Design of AGM & LiFePO4 / Solar system for my boat

[tpenfield]

Quick Update . . .

The system is pretty much all set and has been running for a week or so. I have updated my 'Key Components' diagram (without all the detailed business of the schematic diagram) for those interested in doing something similar (at your own peril ).
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One glitch-y thing that I have found so far is that while using both the Solar and Shore Power to charge the house bank (LiFePO4), I occasionally get an over voltage fault (warning) on the Xantrex . . . typically in the 16.5 - 17 volt range. Although in theory, these charging systems are supposed to play nicely together, I am finding that for brief moments they do not. I believe as the solar panel input to the DuoRacer fluctuates due to clouds passing by, etc., the output of the DuoRacer for a split second or 2 goes over its prescribed voltage range. I noticed the same situation in my earlier stages of testing the solar and the DC-DC charger running together. (thus the lock-out relay)

I don't think the Li-Time batteries mind the split second over-voltage as they don't go off line, but the Xantrex Inverter is quick to notice it. Anyway, not a huge issue at this point, because I can be mindful to use the Xantrex (i.e. shore power) for charging the house bank only when the solar is off-line. If I get really bored some day, I could even put a manual switch in for the solar charging.

 

[tpenfield]

The solar charging system has been working well, but I've been struggling with some engine electrical power related issues for a couple of weeks.

The issues that took a while to sort out. . . .

1) The starboard engine alternator crapped out. I think it was on its way out last season, and during spring prep it said its good-bye. The replacement alternator was defective, so I had to send it back for a refund and got a different brand of alternator (Arco Marine). The alternator is a Delco 7SI style for those following along.



Anyway, while I was sorting that out, it appeared that the starboard engine was getting voltage from the port engine. These digitally controlled engines are supposed to be 'electrically' separate, so it was important to resolve the issue. The symptoms were noticed when I switched the starboard battery off . . . the main power relay on the engine would start buzzing. Initially I thought it was an issue with the starboard engine, but then realized if I disconnected the port engine's battery the buzzing stopped.

Long story made short . . .

2) The battery isolator (2 alternator/3 battery) proved to be the culprit (perhaps internally shorted or something), so I replaced the isolator with a '2 alternator / 2 battery' style ,since I no longer needed a third bank on the isolator. (problem solved) Having the isolator will allow both alternators to share the load of charging the LiFePO battery bank, as needed. FWIW - the DC-DC charger for the LiFePO bank is connected to the port battery, similar to how the original AGM bank for the inverter was connected.


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As you can see, the electrical box (starboard side) needs some TLC . . . Planned for the end of the season. I realized the the electrical box was getting water in it (rain water). So I added some drainage while I get the source of the water figured out.

Boat launch is planned for next week, and I will see how the 'new' electrical system works in its intended real-life setting. I usually use the boat 1-2 times a week, so the solar aspect is primarily used to maintain the batteries while the boat is not is use.

Speaking of solar . . . I have a '100 watt' Renogy semi-flexible panel installed on the soft-top of the boat. It is on its third year of use. The best I've seen it do is 65 watts in mid-day full sun, which is fine for battery maintenance. The MPPT controller (EPEver DuoRacer) 'squeezes' a bit more power out of the panel than the PWM controller (Renogy Voyager) that I was using when I had AGM batteries, but not dramatically so. . . . maybe 10% more power. Something to keep in mind if I plan on expanding the solar capabilities in the future.

 

[svsagres]

For me, the critical issue might be the risk of unexpected shutdown.

There really is no way to know when a BMS is likely to just turn off.

Sure there is. My BMS throws all sorts of warnings and alarms, long before it will do a safety disconnect.

• Temperature out of range? It commands the charge sources to 0A (happened to me this winter).
• Cells too far out of balance? Limit charge current to 1.5A while the balance does its thing.
• High voltage? Before it hits the HVD emergency voltage, it tails off the charging sources so we don’t overshoot. If it does alarm, it disconnects the charging sources after giving warning, but leaves the load connected to draw the battery down.
• Undervolt? Shutdown the DC load, but leave the charging sources Connected so they can bring the battery up. But long, long before it gets anywhere close to this point, there will have been alarms, email notifications, audible alarms, etc telling me the battery is about to be disconnected.

The BMS knows everything that’s going on with the battery, and communicates it with the rest of my system. I can be sitting at the bar in a hotel on the other side of the planet from my boat, and know precisely what my battery is doing.

 

[HarryN]

Thanks for the insights in the thread. I didn't think about the idea that the alternators would behave odd if the two are connected via the starter batteries while in use, but it makes sense.

 

[pollenface]

Why did you decide to stop solar charging when the engines are running?

In my case alternator output voltage is higher than Victron float voltage so naturally zero current is drawn from the solar panel while motor is running.

 

[grizzzman]

In my case alternator output voltage is higher than Victron float voltage so naturally zero current is drawn from the solar panel while motor is running.

Thanks for the update.

 

[pollenface]

Thanks for the update.

Anytime

 

[tpenfield]

Quick Update . . .

The system on my boat seems to be working well. My 100 watt capacity solar panel generates between 60 - 75 watts of power in full sun. which results in 16-18 volts from the panel into the EPEver DuoRacer, depending on load.

Once in a while my Xantrex 2012 inverter detects an over-voltage, which I believe is some quirkiness in the DuoRacer when sun conditions change . . . but who knows.

When the alternators are running, and at a reasonable RPM, I'm getting about 14.7 volts into the Victron Orion charger, and 13.5 volts output, which allows for some decent bulk charging.

I have not run the LiFePO4 batteries down that much, nor have I been on shore power, which will charge the LiFePO4 from the Xantrex. The biggest load I have put on the LiFePO4 bank is 40 amps into the Xantrex to yield about 4-5 amps of 120 VAC. I ran the boat's air conditioner for a while and have used a corded wet/dry vacuum.

I did notice that when the air conditioning was running the voltage from the LiFePO4 bank went down to 12.7 volts, which triggered a low voltage warning. The current draw at that point was about 20 amps per battery (2 batts in parallel), which I did not consider to be all that much. I am wondering if that is an issue with the Li-Time batteries, or perhaps I need a third battery in parallel.

The wet/dry vacuum (when used separately) was drawing similar amperage, but did not set off a low voltage warning. Not a huge issue for me, as I may only be using Air Conditioning when on shore power.

 

[tpenfield]

I did notice that when the air conditioning was running the voltage from the LiFePO4 bank went down to 12.7 volts, which triggered a low voltage warning. The current draw at that point was about 20 amps per battery (2 batts in parallel), which I did not consider to be all that much. I am wondering if that is an issue with the Li-Time batteries, or perhaps I need a third battery in parallel.

The wet/dry vacuum (when used separately) was drawing similar amperage, but did not set off a low voltage warning. Not a huge issue for me, as I may only be using Air Conditioning when on shore power.

After doing some searching on this forum, I'm thinking that I should check the voltage at various points along the wiring path from the batteries to the inverter to see if/where there may be a bad connection.

 

[tpenfield]

Quick Update . . .

I checked the voltage drop while running about 40 amps into the inverter . . . it seems like it is about 0.2 volts from the battery to the inverter. Of course I was not able to reach the power stud on the inverter to check with my multi-meter, so it could be off a bit.

Another issue to be concerned with for any one doing this on a late-model boat with digital controls is the input voltage to the DC-DC charger. I was waiting in line for a dock space to open up, so the engines were idling for a few minutes. All of a sudden, the starboard engine starting throwing fits, revving up/down and an alarm went off. The engine finally died.

It turned out that I had the charging settings too low on the Victron Orion DC-DC charger and it was trying to do bulk charging of the LiFePO4 batteries while the engines were idling . . . not enough power coming from the alternators, so the voltage went too low for the digital controls and the engine went crazy.

I changed the setting so that the DC-DC charger operates only when the input voltage is in the 14 volt range, which is when the engines are running at a decent RPM. It seems to work better now.

 

[MakeMePower]

Quick Update . . .

I checked the voltage drop while running about 40 amps into the inverter . . . it seems like it is about 0.2 volts from the battery to the inverter. Of course I was not able to reach the power stud on the inverter to check with my multi-meter, so it could be off a bit.

Another issue to be concerned with for any one doing this on a late-model boat with digital controls is the input voltage to the DC-DC charger. I was waiting in line for a dock space to open up, so the engines were idling for a few minutes. All of a sudden, the starboard engine starting throwing fits, revving up/down and an alarm went off. The engine finally died.

It turned out that I had the charging settings too low on the Victron Orion DC-DC charger and it was trying to do bulk charging of the LiFePO4 batteries while the engines were idling . . . not enough power coming from the alternators, so the voltage went too low for the digital controls and the engine went crazy.

I changed the setting so that the DC-DC charger operates only when the input voltage is in the 14 volt range, which is when the engines are running at a decent RPM. It seems to work better now.

enjoyed your updates, is there a reason you stuck with isolators vs ACR relays? isolators in rv's always had decent voltage drop due to them being diode based. I feel like all your works around could have been avoided using acr or voltage sensitive relays.

you mentioned a 12.7 low voltage alarm? where was that? on the inverter? 12.7 is full charge on agm, i wouldn't expect an alarm at 12.7

 

[tpenfield]

I could have used ACRs, but the boat had diode-based isolators originally, so I did not change that aspect of the design. The low voltage alarm is within the engine control system, which is completely separate from battery charging system. The charging system is fine . . .

Since the engine throttle, shifting, and steering is all electrically actuated (rather than cables . . . i.e. drive by wire) the engine control system wants to see a certain amount of voltage or else it sounds a warning/alarm on the engine display. For some reason that I have yet to find, my boat is particularly sensitive to voltage, because there is a pesky 1.1 volt loss somewhere in the engine control system. Others with the same engines experience only about 0.5 voltage loss through the system.

Anyway, when the engines are at idling speeds (600 rpm) there is not enough power coming from the alternators to support 30 amps of bulk charging to the LFP battery bank. So the resulting voltage to the engine control system dips slightly below its warning threshold, causing the alarm. A friend of mine with the same boat and a similar system, just put a manual switch it the circuitry to the DC-DC charger so he can only charge his LFP battery when going at cruising speeds (3000+ RPM). I wanted to take a more automated approach, and it needed some tweaking. I was also considering that maybe I don't need 30 amps of bulk stage charging . . . perhaps 15-20 amps will do.

 

[MakeMePower]

I wanted to take a more automated approach, and it needed some tweaking. I was also considering that maybe I don't need 30 amps of bulk stage charging . . . perhaps 15-20 amps will do.

sounds like a perfect place for an acr relay, should drop the bank at idle, then after cruising for 2 minutes fire back up

 

[tpenfield]

sounds like a perfect place for an acr relay, should drop the bank at idle, then after cruising for 2 minutes fire back up

Well, the system is done so something to consider for the next time around.

 

[sammaw]

cool project i am looking at doing something fairly similar. Keep the lead acids for the engine and use a DC-Dc charge for the Li. i probably wont do solar for a start. I have a space similar to you in my boat for the kit, but i was told and read i shouldnt install in the same compartment as the engine. I already have a genset in there and and some battery chargers and batterys. It would simplify my build greatly if i can do what you did in the engine bay. Is the invertor in there as well? How long cant you run your aircon if you had too?

 

[tpenfield]

@sammaw . . . . Maybe sample the engine room temperature during normal operating conditions. I run the bilge blowers continuously when the engines are running, so that helps keep the temperature down. I have not had any problems regarding heat.

The inverter is in a utility bay, which is more forward in the boat under the helm station.

The Air conditioner draws about 40 amps from the LFP bank, which has 2 x 100 Ah 12.8volt batteries. It will run the A/C for 3-4 hours. I don't really use it unless connected to shore power.

Solar charging is a nice thing to have if your boat resides away from a power source. If I had to change anything, it would be to have 200 watts of solar, since the controller manages how much gets used for the charging/maintaining the batteries. A 100 watts panel is OK for maintenance, but a little extra would be nice at times.

 

[Deadboatbattery]

Hi
Have you thought about updating your present altenators?
You will need to have some brackets built to convert them over to your motor.
Gm 1 wire works pretty good and jeggs make a low rpm cut in version as well.

JEGS Premium GM Kool-Fin 140-Amp 1-Wire Alternator - JEGS

Don't get stuck with a dead battery due to the alternator overheating! Even on the hottest day, the JEGS Alternators stay cool, due to the unique Kool-Fin case design. This high output 140 AMP alternator includes heavy duty wound copper coils, spike resistant diodes, built in regulator, double...

www.jegs.com

Mega Amp GM High Output Alternator

We have developed a high output alternator in a case that is smaller than the early GM 10SI case. The mounting on this alternator is exactly the same as the Delco 10SI, 12SI, and CS-130 cases or we have a 1 pivot ear that is common to AMC and marine use. It has the following benefits...

www.qualitypowerauto.com

 

[tpenfield]

Hi
Have you thought about updating your present alternators?

No . . .

 

[sammaw]

sorry just one more question, do you run your 12v accessories of the lithium or lead? ie radar, chart plotter, lights etc.

 

[tpenfield]

sorry just one more question, do you run your 12v accessories of the lithium or lead? ie radar, chart plotter, lights etc.

Lithium . . .

Essentially everything that was powered from the accessory bank before the conversion remained so. The change was that the accessory bank was now lithium instead of AGM.

 

[RDLG44]

Hi, new member here. Thanks for all the great info! We are in the process of buying a twin diesel cruiser and if the deal goes through, I know I will need to redesign the existing battery system to support our "unplugged" cruising plans. Something along the lines of what tpenfield has done, with the addition of a 5kw genset.
A question off the top is whether it is possible to add LiFePO4 battery capacity at a later date (within reason) if I find we need more ah. I know with lead/acid batteries, its not advised to add a new battery to a bank that has multiple cycles on it as the old batteries will draw down the new one. But with lithium's minimal degradation with age, I'm hoping I can add additional capacity at a later date if required. At this point I'm estimating we'll want about 120ah/day for up to 3 days without charging. So a Li house bank of 400 - 500 ah should be sufficient. But if not, can I add another 100ah later? I'm guessing that having multiples of paralleled 100ah batteries would provide most flexibility or can I start with 2 x 200ah batteries (or a single 400ah) and add a 100ah later?
All advice appreciated!

 

[jdege]

Clark, of Emily&Clark's Adventure YouTube channel, has developed a Battery Bank Manager, designed to integrate lead acid and LiFePO4. Basically, it monitors the LiFePO4 bank, and will connect it and disconnect it at the appropriate times so as to keep the LiFePO4 healthy.

In this video he mentions that has three separate banks of lithium connected to his lead.

Emily & Clark's Adventure - BankManager™

NOW AVAILABLE BankManager™ System Combine Lithium (LiFePO4) and Lead-Acid Batteries in the same system, and charge everything optimally. Introducing the BankManager.

www.emilyandclarksadventure.com

 

[wholybee]

Clark, of Emily&Clark's Adventure YouTube channel, has developed a Battery Bank Manager, designed to integrate lead acid and LiFePO4. Basically, it monitors the LiFePO4 bank, and will connect it and disconnect it at the appropriate times so as to keep the LiFePO4 healthy.

In this video he mentions that has three separate banks of lithium connected to his lead.

Emily & Clark's Adventure - BankManager™

NOW AVAILABLE BankManager™ System Combine Lithium (LiFePO4) and Lead-Acid Batteries in the same system, and charge everything optimally. Introducing the BankManager.

www.emilyandclarksadventure.com

This has been posted several times before and has gone around the Internet for a couple years. It works, and has a lot of advocates.

However....... The system is not allowed by either ABYC in the US, or ISO in Europe because connecting LFP and Lead Acid together that way is explicitly prohibited.

I always come to the same answer/conclusion. Why? LFP is pretty darn simple. It is safer and works better than Lead. And that system doesn't solve any problems. It works, but so does a system that doesn't connect an LFP and lead-acid battery. And his claim that it charges optimally and otherwise you wouldn't be is dubious. LFP batteries charged by voltage that were installed on boats 15 years ago and have thousands of cycles still perform almost as new. So.... Why mess with that? And he has several versions of his system. Why? Did the first versions not perform well?

@RDLG44
Yes, with Lithium is is fine to ass more capacity later, for exactly the reason you say. I would advise to start with as large of a battery as possible instead of multiple 100Ah. That way when you add later you will have as few batteries as possible. Strange things can happen after you have 4 batteries in parallel. The parallel batteries need not all be the same capacity.

 

[jdege]

He methods of charging might be better, but are the standard methods good enough? Probably.

I can see two advantages of using his BBMS:

1. Lead is more tolerant of abuse. It's not going to just take itself offline, because... Having lead to run your chart plotter, navigation lights, bilge pumps, when everything goes wrong, might be a good idea.
2. It allows running multiple banks of LiFePO4 with different ages/origins/charging characteristics, instead of having to replace everything everyone you upgrade.

 

[wholybee]

He methods of charging might be better, but are the standard methods good enough? Probably.

I can see two advantages of using his BBMS:

1. Lead is more tolerant of abuse. It's not going to just take itself offline, because... Having lead to run your chart plotter, navigation lights, bilge pumps, when everything goes wrong, might be a good idea.
2. It allows running multiple banks of LiFePO4 with different ages/origins/charging characteristics, instead of having to replace everything everyone you upgrade.

LFP is much more tolerant of abuse than Lead-Acid. It is a plague of lead-acid that banks die after only 1 or 2 years, sometimes less than a year, because of incorrect charging. AGM is especially bad because AGM *requires* a higher charge current than FLA, and also needs to be fully charged at least once per week, preferably more often. Hordes of carbon foam lead batteries are now moving to LFP because that technology didn't work out and many banks dies after a few years. The best thing Clark's system has going for it is that it protects the Lead-Acid from early failure. But it doesn't do a damn thing to make LFP any better.

That simply doesn't happen with LFP. Pretty much the only thing that will damage LFP is overcharging it, or draining it below 0%. Those are what the BMS protects from, and if you setup your charger correctly, the BMS will never disconnect. There are installations that don't even use a BMS (not recommended), even installations that date back 15 years. The fear of a BMS disconnecting is really an irrational one. You can use a Victron BMV with alarms to warn against it if you are really worried. Just setup your chargers correctly to not overcharge them.

And, you can mix LFP batteries of different ages/origins/capacities and they all have the same charge characteristics. The charge characteristics are part of the chemistry. You will see different makes give different specs mostly because LFP is very tolerant and doesn't care. There are lots of opinions on what is "best" but in the end it doesn't matter much. Just don't over charge them.

Given that LFP is now cheaper than Lead, it is simply nonsense to not go all the way and dump lead.