Lithium batteries from Balgon

[whatsnext]

I have seen reference from other RV fulltimers about using the Balgon 700Ah lithium batt pack for $840 (Technomadia, WheelingIt).

My question is this:

How can an RV system utilize this if the rated voltage for the pack is 2.8V - 4.0V?

 

I am not at all a techie but I thought you had to have a "sum 12V system" for RV's.

Thanks to all for clarifying this.

[Bill Joyce]

You wire multiple cells in series to get to 12 volts. Many RVs come with 6 volt golf cart batteries series wired in pairs for 12 volts.

 

But Balqon (notice it is a 'Q', not a 'G') lists 12 volt under "Battery Banks", http://www.balqon.com/lithium-batteries/, already put together for you.

[Jack Mayer]

Yes, HERE is a nice one for you. Pretty much turnkey.

 

OR, if that is too little capacity, try THIS ONE. It's footprint is only 27x24x14. 15 kwhr.

[reed and elaine]

As Bill noted, the item referenced by What's Next is a single LFP cell, and not a battery bank.

 

Balqon prices are the best I have seen. The 9.6 kW-hr Balqon is an excellent price but it does weight about 250#. Admittedly our battery bank of 4 x 2.4 kW-hr (180 amp-hr at 12 V nominal (13.5 V actual at charge) weighs the same but the individual batteries (4 x 180 amp-hr 3.3 V or whatever CALB cells are rated) are only 50# or so each and this makes for easier handling and simpler packaging in our front bay.

 

I have yet to find an LFP user on any forum that is not satisfied with them (other than price). The only discussion/argument seems to been whether to utilize a battery management system or hand balancing. "Discussions" can be vociferous. Prices are going down and the technology is advancing each year.

Reed and Elaine

[reed and elaine]

400# is fairly heavy for us but nothing for a large motorhome. I would consider this Balqonx2 if we were building a solar home.

[whatsnext]

You wire multiple cells in series to get to 12 volts. Many RVs come with 6 volt golf cart batteries series wired in pairs for 12 volts.

 

But Balqon (notice it is a 'Q', not a 'G') lists 12 volt under "Battery Banks", http://www.balqon.com/lithium-batteries/, already put together for you.

Thanks Bill for the "q" correction. I thought you had to wire in series to get to 12v. Just wanted to make sure I was not missing something.

Jack- I saw the 9Kwh pack....maybe if I get on the "nice" list, Santa may make it a Christmas present one year! LOL

[sushidog]

Below is some research I did for a post on another forum. What surprises me is that most Lithium advocates always use the 80% discharge number (I guess because it can be done) but if they are only discharged down to 70% they have 50% more life, making their cost per cycle/ah the same as the best flooded lead acids. The only hurdle to overcome is their initial cost - which may be coming down soon with the advent of graphene batteries.

 

"I will need to build a 48v system to run the heat pump, which is a 48v DC appliance, for which I need 200 usable ah @48v.
If I use 8 flooded lead acid S-550s in series, for $340 ea = $2,720 They are rated at 428ah at 6 volts.
If discharged to 50% for a 1,400 cycle life they will yield 214 usable ah at a cost/cycle/ah of $0.009
If discharged to 70% for a 1,000 cycle life they will yield 300 usable ah at a cost/cycle/ah of $0.009

If instead I chose to use 16 - 400ah 3v lithuims from Balqon in series for $490 ea, they will cost $7,840
If discharged to 80% for a 2,000 cycle life they will yield 320 usable ah at a cost/cycle/ah of $0.012
If discharged to 70% for a 3,000 cycle life they will yield 280 usable ah at a cost/cycle/ah of $0.009 - the same cost as lead acids

The only problem is they cost over $5,000 more initially though they roughly equal the cost of the best FLAs (less than 1/2 the cost of AGMs) in the long run.
They only weigh 30lbs ea x 16 = 480lbs vs 132lbs ea x 8 = 1056lbs for the S-550s saving 576lbs.
If one considers the time value of money a 20 year payback and I'd have to borrow the $5,000 (and pay interest on this amount) they would cost a little more than FLAs even in the long run. But this money buys 576lbs of additional cargo carrying capacity, a little more available space, zero maintenance (a biggie), and the advantages of low internal resistance (faster charge and discharge without heat or invoking Mr. Peukert.)"

 

Chip

[DuffMan]

What happens to Lithium Batteries if they are discharged to -0- Volts - i.e. months of storage and forget to turn something off?

 

I have a Win 8 Lenovo Laptop that this happened to - Non removable battery and nothing I do can get it to power on/ boot. In checking around - this is a common complaint within the QuadCopter / RC flying community. Lithium batteries are not throw in the drawer and forget power sources. If they get below ~2.7 volts they become very expensive bricks. There are some tricks to shock them back but it is very iffy and never get back to full capacity.

 

Is this a problem with these Lithium Auto batteries?

[Jim & Wilma]

Is this a problem with these Lithium Auto batteries?

Yes, a Lithium battery system needs to have under voltage monitoring with a relay that can disconnect power when the limit is reached. This serves as protection, say if you lose power while you're gone and you have DC loads running. The Balqon battery pack referenced above comes with an integrated Battery Management System (BMS) and a contactor (high power relay) to do just that. The BMS also performs other functions like cell balancing and over voltage alarm.

[DuffMan]

So once the relay isolates the battery due to low voltage, how much time do I have before I am left with an expensive brick from internal discharging? Days? Weeks? Months? Years??

[Vladimir]

I am NOT knowledgeable about these batteries.

 

However, we do own two electric bicycles with lithium batteries. The instructions with the bicycles said to always disconnect the batteries after charging. However, that meant IF we did not use the bikes for a month or two the batteries ended up discharging. We try to recharge them every two weeks. I probably should have bought a timer to keep them charged. We did manage to "wake" up the batteries three or four times. It is a process.

 

After a year we have had TWO sets fail due to the self-discharge issue. The first time we got a brand new bike from Trek. Still not sure what we can do with the second battery. They are expensive to replace in the range of 800 dollars.

 

Trek has quit making electric bikes. I suspect it was all related to the battery issue.

[sushidog]

If disconnected from a load the self-discharge rate of a LiFePo4 battery is 1/2 the rate of a lead acid, or around 2-3% a month, so depending on the amount of charge left in the battery (say you disconnect at 75% discharge, you should have at least a couple months before recharging is needed.) Lithium's don't need to be recharged right away like lead acids do to avoid sulfation.

 

Here's a couple links that shows a good comparison between the performance characteristics of different battery types: http://www.mpoweruk.com/performance.htm http://www.mpoweruk.com/lithium_failures.htm#lifetime

 

Chip

[DuffMan]

Problem with using them with an RV being put into storage is, what if I leave my lights on or other background load and it discharges to say10% after a couple days before the battery auto internal disconnects to protect itself. If I am not coming back for a couple months, I bet I will return to an $800.00 useless brick!

[sushidog]

Well, that could happen if the auto disconnect waits till the battery is at 90% discharge.

 

I guess you need the answers to 2 questions.

1. What is the battery low voltage disconnect set at?

2. Is it possible to change the setting to at least 75-80%?

 

Chip

[DuffMan]

Well, that could happen if the auto disconnect waits till the battery is at 90% discharge.

 

I guess you need the answers to 2 questions.

1. What is the battery low voltage disconnect set at?

2. Is it possible to change the setting to at least 75-80%?

 

Chip

 

Only the Mfgr of the battery pack can say. Look at post #9. Those Battery Packs come with their own Battery Management System built in (Lithium packs are a bunch oh small 3 volt cells interconnected to a large sa 12 Volt battery pack. The individual internal batteries are not as simple as others to interconnect - the battery pack has its own integrated controller in the Battery Pack to handle shutdown and cell balancing.)

 

The biggie question is when the battery does go into self protection mode, how much time do you have to get power to it before it becomes unusable and unrecoverable. (I have heard it is a matter of 3-4 weeks after which the pack is unrecoverable.)

 

This must be a dirty little secret as even the Battery Mfgrs website does not discuss it. They want to assume you always have the pack connected to periodic (weekly) charging.

[reed and elaine]

Laptop and electric vehicle batteries are usually Lithium Cobalt which have a much greater energy density but are a lot trickier to maintain.

 

Wheeling it, Gone with Wynnes, and Technomadia are fairly extensive bloggers and it might be good to read them for their anecdotal information.

 

What I have read is that going to 50% DOD fairly often is a good value to work with as your battery bank will last far longer. We have gone to 70% DOD several times when running the Dometic air conditioner and several times when parked in heavy shade for a week. You can drop to 80% fairly often and Liberty Coaches has supposedly done 80% DOD duty cycles for 3000 repetitions. Liberty Coaches probably considers their work to be "confidential" and I have read no reports by them giving particulars.

 

Reed and Elaine

[Daveh]

I don't see why you are aiming that at LFAs, it would eventually kill LA's also. The manufacturers store lifepo4 at approx 50% discharge. That is usually how you would get them shipped to you. The do better stored at a lower capacity.They do not self discharge nearly as fast as LA's. How long they would last after the Lvoltage cutoff went off would depends in other factors but generally if they have a 20-30 % SOC left they will last a long time. Remember you can set your own voltage cutoff points with other equipment. So just make sure itis set higher before you go. Or disconnect them completly.

[wa_desert_rat]

I got to thinking about Prius' lithium battery bank and whether those have had to be replaced yet. Sure enough, there are businesses focused on replacing the batteries in hybrid (and ev) vehicles.

 

Here is an ad for one of them: http://losangeles.craigslist.org/wst/pts/4841399663.html

 

Note the pricing. I wonder if those guys would be able to provide better pricing for RVs and get better performance.

 

WDR

[sushidog]

Since 2004, a Prius battery has 201.6 volts and 6.5ah. However it is made up of 28 modules (batteries) producing 7.2 volts ea. If wired in 4 parallel banks of 7 modules each they would produce a more usable 50.4 volts (nominally 48 volts). for 1310 watt hours or about 20 usable ah - not much. Since I am looking for 200 usable ah @48v I would need 10 of these! How much would 10 used Prius batteries cost?

 

320 usable ah of brand new Balqon batteries (50% more power) would cost $7,840 - a better deal than 15 rebuilt Prius batteries at $650 each = $9,750 - Plus I'm sure you have to have 15 rebuildable cores, and how much will that set you back? And how long will these rebuilt batteries last? For ones with only a 2 yr. warranty you'd have to spend twice as much, plus the cores.

 

Great idea, thinking outside the battery box, but impractical this time.

 

Incidentally, looking at the battery specs, it's amazing the Prius's can do as well as they do with only a 1.3Kwh battery bank. I would have thought it would need to be several times that size.

 

Doing more research I discovered the Prius does not use a Lithium battery but a nickel metal hydride battery which can't be cycled as deeply as a lithium, so it has even less available ah than I stated, making it a very poor choice indeed.

 

Chip

[reed and elaine]

I think the Tesla has around 80 to 100 kW-hours. Tried googling this and did not get any direct answers.

Reed and Elaine

[Dick N]

If disconnected from a load the self-discharge rate of a LiFePo4 battery is 1/2 the rate of a lead acid, or around 2-3% a month, so depending on the amount of charge left in the battery (say you disconnect at 75% discharge, you should have at least a couple months before recharging is needed.) Lithium's don't need to be recharged right away like lead acids do to avoid sulfation.

 

Here's a couple links that shows a good comparison between the performance characteristics of different battery types: http://www.mpoweruk.com/performance.htm http://www.mpoweruk.com/lithium_failures.htm#lifetime

 

Chip

I have a 30 cell lithium battery pack which has been sitting on the shelf for well over a year now. Each cell read 3.131v initially and today still reads 3.05. Self discharge has been almost nil. The pack is stored in a climate controlled environment and I use a Fluke voltmeter to measure voltage. I bottom balanced all 30 cells and slowly brought them all up to 3.131 for storage. And yes, I do eventually plan to use this pack.