LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[FlyingCloud1937]

Originally Posted by ebaugh

At the time I first saw this, I was only interested in defeating the logic since the values were not adjustable or useful for me. With the help of Magnum support (very good!), we determined I needed both the newest remote controller (even though it looks identical) AND a firmware upgrade on the board in my inverter charger.

Sounds like now it will let me not only adjust, but defeat the logic. I seem to remember the tech saying the voltage levels for Battery Saver were hard coded, unlike the other customizable values. Maybe they have fixed that in the last 9 months or so.

Battery Saver is just a time function of the float mode, so voltages set for float are what are used.

Lloyd

[ebaugh]

Originally Posted by FlyingCloud1937

Battery Saver is just a time function of the float mode, so voltages set for float are what are used.

Lloyd

Not exactly. My system was new in 2011, just slightly over 2 years ago. I have "float" set to 13.2 at the moment. It's logic, which I can't exactly define at the moment, holds the 13.2 for a period of time, it will eventually turn "off" the charger until the voltage gets to somewhere around 12.7 or 12 8, then reactivates "float" and repeats the cycle after re reaching 13.2 V. Over and over. The 12.7 or 12.8 is not, and was 6 months ago not a setable parameter under any situation as I remember. But you could defeat "battery saver" with the latest firmware and controller.

For AGM, LA and Gel this behavior makes sense. At dock, there is no reason to float forever if there is no load. But if there is a load, 12.8 is more or less a resting full charge voltage and would almost immediately fall to that value under a load and reactivate the "float" level. With LFP, you will churn through 75% of your charge before it charges again.

It's really worse than that. Every time I start my genset, my more cooperative inverter charger always starts in bulk mode. The Magnum starts in "float" mode since the voltage is already high. So no charge current by default. While I could raise the "float" number, that becomes a permanent floor voltage I don't want. So I have the equalize value set pretty low, about 14V and just invoke equalize every time. Equalize will at least both 1) Timeout if I forget or 2) reset itself to float for the next charge cycle when I kill the generator. Yet again, only the latest firmware can force a "bulk" cycle. Drats. We almost always kill the genset before the cells see more than 3.4-3.45V, so it's not a huge problem. At dock, I just turn off the Magnum charger and float on the other one.

[roetter]

Originally Posted by rainmaking

How did the shipping go? I am looking at the 700Ah ones for two boats. I need them to go to Florida.

Roetter,
I am in SFL and am ordering 12x 700Ah SP's. This thread is great but hard to weed through a lot of the crap people want to stir up. I am tuned in to all the issues here, and even have some new ones (like non-adjustable outboard motor alternators). I really appreciate ebaugh's recent posts related to real and relevant experience 'float' charging at 3.35V.[/QUOTE]

Hi Rainmaking

12 700 Ah cells. That's a lot. What are you building?

When do you need your cells. I need my 700 Ah cells for fall to fit out my boat and a friends boat.

[roetter]

Do you think the alternator (diodes) will survive if you disconnect the house bank at high voltage, but still have the starter battery connected?

[deckofficer]

Originally Posted by roetter

Roetter,
I am in SFL and am ordering 12x 700Ah SP's. This thread is great but hard to weed through a lot of the crap people want to stir up. I am tuned in to all the issues here, and even have some new ones (like non-adjustable outboard motor alternators). I really appreciate ebaugh's recent posts related to real and relevant experience 'float' charging at 3.35V.

Hi Rainmaking

12 700 Ah cells. That's a lot. What are you building?

When do you need your cells. I need my 700 Ah cells for fall to fit out my boat and a friends boat.[/QUOTE]

Which boat is getting the (8) cells? That is a stout house bank. Going for an all electric galley?

[ebaugh]

Originally Posted by roetter

Do you think the alternator (diodes) will survive if you disconnect the house bank at high voltage, but still have the starter battery connected?

That should work fine. It's essentially what I do. Must be connected in parallel with house bank, at least anytime an engine is running.

[rainmaking]

I am not planning a separate starting battery, just two active (one off each engine) and one 'reserve' banks. I was hoping the alternator voltage would not be high enough to cause overcharge but after some posts here I may need to rethink that. Since the alternators only put out 40A we can probably prevent overcharge with load, but it would be unusual for us to have that situation anyway as the 40A on each bank will seldom be much more than maintaining normal load.

We are ordering them this week.

[rainmaking]

Deckofficer,
34' custom Carolina style fishing boat. Galley has sharp super steam convection microwave combo but there will be a propane grill at the bait station...as soon as I either find or build the right one. Fridge, freezer, two AC units....no generator. Well, we might have a eu-2000 for emergency back up.

[roetter]

The voltage the alternator creates at the LA terminals when the amps have dropped from 60 at start of charge to less then 20 amps is 13.4V. That should be low enough to not cause any over charge on 700Ah cells even if we motor for 24+ hours.

What do you think.

[ebaugh]

Originally Posted by rainmaking

I am not planning a separate starting battery, just two active (one off each engine) and one 'reserve' banks. I was hoping the alternator voltage would not be high enough to cause overcharge but after some posts here I may need to rethink that. Since the alternators only put out 40A we can probably prevent overcharge with load, but it would be unusual for us to have that situation anyway as the 40A on each bank will seldom be much more than maintaining normal load.

We are ordering them this week.

You must either have smart alternator controllers, or wire it so the max voltage measured at the battery stays where you want it. There are a couple ways to do this. A battery isolator will drop about 1/2 volt. You can also vary the size and length of the cable feed to the battery, but stay within ABYC ampacity requirements. The longer and smaller the wire, the more the voltage drop.

When I purchased my boat it still had the 1985 factory rig. The output of each alternator went EngineRoom-LowerSteering-FlybridgeSteering-Battery...with 10 ga wire. They did this to power the chg/dsc ampmeters installed in the instrumentation from a different era. But the stock 70A alternators were constrained to about 15-20A and a max voltage of about 13V due to the wiring.

You will have to tinker to find the right combination. Start with a full charged bank, disconnect the shore charger, fire up the engines to 1200 RPMs or so and watch the battery voltage. When it settles where you want it to, you can stop tinkering.

The only other caution is alternator temperature, but with 40A alternators this probably won't be a big factor. You can test this by starting the engines with a discharged bank and watching case temps with an IR gun. Do this after you get done with tinkering with the wire size and isolator if needed.

You probably will only get 20-25A max charge per alternator this way, but if you aren't using the main engines to recharge at anchor, this all makes sense for a power boat.

If you anticipate 24 hour fishing trips, the isolator is a more bulletproof solution. The wiring solution can eventually cause enough trickle charge to potentially creep up the voltage. But for an 8 hour fishing trip, you are probably OK with the ON-OFF-SLOW nature of the operation. Or if there is sufficient normal house loads of electronics lights refrigeration, this will also suck up the power, potentially eliminating the creep.

Welcome to the world of LFP.

[rainmaking]

I think that 20A is going somewhere. Either load is consuming it, terminals are plating, or electrolyte is heating. I would assume over plating is hardest on the battery. Presumably, if you are not at the plating voltage, this is not what is happening. I am not knowledgeable enough to know. Ebaugh's insight a page or two back is helpful though. I am interested to know what his load during the trip was. Remember, even the ignition system on the engine is pulling a fair amount of juice, and boats have lots of 'stuff' that consumes power.

[rainmaking]

Ebaugh, great idea about 'tuning' the alternator voltage. As for temperature, these are big V8 outboards and the alternators are built in to the flywheels. There's not really a good way to determine their heat sinking capacity.

We will be set up just as much for cruising as fishing. Thinking: summer, alternating nights on anchor with ones at marinas. Winter hopefully we can get two or more nights on anchor. The engines, even on long runs, won't be very useful in charging the banks.

[ebaugh]

Originally Posted by rainmaking

I think that 20A is going somewhere. Either load is consuming it, terminals are plating, or electrolyte is heating. I would assume over plating is hardest on the battery. Presumably, if you are not at the plating voltage, this is not what is happening. I am not knowledgeable enough to know. Ebaugh's insight a page or two back is helpful though. I am interested to know what his load during the trip was. Remember, even the ignition system on the engine is pulling a fair amount of juice, and boats have lots of 'stuff' that consumes power.

No ignition system on a diesel. But our average load underway is about 25-30 amps, mostly refrigeration powered by the inverter. At the end of the trip we still showed about 10A charge into the Li bank, which does puzzle me a bit. But I did not watch it like a hawk. It does show discharge of maybe 50A or so when we run the microwave underway. The voltage regulation on the alternators is not tight. So you don't ever really get zero current flow.

[deckofficer]

Originally Posted by rainmaking

Deckofficer,
34' custom Carolina style fishing boat. Galley has sharp super steam convection microwave combo but there will be a propane grill at the bait station...as soon as I either find or build the right one. Fridge, freezer, two AC units....no generator. Well, we might have a eu-2000 for emergency back up.

That sounds good. How much solar production? I just switched to an electric BBQ and like it a lot.

[roetter]

I want to run my design by you guys and see what you think.

4x 700 Ah cells
2 Junsi cell logs
one set for HLV cell and pack level, also delta-V, connected to solenoid cutting off all loads
The other set for LVH cell and pack level, also delta-V, connected to solenoid cutting off all chargers, Lithium house bank has starter batts in parallel all the time through
The solenoids will be driven by the Junsi via a car-style SPDS relays

Chargers:
2 x stock alternators on 2 Yanmar 54 HP engines with internal rugulators. 13.2 V on terminals at LA batteries during absorption with Cristec RCE electronic battery isolator
Victron Quattro 12V 5000 200 A charger
2 x Outback Flexmax 60, each with 900W solar