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.

 

[NWIP]

Thanks for your view/input. I can’t convince DW on solar, so unless something changes there it is not in my future. When I did ME-BMK on 2017, my cousin who has solar with lithium batteries tried to get me to go with Victron. He doesn’t have AGS on his 5er and I just couldn’t see need for redundancy. Getting ready to install ME-BMK on new coach and looking for different viewpoint. Very helpful.

 

[Chuggs]

Glad it helped...

I installed ME-BMK originally. It showed SOC, (State of Charge) and allowed me to reset the aH used counter so, that I could make a record of use over a period of time. This was very useful, both for future planning...but more importantly helping me decide how much solar to install.

I was flabbergasted to find...I could not use the ME-BMK SOC as a trigger for the ME-AGS-N, unless I also upgraded the remote from the ME-RC that came std. and the Advanced ME-ARC remote. So, I changed out remotes as well.

I’m not sure how much reading you’ve done...forgive me if you already know...but just to warn you. Magnum Inverters will attempt to ground themselves thru sensitive network devices if the NEG - lead to the Inverter is removed while the POS + is still attached. To prevent damage, whenever you need to remove cables from the battery, such as installation of the Shunt for a battery monitor...PLEASE remove the Inverter POS + lead first...and reattach it last. It’s easy to do by removing the cable from the 350A catastrophic fuse and wrapping the terminal carefully with electrical tape. If the inverter tries to ground itself thru the BMK, or AGS module...it can fry their brains...

 

[Neal]

Great option and easy mod to install a cutoff switch on the inverter line for this reason as well as others.

 

[NWIP]

I may look at doing the cutoff at the same time as ME-BMK. I was able to remove ME-ARC from 2017 coach so I already have that. This will be second one so hope to improve on first install.

 

[Jim]

So yes, I turned the shore power off and then turned some lights on/off until I found the 20 amp draw I was looking for. (I suspect the inverter was 5-6 amps by itself.) I took a battery voltage reading off the meter, and then came back 4 hours later to take another reading. It' was just math from that point on although I'm going to go back down in a few minutes and get another reading as 4:45 will be the actual 6 hr mark.

Bad batteries?

I sent the data (that I had compiled over the last couple of days) to the manager of the store I bought the batteries from. He in turn, sent it to then manufacture. This morning I got a call from a representative of Crown Batteries. I'm not going to say he was rude, but he was quite direct and through a barrage of quickly asked questions, he determined (in his mind anyway) that the batteries were damaged because I was charging Flooded Acid batteries on the AGM setting.

I hadn't considered this. From what I've known about AGM batteries, they want to be charged with a lesser amperage so that they will charge slower. But I can't see how a lower amperage would damage a flooded acid battery.

At the end of the conversation, he offered to refund my money, which is good. (I hadn't asked.) But for future reference, and to make sure I understand as much as I can about batteries, does anyone feel his theory has merit?

 

[Chuggs]

it’s a give or take...too much current you erode plates prematurely, ....not enough and you allow sulphate deposits to remain on the plates, robbing you of storage capacity. I’m not a battery engineer, somI just try my best to follow they mfg. settings.

 

[Jim]

it’s a give or take...too much current you erode plates prematurely, ....not enough and you allow sulphate deposits to remain on the plates, robbing you of storage capacity. I’m not a battery engineer, somI just try my best to follow they mfg. settings.

The other part of this story is that the batteries were in my previous coach, and the charger was set for flooded acid batteries. When I sold the coach, i moved the batteries to this coach, and they were only in this coach for 3 weeks. During this time they did nothing except sit there on float mode.

I told him this but he wasn't impressed. He also mentioned that the size of my battery bank was 860 ah and the charger probably wasn't putting out enough amperage to keep them happy. I can see how this might happen, but still not sure...

 

[Jim]

OK, I looked at the specs and my Phaeton has a 100amp converter, so I doubt it would have any problem keeping the battery bank charged. So I'm left to wonder, what would make 4 of these batteries fail in such a short time?

 

[TJ&LadyDi]

In your first post, @Jim, you said you bought the batteries for your solar conversion project but now say you removed them from your previous coach. How old are these batteries?

These are big batteries...much larger capacity than used in most coach applications. I'm now wondering if the charging system in your previous coach was actually keeping them properly charged. If not, it might only take a relatively short period for them to sulphate up. Because of their large capacity, the undercharging might be disguised until serious damage was done.

Since it appears that you will be reimbursed by the manufacturer, this might be a good time to start afresh and engineer a new battery system that includes a charging system designed specifically for high-ampacity batteries.

TJ

 

[Jim]

In your first post, @Jim, you said you bought the batteries for your solar conversion project but now say you removed them from your previous coach. How old are these batteries?

Yeah, I guess that sounds a little contradictory, doesn't it?

I bought the battery's on April 2nd 2019 and put them in my first coach. As that was an older coach with no inverter, I bought a inverter/charger to maintain them and to use in the planned conversion. Link to the inverter here.

The solar conversion was originally planned for that coach., but after pulling some of the 8% grades out here, I decided i needed a DP over the V-10. So i took all the solar stuff out and moved it over to the new DP.

I guess it's possible that the inverter/charger wasn't keeping that batteries charged but I seriously doubt it. It was a good inverter/charger and should have maintained the batteries well.

In your first post, @JimI'm now wondering if the charging system in your previous coach was actually keeping them properly charged. If not, it might only take a relatively short period for them to sulphate up. Because of their large capacity, the undercharging might be disguised until serious damage was done.

Perhaps, but again, I doubt it. We were in a "rehab" state with the coach at that time so the coach remained stationary and the batteries never saw any use. They remained connected to shore power and should never have discharged enough to need the inverter/charger to "catch up".