R-31 Power Distribution Questions

[FlyMeAway]

Factory help please!

The R-31 battery power distribution schematic doesn't show the alternator or the solar panels.

How is the alternator in our boats wired? Directly to the engine battery?

Do the ACRs mean that the alternator is charging all battery banks in parallel, or does it charge the engine battery to a certain point before kicking in for the house/thruster batteries?

Is the alternator programmable in terms of charging voltage? What model alternator do our boats have (if there is a stock D4-300 Volvo alternator, I was unable to find information about this in the engine manual or online).

According to the manual the solar charger splits 90/10 house/engine. How is that 90/10 split achieved (is the solar charger wired directly to the batteries and achieves the split on its own)?

 

[SJI Sailor]

Same question!

I was recently trying to figure out whether there is any dependency between the alternator and the settings on the C30 AC charger panel. For example, if the AC charger and inverter are both off, will the alternator still charge the batteries? (I would certainly assume so! but could not find anything in the manual.) And which ones does it charge?

 

[Wee Venture]

If your setup is like mine (R-31CB model year 2018 built in 2017), the alternator is a “Volvo Penta model 3840181” which I believe is built by Mitsubishi. 115 amp. It has a direct connection back to the engine battery (through the battery switch). The alternator is independent from any settings on your inverter/charger or your solar panel controller. You have ACRs between the engine battery and both the thruster bank and the house bank, so once the engine battery gets to 13.0V for two minutes, the ACRs close and apply charging voltage to both other banks. This almost always happens very quickly. The settings on your inverter/charger only apply to that unit, which has a direct cable connection to the house bank (through a fuse and switch in the port lazarette). The Morningstar controller sends an isolated 10% of the charge current directly to the engine battery and 90% directly to the house bank. That can be misleading though, since when either gets to 13V, the ACRs close and connect them all in parallel. I ended up replacing my Morningstar controller with a Victron MPPT unit that has only one output but that is another story.

John

 

[FlyMeAway]

If your setup is like mine (R-31CB model year 2018 built in 2017), the alternator is a “Volvo Penta model 3840181” which I believe is built by Mitsubishi. 115 amp. It has a direct connection back to the engine battery (through the battery switch). The alternator is independent from any settings on your inverter/charger or your solar panel controller. You have ACRs between the engine battery and both the thruster bank and the house bank, so once the engine battery gets to 13.0V for two minutes, the ACRs close and apply charging voltage to both other banks. This almost always happens very quickly. The settings on your inverter/charger only apply to that unit, which has a direct cable connection to the house bank (through a fuse and switch in the port lazarette). The Morningstar controller sends an isolated 10% of the charge current directly to the engine battery and 90% directly to the house bank. That is fairly meaningless though, since when either gets to 13V, the ACRs close and connect them all in parallel. I ended up replacing my Morningstar controller with a Victron MPPT unit that has only one output but that is another story.

Ok cool this is very helpful (and ours is also an R-31CB built in 2017 / MY 2018, so sister ships!).

Follow-up questions:

Is the stock alternator at all programmable for voltages (bulk/float) or what are its default settings?

Do the ACRs work bidirectionally or are there multiple ACRs? This is the confusing point to me. The diagram has the charger/inverter positive terminal going to the house positives, from the house positives to an ACR and then to the engine positives (and another ACR from engine positives to thruster positives).

Does this mean that:
1) Engine doesn't get charged by inverter until house batteries get above 13V?
2) Thruster doesn't get charged by inverter until house batteries get above 13V?

But if the engine/alternator is running, the engine battery charges first? Is there a separate ACR that makes that happen? I don't see how things could be wired that way, unless the ACRs are bidirectional?

 

[Wee Venture]

Regarding the ACRs, they are directionally blind. They are just a relay that closes like a switch when they “sense a charging voltage” on either side. Since charging voltages are usually 14V+ and the relay “switch” closes when the voltage on either side rises to 13V, it usually does not take much time for the charging voltage to be applied to both sides of the ACR. I used to have the misconception that the ACR would close only when the bank on one side reached a certain state of charge but the ACR has no way to measure this other than an arbitrary measurement of voltage.

Regarding the alternator, I know of no way to adjust its output settings but that doesn’t mean there isn’t one. I know there are add-on modules to make the alternator more “smart” but I have heard that this is sketchy on the Volvo Penta engines. Maybe someone else can weigh in here who knows more about the alternator.

John

 

[BB marine]

What you are trying to accomplish is doable with a smart regulator. I would ask a Good VOLVO SERVICE REPRESENTATIVE ! The question as to what are the best options. Volvo common rail electronic engines do not like voltage changes and need to be isolated. The big issue with using standard voltage regulated charging systems with new technology batteries is they don't retain the life expectancy like they do if charged by a smart charger. In boats it is tough to make the new technology work when you rely on the engine alternator for charging. You can put the most advanced 120 Volt charger in the boat to maintain the batteries and then when you throw the lines and cruise you throw all of that away when the alternator starts charging the batteries. I am now going back to Lead acid flooded batteries. I can get almost the same power out as the AGM. I don't have to worry about the charge rate being high enough, destroying them if the voltage goes below 50%. A standard marine charger will do the job and the 130.00 batteries need to be replaced every three years instead of the 300.00 every 5 years, I just priced out East Penn group 31 DP batteries Flooded 100AH, 700CCA, 860 MCCA $119.00 and the AGM comparison 105 AH, 800 CCA 1000MCCA $276.00. I'm paying over twice as much for the AGM to get 2 more years of service and the last two years I'm probably going to have batteries that have 80% capacity because of the way I used them. Charged with a conventional charging system (alternator)half the time.

I know this is not what you are asking and I know you know all this already but I'm just stating my opinion.

There are ways to set it all up. It is expensive and I'm not sure in the Ranger tug cruising application it is worth it.

Good luck with your project. I seems you are trying to cover every base. I hope it works out for you.

 

[FlyMeAway]

Regarding the ACRs, they are directionally blind. They are just a relay that closes like a switch when they “sense a charging voltage” on either side. Since charging voltages are usually 14V+ and the relay “switch” closes when the voltage on either side rises to 13V, it usually does not take much time for the charging voltage to be applied to both sides of the ACR. I used to have the misconception that the ACR would close only when the bank on one side reached a certain state of charge but the ACR has no way to measure this other than an arbitrary measurement of voltage.

Ok cool again this is very helpful. Follow-up question then. If the house batteries are toast and not really holding a charge, does that mean if you're idling the engine to let the batteries recharge for say an hour, you're effectively also charging 4 house batteries from the engine and thruster battery? Like will the battery banks tend to equalize while charging since they are all being charged together? How does having shot house batteries impact the alternator charging the engine and thruster, if at all?

 

[BB marine]

When the engine battery reaches 13.0 Volts for a couple of minutes the ACR close if the house bank is above 11Volts the engine and house banks are parallel the thruster bank if it is above 11 Volts it is parallel. Now all batteries are charging as one bank. When using ACR in a multi bank system all batteries charge at the same rate and if the engine battery is fully charged and linked with a battery that is at 40 % charge the batteries will sync together as long as they are parallel. The unfortunate part of this is the charge rate is not equalized thru all batteries because of the way they are wired. In order to have it charge properly the neg lead should be at one end of the battery chain and the positive lead at the other side. Example: +engine battery, thruster battery, 3 house battery bank - the positive charge lead should be at the engine battery and the negative charge lead should be at the last battery of the house bank. This will give you a equalized charge. Almost impossible to do with the way the battiest are wired in theses boats.

 

[FlyMeAway]

When the engine battery reaches 13.0 Volts for a couple of minutes the ACR close if the house bank is above 11Volts the engine and house banks are parallel the thruster bank if it is above 11 Volts it is parallel. Now all batteries are charging as one bank. When using ACR in a multi bank system all batteries charge at the same rate and if the engine battery is fully charged and linked with a battery that is at 40 % charge the batteries will sync together as long as they are parallel. The unfortunate part of this is the charge rate is not equalized thru all batteries because of the way they are wired.

Ok, so what happens if the house bank falls to 10.5V? Does the ACR close and not charge the house bank?

And if they are all charging as one bank, and the engine is idling, that means they charge *slowly*?

By "the batteries will sync together" does that mean the house at 40% will deplete the engine as they charge, until they equalize (and then charge together)?

 

[Wee Venture]

Ok, so what happens if the house bank falls to 10.5V? Does the ACR close and not charge the house bank?

And if they are all charging as one bank, and the engine is idling, that means they charge *slowly*?

By "the batteries will sync together" does that mean the house at 40% will deplete the engine as they charge, until they equalize (and then charge together)?

I’ll try answering this as I understand it. If the house bank (or any other bank) falls below 10.8V, the ACR will lock it out. This is mainly due to protection in case there is a short. You can try removing the load (e.g., turn the house battery switch off) and see if the bank recovers above 11V. If not, and if you are confident the bank is simply depleted, you will need to get the voltage up on the house bank if you want to charge it with the alternator. You can do this by using the battery combine switch while charging with the alternator or charging the bank in some other way such as a generator.

If the batteries are “all charging as one bank” then each battery will charge more slowly than if all the charging current were going to that battery alone. As an aside, I asked a Volvo tech one time about idling the engine at anchor to charge batteries if necessary and he said that would be fine but to put it in neutral and run the RPM up to 1500 (on our D4 300).

As far as the house bank depleting the engine battery, I don’t see a scenario in which this would happen, at least to any meaningful degree. The ACRs are there to prevent that sort of thing. As long as the charging voltage stays above the engine battery’s resting voltage it will not deplete. If for some reason the voltage were to drop below 12.75V the ACR would disconnect the banks again.

Brian can add or subtract here if he wishes.

John

 

[SJI Sailor]

Just chiming in with thanks to everyone here for the great information and answers!

 

[BB marine]

Well said John.