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

[mcarling]

"Is it bad to have the LiFePO4 charge through the AGM start battery? The alternator will be running, but is there any risk of an empty LiFePO4 bank drawing the entire ~100A that the alternator can output and then also draw down the AGM? I'm sure it'll be fine, but thought I'd ask"

Yes, it is bad to charge the LiFePO4 through the AGM start battery. Yes, an empty 200AH LiFePO4 bank can draw the entire ~100A that the alternator can output and then also draw down the AGM. Depending on the relative charge of each bank, it might even melt cables if not properly fused. If properly fused, you'll probably blow a fuse if the AGM bank is fully charged. Connecting LiFePO4 batteries in parallel with any variety of lead-acid batteries should be avoided.

[SailRedemption]

Hello friends,

I have been in the process of installing my lithium bank on my boat. I am currently at a standstill.

I am having trouble trying to figure out how and where to wire my battery switches on my batteries. I started to wire the on/off switch immediately after the main contactor and from there to the main + bus. Then I had an epiphany, this won't allow me to charge my batteries when it's off.

So now I'm thinking to go from contactor to main + bus, then to the loads and charge buses, then put the house load wire to the on/off switch. This will allow the batteries to charge as long as the BMS is on to keep the contactor closed.

Here's the next thing, I want to have my engine start with my house bank (only battery I have at the moment) but be able to have a separate gel start battery later on. From what I gathered from the battery switch thread on the C34 forum, I could wire the house to a 1,2,off switch (right now I have a Blue Seas dual circuit switch I had laying around that I thought would work but from reading it's not as good as I thought) and then have the engine on the on/off switch.

I have been working on this for a month now, just now getting the batteries in the other day and I feel like I took crazy pills because I feel like my planning was wrong.

Heres what I'm looking like at the moment:

Can someone clarify what I I'm thinking?

See more @ redemptiverepair.com

[mcarling]

Originally Posted by SailRedemption

I am having trouble trying to figure out how and where to wire my battery switches on my batteries. I started to wire the on/off switch immediately after the main contactor and from there to the main + bus. Then I had an epiphany, this won't allow me to charge my batteries when it's off.

I suggest separate contactors for the load and charge buses.

Originally Posted by SailRedemption

Here's the next thing, I want to have my engine start with my house bank (only battery I have at the moment) but be able to have a separate gel start battery later on.

LiFePO4 batteries are so strong that I see little reason for a separate engine start battery. I don't think it's worth the complexity and expense. Just be sure not to overcharge or fully discharge your batteries.

[SailRedemption]

Originally Posted by mcarling

I suggest separate contactors for the load and charge buses.


LiFePO4 batteries are so strong that I see little reason for a separate engine start battery. I don't think it's worth the complexity and expense. Just be sure not to overcharge or fully discharge your batteries.

Yep, I'm ditching the second battery. Thanks for bringing me back to reality. (:

See more @ redemptiverepair.com

[OceanSeaSpray]

Originally Posted by SailRedemption

...
I have been working on this for a month now, just now getting the batteries in the other day and I feel like I took crazy pills because I feel like my planning was wrong.

Maybe it was wrong. I was talking to a guy who had just fried his boat electrical system using a Mickey Mouse BMS combined with issues in this area just recently.
The BMS dropped the bank and it left the charging system directly connected to the loads on board. Voltage spike out of the MPPT as the battery disappeared and then solar voltage for everyone.

That could happen on a lot of installations I have seen diagrams for by the way.

Keep your engine battery and it can be quite small. It is a completely independent power source to start the motor and redundancy is the reason for having it.

Short of seeing a diagram of what you have/want to do, it seems a bit problematic to take this further.

I don't like battery switches on dual bus lithium systems. Opening both the load and charge bus contactors effectively performs a disconnect. Also I like to see the alternator output tied to a battery, not to a switch, and I like to split the alternator output with blocking diodes. No combiner switches, VSRs etc.

Eric

[mcarling]

Originally Posted by OceanSeaSpray

Maybe it was wrong. I was talking to a guy who had just fried his boat electrical system using a Mickey Mouse BMS combined with issues in this area just recently.

I don't use Battery Murder Systems. I believe (but cannot prove) that they kill more batteries than they save. I use a low voltage cutoff for the load bus and a high voltage cutoff for the charge bus based on overall battery voltage, not cell voltage. Now I'm putting together a battery with 120 CALB CAM72 LiFePO4 cells. The only monitoring of cell voltages will be with a hand-held multimeter. In my experience, LiFePO4 cells only have balance problems when they are abusively charged or abusively discharged.

[SailRedemption]

So I figured it out, just needed to do something else for a while(plumbing)!

I'll go from: battery + to main fuse to the contactor, to the main bus bar, that splits to the load and charge bus.

The load bus will have the house and starter wires. House wire will go from load bus to the on/off switch then to panel. The starter wire will go from load bus to dual circuit switch(only used as off/on) then to the engine starter.

I'm going to draw up a new diagram since my current one is in need of changes before this anyway.

See more @ redemptiverepair.com

[SV THIRD DAY]

Originally Posted by SailRedemption

Yep, I'm ditching the second battery. Thanks for bringing me back to reality. (:

See more @ redemptiverepair.com

After a little over a year now of living with my 400AH LeFePO4 bank....today I removed my starting LA battery from the electrical circuit. I'll keep it on the boat just as my cozy security blanket on a trickle charger but I'm about done with Lead!!

[SV THIRD DAY]

Originally Posted by SailRedemption

Yep, I'm ditching the second battery. Thanks for bringing me back to reality. (:

See more @ redemptiverepair.com

After a little over a year now of living with my 400AH LeFePO4 bank....today I removed my starting LA battery from the electrical circuit. I'll keep it on the boat just as my cozy security blanket on a trickle charger but I'm about done with Lead!!

[OceanSeaSpray]

Originally Posted by mcarling

I don't use Battery Murder Systems. I believe (but cannot prove) that they kill more batteries than they save. I use a low voltage cutoff for the load bus and a high voltage cutoff for the charge bus based on overall battery voltage, not cell voltage. Now I'm putting together a battery with 120 CALB CAM72 LiFePO4 cells. The only monitoring of cell voltages will be with a hand-held multimeter. In my experience, LiFePO4 cells only have balance problems when they are abusively charged or abusively discharged.

None of this had anything to do with BMS or balancing. Something very unexpected happened within the pack and cell-level monitoring - precisely - picked it up.

The bottom line is that each cell has a voltage range it needs to stay within. If it doesn't, safety issues develop. Take care of the cells and the pack will take care of itself.
Cells quickly develop balance issues when something goes wrong with them, with their connections, etc. The more cells you put in a pack and the more connections, the higher the risk of something happening precisely, with a huge amount of stored energy around it.

There is a reason why you cannot buy a commercial single 2000Ah marine LFP pack: liability. Too many disturbing "what if" questions with no good answers and the embarrassing prospect of the contraption going on some multi-million dollar asset, with people around it isolated at sea.
It is one thing to knock stuff up together for personal use, and a completely different one to build a system that would stand up to scrutiny. The guy who fried his electronics hadn't asked that simple question "what if the bank got disconnected?"
In the end, he got the answer anyway. If he hadn't, he could be running around broadcasting that everything is fantastic and his way is the way. What a laugh.

[OceanPlanet]

Originally Posted by 44'cruisingcat

So... to save me reading through 4800 posts... has anyone had LiFEPO4 batteries for a long time yet? Like 10 years or more?


Just wondering if the cycle life span has turned out to be as good as claimed.

I don't know of any marine Li installations that are 10yrs old. However I know Genasun has an 1800Ah x 24V system on a Gunboat 90 cat that I think is about 6yrs old. Last year they started getting pesky HV alarm/cutoffs, and they contacted us. A couple calls and a BMS log file later, a cell board module turn out to be corroded (that pack was by a vent that was bringing in wet air). Sent a new board, boat captain installed it, and all good to go.

[SailRedemption]

Originally Posted by SV THIRD DAY

After a little over a year now of living with my 400AH LeFePO4 bank....today I removed my starting LA battery from the electrical circuit. I'll keep it on the boat just as my cozy security blanket on a trickle charger but I'm about done with Lead!!

Yea, that's good to hear! I'll have a spare battery for the windlass up forward I guess that could be my "spare" if need be. Other than that I'm doing only a single bank and making my life easier.

See more @ redemptiverepair.com

[exMaggieDrum]

As part of my research I am looking at what battery/cell configurations would work in the spaces I have available for a LFP battery. I think 400Ah would work and putting together 16 100Ah cells is the best option. That limits the choices of cells and brands.

Winstons are one possibiity but I have not found a US distributor. It seems, from what little I can find, that Balqon is not really functioning as a company. They were the official US distributor for some period. Their website is still up by they have just dropped off the face of the planet. I emailed Winston in China and they say to order direct from them. Anyone done that?

I have done a search on Sinoply cells several times but unable to find any recent posts from anyone who has installed them. I can get them from Lithium Storage in the US. Their website quotes $135/100Ah cell plus shipping. I have not contacted them yet. Can anyone provide any up to date info about their experiences with Sinoply and/or Lithium Storage, or even 2nd-hand info?

CALBs would fit. Any thoughts about how suitable they are compared to Winstons and Sinoplys? Distributors? They seem to have the most sources in the US.

I have ruled out GBS because of the way they terminate the cells.

Still working on the other research and analysis. Much still to do.

Thanks.

[CarstenWL]

putting together 16 100Ah cells is the best option.

I can not see how this can be the best option. If I look at Winston cells (I have 4x400Ah) the price for 4x400Ah is slightly lower than 16x 100Ah. Than think about cell connectors, Cell monitoring, ... for 16 cells.

Regards,

Carsten

[mbartosch]

Originally Posted by CarstenWL

I can not see how this can be the best option. If I look at Winston cells (I have 4x400Ah) the price for 4x400Ah is slightly lower than 16x 100Ah. Than think about cell connectors, Cell monitoring, ... for 16 cells.

In my own installation I finally chose 16 * 100 Ah instead of the 200 or 400 Ah cells. IIRC the price difference to the larger cells was not significant (that was about 9 months ago)

Three reasons for choosing 100 Ah cells:
- the 200 Ah and 400 Ah cells (at least Winston) are higher than the 100 Ah cells. In my case I had to stay below 28 cm, easily done with the 100 Ah cells but not possible with the larger ones
- the smaller cells are considerably lighter and smaller. In my battery compartment I would have a hard time installing the heavier and bulkier larger cells.
- if a cell fails I can rearrange the pack from 4P4S to 3P4S

BTW, cell monitoring is identical regardless how many you arrange in parallel. It's the 4S that need to be monitored.
But you are totally right with the cell connectors. More mechanical connections to worry about.