Lithium Batteries (for the rest of us)

[Lagoon4us]

Things get more muddled once you start splitting into banks. Lagoon4Us is splitting and sensing his SLA starting bank. The behaviour of the system will now depend a lot on the state of charge of the SLAs.
If they are full (usual), there will be greater voltage drop over the splitter (diodes or MOSFETs) on the path of the heavier current (to the lithiums) and the SLAs will always read higher. This will cause early current drop-off and then charge termination for the lithiums, before they reach the regulated voltage. You can leave quite a lot on the table this way. Low SLAs would result in a better charge for the lithiums.
Sensing the lithiums instead would give higher current for longer to the house bank, but the starting bank would tend to go over-voltage while the lithiums are charging.


Agree and this is why i've set mine up this way, true cruising involves a high degree of motoring and i really don't mind if our charge isn't totally effective it's just nice to bank some amps whilst motoring. This is a safe way to my mind.

The solar is the main hitter putting most charge in on any given day.

Continues to work extremely well and we are living aboard cruising the Greek Islands for the last 5 months or so.

Cheers Frank

[poiu]

Originally Posted by ebaugh

This value means little without a time at rest, and then only if there is no load.

We measured some brand new cells out of the box after arriving ocean freight at 3.4V. They were shipped at full charge!

One other thought....if you have a "load" 12V refrigeration, watermaker etc, the charger may be powering that at the end of the charge.

Thanks again for your input. Those measurements were with no other load. It was done as my final pre-haulout charge prior to disconnecting the battery until November. I will work on the system again then and probably buy the computer link for the charger so I can more accurately control settings.

[Jeff Millar]

How would you select a battery charger to charge a lithium - ion battery bank consisting of 2 - 12 volt - 300 ah batteries connected in parallel.
Would you buy a charger with a rated out put of 70 amps or 90 amps with adjustable input voltage levels.
Or what would one of you experienced experts care to recomment as the best.

[Maine Sail]

Originally Posted by Jeff Millar

How would you select a battery charger to charge a lithium - ion battery bank consisting of 2 - 12 volt - 300 ah batteries connected in parallel.
Would you buy a charger with a rated out put of 70 amps or 90 amps with adjustable input voltage levels.
Or what would one of you experienced experts care to recomment as the best.

We use a Sterling Pro-Charge Ultra and a "custom" setting. This charger allows you to build a custom program. With this charger I have it set to charge to 13.8V then drop to 13.4 which essentially turns it off unless a load kicks on. We very rarely use our battery charger though. Once the bank attains 13.8V it gets to a point where very little current will flow into the bank at that voltage. While it is not technically full, as in upper knee full, it simply gets to a point where 13.8V can no longer push any more current into the bank... It tapers to this level, in fairly short order, once the current starts to drop...

When on the hard I use a Mastech switch mode power supply with adjustable voltage and current settings and basically set it to run the "loads" but not really charge as I don't want the bank sitting at 100% SOC all the time. I prefer to leave the bank at about 50-70% SOC, if letting it sit.....

These batteries will work any charger very, very hard and this is why I prefer the power supply because I can turn it from its 50A rating down to 40A and it runs nice & cool and can do this nearly indefinitely. I had 30A unit but it proved too small for the cycle testing I was doing. I now run them in parallel and charge at 60A when needed. If I run the 50A at 50A and the 30A at 30A they begin to develop heat smell...If I knock 10A off each they run nice and cool. I also have a 100A charger that I use in the shop and have stacked all of them together to pack two 80% DOD cycles into one day......

I charge to well below the upper knee so as to prevent any potential for cell damage... As near as I can tell, via capacity testing, we give up about 7-10Ah's by only charging to 13.8V but that has been well accounted for. The cells have remained in perfect balance despite not pushing our BMS to shunting/balancing voltage level.... When I do push that high all the shunt lights come on at exactly the same time.....

As of Tuesday the bank has 164 cycles. A large number of those cycles to 80% DOD and many of those drawn down at a .25C load or greater (100A on a 400Ah bank)... 164 cycles to 80% DOD would leave many LA batts dead...

I am trying for 200 cycles before we pull the boat out of the water in November. It takes WORK to get to 200 cycles!!!! The nice thing is that we have had a cold fridge all summer despite being on a mooring.... The bad thing is my wife keeps complaining that we are freezing stuff because I have the fridge set so high in order to accelerate the cycling frequency.

I have been purposely deep cycling this bank because for me this is more of an experiment/product testing than for my own personal gain. I have been pushing this bank far harder than it would be on most cruising sailboats, just because I am curious.

Through hundreds of hours of testing and cycling this bank I have settled on 13.8V - 13.9V charging for my max voltage and it has been working flawlessly. Personally you would not see me pushing Winston cells higher, in daily practice, but that is where I have settled and I know others push higher...

I treat our BMS as a safety net only... Essentially we are using/charging/discharging our bank without a BMS despite it being there as a safety net. Others on here have ruined cells (Chris Witzgall & T1Terry that I know of) with no safety net to prevent it, so I do believe in having it to prevent my own HEF (human error factor) and save myself, from myself. So far we've never once come even close to utilizing it for LVD, HVC or for balancing....

In order to cycle deeply I had to install a manual alt cut switch and we often run the motor with the alternator off.......

[Jeff Millar]

Maine Sail,
Thank you for your reply that is exactly what I needed to know.
Your response is very much appreciated.

Jeff

[roetter]

I have my install finished now and have done this:
- a total of 360Ah (2x180) in 8 cell, 2 each in parallel then 4 in series. 2P4S
I left my shore charger (Quick251, 25A )
and
the 115A Mitsubishi alternator
and
an old unregulated 12V panel 100W

I made the following modifications
JLD 5740 programmable volt meter currently set to these values
High cut off 13.8 for the winter I will set this to 13.4
High cut in 13.2 for the winter I will set this to 12.8
Low cut of 12.0
Low cut in 12.4

The voltmeter's high and low relays lead to a small relay board with 4 isolated relays that can switch 12V DC 10 A or 250V AC 10A.


Relay 1 - LVC switches a Blue Seas solenoid
Relay 2 - HVC switches the solar panel
Relay 3 - HVC switches the power 110V AC to the shore charger
Relay 4 - HVC switches an automotive SPDT relay. This switches the alternator voltage sensor between two locations.
Location 1: With no HVC triggered it connects the voltage sense to directly after the split diode. Here it measure the house bank voltage plus the drop in the long charge cable. At 100A this voltage drop is significant and that reduces alternator output rapidly (30 seconds) to about 80A. That is what I want as otherwise the alternator or belt may be dead soon.

Location 2: With HVC active it switches the alternator voltage sense to before the split diodes (basically to the voltage at the alternator). Since the alternator is set to 14.3V, and with 0.7V drop at the diode, I get 13.6V at the house bank (minus cable drop). Once this kick in the alternator outputs 0A, and the house bank voltage slowly drops down until it reaches 13.6V. Then it settles in at that lower voltage with fractions of amps going in or out.

I still have the original voltage sense cable directly from the house bank and can easily exchange the two for power-charging. This I would only do if near full and I want the batteries charged in a short time to all full.

At the voltmeter I have a pushbutton momentary switch that lets me drop the voltage sensed at the voltmeter by about 0.8V. With this I can force the HVC state to off for immediate start of a charge cycle.

I am currently on shore power 'cycling' in the upper band the batteries with the fridges on full blast and logging with a Junsi CL

[hellosailor]

Terry-
First you say that charging over 3.4 volts causes damage, then you say to charge to 3.6 volts. And Balqon say their "12" volt batteries have an operating range from 11-16 volts, which is a full 4 volts per cell. In normal operation, no mention of damage.

Maybe you can explain those apparent contradictions to me? Maybe "16" was just a typo for "13.6" and two characters got left out of the middle, huh?

"This would indicate the batteries will cycle for at least 10 yrs " {The Mars rovers]
Well, that would indicate that NASA had a working BMS ten years ago, along with a good battery chemistry. Perhaps someone could find out what they did, so we could just follow that example and ignore all the rubbish being passed around today.

[familycruisers]

Best price on CALB cells anyone?

[goboatingnow]

I would personally prefer to switch the alternator off if a HVC occurred. If you loose the diode pack you could be in trouble.

Why are u adjusting hvc voltage in summer and winter ?

Mainesail your cutoff voltage seems very low. I mean it corresponds to 3.45v. At that level at greater then .2C you could end up with less then 60% charges
I agree with disconnecting the charge and enduring a deep discharge.

Mention was made of alternator charge cycles.
Standard car alternators are design to power the electrical needs of the car. Not primarily charge the battery. Hence almost all I've seen are set to just regulate at a around 14v , this is a point that LA can withstand for long periods ( and cars are rarely run for very long periods ) there is no float charge in car alternators because they are powering loads.

[Maine Sail]

Originally Posted by goboatingnow

Mainesail your cutoff voltage seems very low. I mean it corresponds to 3.45v. At that level at greater then .2C you could end up with less then 60% charges

Dave,

I capacity tested it on numerous occasions and am only losing about 7-10Ah as near as I can tell but never discharged below 2.8VPC.. At a 13.8V charge, to a taper of 5A current, which is where I cut off the charging, I would apply a 100A load (.25C) and I was still recording 390 - 405Ah out of a 400Ah rated bank before hitting a low voltage of 2.8 VPC...... We have our battery monitor calibrated for 380Ah's which compensates...

The regulator does not terminate charging at 13.8V that is the voltage limit setting for the regulator. It continues to charge at 13.8V taking what the alt can throw at it. I have timed the bulk & absorption times to correspond to a 50% DOD, time wise, for a recharge before dropping to a voltage level of 13.4V. I usually just manually turn of the alt when we hit 5A of accepted current at 13.8V..

If I cycle to 80% DOD, and need more time at 13.8V, I simply do a reset of the regulator and send it back into absorption mode at 13.8V. At 13.8V it will then eventually taper the current down towards 80A, 50A then down towards 10A then to about 5A at which point I deem it full..... This entire tapering time is still pretty short.

I've tested the bank in a range from 13.8V to 14.2V and the capacity is not changed much above 13.8V if I let it taper at 13.8V to 5A of accepted current..

With that in mind I have played around with it and decided to keep the voltages at under 14.0V (3.5VPC) with 13.8V being where I have settled for now.. Earlier in the season I was upwards of 14.1V but only noticed that I came up to voltage a little later and tapered current slightly faster. With an unlimited charge source the charging is slower at 13.8V but boats don't have unlimited charge sources. The 13.8V does not seem to limit our speed of charge, keeps us well out of the knee range and we are getting the vast majority of capacity in the bank. The cells have also remained in perfect balance through 164 cycles thus far...

[roetter]

Originally Posted by goboatingnow

I would personally prefer to switch the alternator off if a HVC occurred. If you loose the diode pack you could be in trouble.

Why are u adjusting hvc voltage in summer and winter ?

I am only changing the alternator sense voltage location, that will not cause any trouble for the diode pack. I am not disconnecting the batteries from the alternator.

Summer = I use it at least every few days. = higher cut-off voltage to have a boat ready to use. The alternator will fill the rest of the battery during the 15minutes it takes to motor out from the marina and start sailing.

Winter = She sits for months unused, so I just want to stay at a lower SOC (maybe 80% max) for the small draws of displays and monitoring loads. = lower cut off voltage.

[kevenbenz]

Pls pay attention to Maine's replies,so professional of the LFP batteries,pls do care about all those questions,the charge/discharge current/voltage,and maxiumum of that,will need the BMS to balance them all,if ur build them up by series and parallels should matching all the single cells in advance .or there will be some safety issues,it's dangerous.

Regards
Keven

[kevenbenz]

Originally Posted by familycruisers

Best price on CALB cells anyone?

how is the quality of it?

[goboatingnow]

Originally Posted by Maine Sail

Dave,

I capacity tested it on numerous occasions and am only losing about 7-10Ah as near as I can tell but never discharged below 2.8VPC.. At a 13.8V charge, to a taper of 5A current, which is where I cut off the charging, I would apply a 100A load (.25C) and I was still recording 390 - 405Ah out of a 400Ah rated bank before hitting a low voltage of 2.8 VPC...... We have our battery monitor calibrated for 380Ah's which compensates...

The regulator does not terminate charging at 13.8V that is the voltage limit setting for the regulator. It continues to charge at 13.8V taking what the alt can throw at it. I have timed the bulk & absorption times to correspond to a 50% DOD, time wise, for a recharge before dropping to a voltage level of 13.4V. I usually just manually turn of the alt when we hit 5A of accepted current at 13.8V..

If I cycle to 80% DOD, and need more time at 13.8V, I simply do a reset of the regulator and send it back into absorption mode at 13.8V. At 13.8V it will then eventually taper the current down towards 80A, 50A then down towards 10A then to about 5A at which point I deem it full..... This entire tapering time is still pretty short.

I've tested the bank in a range from 13.8V to 14.2V and the capacity is not changed much above 13.8V if I let it taper at 13.8V to 5A of accepted current..

With that in mind I have played around with it and decided to keep the voltages at under 14.0V (3.5VPC) with 13.8V being where I have settled for now.. Earlier in the season I was upwards of 14.1V but only noticed that I came up to voltage a little later and tapered current slightly faster. With an unlimited charge source the charging is slower at 13.8V but boats don't have unlimited charge sources. The 13.8V does not seem to limit our speed of charge, keeps us well out of the knee range and we are getting the vast majority of capacity in the bank. The cells have also remained in perfect balance through 164 cycles thus far...

Why are you talking about bulk, absorption and float in the context of Li, its has no meaning.

I understand you leave the alternator at 13.8 and left the current taper off and you do this manually. now I see what you are doing.

Dave

[goboatingnow]

Originally Posted by roetter

I am only changing the alternator sense voltage location, that will not cause any trouble for the diode pack. I am not disconnecting the batteries from the alternator.

Summer = I use it at least every few days. = higher cut-off voltage to have a boat ready to use. The alternator will fill the rest of the battery during the 15minutes it takes to motor out from the marina and start sailing.

Winter = She sits for months unused, so I just want to stay at a lower SOC (maybe 80% max) for the small draws of displays and monitoring loads. = lower cut off voltage.

The primary purpose of HVC monitoring is to prevent an individual cell getting out of balance in a series string and hence receiving greater that its allotted cell voltage. HVC on simply the charging voltage of the battery bank , really isnt doing anything at all,

What you are doing is more like charge termination. HVC is meant to be a fault protection

What I meant by the diode pack , is that if it blows out to a short circuit , your scheme looses its protection. I prefer HVC to cause a disconnection of the charting sources and I do not automatically reconnect on a HVC event terminating

HVC should be set about the charge termination voltage set point IMHO
Dave