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Old 29-05-2015, 19:25   #4531
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I'm working on putting together a modest 200ah GBS bank for my small boat. I will have two 85 watt solar panels each charging through their own Genasun GV-10 controllers. The Genasun stock LiFePO4 voltage is 14.2 v.

Now being such a low fraction of C is that 14.2 ok, or should I be ordering a custom voltage of something like 13.8 or 13.9 volts? Is there going to be more resistance at that lower level of charge, and that's why those chargers come set at 14.2, or does Genasun push the the knee a bit harder than a do it yourselfer like me needs too?

Terry, Main sail, Ocean Planet,Third day, I would love to know what you guys think.
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Old 29-05-2015, 20:16   #4532
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I am very happy with my 200 aH lithium bank @ 13.8 / 13.4 with avg daily cruising load of approx 90 aH.
320 watts of solar.
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Old 31-05-2015, 01:32   #4533
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Just read a report from Powerstream Technology date Feb last yr and the testing clearly showed the difference in capacity between charging at 3.4v per cell compared to 4.2v per cell was 3% at the most and the 4.2v was deemed now to actually damage the lithium ferrous cells reducing cycle life. Funny how long it takes for things to come around and start to run in parallel between the theorists and the DIY, the more hands on experience the theorists get, the closer they align with the DIY crowd. Charging to 3.5v per cell ranged from 99% to 100% depending on the product tested, that confirms my stand on 3.6v or higher as over charging the cells and therefore damaging them if this voltage is maintained, and that is exactly what the balance board system does, holds the voltage above 3.6v till all the cells are above 3.6v. The question is, why do it? If 3.5v is between 99% and 100% fully charged, what value is charging all the cells to 3.6v? Charging them to 4.2v is just asking for a short cycle life.
Here is a link to the Powerstream Technology report Charge voltage experiments with lithium iron phosphate batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage


T1 Terry
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Old 31-05-2015, 03:52   #4534
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by T1 Terry View Post
Just read a report from Powerstream Technology date Feb last yr and the testing clearly showed the difference in capacity between charging at 3.4v per cell compared to 4.2v per cell was 3% at the most and the 4.2v was deemed now to actually damage the lithium ferrous cells reducing cycle life. Funny how long it takes for things to come around and start to run in parallel between the theorists and the DIY, the more hands on experience the theorists get, the closer they align with the DIY crowd. Charging to 3.5v per cell ranged from 99% to 100% depending on the product tested, that confirms my stand on 3.6v or higher as over charging the cells and therefore damaging them if this voltage is maintained, and that is exactly what the balance board system does, holds the voltage above 3.6v till all the cells are above 3.6v. The question is, why do it? If 3.5v is between 99% and 100% fully charged, what value is charging all the cells to 3.6v? Charging them to 4.2v is just asking for a short cycle life.
Here is a link to the Powerstream Technology report Charge voltage experiments with lithium iron phosphate batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage


T1 Terry

Well duh.. Yep they are FINALLY starting to get it. Why do they do this though?

Marketing! It is NOT for the health of the batteries. The Chinese win if these are "Drop In" voltages for lead acid. You lose if you believe them...
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Old 01-06-2015, 08:07   #4535
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LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Maine Sail, T1 Terry and other cruisers on this forum - I want to thank you for sharing your wisdom on LiFePo4 batteries. I was going to add these batteries to my Sprinter van RV, but in the end after lots of research I decided it was too much effort. I could adjust my Magnum inverter/charger and Blue Sky solar controller to get the proper voltage profile. But the biggest problem for my installation was dealing with charging from the Sprinter's alternator at 14.1 volts. Many RV manufacturers are going to lithium house batteries by adding a second separate alternator to charge the lithium pack. I now understand why and will wait for lithium in my next RV.
Cheers,
- - Mike
2013 Airstream Interstate from 2012 Sprinter 3500 tall & long
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Old 01-06-2015, 09:33   #4536
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Sailorgerry, would you mind identifying those 2 units you found to be programmable friendly to lifepo4. thanks
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Old 01-06-2015, 10:34   #4537

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

Mike-
Have you verified 14.1 volts as being the proper alternator output, with Mercedes? I know the Germans are doing all sorts of odd integrated "charge control" systems in their cars, but in my limited knowledge, while sloppy systems may roam anywhere from 13.8 to 14.4, none are set to 14.1 as a normal full-time output.
On the other hand, the difference between 14.1 and 14.4 could easily be lack of calibration or float in a meter, and not knowing your background, that could easily be missed.
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Old 01-06-2015, 17:02   #4538
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by T1 Terry View Post
Just read a report from Powerstream Technology date Feb last yr and the testing clearly showed the difference in capacity between charging at 3.4v per cell compared to 4.2v per cell was 3% at the most...

Charging them to 4.2v is just asking for a short cycle life.
Here is a link to the Powerstream Technology report Charge voltage experiments with lithium iron phosphate batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage

T1 Terry
Nobody is charging up to 4.2V anyway (especially fully absorbed) and haven't the main Chinese manufacturers of prismatic cells got an upper voltage limit of 3.65V these days...?
If it wasn't for them, hardly anyone would have lithium cells on board today, incidentally.

What is much more interesting in this article is that a fully absorbed charge at 3.4V resulted in near 100% SOC, something I had pointed out here a while ago after observing the exact same on my bank of prismatic cells and solar charging.
Unfortunately, it doesn't say how long it took to fully absorb each time and I didn't measure that either. I just know it became much longer as voltage dropped.

It emphasises once again that it is always important to terminate the charge with LFP, using lowish voltages doesn't work. It just makes charging inefficient, negating some of the very benefits of LFP.
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Old 01-06-2015, 23:19   #4539
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Sailorgerry, would you mind identifying those 2 units you found to be programmable friendly to lifepo4. thanks
Guvet - For diversion type controllers that can be set for lithium, Iíve been assured (but have not confirmed thru testing), the LVM 6TB charge controller distributed by Eclectic Energy UK, and the Schneider Electric C60 60 Amp Solar Charge Controller (aka Xantrex) will work. For a solar MPPT controller there are many, but I went with the ďKidĒ from a local company called MidNite Solar. Cheers!
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Old 02-06-2015, 08:06   #4540
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by hellosailor View Post
Mike-
Have you verified 14.1 volts as being the proper alternator output, with Mercedes? I know the Germans are doing all sorts of odd integrated "charge control" systems in their cars, but in my limited knowledge, while sloppy systems may roam anywhere from 13.8 to 14.4, none are set to 14.1 as a normal full-time output.
On the other hand, the difference between 14.1 and 14.4 could easily be lack of calibration or float in a meter, and not knowing your background, that could easily be missed.

Yes the voltage does vary from about 13.8 to 14.4. The real problem is you can't easily modify the the Mercedes control of the alternator. When steady state after driving for 15-20 minutes I see a fairly steady 14.1 to 14.2 volts.

The other problem I ran into in planning a LiFePo4 conversion of my house batteries was the minimal 2 gauge wire that Airstream installed from chassis battery under driver's seat to house batteries in rear of van. The Mercedes alternator is rated for 220 Amps and I didn't think 20 feet of 2 gauge wire would be adequate to charge a 400 AH lithium pack. Upgrading this wire was just more than I wanted to tackle.


- - Mike
2013 Airstream Interstate from 2012 Sprinter 3500 tall & long
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Old 04-06-2015, 21:21   #4541
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I’m currently setting up a 12 volt 800ah LifePO4 house bank using 8 x 400 ah Winston cells.

I’m working through my charge sources (Solar, Wind, Shore power and Alternators) and I think other than the alternators I can change to a suitable charge profile.
The boat has 2 Volvo D1-30F engines that have the factory fitted Mitsubishi A3TR0091 alternators that seem to be fitted with very basic internal regulators that are set to 14.3 volts and have no thermal protection that I can find. These work fine on the existing AGM bank and I see them often start at 70 amps then rapidly drop to 30-40amps depending on SOC. It’s not unknown for us to have to motor for 6 to 8 hours at a time, usually on 1 engine only, but still a long time.

My concern is that on the new bank I would expect the alternators to pump out their max at 110 amps x 2 at 14.3 volts. First problem is they will get very hot and probably not last long (they are expensive to replace), and 14.3volt into LifePO4 for extended periods I believe is too high. I will keep the existing LA starting battery so also need a way to split the charging. The factory fit some sort of battery charge combiner but haven’t looked at what it is yet, so currently both banks are charged by either alternator.

I spoke to Balmar about fitting an external regulator to the Mitsubishi and they said they can’t help. I spoke to a local auto electrician who claims he can give me a wire that will cut the field to effectively disable the alternator, and I will use this in the case of a High voltage event. As I understand it, it’s an all or nothing option. However I still have no good temperature protection for the alternators. I could rig some sort of temp sensor to cut the field as well when it gets too hot but I’m looking for something more “commercial”.

What I’m looking for is something that I can hang both alternators from (So has to accept 300 amps), that will take 14.3 volts in but limit the charge voltage to something lower like 13.8, along with some method of scaling back the alternators once they start getting too hot.

I was looking at the Sterling Alternator to Battery charger
Alternator to Battery Chargers up to 400A | Sterling Power Products
,however they have so far ignored my requests for information, so no idea if that would work. Their Lithium battery settings seem very strange, so not sure. They are expensive so don’t want to buy one just to find out.

Is there some other way I can protect the batteries and the alternators. Anyone running LifePO4 banks off a D1-30F Volvo, and if so how did you handle the problem? I do not want to add a second alternator x 2 and would like to keep the existing alternators


Thanks

Andy
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Old 05-06-2015, 02:03   #4542
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Andy,

Those are very good alternators, they are temperature protected and externally sensed. I run one on a Volvo D2-40 and it can get warm charging into the lithium bank, but nothing more ever happened.

Controlling their voltage etc was extensively discussed here earlier by Rolf (look for posts from roetter) who has the same engine.

Remember that it is not because you routinely motor for hours that you are going to run hot alternators throughout. They will only heat up as long as they are bulk charging and then cool off very quickly.

You have two options: reduce the voltage or just disable them once the battery voltage has exceeded a limit for a while. The second method provides faster charging, but this might not matter for you.

Whatever you do, split the outputs of each separately etc, don't combine them into a huge single charging source and don't mess them up with external regulators. Not only it will save you a fortune, but it will also be much more reliable.

Eric
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Old 05-06-2015, 08:00   #4543
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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My concern is that on the new bank I would expect the alternators to pump out their max at 110 amps x 2 at 14.3 volts. First problem is they will get very hot and probably not last long (they are expensive to replace), and 14.3volt into LifePO4 for extended periods I believe is too high. I will keep the existing LA starting battery so also need a way to split the charging.

What Iím looking for is something that I can hang both alternators from (So has to accept 300 amps), that will take 14.3 volts in but limit the charge voltage to something lower like 13.8, along with some method of scaling back the alternators once they start getting too hot.
Since your alternators are reported to have good overheat protection, your solution may be as simple as inserting a 120A rectifier diode in series between alternator and LiFePO4 bank.

For example two of these:

MPSC2N60U120 | MagnaChip MPSC2N60U120 Fast Rectifier Diode, 120A, 1200V, 110ns, 4-Pin SOT-227 | MagnaChip

one for each alternator. You will need a substantial heatsink, as each diode will be dissipating well in excess of 100W.

Look at Vf / A curve of those diodes though. These particular diodes have it quite steep. This may be a benefit or not, depending on how you look at it..

Another possibility:

VS-150U120D | Vishay VS-150U120D Rectifier Diode, 150A, 1200V, 2-Pin DO-205AA (DO-8) | Vishay

Going sailing now, so I'll answer any questions on that (if there are any) on sunday.
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Old 05-06-2015, 10:34   #4544
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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The factory fit some sort of battery charge combiner but havenít looked at what it is yet, so currently both banks are charged by either alternator.
I think the Volvo "charge combiner" is nothing more than a diode-based charge isolator. As such, it probably robs you of ~0.6V on the output side of it.

Have you measured 14.3V at the battery terminals with the alternators running? If not, then this Volvo combiner may just be solving your problem for you.

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Old 05-06-2015, 10:44   #4545
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Is there a maximum number of posts allowed in a given thread and are we getting close to it yet?
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