LiFePo4 - Add on Battery - BOS LE 300

[RobertL]

Hi everyone,
has anyone experience (use / installation) with the BOS LE300 LIFEPO battery which is used to create a hybrid AGM/LIFEPO system?

I currently have a house bank with 3 x 97Ah TROJAN AGMs. Often I see that the bank does not get fully recharged with solar/wind, eventhough up to 30A is be available (flattening charge curve once the AGMs get to > 80% SOC.) So I was hoping that a pack of two LE300s would take up the daily charge/discharge and use all the available solar/wind.

The LE300 is designed to be connected directly to the plus/minus of the AGM battery bank. No changes are needed to the charging system. Although the units appear to be expensive (ca. 469 EURO / 25,6 Ah) they are modular so that battery packs can easily connected together to make a larger system. Not needing to do any further changes to the charging systems is inticing.

Keen to hear your thoughts.

[Pandor]

Well, at least in the US you can likely replace your 300ah AGMs with at least that much LFP for around 469 Euros. This seems much easier, efficient and trouble-free to me. I found most of my existing chargers are LFP compatible. Only added a dc-dc charger from starter battery to house and left the alternator connected to LA starter.

[wholybee]

The likelihood is that your AGM bank is toast. AGM *MUST* be fully charged, or you will kill them, and they will lose capacity. So, it isn't just the LE300 you would need, but also to replace your AGM bank.

For comparison, brand new your AGM bank had about 150Ah, usable. In your AGM banks current condition, a single 100Ah LFP would probably work much better. A 200Ah or 300Ah LFP drop in would be *immensely* better.

There are a few hybrid system fanboys here. But the reality is that while they can work, there just isn't and reason to use them. While they advertise "the best of both worlds" really you get the worst of both worlds. And 469 Euro for 25Ah is crazy stupid expensive. Just buy a couple hundred Ah of LFP and dump the AGM.

[HeinSdL]

Originally Posted by wholybee

The likelihood is that your AGM bank is toast. AGM *MUST* be fully charged, or you will kill them, and they will lose capacity. So, it isn't just the LE300 you would need, but also to replace your AGM bank.

For comparison, brand new your AGM bank had about 150Ah, usable. In your AGM banks current condition, a single 100Ah LFP would probably work much better. A 200Ah or 300Ah LFP drop in would be *immensely* better.

There are a few hybrid system fanboys here. But the reality is that while they can work, there just isn't and reason to use them. While they advertise "the best of both worlds" really you get the worst of both worlds. And 469 Euro for 25Ah is crazy stupid expensive. Just buy a couple hundred Ah of LFP and dump the AGM.

At the moment I am subscribing to the "best of both worlds" point of view, not to buy AGMs specifically, but to continue finding a use for my legacy AGMs which are still in good condition.

To learn more however, why am I potentially getting the worst of both worlds?

[Pete7]

This is our latest installation which has changed considerably over the years. We plan to add the 75A electric dinghy battery into the system to charge it and when not being used increase the size of the house bank.

We like having a hybrid system because it enables us to shut down the LFP when not on board and allow the lead acid to run the bilge pumps etc, powered by solar.

The original idea came from here:

https://www.zwerfcat.nl/en/lithium-hybrid.html

It also means that in the unlikely occurrence of the LFP BMSs shutting down we still have power available. In addition also meant we could continue to put our Trojan TMX24s to good use for a while.

There is some common sense needed with the installation. Adding LFP to a failing house bank isn't going to work. The lead must be in good condition for it to work. However, you don't need a large lead acid bank. Indeed increase the size of the LFP instead.

What happens in normal use is the LFP provides all the power and the lead acid sits there twiddling its thumbs just in case. If a large load is applied like our 1kW 230v electric kettle, solar will provide say 20A, the LFP 40A and the lead acid 10A. Once boiled, solar will then recharged the batteries as required. LFP charges much faster.

There is no way I would buy those BOS LE 300 widgets. They are tiny and over priced in Europe. You could have 4 times the capacity for similar money. You also need to think about heavy duty fuses for the system.

Happy to discuss further if required.

Pete

[Fiso]

Just my 2 cents here, but a hybrid (mixed) system, to me anyway, sounds like a gizmo, not a solution. Not a basher mind you... I am in the same situation. I have thought about the same thing. 300Ah of AGM that have slowly lived a good life, but death is upon them coupled with two starting AGMs isolated, same charging systems. I will retain the two AGM starting batts.

I was adamant that I was going back with AGM for that reason. The chargers / everything already in place, until I saw what inflation has done to (Good) AGM prices vs. LIPO4. They are much closer than I thought these days. AGM 50% deep / cycle count vs 90% deep / much greater cycle count for LiFePO4.

So, to the point of a mixed solution. I can’t get past (in my mind) the management differences in charging profiles / discharge profiles. Believe me when I tell you, with what I do as a profession I understand that a software/hardware profile can be made to differentiate the two, manage it (somewhat), but electrons want to do what electrons do, and a management system between them to keep it healthy seems gizmo ‘Ish to me vs. just changing to a properly designed LiFePO4 isolated system for the house bank. Yes, it will cost me some parts if I do that, and again, I haven’t made that decision yet, but for me it will either be full AGM or isolated LiFePO4 / isolated starting AGM, both with specific dedicated battery management systems.

[HeinSdL]

I like the idea of the AGMs almost always sitting on float charge, around 13.5 volt, thanks to the flat curve of the LFP. This is excellent for the AGMs, no need for gizmos IMO.

And then there are all the benefits mentioned above, with AGMs being much more suited to look after the boat while away from the boat, AGMs step in only when needed (most) at say 12.7V meaning LFP can 'relax' at low SOC and I don't need to junk my AGMs which are good, just not entirely sufficient.

[Rohan]

This is better asked in the lithium systems forum.

https://www.cruisersforum.com/forums/f166/

[wholybee]

Originally Posted by HeinSdL

I like the idea of the AGMs almost always sitting on float charge, around 13.5 volt, thanks to the flat curve of the LFP. This is excellent for the AGMs, no need for gizmos IMO.

And then there are all the benefits mentioned above, with AGMs being much more suited to look after the boat while away from the boat, AGMs step in only when needed (most) at say 12.7V meaning LFP can 'relax' at low SOC and I don't need to junk my AGMs which are good, just not entirely sufficient.

Among the best advantages of LFP are that there is almost zero Peukert factor. There is no need for temperature compensation. You can use (almost) 100% of the capacity. There is no risk of damage due to PSOC.

As soon as you create a hybrid bank, you lose those advantages. You have more capacity, but you have a battery that is difficult to know the SOC, that you need to monitor, calibrate and perform maintenance on. You have added capacity, but lost almost all of the advantages of LFP.

I think many don't realize how life changing those advantages are. LFP if done right is a forget about it thing. Like being on shore power. You don't have to worry if it is fully charged regularly. You don't have to check that your SOC meter is correct, or recalibrate for capacity loss every year. Just set an alarm at 10% SOC so you can recharge before the lights go out. And if the lights do go out, you don't damage anything, you just have no power until you recharge.

The trend is that people want more tech, so they add all this complexity to LFP so they can micromanage it. But that is the opposite of what LFP needs. And they are so used to micromanaging AGMs, they are totally lost on how easy LFP is because they never give it a chance.

I get the desire to not throw away good AGM. But AGM is so heavy and huge compared to LFP. It only really makes sense if you have say a 2 year plan to buy half an LFP bank now, and the other half next year for budgetary reasons. And even then I would strongly discourage it.

When not onboard or away, just set the full charge voltage of the solar to 3.8V or less. Then it is just as good as an AGM in that situation.

[Sos]

In answer to the OP's question, yes I have fitted two of them.

We have two Victron 160 AH batteries that were recently fitted as part of an insurance claim. I wanted more capacity but didn't want to replace the new batteries so went down this route. Keeps the Victron's fully charged and runs the fridge and soon the small freezer we are going to fit. We are a cat so have quite a bit of solar to keep everything topped up when sunny.
A good solution if you don't want to change your charging system and have good batteries already.

[SV_FlyingTigress]

Check out this. It is designed to manage combined lead LFP systems: https://www.emilyandclarksadventure.com/bbms

[Sos]

Originally Posted by SV_FlyingTigress

Check out this. It is designed to manage combined lead LFP systems: https://www.emilyandclarksadventure.com/bbms

Looks like they are only shipping to the US at the moment.

[Tortuga's Lie]

This may sound like a NUB question, but if you go all LFP, how does this handle the surge load of starting your engine? I thought LFP's didn't like this.
Also, if I go all LFP, will my Balmar external regulator be enough to protect the alternator? I think it's an MC-618.
Thanks,
Tom

[wholybee]

Originally Posted by SV_FlyingTigress

Check out this. It is designed to manage combined lead LFP systems: https://www.emilyandclarksadventure.com/bbms

This gets posted again and again. It doesn't change the fact that a hybrid system is a solution looking for a problem.

And, you still wind up with the worst attributes of a Lead-Acid battery mucking up an otherwise great LFP system.

[wholybee]

Originally Posted by Tortuga's Lie

This may sound like a NUB question, but if you go all LFP, how does this handle the surge load of starting your engine? I thought LFP's didn't like this.
Also, if I go all LFP, will my Balmar external regulator be enough to protect the alternator? I think it's an MC-618.
Thanks,
Tom

The actual LFP battery/cells can withstand huge currents, much more than lead-acid. The limitation is that the BMS in most drop-in batteries can't. So, typically, a lead-acid is retained for starting, but not as a hybrid, as the 2 banks would be kept isolated from each other. And starting is really the perfect application for lead-acid, as starting uses almost no capacity(Ah) so quickly gets back to 100% and stays there. Lead-Acid sucks for a deep cycle house bank, so that bank should be 100% LFP.

As an alternative there are a few drop-in LFP batteries that are built for starting and have a BMS that can take it. Expensive, but a few people spring for them. Or, if you opt to not use a drop-in but build a bank from scratch, then it's relatively easy to build one that can be used for starting.

The MC-618 will protect your alternator from overheating, yes. Make sure that the alternator temperature probe is installed, and make sure it is set for a Lithium profile. It would also be a good idea to add the Balmar APD to protect from an unexpected BMS disconnect.