12V Lithium Cells for Boat Battery?

Kaivorth

New Member
Joined
Feb 3, 2021
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Any recommendations for 12v 100ah cells?

I'm looking to dual purpose these for my boat (both engine starting and trolling motor)
and I would also like to use this same battery for a battery backup solution for my house, when used with a pure sine wave inverter in the winter time.

That's kind of the only way I can justify this expense :)

I think most of the cells aren't rated for the high current starting a motor requires? I'm guessing under 100a draw, it's a 2 stroke 40hp motor.

Side note. I've been using a battery jump starter to start my boat motor. Is this a bad idea? It's been able to start my boat at least 10x without draining it. I disconnect it after it's running.
 

snoobler

Solar Honey Badger
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Welcome to the forum.

First, LFP is a bad choice for starter batteries unless specifically designed for it. Starter batteries provide current well above what typical LFP can safely discharge. Lead is very tolerant of huge currents with large voltage drops. LFP is damaged by it.

Electric motors have a surge current that is 4-10X the run current.

If you know the peak current, then you might be able to design something around it.

The jump starter is likely a different chemistry that is far more tolerant of high currents.
 

Bob B

Photon Sorcerer
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LOTS of information about this on this thread if you have time to read thru it. There is a lot of controversy over using lithium as a starting battery because once the battery is fully charged the BMS can suddenly disconnect it from the motor and risk damage to the charge system in the motor. There a protection devices that can be added to mitigate that problem.

There are quite a few on this thread that are doing it. http://www.bbcboards.net/showthread.php?t=982657
 

12VoltInstalls

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Personally, after 30 years of small boats, one lead acid marine starting battery treated well and kept maintained with a 40HP motor will last 5 years, maybe be ‘sufficient’ for 8. That makes a flooded lead battery fairly inexpensive....and dependable. And you never want your starting battery to run accessory nor ‘house’ loads.

In my own personal current build (19’ Starcraft gutted and rebuilt, 90HP) I will certainly have an isolated starting battery, plus two deep cycle group 27 lead acids. Solar maintained with probably just one 100W panel on the roof. Maybe 200W but I don’t think I’ll need that much power

Why? Group 27s are inexpensive and readily available everywhere at moderate cost, relatively light weight for easy transport, and - if you don’t deep discharge constantly - can last almost ten years.

(I actually ’fixed’ a pair of 10-year-old grp29 deep cycles by mistake when I just needed to have something to hook up to for a camper install of my own. The batteries were junk to me as they wouldn’t last a half hour walleye trolling anymore. I hadn’t gone and bought new batteries and they wound up being in place for a few weeks. When I got back to it I was amazed to discover they were at 13V+ and I used them for almost two years when age and neglect killed them (yes, check your water levels more often) and I bought three “Maxx” group 27s at walmartha)

I’m not saying lead acid is ‘better’ - I’m saying for small systems and wise use, the “higher cost over time” may actually be a worthwhile and reasonably small expense.

I see the goal in the boat. All above notwithstanding; will your lifepo battery withstand the vibrations and road-shocks that a lead battery will and can? At $80 for a grp27DC that probably won’t break anyway is it worth it to lifepo the boat?
 

Kaivorth

New Member
Joined
Feb 3, 2021
Messages
10
Ended up buying a ChargeX 100ah battery for $950.
It's overkill, but the lifetime warranty is nice, and I'll be dual purposing this as my house battery backup battery, and will be the starting/deep cycle battery for the boat.
 

Bob B

Photon Sorcerer
Joined
Sep 21, 2019
Messages
3,379
Personally, after 30 years of small boats, one lead acid marine starting battery treated well and kept maintained with a 40HP motor will last 5 years, maybe be ‘sufficient’ for 8. That makes a flooded lead battery fairly inexpensive....and dependable. And you never want your starting battery to run accessory nor ‘house’ loads.

In my own personal current build (19’ Starcraft gutted and rebuilt, 90HP) I will certainly have an isolated starting battery, plus two deep cycle group 27 lead acids. Solar maintained with probably just one 100W panel on the roof. Maybe 200W but I don’t think I’ll need that much power

Why? Group 27s are inexpensive and readily available everywhere at moderate cost, relatively light weight for easy transport, and - if you don’t deep discharge constantly - can last almost ten years.

(I actually ’fixed’ a pair of 10-year-old grp29 deep cycles by mistake when I just needed to have something to hook up to for a camper install of my own. The batteries were junk to me as they wouldn’t last a half hour walleye trolling anymore. I hadn’t gone and bought new batteries and they wound up being in place for a few weeks. When I got back to it I was amazed to discover they were at 13V+ and I used them for almost two years when age and neglect killed them (yes, check your water levels more often) and I bought three “Maxx” group 27s at walmartha)

I’m not saying lead acid is ‘better’ - I’m saying for small systems and wise use, the “higher cost over time” may actually be a worthwhile and reasonably small expense.

I see the goal in the boat. All above notwithstanding; will your lifepo battery withstand the vibrations and road-shocks that a lead battery will and can? At $80 for a grp27DC that probably won’t break anyway is it worth it to lifepo the boat?
A lot depends on how often you use your boat and how you treat the batteries in between.

A fishing guide I know told me he was lucky if he could get 1 year out of his lead acid batteries. He was on the water over 300 days a year and used them hard. At that time, he just used Walmart batteries because they had a good warranty and were everywhere. At that time, the lithium batteries for a boat was causing fires and he wanted nothing to do with them.

I haven't talked to him for a few years now, but I'd be willing to bet he now has LiFePo4 batteries .... at least for the trolling motor.

The problem I have experienced with lead batteries is that you suffer thru reduced capacity for a significant amount of the time you use them. For the trolling motor, most people don't worry about the batteries til the motor starts loosing power ..... well, at that point you are well beyond the 50% you should be using and have further reduced their capacity.

I don't know anyone who gets 10 years out of a lead battery in their boat unless it is just sitting connected to a battery maintainer.
 

12VoltInstalls

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The ten years comment was about using them to store power.
but I’ve never killed a battery in a year. Before solar a smart charger; the charge controllers these days are probably smarter than that.
now if you’re talking bass boat I don’t do that stuff. Not enough tee shirts and I don’t drink a lot of beer. :) But trolling motors can kill a battery bid not cared for.

Nevertheless, my old MFG Niagara would troll 1.8 mph 8 hours easy, and I got three or four years out of a group 29 DC battery before it shortened output time. And I abused the trolling battery in my view.
But I was only out 3?or 4 times/month, 6 if I were lucky.
 
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