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

[diugo]

I also like Balqon's math when it comes to their clearance prices.

[durundal]

Originally Posted by Maine Sail

A puzzle..

Ok so I also have a "reserve bank" that is LA that I will need to charge. Problem is that I am charging my LiFePO4 bank to 13.7V (3.43VPC) then dropping back to 13.4V or 3.35VPC in order to discontinue charging when the bank is full (solar and alt reg are programmed this way).

I had planned to use a new Sterling Power product to boost the ouptut voltage to the reserve battery but the product is not yet shipping and I just found out the "on" voltage is fixed and can't be changed (I had been lead to believe by Charlie that the input trigger voltage would be adjustable.

Obviously I don't want to have this device "on" at 13V as it will always be sitting there on as my bank rests higher than that and I would prefer something that can "boost" to my reserve bank.. I suppose I could just leave it "on" but I would still want to hit my reserve battery with absorption every now and then. As it sits now I have a Balmar Duo Charge that I have adjusted the "on" voltage but this device only follows the voltage of the house bank and will only pump out the 13.7V the house bank will be charged to..

So you have these cases?

Vlith < 13.35 --> charge to 13.7V
Vlith > 13.35 --> use charging wattage to divert to lead acid reserve bank

But your lead acid controller needs some input voltage greater than 13.7V to be able to charge the lead acid properly? You might want to look into charge-logic.com's selection of step up dc/dc converters that would be placed in line with the Balmar, these would let you take the 13.35-13.7V of the lithium bank and send that out at something higher to the lead acid controller. It looks like they have some nice die cast aluminum potted versions of various flavors, or unsealed but more adjustable versions. Identical looking enclosures appear to be on amazon and ebay as well, I'm assuming they are the china-based OEM.

I found them while looking for regulators for small outboards, it turns out that they just have rectifiers until you get to serious horsepower, and that would not be a good condition to have hooked up to a solar-topped-off lithium bank... still haven't found the right output voltage in a sealed unit for that question mark yet...

Andy

[ebaugh]

Originally Posted by Maine Sail

A puzzle..

Ok so I also have a "reserve bank" that is LA that I will need to charge. Problem is that I am charging my LiFePO4 bank to 13.7V (3.43VPC) then dropping back to 13.4V or 3.35VPC in order to discontinue charging when the bank is full (solar and alt reg are programmed this way).

I had planned to use a new Sterling Power product to boost the ouptut voltage to the reserve battery but the product is not yet shipping and I just found out the "on" voltage is fixed and can't be changed (I had been lead to believe by Charlie that the input trigger voltage would be adjustable.

Obviously I don't want to have this device "on" at 13V as it will always be sitting there on as my bank rests higher than that and I would prefer something that can "boost" to my reserve bank.. I suppose I could just leave it "on" but I would still want to hit my reserve battery with absorption every now and then. As it sits now I have a Balmar Duo Charge that I have adjusted the "on" voltage but this device only follows the voltage of the house bank and will only pump out the 13.7V the house bank will be charged to..

I have some creative ideas of how to accomplish this but I am curious as to the groups thoughts on how best to deal with this puzzle.

I have now done over 30 cycles on my bank using the voltage parameters I have chosen and find them to be working perfectly. I gave up a small amount of top end capacity, perhaps 10 Ah's at best, but the cells are still in perfect balance and I am well away from the knee's..

My solution just ties them together, the LA/AGM float just fine on routine LFP operating voltages. I have only been below 12.8V once in the last few months at anchor. But I have 2 other small batteries to start my gensets in the unlikely event I screw up the combined house/engine start bank.

In your case, assuming there is no other "backup", I'm thinking a DC to DC Echo charger is your best alternative? It can be programmed with the correct LA charge profile, but never discharge to the LFP bank, providing a reserve. You could manually switch it in and out, but something has to provide the energy to keep the LA at full charge.

I've seen a 15A echo charger in my readings that I think would do this, but can't remember the specifics. If you don't know of the product, let me know and I will look for a specific suggestion.

Bob

[Maine Sail]

Originally Posted by ebaugh

My solution just ties them together, the LA/AGM float just fine on routine LFP operating voltages. I have only been below 12.8V once in the last few months at anchor. But I have 2 other small batteries to start my gensets in the unlikely event I screw up the combined house/engine start bank.

In your case, assuming there is no other "backup", I'm thinking a DC to DC Echo charger is your best alternative? It can be programmed with the correct LA charge profile, but never discharge to the LFP bank, providing a reserve. You could manually switch it in and out, but something has to provide the energy to keep the LA at full charge.

I've seen a 15A echo charger in my readings that I think would do this, but can't remember the specifics. If you don't know of the product, let me know and I will look for a specific suggestion.

Bob

Problem is I am only charging my Li bank to 13.7V. Every now & then my reserve battery will need some absorption voltage.

The Echo is not programmable and turns on at 13V thus would be "on" all the time. The Duo Charger does have a programmable "on" voltage though the manual does not explain it well. The Duo will work but I will then lack a good push to 14.4V+ on my LA batt.... I suppose for the cost of the LA battery and what it will cost me to backyard engineer a DC to DC boost charger I can just accept replacing it every 3-4 years. I thought the Sterling was going to be my ticket but it is not to be...

The problem is I have piles of equipment around, Echo's, Duo's, Sterling B2B's, ACR's, solar controllers etc. etc.. but none fit what I need to do. I even thought of inserting a boost solar controller off my Duo Charger but I don't have one kicking around that is 30A rated and the Duo can supply up to 30A of current.. The Genasun boost controllers are only 8A rated... Granted my Duo will likely never put out more than 8-10A but I hate to risk it...

I will probably just do an A/B switch on my solar panel and feed two separate controllers. One for the Li bank and one for the LA bank. I'll only need to hit the LA battery once every three to four weeks for a couple of days max. Sharing one array feeding two separate controllers via a selectable A/B switch will work fine I just wanted something more "automatic"...

[dansken]

I plan to use one of these for similar problem http://www.victronenergy.com/upload/...3%20-%20EN.pdf

[ebaugh]

Originally Posted by Maine Sail

Problem is I am only charging my Li bank to 13.7V. Every now & then my reserve battery will need some absorption voltage.

The Echo is not programmable and turns on at 13V thus would be "on" all the time. The Duo Charger does have a programmable "on" voltage though the manual does not explain it well. The Duo will work but I will then lack a good push to 14.4V+ on my LA batt.... I suppose for the cost of the LA battery and what it will cost me to backyard engineer a DC to DC boost charger I can just accept replacing it every 3-4 years. I thought the Sterling was going to be my ticket but it is not to be...

The problem is I have piles of equipment around, Echo's, Duo's, Sterling B2B's, ACR's, solar controllers etc. etc.. but none fit what I need to do. I even thought of inserting a boost solar controller off my Duo Charger but I don't have one kicking around that is 30A rated and the Duo can supply up to 30A of current.. The Genasun boost controllers are only 8A rated... Granted my Duo will likely never put out more than 8-10A but I hate to risk it...

I will probably just do an A/B switch on my solar panel and feed two separate controllers. One for the Li bank and one for the LA bank. I'll only need to hit the LA battery once every three to four weeks for a couple of days max. Sharing one array feeding two separate controllers via a selectable A/B switch will work fine I just wanted something more "automatic"...

It's a problem that has no "automatic" solution I know of. This is an example DC-DC converter I was thinking of:

http://images.mastervolt.nl/files/magic080311.pdf

But you could also use a regular traditional AC powered trickle charger as well, assuming you have an inverter to power it. Or even better shore power on a regular basis.

You probably don't need much amperage charge, once charged, it should take little current to push the LA to 14.4 for awhile to top off. Heck you could make an AC powered one from Radio Shack components for manual use.

Either the DC to DC or AC charger has losses in conversion efficiency. No device has the programming to cycle automatically that I know of...

But the topping charge is not required often. Perhaps a battery combiner based on the LFP voltage as a discharge safe guard, combined with a good smart "AC Battery Tender" that could be run on shore power or at the mooring occasionally. Wouldn't once every couple of months suffice if the LFP kept the float charge?

None of these are different, just optional variations on using your solar system. I measured something like 250mA to keep my 2 AGM golf carts floated at 13.2V. How much would it take to recharge to 14.4 for how long every 2-3 weeks? I don't know, but it has to come from somewhere....too bad LA needs CV to hold a charge, but that's a fact...

Bob

[deckofficer]

Reuben shared a picture of his 48 volt 1000 a-hr bank on the Trawler Forum. You just have to love those big yellow cells. I am a little concerned at how close the terminals of the opposing cells are to each other but since they aren't fully hooked up there might be some sort of divider that is placed between them.

[senormechanico]

If there isn't some kind of divider, we'll certainly hear about it one way or another.

[FlyingCloud1937]

Originally Posted by deckofficer

Reuben shared a picture of his 48 volt 1000 a-hr bank on the Trawler Forum. You just have to love those big yellow cells. I am a little concerned at how close the terminals of the opposing cells are to each other but since they aren't fully hooked up there might be some sort of divider that is placed between them.

It appears That all of the cell connects are either alum, or a tinned alum/copper???

What we can also see is a multiple of post on each cell...looks like three??????

Maybe it's just a bad photo!

Lloyd

Lucy, ya got some splainin to do

[deckofficer]

The 1000 a-hr cells have (6) terminals per cell. Reuben said he has installed rubber mats between the packs terminal side and a mat on top to protect should a tool get dropped on them. I think the bars are copper.

[FlyingCloud1937]

Originally Posted by deckofficer

The 1000 a-hr cells have (6) terminals per cell. Reuben said he has installed rubber mats between the packs terminal side and a mat on top to protect should a tool get dropped on them. I think the bars are copper.

1234.... we can count,

but it appears that the post are all of alum or zinc-coated.

If all alum.. then they are likely old cells, or

the alum binder issue isn't a problem/or is it???

Lloyd

[FlyingCloud1937]

Originally Posted by deckofficer

The 1000 a-hr cells have (6) terminals per cell. Reuben said he has installed rubber mats between the packs terminal side and a mat on top to protect should a tool get dropped on them. I think the bars are copper.

Not to mention that's a pretty big pack with no binding, or any fire control safe-guards.

It appears to have a BMS, but what about the ultimate melt-down....It seems the wood surround only adds fuel to the fire.

Or is she a brazen-hussy, because she can't fail?


lloyd

[downunder]

Originally Posted by FlyingCloud1937

1234.... we can count,

but it appears that the post are all of alum or zinc-coated.

If all alum.. then they are likely old cells, or

the alum binder issue isn't a problem/or is it???

Lloyd

Any positive recommendations/suggestions from your vast experience??????????????????

[diugo]

It is notable that the 1000AHC model appears to use aluminum for all the posts, including the negative ones---which are traditionally copper (since they connect to the copper foils inside the cell).

However, this is not necessarily a harbinger of doom. These are large, expensive, modern Winston cells, not pre-2010 Thunderskys or knockoffs. And galvanic corrosion can be prevented in a number of ways. Has anyone experienced an "ultimate melt-down" with this model before?

Has our self-declared Ralph Nader actually dissected one before hastily suggesting it unsafe at any speed?

[Maine Sail]

Another interesting data point:

Today the bank is being physically installed into the boat so yesterday I performed the same exact discharge/capacity test that I had previously conducted using the exact same parameters except for the charging voltage I charged the pack to..

The only difference between the two capacity tests was this time my bank was only charged to 13.7V or 3.425VPC. I stopped the test at 400Ah's removed from a 400Ah rated battery bank. Last time I terminated the test at 425Ah's. I should have pushed it further but simply ran out of time and was literally standing there waiting for it to hit 400Ah and still be in a "safe" voltage range. I shut it down before low voltage even became an issue.

#1 Has anyone else done the same or similar and measured capacity while charging to a voltage only slightly above "resting" voltage...?

#2 Why if I can still get 400Ah's out of a 400Ah battery bank would I want to charge it any higher than 13.7V other than to do an occasional "top balance".....?

It seems to me from all my testing of this bank over the winter that you can get damn near the full capacity back into the cells (n=1) with a lower charging voltage. This means I stay well away from the "knees" which we know to be an area where the voltage can hockey stick...

I also just finished a week's worth of testing of my solar controller to make sure its set points performed as I want them to. This Aurinco is not my first choice in a controller but Rogue is still not shipping their new controllers and Genasun has not yet added customizable user settings via a computer.

With no disrespect to Genausn (I love their controllers) I was not about to pay $50.00 per adjustment, plus shipping, to have my controller re-programmed. As it sits now that was a good move as my packs charging voltage has changed a number of times over the winter or about $200.00 worth of re-programming.......

The Balmar reg has also been programmed but not yet "tested" I will need to do that on the boat as I did not feel like setting up a test rig on my bench..

I still plan to program my battery monitor for 375Ah's and not 400Ah's as this will keep my discharge floor a little higher. 375Ah's, with 80% of the capacity fully usable, is way more than we need.

Heck we got 7 years out of a 375Ah Wal*Mart group 31 battery bank with only 35% of the capacity "usable" (50% to 85% SOC usable). Those batteries will easily go another year or two and are still testing very, very well. This will be cake walk for the LiFePO4 bank...

So, has anyone out there other than myself, done a controlled capacity test on their Winston bank when charging to a voltage between 13.6V and 14.0V for a 12V nominal bank..? Is what I am seeing and recording normal or is my pack just larger in capacity than the actual "rating"...