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

[john61ct]

Originally Posted by Inkog

The Renogy B2B is a rebranded Chinese device.

True for everything Renogy, I believe just a marketing/distribution company out of China, don't actually have their own factory.

The Sterlings may not be perfect but IMO certainly the best on the market.

60Ah may well be a maximum, or input current or both, just like solar panel specs.

Have you contacted them to see if there's a fix for the heat issue? An ExpeditionPortal member went through that, and they replaced with a newer model, even though it was out of warranty.

You can communicate directly with Charles Sterling the designer and founder if needed, but start out with the right contact for whatever continent you're on.

[newhaul]

Originally Posted by Inkog

. The Renogy B2B is a rebranded Chinese device. Dometic sells the exact same device in Europe.

can you point me to the manufacturer ?

[john61ct]

Originally Posted by ReneJK

so aside from the heat protection & reducing amps , it does work albeit not at the 60A's ?

Yes, great units, just stack them if you need more current.

Or put a good current-limiting VR on your alternator.

Critical is to be able to tweak-adjust your voltage output to exactly what you want rather than accepting canned choices.

Stop-charge rather than Float is a bit more of a challenge if you care about that.

[Inkog]

Originally Posted by newhaul

can you point me to the manufacturer ?

Who knows, but here is the Dometic version sold in Europe:

https://www.dometic.com/en-gb/uk/pro...12-40-_-152914

And Renogy in the US:

https://www.renogy.com/renogy-12v-dc...ttery-charger/

The outside cases differ slightly but the manuals are identical neither bothered to rewrite them.

The manual states there is a 60A version, but neither Renogy or Dometic sell it.

[newhaul]

Originally Posted by Inkog

Who knows, but here is the Dometic version sold in Europe:

https://www.dometic.com/en-gb/uk/pro...12-40-_-152914

And Renogy in the US:

https://www.renogy.com/renogy-12v-dc...ttery-charger/

The outside cases differ slightly but the manuals are identical neither bothered to rewrite them.

The manual states there is a 60A version, but neither Renogy or Dometic sell it.

for everything not refrigeration dometic is just a reseller .
As to the renogy brand idk but likely just like just about every electronic device likely made in the orient.
Quality just depends on quality control .

[ReneJK]

Originally Posted by tanglewood

I guess I just don't understand a power system design that takes 220A of alternator capacity and reduces it down to 40, or 50, or 60A (doesn't matter which). To me, priority one would be directing full alternator output to LFP charging and house loads, regulated as needed for continuous duty. For the cost of the Sterling plus the Blue Seas disconnect you could install a single Wakespeed or Balmar regulator and have a power system with 220A capacity rather than 60A.

1) I will continue to use my 2 alternators to charge 2x AGM batteries , so they will still be used

2) the current limiter 'function' of the Sterling will allow me to charge my LFP bank without burning them up within 30 minutes (which ive done twice already due to my own stubbornness , charging an empty AGM bank with them . with an external regulator that had a defective temp sensor)

3) the cost of the Sterling + display (from an official dealer) + 3x Blue Sea latching relays (new from eBay) is the same price as a SINGLE wakespeed WS500 , since I have 2 alts that cost would double (ie $1200 ?) whereas the Sterling+display and 3x Bluesea relay came to roughly $550 total

4) afaik the WS500 needs M$ windows , I dont have that

5) I can still use my old wind gen , solar, battery charger etc WITH teh sterling and get amps out of them for no extra costs (ie teh sterling would already be in place for teh alternators , WS500 cant do that and if I wanted to still use what I have it would cost me even more

[nebster]

Originally Posted by john61ct

Bottom balancing is best if you regularly draw your bank down to **very** low SoC, in effect ensuring you can discharge as deep as possible without an imbalance "blocking" you via the BMS per-cell protection.

It also **requires** you to regularly go down that low, balancing must be manual, and

more frequently than you would need to just doing capacity benchmarking.

Absolutely incorrect. A balancing decision has nothing to do with whether you are "required" to "regularly go" to the balancing voltage.

What matters is whether your cells can maintain their state relative to each other. Which, in the real world, at fractional rates with good thermal stability, I believe most modern prismatic LFPs can.

I am skeptical that you have any experience with this, and I think you should stop writing when you don't.

[john61ct]

Originally Posted by nebster

A balancing decision has nothing to do with whether you are "required" to "regularly go" to the balancing voltage.

Well yes, obviously in a perfect world, cells do not need balancing at all.

But even perfectly matched top quality cells do eventually age, and as they do, balancing them does become increasingly necessary.

The question I was responding to
http://www.cruisersforum.com/forums/....php?p=2955153
was simply whether to top or bottom balance.

My point is, if you choose to balance at the bottom, then if (when) they do need balancing, it needs to be done manually, and at a very low SoC.

Which is both more stressful to the cells, and less convenient for the owner, than the automated top-balancing that 99% of us simply let the BMS handle for us.

[nebster]

Originally Posted by john61ct

My point is, if you choose to balance at the bottom, then if (when) they do need balancing, it needs to be done manually, and at a very low SoC.

This is also not strictly true, although it is at least directionally reasonable instead of utter nonsense.

To the folks thinking about building up a real battery: please be careful making technical choices based on the theories of random internet people who demonstrate no hands-on experience.

[nebster]

Originally Posted by john61ct

Which is both more stressful to the cells, and less convenient for the owner, than the automated top-balancing that 99% of us simply let the BMS handle for us.

Please identify your battery and automated top-balancing BMS you are using.

[nebster]

Originally Posted by Cpt Pat

It appears to me that cell balancing is just an academic exercise when one has quality cells and uses those cells conservatively at fractional C charge and discharge rates.

Your experience matches my personal observation exactly.

Anyone who is triggering a rebalance on their BMS regularly is probably pushing the limits of the chemistry in a way that is likely to have a deleterious effect on lifetime (which could be a fine and justifiable decision, nonetheless).

Anyone who stays in a more conservative regime and verifies consistent cell quality at the start can probably dispense with any concern about rebalancing, at least for many years of normal use.

If the latter path is chosen, then the question of balance voltage becomes a very symmetric one, since in that case a meaningful voltage differential in normal use will never be encountered. The question then becomes: do I think I will be more likely to accidentally discharge my pack or overcharge my pack? The answer to that question can then sort out the balancing decision.

The standard path is to use a top-balancing BMS and call it a day. That's should be the default choice, since it's by far the most common approach. But the reasons for that default are sometimes (often?) in conflict with how I think a lot of us would prefer to manage our investment, which is why I keep participating when this topic comes up.

[CatNewBee]

I guess, you all are discussing extremes. Balancing takes place / starts usually at 80... 90% SOC with cheap BMS systems, and adjustable BMS can even define start balancing only when charge current higher than the balancing current is flowing.

Usually, with solar and while cruising you rarely hit that SOC, because you use energy for the navigation, auto pilot, watermaker, cooking... Also you have shading when using the sails, so you harvest less energy than at anchor. My battery goes close to the full state maybe once in a week or every 15 days, then some balancing takes place.

It is really about your system and use pattern, not about technology. The BMS takes care of yout battery if you are not watching it, just set it and forget it.

Regarding your alternators, they usually are doing fine, LFP batteries stay at higher voltages than AGM start batteries (13.4V vs. 12.8V), alternators are set at 14...14.2V, charge current is not the maximum possible current any way, usually, there is no problem to charge the house bank directly. You can connect and disconnect the alternators, if wanted, based on SOC or Voltage to keep the current in some limits, no fancy B2B necessary, but of course you can use one, two or more B2B charger in parallel.

[tanglewood]

Originally Posted by Cpt Pat

It appears to me that cell balancing is just an academic exercise when one has quality cells and uses those cells conservatively at fractional C charge and discharge rates. The trouble arises when one wants to operate at the factory rating extremes (10-90% SoC, and factory maximum charge and discharge rates)

Confession time. I have never balanced my cells, not even when first commissioned. They were all really close from the factory (CALB), so I just went for it to see how they would behave.


I charge with solar to 3.45vpc, float (yes, there is that dirty word) at 3.35vpc, and the backup generator starts at 3.1vpc. I typically see a max of around 5mv difference cell to cell, and the long term max spread is about 70mv. I think that max spread is because I need to clean the battery terminals since it seems to happen when there are heavy loads running like my air compressor or car lift.


I'm just waiting to see when I might need to do any balancing, but so far none is required.

[tanglewood]

Originally Posted by nebster

Your experience matches my personal observation exactly.

Anyone who is triggering a rebalance on their BMS regularly is probably pushing the limits of the chemistry in a way that is likely to have a deleterious effect on lifetime (which could be a fine and justifiable decision, nonetheless).

Anyone who stays in a more conservative regime and verifies consistent cell quality at the start can probably dispense with any concern about rebalancing, at least for many years of normal use.

If the latter path is chosen, then the question of balance voltage becomes a very symmetric one, since in that case a meaningful voltage differential in normal use will never be encountered. The question then becomes: do I think I will be more likely to accidentally discharge my pack or overcharge my pack? The answer to that question can then sort out the balancing decision.

The standard path is to use a top-balancing BMS and call it a day. That's should be the default choice, since it's by far the most common approach. But the reasons for that default are sometimes (often?) in conflict with how I think a lot of us would prefer to manage our investment, which is why I keep participating when this topic comes up.

Exactly my experience too, from another person who is actually using this stuff on a daily basis.


Re top vs bottom balancing, I think you are exactly right. I full charge on a daily basis on solar 9 months out of the year, and every 2-3 days the rest of the year. So I care MUCH more about rogue cells at top of charge than bottom of charge because I see top of charge 10 times for every bottom of charge.

[evm1024]

Originally Posted by nebster

Absolutely incorrect. A balancing decision has nothing to do with whether you are "required" to "regularly go" to the balancing voltage.

What matters is whether your cells can maintain their state relative to each other. Which, in the real world, at fractional rates with good thermal stability, I believe most modern prismatic LFPs can.

I am skeptical that you have any experience with this, and I think you should stop writing when you don't.

To the folks thinking about building up a real battery: please be careful making technical choices based on the theories of random internet people who demonstrate no hands-on experience

Very well said.

It would be far better to rely on the opinions of those who have demonstrated experience and knowledge.