Bad Batteries?

[Neal]

It looks like the ME-BMK is 500A/50mV if that matters.

 

[sheridany]

It looks like the ME-BMK is 500A/50mV if that matters.

did you install ME-BMK yourself?

 

[Neal]

Yes I did, coached by @Chuggs

 

[sheridany]

Is bribery a punishable offense on the forum?

 

[Neal]

Salivating...if only I could remember how to do it. A lot around here have done it, I suggest read the ME-BMK installation instructions and see how you feel about it. Mine was a bit more complex due to the mounting location on the back wall of the battery bay, some actually mount it to the top of the batteries I think which seems easier to deal with.

Magnum ME-BMK Manual

Magnum Energy Battery Monitor Kit Manual

rvforums.com

 

[Chuggs]

shunts are measured in two ways...the ampacity and the voltage drop across the shunt.

50mV/500A is very common. So, the first thing to do is buy a shunt capable of carrying the current. If you run a blow dryer, or a microwave, on inverter...you’re pulling more than 100A.

i have measured over 164A coming off my battery bank while doing certain things... So, a 100A shunt would not be ideal.

The next is the voltage drop. The shunt is basically a resistor...when current is flowing, the restriction (slight) causes a measurable drop in voltage. 50mV per 500A. This is what the circuitry is measuring to provide an Amp reading.

The ME-BMK comes with a 50mV/500A shunt...and the module is preprogrammed to read this...no user adjustment there.

The BMV-712 comes with a 50mV/500A shunt...but the device can be setup via Bluetooth...or thru the remote display device with buttons. The BMV-712 can be programmed to accept shunts of varying sizes...

On a side note... we run Victron for Solar and Magnum for inverting. The best of both words is having both the ME-BMK to interface with the Victron components...and the ME-BMK to interface with the Magnum components. The Magnum gives you the ability to add SOC to the component mix...such that if you have a networked AGS you can use SOC v. Voltage. Or when running off a 30A Shore power...you can change the AC-IN to SOC. But this also requires the ME-ARC remote to replace the ME-RC remote,,, Anyway, should anyone find themselves in a similar situation wanting to run two battery monitors...then you can order a ME-BMK-NS ..,which comes with No Shunt. The orange and blue sense wires can be piggybacked into the Victron BMV-712 shunt...using the two screws that secure the circuitboard to the shunt. Both meters will be looking at the same exact mV reading. And you don’t have to wire in two shunts in series...

 

[Jim]

If you run a blow dryer, or a microwave, on inverter...you’re pulling more than 100A.

i have measured over 164A coming off my battery bank while doing certain things... So, a 100A shunt would not be ideal.

Thank you for that explanation, Chuggs.

Question: If I were to exceed 100A while using a 100A shunt, would there be a problem? An overload of some kind or possibly even a fire?

 

[Chuggs]

I honestly don’t know. Operating outside the range of the device could cause errors...or perhaps the shunt will just get warm to the touch... I do recommend that you take a reading of the shunt with a handheld IR thermometer. If you see it getting hot...I wouldn’t leave that load unattended...and would abandon that device pretty quickly. Safety is paramount.

The RV geeks did a piece quite a while back in their Winter Secret Weapon. They basically installed a dedicated branch circuit for running a space heater. It allows them to power this single outlet from the 20A gfci outlet on most pedastles. This way their heater isn’t running off the inverter, or taking anything from the power available to the other coach systems running off the shore power cord. I added an outlet like this...in our bedroom. I normally use the block heater to power it when we just use it to power a small draw like a fan. If I wanted to use a heater, or plug in a circular saw...I would run the heavy ga. extension cord to the pedastle to get the full 20A available in that outlet.

Genrally, we stick to Oasis (diesel) power for hot water and heating when running off batteries.

As far as battery measurement and health go...

The most difficult thing is Peukerts effect. In a perfect world...drawing 100A for 1 hr would remove 100aH from the battery. Unfortunately...the only point where this is true, or at least should be true is at the 20hr rate used for rating the battery. At higher amp draws...you actually take more out due to the Peukert effect. So just as a let’s say... 100A for 1 hr takes 120aH out. Not fair right? Some battery monitors can be programmed for this...others can’t. It obviously can induce error.

There are quite a few graphs which show approx. SOC for lead acid batteries at varying loads expressed as C/x... C1, C/10, etc... amps based on a fraction of battery bank capacity.

if you track this...you will get some idea of battery health. Also taking specific gravity readings from batteries which have been disconnected and allowed to rest for at least two hours.., You might regain some storage thru equalization...but it depends on how long the sulphate shave hardened on the plates as to wether or not you will see results.

I am seeing degradation on my four year old batteries. I may be getting all new Lifeline AGMs before going to the balloon fiesta next year. Until then...I can live with the degradations...as we still have plenty of amp hrs for normal use. Just really like it all when dry camping for over a week... gotta have power to run the espresso machine

if you find a large golf cart place...might see if the have one of those inductive spectroscopy devices. They can basically read your batteries capacity, and SOC in a matter of seconds using a quick load analysis. Expensive device...but if you had a large fleet of golf carts it would be nice to have.

 

[NWIP]

Question, if not running solar is there any advantage to the Victron BMV-712 vs ME-BMK.

 

[Chuggs]

Question, if not running solar is there any advantage to the Victron BMV-712 vs ME-BMK.

Well...this has many answers...

If you don't need or want to network your Battery monitor to a Magnum Inverter system...then if choosing a stand alone battery monitor...get the Victron. Otherwise the ME-BMK would be the better choice.

If you are adding a ME-BMK by Magnum and do not have any Victron components...then Bluetooth monitoring and other Victron BMV displays is all you'll gain...unless adding some other Victron components.

If you do plan Solar at some point. I do recommend Victrons charge controllers...then with the optional temp sense for the BMV...your controller will be able to see real amps, real volts, and adjust charge parameters based on battery temp...for lead acid chemistry. They communicate via BTLe...and they call it VE.Smart networking. It's wireless.

Finally, for those who wish to remotely monitor thier system...the Venus GX is one of the many GX systems that Victron offers, and the BMV would ve.direct cable connect to the Venus for recording your systems status on the VRM network. Magnum offers Magweb.

So, it really depends on how much data you want and how you wish to access it.

I will admit to not being very impartial. I tripped into getting Victron components...and they have far exceeded my expectations. The Bluetooth interface with Smartphone, Tablet, or Laptop is super easy, and will notify you of updates to firmware...which they make very easy to install. I really only use the ME-BMK to enable AGS features or AC-IN features via SOC parameter. It can adjust charge output thru the shunt based on Amps if you select CC/CV charge mode...on a ME-ARC remote.

Basically...th Victron has more capabilities...it just depends on whether or not you want/need these.

Sorry, a lot of points....and no guarantee I answered your question...but I took a stab at it.