How are AHs calculated on Lithium?

[toporanger]

I see all the posts asking what size battery to get and it got me thinking. Most AGM/Lead batteries AH are calculated at 20 amp. Most size 31 100ah batteries would last around 1 hour at the minn kota max amps on their TMs right?

Are lithium measured the same way? Or is lithium say 50 ah at 50 amps?

Just going through all these threads asking if say 50ah is enough and Im not even sure the batteries are being measured in their specs the same way. I cant find any lithium battery that lists say 50ah at 20 Amps like the AGM batteries do.

[CatFan]

Most batteries are tested at the 20 hour rate, not 20A.

[toporanger]

I think I understand thank you for the clarification.

But wouldn't that be even less load then? 20 hour rate for a 100 Ah battery would be 5 amps for 20 hours correct? Curious if lithium are measured that way also, especially considering that standard batteries get less powerful as they discharge.

[KandKKustomz]

Total amps usage divided by AH for lithium as you getting a true AH rating on a lithium.. a lead acid or agm is pretty much dead at 50 percent discharge.
So 10 amps constant ÷ 100 ah. 10 hours runtime. Give or take

[CatFan]

I think I understand thank you for the clarification.

But wouldn't that be even less load then? 20 hour rate for a 100 Ah battery would be 5 amps for 20 hours correct? Curious if lithium are measured that way also, especially considering that standard batteries get less powerful as they discharge.

Yes, most TM batteries are tested about 5A. That’s why I prefer to use RC which is a 25A discharge so is more like what you see in TM use. Discharge rate affects overall capacity.

AH measurement has a published standard, so it should be measured the same way for all batteries. But it wouldn’t be valid to compare the numbers between types because the discharge curve is different.

[bobcoy]

Topo, PM sent

[bobcoy]

I found a Will Prouse video on this subject. Not overly technical. It is however almost 20 min. Link:

[fishon396]

Interesting video

[KandKKustomz]

As I said above..

[Mechanic Bob]

AWESOME Video! Thanks for posting

[Lou r Pitcher]

A virgin lead acid battery such as an Odyssey and several other popular AGMs are not considered dead at 50% depth of discharge as the video incorrectly suggests.

They are considered to deliver a full life even when regularly using 80% of their full charge capacity before recharging.

[bryan535]

Total amps usage divided by AH for lithium as you getting a true AH rating on a lithium.. a lead acid or agm is pretty much dead at 50 percent discharge.
So 10 amps constant ÷ 100 ah. 10 hours runtime. Give or take

I'm pulling crankbaits with a 24 volt Minn Kota terrova. With 2 interstate batteries 100 ah I get 5 hours and they're dead. What would lithium do for me?

[bobcoy]

You should about double your runtime with 100 Ah Lithiums. Bob

[Smbass1]

Bobcoy is right, double the run time. I have spent a great deal of time researching lithium batteries (Lifepo4)and feel that Battle Born Batteries are one of the best for me. I’m not a sponsor or get anything for saying this, but I feel that any battery I use in my boat must be UL laboratory rated. This insures that it has been tested and proven safe. The above video by Will Prouse is very good and he has a lot on YouTube, some that explain lithium batteries in plain terms that most people can understand. I feel lithium batteries will over take lead acid batteries in the next few years and the price will come down.

[bobcoy]

A virgin lead acid battery such as an Odyssey and several other popular AGMs are not considered dead at 50% depth of discharge as the video incorrectly suggests.

They are considered to deliver a full life even when regularly using 80% of their full charge capacity before recharging.

I own an Odyssey 2150. It is a beast of a battery however still has lead acid rules
This is from the tech specs for that battery.
If the voltage is 12V or less (~35% SOC), the battery should be considered discharged and it must be charged prior first use.
OCV depends on the SOC and that dependency is given in the following table:

SOC	10%	20%	30%	40%	50%	60%	70%	80%	90%	100%
OCV	11.70 V	~11.82 V	~11.95 V	~12.08 V	~12.20	~12.32 V	~12.46 V	~12.58 V	~12.70	>12.84 V

Knowing OCV is important in avoiding deep discharge conditions and prolonging the battery operating life.

[bobcoy]

Lou this info is at: https://www.batteryequivalents.com/o...e-battery.html

Odyssey 31M-PC2150 AGM as Deep Cycle Marine Battery

Although battery's plates are relatively thin (to provide high currents), they are designed to withstand many charging-discharging cycles. For example, the battery can withstand around 400 charge-discharge cycles down to 80% of maximum discharge (80% DoD - Depth of Discharge, 20% charge left).
However, avoiding really deep discharges can significantly prolong the battery's operating life, as shown in the following table:

DoD%	10%	20%	30%	40%	50%	60%	70%	80%	90%	100%
Number of Cycles	~6000	~2200	~1300	~900	~650	~550	~470	400	~380	~320

As you can see at 50% it will still last much longer than at 80% DOD

[700Sam]

Will Prouse knows quite a bit and his videos are insightful, but useable AH, for trolling motor purposes it's not as huge an advantage for lithium as some may think.
Generally a 100ah lithium battery is 100ah at the 20hr rate and still pretty damn near 100h at the 1 hr rate.
A very good lead acid would be 100 AH at the 20 hr rate but around 40ah at the 1hr rate. Quite an advantage for the lithium. But in the real world it may not matter to you. If you regularly run your trolling motor at below half throttle , as I usually do, then the lithium advantage in useable AH is significantly less. Seeing as a 24v trolling motor at settings 1-4 is under 5 amps draw there's no advantage to lithium. If you run your trolling motor at low speeds. It's when you run and gun with your trolling motor that the useable AH of lithium become relevant.
A quality group 27 or 31 , at the 20hr rate is 115-140ah, would be pretty much equal to a 100 AH lithium. At low amp draws

[bassburch]

Gee, it sure would be nice if there were a standard usable AH test/calculation for ALL batteries regardless of composition.

[700Sam]

Gee, it sure would be nice if there were a standard usable AH test/calculation for ALL batteries regardless of composition.

The AH ratings and the way different rates they are calculated is fairly standard. Especially among the top brands of lead acids. They publish the AH ratings at 100hr, 20hr, 5hr etc..
It is in the "consumer arena" of battery brand's, as I like to refer to them as, that companies prey on the ignorance of consumers. Everstart batteries with their non standard AH calculation rates, and some marine lithium battery sellers fall into this category.

[bobcoy]

Sam, try watching and listenning to that video. It tells you something different. Bob