is possible and likely that the ACR positive is running to the positive terminal or a busbar near the Inverter/charger.

Of course, the Blue Sea will be replaced by a DC to DC charger in your Lith configuration but it possibly would be more convenient to repurpose the ACR wire run ( provided it is of sufficient gauge) in the DC to DC application.

 

[geoffff]

Are you sure there isn't another hole through the floor under the gaucho for the alternator charging wire?

My 2004 and 2005 vans are set up a bit different, without a Blue Sea ML-ACR. My vans are both the "50" layout, with 3 holes through the floor under the rear bench seat -- where the Sure Power separator/isolator, Inteli Power shore power charger, and Mark PV solar charger live.

My cables through the floor are: two 2/0 AWG cables (red+black) to the house battery, and a red 2 AWG cable that goes to the engine/alternator for charging.

 

[dogtubs]

Are you sure there isn't another hole through the floor under the gaucho for the alternator charging wire?

My 2004 and 2005 vans are set up a bit different, without a Blue Sea ML-ACR. My vans are both the RB layout, with 3 holes through the floor under the rear seat -- where the Sure Power separator/isolator, Inteli Power shore power charger, and Mark PV solar charger live.

My cables through the floor are: two 2/0 AWG cables (red+black) to the house battery, and a red 2 AWG cable that goes to the engine/alternator for charging.

Hello Ray & Geofff,

Thanks for your replies. In my van, under the gaucho, there are two 2/0 (red+black) cables through the floor. These connect the house battery to the inverter/charger.

From the inverter positive terminal there is a 2 AWG wire that goes to a Hi-Amp 60 Amp Buss where 3 other large wires are connected.

With everything disconnected, a continuity test confirmed that the house battery wire from the ML-ACR is connected to the Hi-Amp Buss.

I don’t understand how it works, but I’m assuming that when the ML-ACR connects, it pushes alternator charge to the Hi-Amp Buss where it goes to the inverter and then to the house battery.

Is my assumption kinda correct?

Thanks!
Johnny C.

 

[1der]

Almost right

It pushes the charge to the inverter Hi Amp Buss to the Inverter positive terminal (not through the inverter) then to the battery. The positive post on the inverter is simple a pass through/connection point between the 2AWG wire connection and the 2/0 cable to the battery.

 

[dogtubs]

Almost right

It pushes the charge to the inverter Hi Amp Buss to the Inverter positive terminal (not through the inverter) then to the battery. The positive post on the inverter is simple a pass through/connection point between the 2AWG wire connection and the 2/0 cable to the battery.

Ah, got it. That was confusing. I was thinking it must go thru the inverter, but I understand now.
I’ll sleep better tonight
Thanks!

 

[dogtubs]

Almost right

It pushes the charge to the inverter Hi Amp Buss to the Inverter positive terminal (not through the inverter) then to the battery. The positive post on the inverter is simple a pass through/connection point between the 2AWG wire connection and the 2/0 cable to the battery.

Ray,

Can’t sleep again…

If the Sportsmobile wiring simply uses the + inverter lug as a connection point for the ML-ACR 2 AWG cable and the 2/0 battery cable, wouldn’t it be more efficient to just connect the 2 AWG directly to the battery?

 

[1der]

No difference. Actually, in some ways it is "more" efficient since the last 3 to 4 feet is a 2/0 much lower resistance cable vs the 2AWG running from the front.

The inverter terminal is literally just a connection. The inverter itself is not drawing anything if not on. If the inverter is on, it is drawing the same regardless if the connection is at the battery or at the inverter terminal.

 

[dogtubs]

No difference. Actually, in some ways it is "more" efficient since the last 3 to 4 feet is a 2/0 much lower resistance cable vs the 2AWG running from the front.

The inverter terminal is literally just a connection. The inverter itself is not drawing anything if not on. If the inverter is on, it is drawing the same regardless if the connection is at the battery or at the inverter terminal.

Ray, thanks for your reply! Now I’m stuck on whether or not I need a DC-DC charger. In addition, please review the following for any knee jerks…

I had the original Sportsmobile setup:
200Ah AGM battery, 200 amp fuse, 1500W inverter/charger, All lconnected with 2/0 wire. Isolator - upgraded to ML-ACR

Now I have:
300Ah LiFePO4 House Battery
Connected to 400 amp ANL Fuse
Connected to 5000W Inverter/Charger
All connections 4/0 wire.

300W Solar Panels
Connected to 40 amp Solar Controller
Connected to House Battery with 8 AWG wire (ok?)

Now the question is do I need to replace the ML-ACR with a DC-DC Charger?
The wire from the existing ML-ACR to the House Battery is 2 AWG, it’s the length of the van and tucked into various harnesses. Is it worth pulling bigger wire?
If I need a DC-DC Charger - what size?
I’m assuming the alternator is 130-136 Amps

Thanks for your thoughts!

 

[geoffff]

Be prepared to learn a lot! I've also been diving deep learning all this electrical stuff for my van, over the past few months.

2 AWG cable: it can handle 150A, but with resistive losses you probably want to keep the current flow under 35A. There are tables where you can look up this stuff. I ended up keeping my old 2 AWG cable.

DC-DC charger: Though a few people out there charge their lithium batteries without a DC-DC charger, the general understanding is that it's not a good idea. For one thing, you need to limit the charging rate.

Alternator: Your alternator may be 130A, but it only generates about 80A at idle. Then there are other loads, including the van itself (about 15A), and perhaps headlights (28A), and what about airing back up with your compressor? (65A). If you exceed 80A draw at idle, your alternator will be running hard (hot) and your starter battery will need take up any slack (while it can). In the end, I decided to go with a 30A DC-DC charger. I may also upgrade my alternator in the future.

Here is the thread with me working on my electrical system plan, and doing lots of measurements of my alternator. Another Lithium Battery Upgrade - Check My Work?

Here is my current schematic:

 

[dogtubs]

Be prepared to learn a lot! I've also been diving deep learning all this electrical stuff for my van, over the past few months.

2 AWG cable: it can handle 150A, but with resistive losses you probably want to keep the current flow under 35A. There are tables where you can look up this stuff. I ended up keeping my old 2 AWG cable.

DC-DC charger: Though a few people out there charge their lithium batteries without a DC-DC charger, the general understanding is that it's not a good idea. For one thing, you need to limit the charging rate.

Alternator: Your alternator may be 130A, but it only generates about 80A at idle. Then there are other loads, including the van itself (about 15A), and perhaps headlights (28A), and what about airing back up with your compressor? (65A). If you exceed 80A draw at idle, your alternator will be running hard (hot) and your starter battery will need take up any slack (while it can). In the end, I decided to go with a 30A DC-DC charger. I may also upgrade my alternator in the future.

Here is the thread with me working on my electrical system plan, and doing lots of measurements of my alternator. Another Lithium Battery Upgrade - Check My Work?

Here is my current schematic:

Be prepared to learn a lot! I've also been diving deep learning all this electrical stuff for my van, over the past few months.

2 AWG cable: it can handle 150A, but with resistive losses you probably want to keep the current flow under 35A. There are tables where you can look up this stuff. I ended up keeping my old 2 AWG cable.

DC-DC charger: Though a few people out there charge their lithium batteries without a DC-DC charger, the general understanding is that it's not a good idea. For one thing, you need to limit the charging rate.

Alternator: Your alternator may be 130A, but it only generates about 80A at idle. Then there are other loads, including the van itself (about 15A), and perhaps headlights (28A), and what about airing back up with your compressor? (65A). If you exceed 80A draw at idle, your alternator will be running hard (hot) and your starter battery will need take up any slack (while it can). In the end, I decided to go with a 30A DC-DC charger. I may also upgrade my alternator in the future.

Here is the thread with me working on my electrical system plan, and doing lots of measurements of my alternator. Another Lithium Battery Upgrade - Check My Work?

Here is my current schematic:

Geofff,
No kidding, this stuff is overwhelming & expensive.

I read through your thread and absorbed what I could, but there’s a lot there. Thanks.

First, it looks like I’ll be returning the 5000W inverter/charger. As you, my 110V needs are minimal (1000W microwave that I use very seldom, and I may add a coffee pot in the future). So, looking at a 2000 or 3000W inverter/charger.

Looking at your recent diagram and the connection from starting bat to BS11001 to DC-DC charger…

1. Is there any way I could use my ML-ACR in place of the BS11001? For instance with the ML-ACR always set to connect?
2. If I scrap the ML-ACR and install a BS11001 it would need to be under the hood, where the ML-ACR lives. Is this ok?
3. If I scrap the ML-ACR and don’t install a switch (like the BS1101), would I connect the starting battery directly to the house battery?
4. I assume the Victron 30 amp DC-DC charger is bidirectional allowing the inverter/charger to trickle charge the starting battery. Is this correct?

Do you like the 500 amp Victron SmartStunt?

Many thanks for your help!

 

[Eatmorefish]

Your ML ACR may not be compatible with lithium, Blue Seas has great tech support, give them a call and they may talk you thru it.

 

[dogtubs]

Geofff,
No kidding, this stuff is overwhelming & expensive.

I read through your thread and absorbed what I could, but there’s a lot there. Thanks.

First, it looks like I’ll be returning the 5000W inverter/charger. As you, my 110V needs are minimal (1000W microwave that I use very seldom, and I may add a coffee pot in the future). So, looking at a 2000 or 3000W inverter/charger.

Looking at your recent diagram and the connection from starting bat to BS11001 to DC-DC charger…

1. Is there any way I could use my ML-ACR in place of the BS11001? For instance with the ML-ACR always set to connect?
2. If I scrap the ML-ACR and install a BS11001 it would need to be under the hood, where the ML-ACR lives. Is this ok?
3. If I scrap the ML-ACR and don’t install a switch (like the BS1101), would I connect the starting battery directly to the house battery?
4. I assume the Victron 30 amp DC-DC charger is bidirectional allowing the inverter/charger to trickle charge the starting battery. Is this correct?

Do you like the 500 amp Victron SmartStunt?

Many thanks for your help!

Ok, I’ve scrapped the ML-ACR and replaced it with a Blue Sea 11001. So, those questions are mute.

But, I’m still wondering about the Victron 30 amp DC-DC charger - is it bidirectional allowing the inverter/charger to trickle charge the starting battery?

Do you like the 500 amp Victron SmartStunt?

Anybody want to buy an ML-ACR?

 

[geoffff]

Geofff,
No kidding, this stuff is overwhelming & expensive.

I read through your thread and absorbed what I could, but there’s a lot there. Thanks.

First, it looks like I’ll be returning the 5000W inverter/charger. As you, my 110V needs are minimal (1000W microwave that I use very seldom, and I may add a coffee pot in the future). So, looking at a 2000 or 3000W inverter/charger.

Looking at your recent diagram and the connection from starting bat to BS11001 to DC-DC charger…

1. Is there any way I could use my ML-ACR in place of the BS11001? For instance with the ML-ACR always set to connect?
2. If I scrap the ML-ACR and install a BS11001 it would need to be under the hood, where the ML-ACR lives. Is this ok?
3. If I scrap the ML-ACR and don’t install a switch (like the BS1101), would I connect the starting battery directly to the house battery?
4. I assume the Victron 30 amp DC-DC charger is bidirectional allowing the inverter/charger to trickle charge the starting battery. Is this correct?

Do you like the 500 amp Victron SmartStunt?

Many thanks for your help!

I'm far from an expert. I'm still learning this stuff. Just last night Scalf77 gave me a long critique of my design, pointing out a bunch of mistakes. Below is my updated schematic.

I don't see any reason to put those in the engine compartment. My Sportsmobile originally had its isolator back inside the van, not in the engine compartment. However, I am adding a 200A MRBF terminal block fuse in the engine compartment to protect that long 2 AWG cable under the van. In my original Sportsmobile, there was no protection, and I actually had an engine fire because of it!

The Victron 30 amp DC-DC charger is not bidirectional. Mine is set up only to charge the house battery from the engine. To trickle charge the starter battery, I plan to just plug a cheap 120V trickle charger which I will plug into my inverter output at times. My Victron MultiPlus does have a trickle charger capability, but from what I read it is not appropriate for use with a lithium house battery.

As for the 500 amp Victron SmartStunt, I haven't wired it up yet -- so we will see. I am adding it so I can use the Victron Cerbo GX and a GX Touch 50 display to monitor my battery along with the rest of the system.

I am very much in the middle of this project. All I have wired up so far is the Victron MultiPlus.



I never intended this to get so complicated and expensive. But one thing leads to another...

 

[dogtubs]

I'm far from an expert. I'm still learning this stuff. Just last night Scalf77 gave me a long critique of my design, pointing out a bunch of mistakes. Below is my updated schematic.

I don't see any reason to put those in the engine compartment. My Sportsmobile originally had its isolator back inside the van, not in the engine compartment. However, I am adding a 200A MRBF terminal block fuse in the engine compartment to protect that long 2 AWG cable under the van. In my original Sportsmobile, there was no protection, and I actually had an engine fire because of it!

The Victron 30 amp DC-DC charger is not bidirectional. Mine is set up only to charge the house battery from the engine. To trickle charge the starter battery, I plan to just plug a cheap 120V trickle charger which I will plug into my inverter output at times. My Victron MultiPlus does have a trickle charger capability, but from what I read it is not appropriate for use with a lithium house battery.

As for the 500 amp Victron SmartStunt, I haven't wired it up yet -- so we will see. I am adding it so I can use the Victron Cerbo GX and a GX Touch 50 display to monitor my battery along with the rest of the system.

I am very much in the middle of this project. All I have wired up so far is the Victron MultiPlus.



I never intended this to get so complicated and expensive. But one thing leads to another...

Geofff,
Thanks for the updated schematic. I’m building my system based on your diagram. Thanks for doing all the heavy lifting!

The breaker amperage ratings are driving me crazy.

Ok, no built-in trickle charger for the starting battery. How did Sportsmobile make it charge the starting battery when plugged into shore power?

Part of my problem is trying to figure out what the Sportsmobile electricians were thinking.

I assume that because the DC-DC charger is not bidirectional it keeps the starting battery from being used (isolated) while parked. Is this correct or do you have an isolator some where?

You mentioned “I don't see any reason to put those in the engine compartment.” Well, my isolator (then the ML-ACR) was installed under the hood so now that both are removed I have a loose positive from the starting battery and a loose 2AWG running to the gaucho area. That’s why I want to put the BS1101 under the hood. Make sense?

 

[1der]

""Part of my problem is trying to figure out what the Sportsmobile electricians were thinking.""

Yep, do not go down that rabbit hole.

The bi directional worked for AGM/ Lead Acid. Does not work for Lith thus need for DC to DC. DC to DC does provide isolation. You need to be careful with how to trickle charge your starter (longer discussion)

Install the DC to DC where it fits. You can splice the two positive wires that ran to the ACR in the engine compartment together.

I do not see a good reason to put the BS 1101 in your system except to be able to disconnect your Lith battery.

More discussion needed around how to reawaken a Lith BMS when it triggers due to protection mode.

 

[dogtubs]

""Part of my problem is trying to figure out what the Sportsmobile electricians were thinking.""

Yep, do not go down that rabbit hole.

The bi directional worked for AGM/ Lead Acid. Does not work for Lith thus need for DC to DC. DC to DC does provide isolation. You need to be careful with how to trickle charge your starter (longer discussion)

Install the DC to DC where it fits. You can splice the two positive wires that ran to the ACR in the engine compartment together.

I do not see a good reason to put the BS 1101 in your system except to be able to disconnect your Lith battery.

More discussion needed around how to reawaken a Lith BMS when it triggers due to protection mode.

Ok, no BS1101. As far slicing the two wires together that were on the ACR, would it be reasonable to put the 200A MRBF terminal block fuse at that location? I DON’T want an engine fire!

 

[dogtubs]

Ok, no BS1101. As far slicing the two wires together that were on the ACR, would it be reasonable to put the 200A MRBF terminal block fuse at that location? I DON’T want an engine fire!

Or some 200 amp fuse?

 

[1der]

The fuse/breaker should be at the battery or source of 12v (alternator terminal)

 

[Scalf77]

More discussion needed around how to reawaken a Lith BMS when it triggers due to protection mode.

I have installed a momentary switch that I connect to the Vbatt line of SmartShunt (connect to Lithium House battery), the other side goes to the AUX connection of the SmartShunt which I usually attach to the start bat input of DC-DC Charger.