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Electrical system load measurements?

FYI, got a response back from Antigravity batteries:

"Thank you for reaching out to us.

As long as your charging voltage is in the 13.2 to 14.6 V range, you shouldn't see any issues. Our car batteries are designed to handle typical engine bay temperatures, and they come with protections from over-discharge, over-voltage, overheating/thermal runaway, and short circuit. Some newer cars with smart charging systems can be problematic for our batteries, but they generally work great in older cars. You just want to avoid installing it right next to a big source of heat, like the engine manifold, for example. If the car is modified and the engine bay temps are slightly higher than normal, some heat resistant wrapping should suffice, but if the engine bay temps are significantly higher than stock, I recommend relocating the battery to be on the safe side.

I have an older car as well (1991 Prelude Si) and I'm using our ATX20-HD motorcycle battery. It's been bulletproof for the past six years. If you're looking for a smaller battery as well, an ATX30-HD would be great for your car as long as you don't have any power thirsty accessories.

https://antigravitybatteries.com/products/starter-batteries/restart-oem/atx30-hd/

Here is a video with lots of info on our batteries and lithium in general.

https://youtu.be/R_rw_qstFdE?si=qZ1uiGgG4zWMxe3R

Have a great day, and please let me know if you have any additional questions."



FWIW I see "Lithium Ion" on their batteries (and mention in the video) however they clarify that all are LifePo4.

Relatively pricey, but based on the cost of other lithiums advertised as automotive starters, it's not outrageous. More than I'm willing to pay for the cost/benefit in my case, but for a daily driver, they could be a good option. Another thing I remembered but hadn't thought to put down, corrosion should be nil with these batteries.

If a manufacturer is going to allow reps to state that the batteries will work as a drop in, I'm inclined to test the tiny one in the truck just for the heck of it, with the alternator.

Still concerned about the underhood heat and starter draw, so will have to test to get those numbers when I get the chance.
 
So you grabbed my attention with this. I've been researching.

Weird thing is I went to school for power engineering, and through a lot of career moves and time I work a lot on control systems for utility scale batteries. These things seem like a black box comparatively.

I would like to switch to no longer use SLA in my motorhome house batteries and maybe my Jeep. What research have you guys found? I didn't mind SLA but now they're failing after just a couple years in most of my stuff.
 
I feel at this stage if all lifepo4's could serve as starting batteries, there would be no use case for SLA of any type. (I assume agm is in some way shape or form included in SLA, if not, AGM is still garbage comparatively as well).

It does really depend on use however. Starting battery, eh, tough. The dedicated automotive-sized starting batteries are pricey. Too pricey IMO. If you were able to use one battery for starting and storage (say 140Ah) it would save people so much money, immediately and over time, even if the costs were say, a hundred more than a comparable storage only battery.

For storage, SLA cannot compare. Period. The Lifepo4's will not let you damage them (over charge or over discharge) unlike SLA's. The rated capacity of a lifepo4, assuming it's one you've seen tested on YouTube, is always near the Ah rating, usually slightly over. Their discharge voltage curve is flat, unlike SLA.

FWIW, economy of scale doesn't seem to work with the Lifepo4's though. One would think a 200Ah would be a bit less than two 100's, but the opposite is true. It may just be demand is lower. Which is weird, as for storage, fewer batteries is less complicated. The BMS limits the discharge current so you need to account for that for your use, but generally they are around 100A discharge, usually a higher peak for a few seconds, which I think is pretty good for most uses outside of whole house backup.

Depending on age, recreational vehicles of semi-recent manufacture apparently often have a power converter/battery charger that is made for lithium and SLA, I believe those tend to need a jumper changed, that's it. Older you'll need to replace the charger with one made for lithium. Apparently the RV lifepo4 charger replacements are common, but be careful, as with everything else, the Chinese are selling copies that don't work properly.

I don't even have an RV, but given I have a golf cart that may go 48v, I've wondered about using the 48v battery from it, with an inverter/charger in an RV. Plug the inverter into the shore power of the RV, and forget about 12v for anything other than what runs off the vehicle/trailer when in motion. 3000w (with up to 6000w surge) pure sine wave inverters are not that pricey really. You can even get inverter/AC charge/solar charge inverters. Go look at Victrons page if this sort of stuff excites you lol https://www.victronenergy.com/

Seriously though. This battery chemistry has opened the floodgates to electronics that can be used to take advantage of the better cycle life, and capacity. You could literally eliminate propane use in many RV's for well south of $1000, short of a heater if you need one. Given you'll get the same battery capacity in half as much space vs SLA, you'll also have more room for other gear.

With the weight of these batteries, it is not impractical to also consider using them as household backups in short-term emergencies, so they don't have to be JUST an RV deal. And if you have solar, these things will charge fast if your system can generate enough current, making them very good for the aforementioned household backup.

Their only real downsides IMO are the relatively low discharge current most have (limiting use as a starter battery), higher required charge voltage (typically seen 14.2-14.4), and their limitations at hot/cold. But I think the cold weather limitation is a bit overblown.

Check the "specs" here of a battery I semi-randomly selected: https://www.litime.com/products/litime-12v-100ah-lithium-lifepo4-battery the chemistry is what determines the charge/discharge limitations based on temp, but unless you spend your time in areas where it stays below freezing for days at a time, I don't think that the charge limitation of 32* is that much of a factor. If it IS, heated Lifepo4's are available. But since they don't off-gas, in an RV I'd be inclined to keep them as near the interior as I could, to keep them as warm as possible without needing to spend more money on the same battery, just heated.

12v heating pads are so cheap if I wanted them "just in case", I think they would be a more cost effective option than the heated batteries anyway. I feel the heated batteries are way more expensive than they should be, considering the temp probes are already there, and the heating method to me is questionable...unless the temperature probes are buried deep in the middle of the battery, they aren't going to reflect the actual core temperature. The heaters are never between the cells, always outside (but inside the case), so I'm a bit leery of trusting that. I expect the majority of users are not dealing with frozen batteries, and with a 4000+ cycle life, if it cuts battery life 25% when would we actually find out? Widespread adoption is really only the last year or two, so we have some time yet to see any long term failure trends. Most of us could probably discharge a lifepo4 battery 100% every time we used them, and still not kill them in ten years because we don't do so every day.
 
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So maybe in September I bought an EcoFlow 12V 100Ah LiFePO4 that is approximately the size of a group 27. It doesn't have bluetooth. I think that's pretty much mandatory now that I've dabbled. I bought it for a trial to run one of my wifi camera stations out in the woods. All I've found out is that my 15 year panels hardly put out any power.

I think for my motorhome (two group 27s fit under the steps and I'd just put a Facon heat pad in there if necessary) I'm going to buy a pair of these unless someone has a better idea:
 
IMO, I wouldn't buy anything I haven't seen someone (like Will Prowse, but there are multiple others that do comprehensive testing and tear downs) tear apart and actually test. I've heard of Powerqueen, just can't recall how they tested.

There is some dangerous stuff out there (like no overcurrent protection, or heat based only overcurrent protection, too small wiring inside, etc.) so unless it tests well, or I know I don't care about the flaws, then I won't consider it. I've seen 100Ah batteries down into the $130's now, but I also just got done watching a video where a "budget" brand had apparently changed the QR codes on the cells to make them appear newer than the three years old they actually were.

While it will be more costly per watt hour, I'd look at one larger battery than two, of course you may need to measure for fitment. There is some wonky stuff that goes on with many of these batteries when in parallel (it's a BMS thing) where one draws down significantly before the other one starts to draw down, instead of drawing down evenly. Can't recall all the specifics, but it turned out not to be isolated to the one brand.

If capacity is never a concern where you aren't trying to intensively manage and plan how much time you can run whatever, who cares, but if you are trying or needing to keep good track of what power is left, the calculations aren't quite as easy. Not hard, but more thinking required. I'm unsure how that works for balancing if the two batteries are now drawn down to different levels and charging isn't always completed to 100%. I don't quite get the balancing thing when it comes to batteries in parallel, not something I've had to really consider, but I know the issue on drawdown as it became a pretty big topic.

Maybe it's what I'm just used to, various status' on the wall as you step into the RV/trailer, but I think I'd rather have a hardwired battery monitor on the wall somewhere. Bluetooth can be handy, but if I was only using a battery in a fixed position, as long as the wired monitor showed all the same data, I don't know as I'd pay a premium for bluetooth. Probably not real common for the 12V 100Ah batteries to come with a monitor, not sure if that holds true with the 12V 200Ah+ ones as well. I would *think* it has something to do with cost, so the bigger the battery the more likely they would be to include it? Most of the 48V batteries seem to come with monitors for some reason, even when bluetooth is present. If I only had bluetooth though, I don't think I'd fret, who doesn't have their phone with them all the time anymore anyway?

I got my 48V DCHouse on eBay through their "account" there, as a refurb or slightly used unit. It was (relatively, ~20% less) dirt cheap for a battery that tests as well as it does, with all the same accessories as when bought new. If you have time, eBay may be an option if saving money on a larger battery is of interest to you.
 
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dyeager535 said:
IMO, I wouldn't buy anything I haven't seen someone (like Will Prowse, but there are multiple others that do comprehensive testing and tear downs) tear apart and actually test them. I've heard of Powerqueen, just can't recall how they tested.

There is some dangerous stuff out there (like no overcurrent protection, or heat based only overcurrent protection, too small wiring inside, etc.) so unless it tests well, or I know I don't care about the flaws, then I won't consider it. I've seen 100Ah batteries down into the $130's now, but I also just got done watching a video where a "budget" brand had apparently changed the QR codes on the cells to make them appear newer than the three years old they actually were.

While it will be more costly per watt hour, I'd look at one larger battery than two, of course you may need to measure for fitment. There is some wonky stuff that goes on with many of these batteries when in parallel (it's a BMS thing) where one draws down significantly before the other one starts to draw down, instead of drawing down evenly. Can't recall all the specifics, but it turned out not to be isolated to the one brand.

If capacity is never a concern where you aren't trying to intensively manage and plan how much time you can run whatever, who cares, but if you are trying or needing to keep good track of what power is left, the calculations aren't quite as easy. Not hard, but more thinking required. I'm unsure how that works for balancing if the two batteries are now drawn down to different levels and charging isn't always completed to 100%. I don't quite get the balancing thing when it comes to batteries in parallel, not something I've had to really consider, but I know the issue on drawdown as it became a pretty big topic.

I also think that for an RV I'd rather have a hardwired battery monitor on the wall somewhere. Bluetooth can be handy, but if I was only using a battery in a fixed position, as long as the wired monitor showed all the same data, I don't know as I'd pay a premium for bluetooth. Probably not real common for the 12V 100Ah batteries to come with a monitor, not sure if that holds true with the 12V 200Ah+ ones as well. I would *think* it has something to do with cost, so the bigger the battery the more likely they would be to include it? Most of the 48V batteries seem to come with monitors for some reason, even when bluetooth is present. If I only had bluetooth though, I don't think I'd fret, who doesn't have their phone with them all the time anymore anyway?

I got my 48V DCHouse on eBay through their "account" there, as a refurb or slightly used unit. It was (relatively, ~20% less) dirt cheap for a battery that tests as well as it does, with all the same accessories as when bought new. If you have time, eBay may be an option if saving money on a larger battery, if less cost is of interest to you.
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The battery i bought did say they do not recommend putting in parallel so I got a 280ah so I didn't need to.
 
Shenzhen LiTime Technology Co has been around a while
Ampere Time
LiTime
Power Queen

etc are all them. There are probably more.


I'm mostly worried about any battery catching on fire.
 
Can confirm they still burn, but not like a standard lithium ion. It's usually caused by a rogue BMS combined insufficient engineering on heat dissipation and connections (bus bars, poor connections to cells, etc).
 
CyberSniper said:
Can confirm they still burn, but not like a standard lithium ion. It's usually caused by a rogue BMS combined insufficient engineering on heat dissipation and connections (bus bars, poor connections to cells, etc).
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Yeah, that's really the reason to do the research. The bigger names consistently have solid construction, it's when you start trying to be cheap that the cost cutting can come into play. Nothing wrong with being cheap, there are a few bargains to be had, but typically the cost comes from cutting the mentioned corners.

For something where a failure isn't going to be dangerous or critical, no biggie, use a cheapy and hope it works out. When it potentially comes to peoples lives, I'll pay a couple $$ more for stuff proven to be made properly.
 
I'm pretty sure it's all made by a few manufacturers to specific price points. I haven't spent a lot of time at it, but I'm willing to bet most of them in the same price range come from the same place.

The Will Prowse guy is worth watching the videos with the sound off. It's hard to take seriously anyone that hangs their drillbits by on the wall with a magnet. His wild ass guesses on why things are done a certain way are terrifying because people parrot that shit like fact.

I'm more familiar with utility grade batteries (including lead acid with clear cases so you can monitor them). Like batteries measured in MW. You can comfortably fit 1.5MWh of battery in a conex container for example.
 
The 48v battery is powering 12v equipment? What is changing the voltage ?
 
CyberSniper said:
DC to DC buck converter. Not terribly efficient but they work fine.
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You can find them up the mid 90% range - under load. The problem is that when everything is off, they still draw power (i.e. 0% efficiency). You might be able to use multiple smaller ones and have power cut to the systems you're not using.

dyeager535 said:
@CyberSniper

With this you can just forego a generator. Lol. https://www.wattcycle.com/products/12v-628ah-lifepo4-lithium-battery-with-bluetooth
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An 8kWH battery is a whole different league than generator, which maybe can provide 8kW continuously. 300A might not be enough to run a well pump and definitely not enough for an electric range or microwave. If all you need is refrigerators, a furnace, and some lights it could probably get you through the night, though.
 
Blue85 said:
An 8kWH battery is a whole different league than generator, which maybe can provide 8kW continuously.
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Oh I know, but he was talking about 2x 12v 100Ah lifepo4's for his RV, and I saw these batteries just came out, it seemed humorous.

600+ Ah would probably provide most people used to deep cycles and a generator to recharge them in an RV/trailer so much run time that generator usage would be uncommon vs common. Obviously living in the thing (especially in summer with AC) is going to be far different than using it as a place to crash for the night and being out all day.

When we ran lead acids in a trailer for winter camping the generator was a requirement daily after the heater fan, fridge, etc ran all night. 600+ Ah is probably about 6 times what we had in usable Ah at that time. Something this massive would have been reassuring, and would have been nice to reduce reliance on the generator.

Willing to bet if I went and spec'd out 600Ah (usable) of Trojans or similar, this would be cheaper.
 
I haven't read all the responses, but you can get a pretty good idea of the electrical load using a voltmeter. Since all wires have resistance, if you measure the voltage drop from one end of the wire to the other you can divide that by the resistance of the wire and get the current. For example, if you have a 2AWG wire going from the battery to the starter that is 6 ft long the resistance of that wire will be 0.001518 ohms. The way you figure that out is to look up the resistance of the wire under test and it will tell you the ohms/foot (or ohms per 1000 feet). Then you multiply that number by the length of the wire to get your total resistance. Now measure the voltage drop from one end of the wire to the other. Say it's 0.1 volts. Knowing that voltage=current x resistance we can calculate the current. Let's rearrange that equation into the form we want so that current=voltage/resistance. So with a voltage drop of 0.1V divided by 0.001518 equals about 66 amps. Of course this will all depend on the accuracy of your meter when reading the voltage drop across the wire. Do this for all the wires coming off your battery and add the results together. If this is too confusing just post up all the voltage drops across the wires coming off your battery and the gauge and length of your wires and I'll do the calculations for you. :waytogo:
 
wouldn't connections and terminal to cable attachments add some measurable resistance that would need to be accounted for in that equation ?
 
Negligible compared to the meter accuracy and measurement of the cable length, etc. This is just to get a good idea. Nothing would beat a true ammeter measurement though.
 
A generic RV rooftop AC unit takes about 1350 watts to run the fan and compressor. The more expensive ones that have two fan motors take less energy because they only run the fan when it is needed.

Most people like me that have used lead-acid batteries are used to 70-100ah batteries that you can realistically get 25-40ah out of them before cell damage. So going from 40ah to 100ah usable is huge. My old camper I used 3 group 34/78 batteries to get two solid days of usage. I can do that with a single group-24 sized lithium battery now. Which is why I keep looking at them.

One of my beefs with the cheaper batteries (like wattcycle) is that they don't pay attention to packaging. They just make a battery that is convenient to package, not understanding that most people that aren't look for loose cells are trying to stuff them in a BCI-standard compartment.
 
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