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

[mbianka]

Originally Posted by deckofficer

Close to 100% DOD, but even at 80%, that would be a lot of nm per charge. You probably don't have room for (16) of those 700 a-hr cells. The way you treat your AGMs, I can see why you get such good cycle/storage life from them.

Well, that's the plan and so far so good. Plus it's easier to monitor and charge four individual 8A4D AGM's than 16 LiFePO4'a at this point. Though I may try LIth batteries first for the house bank when those two group 27 Gels go bye bye. I bought those batteries at the same time I bought the AGM's for the propulsion bank. They are still working well six years on too. But, like the EP bank they get charged early and often when I use the Honda 2000 to charge the EP bank and have 150 watts of solar helping them along too.

[diugo]

Originally Posted by deckofficer

Not that old, just was into electronics as a young kid. My first HAM transmitter was a Knight-Kit T-60 AM CW in 1963. I did build a Knight-Kit tube tester. Heath Kits were too expensive for me.

In the 70s Radio Shack had these various red "perfbox" kits which were pretty fun to build. My fave tho was the solderless 100 circuit experiment kit, with all the springs and jumper wires. I think I too shyed away from the Heath kits because of price.

Only got into ham radio in order to make free "cellular" phone calls using the autopatch. In case everyone hasn't noticed it yet, I am a major penny pincher

[deckofficer]

Originally Posted by mbianka

Well, that's the plan and so far so good. Plus it's easier to monitor and charge four individual 8A4D AGM's than 16 LiFePO4'a at this point. Though I may try LIth batteries first for the house bank when those two group 27 Gels go bye bye. I bought those batteries at the same time I bought the AGM's for the propulsion bank. They are still working well six years on too. But, like the EP bank they get charged early and often when I use the Honda 2000 to charge the EP bank and have 150 watts of solar helping them along too.

When you do the house bank, here is the size of small 100 a-hr @ 30 lbs.

[Cotemar]

1) Are these batteries any good for a boat house bank?

2) If they are 12 volt already you would not have to worry about balancing them?

3) With an operating voltage of 11 to 16 volts, you would not have to worry about hitting the top or bottom?

Balqon - Advanced Transportation Solution

[deckofficer]

Originally Posted by diugo

In the 70s Radio Shack had these various red "perfbox" kits which were pretty fun to build. My fave tho was the solderless 100 circuit experiment kit, with all the springs and jumper wires. I think I too shyed away from the Heath kits because of price.

Only got into ham radio in order to make free "cellular" phone calls using the autopatch. In case everyone hasn't noticed it yet, I am a major penny pincher

I too was an early adopter using the repeater's autopatch. I had my handheld, small "cellular" phone 20 years before the Motorola Brick was introduced. It was impressive since there was no such thing as a cell phone back then.

[deckofficer]

Originally Posted by Cotemar

1) Are these batteries any good for a boat house bank?

2) If they are 12 volt already you would not have to worry about balancing them?

3) With an operating voltage of 11 to 16 volts, you would not have to worry about hitting the top or bottom?

Balqon - Advanced Transportation Solution

I believe they use (4) of the 90 a-hr cells packaged as a single 12 volt battery. They don't say anything about a BMS and for some reason they de-rate the 90 a-hr cells from <3C to <1C and cycle life from 2000 cycles to 1750.

[Cotemar]

Originally Posted by deckofficer

I believe they use (4) of the 90 a-hr cells packaged as a single 12 volt battery. They don't say anything about a BMS and for some reason they de-rate the 90 a-hr cells from <3C to <1C and cycle life from 2000 cycles to 1750.

What does "Max Discharge Current : < 3CA" mean?

[deckofficer]

Originally Posted by Cotemar

What does "Max Discharge Current : < 3CA" mean?

If the cell is a 90 a-hr cell, they recommend that you don't pull more than 270 amps, i.e. 3C. On Maine Sail's new house bank at 400 a-hr, that would be 1,200 amps.

[Cotemar]

Originally Posted by deckofficer

If the cell is a 90 a-hr cell, they recommend that you don't pull more than 270 amps, i.e. 3C. On Maine Sail's new house bank at 400 a-hr, that would be 1,200 amps.

So does "Max Discharge Current : < 1CA" mean 90 amps ?

[mcarling]

Originally Posted by deckofficer

If the cell is a 90 a-hr cell, they recommend that you don't pull more than 270 amps, i.e. 3C. On Maine Sail's new house bank at 400 a-hr, that would be 1,200 amps.

Yes, but lower discharge rates will increase LiFePO4 battery life. 0.5C or less is optimal for long battery life.

Originally Posted by Cotemar

So does "Max Discharge Current : < 1CA" mean 90 amps ?

For a 90AH battery, yes.

[deckofficer]

Originally Posted by Cotemar

So does "Max Discharge Current : < 1CA" mean 90 amps ?

That is a cont. rating. The single cell 90 a-hr is <3CA but pulse rating is 20CA, or 1800 amps pulse.
Winston Battery Limited

[noelex 77]

The "12v" lithium batteries do not seem to me to be as good an option as the separate cells. The cost is very similar and while the wiring is easier pre made jumpers make connection easy.
The big drawback of the 12v cells is that is that it is impossible to balance the cells. There is a lot of debate over the need to balance the cells. I have only used smaller lithium batteries, but my experience has been that even with modest charging and discharging rates they go out of balance reasonably quickly.

To loose the ability to balance the cells is a significant drawback even if you feel it only needs checking infrequently.

I may be cynical, but I think these 12v batteries have been produced because consumers want a direct replacement for their 12v LA batteries and despite the technical compromises associated with doing this the manufactures are bowing to consumer demand.

My recommendation would be to buy the separate equivalent cells in preference.

[deckofficer]

Originally Posted by noelex 77

The "12v" lithium batteries do not seem to me to be as good an option as the separate cells. The cost is very similar and while the wiring is easier pre made jumpers make connection easy.
The big drawback of the 12v cells is that is that it is impossible to balance the cells. There is a lot of debate over the need to balance the cells. I have only used smaller lithium batteries, but my experience has been that even with modest charging and discharging rates they go out of balance reasonably quickly.

To loose the ability to balance the cells is a significant drawback even if you feel it only needs checking infrequently.

I may be cynical, but I think these 12v batteries have been produced because consumers want a direct replacement for their 12v LA batteries and despite the technical compromises associated with doing this the manufactures are bowing to consumer demand.

My recommendation would be to buy the separate equivalent cells in preference.

I agree.

[senormechanico]

+1 what Noelex said.
Plug and play isn't always the best answer to a need.

[bill good]

They are made from cells with following serial numbers & are very close in specs however the tops come off to expose terminals & if you want you can fit BMS. As starting batteries with very little power used during start they are back up in less than a few mins. I am happy with the 40 Ah sold as a complete unit it is 4 standard cells strapped within an external case. The other engine has a made up 24 AH round cells with shunt BMS. I try to remember to parallel them for starts but sometimes forget to do so. I will have to look at the issue of float charge voltages now that has been raised. 6mths & so far all good.

Regards Bill