My initial plan was to go with the overkill solar BMS because of its simplicity and low temperature disconnect. However because of my 2000 watt inverter/charger it seems that the overkill solar does not have enough capacity. I considered putting two in parallel but I couldn't find anyone actually using a configuration like that just people theorizing. Any recommendations? I looked at the 200a smart daly but it seems kinda sketchy and the status of the low temperature disconnect seems questionable. This is my first build so I wasn't something simple and robust.
BMS recommendation for 4S 280ah battery
- Thread starter Gockleyd
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I am planning to use this renogy https://www.renogy.com/2000w-12v-pu...ihBRjqTtj4nzXDrmuGWRqWxzKxzUOwu8aAnG4EALw_wcB
If it has its own low voltage disconnect I would be less worried but the temp sensor is only for temperature compensated charging of lead acid
If it has its own low voltage disconnect I would be less worried but the temp sensor is only for temperature compensated charging of lead acid
John Frum
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By the weight of it I would guess its a low frequency inverter which is good.
I doubt that one has the modal remote switching capability I was looking for though.
I guess you need a beefier BMS.
Sorry I can't recommend one.
When l return home next week I'll test the low temp disconnect on my 200a Daly and see if it works ..... l know l had to change the setting via bt as it was on some random figure not relevant to earth lol ....something like -100 ? Can't remember
The high voltage disconnect works so far while l was charging in series , apart from that it seems fine so far , but its early days too.....
Mines in a caravan setup here in Australia so not too many days were it's gets that cold when we're on holidays and the van centrally heated anyway when it is cold outside
The high voltage disconnect works so far while l was charging in series , apart from that it seems fine so far , but its early days too.....
Mines in a caravan setup here in Australia so not too many days were it's gets that cold when we're on holidays and the van centrally heated anyway when it is cold outside
It's a Daly supplied by Basen with my batteries , they get them through Daly , just hasn't got Daly on it
Mines bt/ uart , ntc and monitor ported ,,,, no manual as such , so l just winged it ..... it seems consistency of supplied wiring for ports and manuals isn't a priority for them ....appears well built otherwise
I'm running active balancing as well
Mines bt/ uart , ntc and monitor ported ,,,, no manual as such , so l just winged it ..... it seems consistency of supplied wiring for ports and manuals isn't a priority for them ....appears well built otherwise
I'm running active balancing as well
Forgot to add , that Renogy unit gets not so good reviews on Amazon , l was looking at getting one too, think I'll stick with seperate units , l have had a good run with our 1000w Giandel in the past , so l might upgrade that as we only use it occasionally ..... might even make a soft start to cope with bigger surges
If l was depending on an inverter ld spend a lot more and get a good low frequency one
If l was depending on an inverter ld spend a lot more and get a good low frequency one
SoundinSpirit
New Member
Hey all... Just to chime in about the parallel use of the Overkill BMS, I am bench testing right now with no luck. I suspect I have a faulty BMS anyway, but both will allow 60 amps, increase the heat gun to 135 amps on high and they both shut off. One will auto reset from the overcurrent, the other gets locked into a "Discharge low" protection. This refers to low temp, I believe. Temps are 58 F and not an issue. I can hard reset (unplug balance leads) the one and it is good to go again.
To the thread topic though, I wired the two in parallel using a bmv-712 as well. Heat gun on low is 60 amps and they BOTH register 60 amps. bmv agrees. I would think the overkill bms would share the load though.... If I increase the load to 135 amps on high heat, they shut down.
I am open to ideas on settings to play with to make it all work.... Happy to share all the info too!
Reason for going the dual Overkill route is I will be ordering another set of four 280 amp hour cells soon...
I'm using the GoWIse 2000 pure inverter Will recommended. However, I JUST got it, so returning it is conceivable for a different one.
To the thread topic though, I wired the two in parallel using a bmv-712 as well. Heat gun on low is 60 amps and they BOTH register 60 amps. bmv agrees. I would think the overkill bms would share the load though.... If I increase the load to 135 amps on high heat, they shut down.
I am open to ideas on settings to play with to make it all work.... Happy to share all the info too!
Reason for going the dual Overkill route is I will be ordering another set of four 280 amp hour cells soon...
I'm using the GoWIse 2000 pure inverter Will recommended. However, I JUST got it, so returning it is conceivable for a different one.
Thank you for the real world experience.
I just got an email back from Steve at Overkill and he does not recommend paralleling the BMS's on one set of cells. Looks like I'm going to have to find another option or send like the new Daly smart BMS does have low temp based on what people are saying do I might go that route.
I just got an email back from Steve at Overkill and he does not recommend paralleling the BMS's on one set of cells. Looks like I'm going to have to find another option or send like the new Daly smart BMS does have low temp based on what people are saying do I might go that route.
WA5IDX
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I've planned on using two (2) Overkill 120A BMS units on my two (2) 4S batteries. I plan on connecting the positive terminals together but not the Negative terminals of the Batteries. That way each BMS "sees" only a single "input/output" and any load should be shared ( albeit maybe not equally) between the two BMS units.
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I have two 4s 280Ah batteries, each with their own Overkill Solar 120 amp BMS. I've pushed the draw to over 100 amps with no problem. Since I have a combined 240 amp capacity between the two BMS, a 100 amp draw is hardly pushing it.
Putting two BMS on the same battery does not seem reasonable to me.
Putting two BMS on the same battery does not seem reasonable to me.
Appreciate the clarification here. My plan has been this exact configuration so was quite nervous reading the earlier posts.
I too am a little confused as to why you would want 2 BMSs on a single 4s - to pull twice the current? Note, still new here and reserve the right to pull the newbie card.
I'm going to say it's one of these things:
1. Ignorance
2. Trying to do it on the cheap
3. They read it on the Internet
John Frum
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hypothetical but not unusual use case:
You have a 4s 280ah battery
You wish to put ~1c from your battery to run a large-ish inverter to full capacity on occasion.
You want to use the overkill solar 4s BMS because of @OverkillSolar's reputation for customer service.
The first hurdle is to see how close the BMSs and wire harness's are on voltage sense.
If they are "close" it should work.
Probably want to disable balancing on one of them though.
SoundinSpirit
New Member
Ok... Big update here!
I start a new thread for this too...
Dual Overkill 120 amp BMS running in parallel WORKS GREAT- though per Steve at Overkill, it is not recommended.
I have 4s 280 cells, grade A... my plan is to get 4 more, but I wanted to plan for that time about 2 months from now for shipping. I also have a 2000 watt inverter I wanted to run, which should draw about 180 amps under my planned, short duration, max load. Wiring the BMS modules using a Victron BMV-712 and a hobby load tester, I was able to see the 60 and then 135 amp draw split between the two modules. It is not a perfect 50/50 split, but close... The BMV was showing the load split and the BMS reflected this as well! Both BMS show the same cell voltage. Charging using a AGM charger at about 20 amps is working fine too.
Does it work? YES! There seems to be zero issue in doing this too while bench testing.
My WHY is explained above... The how is here to. I am actually using TWO battery chargers too. I DID want the reliability, local prep with wires, etc of Overkill. Also the Stateside shipping speed.
While I didn't read about it on the internet, I did watch Will's video using two 60 amp Daly BMS in parallel...
I thought this through and checked everything step by step very cautiously...
NOT doing it on the cheap either... the two Overkill BMS were about $250 with lugs crimped, etc.
For the next few camping trips, I will be good to go until the next four cells roll in, then I'll split the BMS modules up for the two separate 4s sets!
Pretty stoked!
My comment above and the issue I have with one BMS is temperature related? Maybe? It works fine until it hits high/low/overcurrent. then it gets locked out of self reset with discharge turned off. Working it out with Overkill, but probably a faulty module...
I start a new thread for this too...
Dual Overkill 120 amp BMS running in parallel WORKS GREAT- though per Steve at Overkill, it is not recommended.
I have 4s 280 cells, grade A... my plan is to get 4 more, but I wanted to plan for that time about 2 months from now for shipping. I also have a 2000 watt inverter I wanted to run, which should draw about 180 amps under my planned, short duration, max load. Wiring the BMS modules using a Victron BMV-712 and a hobby load tester, I was able to see the 60 and then 135 amp draw split between the two modules. It is not a perfect 50/50 split, but close... The BMV was showing the load split and the BMS reflected this as well! Both BMS show the same cell voltage. Charging using a AGM charger at about 20 amps is working fine too.
Does it work? YES! There seems to be zero issue in doing this too while bench testing.
My WHY is explained above... The how is here to. I am actually using TWO battery chargers too. I DID want the reliability, local prep with wires, etc of Overkill. Also the Stateside shipping speed.
While I didn't read about it on the internet, I did watch Will's video using two 60 amp Daly BMS in parallel...
I thought this through and checked everything step by step very cautiously...
NOT doing it on the cheap either... the two Overkill BMS were about $250 with lugs crimped, etc.
For the next few camping trips, I will be good to go until the next four cells roll in, then I'll split the BMS modules up for the two separate 4s sets!
Pretty stoked!
My comment above and the issue I have with one BMS is temperature related? Maybe? It works fine until it hits high/low/overcurrent. then it gets locked out of self reset with discharge turned off. Working it out with Overkill, but probably a faulty module...
John Frum
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What is the differential in voltage between the BMSs per cell?
Also how close are they to your dvom?
SoundinSpirit
New Member
Here is a screen shot of the cell voltages... Cell three is always a little off, but never more than a .09 variance. As these are new cells and I top balanced with a RC charger, AND am only using an AGM profile for bulk charging at 20 amps.... I will break the pack apart and top balance once more using a bench top lab charger I had delivered yesterday. With two DIFFERENT multimeters, one a cheap Harbor Freight and the other a good one, each cell is off from the BMS by .10 volts. This is the same for either BMS and when hooked up independently too. I can't figure out why. Voltage for the cell is being taken at the individual terminals.
Pack voltage is also off with the multimeter too. Though the BMS matches the Victron BMV-712 exactly.
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John Frum
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Each BMS will likely have a slightly different idea of each cell's voltage.
That is what I am curious about.
Also curious about how well each bms coincides with your "reference" meter.
As an aside my "reference" meter is my Mastech 8268 which cost less than a third of the price of my Klein cl390.
SoundinSpirit
New Member
@smoothJoey
The two BMS match right on...
This is the meter I have, but I am going to exchange it for the AC/DC clamp model... I thought this one had DC, but realized it did not... I really have found the clamp part nice. I bought it in trouble shooting an Air Conditioner- furnace problems in our new trailer. I tore everything apart only to find a stupid bad diode in the 12 volt line at the Air Conditioner board. It kept blowing fuses on one zone of the trailer. I didn't want to take it to the dealer and have them keep it for a month. Lo...
The two BMS match right on...
This is the meter I have, but I am going to exchange it for the AC/DC clamp model... I thought this one had DC, but realized it did not... I really have found the clamp part nice. I bought it in trouble shooting an Air Conditioner- furnace problems in our new trailer. I tore everything apart only to find a stupid bad diode in the 12 volt line at the Air Conditioner board. It kept blowing fuses on one zone of the trailer. I didn't want to take it to the dealer and have them keep it for a month. Lo...
Klein Tools 400 Amp Digital Clamp Meter, AC Auto-Ranging with Temp CL220 - The Home Depot
The CL220 measures AC current and NCVT via clamp and AC/DC voltage, resistance, and continuity via test-leads, and temperature with thermocouple. The meter features automatically ranging True Root Mean
www.homedepot.com
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