Hey guys. I’ve been living in the dinosaur ages when it comes to lithiums but finally gonna make the switch in my tracker 185. Going to LiTime batteries powering my fortrex(soon to be ultrex) 80lb. So I’ll go with two bluetooth 100ah batteries. My big question…..are people also running lithium for a cranking battery?

I’ve always heard you don’t want lithium for cranking because you don’t know when the battery is getting drawn down like an sla. But I see now they make specific cranking batteries, so apparently it’s a thing. LiTime makes a 20ah, 800cca cranking battery. And I’m only equipped with a 90hp Mercury two stroke. Is it still best practice to stick with sla for cranking or is that a thing of the past?

I went lead for the cranking battery just for price reasons. I hadn’t seen the little LiTime you mentioned or i might have done that since the price is about the same. Just don’t put the boat electronics on that same little lithium cranking battery. Put them on a dedicated 12/100.

If you're going with an Ultrex, I highly recommend going with the Ultrex Quest if you can fit it in the budget. You can run the Ultrex Quest just fine on 24v. It is about a 1/2 mph difference on the top end with 24v vs 36v and pretty much the same everywhere else.

As for the outboard with a Lifepo4 cranking battery? Conventional wisdom usually points to NO unless you have a certain newer outboard said to be compatible. If you're a risk taker, I would at least price the price the parts that are likely to need to be replaced so that kick to your tender parts won't be altogether shocking.

1 hour ago, casts_by_fly said:

I went lead for the cranking battery just for price reasons. I hadn’t seen the little LiTime you mentioned or i might have done that since the price is about the same. Just don’t put the boat electronics on that same little lithium cranking battery. Put them on a dedicated 12/100.

Here’s the wild thing: if I replace both deep cycle with the mini 100ah, the cranking battery with a lithium cranking battery, then I can actually fit a 3rd 100ah on the rear compartment just for the graphs! Side question….you think the bilge and aerator would be fine still on the 20ah cranking lithium or would I need to swap those over with the graphs?

29 minutes ago, Big Hands said:

As for the outboard with a Lifepo4 cranking battery? Conventional wisdom usually points to NO unless you have a certain newer outboard said to be compatible. If you're a risk taker, I would at least price the price the parts that are likely to need to be replaced so that kick to your tender parts won't be altogether shocking.

I’m thinking I’ll contact Mercury directly to check on running a lithium with a 2001 motor

10 minutes ago, Swimbaitstud said:

I’m thinking I’ll contact Mercury directly to check on running a lithium with a 2001 motor

2001?

99.99999% chance that it'll be a "NO".

12 minutes ago, Swimbaitstud said:

Side question….you think the bilge and aerator would be fine still on the 20ah cranking lithium or would I need to swap those over with the graphs?

Depends on how much you'll need to run them. Bilge? hopefully on rare occasions.

Aerator, on a heavy use day, it's hard to say it'll be enough. You really need to do the math with how many amps those items will draw. Multiple graphs starts to be a concern, especially if they are medium to large screens.

Check out Redodo for some high capacity Group 31 size batteries (up to 165 ah). Two of those and you could run your Ultrex, and all of your other 12v accessories. You can wire the two 12v lifepo4 batteries in series for 24v for a 2v trolling motor, and at the same time, tap 12v off of one or both of those same batteries for ALL of your other accessory needs. Then have a lead acid cranking battery just for that purpose.

I've been running a dual purpose LiFePO4 from Florida Lithium for 2 years now with no issues. It's also my house battery (stereo, electronics, lights) and have zero interference. The lowest I've run it was 72% fishing with all my graphs on for 8 hours. They say they are compliant with Mercury outboard specs, which is what I have (2021 Mercury v6 200HP 4 Stroke).

FloridaLithium

12V 105ah Dual Purpose LifeP04 battery

Florida Lithium's advanced performance dual purpose Lithium batteries provide the best of both worlds! Our 105ah battery features an upgraded 150Ah BMS, providing maximum deep cycle performance AND 80

This can be a deep rabbit hole and it depends on how deep you want to go, being an old engineer like everything I tend to go deep to try to understand everything. I'm a huge LifePo4 (LFP) fan. It's a very stable chemistry and when made properly they should last a very long time. My setup is rather complicated since I do not have shore charging so I need my configuration needs some additional electronics that allows me to charge ALL the batteries when the big engine runs. I'm sure you have read most of the highlights for LFP but they are superior (again when made properly) than lead acid or agm. One of the major things that I believe most folks overlook is that they have different charging profiles, you need a special charger for them and most of the plug and play chargers while they say the support LFP they may not be a good fit for your batteries. One of the main advantages to LFP is that they have a BMS that manages the 4 cells in the battery (if talking 12v batteries). That BMS controls all of the functions and is the brain and depending on how it is programmed will also control the charging profiles. Most LFP chargers want to charge to 14.x volts and what usually ends up happening is the BMS will just cut off charging when one of the cells hits 3.5x voltage. These batteries can balance at higher voltages but its a slow process so what happens over time is the cells become more unbalanced. Again LFP has such a long life and capacity that it will not impact things for a very long time. See I am already going down a bunny trail, lol...

Anyway, they make LFP cranking batteries that should meet most mfg specifications, the one thing that you may want to think about is depending on how you are going to wire things up you may want a shunt or something else on the batteries to know what the voltage is and that will allow you to derive the state of charge. What's nice about LFP batteries is you get the full capacity, if it states 20ah then you have 20ah, lead acid/agm etc you can cut that number in half.

I did not go with a LFP cranking battery since my new boat came with a brand new agm cranking, but I have 3 LFP, 2 for 24v trolling and 1 for house which runs all the electronics. Depending on the LFP types one of the only gotchas is that they have a low temperature cutoff, meaning that the BMS will not allow you to charge them when the temps are below a certain temp. Each brand like I said has a value that they use for low temp cutoff and again it only applies to charging, you can use the batteries and they will work and actually heat the batteries up but if you try to charge them when its cold and below the value the bms will not allow since you can damage them when below 32. Just something to keep in mind, some of the batteries have heated wraps that turn on below freezing to keep them above the temp but just something else to consider.

Oh well, if you have any questions about setup balancing etc let me know, I may not have an answer but I do know some good forums that deal with the batteries that probably do...

8 hours ago, bishoptf said:

This can be a deep rabbit hole and it depends on how deep you want to go, being an old engineer like everything I tend to go deep to try to understand everything. I'm a huge LifePo4 (LFP) fan. It's a very stable chemistry and when made properly they should last a very long time. My setup is rather complicated since I do not have shore charging so I need my configuration needs some additional electronics that allows me to charge ALL the batteries when the big engine runs. I'm sure you have read most of the highlights for LFP but they are superior (again when made properly) than lead acid or agm. One of the major things that I believe most folks overlook is that they have different charging profiles, you need a special charger for them and most of the plug and play chargers while they say the support LFP they may not be a good fit for your batteries. One of the main advantages to LFP is that they have a BMS that manages the 4 cells in the battery (if talking 12v batteries). That BMS controls all of the functions and is the brain and depending on how it is programmed will also control the charging profiles. Most LFP chargers want to charge to 14.x volts and what usually ends up happening is the BMS will just cut off charging when one of the cells hits 3.5x voltage. These batteries can balance at higher voltages but its a slow process so what happens over time is the cells become more unbalanced. Again LFP has such a long life and capacity that it will not impact things for a very long time. See I am already going down a bunny trail, lol...

Anyway, they make LFP cranking batteries that should meet most mfg specifications, the one thing that you may want to think about is depending on how you are going to wire things up you may want a shunt or something else on the batteries to know what the voltage is and that will allow you to derive the state of charge. What's nice about LFP batteries is you get the full capacity, if it states 20ah then you have 20ah, lead acid/agm etc you can cut that number in half.

I did not go with a LFP cranking battery since my new boat came with a brand new agm cranking, but I have 3 LFP, 2 for 24v trolling and 1 for house which runs all the electronics. Depending on the LFP types one of the only gotchas is that they have a low temperature cutoff, meaning that the BMS will not allow you to charge them when the temps are below a certain temp. Each brand like I said has a value that they use for low temp cutoff and again it only applies to charging, you can use the batteries and they will work and actually heat the batteries up but if you try to charge them when its cold and below the value the bms will not allow since you can damage them when below 32. Just something to keep in mind, some of the batteries have heated wraps that turn on below freezing to keep them above the temp but just something else to consider.

Oh well, if you have any questions about setup balancing etc let me know, I may not have an answer but I do know some good forums that deal with the batteries that probably do...

I appreciate all that info, and everyone else’s as well!

The sad conclusion is, I called Mercury and they said definitely not compatible with a 2 stroke of that age and that they really only recommend lithiums for newer 4 strokes. Sooooo…..I’ll probably just end up going with an AGM once my sla battery dies. Thanks again guys!

The issue using a lithium as a starting/cranking batter I think is the CCAs needed.

@gim - the LiTime we’re talking about will do 1200 CCA. The battery chemistry isn’t the limiting factory it is the build quality of the wiring and BMS that limits the cranking amps. Now that big motors are being rated for LiFePo you’ll see more and more come along.

1 hour ago, casts_by_fly said:

@gim - the LiTime we’re talking about will do 1200 CCA. The battery chemistry isn’t the limiting factory it is the build quality of the wiring and BMS that limits the cranking amps. Now that big motors are being rated for LiFePo you’ll see more and more come along.

Yup plenty of cranking amps. I think a major problem is the charging system of your motor. Some have a stator and some have an alternator. And the issue is that you’re trying to charge your lithium battery with a running motor that’s not capable of charging lithium. It would be like charging your lithium with an sla charger