Lithium Battery Bank and Starter

[senorquill]

Has anyone gone all lithium for their battery battery bank to include the starter battery?

I want one bank wired in parallel with all Lithium batteries but I don't think it will push enough CCA to start the engine.

MQ

[Noah]

I am not an electrician nor a mechanic but my understanding is it takes very little cranking power to start our small engines. The main advantage for a dedicated start battery or reserve battery is the isolated/indepenant power source in a emergency.

[senorquill]

Thanks, does anyone know if Maximum Continuous Discharging Current of 100A would be able to start the engine? That what Renogy Lithium batteries push.

[senorquill]

I wrote Westerbeke and asked, and also have looked in the manual.

[mark_53]

I trying to gain some perspective on your question and I'm not an electrician but if you operate a 1100 watt appliance (microwave) through an inverter, you would draw approx 100amps (1100watts at 12v = 91.6amps plus some conversion loss).  Now you try and start the engine at the same time.  Seems like the answer would depend on the state of charge and capacity of the lithium battery.

As Noah suggested, I think you're missing the point of a start battery.

[senorquill]

I trying to gain some perspective on your question and I'm not an electrician but if you operate a 1100 watt appliance (microwave) through an inverter, you would draw approx 100amps (1100watts at 12v = 91.6amps plus some conversion loss).  Now you try and start the engine at the same time.  Seems like the answer would depend on the state of charge and capacity of the lithium battery.

As Noah suggested, I think you're missing the point of a start battery.

I don't think this is an accurate statement. Lithium's will push 100A all the way until they die (unlike AGMs), so SOC doesn't matter with a lithium; you're going to get 100A to the starter regardless. A West Marine 105ah battery will send Cold Cranking Amps at 800A and Marine Cranking Amps at 1000A to the starter. On cold days my engine struggles more to start than when it is 90 out, and that's with the AGM I have. So, the question is, what is the minimum Amps required to be sent to the starter? Can a lithium do it at 100A? Sounds like they might not be strong enough.

"The maim advantage for a dedicated start battery or reserve battery is the isolated/Independant power source in a emergency." Yes, it to use the house bank without depleting the starter bank so your starter battery is full when you go to crank. I want this but I want a house bank of Lithium's since they basically have twice the power as an 100A AGM due to DoD, last for 4000 cycles instead of 300, and have a life expectancy of up to 10 years.

The solution to this, from what i've been reading, is to have a completely independent starter battery. Then you use a 12v 40A DC to DC battery Charger and charge the starter battery from the 2x Lithiums. The only thing you lose is the ability to quickly switch to the emergency start that taps into the house bank. I guess you would just move the 2 battery terminal wires over if you had to, but then I would still be hoping that the 100A from the lithium's would start the engine...

Switching the house bank to lithium would nearly double my ability to run all my offshore gadgets.

[senorquill]

I also wouldn't start my engine with an inverter on running a microwave and all the lights and GPS/AutoPilot on. Just turn them off and start the engine.

[mark_53]

It doesn't take much to start our engines.  You should have no problem starting with a 800 CCA battery.  I used a 550 CCA 80ah FLA battery to start.  No problem.

[Ron Hill]

MQ : Now that the airlines prohibit carrying a Laptop with a lithium battery in checked luggage because of possible fire, I don't think that I would want Lithium batteries on my boat!!!

A thought

[Noah]

RON— Not the same "Lithium". Different chemistry. He is referring to LiFePO4 batteries, which are more and more common in boats. Not the same as the lithium Ion batteries found in cars,  computers, phones, and other electronic devices.  Lithium ion batteries can overheat and catch fire, while LiFePO4 does not.

[tmac]

I'm going to venture forth with my opinions on this subject even though some may not agree.  I'm right in the middle of reconfiguring my boat's battery and charging systems to incorporate LiFePO4 for the house bank.  My recommendations to MQ are as follows:

1.First, spend some more time educating yourself about incorporating Lithium.  As Maine Sail says, Lithium is not a drop-in replacement for lead acid.  There's more to consider than you see at first glance.  I'd recommend watching the video seminars on YouTube from Pacific Yacht Systems (Jeff Cote) on the subject (yes, I know, he's long winded, but there's good information in there.)  Also Maine Sail has several good write-ups, as well as Nigel Calder's extensive writings and his videos on YouTube.

2.One of the above authors made a good analogy, which was that LiFePO4 batteries are like marathon runners, and lead-acid starter batteries are like sprinters.  Starting an engine requires a sprinter – big push for a short duration.  This is not what LiFePO4 batteries are designed for.  They are good at providing a strong, steady output for long periods of time.  The three authors above all seem to agree that using a LiFePO4 battery as a starter battery on a regular basis is not recommended. 

3.You mentioned that you were going to have the DC to DC charger charging the starter battery from the house bank.  In my opinion, that's backwards.  Unless you are also using solar, the DC charger only comes into play when you are charging via the alternator.  When you crank the engine, you are only draining the starter battery by a couple of percent in most cases, unless your engine requires some serious maintenance. (This is why most internally regulated alternators have a VERY conservative charging profile – it only takes a few minutes to fully recharge the starter battery.)  So to me, it makes more sense to have the DC charger look to see when the starter battery has 13.6 V on it (i.e. it is being charged by the alternator), and draw from that side to also charge the house bank, which will likely be in more need of charging. The starter battery will be recharged in short order, and then the DC charger and alternator can focus on the house bank.

4.There are many misconceptions about Lithium batteries – especially the issue with flammability.  Maine Sail does a good job of putting this to rest (as does Nigel Calder), clarifying that the LiFePO4 battery is very different that the earlier Lithium Ion batteries that made the news so often.  The primary concern for fire with LiFePO4 would actually come from situations where a dead short in wiring occurred that would allow the battery to pump out vast amounts of current, melting the wiring.  However most of the batteries being sold today have battery management systems that would shut down the battery in these situations.  That BMS, combined with an appropriate Class T fuse in the main wiring configuration should greatly reduce this risk.  The other situation to guard against is using a 1/2/both switch and combining a heavily discharged starter battery with a fully charged LiFePO4 bank.  The large voltage difference would cause a big current spike, and again could lead to a wiring meltdown. In my configuration, I'm using a keyed switch hidden away from passengers that will allow me in an emergency use my house bank for starting the engine, but only after I first pull the fuse on the starter battery so that the two banks are never linked.

That's my nickel's worth.  Is it worth installing LiFePO4?  I think so – for nearly the same cost as replacing my 4 dying Trojan T-105's I'm getting about 220 amp hours, of which I can actually use about 175 AH on a regular basis (and more if I really need), whereas the Trojans gave me 420 AH, but I could only use about 35% of that on a regular basis or 147 AH (sometimes 200 AH if I pushed it hard, but you pay a price in longevity for that).  Not to mention the far longer lifespan for the LiFePO4.   And I can fit the two lithium batteries easily into the battery box, with enough room to also mount the DC to DC charger in there and do a nice, neat wiring job for my main unswitched bus, fuses, etc. 
OK – I've stepped down off my soapbox...

[senorquill]

I’m going to venture forth with my opinions on this subject even though some may not agree.  I’m right in the middle of reconfiguring my boat’s battery and charging systems to incorporate LiFePO4 for the house bank.  My recommendations to MQ are as follows:

1.First, spend some more time educating yourself about incorporating Lithium.  As Maine Sail says, Lithium is not a drop-in replacement for lead acid.  There’s more to consider than you see at first glance.  I’d recommend watching the video seminars on YouTube from Pacific Yacht Systems (Jeff Cote) on the subject (yes, I know, he’s long winded, but there’s good information in there.)  Also Maine Sail has several good write-ups, as well as Nigel Calder’s extensive writings and his videos on YouTube.

2.One of the above authors made a good analogy, which was that LiFePO4 batteries are like marathon runners, and lead-acid starter batteries are like sprinters.  Starting an engine requires a sprinter – big push for a short duration.  This is not what LiFePO4 batteries are designed for.  They are good at providing a strong, steady output for long periods of time.  The three authors above all seem to agree that using a LiFePO4 battery as a starter battery on a regular basis is not recommended. 

3.You mentioned that you were going to have the DC to DC charger charging the starter battery from the house bank.  In my opinion, that’s backwards.  Unless you are also using solar, the DC charger only comes into play when you are charging via the alternator.  When you crank the engine, you are only draining the starter battery by a couple of percent in most cases, unless your engine requires some serious maintenance. (This is why most internally regulated alternators have a VERY conservative charging profile – it only takes a few minutes to fully recharge the starter battery.)  So to me, it makes more sense to have the DC charger look to see when the starter battery has 13.6 V on it (i.e. it is being charged by the alternator), and draw from that side to also charge the house bank, which will likely be in more need of charging. The starter battery will be recharged in short order, and then the DC charger and alternator can focus on the house bank.

4.There are many misconceptions about Lithium batteries – especially the issue with flammability.  Maine Sail does a good job of putting this to rest (as does Nigel Calder), clarifying that the LiFePO4 battery is very different that the earlier Lithium Ion batteries that made the news so often.  The primary concern for fire with LiFePO4 would actually come from situations where a dead short in wiring occurred that would allow the battery to pump out vast amounts of current, melting the wiring.  However most of the batteries being sold today have battery management systems that would shut down the battery in these situations.  That BMS, combined with an appropriate Class T fuse in the main wiring configuration should greatly reduce this risk.  The other situation to guard against is using a 1/2/both switch and combining a heavily discharged starter battery with a fully charged LiFePO4 bank.  The large voltage difference would cause a big current spike, and again could lead to a wiring meltdown. In my configuration, I’m using a keyed switch hidden away from passengers that will allow me in an emergency use my house bank for starting the engine, but only after I first pull the fuse on the starter battery so that the two banks are never linked.

That’s my nickel’s worth.  Is it worth installing LiFePO4?  I think so – for nearly the same cost as replacing my 4 dying Trojan T-105’s I’m getting about 220 amp hours, of which I can actually use about 175 AH on a regular basis (and more if I really need), whereas the Trojans gave me 420 AH, but I could only use about 35% of that on a regular basis or 147 AH (sometimes 200 AH if I pushed it hard, but you pay a price in longevity for that).  Not to mention the far longer lifespan for the LiFePO4.   And I can fit the two lithium batteries easily into the battery box, with enough room to also mount the DC to DC charger in there and do a nice, neat wiring job for my main unswitched bus, fuses, etc. 
OK – I’ve stepped down off my soapbox…

Tom,

Thanks for the great advice. After a ton more research and contacting Renogy it sounds like the 100A a LiFePO4 produces will not work for engine crank ups, so I'll be going with a 2x 100Ah LiFePO4 House Bank and 1x 105Ah AGM starter bank with DC to DC charger option from the starter bank to the house bank.
------------
I've been watching Pacific Yacht Systems and that's where I got the idea for the DC to DC charger. You are correct about the DC to DC going from the Starter Battery to the House Bank, I miss spoke. That's is what I intend on doing. I have 200 watts of solar also, which I could re wire to the starter battery in the event the alternator craps out and I need the starter battery at full power.

MQ

[Noah]

Save some money and get a plain old flooded lead acid "maintenance-free" (sealed) battery for your starting battery. IMO, better choice than AGM for this purpose.

[senorquill]

Save some money and get a plain old flooded lead acid "maintenance-free" (sealed) battery for your starting battery. IMO, better choice than AGM for this purpose.

I'm going to be using one of my House Bank AGM for the starter bank, when I put the lithium's in, so don't have to buy another starter battery. I'll keep the other on board and charge every once in while to have an extra starter battery, until i feel comfortable with lithium's. Just bought all the stuff Renogy, i'll make a YouTube video of the install and follow up on how it worked. Should arrive next week.

Heading out this weekend, #### weather, so hopefully this parallel set up I did doesn't bite me in the ass.

[senorquill]

Gents, 

FYSA, from Westerbeke about the cranking amps for M25XP. Lithiums which supply 100A are not recommended.

Thank you for your inquiry. Westerbeke recommends an 800 to 1000 CCA starting battery be connected to your M25XP. The amount of starter motor amperage draw running that is posted in the technical manuals specification for the product is listed as 46 Amps, see page 33 (38 of the .pdf) of the manual found at this link 200155_rev2_m12-m35_technical_man.pdf (westerbeke.com) to our web site. However, it is important you understand that the amperage will vary based on the cable size, cable condition, cable length, starter condition, as well as the overall condition of the engine and the other circuitry in the engines DC electrical system. Also note that the in rush current draw may on initial start can easily be 5 to 10 times that amount, hence the 800 to 1000 CCA recommendation. For more help we suggest you consider seeking the advice of your local Westerbeke representative.

MQ