Lithium Battery Recommendation

[DT6]

Hi,

We pickup our 21C later this month and it will be "Lithium Ready". I am seeking some battery recommendations, especially with respect to the Battery Management System (BMS) and whether it includes low-temperature cutoff or not. Also, how important is the "Max Load Rating" (is this the same thing as "Load Power")?

Winter temps where we are in Oregon can get down to near zero (F) on a bad day, but certainly near 20F or less many times between December - March. So if I understand the technology correctly the lack of a low temperature cutoff could damage these if I leave the battery cutoff switch on the trailer "ON" and temperatures here drop below freezing?

John (in Santa Cruz) has recommended the SOK 206Ah and that seems to be a solid recommendation. https://www.sokbattery.com/products/...e-battery-pack

Alternatively, Ampertime, which has a decent reputation it seems, has a heated version but unless I'm missing something, that draws power to keep the battery at a proper temperature, whereas (I believe) the SOK will simply shutoff until the battery temp is warm enough to charge safely. https://www.amperetime.com/collections/ampere-time

I'm not sure which is the best alternative between the two, again assuming that a low-temp cutoff in the BMS is critical.

If the low-temp BMS is not critical, there are certainly less expensive alternatives.

Thanks!

[splitting_lanes]

I went with AmpereTime, but my area rarely gets to freezing and with the battery in the trailer I don’t need to worry about damaging it from charging it when it’s cold.

My short list of batteries is SOK and AmpereTime, with your location I’d go with a pair of SOK’s if you’re using a inverter, and a single SOK without an inverter. There’s many good batteries, and many good combinations, this is just my thinking.

If you fast-charge a LiFePO4 battery when it’s internal cells are frozen, you’ll permanently damage it. If you need power for an inverter you’ll need a BMS that can output enough to run it. I ran my AmpereTime at 170amps with the fridge and inverter running off it with a load.

[Sean Murry]

I went with Battle Born Batteries from Nevada. Work well for me. Their BMS does have a low temperature cut off.

[rubicon327]

Don’t rule out Bestgo…very well made and they have several sizes depending on what you are looking for. We have the 400AH version and it has served us well so far
https://www.electriccarpartscompany....-battery-packs
https://www.bestgobattery.com/

[chesaka]

I live in Alaska and wanted batteries that would still charge below freezing. I went with LifeBlue lithium low-temp batteries on the recommendation of AMSolar. They have an internal warming system that kicks in when temp goes below freezing. I haven't done any real cold weather camping yet. Other than that they work well. Nearly always reading 100%.

[DT6]

Hi Everyone,

I'm going to try and clarify my original question. I am really looking for advice on BMS low temp cutoff and Max Load Rating. While I appreciate the recommendations on batteries, I think I've got a pretty good set to select from. So I'm amending my original question to the following:

For whatever Lithium battery I select, I am seeking some recommendations/education with respect to the Battery Management Systems (BMS) and whether it should include low-temperature cutoff and how important it is to have that? Most of the sub $1K batteries do not seem to have that feature.
Also, how important is the "Max Load Rating" and is it the same thing as "Load Power"?

On our 19 that we just sold, I always had the battery cutoff switch under the dinette left in the ON position, but we had the two 6V 225Ah Lead Acid batteries and the inverter.

For the new 21, I've got the Inverter and two 190W solar panels along with the rest of the Lithium Ready setup from the trailer build. I don't want to have to go out and turn the battery cutoff switch to OFF when it gets too cold. There are a number of reasons, but for the most part it would be very easy for me to forget it is ON, then forget about it and maybe we take a trip out of town during the winter without the trailer and we get a cold snap wile gone. And I don't want to two 6V any longer as I may be using a bit more power than that from time to time. Sorry if my original post seemed to suggest I was seeking battery recommendations, and I do appreciate the comments. Thanks!

[rubicon327]

Unless you are always in warm weather I wouldn’t buy a battery without a low temperature cut off. Not worth the risk of damaging the cells and no one wants to babysit a battery all winter. Once lithium batteries are full they have a very slow self-discharge so if you aren’t using the trailer they will hold charge just fine especially with active solar. I recommend the batteries be inside the shell and if you need to charge them in cold weather you can easily temper the trailer with the propane furnace or electric heater. I installed an electric heater with digital thermostat just for that reason. We never touch our battery cutoff switch. Also with the way the factory solar is wired it is not disconnected by the battery shutoff switch so you will always have it trying to charge the batteries. The heated batteries by BattleBorn or ReLion are another option but they do use battery power to keep themselves warm.

As far as max load rating this should be the maximum current the BMS can handle. Our Bestgo battery has very clear information on what the battery can tolerate. I had certain needs to be able to run a mini-split A/C but your demands may be less. If you have questions it might be best to contact the battery mfr/retailer.

[DT6]

Originally Posted by rubicon327

Unless you are always in warm weather I wouldn’t buy a battery without a low temperature cut off. Not worth the risk of damaging the cells and no one wants to babysit a battery all winter. Once lithium batteries are full they have a very slow self-discharge so if you aren’t using the trailer they will hold charge just fine especially with active solar. I recommend the batteries be inside the shell and if you need to charge them in cold weather you can easily temper the trailer with the propane furnace or electric heater. I installed an electric heater with digital thermostat just for that reason. We never touch our battery cutoff switch.

Thank you, this is exactly what I was looking for. So the only decision it seems is to choose between Low-Temp Cutoff in the BMS or one that is self-warming - or both. Awesome.

[alanmalk]

To attempt to answer your other question about "Max Load".



There should be a very clear battery specification about "maximum discharge current", typically in amps. For example, my lithium batts say "max discharge current - 100 amps". This is the number that the BMS will supply and "should" cut off if you attempt to take more.


Obviously 100 amps is not enough to run the typical big inverter so most people use 2 batteries in parallel for a max current of 200 amps. Some larger lithium batteries are designed for 200 amps or more.

[John in Santa Cruz]

on my double-insulated 21C, the batteries are under the dinette bench, and even when its sub freezing outside, its usually still 60 or so inside.

that said, if I actually COLD camped, I'd get the *new* SOK 206AH version that has the warmer, and also has integrated bluetooth charge state monitoring. I have 2 of the the older version 206AH without these features.

I'm very happy with my SOKs. Very good build quality. Get them from https://www.currentconnected.com/ they are the US stocking distributor

[rubicon327]

Originally Posted by alanmalk

Obviously 100 amps is not enough to run the typical big inverter so most people use 2 batteries in parallel for a max current of 200 amps. Some larger lithium batteries are designed for 200 amps or more.

Just as a point of reference our 400AH Bestgo is rated for 150A continuous and even higher for shorter durations. 200A rated BMS

[tacchino]

Victron charge controllers when combined with their temp sensor can be configured to cut off charging at whatever temperature you choose. As long as you are only charging through the controller and not through the converter/charger that would take care of the input side. On the output side the temp ranges are generally lower and easier to manage, especially if you just have it in storage.

[Sean Murry]

Battle Born Batteries recommended the batteries be at roughly 60 - 80% charge when in storage. They do not recommend they be at 100% state of charge.. They also suggested you cut off the batteries from solar while in storage to give the batteries a rest. I installed a battery disconnect switch directly at the batteries to completely disconnect it from solar while in storage

[John in Santa Cruz]

that is for long term storage, like months. mine get used quite regularlly, keeping the compressor fridge cold, the ventilation fan running.

[splitting_lanes]

After I get back from my next trip, I’ll look at disconnecting the solar charger so I’m not topping the battery off every morning.

I read the best way to disable the solar charger is to switch off the positive lead from the panel to the controller, and leave the controller connected to the battery. Makes sense from the standpoint of using the controller to turn on and off our inverter. The other day the wife went out to the trailer to grind coffee without waking the guests, used the inverter to run the grinder.

[hugh]

You can forgo the low temp protection in your BMS if all your chargers have low temp protection, and you are confident the charger temperature sensors track your battery temperatures. In other words, having a charger temperature sensor in a climate controlled area won't help you if the batteries sit in an unconditioned storage box.

As far as max load, max power, etc. the most important rating is the maximum continuous discharge current That's the maximum current that you can withdraw from the battery for an unlimited period of time, without triggering the batteries overcurrent protection.

If you're running a large load like a 1500w inverter, you're probably going to need at least a 200a continuous discharge rating.

[John in Santa Cruz]

Originally Posted by hugh

As far as max load, max power, etc. the most important rating is the maximum continuous discharge current That's the maximum current that you can withdraw from the battery for an unlimited period of time, without triggering the batteries overcurrent protection.

If you're running a large load like a 1500w inverter, you're probably going to need at least a 200a continuous discharge rating.

hence why I'm glad I got two SOK 206AH... they have a 100A continuous output rating (200A for 3 seconds), so two in parallel can safely deliver 200A to my inverter... I didn't originally plan on getting a big inverter, but once I had the big batts and proved the solar upgrade was sufficient, it just seemed like a handy thing to have. Also, they have a 40A recommended charge current (50A max), and the PD4655L *will* dump 55A into them continuously, so splitting that across two batts works nicely.

[DT6]

Originally Posted by hugh

You can forgo the low temp protection in your BMS if all your chargers have low temp protection, and you are confident the charger temperature sensors track your battery temperatures. In other words, having a charger temperature sensor in a climate controlled area won't help you if the batteries sit in an unconditioned storage box.

As far as max load, max power, etc. the most important rating is the maximum continuous discharge current That's the maximum current that you can withdraw from the battery for an unlimited period of time, without triggering the batteries overcurrent protection.

If you're running a large load like a 1500w inverter, you're probably going to need at least a 200a continuous discharge rating.

This, along with some of the other comments have been most helpful and educational. At first I thought a single 200Ah battery would do the trick, but they don’t have enough of a discharge rating at 100a. So the solution seems to be getting two 100Ah and running them parallel. Now I just have to select a brand.

I’d love to have another 40 to 100Ah in case I’m running my astrophotography gear all night plugged into the trailers outside DC socket, but I can buy a separate 50Ah battery for that and it will be more versatile in that I won’t be tethered to the trailer.

Thank you to everyone for your comments!

[John in Santa Cruz]

A problem with a separate battery is you'll need a separate charger, whether plugin or solar.... If you were to run your small battery down to 50%, and hook it up to your trailer's DC system to use the trailer's solar to charge it, and the trailer was already 100% charged, the trailer batteries would try and dump a HUGE amount of amps into the smaller battery.

[Sean Murry]

To be on the safe side, given I also have a Compressor fridge, I went with 4x100A lithium batteries, 190W roof top solar and 2x100A portable solar panels to chase the sun when the trailer is parked in the shade. The lowest I have ever been over a week boondocking is about 60%.