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

[Surf City]

Well, I think I am following along with the concept of parallel and series, but before I get to set up - I would like to ask amp hours usage. If you use 200 amps a day on a 12 volt system, how many days would you like to have in storage? We have a 700 watt solar system with a MPPT and a generator but on rainy days I like hearing the rain fall. Do you have a two or three days backup, ie 500 to 600 ah of usable Lithium battery?

When I begin to buy cells to install said ah, do you create more problems having 100 ah cell vs 260 ah cells? At 100 ah, you will have 40 links if you follow Pauls #4 method vs 24 links using 260 ah cells. I believe I counted correctly. You have more potential to have a problem with more connections. I know if one cell is to have a problem, it will be more money to replace a larger cell. What is the chance that you will have a bad cell, new technology? Anybody have their input as to what method they think is the best way to build a battery bank using 500 to 600 usable ah?

Has anybody used the company on ebay in the US for Winston batteries? His rating is very low and not great feed back. Who in the US or where can I find a good source for cells world wide? Splashing the boat in June.

On the learning curve!

Wil

[T1 Terry]

Small cells in parrallel or big single cells?

Here is a couple of You tube links and a DIY EV forum link that shows what is actually inside the plastic cell box. In the video the plug is removed from the top of the cell, some of the better manufacturers use valves and some of the others just use a plastic plug like in the video. If you read the forum link, about 7 posts down, he admits he got it wrong about the gassing causing the swelling. It is gassing, it just the gas leaks out and when the plastic body of the cell cools it goes hard again, just a property of the plastic use.

[Surf City]

Thanks Terry, I could not down load the sites that you listed but I get the point. What are your thoughts of other manufactures of lithium batteries?

Wil

[T1 Terry]

Bugga, does this one work

[bcn]

As I'm about to place orders for the components of our planned housebank (400Ah) so the question if after those two more months from the last reports our "guinea pig users" have to report news or add advice from their experiences?

How are the things going?

bcn

[OceanPlanet]

Originally Posted by bcn

As I'm about to place orders for the components of our planned housebank (400Ah) so the question if after those two more months from the last reports our "guinea pig users" have to report news or add advice from their experiences?

How are the things going?

bcn

You might get a kick out of this recent 1080Ah x 24V installation in the new Coastal Craft IPS6....

[bcn]

Originally Posted by OceanPlanet

You might get a kick out of this recent 1080Ah x 24V installation in the new Coastal Craft IPS6....

Neat, but perhaps not our size...

Two observations:
- in this building a BMS is in place (have a look at the battery bank)

- power outlet 120V AC - would prefer a watertight one down there

bcn

[OceanPlanet]

Yes of course a BMS is in place! Trying a system that size without full protection would be insane. This one is 3 x 360Ah X 24V, each 360Ah bank is 2 x 360Ah x 12V packs.

The builder could certainly do watertight on everything if that's what their client wanted.

Note that on boats like Telefonica (currently leading the VOR), their Genasun system is completely sealed in separate watertight boxes (they also have 3 parallel banks).

[T1 Terry]

The 4 house battery set up currently in full time use that I'm associated with are operating faultlessly. there are two big 800Ah X 24v systems on the plan and build side going at the moment, no proprietary BMS systems on any of the set ups, just the $28 cell logger alarm for cell over or under voltage, so far after 9 mths the only system that has triggered an alarm is mine and that was due to my stupidity, accidentally connected a solar panel set directly to the batteries instead of through the solar control. No harm done, the alarm alerted me to the problem, reconnected the 2 offending cable to the correct bus bar and all was fine again.
My system pulls 240Ah to 270Ah out overnight every night, if the weather is crap for 3 days with bugger all solar input the system has occasionally dropped to 0% SOC and the inverters have actually dropped out once with the low voltage cut out, 10.5v, 2.6v per cell. As soon as the load dropped the cells recovered to 3v, the Ah out totalled 739Ah, not bad from a 720Ah bank. Turned the charger on and 720Ah went back into the batteries before the charge rate started to reduce, 100% SOC and 739ah rolled up less than an hr later. After the first time that happened I watched my batteries a lot less, did a cell log after a few days ago, cells still remain within 7 millivolts of each other. once the cells are top balanced and the system has settled (around 3 mths use) the batteries stay balanced, they don't run a muck just because there is no BMS fitted as long as the max charge voltage remains below 3.45v per cell, even at 3.5v per cell after they have settled doesn't seem to cause any issues.
No matter how many cells you put in parallel to build capacity there is still only 4 cells in series to build a 12v battery so there are only 3 cells that can drift higher or lower than the others, it just doesn't happen in house battery system, the loads are big enough, the charge rate isn't high enough and there aren't enough cells in parallel.
Think about it, the cell operating voltages are between 3v and 3.4v, if the charging voltage is limited to 13.8v then even if 3 cells were to remain at 3.3v while charging the highest the 4th cell could reach is 3.9v, the max safe limit is 4.2v. I wouldn't recommend regularly pushing a cell to 3.9v and it's highly unlikely to ever happen, 600millivolts across 4 cells in a bank just doesn't happen unless a cell has failed. The cell loggers have an alarm setting for the max differential between the highest and lowest cell so if that was set at 500 millivolts the alarm would sound before the cells got that far apart and a high cell voltage alarm of 3.6v would go off before a cell went that high either but if you weren't there or busy trying to stay upright and alive the batteries would be destroyed even if the alarms are sounding. Simply turning the charge off will sort the problem and it can be dealt with at a more convenient time.

T1 Terry

[goboatingnow]

Originally Posted by OceanPlanet

Yes of course a BMS is in place! Trying a system that size without full protection would be insane. This one is 3 x 360Ah X 24V, each 360Ah bank is 2 x 360Ah x 12V packs.

The builder could certainly do watertight on everything if that's what their client wanted.

Note that on boats like Telefonica (currently leading the VOR), their Genasun system is completely sealed in separate watertight boxes (they also have 3 parallel banks).

Absolutely no need for a bms, a simple under and over voltage detection system is all that's needed

Dave

[OceanPlanet]

Originally Posted by goboatingnow

Absolutely no need for a bms, a simple under and over voltage detection system is all that's needed

Dave

Different strokes for different folks, and especially for clients who expect everything to run automatically without them having to manually tend to the batteries. For you experienced DIY guys, sure you can save a lot of $ by leaving out the bells & whistles.

However, I know from experience that human error is a common occurance at sea. I don't trust myself to never screw up, and certainly would not expect all of my clients to be perfect either.

I've done two circumnavigations, and over 100,000 miles of ocean racing & cruising. But perhaps you've done even more and are more dependable than me...

[T1 Terry]

Originally Posted by OceanPlanet

Different strokes for different folks, and especially for clients who expect everything to run automatically without them having to manually tend to the batteries. For you experienced DIY guys, sure you can save a lot of $ by leaving out the bells & whistles.

However, I know from experience that human error is a common occurance at sea. I don't trust myself to never screw up, and certainly would not expect all of my clients to be perfect either.

I've done two circumnavigations, and over 100,000 miles of ocean racing & cruising. But perhaps you've done even more and are more dependable than me...

I agree there, it's horses for courses all right. Don't think I'd be putting all my trust into a BMS system though, too many batteries have been killed due to their failures for me to trust one that far from help, what do you do when it craps itself, everything has a failure potential.
You may have lots of sailing experience but we are talking house batteies here, do you have any personal lithium house battery experience not using a BMS that you would like to share?

T1 Terry

[OceanPlanet]

Hmmm...don't know where to start. I grew up cruising with my dad, and lived aboard till the end of high school. Since then, my whole life has been in the marine business (see bruceschwab.com, and oceanplanet.org).

It probably isn't possible to race around the world (with with stopovers or nonstop, I've done both) without becoming a bit of an energy wonk. Of course lithium batteries for marine use didn't really exist in my ocean racing days (04/05 Vendee Globe). However, the importance of proper battery/systems maintenance and efficiency of fuel use/charging was pretty much ingrained into my DNA. Failure isn't an option when you can't stop without disqualification. For both of my RTW trips I used Geltech batteries, charged with a lot of solar panels and 130A x 24V alternator on the little 3GM engine. In the Vendee I used about 40gal of diesel in the 110 days. In those days that would considered pretty efficient...

Having seen more than enough ocean water, I returned to helping others on their boats in 2005. In the early part of 2009 I began offering simple LiFePO4 kits that used only balancing boards and basic monitoring. I figured that anyone used to looking after their own (lead) batteries would know not to run them too low (just as with lead) or overcharge them.

Unfortunately, even on professionally maintained yachts (or perhaps especially so) I learned that the inbred tendency to watch voltage as an indicator of SOC was hard for some users to kick. Even with a monitor and alarm there were lithium banks being run too low (sometimes killing cells), or overcharging faster then the shunting modules could burn off. Sure, users that really paid attention were ok however the failure rate (of the humans, mind you) was far too high.

Especially for a product that clients want to come with a warranty, and for marine systems installers to sell with any confidence. I soon connected with MIT graduate and avid sailor Alex MeVay of Genasun and became familiar with the BMS system he began developing in 2005-2006 for Li-Co systems he had been selling to racing yachts. He has been working with lithium for a long time, having been involved in the winning MIT solar race car team back in 1999.

With the combination of LiFePO4 cells, and Alex's BMS system I finally felt there was a safe, reliable lithium energy storage product. There are several details about the BMS configuration that I won't go into now, but it's the best thought-out system I've found so far. Many yachts are using this product now, from around the world racers to power-hungry yachts like the IPS56 above.

As a comparison in energy efficiency to my 40gal/110day on the Vendee, the IMOCA 60 "Mapfre" (ex-Foncia) using a 300Ah x 24V Genasun system, raced around the world in the Barcelona World Race in 94days, using only around 25gal...with NO solar. I installed that system myself in Spain. They would charge once roughly every 3rd day, for one hour (at about 300A x 24V). As T1 points out above, the charging efficiency of LiFePO4 is amazing.

It's great that smart guys can take the minimalistic approach, however that really won't work for professionally installed systems supplied with a warranty.

[bcn]

Originally Posted by OceanPlanet

Unfortunately, even on professionally maintained yachts (or perhaps especially so) I learned that the inbred tendency to watch voltage as an indicator of SOC was hard for some users to kick. Even with a monitor and alarm there were lithium banks being run too low (sometimes killing cells), or overcharging faster then the shunting modules could burn off. Sure, users that really paid attention were ok however the failure rate (of the humans, mind you) was far too high.

..........

It's great that smart guys can take the minimalistic approach, however that really won't work for professionally installed systems supplied with a warranty.

Interesting insights. How did the users achieve to ruin cells having alarms in place?

I understand that a set-up like that of Terry or the one of Paul/sytaniwha will not overcharge and to prevent from draining the housebank the under voltage alarm is in place.

bcn

[OceanPlanet]

Alarms only work if someone is there to hear them. Leave the lights on when off the boat for a long period, and....

You must be talking about LVC or HVC to prevent over or undercharge?