Is there advantage between running a 2-100ahr to 1-200ahr

[757driver]

Here. From LifeBlue data sheet for the 300 AH. Current on their website.

[Itinerant1]

Is that an old copy?


They must of updated/ improved their batteries since the initial introduction of them.

[757driver]

Originally Posted by Itinerant1

Is that an old copy?


They must of updated/ improved their batteries since the initial introduction of them.

Current on their website. Data sheets show version 3. They no longer list a High current, Low temperature battery.

[paul65k]

So back to the subject at hand...... yes 2 100A LiFePO4 batteries will typically have more amperage available than a single 200A battery...... even with the Lifeblue example 2 100A batteries (in series) can support 200A draw, likewise 4 100A batteries can support 400A vs (2) 200A batteries which would support 300A.

On the other hand, these have to be cabled properly to enjoy the total amps available..... there's always that

[BCam]

Will Prowse has reviewed several relatively inexpensive LiFePO4 batteries recently on his Youtube channel, complete with teardowns. He especially liked this one:

https://www.youtube.com/watch?v=SU86EJXcTMM

SOK also makes a 100Ah version.

I'm not sure I'd be too concerned about redundancy. It all depends on how far you plan on being from a battery store where you could pick up an inexpensive lead acid battery. You always have your starting battery and you toad, if you have one.

Some of the batteries he's negatively reviewed lack a low temperature charge shut-off. LiFePO4 batteries will be damaged if charged below freezing. They work better than traditional batteries at low temperature, it's charging that's the issue. Battle Born has introduced a heated battery to get around this issue.

Personally, I wouldn't buy a LiFePO4 battery that Will hasn't reviewed with a teardown. There are good reviews of other batteries on his channel.

[Phil G.]

Originally Posted by 757driver

Yes there is. For any given lithium battery manufacturer each of their batteries (a 100 AH model and a 200 AH model) will most likely have the same BMS and the same limit on the max amps it can deliver (ie 100 AH). The 200 AH battery can only put out 100 AH max without tripping the BMS. Two 100 AH batteries which can put out 100 AH each without tripping the BMS can give you a max of 200 AH max which now could run a microwave for a short period of time.

My lithium manufacturer actually cautions against this when choosing the number of batteries and their size.

Hmmm ... I thought the definition of the "Amp Hour" spec for batteries meant a current delivery rate capability of: 1 amp for 100 hours, or 100 amps for 1 hour - or any combination in between.

If so ... why wouldn't two 100 AH 12V lithium batteries wired in parallel deliver 1 amp for 200 hours, or 200 amps for 1 hour -> thus exactly matching one 200 AH 12V lithium battery that could deliver 1 amp for 200 hours, or 200 amps for 1 hour?

What in lithium battery electro-chemistry, construction, or other limitations ... would make the above not corrrect?

[757driver]

Originally Posted by Phil G.

Hmmm ... I thought the definition of the "Amp Hour" spec for batteries meant a current delivery rate capability of: 1 amp for 100 hours, or 100 amps for 1 hour - or any combination in between.

If so ... why wouldn't two 100 AH 12V lithium batteries wired in parallel deliver 1 amp for 200 hours, or 200 amps for 1 hour -> thus exactly matching one 200 AH 12V lithium battery that could deliver 1 amp for 200 hours, or 200 amps for 1 hour?

What in lithium battery electro-chemistry, construction, or other limitations ... would make the above not corrrect?

Because that 200 AH lithium battery may well have a BMS limiting its continuous output to 100 or 150 amps.

[Phil G.]

Originally Posted by 757driver

Because that 200 AH lithium battery may well have a BMS limiting its continuous output to 100 or 150 amps.

Why?

If so #1, doesn't that then effectively mean that the "200 AH" model is not capable of meeting the definition of what an Amp Hour rating is supposed to be?

If so #2, then one should always install two of the 100 AH lithium batteries instead of one of the 200 AH lithium batteries -> for AH current delivery reasons in addition to the 12V battery redundancy reason.

(I suspect that the reason for the 200 AH lithium BMS having to not meet the AH definition is a safety one ... to keep internal heat build up with heavy current draws under control.)

[Phil G.]

Originally Posted by twanger

I thought two 100 ah lifepo4 could output more amps than one 200. Is there no truth to that?

See Posts 20, 21, and 22 in this discussion thread. It appears that your information may be correct - two 100 AH LifePo4 12V batteries in parallel can output more amps to meet certain requirements than one 200 AH LifeP94 12V battery can.

I'm not sure, but this "may not" be the case with other RV battery types - such as with AGM batteries, for instance.

[757driver]

Originally Posted by Phil G.

Why?

If so #1, doesn't that then effectively mean that the "200 AH" model is not capable of meeting the definition of what an Amp Hour rating is supposed to be?

If so #2, then one should always install two of the 100 AH lithium batteries instead of one of the 200 AH lithium batteries -> for AH current delivery reasons in addition to the 12V battery redundancy reason.

(I suspect that the reason for the 200 AH lithium BMS having to not meet the AH definition is a safety one ... to keep internal heat build up with heavy current draws under control.)

I would agree. In most cases two 100 AH lithium batteries would be better than one 200 AH lithium battery. The reason for the amp limitation is cost. It costs more to install more robust mosfets and heavier wiring/components. Some put in components capable of the AH capacity of the lithium battery in terms of max continuous current, others don’t.

[757driver]

Originally Posted by Phil G.

See Posts 20, 21, and 22 in this discussion thread. It appears that your information may be correct - two 100 AH LifePo4 12V batteries in parallel can output more amps to meet certain requirements than one 200 AH LifeP94 12V battery can.

I'm not sure, but this "may not" be the case with other RV battery types - such as with AGM batteries, for instance.

Your right, it is not the same with other battery types. This is a quirk of lithium batteries and their internal BMS.

[Pianotuna]

Originally Posted by twanger

I thought two 100 ah lifepo4 could output more amps than one 200. Is there no truth to that?

No. It depends on the battery management system.


It is better for other reasons to have 1 200 amp-hour battery.

[aaurbane]

If you intend to take the lithiums with you for your next RV you'd have a better shot at putting the 100 ah batteries directly into the locations of the lead acids you're replacing. This doesn't matter if you always expect to have your lithiums in a new location.

[bigchick]

amp hours is a measure of capacity. so 2 100 AH batteries will deliver the same capacity as a single 200 AH battery. the difference is in the maximum current flow allowed by the BMS. the same bms may be used in both the 100 AH and 200 AH batteries. if so the 200 AH battery will only output the same instantaneous current and the 100 AH battery. two 100 AH batteries will have two BMS's involved and will output the twice the current as a single 100 AH battery. and even 100 AH batteries from different manufacturers may use different BMS's with different output specs.

one reason for using multiple batteries to increase the instantaneous output is if you need to have the batteries start a device such as a generator that require high instantaneous current.

the BMS may also limit the amount of recharge current going into the battery.