LiFePO4 Batteries - Okay Tear Me Apart ;-)

[Tinkerer007]

Originally Posted by s/v Jedi

**Snip**

price LA : $2,220.-
price LFP : $2,640.- plus BMS
**Snip**
cheers,
Nick.

Be aware that you have to add 10% for shipping from China to US and then there will be additional shipping within the US. So:

price LFP: $2,904 plus BMS

might be more realistic. I think the US shipping for my 4 cells was ~$50. My total was $1017 for the 4 200 AH TS cells.

[hellosailor]

Nick-
"no. of LA terminals to wire: 12
no. of LFP terminals to wire: 24 (double the wiring plus BMS wiring)"

What am I missing here? One LFP cell should replace 1-1/2 LA cells, 3v vs. 2v nominal, so the LFP cells should also give you less wiring to do, assuming availability on a similar cell/battery level, no?

I suppose...with LFP cells holding a more constant voltage across their cycle range, that should also give them another incidental benefit, i.e. anyone powering a radio transmitter or other voltage-dependent devices would see more consistant operation from a LFP supply rather than a LA supply. (And the downside, you won't be able to tell your battery is getting low because the cabin lights are growing dimmer.<G>)

[s/v Thea]

Originally Posted by Tinkerer007

I expect that the battery will shut down this evening around 5 PM (23 hours later). I hope I can get home before 5PM so I can witness the event.

Bob,

If electric1's graphs are correct you should have charged to 95%, LVC should occur around 5% so you should get 90%*200/6.4= about 28hrs.

Will be interesting.

Doug

[electric1]

Originally Posted by hellosailor

What am I missing here? One LFP cell should replace 1-1/2 LA cells, 3v vs. 2v nominal, so the LFP cells should also give you less wiring to do, assuming availability on a similar cell/battery level, no?

LA batteries don't come with individual cells exposed, you usually get 2 terminals for 6V or 12V battery. LFP cells come with 2 terminals for each 3V cell, but they usually ship with busbars and not require any additional cables, so its all basically a moot point.

[s/v Jedi]

I selected the 200Ah because it is half the capacity of the LA batteries I have now so that I get three strings again... just to make the comparison better. Yes, you can use bigger LFP cells but you can also use bigger LA cells.

Electric is right, the LA I use now are 6V. The number of terminals is important because of the corrosion issues in a marine environment. The busbars they ship with the LFP cells are just copper, not tinned so that will not do (will be one big mess on most boats). This means a lot of spraying (but underneath the jumpers is very hard to get to) or using tinned copper instead.

I like three parallel strings because it's doable to loose one of them. If you have two strings you lose 50% capacity when you loose one and are often left with too little to operate the boat.

Yes, the prices are wrong but I guess the LA also have their shipping costs and at 3x the weight, this won't be cheap either...

cheers,
Nick.

[LiFeTech Energy]

Originally Posted by electric1

LifeTech, nice to see you here, I know you from DIY EV forum. I agree that you generally get what you pay for, but I would disagree that everything from China is poor quality. Most of the Western world lives on stuff made in China, you just need to pay attention to what you buy and who you work with. I understand that you are promoting highest quality product and its what I call a "Cadillac solution" , but there is a big world out there and plenty of people who are perfectly satisfied with "Honda solution". My product falls into that category and I stand behind my quality and reputation and will not let anyone bash it just because it costs less than alternatives. I do my business with minimum overhead, but I never compromise on quality and support, so please try to keep a humble attitude when referring to your competition.

I have to agree with you electric1. No problem there. I am sure you take care of the quality control issues yourself (which is good to see) since QC is where so many of the Chinese made cells are very lacking. There are those exceptions which are mainly western countries which have their own battery manufacturing plants in China and make their cells to an internationally recognised quality standard such as ISO9001 or similar.

[Tinkerer007]

Originally Posted by Tinkerer007

In my garage I found a spotlight to hook up to my battery. It started draining at 6.6 A, but after 20 minutes, it was down to 6.4A. This morning (12 hours later) it was at 6.37 A. I expect that the battery will shut down this evening around 5 PM (23 hours later). I hope I can get home before 5PM so I can witness the event.

It was still going when I got home at 5:15 (23 hours). Amps was at 6.37, and voltage was at 12.73 V. Unfortunately I won't be measuring Amps with that meter anymore. I tried to measure voltage with it plugged in the Amps plug.

And it is still going 27 hours later.

[Viking Sailor]

Originally Posted by Tinkerer007

It was still going when I got home at 5:15 (23 hours). Amps was at 6.37, and voltage was at 12.73 V. Unfortunately I won't be measuring Amps with that meter anymore. I tried to measure voltage with it plugged in the Amps plug.

And it is still going 27 hours later.

There may be a fuse inside the meter to protect it against trying to measure amps directly across a voltage source.

[s/v Jedi]

Hey tinkerer: open the meter up, there's probably a replaceable fuse there. Now how do I know that...

cheers,
Nick.

Edit: gee Viking, you're too fast; we've been typing the same thing at the same moment ;-)

[Tinkerer007]

Yeah, no such luck. Well there is a fuse, but it is only .5 A. But there was the smell of burned silicon and the residue of some part with the traces lifting off the PCB. The voltage was working till I took it apart to look for the fuse, but now I can't get the switch mechanism back together. It was a nice meeter that I got 20 years ago (looks like a Fluke, but is made by Philips.) Maybe, I will be able to put it back together int he daylight.

If not, what is a good meter to get?

[Viking Sailor]

Originally Posted by Tinkerer007

Yeah, no such luck. Well there is a fuse, but it is only .5 A. But there was the smell of burned silicon and the residue of some part with the traces lifting off the PCB. The voltage was working till I took it apart to look for the fuse, but now I can't get the switch mechanism back together. It was a nice meeter that I got 20 years ago (looks like a Fluke, but is made by Philips.) Maybe, I will be able to put it back together int he daylight.

If not, what is a good meter to get?

Sorry old buddy - s**t happens! Next time don't listen to Nick.

Flukes are good. I've even had good luck with mid-range Radio Shack meters.

Good luck,

Paul

[goboatingnow]

Electric1 , thats an interesting set of charging graphs . I looked at Thundersky data and couldnt square there charging graphs with by understanding of Li technology. But interestingly since liFepo4 doesnt exhibit thermal runaway, I suspect the charging graph should reflect that by not showing a massive HVC event.

Thats what I like about Li tech ( and designed a fair few chargers). There is a well defined voltage knee that is easy to detect

I would say however, back to my hobby horse, is that boating actually needs an integrated DC charge controller product line. Boats tends to be wierd collections of hi-tech stuff and stuff mr Edision would recognise. A Integrated charge controoler would accept and control Alternators, wind gens, water gens, DC generators and solar panels. perhaps its needs to be modular in nature so that poeple add control modules as they require.

ALso looking at LiFepo4 tech, and knowing boats as I do, both HVC and LVC events are very unlikely, actually one of the issues is that 4 Li cells in series gives a voltage thats a little low in comparison to LA ( though there is the Lead acid droop). However well before LVC every device on the boat will have basically stopped and everything electronic will be screaming at you. Hence Hard LVC disconnects are OK. ( In fatc there are a lot of LA " battery savers" that do just that. HVC is a simple controlled disconnect as well. The rest are just monitored voltage set points.

DAve

[Tinkerer007]

Originally Posted by Tinkerer007

It was still going when I got home at 5:15 (23 hours). Amps was at 6.37, and voltage was at 12.73 V. Unfortunately I won't be measuring Amps with that meter anymore. I tried to measure voltage with it plugged in the Amps plug.

And it is still going 27 hours later.

So the spot light lasted 30:15. (At least the spot light was on and shining down the hallway at 30 hours, and then out 15 minutes later.)

That is about 6.4 A x 30 H = 192 AH.

Any other tests I can do before installing in the boat?

[s/v Thea]

Originally Posted by Tinkerer007

So the spot light lasted 30:15. (At least the spot light was on and shining down the hallway at 30 hours, and then out 15 minutes later.)

That is about 6.4 A x 30 H = 192 AH.

Any other tests I can do before installing in the boat?

Sounds good!

Be interesting to put your charger on them and see how long it charges at max amps.

Doug

[Tinkerer007]

I put the charger on last night and then promptly went to bed. I didn't even think to check on it this morning.