BVM-8s - new 1-8 cells battery monitor device?

[webfootguy]

Has anyone seen or used this new battery monitor device called the BVM-8s? It showed up on ebay this week.

http://www.ebay.com/itm/200682907061

[miuan]

Looks to me just like a celllog 8M. What's the black box for?

[Hyena]

I just came across these on ebay too. I googled for more info an up came this ES link at the top of the google search
They do indeed look like a clone of the cell logs, which is a good think considering they're currently back ordered at hobbyking
The benefit of these is they seem to come with an external alarm, so the main unit can housed inside your battery bag or enclosure with the small external alarm module mounted outside where you can hear it when it goes off.

I just bought one so I'll report back when it arrives.

[cor]

Wow, it's $11 so I ordered 2 for the 4 4s packs I have. Will report back in 3 weeks...

[toft]

Some new info/ report in BVM-8s topic?

[Hyena]

Mine arrived today, I made a video review to show its features.
The interface is identical to the cell log but has the added benefit of being able to specify the LVC alarm voltage. It also has a max delta V alarm, so if cells get out of balance by more than say 200mv then the alarm will trip too, which is kind of a cool feature.
The external alarm is quite loud, 90 db supposedly. I could hear it at 50km/hr over the wind noise (with the voltage set to 3.9v just to test it)
As per the video I'm not a fan of the 2 tone LCD screen but that 's fairly trivial.

Here's the video

[bobale]

The interface is identical to the cell log but has the added benefit of being able to specify the LVC alarm voltage. It also has a max delta V alarm, so if cells get out of balance by more than say 200mv then the alarm will trip too, which is kind of a cool feature.

My Cellogs have both of those features.

[toft]

Thanks for report.
Is there some kind of swich on/off? Or I need each time to mechanically unpluged when want to not using bike(for example after ride staying without possibility of charging for example 8 hours when I'm in a work)? Asking because its consuming energy so...
What is minimum alarm Voltage? (thinking of using with lifepo cells).

[Hyena]

The interface is identical to the cell log but has the added benefit of being able to specify the LVC alarm voltage. It also has a max delta V alarm, so if cells get out of balance by more than say 200mv then the alarm will trip too, which is kind of a cool feature.

My Cellogs have both of those features.

Really ? Is it the USB version or the cheaper version ?
Mine is the cheaper version but it's a year or so old, maybe they revised them more recently ?
I'll have to buy another one to check.

Thanks for report.
Is there some kind of swich on/off?

Nope, but putting a small switch in the first negative wire would turn the device off.
I'm actually keeping a look out for a single throw triple pole switch for just this purpose - to be able to turn all 3 off with the throw of a single switch.

What is minimum alarm Voltage? (thinking of using with lifepo cells).

I'll check tonight

[dumbass]

Does it indicate the max capasity (volts and MA) of the external alarm? I'm assuming it's like the CellLog8 and can handle a small relay.

Bob

[bobale]

Really ? Is it the USB version or the cheaper version ?
Mine is the cheaper version but it's a year or so old, maybe they revised them more recently ?
I'll have to buy another one to check.

They're the cheaper ones, bought 6 months ago. Are you absolutely sure yours doesn't have them?

[dumbass]

Hyena,

I forgot to ask......What was shipping time like? I assume normal 2 t o3 weeks.

Bob

[dumbass]

Just ordered 4 of them.......Hope their as good (or better) then the CellLog8s

Bet the price of the CEllLog8 will be dropping with the new competition.

Bob

[Hyena]

Does it indicate the max capasity (volts and MA) of the external alarm? I'm assuming it's like the CellLog8 and can handle a small relay.

Not sure, my cell log only has an alarm output option of a normally open or normally closed - I've never actually used it. The BVM looks like it just outputs a voltage on the alarm line. When you plug in the external buzzer it also uses that for the keypress beeps - which are much louder than the internal beeper in the unit.

They're the cheaper ones, bought 6 months ago. Are you absolutely sure yours doesn't have them?

Pretty sure, I'll check again tonight.
Mine are a good year old.

Shipping time was about 2 weeks - if you're ordering today you might get lucky but come tomorrow all of china will grind to a halt for the chinese new year holiday.

They're not THAT much cheaper than the cell logs - there's only $2-3 in it. I actually prefer the cell logs but they've been out of stock for ages. Ironically, last night they came back into stock again at HK.

[dumbass]

Shipping time was about 2 weeks - if you're ordering today you might get lucky but come tomorrow all of china will grind to a halt for the chinese new year holiday.

They're not THAT much cheaper than the cell logs - there's only $2-3 in it. I actually prefer the cell logs but they've been out of stock for ages. Ironically, last night they came back into stock again at HK.[/quote]

LOL, Isn't the a bitch.......I looked to order 4 CellLogs yesterday but HK showed they were still out of stock. That's why I bought these........O'well.....hope they work for me or I might have a fire sale. I use the external alarm through a NC relay. Based on your info I think these will work ok. They look like they have a little larger screen on them too.

Bob

[dumbass]

Hyena,

Any chance you could post the manual of this thing? It would be nice to real what they say about the external alarm.

Thanks,

Bob

EDIT: I was able to download a user manual from the internet, however, it's not very complete. But it does indicate that it has an extra alarm output that can be controlled by the user. SO I am assuming that the buzzer can be replaced with something like a relay. Time will tell...........

[cor]

The box itself has a beeper but its alarm output has a 3-wire cable which can be attached to an (included!) box with 2 buzzers producing 90 dBA each and a LED.
I am presuming that you can wire a relay instead of a buzzer.
I got mine for $11 each on Ebay. User Manual is included (2-sided printed and folded leaflet) but I can't say it is very clear.
For my 4x 4s packs, I plan on making a conversion wire to 8s so I can measure 16s with 2 monitors.
When I plugged the monitor into the Leadershobby 4s packs, the voltages were all over the map - from 3.8 to 4.1V
Unfortunately 1 pack had a cell that shows 0.6V so that is DOA. The other packs I must measure if they have the spec'ed cap and power.

[dumbass]

Yeah, the problem I found with the instructions is they really don't tell you much. And they hardly mention the external alarm. But what I need to know is if the ext alarm can be set for NC. And what voltage in the alarm output. I am assuming that it would be the same voltage as your pack which in my case is 24v each.

Bob

[cor]

Hi Bob,
I have not tried measuring the output of the BVM yet.
It does decent work in alerting when the voltage delta between highest and lowest cell gets over the configurable threshold or when any cell gets below the low voltage threshold (which can also be configured).
Here a pic (with my cellphone, sorry for the bad quality)
On the left are markings about the supported chemistries: Li-Ion, Li-Po, Li-Fe, NiCd, NiMH
On the right are 3 buttons: (up) Cell, (down) Mode and (enter) Menu
Default the display comes up with voltage measurement of 8 positions, unless you connect only one cell.

[dumbass]

Ok, thanks for the info. Looks a lot like the CellLog8 but I'm still worried that because they are supplying the voltage to that external alarm that it won't work for me. I need a NC external alarm. But we see what it does when they (4) arrive.

Bob

[auraslip]

I DO NOT WANT THE CELLLOG TO GET CHEAPER.

I WANT IT TO STAY THE HIGH QUALITY PRODUCT THAT IT IS!!!!!!!!!!!!

[cor]

Does anyone know how to use the bar-indication that comes up when you press "Cell" (up key)?
It always says 81% in my case and I am assuming it is an indication of State of Charge, though I have gone through a complete discharge/charge cycle without it moving, so I have the impression that it is stuck...
I have a LiPoly pack connected, currently all cells are above 4.23V and the bar is still sitting at the same 81% that it indicated two hours ago when I had discharged this pack so the lowest cell hit 3.000V.

[cor]

OK, my first experience with this BVM-8S: it seems reasonable accurate, my multimeter agrees with its readings.
Nice that you can configure the pack chemistry, but it does not give you an option to set a high voltage alarm, only a low voltage and a max delta between cells.
I am actually running two BVMs in parallel, each on a parallel string of 8s as I have 4 packs of 4 cells and I want to run 30V, so the two 10Ah strings add up to a 20Ah battery pack.
Now my main issue: can I switch off the BVM so it does not draw from the pack? I noticed that even when the voltages stay the same for a long time, its backlight still keeps going, slowly draining the pack. It seems that the only way to avoid that, is to plug it in every time you go riding and unplug it immediately afterwards. How is the Cell Monitor behaving?

BTW, an interesting thing was that the two BVMs showed the lowest pack voltage more than a whole voltage apart, this happened probably at the moment that I connected that pack to the bike (zap - charging up the capacitors) while the other pack got connected to the first, so everything was already charged and the lowest voltage was due to my riding the bike.
Starting voltage was 32.5V, finishing voltage 32.4V because I only rode up and down the street to test the bike. Low voltage on the first pack was 29.3V while the second (parallel) pack was 30.5V. Since they were parallel, their voltage cannot have differed while riding, only before connecting them parallel.
So, while this device is necessary to monitor the pack wile riding, it is not very convenient when you need to disconnect it every time (with the risk to screw up one time and short-circuit the series packs via their monitor wires if you accidentally get them in the wrong order)

[cor]

I am discovering a serious defect of the BVM-8S:
it appears that even when you connect 8 LiPo cells, they only draw from the first two cells!
So, they could not make their power supply work for up to 35V and therefor they will actively UNbalance a string? Bah!
I have these monitors on my 2 strings for about 30 hours since manually balancing all 16 cells pretty accurately - I have ran them in my bike for a few launches and overpass-assist (my own riding speed is higher than the 24V bike reaches, so I only use the assist for take-off from red light and hill climbing on overpasses)
Now I see that all cells are 4.0V *except* the first two cells of each string, those are 3.9V. Hmmm. Is that the reason that the display for the first two cells is yellow - those two cells are in the danger zone with these monitors?
Since the backlight of the BVM is not automatically switching off, they continue to draw major current from the first two cells, maybe as high as 1Ah per day, seeing that the first two cells are 0.1V down compared to the others...

[amberwolf]

There s a mod for I think the celllogs (or was it the battery medic?) to make them draw from all cells; maybe you could see if that wll also work on these?

Alternately you could mod it to draw power only from external aux battery and tape one to the back.