Lithium AH vs Lead Acid AH

[mattadata]

What is the best way to compare my Trojan T875s capacity to something like this lithium drop in replacement

Using the the Trojan 20 hour rate, each battery has 170 AH. So that is a total pack AH of 1020, and only 50% of that is usable, so that leaves 510 AH.

For lithium, it has a usable capacity of 100AH, so if we use 4 of them, it comes to 400AH.

Since I will be saving a weight with lithium, are these setups pretty equal in terms of capacity (distance)? Or is my logic flawed?

[cgtech]

I have done testing, and yes, 100ah lithium is about equal in delivered power as t875. That's not even factoring in the weight savings. Lithium cells are rated at 1 hour rate, not the deceptive 20 hour rate like lead acids. In my opinion, the "20 hour rate" thing is a total scam on users. But, your math is screwy, ah figures don't "stack up" on batteries wired in series. 4 12v 100ah cells wired in series equals 1 48v 100ah battery. If you took 4 12v 100ah batteries wired in parallel, you would get 12v 400ah.

[Sergio]

Since the batteries are in series, You do not add the AH together.

A T-875 pack for practical purposes is equivalent to a 70AH lithium pack.

[mattadata]

Good catch. Thanks.

[JohnnieB]

Trojan doesn't publish AH @ 1-hr rate for their batteries, but US Battery does.

Their 8V 170AH cart battery has 105AH at the 1-hr rate.

If only 50% is usable, there is 52.5AH available.

The Li battery is 100AH @ 1-hr rate, but how much of that is usable?
I don't know much about LI battery packs, but from what I've read they aren't fully charged or fully discharged because overcharging and over-discharging kills them. Again, from what I've read, some people charge to 90% and discharge to 10% while others only charge to 80% and discharge to 20%, so the usable range is either 80% or 60%, so 60AH to 80AH is available.

On the other hand, the 1-hr rate for the lead-acid battery is an amp flow of 105A, which is a pretty high for the average amp flow while driving a cart, so their true AH capacity is likely to be in the neighborhood of 55AH, or more.

Looks like the 48V 100AH Li pack linked to will provide more driving distance than the T-875 pack without taking the lighter weight into consideration.

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Question to those that know more about lithium battery packs.

Should the max battery amps slider in the XCT be set to the recommended max amp draw from the 100AH Li battery pack?

[mattadata]

Originally Posted by JohnnieB

The Li battery is 100AH @ 1-hr rate, but how much of that is usable?

Thanks JohnnieB. They state on their website you can use 100% of their rated capacity....so they must the extra capacity in their so they don't kill the cells.

[cgtech]

Max Amps slider SHOULD be set to cell "max instantaneous C" rating of the batteries. 10C (1000a) is common max on good 100ah cells.

[JohnnieB]

Originally Posted by cgtech

Max Amps slider SHOULD be set to cell "max instantaneous C" rating of the batteries. 10C (1000a) is common max on good 100ah cells.

Wow! I didn't realize the max instantaneous rate would be that high (10C).

Of course, the max for the Li batteries that'll fit in my budget will probably be in the 5C range.

Thanks for the info.

[scottyb]

We should start the JB lithium fund. Everybody you help donates $1 then in no time you'll be over-volting the D&D

[BobBoyce]

3C is a good setting for max currents up to 2 minutes, 10C is for impulse currents of 2 seconds or less. At least that is the ratings for my 100 AH cells.