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To BMS or NOT to BMS?
#1
I've gone from 7s to 10s for my 36v (max 42v) 12KW inverter, but the two 10s BMS I've purchased from different vendors were not protecting against overdischarge. So, I decided to go 11s and charge the pack to 42v (42/11=3.8v per cell/module.) It has been working pretty good so far with a delta of about 40-60mv difference. Is there a way to wire a 14s BMS on a 10s or 11s battery?

Thanks.
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#2
Here's a bms that can do 11s: BMS 6S 7S 8S 9S 10S 11S 12S 13S 4.2V 25A Adjustable BMS Lithium Li-ion 18650 PCM
And it has:
25A Adjustable BMS
Over charge recover voltage: MIN:4.14V TYP:4.19V MAX:4.24V
Over discharge detection voltage : MIN:2.72V TYP:2.8V MAX:2.88V
Over discharge recover voltage: MIN:2.9V TYP:3V MAX:3.1V
Over charge detection current: MIN:32A TYP:40A MAX:48A
Over charge detection delay time: MIN:700mS TYP:1000mS MAX:1300mS
Over charge current protection delay time: MIN:mS TYP:16mS MAX:20mS
Over disrcharge current detection current : MIN:54A TYP:60A MAX:66A
Over distcharge current protection delay time: MIN:18mS TYP:24mS MAX:30mS
Idle current : 25uA
temperature protection: Yes
Over current protection : Cut load
discharge current: 18A
Over charge detection voltage: MIN:4.23V TYP:4.25V MAX:4.27V
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#3
That question should not have to be asked from the start...


Get a proper BMS that does what you need. A BMS for 20USD seldom works for a larger system. They are made for ebikes and such and nothing else.
Some BMS´s out there can be wired down but not all of em.
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#4
There are some of us who can't afford BATRIUMS yet and need to come up with alternatives. I was looking at the Chargery BMS16T, where you can use from 2S to 16S, but I haven't found enough info to make the jump. ElectroDacus is another option, but they only go up to 24v. Another good option would be the DIY BMS as shown on Julian Ilett's video, but I have no time to be soldering parts. The 7S I have is one of those Chineese Cheap models and it works perfectly, but it's 28.8v.

Oh, BTW, I'm not powering just lights and little thingys for a little while and go back to the grid. I'm powering my entire house with this -I'm NOT connected to the grid whatsoever. I'm talking about Washer, Fridge, TV, Microwave Oven, Blender, PlayStation, Projector, Waterpump, you name it!
1500W of Residual Thermonuclear Energy Collectors (6X250W 2S)
40A eSmart3 MPPT Controller
Raspberry Pi 3 remote monitoring
BATTERIES, Need Lots of Batteries!
800 18650 (80P10S= 40.0v) 4.1Kw
12Kw Pure Sinewave 36V Inverter
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#5
(05-16-2019, 01:48 PM)DomingoRP Wrote: Oh, BTW, I'm not powering just lights and little thingys for a little while and go back to the grid. I'm powering my entire house with this -I'm NOT connected to the grid whatsoever. I'm talking about Washer, Fridge, TV, Microwave Oven, Blender, PlayStation, Projector, Waterpump, you name it!

Ahh, definitely don't use the one I linked to earlier Tongue

Have you looked at Colin Hickey's BMS? Adam Welch did a few videos over the course of a year to show it's reliability.
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#6
Yes, I have. Also, Great Scott has a video about that DIY BMS. I guess I’ll start saving for a Batrium. I’ve found a supplier of 18650s that has a boatload of 2100mA hardly used cells from Laptops and I don’t want to mess them up once I complete the planned 10Kw Powerwall. I just went back to use the Chinese 10s. It balances and protects from Over voltage, but does not protect against under voltage.
1500W of Residual Thermonuclear Energy Collectors (6X250W 2S)
40A eSmart3 MPPT Controller
Raspberry Pi 3 remote monitoring
BATTERIES, Need Lots of Batteries!
800 18650 (80P10S= 40.0v) 4.1Kw
12Kw Pure Sinewave 36V Inverter
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#7
I just got the chargery bms8t (its the same as the bms16 and bms24,  but only monitors 8 cells and has smaller control box). I been putting it through its paces for the past week. 

I got it hooked up to my 220ah lifepo4 which is connected to a 240watt solar panel and 20 amp ecoworthy mppt. I decided to get the chargery to replace the 4 dollar 30amp bms I was previously using. The cheap bms don't work well with solar, everytime the bms triggers to stop charging I would get voltage surges that destroyed many 12 volt fans.

The chargery comes with no instructions in the box, you need to download from website, it took me a while to find them. Its basically a display box, control box (that goes by your battery), and a shunt (i got the 100amp). The display box (lcd) is connected to the control box by a coiled wire(like on a telephone) and you can place the the display box in a convenient area. The control box gets its power from the balance connectors or external source. If you power from the balance connectors, I notice the readings for the cells were all over the place, I decided to use an external source (actually the same battery 13.3 volts) the external plug is not included but I found out that an opus btc3100 plug will fit perfectly on the unit. With external power, the cell voltage read perfectly.

You need to supply your own contactors I been using a 30 amp automotive relay (its all I need for my system), The control box can power larger contactors, much higher amps then most bms. The chargery is failsafe in design, the connectors that supply the contactors are always powered on, if the bms decides to shutoff the charging the contactor is deenergized. If the chargery loses power, the contactors will shutoff charging. The method of controlling the contactors is not changeable, they are always energized, so you need a  contactor that are always normally open(when deenergized). If using large contactors, they will be consuming power all the time, I see that as a negative unless you have a very large battery bank. I actually decided not to use a contactor for over discharge, since I rarely use more then 30 amps in a day. I'll rely on the audio alarm. 

The chargery can count the amps going in/out of the battery, but it displays in watt hours, myself I prefer to monitor the amp hours but that is not an option with the unit. In the settings you set the battery amp hours but I don't know how the unit uses it since it doesnt show up in the main screen. As a coulombmeter the unit is useless for that purpose, though it should be able to do it. Also on the main screen any usage of less then 1 amp charge/discharge isn't displayed.

Besides the ability to control the contactors to disconnect charge/discharge, it also has a beeper alarm and a flashing light that will go off when limits are exceeded. And it has 2 temperature probes that monitor battery temp, they will also disconnect charging/discharging if temps are exceeded. The cells over/under voltage are fully programmable. Also the chargery can balance at 1.2 amps per cell, which also allows to set the voltage you want it to start balancing. I am using active balancers on my lifepo4 pack so was unable to test the balance feature.

As far as longevity, the unit seems very well built. I like the ability to see the cells voltage in real time. I like it so far, cost me 86 dollars including shipping.
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#8
Domingo: You dont need to get Batrium system. You need a BMS. But a good BMS do cost. I know plenty of them that cost 5x what Batrium do Big Grin

Im not sure why people get stuck at that? Yes you get what you pay for and yes you need a BMS. Then you need to define what its worth for you and what it is for. In my case we talk about protecting a LARGE battery bank that is for my whole property. In such a case a 1000USD BMS is nothing but for someone with 100USD batteries and its outside a 10USD bms is more likely an ok choice. Still depends on what you aim for.
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The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#9
(05-17-2019, 05:23 AM)jonyjoe505 Wrote: I just got the chargery bms8t (its the same as the bms16 and bms24,  but only monitors 8 cells and has smaller control box). I been putting it through its paces for the past week. 

I got it hooked up to my 220ah lifepo4 which is connected to a 240watt solar panel and 20 amp ecoworthy mppt. I decided to get the chargery to replace the 4 dollar 30amp bms I was previously using. The cheap bms don't work well with solar, everytime the bms triggers to stop charging I would get voltage surges that destroyed many 12 volt fans.

The chargery comes with no instructions in the box, you need to download from website, it took me a while to find them. Its basically a display box, control box (that goes by your battery), and a shunt (i got the 100amp). The display box (lcd) is connected to the control box by a coiled wire(like on a telephone) and you can place the the display box in a convenient area. The control box gets its power from the balance connectors or external source. If you power from the balance connectors, I notice the readings for the cells were all over the place, I decided to use an external source (actually the same battery 13.3 volts) the external plug is not included but I found out that an opus btc3100 plug will fit perfectly on the unit. With external power, the cell voltage read perfectly.

You need to supply your own contactors I been using a 30 amp automotive relay (its all I need for my system), The control box can power larger contactors, much higher amps then most bms. The chargery is failsafe in design, the connectors that supply the contactors are always powered on, if the bms decides to shutoff the charging the contactor is deenergized. If the chargery loses power, the contactors will shutoff charging. The method of controlling the contactors is not changeable, they are always energized, so you need a  contactor that are always normally open(when deenergized). If using large contactors, they will be consuming power all the time, I see that as a negative unless you have a very large battery bank. I actually decided not to use a contactor for over discharge, since I rarely use more then 30 amps in a day. I'll rely on the audio alarm. 

The chargery can count the amps going in/out of the battery, but it displays in watt hours, myself I prefer to monitor the amp hours but that is not an option with the unit. In the settings you set the battery amp hours but I don't know how the unit uses it since it doesnt show up in the main screen. As a coulombmeter the unit is useless for that purpose, though it should be able to do it. Also on the main screen any usage of less then 1 amp charge/discharge isn't displayed.

Besides the ability to control the contactors to disconnect charge/discharge, it also has a beeper alarm and a flashing light that will go off when limits are exceeded. And it has 2 temperature probes that monitor battery temp, they will also disconnect charging/discharging if temps are exceeded. The cells over/under voltage are fully programmable. Also the chargery can balance at 1.2 amps per cell, which also allows to set the voltage you want it to start balancing. I am using active balancers on my lifepo4 pack so was unable to test the balance feature.

As far as longevity, the unit seems very well built. I like the ability to see the cells voltage in real time. I like it so far, cost me 86 dollars including shipping.

Thanks for that quick rundown on the Chargery. I’ve got the manual already. Quick question: does it do balancing?
1500W of Residual Thermonuclear Energy Collectors (6X250W 2S)
40A eSmart3 MPPT Controller
Raspberry Pi 3 remote monitoring
BATTERIES, Need Lots of Batteries!
800 18650 (80P10S= 40.0v) 4.1Kw
12Kw Pure Sinewave 36V Inverter
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#10
Daromer, can you name a couple of those BMS that cost more than batrium? I've seen some 'SMART BT BMS' really cheap, but I don't want to be spending money on stuff that does not work. I don't want to go back to 24V because I won't have room to grow.
1500W of Residual Thermonuclear Energy Collectors (6X250W 2S)
40A eSmart3 MPPT Controller
Raspberry Pi 3 remote monitoring
BATTERIES, Need Lots of Batteries!
800 18650 (80P10S= 40.0v) 4.1Kw
12Kw Pure Sinewave 36V Inverter
Reply


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