Combining lead & lithium batteries

I came across an interesting product that allows you to combine LiFePo4 batteries with AGMs in a house bank. There are several advantages, including getting more capacity from your battery bank, more capacity from solar panels, and extending your AGM battery life. The cost of it is $530 with a necessary contactor. You can watch a video of it here: https://youtu.be/AJIFW_2GEwc

The product is called the "Battery Bank Manager Plus" and is made and sold by Clark of Emily & Clark's Adventures, a sailing Youtube channel. I have no association with them except as an interested potential paying customer. It seems to have a lot of advantages, but I'm not keen on installing a little black box with questionable long term support that controls an important function on the boat.

I have 6 Lifeline 4D AGM batteries, each with 210A-Hr capacity at 12V. I have a 24V DC system, so my combined house bank capacity is 6 x 210 / 2 = 630A-Hr at 24V. Or half of that, 315A-Hr, if you discharge to only 50% of the bank's capacity. I'd like to exchange 2 existing AGMs for 2 new Battleborn 8D 12V LiFePo4, each with 270A-hr capacity. I would be losing 105A-Hr of AGM capacity but gaining 190A-Hr of lithium capacity (assuming I can use 70% of the lithium capacity) for a total gain in capacity of 85A-Hr (27% more capacity than I have now). That doesn't sound like a lot, but I will also be extending the life of AGM batteries and getting more capacity from my solar.

The total cost of this would be between $5K assuming I can sell my 1 year old AGMs for something. Have any of you seen this product, installed it, or considered something similar?

The claims that are made about this product don’t seem credible to me.

Stick with your AGMs.

Lifelines are rather expensive. Good quality G31, 100 Ah AGMs available from Renogy and others cost about $200 each. When your Lifeline’s give out, consider replacing with a bank of these.

David

DavidM said:

The claims that are made about this product don’t seem credible to me.

Stick with your AGMs.

Lifelines are rather expensive. Good quality G31, 100 Ah AGMs available from Renogy and others cost about $200 each. When your Lifeline’s give out, consider replacing with a bank of these.

David

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"Good quality" and Renogy don't belong in the same sentence..

This was a brand spanking new Renogy 100Ah that could barely deliver 72Ah.

CMS said:

"Good quality" and Renogy don't belong in the same sentence..

This was a brand spanking new Renogy 100Ah that could barely deliver 72Ah.

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I suppose WindyNation and Weize fall into that same category. If so is there any acceptable AGM that is cheaper than Lifelines?

Davis

DavidM said:

I suppose WindyNation and Weize fall into that same category. If so is there any acceptable AGM that is cheaper than Lifelines?

Davis

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Odyssey

Insequent said:

Odyssey

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+1

I've been using combined lead and lithium on my boat and RV for a couple years now, with great success after having seen Emily and Clark's video on how to combine them properly.

There are some caveats you can't just go ahead and do it blindly. You need to know the float current required from your lead batteries, and you must have a proper charge controller with the cut off on your lithiums otherwise you are taking great risks.

His new Gadget sounds good, though I haven't seen it or tested it.

???
Everywhere I look, a 100AH Odyssey cost as much or usually more than Lifeline. Please give links to quotes.

I just replaced the Lifeline AGM batteries in my sailboat last month. They were purchased in July 2005. On test, they have about 78% of brochure capacity, however the internal resistance is higher which is why I replaced them.

"You pays now, or you pays later." I guess I would have put in Renogy, if I were selling the boat immediately and needed to claim the batteries were new.

DDW said:

"You pays now, or you pays later." I guess I would have put in Renogy, if I were selling the boat immediately and needed to claim the batteries were new.

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then the new owner can complain in 1.5 years how much of a knucklehead the "PO" was...

Full River is the only imported AGM worth buying. Best bets are still Lifeline, Odyssey & Northstar. Firefly were amazing but they had major QC issues and it killed them.... Why anyone would invest in AGM these days is beyond me...

I'll second the Fullriver AGMs as being good quality. Lifeline, Odyssey, Northstar, Trojan, Rolls, and a couple others all make good FLA and AGM batteries as well. Based on similarity in specs and appearance, I've been suspecting that the Rolls AGMs might actually be made by Fullriver. The Rolls AGMs are not US made like their other batteries from what I've seen.

At this point, I'd say LFP is at least worth a good assessment before buying a lead based house bank. But it doesn't necessarily make sense for every application yet, especially if cost is a concern.

Max1 said:

I've been using combined lead and lithium on my boat and RV for a couple years now, with great success after having seen Emily and Clark's video on how to combine them properly.

There are some caveats you can't just go ahead and do it blindly. You need to know the float current required from your lead batteries, and you must have a proper charge controller with the cut off on your lithiums otherwise you are taking great risks.

His new Gadget sounds good, though I haven't seen it or tested it.

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Thanks for the very relevent reply Max1. The big advantage to the BBMS is that it allows you to bolt on LiFePO4 to an existing lead battery bank without much modification. The charge controller (whether it's a battery charger, solar charger, or alternator regulator) can be left alone with the lead charge settings. The BBMS will control a contactor that allows that current to charge the lithium batteries. I think I have that right.

I am not sure you need a $350 device to combine lithium and AGM batteries. A few weeks ago Helmsman (one of the gurus here) introduced me to an article by Jim Healy. He advises the ABYC, and in the link below he describes, among other things, how the two types of batteries can be charged and used in the same system. Very clever approach. Worth the read on many levels.

https://gilwellbear.wordpress.com/ca...ries-on-boats/

Anyone going down this path should know that the recently released ABYC spec for Lithium Ion batteries recommends against including different battery chemistries in the same bank. Lead batteries can short out and melt down, and it's not an uncommon occurrence. It's a safety concern because if a failing lead battery is connected to an Li-ion bank as it is in a hybrid, there is a massive amount of current that will get dumped into the failing lead battery. I'm not totally up to speed on all the considerations, but that's the key thing that I recall.


Also, ISO has a draft pre-standard much like ABYC's earlier TE-13 Technical Report. ISO flat-out prohibits hybrid banks.


Creating such hybrid banks has definitely been a popular approach, but anyone continuing to do so should do it knowing which direction the standards are pointing.

HeadedToTexas said:

I am not sure you need a $350 device to combine lithium and AGM batteries. A few weeks ago Helmsman (one of the gurus here) introduced me to an article by Jim Healy. He advises the ABYC, and in the link below he describes, among other things, how the two types of batteries can be charged and used in the same system. Very clever approach. Worth the read on many levels.

https://gilwellbear.wordpress.com/ca...ries-on-boats/

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The link does not go to your intended topic.

Hehe, not sure how that happened. This link goes where I think it should go.

https://gilwellbear.wordpress.com/c...-topics/lithium-chemistry-batteries-on-boats/

The section is about 75% down the page and titled How A “Hybrid” Battery Bank Works.

That said, I think the right approach is to follow the ABYC including the new spec for lithium batteries. Guess the linked discussion is rather academic at this point. Enjoy.

CMS said:

Firefly were amazing but they had major QC issues and it killed them.... Why anyone would invest in AGM these days is beyond me...

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We got lucky with our Firefly batteries, bought early when they were still being made in the US and haven't had the quality/failure issues that sunk them.

At the time Firefly's represented a lot of the advantages of Lithium without the need to change infrstructure around them. They were also less expensive (at the time) than Lithium and made sense to my brain and pocketbook.

When these are done, we'll replace with LifePo.

I’m a fan of lithium, but until insurance companies get on board our use of lithium banks will remain isolated and supplemental. We only use them to slowly push the last 1200 watts or so into our house banks overnight completing the charge cycle that the solar can’t. This makes can make a huge difference in agm lifespan for those who spend most of their time away from docks and yellow umbilicals. Time will tell, but I see more problems with these hybrid approaches than solutions.

HeadedToTexas said:

Hehe, not sure how that happened. This link goes where I think it should go.

https://gilwellbear.wordpress.com/c...-topics/lithium-chemistry-batteries-on-boats/

The section is about 75% down the page and titled How A “Hybrid” Battery Bank Works.

That said, I think the right approach is to follow the ABYC including the new spec for lithium batteries. Guess the linked discussion is rather academic at this point. Enjoy.

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The gentleman doesn't seem to know as much about LFP as he thinks he does. In any case, if you don't start your education by reference to CMS's unbelievably helpful Marine How-To site you are wasting a lot of time.

This isn't really a 'same bank' from what I could see. It's a relay connecting a legacy battery bank to a new lithium bank. Software monitors voltage and current and opens/closes the relay. Like an ACR, but with different operating parameters.

I wouldn't choose that product, but the idea of extending the capabilities of a LA bank with a lithium add-on is an attractive one for lots of people.

What's a properly engineered system look like to do that? It would be easy to have a stand-alone lithium battery connected to the house bank with chargers in both directions. Charge the lithium during the day, then reverse at night. Or have a simple controller based on house SOC. Not hard to monitor and control.

I think the safest and easiest solution would be to make the lithium bank 48V, make it adequately-sized to essentially replace the capacity of the 12V bank (or bigger), and use MPPT controller(s) between the 48V bank and the 12V bank as a DC to DC charger. Everything on the boat would still run on 12V and the lithium bank would only be used to keep the 12V bank charged. Solar panels and/or a separate 120VAC 48VDC charger would be used to charge the 48V bank. Said 120V charger could run off a 12V-powered inverter when the engine(s) is running if there's excess charge current available from the alternator(s) There likely would be excess current available since a properly-sized lithium bank would tend to keep the 12V batteries fully charged all the time. The lithium bank could be installed anywhere on the boat because the cables necessary for 48V are tiny and voltage loss would be insignificant. This would be a huge advantage if the 12V house bank is in the engine room since lithium batteries would not do well in that kind of heat.



For example, if the boat worked well on a 600 AH 12V FLA bank (so 300AH in usable power) adding a 100AH 48V lithium bank and a 75/50 (75 volt DC in/12V 50amp out) MPPT controller (or two of them) would more than double the 12V capacity to 700AH. Thus the FLA batteries would not normally discharge at all, but you'd always have the option of using their capacity, say to run a stateroom-sized air conditioner for a few hours on a really hot night at anchor. The MPPT controller(s) would take away all the worry about excessive current between the banks and trying to match charge profiles.



The lithium bank would also be perfectly suited to solar use too, since they can be re-charged at max current all the way to 100% SOC. A big solar array (say 2000 watt for a boat that uses 4 kWh every 24 hours) and a lithium bank as described could all but make the genset moot, even on cloudy days.

I am about to change my house bank to lithium. After much analysis i have decided to isolate the Lithium bank. My AGM start bank will be still be charged by the engine alternators and AC shore / Gen set charger. The lithium will be charged by solar and AC shore power / Gen Set charger, but not the engine.alternators. The AGM setting on my Charles Marine 50 amp charger produces 14.4 v. This is within the allowable charge range of my 200ah Lithium batts.

I too am a bit skeptical about this product. Sorry.

A DC-DC charger (e.g. reputable Victron) comes to mind as a well-established way to join two different banks together when the chemistries differ. It is a 1-way configuration... configured for the target bank's charging profile.

The 30 amp Victron DC-DC charger is what we invested in for our boat.

I watch their YouTube channel, but was nervous about the initial connection. Maybe this device will alleviate that danger

MVDarlin said:

I am about to change my house bank to lithium. After much analysis i have decided to isolate the Lithium bank. My AGM start bank will be still be charged by the engine alternators and AC shore / Gen set charger. The lithium will be charged by solar and AC shore power / Gen Set charger, but not the engine.alternators. The AGM setting on my Charles Marine 50 amp charger produces 14.4 v. This is within the allowable charge range of my 200ah Lithium batts.

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So how will the Li get charged when you’re cruising?

sunchaser said:

So how will the Li get charged when you’re cruising?

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On my house bank I have combined lead and lithium. The starters for my engine uses 12 volt lead acid only.

The house Bank is direct charge via solar. The key to the combination of lead lithium is the BMS on the lithium. It will cut off the lithium at 14 or so volts before it over charges allowing the lead acid to continue accepting charge. The same is reverse when discharging. The BMS will cut off the lithium from the lead acid once you reached min voltage.

I also run an isolator from the alternator to the house Bank. So if underway the alternator will feed the house Bank. As described in the paragraph above, the BMS will shut down the lithiums once they Max charged allowing the lead acid to continue accepting charge from the alternator.

Combining lead & lithium batteries

Max1 said:

On my house bank I have combined lead and lithium. The starters for my engine uses 12 volt lead acid only.



The house Bank is direct charge via solar. The key to the combination of lead lithium is the BMS on the lithium. It will cut off the lithium at 14 or so volts before it over charges allowing the lead acid to continue accepting charge. The same is reverse when discharging. The BMS will cut off the lithium from the lead acid once you reached min voltage.



I also run an isolator from the alternator to the house Bank. So if underway the alternator will feed the house Bank. As described in the paragraph above, the BMS will shut down the lithiums once they Max charged allowing the lead acid to continue accepting charge from the alternator.

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When the BMS shuts down the LFP, what powers your house loads?

twistedtree said:

Anyone going down this path should know that the recently released ABYC spec for Lithium Ion batteries recommends against including different battery chemistries in the same bank. Lead batteries can short out and melt down, and it's not an uncommon occurrence. It's a safety concern because if a failing lead battery is connected to an Li-ion bank as it is in a hybrid, there is a massive amount of current that will get dumped into the failing lead battery. I'm not totally up to speed on all the considerations, but that's the key thing that I recall.


Also, ISO has a draft pre-standard much like ABYC's earlier TE-13 Technical Report. ISO flat-out prohibits hybrid banks.


Creating such hybrid banks has definitely been a popular approach, but anyone continuing to do so should do it knowing which direction the standards are pointing.

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Twistedtree presents the exact reason why mixing LFP and Lead is a bad idea. LFP batteries are capable of very high current discharge, and in combination with Lead if (when) the Lead batteries fail the LFP will contribute to and even cause a very dangerous situation - by dumping a huge amount of current into the failing battery.

When I was initially investigating a LFP house bank keeping a small Lead Acid bank in parallel with the LFP bank seemed like a great solution to avoid alternator and other charge source issues if the BMS dropped the LFP bank out of the system. Rod Collins (Marine-how-to) was kind enough to educate me on the downsides to such an arrangement.

I have not review the device suggested by the OP, but will be as I am curious on how they are proposing to make this a safe system choice.

twistedtree said:

When the BMS shuts down the LFP, what powers your house loads?

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Thats what I was wondering.

I went with the two Victron DC to DC chargers. Total 60 Amps. After one year, so far so good. The biggest thing is setting up all the parameters within the 2 Victron chargers and the charger/inverters. The values between the two can not be setup the same. The firmware!!

Hint on charging Li. The chargers should be setup only to turn on when the voltage drops to the value that is set in the charger. For me, charge Voltage 14.1, normal voltage is about 13.4 and the charger will turn on around 12.9.

Now I take the boat from Boston to just the other side of the Cape Cod Canal. A 6 hour run. Turn on the genset and the charger/inverter starts charging and than goes into standby roughly 10 minutes later. I was waiting for the amps to slowly drop off like a AGM battery would. Now days to week went by between the install/ setting up the values and my trip. You can't remember everything! I made a phone call thinking something was wrong. Nope, all good.

On my last boat I could see the voltage and amps that the charger was putting out. It was a lot more constant due to the house loads.

Now 30 minutes before leaving the slip. I turn the charger off and on. This turns the charger on and helps in topping the batteries off. Its really not needed, but I feel better knowing their closer to fully charged when leaving the slip.

Several responders have mentioned Rod Collins (marinehowto.com) recognizing his expertise in marine battery systems. And, there are many references to AGM batteries. How many of you are aware of the fact that Rod is NOT a fan of AGM batteries? He has a long article on his website that explains why. Except for not needing to water the batteries, AGMs' offer virtually no advantage over flooded batteries, and at double (or more) the cost. I know, not common knowledge about AGMs. Meanwhile, AGMs must be recharged to 100% often lest they be damaged, whereas flooded batteries much less often. I suggest you read Rod's treatise before sending slings and arrows my way.

I tryed looking up AGM batteries on marinehowto.com on why Rod is not a fan of AGMs. I could not find it. A link would be nice.

From my experience, I had 5 AGMs from Oddessy that lasted at lest 11 years. Than I sold my boat with them. For me, peace of mind knowing that I had a batteries that just wanted to keep going was great.

I never charged them during winter months. Every spring I did a load test, all good. A little pricey, but for over 11 years of good service I am happy.