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time2roll

Southern California

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Posted: 11/30/22 03:37pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

wa8yxm and time2roll. I have great respect for both of you, but this time I have to disagree.

From Battle Born:

"Can I Connect 100 Amp-Hour Battle Born Batteries to the 270 Amp-Hour Battle Born Batteries?

Here at Battle Born Batteries, we offer two different lithium battery sizes: our 100 Amp-Hour BB100 series and GC2 series, and the new 270 Amp-hour batteries.

These two different sizes of batteries should never be connected. Any attempt to connect Battle Born Batteries of different amp-hours will result in a voided warranty.

You should only ever connect batteries of the same size."
I can agree with this disclosure. Primarily because the usage is unknown.

If pulling 100 or less amps there is no issue as the smallest battery can handle that. If expecting 300 amps there is a good chance the load will not be shared proportionally at all times causing a single battery to shut down from overcurrent.

Likewise even having the same size will not guaranty they all share the load equally. Put two 100ah in parallel and draw close to 200 amps and one could easily overload. I would recommend an overhead margin of maybe 20% to 30% of draw capacity in parallel. Four or more in parallel I recommend fusing each battery.

For typical RV use of lights and furnace... no issue.


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larry cad

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Posted: 11/30/22 03:52pm Link  |  Quote  |  Print  |  Notify Moderator

I suppose that if we have a friend we are visiting, who needs a "jump", sure ain't gonna get one through my jumper cables. That would put his battery and my battery in parallel! Look out, damaged battery or two coming up! And, "OH NO", their are two (count them) 2 alternators in that parallel mix too. Must be a slow day in RV.NET land

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S Davis

Western WA

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Posted: 12/01/22 12:44am Link  |  Quote  |  Print  |  Notify Moderator

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.

[image]

StirCrazy

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Posted: 12/01/22 06:14am Link  |  Quote  |  Print  |  Notify Moderator

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.

[image]


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

Steve


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pianotuna

Regina, SK, Canada

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Posted: 12/01/22 06:55am Link  |  Quote  |  Print  |  Notify Moderator

S Davis,

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


Regards, Don
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S Davis

Western WA

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Posted: 12/01/22 10:32am Link  |  Quote  |  Print  |  Notify Moderator

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.

[image]


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.

* This post was edited 12/01/22 10:55am by S Davis *

S Davis

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Posted: 12/01/22 10:51am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 12/01/22 11:01am by S Davis *

pianotuna

Regina, SK, Canada

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Posted: 12/01/22 11:53am Link  |  Quote  |  Print  |  Notify Moderator

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

Western WA

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Posted: 12/01/22 12:00pm Link  |  Quote  |  Print  |  Notify Moderator

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

pianotuna

Regina, SK, Canada

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Posted: 12/01/22 12:04pm Link  |  Quote  |  Print  |  Notify Moderator

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.

[image]

https://www.harborfreight.com/battery-cu........x5Jme3ESiNo1xlbvh3RYhRcmulYaAskbEALw_wcB

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