Boat battery

[duckman18]

I think it’s about time to change the deep cycle out in my sled. I’ve just been running a 27 series deep cycle from Costco. It Powers a 55 pound thrust Minnkota electric motor. I use it for side drifting Rivers and duckhunting. What is the best set up out there for batteries? Is it worth stepping up to a lithium? I’m usually always running it on speed 3,4,5  so I tend to only get 4-six hours out of a charge on a new battery.

[CP]

Yeah, lithium is worth it.  LiFePO4 batteries have made lead acid obsolete.  Try one and you will never go back.

[hunthard]

What's the cost of these? I have the Les Schwab optima battery and they seem to last 8 years or so. The last one I bought was $250 I think.

[CP]

Looks like about $170 for a 50Ah.  A 50Ah should outperform any group 27 lead acid.

https://www.amazon.com/dp/B0BHHQTQRT/?coliid=I3KTIQXFWGBOHQ&colid=383QQYN24QZ61&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

[Skillet]

I agree with CP.  If you're fully discharging a trolling motor battery, LiFeP04 is going to be a major upgrade over lead-acid. 

There are still a few scenarios where lead-acid makes sense, but  they are getting rarer and rarer.

[Stein]

Only reason I would not go lithium is for high draw situations like starting engines and sometime pot pullers depending on the current draw.

[HUNTNORTHWEST]

Tagging

[Skillet]

Only reason I would not go lithium is for high draw situations like starting engines and sometime pot pullers depending on the current draw.

I wasn't aware this was a limitation of Li batt's.  If a high amperage draw is needed, does a Li batt get damaged or is it just unable to do the work compared to a lead-acid or AGM?

[CP]

Only reason I would not go lithium is for high draw situations like starting engines and sometime pot pullers depending on the current draw.

I wasn't aware this was a limitation of Li batt's.  If a high amperage draw is needed, does a Li batt get damaged or is it just unable to do the work compared to a lead-acid or AGM?

LiFePO4 batteries have a BMS (Battery management system) that is programmed to shutoff if at some high current.  If it is a good BMS, the battery isn’t damaged and can be restarted but that is their major limitation. 

A lead acid battery is a very good choice when you need a lot of amps for a short period of time and then you immediately recharge the battery (e.g., starting an engine).  But for deep cycling, they can’t complete with LiFePO4.

[Skillet]

Good to know, thanks for the explanation.

Are the BMS' hackable, or open source?

[CP]

Good to know, thanks for the explanation.

Are the BMS' hackable, or open source?

Not open source.  They may be hackable, but well beyond my skills to do so.  Programmed in firmware, so who knows what all is in there?

[Skillet]

Good to know, thanks for the explanation.

Are the BMS' hackable, or open source?

Not open source.  They may be hackable, but well beyond my skills to do so.  Programmed in firmware, so who knows what all is in there?

Probably a good fire starter if you didn't have the coding chops to figure it out 

[Woodchuck]

My BIL recently added this to his boat and is thrilled with results. Best price he found was from Hodge Marine in FL.
https://minnkota.johnsonoutdoors.com/us/shop/battery-chargers/board-alternator?v=101926#learn-more-anchor

[RockChuck]

Wow the price has really come down on lithium! Just make sure you have a charger capable of charging lithium.

[GWP]

It not only depends on the BMS, but also the amp output capability of the individual Lithium cell.
I have 18650 cells (cells that most battery packs are made from) that range from a max 4 amp output to max 20 amp output. That is the individual cell (like a single C cell battery for comparison), and that means the battery pack made from the 4 amp will not be able to put out as much amperage and will not have as much capacity.
Each battery can only put out the max amperage it is rated for. If you push the capacity of the build, the BMS will eventually cut it off for heat or overdraw to protect itself. It WILL turn itself back on once the conditions are back to normal.
There are individual Lithium cells rated for 200 amp output that are pretty scary power wise. 6 of those will easily start or jump start a car.
I built a 24V 75 amp LiPo4 120 cell pack for my trolling motor to replace a pair of 31 Lead Acids. Half the weight, power all day. Probably closer to 100 amp capability compared to a Lead Acid.
The best thing about the Lithiums is it is full power until it is dead. No power dropping off and turning the power up to maintain the same speed like a Lead Acid.