Lithium batteries

[lem55]

Hi all,
Quick question. I have asked some of the sellers, but have not gotten
a response. My question is can you mix battery amperage 100 amps with a
200 amp battery? Thanks Lee

[Tom_M1]

The best YouTube source is Will Prowse. He tears apart lots of batteries. Some of the cheaper LiFePo4 batteries have no low temp sensor. He checks this by dipping the sensor in ice water.

[StirCrazy]

wa8yxm wrote:

pianotuna wrote:

time2roll wrote:

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

You left out part of what I said which was there is no need to have heaters cut in at 50 f.

Warning.. there is a video where an engineer (We like to take things apart as well as build 'em) took apart a LiFePO4 battery.. Down to the cells (He did not take them apart)

The battery clearly claimed to have both low and high temp sensors and protection (High temp is to prevent thermal runaway and fires.. Rare with LiFePO4, common in some other LiOn types)

IT did have a high temp sensor.. But no low temp at all. He tested.
So just because it says it's low temp protected... Does not mean it is.

that was a store bought boxed one and what that engineer may have missed is that one temp probe can be used for both high and low limits.. when you build them yourself you know exactly what they have in them. high temp is mainly to prevent charging when the battery is to warm, not for thermal runnaway, as LifePO4 is highly resistant to that. in fact if you have ever seen the vido of what it takes to get a LiFePO4 to actualy catch fire, its pretty amazing..

[wa8yxm]

pianotuna wrote:

time2roll wrote:

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

You left out part of what I said which was there is no need to have heaters cut in at 50 f.

Warning.. there is a video where an engineer (We like to take things apart as well as build 'em) took apart a LiFePO4 battery.. Down to the cells (He did not take them apart)

The battery clearly claimed to have both low and high temp sensors and protection (High temp is to prevent thermal runaway and fires.. Rare with LiFePO4, common in some other LiOn types)

IT did have a high temp sensor.. But no low temp at all. He tested.
So just because it says it's low temp protected... Does not mean it is.

[time2roll]

pianotuna wrote:

time2roll wrote:

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

You left out part of what I said which was there is no need to have heaters cut in at 50 f.

There was no reason to talk about cold damage at 50f and above and yet there it just fell out.

May as well talk about 150mph speed rated tires for an RV.

[pianotuna]

time2roll wrote:

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

You left out part of what I said which was there is no need to have heaters cut in at 50 f.

[time2roll]

pianotuna wrote:
The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

Or the BMS stops the charging at low temperature and protects the battery until it can be determined why the heating system has failed.

[pianotuna]

S Davis wrote:
I only plan on 350 amps max so two 250amp BMS should cover it.

Yes dual 250'tis will be fine.

[pianotuna]

S Davis,

I chose to have a single switch for each battery bank. They are 1000 amps contacting and cheap.

If one should end up with burned contacts--the other can carry the load.

This is the format, but I'm not sure if it is 1000 amps contacting.



https://www.harborfreight.com/battery-cutoff-switch-63425.html?utm_source=google&utm_medium=cpc&utm_...

[S_Davis]

I only plan on 350 amps max so two 250amp BMS should cover it.

[pianotuna]

S Davis,

Looks like a good system.

There is no need to heat the batteries at 50 F.

Heat and cold are the enemy but Li can tolerate between -4 f to 140 f. I'd choose to shave off 14 f on both ends. i.e. 10F to 126 F.

The "cold" end is the dangerous part. Charge below that, and the batteries become expensive door stops.

The "hot" end, if exceeded does reduce cycle life.

I'm going to go out on a limb and say I think the BMS is a little bit small amperage wise. I'd be more comfortable with 300 instead of 250.

If you intend to "moochdock" and plug into 15 amp shore power, load support is a wonderful feature. I would never buy an inverter/charger without that feature.

[S_Davis]

pianotuna wrote:
S Davis,

So what are the components in your battery bank? Which battery management system?

Here is most of it I am adding a victron multiplus or a outback 3000 watt inverter.

600amp buss bars
4/0 DLO cable rated at 405amps from the 600a buss bar to battery switch
3/0 DLO cable from the batteries to the negative 600amp buss bar
600 amp dual bank battery switch/one on, both on or both off
3/0 DLO cable rated at 350amps from switch to each 280ah battery
300amp MBRP fuses on the positive of each battery
Battery buss bars rated at 300amps
Daly 250amp 4-S BMS

There is also a heating system on each battery with 25 watt silicone heat pads and fans, I keep them about 50 degrees F.

[S_Davis]

StirCrazy wrote:

S Davis wrote:

StirCrazy wrote:

S Davis wrote:
“I could just take the two 4s BMS off and use a 100amp 8s BMS that turns all 8 cells into one battery instead of two in parrelell.”

Except you just made a 24 volt battery with a 8-S BMS. Eight cells in series makes 25.6 volts. To stay at 12 volts and up the ah you would have to use a 4-S BMS and use parallel sets of cells. The draw back is not being able to monitor each cell in the battery.

true, you would be monitering groups of cells, but if you get quality cells that are matched, thats not an issue.

I still recomend building seperat batteries unless you want to go to a higher capacity and use a stepdown. but in my case I would do another 310AH battery and have two of them. so when I am using my camper I would just use one as thats 10 days camping with the furnace running 24/7, but for my 5th wheel I could have two in there and just move one back and forth between the 5th and the camper. one will give me more usable capacity than I have with my four 6V batteries so it will be fine when I am using the camper, but when I am going for a longer dry camping backwoods with the 5th wheel I can put the second in and double my capacity. being only 48lbs its not a big deal either.

That is what I did, I have almost 2000ah in seven 12 volt 280ah batteries. I have two in my work truck with a few spares.

I like thoes diaganal bus bars, where did you buy your cells from?

Steve

I cut and drilled them, it can be ordered in any amp rating. I got it at Galco, it is called Eri flex. The cells are EVE LF280N I purchased from Docan Power, they ran about $150.00 per cell delivered.

[pianotuna]

S Davis,

So what are the components in your battery bank? Which battery management system?

[StirCrazy]

S Davis wrote:

StirCrazy wrote:

S Davis wrote:
“I could just take the two 4s BMS off and use a 100amp 8s BMS that turns all 8 cells into one battery instead of two in parrelell.”

Except you just made a 24 volt battery with a 8-S BMS. Eight cells in series makes 25.6 volts. To stay at 12 volts and up the ah you would have to use a 4-S BMS and use parallel sets of cells. The draw back is not being able to monitor each cell in the battery.

true, you would be monitering groups of cells, but if you get quality cells that are matched, thats not an issue.

I still recomend building seperat batteries unless you want to go to a higher capacity and use a stepdown. but in my case I would do another 310AH battery and have two of them. so when I am using my camper I would just use one as thats 10 days camping with the furnace running 24/7, but for my 5th wheel I could have two in there and just move one back and forth between the 5th and the camper. one will give me more usable capacity than I have with my four 6V batteries so it will be fine when I am using the camper, but when I am going for a longer dry camping backwoods with the 5th wheel I can put the second in and double my capacity. being only 48lbs its not a big deal either.

That is what I did, I have almost 2000ah in seven 12 volt 280ah batteries. I have two in my work truck with a few spares.

I like thoes diaganal bus bars, where did you buy your cells from?

Steve