LiFePo vs Lead Acid - Knowledge and myths

[John in Santa Cruz]

Fwiw, I put a 4645 in my Casita 16, it was a easy drop in.

[Air Doug]

Originally Posted by Motoboss

How many batteries are you using to run the truck fridge? What model is it? Are you using any solar? What would consider the minimum requirements?

The TruckFridge is the TF130 undercounter one that gets put into Snoozy trailers. We run two 100Ah LiFePO4 batteries charged by a 9 amp DC/DC converter when driving, and by 100 watts solar when sunny. We supplement the solar with 100 watts of suitcase solar if needed. We ran with one battery for a while but found that we were cutting it close from time to time and having to run the generator. With two batteries and moving every few days we don't have to run the generator.

Using the Fantastic Fan definitely cuts into the power profile and the 3 amp charger can't keep up.

As an aside, we also use an ARB compressor-type freezer/fridge in our truck when towing our teardrop. It runs off of a 50Ah LiFePO4 battery charged by 100 watts of solar and 9 amps of DC/DC converter. It is basically a perpetual motion machine with that setup.

[John in Santa Cruz]

Originally Posted by Air Doug

...We run two 100Ah LiFePO4 batteries charged by a 9 amp DC/DC converter when driving, and by 100 watts solar when sunny. We supplement the solar with 100 watts of suitcase solar if needed. ....

a 100W solar panel is maybe 6 amps max. if those two batteries were 50% discharged, driving at 9 amps would take at least 12 hours of engine-on time to fully charge. on solar, even with both panels, you're not going to get a 50% charge in a single day, even mid summer perfectly clear day

[Air Doug]

Originally Posted by John in Santa Cruz

a 100W solar panel is maybe 6 amps max. if those two batteries were 50% discharged, driving at 9 amps would take at least 12 hours of engine-on time to fully charge. on solar, even with both panels, you're not going to get a 50% charge in a single day, even mid summer perfectly clear day

Yeah, you're right. The batteries never got fully charged when boondocking and we got charged up from time to time at campsites with power. I should have remembered and said that. Bottom line was that we never had a problem coming close to running out of battery in a month of driving and camping.

[jwcolby123]

Originally Posted by John in Santa Cruz

...

I was ready to go lithium for this, but was warned by an RV electrician, you can't charge them when they are very cold OR very hot, while good old flooded wet cell have a wider temp range, and while they lose capacity in the extremes, they don't stop working entirely until they get REALLY cold.

Yea, you hear a lot of things out there that aren't true.

[David Tilston]

Originally Posted by jwcolby123

Yea, you hear a lot of things out there that aren't true.

From the orignal post:

Originally Posted by jwcolby123

1) Charging them at temperatures below freezing will shorten their life.

[Alex Adams]

Yep, a lot of misinformation. Here are the temperature Specs for Battleborn's non-heated 100 Ah battery:

Operating Temp Range:
-4°F (-20°C) to 135°F (57.2°C)
Charging temerature range:
25 F (-3.9°C) to 135°F (57.2°C)

I WILL NOT be camping if it is under 25 F inside the trailer for any length of time or above 135 F! I currently remove my Lead Acid battery from my trailer when it is being stored so no biggie to remove it after I convert to LiFePO4. In fact it will be easier since my current battery is 60 pounds and the Lithium is 31 pounds.

One more thing not talked about, if you lose a cell on a lead acid battery it's finished. If you lose a cell on a Battleborn LiFePO4 battery, you lose some capacity but the battery still works. Very important if you are running a 12 volt compressor fridge.

[parmm]

Originally Posted by Alex Adams

Yep, a lot of misinformation. Here are the temperature Specs for Battleborn's non-heated 100 Ah battery:

Operating Temp Range:
-4°F (-20°C) to 135°F (57.2°C)

I WILL NOT be camping if it is under -4 F or above 135 F! I currently remove my Lead Acid battery from my trailer when it is being stored so no biggie to remove it after I convert to LiFePO4. In fact it will be easier since my current battery is 60 pounds and the Lithium is 31 pounds.

We don't camp at all, but we do travel using a RV Have pulled out of our home town leaving for Florida in February when it was -26F several years ago. We usually stop somewhere south of Winchester, Virginia for the first stop. It can be very cold there too. Not many camp grounds open in mid February, even down there. This was my whole reasoning for buying HEATED Battleborn batteries. They will be mounted in insulated battery boxes. Wish I could get them inside the Scamp 19 somehow, but don't think there is a good spot for them.

[Alex Adams]

Originally Posted by parmm

We don't camp at all, but we do travel using a RV Have pulled out of our home town leaving for Florida in February when it was -26F several years ago. We usually stop somewhere south of Winchester, Virginia for the first stop. It can be very cold there too. Not many camp grounds open in mid February, even down there. This was my whole reasoning for buying HEATED Battleborn batteries. They will be mounted in insulated battery boxes. Wish I could get them inside the Scamp 19 somehow, but don't think there is a good spot for them.

In that case, I would have the battery in the tow vehicle with me on a DC charger and I would power my 12 volt fridge via the 7 pin trailer connector. If its that cold, then the fridge would stay cold overnight when parked at the hotel. Still better than having to lug 60 pounds around.

[John in Michigan]

Our 23 lb lifepo4 batteries (each is 105 ah at 12 vdc) are hauled in the TV. Plenty of power when we need it. In winter it is sometimes below zero F when we head south. At our first overnight stop, we can put a battery in the trailer and switch on the furnace.

[parmm]

Originally Posted by John in Michigan

Our 23 lb lifepo4 batteries (each is 105 ah at 12 vdc) are hauled in the TV. Plenty of power when we need it. In winter it is sometimes below zero F when we head south. At our first overnight stop, we can put a battery in the trailer and switch on the furnace.

Come on John, tell us who makes a 23 lb, 105 ah, lifepo4 battery? 23 pounds and 105 ah is super impressive!

[Alex Adams]

Originally Posted by parmm

Come on John, tell us who makes a 23 lb, 105 ah, lifepo4 battery? 23 pounds and 105 ah is super impressive!

Prismatic cells can get you to 23 pounds. The only problem with them is the same as lead acid cells, you lose one and the battery stops working.

[Motoboss]

Originally Posted by John in Santa Cruz

Fwiw, I put a 4645 in my Casita 16, it was a easy drop in.

My original converter is a 25 amp, so the PD4635 IS an upgrade

[John in Michigan]

Per my post number 21, my Lion Energy UT 1300 batteries are 23 lbs each. Nice sturdy handles. LEDs indicate charge level. Purchased at Costco online (when available). Appears this battery is currently available for $689 at Costco. I was able to find it by google searching "Lion Energy Safari UT1300 - Special Order".

[John in Santa Cruz]

Originally Posted by Alex Adams

One more thing not talked about, if you lose a cell on a lead acid battery it's finished. If you lose a cell on a Battleborn LiFePO4 battery, you lose some capacity but the battery still works. Very important if you are running a 12 volt compressor fridge.

um, since those are 4 LiFePO4 cells in series (with BMS etc), at best you could bypass the dead cell, which would leave you with a nominal 3 x 3.6V = 10.8 volts when one dies and the other 3 are fully charged.. so I dunno how that is 'reduced capacity'. not much "12V" stuff will be happy below 11V.

[John in Santa Cruz]

Originally Posted by Alex Adams

Charging temerature range:
25 F (-3.9°C) to 135°F (57.2°C)
....

from the data sheets on a LiFePO4 battery maker (NexGen)...

LiFePO4 batteries can safely charge between -20°C to 55°C (-4°F to 131°F). However, at temperatures
below 0°C (32°F) the charge current must be reduced, until the temperature is >0°C (32°F), as follows:
1. 0°C to -10°C (32°F to 14°F) charge at 0.1C (10% of the battery capacity)
2. -10°C to -20°C (14°F to -4°F) charge at 0.05C (5% of the battery capacity)

C would be 100 A for a 100AH battery, so 0.1C would be max 10A, and 0.05C would be 5 amps. the normal recommended charge rate is 0.5C.

while I don't *PLAN* on camping in weather that cold, it happens, morning frosts in the spring, etc could easily get you down to 0C/32F. and I don't run my furnace while I'm driving, so going over a high mountain pass, when there's still freezing above 8000 feet or whatever? ditto, could easily get below 0C.

[Alex Adams]

Originally Posted by John in Santa Cruz

um, since those are 4 LiFePO4 cells in series (with BMS etc), at best you could bypass the dead cell, which would leave you with a nominal 3 x 3.6V = 10.8 volts when one dies and the other 3 are fully charged.. so I dunno how that is 'reduced capacity'. not much "12V" stuff will be happy below 11V.

Battleborn uses cylindrical cells that are hooked up as 30 cells parallel into a pack with 4 packs wired in series. So if a single cell fails in a pack, the pack will still put out the full voltage just at a reduced capacity. Hence your voltage never drops, just the Amp hour capacity.

https://www.youtube.com/watch?v=G5E30u-66VI

[redbarron55]

As long as the bad cell opens up and does not short out.

[AlanKilian]

Originally Posted by redbarron55

As long as the bad cell opens up and does not short out.

I don't know specifically about Battleborn, but the eBicycle community has started to use per-cell fusing so even if a single cell shorts, you just get reduced capacity, not reduced voltage.

And it doesn't start a cascading fire.

[jwcolby123]

Just an FYI, under normal circumstances, if you discharge most of the way down, your cells will gradually drift out of balance. Gradually as in over a year or so.

LiFePO4 batteries have a BMS or a "battery management system:. One of the jobs of the BMS is to prevent any individual cell of the "bigger" battery from overcharging, or draining too far down. The BMS will absolutely do that.

So if your battery gets "out of balance" then what happens is that the BMS will prevent further discharge (in that discharge cycle) because one cell is all the way depleted (you can't draw all the available power from the remaining cells) or turn off charging if one cell is charged higher than the others and it reaches maximum charge, thus you cannot "fully charge" the battery.

The point here is simply that
1) The process of "getting out of balance" is a gradual and relatively slow one.
2) If that does occur, then the result will be that you will no longer get the full capacity until re-balanced
3) The battery will not be damaged because that is the precise reason that a BMS monitors such things.
4) If the individual cells started out closely matched and were good cells, it will take relatively longer to become unbalanced. I.e. cheap cells get out of balance faster than quality cells.

BTW I recently read that the same thing can occur in Lead Acid batteries and in fact Flooded lead acid batteries are sometimes "balanced" by adding electrolyte to cells.

So yes, balancing is an important task of the BMS but it isn't something that needs to be freaked out about. And making sure that it can occur every six months or a year is just fine.