Is BIG BATTERY full of Crap??

[Dzl]

I might suggest to those who are curious & wish to learn more about battery tech "as it is today" with more current information to go through the site below

How low temperature affects the battery | Grepow Blog

Factors affecting battery at low temperature; Features of low-temperature battery; Grepow provides you LiPo and LiFePO4 low-temperature battery.

www.grepow.com

Thanks Steve, looks like a good resource on a topic where I have struggled to find detailed info. I'll check it out.

 

[Sojourner1]

For new folks reading this and wondering how to figure what "C" rate you're charging or discharging, here's how.

Example using my bank size;
Charge or discharge rate ÷ battery size

500a ÷ 500ah = 1c
100a ÷ 500ah = 0.2c
10a ÷ 500ah = 0.02c
1a ÷ 500ah = 0.002c

Going back a couple posts I believe ghostwriter66 was exaggerating some with the time to charge batteries, 28a into the 280ah battery would be 10 hours and if doing that from your solar system you just might fall short of dayight in winter conditions. If you sized your battery bank large enough or just have minimal loads you might be able to live in a psoc for long periods of time.

 

[ghostwriter66]

For new folks reading this and wondering how to figure what "C" rate you're charging or discharging, here's how.

Example using my bank size;
Charge or discharge rate ÷ battery size

500a ÷ 500ah = 1c
100a ÷ 500ah = 0.2c
10a ÷ 500ah = 0.02c
1a ÷ 500ah = 0.002c

Going back a couple posts I believe ghostwriter66 was exaggerating some with the time to charge batteries, 28a into the 280ah battery would be 10 hours and if doing that from your solar system you just might fall short of dayight in winter conditions. If you sized your battery bank large enough or just have minimal loads you might be able to live in a psoc for long periods of time.

So YES using the figures that the battery company is saying YES my numbers are exaggerated -- BUT using real world numbers out here in the field all I can say is that AT BEST - you MAY be able to ALMOST do a trickle charge to the battery once it hits 0/32. I would LOVE for someone to prove to me otherwise because that would save me a ton of grief with the 100000000 LiFePO4 batteries we have out here now that we have all set to literally barely trickle charge (if that) once the temp drops 0/32.

Hell last year this all started when BattleBorn said that they could charge well below freezing but when push came to shove never was able to say how they did it or what voltages or C rates they were using -- So forget the 0.1Ca vs 0.1C vs this or that - what i am saying is that with the info that our battery manufacturers has given us - taking a 100% charged battery that is below 0/32, and using it all night long in a van or camper or RV to where it is at 5% - then expecting it to be recharged the next day to 80 or 50% or 25% is NOT going to happen from where I sit.

Once again - DEJA VU from last year where we just all decided to agree to disagree. The #1 killer of LiFePO4 is HEAT, a close second is ppl charging them incorrectly under 0/32. ALL I am trying to do is let the NEWBIES and simple ppl like me know that YOU better know exactly what you are doing when you charge below 0/32 because there is NO coming back from that mistake. I think that i will now add this topic to the "file and forget" until next year at this time.

 

[fat_old_sun]

I think that i will now add this topic to the "file and forget" until next year at this time.

!Remindme in 1 year

(I do know that this forum does not have a remindme bot, but wanted to have the last word)

 

[ghostwriter66]

!Remindme in 1 year

(I do know that this forum does not have a remindme bot, but wanted to have the last word)

Now THAT made me laugh so THAT means my shift is over ... we can put the fire out tomorrow ....

 

[upnorthandpersonal]

Fushta!

(too obscure?)

 

[Hedges]

Could be no charger has been designed to accommodate the lithium C-rate/temperature curve.
For lead-acid, they understand charge voltages change with temperature, and those parameters can be user set.

If a consumer's PV system is > 10% of battery capacity, as the sun comes up they might only put a couple percent into the battery before charge rate exceeds 0.1C, and then BMS disconnects battery and they get no more charging.

We've seen some BMS that divert power to a heater. Whatever is done, needs to be a system solution (communication or settings), unless BMS can keep system up and running somehow.

 

[Steve_S]

Could be no charger has been designed to accommodate the lithium C-rate/temperature curve.
For lead-acid, they understand charge voltages change with temperature, and those parameters can be user set.

If a consumer's PV system is > 10% of battery capacity, as the sun comes up they might only put a couple percent into the battery before charge rate exceeds 0.1C, and then BMS disconnects battery and they get no more charging.

We've seen some BMS that divert power to a heater. Whatever is done, needs to be a system solution (communication or settings), unless BMS can keep system up and running somehow.

There are a few BMS's systems that do just that like this: http://bestechpower.com/communicationbms/HS-017.html or the slightly lighter HS-015 but when you start looking at these and pricing them, you'd better be ready to have a seat. This is another Level of BMS. I don't think anyone here is using BesTech BMS Systems. Many of their products are what I would call "Feature Rich" and priced accordingly.

 

[JoeHam]

Fushta!

(too obscure?)

Silver bullet or stake through the heart?

 

[Dzl]

Could be no charger has been designed to accommodate the lithium C-rate/temperature curve.
For lead-acid, they understand charge voltages change with temperature, and those parameters can be user set.

If a consumer's PV system is > 10% of battery capacity, as the sun comes up they might only put a couple percent into the battery before charge rate exceeds 0.1C, and then BMS disconnects battery and they get no more charging.

We've seen some BMS that divert power to a heater. Whatever is done, needs to be a system solution (communication or settings), unless BMS can keep system up and running somehow.

It seems to me while an integrated approach would be ideal, at least a basic implementation could be accomplished by the charge controller alone so long as it had an external temperature sensor. And it could be an optional feature, hidden behind warnings and disclaimers in the advanced configuration parameters. And it could be left up to the user to determine the values same as low temp cutoff on many devices.

At the end of the day though, I tend to agree with Dacian's assessment, too much attention is given to low temperature protection and not enough attention is given to avoiding low cell temperatures in the first place which is by far the better option where possible. Ideally both approaches can be employed, but I do agree that a disproportionate amount of attention is given to a hard cutoff and relatively little attention is given to how best to avoid needing to rely on a hard cutoff.

 

[myrkr]

As a noob coming in and reading this thread while searching for info on these specific Big Battery packs after seeing Will's review, what is the takeaway here in if these battery packs are worth buying? I (mostly) get all the points being made around the charging issues at various temps and that it could be considered in some cases a bit deceptive on Big Battery's part to present these packs as charging in any meaningful way at cold temps.

In terms of cost per watt, for what appears to be decent cells, case, wiring, etc. are these packs a good deal for those of us who need a pre-built lifepo4 battery? Or does this issue with low temperature charging make them not worth pursuing? They are cheaper than the SOK batteries that Will compared at the same time, and it seems from other various threads some people are not fans of the SOK batteries for various reasons. Just wondering if in the end how many of you (with far more knowledge and experience than me) would say the Big Battery pack is still a good deal worth buying if you need a decent lifepo4 pre-built pack.

 

[Bob B]

As a noob coming in and reading this thread while searching for info on these specific Big Battery packs after seeing Will's review, what is the takeaway here in if these battery packs are worth buying? I (mostly) get all the points being made around the charging issues at various temps and that it could be considered in some cases a bit deceptive on Big Battery's part to present these packs as charging in any meaningful way at cold temps.

In terms of cost per watt, for what appears to be decent cells, case, wiring, etc. are these packs a good deal for those of us who need a pre-built lifepo4 battery? Or does this issue with low temperature charging make them not worth pursuing? They are cheaper than the SOK batteries that Will compared at the same time, and it seems from other various threads some people are not fans of the SOK batteries for various reasons. Just wondering if in the end how many of you (with far more knowledge and experience than me) would say the Big Battery pack is still a good deal worth buying if you need a decent lifepo4 pre-built pack.

In your application .... will there be any risk of low temp? The cutoff is set to -20C

If I were looking for a ready made battery, I would want one with Bluetooth and the ability to configure settings.
It also seems that this battery ... or the SOK ...have no cell compression. It has been widely discussed on a couple of forums and compression is recommended for the most popular DIY EVE and Lishen cells.

 

[myrkr]

In your application .... will there be any risk of low temp? The cutoff is set to -20C

If I were looking for a ready made battery, I would want one with Bluetooth and the ability to configure settings.

Yes, these will be installed inside of a camper van, so there will times when the van is not warm inside and charging could take place (solar or first drive warm-ups via alternator). My plan is for a mostly Victron install (Multiplus, Smart Solar Charger, Orion Smart DC-DC, BM712 Monitor, etc.) so I was hoping that the Victron system could all be configured in such a way to prevent any charging of the battery below 32F let's say. It sounds like from reading documentation on all of these Victron pieces that they could be programmed like this. So my hope is that the Victron stuff will act as the brains and not charge below whatever temp I set, and the battery more or less doesn't need to be smart enough to protect itself from low temperature charging (though it would of course be nice if it did). But my logic with this approach could be flawed.

 

[Bob B]

Yes, these will be installed inside of a camper van, so there will times when the van is not warm inside and charging could take place (solar or first drive warm-ups via alternator). My plan is for a mostly Victron install (Multiplus, Smart Solar Charger, Orion Smart DC-DC, BM712 Monitor, etc.) so I was hoping that the Victron system could all be configured in such a way to prevent any charging of the battery below 32F let's say. It sounds like from reading documentation on all of these Victron pieces that they could be programmed like this. So my hope is that the Victron stuff will act as the brains and not charge below whatever temp I set, and the battery more or less doesn't need to be smart enough to protect itself from low temperature charging (though it would of course be nice if it did). But my logic with this approach could be flawed.

Most of us want the BMS to be a backup to whatever the charge controller does or does not do .... So, the non configurable low temp cutoff would be a deal breaker for me.

 

[Hedges]

Batteries with Bluetooth ... what is this world coming to? <smh>
If I wanted to mess with batteries I'd use a hygrometer. But I don't, so I bought AGM.

Maybe you could set up a thermostat to control a relay, transferring SCC & DC-DC from battery to a heater. Don't like to disconnect a charging circuit, but that's exactly what a BMS reserves the right to do, correct?

 

[Dzl]

Yes, these will be installed inside of a camper van, so there will times when the van is not warm inside and charging could take place (solar or first drive warm-ups via alternator). My plan is for a mostly Victron install (Multiplus, Smart Solar Charger, Orion Smart DC-DC, BM712 Monitor, etc.) so I was hoping that the Victron system could all be configured in such a way to prevent any charging of the battery below 32F let's say. It sounds like from reading documentation on all of these Victron pieces that they could be programmed like this. So my hope is that the Victron stuff will act as the brains and not charge below whatever temp I set, and the battery more or less doesn't need to be smart enough to protect itself from low temperature charging (though it would of course be nice if it did). But my logic with this approach could be flawed.

I believe (not positive) that with Victron components you could prevent low temp charging. I know it is possible with the Solar Charge Controller, I'm not positive if it is possible 'system wide', or if it is, if you need a 'GX' device.

I feel a llittle differently than Bob RE: it being a dealbreaker, unlike voltage where its definitely important to have the BMS act as a second line of defense, with low temp protection, I think multiple lines of defense is more of a 'nice-to-have' redundancy than a necessity. In practice--unlike over or under voltage protection--almost nobody has two lines of low temp defense. Its generally one or the other. Most people's only low temp protection is at the BMS.

 

[Bob B]

I believe (not positive) that with Victron components you could prevent low temp charging. I know it is possible with the Solar Charge Controller, I'm not positive if it is possible 'system wide', or if it is, if you need a 'GX' device.

I feel a llittle differently than Bob RE: it being a dealbreaker, unlike voltage where its definitely important to have the BMS act as a second line of defense, with low temp protection, I think multiple lines of defense is more of a 'nice-to-have' redundancy than a necessity. In practice--unlike over or under voltage protection--almost nobody has two lines of low temp defense. Its generally one or the other. Most people's only low temp protection is at the BMS.

I like to err on the side of safety .... If it can ruin your battery, I think the BMS should be protecting against it happening. In a Van, there could be 3 charge sources including solar, shore power, and DC-DC .... It seems like it is going to get complex to synchronize all 3 to prevent cold temp charge. The BMS is the last line of defense there ... but there will always be various opinions.

 

[myrkr]

Batteries with Bluetooth ... what is this world coming to? <smh>
If I wanted to mess with batteries I'd use a hygrometer. But I don't, so I bought AGM.

Maybe you could set up a thermostat to control a relay, transferring SCC & DC-DC from battery to a heater. Don't like to disconnect a charging circuit, but that's exactly what a BMS reserves the right to do, correct?

Yeah, I was wondering if I could then just create my own external temperature sensing disconnect, but thought similarly that it probably wouldn't be ideal to disconnect a high charge rate cold turkey? Maybe if there was a device that could manage the low temp disconnect (if the Victron system can't) but do so in a graceful disconnect kind of way that pulled throttled down (almost immediately)?

I believe (not positive) that with Victron components you could prevent low temp charging. I know it is possible with the Solar Charge Controller, I'm not positive if it is possible 'system wide', or if it is, if you need a 'GX' device.

I feel a llittle differently than Bob RE: it being a dealbreaker, unlike voltage where its definitely important to have the BMS act as a second line of defense, with low temp protection, I think multiple lines of defense is more of a 'nice-to-have' redundancy than a necessity. In practice--unlike over or under voltage protection--almost nobody has two lines of low temp defense. Its generally one or the other. Most people's only low temp protection is at the BMS.

I'll have to check with my Victron rep to see what the system can/can't do in regards to system wide temperature sensing voltage disconnect.

I think in a more ideal world the Big Battery would have a more standard low temp BMS protection configuration, as opposed to this current offering, however given the overall decent pack build (minus this BMS issue), coupled with the really low cost per watt, it seems like it still might be worth it. In terms of cost per watt along with the product itself, it seems like it's either the Big Battery or the SOK.

I like to err on the side of safety .... If it can ruin your battery, I think the BMS should be protecting against it happening. In a Van, there could be 3 charge sources including solar, shore power, and DC-DC .... It seems like it is going to get complex to synchronize all 3 to prevent cold temp charge. The BMS is the last line of defense there ... but there will always be various opinions.

I agree on erring on the side of safety. My van will have solar, shore, and DC-DC, so I really would prefer the BMS to have proper low temp cutoff, and then be able to program the Victron stuff as a second line of safety.

 

[backwash]

Good day; I almost hate to wade in here as this has been an interesting conversation.

But for me: My 280ah batteries for my RV have a 14w heater on each side for a total of 28 watt consumption. The testing I did last spring showed that the heaters could increase the temperature of the battery by about 10 degrees in an hour. To go from O deg F to 40 deg F (which is where my Victron mppt controllers are set at to allow charging) it would only take 28 watts (each battery). And only 56 watts over 2 hours in the morning to get to an even safer 50 deg F.

With this in mind why would a person risk charging at anything below 40 or 50 deg even at a low .1C rate when the energy cost is so low to heat them up to a much safer range ? A rough calculation in this instance would be about 3% of the battery capacity to heat them up and get them to that 50deg mark where they can take a much higher current.

 

[Dzl]

I like to err on the side of safety .... If it can ruin your battery, I think the BMS should be protecting against it happening. In a Van, there could be 3 charge sources including solar, shore power, and DC-DC .... It seems like it is going to get complex to synchronize all 3 to prevent cold temp charge. The BMS is the last line of defense there ... but there will always be various opinions.

I feel I usually err on the side of caution also (some would say overly so).

In this case, I suppose the point I was trying to make, is if someone controls low temp cutoff at the charge controller instead of the BMS, they have no more or no fewer lines of defense than someone that controls it only at the BMS. Since most people only control it at the BMS and do not have the capability to do so at the charge controller, @myrkr's approach has no fewer layers of protections than the default approach.

That said, I think you make a very good and valid point that there is value in the simplicity of a single device being able to cut all charging if temperature drops to freezing. More complexity equals more chances to misconfigure something or more chances for something to fail. A BMS based solution would be simpler in a multi-charger situation. This is especially valuable for someone that does not feel confident in there ability to design/configure there system and wants something that 'just works'.

That said, Victron makes very high quality equipment and its designed to integrate pretty well. IF low temperature cutoff can be managed centrally by the BMV or by a GX device, or be managed individually by each charge source I would tend to trust it. Sure its a bit of added complexity but on the other hand you are trusting a much more reputable company than whoever is making most of the BMSes we use.