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Open Roads Forum  >  Tech Issues

 > Lithium cost keep dropping!

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NRALIFR

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Posted: 11/05/21 07:04am Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

Just finishing up my first 280ah pack, still need to torque all the connections, trim the all thread and add acorn nuts.

Eve 280ah 12volt cell


What is the form factor of the complete unit? The battery box in my camper will accommodate a single group 31 battery, and I currently have a VMAX agm. When I replace it, I’m going to be looking for a lithium group 31 with the highest AH rating. The highest group 31 I know of currently is around 155AH with BMS.

[emoticon][emoticon]

BFL13

Victoria, BC

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Posted: 11/05/21 08:32am Link  |  Quote  |  Print  |  Notify Moderator

NRALIFR wrote:

S Davis wrote:

Just finishing up my first 280ah pack, still need to torque all the connections, trim the all thread and add acorn nuts.

Eve 280ah 12volt cell


What is the form factor of the complete unit? The battery box in my camper will accommodate a single group 31 battery, and I currently have a VMAX agm. When I replace it, I’m going to be looking for a lithium group 31 with the highest AH rating. The highest group 31 I know of currently is around 155AH with BMS.

[emoticon][emoticon]



With LFP no gassing you can carry them anywhere, so the TC battery box size is not a limitation. Routing the wires might be the only factor.

Big lesson in choosing a single 100AH battery that can run the inverter/microwave was you still need to run the furnace etc, so 100AH is just not enough for a weekend off grid.

You need two batteries, which means twice the already high cost if LFP (although reducing as noted) and a place to put them. Good thing is they can go anywhere, including inside where it is warm, so that leaves the cost.

Even better if you can roll your own for more AH at less cost---except drop ins would let you place each of two batts in different locations wired in parallel instead of all cells in one box. Depends on your RV layout what is possible and your budget.

Main thing is you are not stuck with the existing battery location.


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Gjac

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Posted: 11/05/21 09:05am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

NRALIFR wrote:

S Davis wrote:

Just finishing up my first 280ah pack, still need to torque all the connections, trim the all thread and add acorn nuts.

Eve 280ah 12volt cell


What is the form factor of the complete unit? The battery box in my camper will accommodate a single group 31 battery, and I currently have a VMAX agm. When I replace it, I’m going to be looking for a lithium group 31 with the highest AH rating. The highest group 31 I know of currently is around 155AH with BMS.

[emoticon][emoticon]



With LFP no gassing you can carry them anywhere, so the TC battery box size is not a limitation. Routing the wires might be the only factor.

Big lesson in choosing a single 100AH battery that can run the inverter/microwave was you still need to run the furnace etc, so 100AH is just not enough for a weekend off grid.

You need two batteries, which means twice the already high cost if LFP (although reducing as noted) and a place to put them. Good thing is they can go anywhere, including inside where it is warm, so that leaves the cost.

Even better if you can roll your own for more AH at less cost---except drop ins would let you place each of two batts in different locations wired in parallel instead of all cells in one box. Depends on your RV layout what is possible and your budget.

Main thing is you are not stuck with the existing battery location.
I thought that 100 AHs of LI was equivalent roughly to 210 amp hrs of lead acid GC batteries because you only run the GC batteries down to 50% whereas you can run the LI down to 0. My my 2 6v GC batteries last me 7 days before they are at 50% SOC, everything being equal won't 100 AH LI do the same? Would the LI equivalent last any longer running down to 0 than the 2 6v GC batteries running down to 50%?

time2roll

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Posted: 11/05/21 09:27am Link  |  Quote  |  Print  |  Notify Moderator

Gjac wrote:

I thought that 100 AHs of LI was equivalent roughly to 210 amp hrs of lead acid GC batteries because you only run the GC batteries down to 50% whereas you can run the LI down to 0. My my 2 6v GC batteries last me 7 days before they are at 50% SOC, everything being equal won't 100 AH LI do the same? Would the LI equivalent last any longer running down to 0 than the 2 6v GC batteries running down to 50%?
Yes although the issue is 2x GC2 at 49% is still 12 volts. Lithium at zero cuts out completely. So a bit of wiggle room if you go beyond 50% on the GC2 that does not exist in the Lithium. I recommend going minimum 150 Ah lithium for this reason. And 200w solar should help too if you want to stick with 100. If you roll your own lithium, the 280 size is popular and priced well.


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BFL13

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Posted: 11/05/21 09:54am Link  |  Quote  |  Print  |  Notify Moderator

Depends! [emoticon]

Relion says:

"More Usable Capacity 25-50% more capacity than lead-acid equivalent."

Many say 100% is usable with LFP, but many users here like doing 20-90s for 70% range in real life, so that compares with 50-90s using 6s at 40% range. You could do 40-90s at 50% range with your 6s too.

70 is 30 more than 40 and 30 is 75% of 40.
70 is 20 more than 50 and 20 is 40% of 50.

You also have "inverter usable" vs "furnace usable". The LFP stays above inverter alarm 11v to a lower SOC than 6s do. But you can go lower with the 6s and still run the furnace even though you can't do inverter anymore at that lower SOC.

Reisender

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Posted: 11/05/21 12:13pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Depends! [emoticon]

Relion says:

"More Usable Capacity 25-50% more capacity than lead-acid equivalent."

Many say 100% is usable with LFP, but many users here like doing 20-90s for 70% range in real life, so that compares with 50-90s using 6s at 40% range. You could do 40-90s at 50% range with your 6s too.

70 is 30 more than 40 and 30 is 75% of 40.
70 is 20 more than 50 and 20 is 40% of 50.

You also have "inverter usable" vs "furnace usable". The LFP stays above inverter alarm 11v to a lower SOC than 6s do. But you can go lower with the 6s and still run the furnace even though you can't do inverter anymore at that lower SOC.


That last explanation using the inverter and furnace makes a lot of sense and gives some clear context, at least for me.

Our new trailer that arrives in a couple or so months has two x 6 volt AGM batteries mounted under the bed. I had thought of switching it out for a battle born group 31 but I’ll see who’s it goes. The trailer comes with a 1200 watt inverter and is not hooked up to the microwave so I don’t see a huge load from it. Entertainment centre and a plug by the bed seems to be the only thing it’s hooked up to. Kinda wish it was hooked up to the microwave. That may be our first mod. We’ll see how it goes with the AGM’s but I’m not adverse to swapping it out with a battle borne.

Thanks for the explanation.

BFL13

Victoria, BC

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Posted: 11/05/21 01:25pm Link  |  Quote  |  Print  |  Notify Moderator

"The trailer comes with a 1200 watt inverter and is not hooked up to the microwave so I don’t see a huge load from it."

Some newer Rvs come with an inverter that is meant to run the res fridge they often come with now. Makes off-grid a challenge.

NRALIFR

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Posted: 11/05/21 02:03pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

NRALIFR wrote:

S Davis wrote:

Just finishing up my first 280ah pack, still need to torque all the connections, trim the all thread and add acorn nuts.

Eve 280ah 12volt cell


What is the form factor of the complete unit? The battery box in my camper will accommodate a single group 31 battery, and I currently have a VMAX agm. When I replace it, I’m going to be looking for a lithium group 31 with the highest AH rating. The highest group 31 I know of currently is around 155AH with BMS.

[emoticon][emoticon]



With LFP no gassing you can carry them anywhere, so the TC battery box size is not a limitation. Routing the wires might be the only factor……….

Main thing is you are not stuck with the existing battery location.


That’s true, but I’ve got a lot of work invested in improving the wires and accessories associated with the battery box so I’ll have the main battery in there regardless. That’s also where the Trimetric shunt and shutoff switch is. Just from a battery packaging standpoint, a drop-in group 31 with its own BMS and a lot of AH’s would work best for me.

About 9 months ago I was given these two U1 40AH lithium batteries that were salvaged out of hospital med-carts. I’ve cycled them in parallel about a dozen times with a 150 watt heater, and they’ll run it for about 6 hours. They’ve been sitting idle for a couple months now, and they’re currently at 13.18 volts @ 55°.

[image]

One of my winter projects is to install these inside the camper to be used solely for our 12v mattress heating pad. I’ll have them on a battery switch so they can be isolated from the main battery at night, and combined for charging. If the mattress heater flattens them, it won’t be a crisis.

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* This post was edited 11/05/21 02:28pm by NRALIFR *

Reisender

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Posted: 11/05/21 02:36pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

"The trailer comes with a 1200 watt inverter and is not hooked up to the microwave so I don’t see a huge load from it."

Some newer Rvs come with an inverter that is meant to run the res fridge they often come with now. Makes off-grid a challenge.


Yes I’ve seen that. But in this case it is a 3 way dometic.

I’ll wait to see how much power it uses. It’s a small trailer and the heat and hot water are hydronic, so no furnace blowers etc. It has a 163 watt solar panel on it as well with room for another similar sized unit. Until we get out there I don’t know what to expect.

Our first long trip we’ll be up your way. Starting in the Okanagan, following the gold trail up highway 3 to the coast, then a few weeks on the island starting in Victoria, tge. Up the island and the inside passage to Prince Rupert and then points unknown heading east on 16. We have a week or two of dry camping with friends as well but will probably bring a little 2 K propane generator with us. Should be fun.

Thanks for the info.

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