crowTrobot
New Member
Probably not the normal route. But I would like to at least look at it.
Suppose I want a 12v 100 AH battery w/o bms. Have any recommendations
- Thread starter crowTrobot
- Start date
sunshine_eggo
Happy Breffast!
fuzzmunky415
New Member
I've got a couple of Valence U27-12XP's I'll sell ya.. 144AH
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yodamota
Solar Enthusiast
ive been using a 95ah FLA battery in my car from costco. 150 bucks Canadian.
Rednecktek
Solar Wizard
No BMS? Anything with lead plates in it will do.
Did a BMS touch you in an inappropriate manner?
Did a BMS touch you in an inappropriate manner?
AlpineJoe
Solar Enthusiast
- Joined
- Jun 13, 2022
- Messages
- 233
Buy raw cells and DIY your own pack. Top balance them, don't drain them too low, and don't charge about 13.8V and you might be fine for a long time. I have a 50AH 12V pouch cell pack from JAG35 that I've been running BMS-less for almost 2 years now. I do have a balancing charger that ensures all the cells are charged to the same level. The most I've run the battery down is ~ 65%.
wpns
Solar Joules are catch and release
How does this differ from a BMS?
wpns
Solar Joules are catch and release
How does this differ from a BMS
scubadoo
Solar Enthusiast
I can be done despite many doomsayers.
Our 4 cell 300Ah Sinopoly LiFePO4 motorhome/engine starting battery has survived 10 years of fulltime travel without any inbuilt BMS circuitry.
My "BMS":
No charging source exceeds 14.1V at the battery terminals at which point the battery pack is always 100% SOC without any absorption time regardless of my usual charging currents according to both the series installed Victron and Junctek shunt based battery monitors.
75A alternator, 50A solar and rarely used 30A mains powered battery charger.
20% SOC loud alarm and Victron BatteryProtect 12.5V disconnect. Never triggered in day to day use.
Unlike apparently hundreds of fellow forum users cell balancing has never proved necessary for the last 10 years. Sure I occasionally check but again despite being informed multiple times that cell capacities will drift excessively they have not, well at least for my battery or the 280Ah EVE battery that I paralleled about 18 months ago.
I have observed up to a c40mV deviation on the odd occasion but as a test a few years ago forcing all cells to within 1mv required a few seconds at 30A. Certainly no useful energy added to any cell.
I'm almost convinced that sometimes perfect cell balance is perhaps just a psychological satisfaction thing?
Forcing the battery to 14.5V about a year ago. Near enough for me.
I must check again soon.
Click to enlarge.
Our 4 cell 300Ah Sinopoly LiFePO4 motorhome/engine starting battery has survived 10 years of fulltime travel without any inbuilt BMS circuitry.
My "BMS":
No charging source exceeds 14.1V at the battery terminals at which point the battery pack is always 100% SOC without any absorption time regardless of my usual charging currents according to both the series installed Victron and Junctek shunt based battery monitors.
75A alternator, 50A solar and rarely used 30A mains powered battery charger.
20% SOC loud alarm and Victron BatteryProtect 12.5V disconnect. Never triggered in day to day use.
Unlike apparently hundreds of fellow forum users cell balancing has never proved necessary for the last 10 years. Sure I occasionally check but again despite being informed multiple times that cell capacities will drift excessively they have not, well at least for my battery or the 280Ah EVE battery that I paralleled about 18 months ago.
I have observed up to a c40mV deviation on the odd occasion but as a test a few years ago forcing all cells to within 1mv required a few seconds at 30A. Certainly no useful energy added to any cell.
I'm almost convinced that sometimes perfect cell balance is perhaps just a psychological satisfaction thing?
Forcing the battery to 14.5V about a year ago. Near enough for me.
I must check again soon.
Click to enlarge.
Attachments
sunshine_eggo
Happy Breffast!
It's been well established that YOU are far more obsessive than the average human BMS.
robbob2112
Doing more research, mosty harmless
The math shows with no pattern of usage - i.e. totally random times and amounts of charge and discharge the batteries will stay balanced.
When you add in time of day, so solar charging, the pattern is less random and they will drift some.
Anyone using a normal pattern of night and day with similar usage of coffee in the AM, lights all day or not, tv at night, etc, but repetative off and on with repetative similar charge times/rates at the same times of day the cells will drift quite a bit and pretty quickly.
Summary is you can manage without a BMS, but why not use one or an active cell balancer and get away from having to check them periodically or top balance once and a while?
Let the automtion do the work.
chrisski
Solar Boondocker
- Joined
- Aug 14, 2020
- Messages
- 5,468
If I built a battery with no BMS, I'd build it with cells that have a high discharge / charge rate. For my Lithium Iron Phosphate batteries, I have topbrand that can charge discharge at 2C or 3C. The higher C discharge the better.
There could be a good reason to not have a BMS, like on a wheel chair crossing the street and the power dying as acceleration is needed to get out of the way of a car and not trip the BMS that stops the chair dead in its tracks. The risk your taking is the battery pack catches on fire as soon as the wheel chair is out of the way.
Personally, think building a lithium battery without a BMS is a terrible, terrible idea that gets worst as the battery gets older. If you know what you're doing its probably a terrible idea. Might not be so terrible if you can accept the loss of the equipment and all the other damages, that point only a bad idea.
There could be a good reason to not have a BMS, like on a wheel chair crossing the street and the power dying as acceleration is needed to get out of the way of a car and not trip the BMS that stops the chair dead in its tracks. The risk your taking is the battery pack catches on fire as soon as the wheel chair is out of the way.
Personally, think building a lithium battery without a BMS is a terrible, terrible idea that gets worst as the battery gets older. If you know what you're doing its probably a terrible idea. Might not be so terrible if you can accept the loss of the equipment and all the other damages, that point only a bad idea.
dktool
New Member
I'm still trying to figure out to build a car with no wheels, the Jetsons did it in the 60's and here I sit staring at my rubber tires.
And they, like a battery with no bms tend to explode occasionally.
And they, like a battery with no bms tend to explode occasionally.
Balancing chargers I have seen charge each cell individually to the correct voltage (3.50?)
They would provide no other protection.
The balancing chargers I have seen are for small battery hobbyist to fly a model plane or run a model car etc.
sunshine_eggo
Happy Breffast!
Yep. the balance chargers monitor all cells via an attached harness, much like a BMS harness. Most have some limited balancing capability on the order of 0.5A.
They charge until a single cell hits peak voltage.
Taper current to hold that cell at peak voltage and engage balancing.
I blabbered about it as an option for top balancing:
8S or less alternative to top balance with potential future awesomeness.
This charger, 20A 1-8S balance charger: https://www.amazon.com/ISDT-Touchscreen-Battery-Charger-Discharger/dp/B0823DGJXS?th=1 8S balance leads (no, you don't need 10, and you'd only use 5 of the 9 wires for 4S): https://www.amazon.com/JST-XH-Balance-Extention-RC-Battery/dp/B085W1T31S?th=1...
diysolarforum.com
sunshine_eggo
Happy Breffast!
Never seen that.
The sense leads only pass balancing current, so the voltage measurement isn't influenced by primary charge current. Stopping balance current to periodically check voltage would be sensible.
OzSolar
Whatever you did, that's what you planned.
Keep your eye on Battery Hookup. They often have things like this.
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scubadoo
Solar Enthusiast
No obsession here. Some others seem obsessed in their cell voltages being identical.It's been well established that YOU are far more obsessive than the average human BMS.
Our Victron system settings have remained unaltered for the last five or so years.
It all ticks over on its own without adjustment or intervention.
Sure I keep an eye on things and hopefully not too many others have blind faith in their often the cheapest BMS available operating perfectly for the next 15 years without checking occasionally.
I have no such faith for our perhaps unique and frequent 700A plus peak starter motor current draw requirements.
14.1V maximum, 10 minutes absorption and 13.45V while the sun still shines "float" is very easy and works for our now 10 year old fulltime RV use battery.
The "human BMS" is all but idle these days.
sunshine_eggo
Happy Breffast!
No obsession here. Some others seem obsessed in their cell voltages being identical.
Our Victron system settings have remained unaltered for the last five or so years.
It all ticks over on its own without adjustment or intervention.
Sure I keep an eye on things and hopefully not too many others have blind faith in their often the cheapest BMS available operating perfectly for the next 15 years without checking occasionally.
I have no such faith for our perhaps unique and frequent 700A plus peak starter motor current draw requirements.
14.1V maximum, 10 minutes absorption and 13.45V while the sun still shines "float" is very easy and works for our now 10 year old fulltime RV use battery.
The "human BMS" is all but idle these days.
Uh huh.
Are lithium ion batteries better than lead acid?
I found mine are pretty quiet. But maybe that's my old ears? ?? In my case can't hear over the ringing in my ears.
diysolarforum.com
scubadoo
Solar Enthusiast
Thank you for confirming my previous post unless you consider careful occasional battery monitoring is some form of obsession.Uh huh.
Are lithium ion batteries better than lead acid?
I found mine are pretty quiet. But maybe that's my old ears? ?? In my case can't hear over the ringing in my ears.
Perhaps I incorrectly assumed most others would do likewise?
If not I gladly plead guilty to all obsession charges.
400bird
Solar Wizard
That's what we're saying. Most people would start off saying they're going to do exactly what you do (play BMS on
sunshine_eggo
Happy Breffast!
The ratio of no-BMS bloated batteries to healthy batteries on this site is n:1.
You're 1.
robbob2112
Doing more research, mosty harmless
I think in this case I would equip the wheelchair with a second small battery and NO contactors (the $15 ones) so if your scenario occured it would switch to the backup battery pack.
And both packs would have a BMS on them
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