AMP hours is AMP hours? Flooded vs LiPO4

[DaveTM]

This is a battery question.....so it's electric.....and I gotta have it spelled out to me.

So, if a Trojan T-150 is 100-hr rate is 250, and it's 20-hr rate is 225, how do I make this "equivalent"?

And a LiPo4 battery is rated 50 amp-hr.....what is the magic formula to put all of this on a common ground so I can compare these?

[cgtech]

Lead acid batteries produce 57% of their "20 hour rate" when discharged at a 1 hour rate. Or at least that's what I read on the internet. Lipo are rated at a 1 hour rate.

[JohnnieB]

Originally Posted by DaveTM

This is a battery question.....so it's electric.....and I gotta have it spelled out to me.

So, if a Trojan T-150 is 100-hr rate is 250, and it's 20-hr rate is 225, how do I make this "equivalent"?

And a LiPo4 battery is rated 50 amp-hr.....what is the magic formula to put all of this on a common ground so I can compare these?

Back in 1897 (when we were in nappies ), a guy named Wilhelm Peukert presented the fact that the higher the amps rate drawn from a lead-acid battery, the less of the stored chemical energy could be obtained. https://en.wikipedia.org/wiki/Peukert%27s_law

Attached is a chart from US battery showing the effective storage capacity for many of their batteries at various discharge rates.

If you look at the US 250E XC about in the middle of the 6V batteries, you'll see it has the storage capacity of 225AH when discharged at the C/20 (20 hour rate) rate of 11.25A and only 155Ah when discharged at the C/1 ( 1 hour rate) rate of 225A. A 225AH T-105 will have similar storage capacities at similar hour rates.

According to the Wikipedia article, a Peukert factor of 1.0 is the ideal battery that has the same storage capacity no matter what the amp draw is and generic lead-acid batteries have a Peukert factor of about 1.44. On the other hand, the Peukert factor of a Lithium battery is close to 1.0 so its storage capacity is about the same with light or heavy loads.

You might be able to dig out a formula from the Wikipedia article, but I'd just use the US Battery chart to find the AH rating the Lithium batteries being compared are rated at. In fact, I'd most like just use the 3hr rate for 6V and 8V Lead-Acid batteries for a storage capacity comparison.

-------
Also along these lines, the Peukert factor determines the voltage drop under load. The more amps you draw from a lead-acid battery the more the battery voltage drops, but the voltage of a Li battery stays about the same under heavy load.

[DaveTM]

Thanks Johnnie. I've set up a spreadsheet to do some calculations (It's a CPA thing) and my understanding is getting close.

However, my 3 grandsons are here until Memorial Day and my thinking is difficult with the DB rating in my house of REALLY FREAKING LOUD!!

I love 'em when they come......I love 'em when they go!!

[JohnnieB]

Originally Posted by DaveTM

Thanks Johnnie. I've set up a spreadsheet to do some calculations (It's a CPA thing) and my understanding is getting close.

However, my 3 grandsons are here until Memorial Day and my thinking is difficult with the DB rating in my house of REALLY FREAKING LOUD!!

I love 'em when they come......I love 'em when they go!!

Not a CPA, but I've been known to do a few spreadsheets every now and then.

The noise the grandkids make just enhances the solitude of the woods.....

----------
Something I forgot to mention is the usable storage capacity of lithium batteries is higher than lead-acid.

We typically limit ourselves to only using about 50% of the storage capacity of a lead-acid battery and, as I understand it, about 80% or so of the storage capacity of lithium batteries can be used without adversely affecting it.

This is all hearsay, but from what I've read here and other places is that there is a danger of the lithium batteries catching on fire (Thermal runaway) if they are overcharged or over-discharged and if the cells in the pack are not well balanced, getting one or more cells into a dangerous condition if you charge the pack too high or discharge it too low. By not charging above 90% or discharging below 10% largely avoids that issue. I've also heard of a 20% top and bottom buffer being used. Apparently there is some device called a BMS (Battery Management System???) that mitigates the problem. Also, I've heard of Top Balancing and Bottom Balancing the pack to help with the issue. These are areas that I need to learn more about.

One thing is for sure, reducing the cart weight by several hundred pounds will improve your cart's ability to get you to your hunting spot and back.

[cgtech]

This is the reason I like the LiFeP04 chemistry. They are very tolerant of abuse, and when you push them too far, they just stop holding power and smell a little funny.

[DaveTM]

Originally Posted by cgtech

This is the reason I like the LiFeP04 chemistry. They are very tolerant of abuse, and when you push them too far, they just stop holding power and smell a little funny.

I have a B-I-L like that.....except he smells funny all the time.


My reason of wanting.....or considering to go with the LIpo4 is for the distance it allegedly will get. Hunting in temps from 20 to 35 degrees takes a toll on the ability to travel longer distances. Especially if I'm going up a mountain (if you live in WV......you know what a mountain is)