Battery Monitoring System

[Karlos]

Hello all,

Still figuring out my new-to-me 2018 Open Road 32SA and making additions and modifications. My current focus is learning to live with my residential refrigerator. It's kind of a love/hate relationship now: love the size and performance, but hate the battery drain when we want to dry camp.

My house battery system consists of four 12V deep cycle lead-acid batteries in parallel. I would change it to lithium, however they are less than six months old. The total rated capacity is 324Ahr, but since they are lead-acid cells, I am planning on depleting only 200Ahr before recharging. That would drain the bank down to about 40% capacity. Anyone see issues here?

I would like a real-time battery monitoring system (BMS) to track this usage. This would typically involve a shunt and some intelligent measurements. The Spyder system in my rig provides only voltage readings for house and chassis batteries. According to the Spyder support people, the "Spyder system does not have a shunt in it. We read the voltage from a 12v input wire into the RSI-9 board on the back of the G6 panel. So adding a shunt should not affect the chassis voltage reading on our system."

To roll my own BMS, I plan to add a shunt at the negative terminal (or close to it) of the house bank and a "smarter" battery monitor. I was initially planning on using the Victron BMV-712, but the $200 price tag turned me off. Instead, I purchased a highly reviewed clone for under $50 with 350A max current shunt, rather than the 100A version. I probably could have gotten by with the 100A version, but my 1200W inverter can draw 100A at full usage from these batteries. Anyone see issues here?

Here is the monitor and shunt info: https://www.amazon.com/dp/B07FGFFHC6...t_details&th=1

Ultimately, I will switch to Lithium batteries and add solar charge capability, but that is down the road.... Thanks for any suggestions.

cheers,
Karl

[EngMarc]

Originally Posted by Karlos

Hello all,

Still figuring out my new-to-me 2018 Open Road 32SA and making additions and modifications. My current focus is learning to live with my residential refrigerator. It's kind of a love/hate relationship now: love the size and performance, but hate the battery drain when we want to dry camp.

My house battery system consists of four 12V deep cycle lead-acid batteries in parallel. I would change it to lithium, however they are less than six months old. The total rated capacity is 324Ahr, but since they are lead-acid cells, I am planning on depleting only 200Ahr before recharging. That would drain the bank down to about 40% capacity. Anyone see issues here?

I would like a real-time battery monitoring system (BMS) to track this usage. This would typically involve a shunt and some intelligent measurements. The Spyder system in my rig provides only voltage readings for house and chassis batteries. According to the Spyder support people, the "Spyder system does not have a shunt in it. We read the voltage from a 12v input wire into the RSI-9 board on the back of the G6 panel. So adding a shunt should not affect the chassis voltage reading on our system."

To roll my own BMS, I plan to add a shunt at the negative terminal (or close to it) of the house bank and a "smarter" battery monitor. I was initially planning on using the Victron BMV-712, but the $200 price tag turned me off. Instead, I purchased a highly reviewed clone for under $50 with 350A max current shunt, rather than the 100A version. I probably could have gotten by with the 100A version, but my 1200W inverter can draw 100A at full usage from these batteries. Anyone see issues here?

Here is the monitor and shunt info: https://www.amazon.com/dp/B07FGFFHC6...t_details&th=1

Ultimately, I will switch to Lithium batteries and add solar charge capability, but that is down the road.... Thanks for any suggestions.

cheers,
Karl

I have the BMV-712 and love it. Very well connected and the bluetooth app lets you do everything for settings and virtually anything you can do on the display.

[TacomaJoe]

I have the AiLi (actually 3 of them). It tracks my Bluetooth enabled lithium batteries very close. At first I had it mounted on my battery on the tongue. I extended the cable so that the display was convieniently located inside the trailer. I have since converted to lithium, moved them inside and all is good.

[Mark_K5LXP]

That would drain the bank down to about 40% capacity. Anyone see issues here?

The more accurate your battery monitor the closer to 0% you candraw down the batteries. Only drawing down your battery to 40% is extra "safe" but for the most part unnecessary- reducing your operating time, operating the genset more often and ensuring the batteries age out and not wear out. Taking them down to 20% is just as "safe", if you monitor them carefully then 0% is OK.

I probably could have gotten by with the 100A version, but my 1200W inverter can draw 100A at full usage from these batteries. Anyone see issues here?

I don't know the specifics of this monitor but generally when you use a higher current shunt, low current accuracy can suffer. That might matter if you typically draw low power most of the time. Going the other way, with a low current shunt the unit may not count Ah correctly when above the shunt rating. A closer review of the spec's should reveal how it works, or a call to their tech support. I would be inclined to go with the 100A shunt if that's all the higher you anticipate going, unless say the monitor only goes to 99 and won't read higher than that.

Mark B.
Albuquerque, NM

[Karlos]

I'm looking at where to mount the new BMS shunt, and decided that directly attaching to the battery would present a mounting problem.

Immediately to the right of my battery bank is a panel that contains my battery shut-off switch, the inverter shut-off as well as the battery merge solenoid. I haven't opened things up in that panel yet, but it seems like a perfect place to mount the BMS shunt.

Has anyone out there been in that panel, or installed a shunt in that panel?

cheers,
Karl

[SteveJ.]

Originally Posted by Karlos

Hello all,

Still figuring out my new-to-me 2018 Open Road 32SA and making additions and modifications. My current focus is learning to live with my residential refrigerator. It's kind of a love/hate relationship now: love the size and performance, but hate the battery drain when we want to dry camp.

My house battery system consists of four 12V deep cycle lead-acid batteries in parallel. I would change it to lithium, however they are less than six months old. The total rated capacity is 324Ahr, but since they are lead-acid cells, I am planning on depleting only 200Ahr before recharging. That would drain the bank down to about 40% capacity. Anyone see issues here?

I would like a real-time battery monitoring system (BMS) to track this usage. This would typically involve a shunt and some intelligent measurements. The Spyder system in my rig provides only voltage readings for house and chassis batteries. According to the Spyder support people, the "Spyder system does not have a shunt in it. We read the voltage from a 12v input wire into the RSI-9 board on the back of the G6 panel. So adding a shunt should not affect the chassis voltage reading on our system."

To roll my own BMS, I plan to add a shunt at the negative terminal (or close to it) of the house bank and a "smarter" battery monitor. I was initially planning on using the Victron BMV-712, but the $200 price tag turned me off. Instead, I purchased a highly reviewed clone for under $50 with 350A max current shunt, rather than the 100A version. I probably could have gotten by with the 100A version, but my 1200W inverter can draw 100A at full usage from these batteries. Anyone see issues here?

Here is the monitor and shunt info: https://www.amazon.com/dp/B07FGFFHC6...t_details&th=1

Ultimately, I will switch to Lithium batteries and add solar charge capability, but that is down the road.... Thanks for any suggestions.

cheers,
Karl

I have a different brand but it looks identical to mine. It's been working well for 2+ years.

IIRC, the instructions say to mount it to the negative cable. Do install some protection to keep the shunt clean and dry.

We use ours on L/A batteries. With solar and mostly dry/dispersed camping it comes in quite handy. The gauge light on it makes a great night light.

[High Road Travelers]

Originally Posted by Karlos

I'm looking at where to mount the new BMS shunt, and decided that directly attaching to the battery would present a mounting problem.

Immediately to the right of my battery bank is a panel that contains my battery shut-off switch, the inverter shut-off as well as the battery merge solenoid. I haven't opened things up in that panel yet, but it seems like a perfect place to mount the BMS shunt.

Has anyone out there been in that panel, or installed a shunt in that panel?

cheers,
Karl

You might want to check if your recall fix has been performed on that panel to the right of your battery bank. For your model the recall was to tighten the lugs inside the panel (Tiffin Recall #TIF-120).
I have the same model, but have four 6 volt lead acid batteries with the same 1,200 watt inverter and residential fridge. We don't boondock very much, but do alright by running the generator in the morning and at night for an hour or two.
You have a nice rig and with Lithium and solar you can do just about anything you want to. Hope you find a good BMS.
Thanks,

[EngMarc]

As I've said more than a few times, I've been very happy with the Victron BMV-712 that came on my Tiffin.

It has a lot of features including bluetooth app management, ability to dynamically start/stop external relays such as AC or Genset and is easily interfaced with the central monitoring systems from Victron.

So is the $200 worth it - YES in my opinion. It works flawlessly and just as described.

A a solid investment.

Just my $0.02 worth,
Marc

[jpspaz]

I am running a Victron smart shunt off the negative cable and three 12V AGMs. I had four GC2 lead acid 6v batteries prior wired in series parallel. You mention running them down to 40%. The recommendation for lead acid is 50%. Anything lower could damage them. I was very close to getting lithium but having to swap out my inverter, add a DC to DC charger, and rewire everything was just something I didn't want to spend the money on at this time. I have a propane/electric fridge so I can manage with my current set up as we don't boondock all that often.



My only complaint about the smart shunt is the range on it. I need to be very close to it to get a reading on my phone.

[Mark_K5LXP]

The recommendation for lead acid is 50%. Anything lower could damage them.

You can pick any arbitrary discharge point you want for a variety of operational reasons, but the above "damage" statement is false. Discharging a battery to any depth within manufacturer specification (which usually includes 100%) does not damage a battery, any more than driving on tires causes them to be damaged or motor oil to be damaged by running the engine.

Mark B.
Albuquerque, NM

[twinboat]

Look at the depth of discharge charts .

Nowhere does it list a " Damage " area above 10%

[Karlos]

I just purchased the Victron SmartShunt for my battery monitor, and will return my AiLi shunt. Here are my reasons:

System Expandability. I plan to switch to lithium batteries and add rooftop solar eventually. I'd like to select components that can handle that evolution rather than need to be replaced. Victron has a wide range of products that integrate well to add future capability.

Data logging. I'm currently in the phase of understanding my power consumption patterns in order to size the future battery bank and solar install. Victron provides better data logging capability than the AiLi, and has a nice smart phone display via the Bluetooth app. (I recognize the short Bluetooth range. I can deal with that in the short-term, and will improve it when I integrate the Cerbo GX and it's control panel.)

Water Resistant. The SmartShunt is available in an IP65 version. Since my basement slide-out battery box is somewhat open to the elements, the weather-hardened version gives me more mounting options and doesn't require me to enclose it.

Thanks for all your comments. It helped me firm up my decision.

Karl

[thegats1]

Originally Posted by twinboat

Look at the depth of discharge charts .

Nowhere does it list a " Damage " area above 10%Attachment 405738

True, but good luck getting a flat discharge curve to allow getting to 10% over a reasonable stretch of time. In my experience, the time to get to 10% after 50% on the amp-hr curve is pretty quick. But, I agree with your post. With a BMS you can at least watch it and take action before cell reversal occurs.

[Mark_K5LXP]

True, but good luck getting a flat discharge curve to allow getting to 10% over a reasonable stretch of time.

This is an consequence you'd see with any battery that has much of a terminal voltage delta across it's state of charge. The terminal voltage isn't flat, so a delivery of constant power requires an ever increasing number of amps. So yes, going from 50% to 10% happens quicker than 90% to 50% with a constant power load. Peukert plays a role here as well. It's not about the 50% Rule, it's just how they work across a range of SoC. No question lithium is "better" in this regard but properly implemented lead can work OK across the entire SoC range too.

Mark B.
Albuquerque, NM