Electrical diagram feedback and ACR help needed

mmrump

New member
Hi, Ive attached my preliminary electrical diagram. It's based on a setup that seems to be relatively vetted on this forum. In addition to having other sets of eyes look at what I'm doing, I'm looking for advice on how to incorporate an automatic start/stop for the inverter that is connected to my starter battery. My understanding is the inverter will draw power unless turned off. I'm only using it as a backup to solar., I don't want to think about it, but I'm struggling to find a solution. I'm looking at Blue Sea ACR's but I'm not sure which one would work and specifically where it would fit in with my setup.

For reference, I have a 2019 144 that does NOT have an auxiliary battery (hence the concern with draining the starter battery).
Here are my questions:

- Is ACR a good solution, or is there something better?
- If I get an ACR, is the inverter necessary, will the ACR keep the batteries happy without the inverter?
- Is there an ACR that can sense the charge when the alternator starts, or will I need to find an ignition connection (if so, where would I find it?)

I'm sure I'll have more questions. I'll also be updating my diagram with wire sizing and lengths for a final review once I get this ACR solved.

Thanks in advance!2019 Sprinter 144 Wiring Diagram.jpg
 

autostaretx

Erratic Member
What's the wire between the Samiex and the Magnum?
Is it 12v, or is it 120v?
Either way, adding an arrowhead to indicate direction of current flow (and labels with voltage) would clarify things.

Can the Samiex also power house loads?

--dick
 

AirJoseph

Member
That's essentially the same as my set up. No ACR required but I have a switch near the drivers seat to turn the 1000 watt inverter on or off as I see fit. In other words, I actively control when the alternator is charging or not. Not automatic but I like it that way.

Btw, I'm not a fan of ACR use for Lithium Batteries as the charging current is not controlled. This may cause a charge rate that is too high for the Lithium batteries and cause damage. A depleted Lithium battery has low internal resistance and will draw current from the alternator and the starter battery at the same time. I stand to be corrected but the available charge current could be in the hundreds of amps.
 
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mmrump

New member
What's the wire between the Samiex and the Magnum?
Is it 12v, or is it 120v?
Either way, adding an arrowhead to indicate direction of current flow (and labels with voltage) would clarify things.

Can the Samiex also power house loads?

--dick
Thanks Dick. I don't have it installed yet, but the wire will be 120v (12/3 AWG). The Samiex will be able to power house loads, but I wont be using it for that purpose. it will mainly be used to charge the battery when solar isn't enough. I'll be updating my diagram with wire guage and directions as a next step. Thank for the feedback.
 

mmrump

New member
That's essentially the same as my set up. No ACR required but I have a switch near the drivers seat to turn the 1000 watt inverter on or off as I see fit. In other words, I actively control when the alternator is charging or not. Not automatic but I like it that way.

Btw, I'm not a fan of ACR use for Lithium Batteries as the charging current is not controlled. This may cause a charge rate that is too high for the Lithium batteries and cause damage. A depleted Lithium battery has low internal resistance and will draw current from the alternator and the starter battery at the same time. I stand to be corrected but the available charge current could be in the hundreds of amps.
AirJoseph - thanks. My primary concern is a situation where I forget to turn it off and drain my starter battery.

If I put an ACR between the starter battery and the Samiex, then wouldn't the Magnum inverter regulate the charge to the house battery?

Thanks for you feedback.
 

AirJoseph

Member
Okay, now I see what you want to accomplish. You are correct that the charger will limit the current. I thought you wanted to use an ACR instead of the Samiex inverter as most people with ACRs have done. Carry on... :)
 

msmolow

2019 Unity CB / 2018 Chas
My primary concern is a situation where I forget to turn it off and drain my starter battery.
How about a Magnum DCLD tied into a 12 volt source? It will turn the inverter on or off based upon the 12 volt signal.
 

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Kevin.Hutch

2011 Mercedes 313 906
I see you are planning to convert 12v to 120v (inverter) then run a 12v to 120v charger, leaving the the inverter permanently connected to the starter battery will drag your starter battery down without the alternator running, if you use it for 120v loads including your charger. The charger would be seen as a permanent load on the inverter switching it permanently on and no current would be available from the much bigger house battery to meet any other 120v loads.

An involved system to replace a DC-DC converter that does the same thing without the overhead of DC/AC-AC/DC voltage conversion.

You would have to remember to switch the 12v side of the inverter as its significant standby current will come from your start battery when there is no alternator charge even with no load, hence the question of the ACR.

An ACR (automatic charging relay) is simply a (VSR) voltage sensing relay and as that name implies it senses the input voltage to a predetermined voltage then turns on. My BEP VSR senses 13.4v for 5 seconds before switching on and switches off when 12.8v for 20 seconds, it has an standby current of 1.8mA that can be manually switched off for storage. Check the spec of any specific VSR/ACR they will be similar as is the B+ connection.

Alternatively a B+ controlled relay before the inverter could be used with a 90A (1000w @12v) relay/solenoid, yet all this is functionality included in the DC/DC converter.
 

Kevin.Hutch

2011 Mercedes 313 906
Btw, I'm not a fan of ACR use for Lithium Batteries as the charging current is not controlled. This may cause a charge rate that is too high for the Lithium batteries and cause damage. A depleted Lithium battery has low internal resistance and will draw current from the alternator and the starter battery at the same time. I stand to be corrected but the available charge current could be in the hundreds of amps.
Surely this one of the functions of the BMS to limit the charge current, mine is limited to 100A although that may be high for the alternator excess capacity if not temp regulated.
 
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I happen to be a big fan of mounting the protection fuse directly on the battery. EATON's Bussmann Series MRBF-250 Marine Rated Battery Fuses are cheap and are perfect for this application.

Here is an example: https://www.waytekwire.com/item/45565/250A-Bussmann-MRBF-58V-Marine/

Best practice calls for mounting the fuse or circuit breaker as close as possible to the source (battery in this case). The reason for this is that any wire between the source and the fuse is unprotected should it chafe through or otherwise become shorted to ground.
 

AirJoseph

Member
Surely this one of the functions of the BMS to limit the charge current, mine is limited to 100A although that may be high for the alternator excess capacity if not temp regulated.
The BMS limits the charge current to 100 amps? Is that done by opening the circuit if it hits 100 amps or does it regulate the current to 100 amps?
 

Kevin.Hutch

2011 Mercedes 313 906
The manufacturer did not disclose the internal workings of their BMS and I have no way of checking, but I have to assume that it does not just disconnect as the input and output are via the same battery terminals and disconnecting the battery would transfer any load to just running on the alternator.
 

borabora

Member
[
The BMS limits the charge current to 100 amps? Is that done by opening the circuit if it hits 100 amps or does it regulate the current to 100 amps?
The battery BMS cant't limit charge current. It will just disconnect the battery and reconnect after a while.
However, the Sprinter alternators that I am aware of will reduce voltage soon after start up to somewhere around the float voltage of the starter battery (~13.7V) which will reduce the LIFEPO4 charge current significantly. It will also leave such batteries undercharged depending on one's type of driving.
Personally, I think DC-DC charge controllers are a no-brainer for LIFEPO4 batteries.
 

marklg

Well-known member
My Lifeblues definitely disconnect when the voltage gets to high or too low and also when the batteries decide they are fully charged. With no load, the solar charge controller and the Sterling B-B could not shut off fast enough and the voltage exceeded 16V for a very short time when the last battery disconnected. Now, if I am charging with either of those sources, I have a small load (inverter running the microwave display) and the problem has not happened again.

Regards,

Mark
 

Kevin.Hutch

2011 Mercedes 313 906
Mark that surely makes no sense, if the BMS disconnects the battery even that is a crude way of regulating or the PWM approach the question is what an individual BMS hysteresis (off/on pulse width) or how long, milliseconds, seconds or until the surface charge drops to a predetermined level and how will loads cope with that.

Disconnecting the battery from charge must also disconnect the load as the charge and load are via a common terminal, switching off the solar regulator and any load connected.

Hypothetically if I am in a Van park on a shore charger with only one small LED reading light on and the battery reaches fully charged would the light go out or am I at the mercy of an unloaded charger.
 

marklg

Well-known member
Mark that surely makes no sense, if the BMS disconnects the battery even that is a crude way of regulating or the PWM approach the question is what an individual BMS hysteresis (off/on pulse width) or how long, milliseconds, seconds or until the surface charge drops to a predetermined level and how will loads cope with that.

Disconnecting the battery from charge must also disconnect the load as the charge and load are via a common terminal, switching off the solar regulator and any load connected.

Hypothetically if I am in a Van park on a shore charger with only one small LED reading light on and the battery reaches fully charged would the light go out or am I at the mercy of an unloaded charger.
The BMS is internal to the battery. When it decides it is charged enough it disconnected. The load is still connected to the solar charge controller and the B-B. They were not fast enough to avoid a very short high voltage spike (milliseconds) when the battery disconnected. The battery also registered an overvoltage input. The BMS may stay disconnected for some time in that case. It could be that the voltage setting on the solar charge controller is too high, it has limited choices, but I am sure that with a small load applied, everything works correctly. It may be just a transient interaction between the BMS and the charging sources, but it happened several times until I left a load connected when charging.

Regards,

Mark
 

Kevin.Hutch

2011 Mercedes 313 906
The BMS is internal to the battery. When it decides it is charged enough it disconnected. The load is still connected to the solar charge controller and the B-B. They were not fast enough to avoid a very short high voltage spike (milliseconds) when the battery disconnected. The battery also registered an overvoltage input. The BMS may stay disconnected for some time in that case. It could be that the voltage setting on the solar charge controller is too high, it has limited choices, but I am sure that with a small load applied, everything works correctly. It may be just a transient interaction between the BMS and the charging sources, but it happened several times until I left a load connected when charging.

Regards,

Mark
My battery has only two terminals pos and neg and they are connected to all active charge sources and loads.

If the battery was to disconnect internally by the BMS when there is only one charge source, as when I am on shore power at night, the external terminal would only have power from the charge source and chargers usually rely on the battery to provide stability and if the source is too high for the BMS it would likely be too high for many loads. I have burnt out cheaper 12v LEDs with the 14.8V from the Sprinter alternator.
 

marklg

Well-known member
My battery has only two terminals pos and neg and they are connected to all active charge sources and loads.

If the battery was to disconnect internally by the BMS when there is only one charge source, as when I am on shore power at night, the external terminal would only have power from the charge source and chargers usually rely on the battery to provide stability and if the source is too high for the BMS it would likely be too high for many loads. I have burnt out cheaper 12v LEDs with the 14.8V from the Sprinter alternator.
Yes, that is exactly what happened. The load of the inverter is enough for the charging source to still regulate, even when the battery disconnects, so no harm, and the battery connects again in a few seconds. With no load, the charging source does not regulate fast enough, the voltage spikes, and the battery detects an overvoltage at 15.2V +/- 0.2V and will not connect again until the voltage goes below 14.4 V +/- 0.2V. The Sterling BB1260 LiFePO4 setting max voltage is 14.4V with some tolerance.

So, basically, the battery is almost charged, approaching 14.4V and the Sterling BB1260 is happy there. The BMS opens up, maybe for a very short time and the voltage spikes to above 15.6V for a very short time. Then, the overvoltage protection on the battery triggers. The Sterling eventually regulates back down to 14.4V but that is not low enough for the battery overvoltage protection to allow it to reconnect if the tolerance is just slightly negative.

I have seen suggestions to set the Sterling up with a custom setting so the max voltage is a little less. It is hard to do using the panel buttons.

Having any load at all keeps the max voltage from never going above 15.2V so the overvoltage protection never kicks in and the BMS, which probably does use a PWM circuit, just tops off and balances the battery, turning off and on as needed.

Regards,

Mark
 

Kevin.Hutch

2011 Mercedes 313 906
Now it all makes sense, that must be why my battery manufacturer recommended I set my solar regulator down to 14.4v I am now intrigued how I have seen prolonged 14.8v when the alternator is running, thus the DVSR on connecting the batteries. I have had the fridge on (only load) and sun out (solar charge present) when the alternator has shown 14.8v, although as a load the fridge switches on/off with it's thermostat so I will have to check the current into the battery next time I see it.

It may simply be that the voltage drop over the cable between the chassis and House battery has kept the voltage at the battery below 14.4v. The 14.8v I see is from on my OBII monitor showing the chassis battery voltage, constantly monitored since I burnt out the original solar regulator with over voltage and my BMV700 screen is not visible from the drivers seat.
 

marklg

Well-known member
Now it all makes sense, that must be why my battery manufacturer recommended I set my solar regulator down to 14.4v I am now intrigued how I have seen prolonged 14.8v when the alternator is running, thus the DVSR on connecting the batteries. I have had the fridge on (only load) and sun out (solar charge present) when the alternator has shown 14.8v, although as a load the fridge switches on/off with it's thermostat so I will have to check the current into the battery next time I see it.

It may simply be that the voltage drop over the cable between the chassis and House battery has kept the voltage at the battery below 14.4v. The 14.8v I see is from on my OBII monitor showing the chassis battery voltage, constantly monitored since I burnt out the original solar regulator with over voltage and my BMV700 screen is not visible from the drivers seat.
If your battery overvoltage cutoff is similar, 14.8 V won't be enough to trip it. I'll bet there are at least a few tenths of a volt drop in the wiring. The fridge will still take some current even if the compressor is off, so that may be enough to keep things below whatever the overvoltage cut in is. If it doesn't ever trip, it doesn't have to drop below 14.4 to come back on.

Regards,

Mark
 

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