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

[SV THIRD DAY]

Originally Posted by Merc83

Hello and thanks for your reply.
So you do not take any notice of what load may be on the cells when charging, just set it to turn the charging off at 13.8 volts?

I guess if I was running my 1500W hot water heater or 1100W water maker, then I would pay more attention, but the reality is that a 2-10A DC load drawing on the bank while you are charging just isn't going to cause the battery voltage drop like it will on a Lead Is Dead wet acid battery to throw off the charge profile.

My set-up is also a reflection of the way I live aboard.
We are on a mooring now and only go to the pump out dock once a week, so the main source of my battery charging is from Solar. I just run the generator now and then but I'm 90% off solar. So I simply set my BlueSly Solar controllers to a charge voltage of 13.8v. Bulk...absorb...float...I set all the modes to 13.8v That way when the battery is charged to 13.8v, there is no more driving force to push in amps and I can indeed see the taper off in Amps on my Amp meter. I have NEVER turned my solar controllers off. I am simply relying on the 13.8v set-point to not overcharge. And with 1500W of solar, that happens pretty fast on a sunny day. Now before the wood is piled around the stake to burn this heretic alive, I live aboard and work from the boat, sitting at my desk with the cellog cell meter, overall volt meter, and Amp meter within easy eye-shoot. This isn't something I just set up and walked away with, I've been watching and collecting data on it now for 2yrs which is why I feel comfortable with it. Of course I was told everything from I will blow the bank up and kill myself to I will damage the battery...but the bank is working like a dream for me without all the drama. Even a broken clock is right twice a day...so who knows...maybe my time is about up...

[evm1024]

On second read looks like Rich has the correct meaning of your question.

[exMaggieDrum]

Has anyone designed an elegant way to use a latching/b-stable battery switch using the House Power BMS with easily obtainable relays, etc. as needed, that is, without a DIY circuit board to handle the bi-directional relay signals? I would love to use a Blue Sea 7700 remote battery switch because of its extremely low continuous power consumption (0.0mA). The House Power BMS doesn't send an external signal when going from an HVC or LVC warning level to a "normal" level, other than not sending the signal for the warning event. This may be really simple and I just haven't put enough brain power in to it from a circuit design point of view.

BTW - thanks for the posting on the Super-B batteries from the Netherlands. Any pricing info available? The manual is very good. I'm committed to DIY right now but am curious. I like that it automatically handles a latching/bi-stable switch.

[BigBeakie]

Originally Posted by exMaggieDrum

BTW - thanks for the posting on the Super-B batteries from the Netherlands. Any pricing info available? The manual is very good. I'm committed to DIY right now but am curious. I like that it automatically handles a latching/bi-stable switch.

They are about $2,000 for the 160Ah.

Any other comments from anyone, please? I know that drop in LFP are viewed very suspiciously by the guru's here because of the importance of the BMS,
but do these Super B have that BMS issue covered, or not? That is my question.

[Merc83]

Hello Third Day and EVM 1024,

You have answered my questions beautifully, I thank you. I now understand what is happening when charging with a load present. These LiFeP04 cells take some getting used to. The hardest part is clearing the years of fog left in the brain from the Lead Acid days and starting fresh with news ways of doing things. No doubt I will have further questions in the future and I will keep reading and trying to soak up the knowledge from this fantastic thread.

Many Many thanks to all those who contribute to help others learn.

Cheer,

Les

[campr]

I'm going to implement a victron buck converter to charge my lipos from the engine: https://www.victronenergy.nl/dc-dc-c...verter-25a-50a it provides s fixed voltage source only when the engine is running. Seems like a good idea. Anyone care to chip in on this idea?

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[Anjin]

Originally Posted by campr

I'm going to implement a victron buck converter to charge my lipos from the engine...Anyone care to chip in on this idea?

Sounds like a pretty good idea, and I've been looking for something like that. The buck converter is supposed to be for "smart" alternators - not sure what that means but the description implies variable voltage and/or current. I have particularly "stupid" alternators - hitachi 80 amp on each of my two Yanmar 54hp diesels. I say "stupid" because they will overheat if you try to approach anything like 80 amps and then they will compensate by lowering the voltage in order to reduce the current. Hard to adapt a stable profile for LiFePo charging especially since they have no remote sensing for the state of charge.

The buck booster allows you to set the charging voltage, charging current and maximum input current. That would allow me to protect my alternators by setting them down to, say, 40 amps continuous and keep a constant charging voltage available. I'd wire it in parallel with the starter battery so I could turn it off without worrying about blowing the diodes on the alternator (the starter battery would absorb the surge). In any case I'd want a way to turn it off remotely in case the LiFePo's were already fully charged. That could be manual (a remote switch on the input or output) or an independent monitoring/control circuit - or even the BMS as a last resort.

If I went this route, I think I'd take the Rich Boren approach - set it to 13.8 V and just treat it as another charging source. And If I've oversimplified Rich's approach, blame me not him.

- Art

[campr]

Art, there seems to be an override wire on the device which allows you to switch off the buck converter, even if it detects an engine start.

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[Maine Sail]

Just a quick update on my external rectification modification.

Since converting to external rectification, of my small case CS130D based alternator, I can continuously run about 20A more than I previously could and do so without over heating.. So far my peak recorded temp has been 218F on a charge from 80% DOD with a 1:20 minute run.. I am using a remote cylinder head temp monitor for motorcycles that captures peak temps and holds them in memory so I don't have to stare at it all the time......

So far this mod seems to be working well in my application but I still want to get more data. The conversion was done for my by Mark Grasser DC Solutions.

Still I think the best option is to go to a large frame alternator designed and intended for high output for long duration's. I did not have the room for this and already have a Sea Frost system so getting the most out of a small frame alt was in order...

[OceanPlanet]

Originally Posted by Maine Sail

Just a quick update on my external rectification modification.

Since converting to external rectification, of my small case CS130D based alternator, I can continuously run about 20A more than I previously could and do so without over heating.. So far my peak recorded temp has been 218F on a charge from 80% DOD with a 1:20 minute run.. I am using a remote cylinder head temp monitor for motorcycles that captures peak temps and holds them in memory so I don't have to stare at it all the time......

So far this mod seems to be working well in my application but I still want to get more data. The conversion was done for my by Mark Grasser DC Solutions.

Still I think the best option is to go to a large frame alternator designed and intended for high output for long duration's. I did not have the room for this and already have a Sea Frost system so getting the most out of a small frame alt was in order...

Exactly what we've been doing for charging Li; if possible fit in large case American Power Systems, Inc. (APS) alts (often using a modified shortened version so the pos. stud doesn't extend as far out the back), but if those don't fit then going small case (usually MGDC) with external RR's.

[Cottontop]

I searched but didn't find much.

Is anyone familiar with the Enphase LiFePO4 batteries with their "micro-inverters"?

[campr]

The micro inverters go to 110/240V right? They do not provide for any battery charging capabilities.

As for the LiPo part, not much more available than that they use 'AC batteries' which I assume means that they use inverters included in a battery module. Their batteries are Eliiy Power.

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[bill good]

Micro inverters are used on larger solar installations where the loss of one panel/inverter combination only results in a small over all loss.(Built in redundancy). This configuration allows for expansion when needed. Yes they produce only AC voltage. Mostly set up for on grid systems.

Regards

[Cottontop]

There's a thread running where someone actually tested panel shading. A little shade on one panel (they used two panels, both in series and parallel), and production was cut in half. Any shade on both panels and production was cut even more sharply.

Well, I have an arch that's going to shade some part of the array most of the time (relocating the arch will not be easy), so I have gotten interested in Enphase's micro-inverter system. As noted above, the micro-inverters on the panels seem to limit the loss of production due to shading to the proportion of the array shaded. I can live with that. Then they have their micro-inverter AC batteries. How charging happens is not clear. But as I am going to have a mostly AC boat, this whole get-up might make sense for me, if I can figure it out.

[OceanPlanet]

Using micro-inverters on each panel would in effect be the same as using one small MPPT controller per panel...except the AC output would have to sync with an inverter sine wave to contribute to AC loads.

Makes more sense to put the energy into the batteries (DC) and then use as needed via the inverter....