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

[deckofficer]

This will be my new source for any cell that isn't the 700 and 1000 a-hr cells that Balqon seem to have in stock. Lithium Prismatic Batteries

[roetter]

Originally Posted by folivier

Glad your order shipped so quick. Mind telling us how you placed the order?
Who you talked to? Or did it online?
Hopefully they are getting their order system working better now.

I was checking the shop page on the site when "Steve" came in with a message on the "Chat Line" to ask "how can I assist you". 10 minutes later and with two or 3 emails going back and forth with "James Li" for the credit card authorization it was all settled.

I have not opened the boxes yet, as they are with a friend in Annapolis. I am going over there next Monday.

[deckofficer]

Originally Posted by roetter

I was checking the shop page on the site when "Steve" came in with a message on the "Chat Line" to ask "how can I assist you". 10 minutes later and with two or 3 emails going back and forth with "James Li" for the credit card authorization it was all settled.

I have not opened the boxes yet, as they are with a friend in Annapolis. I am going over there next Monday.

You will like how Balqon packages the cells for shipment.

[d design]

i like the idea of being able to cook your food with electricity. these batteries can handle that much amps.

[deckofficer]

Originally Posted by d design

i like the idea of being able to cook your food with electricity. these batteries can handle that much amps.

You got that right. Before these cells and I was still using lead acid for off grid homes, it would be (24) 2 volt cells in series for the 48 VDC inverter to run heavy loads. Now with big enough cables these LiFePO4 cells would run a 5000 watt inverter on 12 volts. Got to love the sag-less voltage.

[KASHMIR]

I wonder if anybody has tried connecting the 17.5V from the solar panels direct to the LiFePO4 bank of cells? I would have thought that the BMS would cut the solar cell current when the battery terminal voltage reached the required 14.6 V or would it cook something before that happened?

Peter

[CharlieJ]

My design philosophy is to use the charging source organic control features to limit the charging voltage and to use the BMS HVC relay as the back-up.

[Maine Sail]

Originally Posted by CharlieJ

My design philosophy is to use the charging source organic control features to limit the charging voltage and to use the BMS HVC relay as the back-up.

Bingo! The BMS is your insurance policy not your regulator or controller.....

[markv]

I am just about to put in my order for a new Lagoon 450, taking delivery mid July. I've researched what I want to have for power etc and listed it here, be grateful for any info I might need to avoid costly mistakes..

I had a 440 for 7 years and for 4 years had 640W from 4 panels mounted in an array extending out from the bimini. After changing lights to LED, those panels started to become a lot more effective, and this time I want to avoid getting a large generator. We had a Fischer Panda and always had problems with it, so I can make do with a 2.4kw portable Yamaha. No intention to get AC this time, hardly used it last time.

I talked to Balqon and am ordering 2 x 9kw (700Ah x 4) units with built in BMS, and 1800W of solar panels (6 x 300W, 2x3 grid) extending off the bimini as before (4.7m wide by 2m back, of which 25cm will overlap the bimini top. I want to add 2 x Flexmax 80 solar controllers, each one connected to 3 of the solar panels. I am getting conflicting reports as to if I can connect both of these Outbacks to the same battery bank.
For battery space, I think there is room as the current battery space under the main bunk is 1.6m wide, and dimensions of the Balqons are 700mm x 650mm. Weight of each pack is about 90kg each.

I also want to change or add alternators on the engines, each to 150A or 200A and I will need to get a voltage regulator on each.

Part of the equipment supplied by Lagoon includes 60 and 40amp chargers i think supplied by mastervolt, don't have a choice on those, but will either add or replace them with Victron inverter charger 12/2500/200.

Still have to figure out the physical aspects of connecting all of this to the batteries, so any advice or even better, pictures, would be great. Will be doing some of it ourselves, and hoping there might still be some contractors around in late July/August in Les Sables d'Olonne, France to help. Or maybe they won't know LiOn tech, so learning as much as we can now before we get there.

[bill good]

Originally Posted by KASHMIR

I wonder if anybody has tried connecting the 17.5V from the solar panels direct to the LiFePO4 bank of cells? I would have thought that the BMS would cut the solar cell current when the battery terminal voltage reached the required 14.6 V or would it cook something before that happened?

Peter

Hi Peter I have thought it would be a good idea as the solar panel is already a constant current device & the old shunt regulator set to give the constant voltage part would do the job max kiss. A simple timer to time out the constant voltage requirement job done. Some form of BMS for the normal cell health should also be used.
It will be interesting to hear why this would not work & I think it would be better tham MTTP.

Regards Bill

[mrm]

Originally Posted by bill good

Hi Peter I have thought it would be a good idea as the solar panel is already a constant current device

This is wrong assumption, look at solar panel I/V curves to understand why.

& the old shunt regulator set to give the constant voltage part would do the job max kiss. A simple timer to time out the constant voltage requirement job done. Some form of BMS for the normal cell health should also be used.
It will be interesting to hear why this would not work & I think it would be better tham MTTP.

Regards Bill

In an emergency situation, like a total solar charge controller failure, this would work to get _some_ charge into batteries.

In a normal use scenario, this is entirely wrong for at least two reasons:
- extremely inefficient (see panel I/V curves again...),
- risk of cooking batteries.

Questions to help better understand why (EE 101 level).

- What is the output (delivered) power of a fully insolated, nominal 200W solar panel with disconnected outputs?

- What is the output (delivered) power of a fully insolated, nominal 200W solar panel with outputs short circuited?

[Maine Sail]

Originally Posted by KASHMIR

I wonder if anybody has tried connecting the 17.5V from the solar panels direct to the LiFePO4 bank of cells? I would have thought that the BMS would cut the solar cell current when the battery terminal voltage reached the required 14.6 V or would it cook something before that happened?

Peter

The "required" charge voltage for LFE is NOT 14.6V. If you want PROBLEMS and want to create a need for continual balancing, then sure, go to 14.6V. You will then have a need for balancing just as many BMS makers want you to have... Charge at a SAFE LFP voltage and you will likely have NO NEED to cell balance, the batteries will still get full and you won't run the risks associated with "automatic cell balancing"....

The Chinese put this stuff in the manuals so that they can sell more product as it now appears to be DROP IN for lead acid.... Ask the GEL battery makers how this worked out for them?? They are now eating the lunch of AGM batteries even when GEL batteries are far superior in terms of cycle life. GEL got a bad rap because some manufacturers got greedy and tried to market them as "drop in" for typical flooded battery charging voltages. Most of the early GELS were DESTROYED and the GEL industry got a black eye. When charged at 14.1V they can go 15 years +, when charged at 14.4V+ they last a year or less..... The Chinese just want to sell batteries and they will tell you whatever you want to hear.

Even companies like Lithionics used to suggest 14.6V, but they learned the HARD WAY. They now suggest 14.0V of you don't use their brand BMS and max 14.2V if using their BMS. Genasun, even with their incredible BMS, max charges at 14.2V... Jack Rickard LFP Pioneer suggests also a max charge voltage of 14.2V with lower even better.

It is NOT drop in and anything above 14.2V is an UNWISE charging voltage for fractional "C" use..

MAX CHARGE VOLTAGE FOR LFE = 14.2V

BETTER MAX VOLTAGE FOR LFE = 14.0V

SAFEST CHARGE VOLTAGE FOR LFE / DIY 13.8V-13.9V


Any GOOD LFE BMS will HV CUT charging at 14.2V or lower. Any BMS cutting higher than that is doing so to keep themselves in the "cell balancing" business. These cells are FULL at below 14.0V.....

The Clean Power Auto House Power BMS is the best value for a frac "C" BMS. Why Mickey Mouse it and risk 3k worth of cells when a well designed BMS can be had for as little as $126.00 (plus your choice of relays/contactors).....????

House Power BMS Board $75.00

House Power BMS Cell Modules $12.75 Each

The HPBMS does SMART cell balancing meaning if it is wired and used PROPERLY you can't physically shunt balance without first MANUALLY disabling HVC because HVC occurs well before cell balancing......

Cell balancing IMHO should be treated just like equalizing flooded batteries, attended, manual and done at the LOWEST possible current.

I now have 326 cycles, most to 80% DOD, and have never had to re-balance, at all.. Max charge voltage on this Winston LFP bank is 13.9V for 30 minutes then it drops to 13.8V..... This 400Ah bank is still delivering 425Ah at a .25C load and has lost ZERO capacity... 14.6V....????? No need!

[CharlieJ]

Hear, here!!!

This is extremely sound advice. And you got it for free.

[hellosailor]

So, Maine, tell us how you really feel.(G)

Hucksterism would of course explain the contradictory instructions and conflicting recommendations from so many sources in the "lithium" battery business.

Or, it could just be the unfortunate result of the incredibly complicated need to translate the correct voltage levels from Mandarin(and sometimes more obscure dialects) into Arabic (for the numbers part) and then again into English for those damned hairy barbarians, ergh, Yankee customers. So many opportunities for a sad translation error to accumulate!

(WEG)

[Maine Sail]

Originally Posted by hellosailor

So, Maine, tell us how you really feel.(G)

Hucksterism would of course explain the contradictory instructions and conflicting recommendations from so many sources in the "lithium" battery business.

Or, it could just be the unfortunate result of the incredibly complicated need to translate the correct voltage levels from Mandarin(and sometimes more obscure dialects) into Arabic (for the numbers part) and then again into English for those damned hairy barbarians, ergh, Yankee customers. So many opportunities for a sad translation error to accumulate!

(WEG)

I suspect a lot of the problem comes from how the Chinese expect these batteries to be charged and the reality of the chargers it the real market and what people think the manuals mean. I just forget the manuals and proceed on to do physical testing to find out what is safe, what is full, and what is not safe.

THEY EXPECT: Bring bank to 14.6V - IMMEDIATELY STOP/TURN OFF CHARGING.

The reality is nothing is set up that way in the marine market so we:

REAL WORLD: Charge to 13.8V - 14.0V - HOLD CV UNTIL TAIL CURRENT IS 0.025C - 0.05C then DROP to a lower "FLOAT" or really an OFF voltage.

14.6V puts these batteries well within the upper knee and they DO NOT like to be held in the upper knee....

AVOID THE KNEES and you will have a simple, effective and long lasting bank that stays in balance for a very, very long time.. Try to cut corners and use lead acid charging profiles and, well, you get what you get........