LiFePO4 Batteries - Okay Tear Me Apart ;-)

[gael]

Originally Posted by McG

. Also, a major concern is I will have 2 banks of 4 cells each, connected in parallel to give me 12v 800Ah. Will I need 2 chargers, one per bank? Will I need 2 BMS'es? Will I be able to use 2 isolated chargers (Ctek XS25000) in parallel over both banks or is it better to have a charger on each bank?
Hoping to hear from you soon.

I have two 24V 130Ah bank with one charger and spliter (Victron) to fill the two banks in a same time( not in parralel) and one BMS per bank.
For the service, the 24V rail is connected to one bank only and you can select the bank to be used. Connecting the two banks in parralel could generate a massive peak of current if the two bank are totally misbalanced. In my set up it is impossible to have both banks connected in parralel. Each bank has its own switch.

rgds
gael

[McG]

Originally Posted by gael

I have two 24V 130Ah bank with one charger and spliter (Victron) to fill the two banks in a same time( not in parralel) and one BMS per bank.
For the service, the 24V rail is connected to one bank only and you can select the bank to be used. Connecting the two banks in parralel could generate a massive peak of current if the two bank are totally misbalanced. In my set up it is impossible to have both banks connected in parralel. Each bank has its own switch.

rgds
gael

Thanks for the info Gael. My next question is: Having such a big bank, I need a grunty charger to get it filled. Will it work to use 2 isolated chargers in parallel over one 400Ah bank? The reason I ask is because I already have 2 Ctek 25Amp chargers. So I was hoping to get 50A out of them in parallel.

[gael]

Originally Posted by McG

Thanks for the info Gael. My next question is: Having such a big bank, I need a grunty charger to get it filled. Will it work to use 2 isolated chargers in parallel over one 400Ah bank? The reason I ask is because I already have 2 Ctek 25Amp chargers. So I was hoping to get 50A out of them in parallel.

Well 50amp in a 400Ah bank means a minimum of 8hours full load charge if your bank is deep discharged. You will lose a big benefit of the Lithium bat, but I did the same mistake to (50amp in 2 * 130Ah)
I never tried to connect 2 chargers in parralel on one bank. I have no idea of the Ctek output diagramm, but I fell it should work as long you can kept them stupid as possible, and use two fast fuses in case of.
Are they trimmed on 28V or a bit more?
rgds
gael

[McG]

Originally Posted by gael

I never tried to connect 2 chargers in parralel on one bank. I have no idea of the Ctek output diagramm, but I fell it should work as long you can kept them stupid as possible, and use two fast fuses in case of.
Are they trimmed on 28V or a bit more?
rgds
gael

I'll try that. This is a 12V system, so chargers trimmed at 14.4V. I'll have a look and see if it is adjustable inside maybe. I'd like to charge at 15v.

[gael]

Originally Posted by McG

I'll try that. This is a 12V system, so chargers trimmed at 14.4V. I'll have a look and see if it is adjustable inside maybe. I'd like to charge at 15v.

Be carefull, check what is the max voltage your cells can accept. 15V for 4S seem to be a bit high in my mind.This max voltage should be given in the cell specification.
Can you measure the charge current when Vbat reachs 14V and above? Just to see when your pack starts to be saturated and Vbat rises very fast.
rgds
Gael

[McG]

Originally Posted by gael

Be carefull, check what is the max voltage your cells can accept. 15V for 4S seem to be a bit high in my mind.This max voltage should be given in the cell specification.
Can you measure the charge current when Vbat reachs 14V and above? Just to see when your pack starts to be saturated and Vbat rises very fast.
rgds
Gael

Max is 16v. I can visually monitor it. I just got myself a MeanWell 15v 1500w Lifepo4 charger that is capped at 15v. I'll keep a close eye on the charging the first few times though.

[gael]

Originally Posted by McG

Max is 16v. I can visually monitor it. I just got myself a MeanWell 15v 1500w Lifepo4 charger that is capped at 15v. I'll keep a close eye on the charging the first few times though.

Interesting. I bough my cells from CALB; max volt/cell is 3.6V. Seem your cells max volt is 4V. which brand are they?
Anyway, as these toys can handle huge power and 'm new with this technology, I'm always very carefull. I have not yet installed an fully automated chrage-discharge system on my boat. Every action is done after checking the monitors -aprox one time a week.

[McG]

Originally Posted by gael

Interesting. I bough my cells from CALB; max volt/cell is 3.6V. Seem your cells max volt is 4V. which brand are they?
Anyway, as these toys can handle huge power and 'm new with this technology, I'm always very carefull. I have not yet installed an fully automated chrage-discharge system on my boat. Every action is done after checking the monitors -aprox one time a week.

This is what I imported: Battery spec
I'm planning to grab one of "electric1's" BMS'es today. It looks like a good system at a good price. He gave me very good advice. He recons, when you receive the cells, connect the lot in parallel for 24Hrs. That will remove any imbalances. I think it will be a good way to maintain the balance i.s.o. a BMS in the long run but I cannot just disconnect the batt - it is used 24/7 and it is quite impractical. So I'll go with the BMS.
BTW, what's this you say about discharge? Do you actually have to discharge the batt for some reason?

[sytaniwha]

Hi,

Below is a description of my 400Ahr LiFePO4 bank using 4 * 400Ahr CALB cells for the house bank of our 46ft cruising yacht, plus a link to an interesting video on LiFePO4 charge/discharge characteristics.

McG you may find this link interesting of a video by a Carnegie Mellon Robotics Institute PhD talking to a group of electric car enthusiasts about LiFePO4 charging and conditioning.

Robotics Institute: Videos

He recommends an initial charge/discharge cycle with your cells all in parallel, and stopping at a well defined curve point (e.g. very near full charge or full discharge), to initially ensure all your cells are at a very similar SOC. This is a step further than the good advice offered to you by Electric1.

Also, some of the earlier posts recommend matching your cells for capacity and internal impedance very closely at the factory, and I also think that is critical.

I purchased 4 * 400AHr cells off CALB direct earlier this year, and asked them to match as closely as possible. When they arrived, with the equipment I have I couldn't measure a difference in capacity or impedance, and parallel charge/discharge showed no imbalance (by monitoring individual cell current).

I was also very impressed with CALB's customer service. The sales person still contacts me every few months to see how the cells are, and answers tech questions very quickly.

I run the cells as a 12V (nominal), 400 Ahr bank. They replaced a 600Ahr Trojan SLA pack, and provide more useful energy per discharge. Another side benefit is that I don't have to worry about self-discharge ruining the cells when I leave the boat for an extended period.

I'm currently charging using a 120A alternator through a Sterling Power regulator, and a Victron 50A galvanically isolated mains charger. Both can have their charge parameters changed to fit the ideal charge curve for whatever brand of LiFePO you're using (I note that different brands have some quite significantly different charging parameters).

I use a Vetus Battery Watch unit which controls low voltage cutoff at the pack level to the consumers. Combined with the high voltage cutoff provided by the charge sources, this produces the sensible separation between charge and discharge as suggested by OceanPlanet (i.e. after a low voltage cutoff, the cells can still be charged, whilst a high voltage cutoff doesn't remove the ability for the consumers to draw power from the battery).

I was originally going to add a cell-level BMS, but agreed with GoBoatingNow's comments back in Mar/Apr 2010 that cell level probably isn't necessary for a relatively low current situation (like a typical cruising house bank), especially when there are only a few closely matched cells (4 in my case). My usage thus far supports that view, so we'll see how it goes in future.

I figured that as worst case I might have to do a parallel charge/discharge cycle manually on an annual basis to realign the cells, but I can't detect any drift thus far, so that may not even be necessary.

Anyway, I hope that this info helps some people. Also, thanks to those of you (Gael & OceanPlanet spring to mind) for starting to put real user data on this post - I find it helpful, and gives me areas to think about. Actual user data and experience trumps manufacturers' propaganda and people's general conjecture every time.

Cheers,
Paul.

[sytaniwha]

For those of us who are users of LiFePO4 technology in sailing house bank applications, and who want to have a forum to discuss our data, knowledge, ideas, and failures, I have just started another thread:

http://www.cruisersforum.com/forums/...rum-65069.html

I am looking for real users to talk about real applications, and avoid the long theoretical debate about the merits of the technology, and also avoid manufacturers trying to boost their cells vs another's.

Hopefully it will turn into a useful resource for ourselves and others who may want to use the technology in the future. I think there are probably enough of us using it now to make that possible.

See you there,

Paul.

[Highland Fling]

Well having spent the last six hours reading this very very interesting thread I find it breaks down into a few mindsests some are very helpful and others i find a bit worrying. I have real issues with the anti China nonsense and the main perpetrator of that seems to be wearing blinkers and bad mouthing / slagging off other peoples products. That totally unnecessary attitude and behaviour would ensure that i never went near his company and products even if they are making some sensible posts here it gets swamped with the negativity. So lets look at some facts that they did get wrong A N Other has posted a correction about warranties and guarantees so no point in covering that again. Then Nike have never made shoes in the USA and are not a manufacture but a marketing organisation using cheap foreign labour (far eastern) to make their products. Nike FAQs | Global Exchange

I noticed that some these (their) really good LiPo batteries were made in Taiwan (pretty close to China and soon to be part of China) The biggest sail maker in the world is in China http://www.china-sail-factory.com/index.aspx and Niger Calder no less seems to think they do a great job as do many of the BIG LABEL sailmakers who have their sails made in the China sail complex (not that all of them are willing to admit that) http://www.leesails.ca/images/Sailsfromchina2.pdf.

Now what do i know about LiPo batteries not a lot though i have been using them in my R/C planes and Helicopters for more years than i can remember. BUT like any battery if you dont treat them right you are going to have problems TOTALLY NOTHING NEW THERE.....I am seriously interested in some LiPo batteries and discovered Bruce at OceanPlanet and was seriously gobsmacked at the cost of the GenaSun solution CBA and ROI figures look great and the fact that they have a massive acceptance rate hold the voltage stable are much lighten than a LA battery BUT seem to be taller :-(. Then i found this thread and WOW. Electric1 has some great posts and being an engineer myself (electrical electronics and computing) they seems to be offering solutions that would fit in well with my mindset and bank ballance ( not that i yet understand the cost of there solutions/offerings suggestions - lots more reading and research needed i see). MY BIG ISSUE is that i want to charge my batteries much quicker and yes cover your eyes i use my main engine for this. At the moment i have 11 year old Gel cells that just refuse to die and long may that continue as i cant really get the CBA and ROI figures to work for me burning diesel vis a vis solar panels and wind generators. We cruise the Caribbean for six months of the year and i doubt if we spend $300 on buying diesel for our 54 HP Yanmar. So to one expert poster for this person you are a big big turn off to most of the others very very interesting. Now to read the other LiPo therads and yes i know it should be LiFePO4 but been calling these 'sort' of batteries LiPo for years :-)

regards

David

[rebel heart]

So 2-3 years later, any updates from the people who are using the li batteries?

[senormechanico]

Only one year, but they're as good as the day I put 'em in and the fridge has been running the whole time without any shore power (Four 200aH HiPower LiFePo4 cells).

I just got back from an overnighter and we woke up to 85% charge on the BlueSky monitor.
Last night, we had been using the wifi, laptop, making smoothies with the Vitamix (1500 watt motor), running the furnace, and don't forget wife's 1675 watt electric hair dryer for a few minutes.
Before anyone gets in a tizzy about the hair dryer, I confidently let her know it was perfectly ok to take it, as the batteries are fine with it and the solar will keep us in fat city (and they do).

Last evening while the Vitamix was running, I took a look at the monitor.
We were running the laptop, wifi, lighting, furnace and the Vitamix.
Total current draw was 132 amps.
The voltage went from 13.2v before the Vitamix was on, to 12.3 after it had been running for about a minute.
As soon as she turned off the 1500 watt load, the voltage went immediately back to 13.2 v.
Due to the slightly higher voltage, our Spectra watermaker makes noticeably more GPH with only a perceptible increased amperage.
You couldn't PAY me to go back to FLA's.

[downunder]

Impressive

[McG]

Originally Posted by rebel heart

So 2-3 years later, any updates from the people who are using the li batteries?

Yip. My 800 (4x200) AH Winston pack is still serving me like the day I fitted it 2yrs ago. I also fitted a Battery Management System (all about it elsewhere on the forum). I live in my motorhome and run a big compressor fridge/freezer 258l, 2 diesel heaters etc. Charged by 407Watt solar laminates. From May to Sept I charge approx once every 10 days from mains. (Hardly any sunshine in New Zealand during winter.) I will not consider LA's even remotely. I'll probably replace my car batt with lifepo4 too when time comes. It is such a carefree system.

We went overseas for 3 months. I switched off all the appliances but left the solar on thru an outback 80 controller. She was all sweet when we returned and I just hooked it all up again.