I’m working on a custom DIY battery box and using a SmartShunt IP65 Battery Monitor (500A) to track the state of charge. However, I’m not getting consistent or accurate readings, and I’m hoping someone can point out what I might be doing wrong.
Current Setup:
2 x 12V batteries chained together (parallel).
Negative from the battery chain is connected to the SmartShunt input, then output.
Temp monitor connected (though I’m unsure if it’s necessary for me anymore so I can remove)
Positive to battery positive.
Aux to battery negative for the temp sensor
I followed the diagram for the temp sensor, except I’m chaining two batteries instead of using just one.
App Settings:
Capacity: 210AH.
Charged Voltage: 13V (measured after a full charge and waiting overnight).
Synchronize SOC to 100% when batteries were at full charge.
All other app settings are default.
Issues:
The app reads voltage and output values correctly, but the time remaining never seems accurate.
After a night of discharge, SOC shows 70%, but if I disconnect/reconnect the batteries (power cycling the shunt), the SOC resets to 100%.
Questions:
Does the SmartShunt need to stay connected at all times, even during charging?
Are my app settings incorrect for this setup?
Can the SmartShunt be turned off when not in use? (I’m using this for astrophotography equipment, so it’s not always needed but could stay hooked up in a car if that’s okay.)
Future Plans:
I’m planning to add two more batteries and want to ensure I set everything up correctly. Below is my planned setup:
Chain 4 x 12V batteries in parallel.
Negative from Battery 4 connects to SmartShunt input, then SmartShunt output splits into two negatives.
Positive aux links to Battery 4’s positive, which also splits into two positives.
The split is intended to minimize voltage drop over a 50ft run (from my car trunk to equipment in the field). I can’t keep lugging 60lb battery boxes back and forth!
Each positive line is fused and fed into separate DC-DC 0-36V in / 12V out stabilizers (I haven’t tested these yet but hope they help reduce voltage drop). The outputs from the stabilizers are linked back into a single line that goes to the equipment, so voltage and SOC should still match.
Concerns:
Is my setup feasible?
Would moving the SmartShunt to the end, after the DC-DC stabilizers, impact its ability to track accurately due to voltage drops?
Thanks, sorry about that, thank you for the manual link, I havent seen that one, just the one provided.
The battery is -
Lead Acid EverStart Maxx Marine Battery, Group Size 29DC
12V, 845 CCA, 114AH
I will review the manual for some settings
Thank you for the note on the shunt being powered 24/7 (I assume that means during charging as well), it looks like the temp rating should suffice to be left in a tesla frunk
If I can clarify, what is the correct way of connecting the shunt to 4 batteries in parallel?
Shunt remains connected at all times, during charge and discharge.
There is a setting on it that keeps its SOC when it is reconnected. (Near the bottom -battery soc on reset)
Wiring parallel battery banks wrong can result in over working one battery and under working another. Download Victron’s guide “Wiring Unlimited”, link below and read chapter 3. Connecting both positive and negative to the end battery is wrong regardless of 2, 3 or 4 batteries. Wiring Unlimited
When deciding what cable to use for your 50ft do not choose it based on current rating, but do a proper voltage drop calculation and try to keep that low, the normal recommendation is 3%. Remember the voltage drop will result in more power being required to compensate. Voltage drop calculators are available on line or in the Victron Toolkit app.
When running the system make sure that you unroll all the cable even if you do not need it. The resistance of the cable will generate heat and needs free air to cool. Keeping it rolled up can result in overheating. Choose a flexible multistrand cable.
The SmartShunt has to be at the battery to read the current that is being taken from the battery. You can not put it after the voltage stabilisers because the current after stabilisation will be different to the current feeding the stabilisers to to inefficiency losses and voltage conversion.
Your system is feasible as long as you size the 50ft of cable correctly as noted above.
Thanks for that info, the online manual and Wiring Unlimited pdf is very helpful, I wish there where links to that in the item main page or amazon.
If you dont mind, does this set up seem better as far as wiring? Is there any issue, with adding/removing 2 of the batteries as needed and just updating the max amp hours in the settings? I was hoping to have the flexibility of using 2 batteries for normal usage and adding the other 2 when more is needed. Since they are all 4 charged at the same time, and based on the new diagram via the bus bar, the voltage should be the same unless im mistaken, just the amp hours needs adjusting
With the bus bar design it is easy to add/remove a battery or 2 and just update Ah setting. The new wiring is better. As above, aux is only for 2 12V batteries in series for 24V.
Thank you very much for the feedback; it’s been extremely helpful. I have a few follow-up questions:
I’m currently using a regular 15A automotive battery charger, but it’s a bit frustrating because the charge times are inconsistent. I noticed there are less expensive versions of the Blue Smart chargers (5A/10A). Would those be sufficient for charging a 4-battery setup, or is the Victron Energy Blue Smart IP65 12V 15A Battery Charger the correct one to use?
Regarding the temperature sensor connection for the SmartShunt—would it still be effective in a chained setup if the sensor’s positive connection is on the bus bar? I’ve only seen diagrams with a single battery, not a bank of them.
I came across the Battery Balancer, which isn’t too expensive. All 4 batteries are the same brand, bought at the same time, and I haven’t noticed any voltage differences when charged in series. Is a balancer necessary for proper charging, or should my current setup be sufficient?
@nichols89_ben Hello Ben, it sounds like you do some interesting field work.
I know this is probably not what you want to hear but Lithium batteries would make life easier for you.
Firstly they are much lighter than the batteries you are using. The weight difference is significant, especially if you are changing the location of the batteries at all.
Secondly, they have a deeper depth of discharge allowed without damage. The lead acid type batteries should not really be discharged beyond 50% whereas the Lithium can be discharged quite low, lets say 10%. In other words you get practically twice the useful capacity out of Lithiums.
Thirdly, Lithiums charge so much faster than lead acids. They just charge at full current until the last 5 minutes and then simply stop. Lead Acids tend to very slowly get to full charge so the difference is remarkable.
Yes they are more expensive but the price difference is narrowing over time. They last longer and have better specifications . I thought it worth mentioning before you expand to more batteries.
I am not familiar with the Victron chargers but any one will be better than an automotive units as they have proper charging algorithms. With 4 batteries the higher charge rate will be best.
The battery balancer is only for batteries in series, so 24V, 36V or 48V made from 12V batteries. It does not work for parallel, these by nature stay balanced.
The temperature sensor must be connected to a battery to sense its temperature. If you do not use temp sense then you can connect voltage sense to the bus bar.
Man, when I was looking at battery options back in June, I quickly ruled out lithium because of the price. But after your comment, I took another look and realized I must have been checking out the wrong ones (like the $900 100AH BattleBorn). I found some off-brand options (https://www.amazon.com/dp/B0CRB118TG?th=1) for 100ah $170 12v mini, which is much more doable. I went ahead and bought 4 of them and returned the lead-acid ones I picked up last week. After running the numbers with the discharge rate, I’m happy with the decision, plus it’s 80 lbs instead of 240 lbs. I’ll definitely feel it in a few weeks when I balance my budget, though.
Thank you, your answers have been very helpful. I’ve decided to go with lithium batteries, so I’ll need to make some updates.
Temperature Sensor:
Would measuring the temperature of a single battery still be beneficial? I initially got the sensor because my batteries were stored in a plastic tub out in the field and left on the ground overnight, and I was concerned about temperature affecting performance. My new setup has them stored in my Tesla frunk, so I’m not as worried about it now.
Bluetooth Range Issue:
Is there a better solution for extending the Bluetooth range? I saw this is a common issue when trying to check power from my car while the shunt is about 10 feet away. I set up a voltage alert, but without a connection, it doesn’t notify me. According to the SmartShunt manual, adding a VE.Direct Bluetooth Dongle could solve this, but it says doing so “will not support stored trends, Bluetooth GATT service, or the Keep SOC option.” How crucial are these features?
Display Option:
I know the SmartShunt is app-only, but I didn’t see an option for adding a simple display to show the voltage in case my phone dies. I have a basic 200A Watt Meter Power Analyzer and was thinking of adding it to the setup. Are there any issues with doing that?
Lithium need to be above -20degC to discharge and above 5degC to charge. The battery BMS usually looks after this.
Voltage sense means the small red wire.
If you want better bluetooth range and a display look at the BMV-712. The items not supported by the dongle are not important. The BMV-712 display unit has a relay you could connect a buzzer to and set up a low SOC audible alarm.
Thanks again, its too late to swap out the smart shunt, but I just want the screen to show basic voltage and not all the bells and whistles. It seems the dongle is still the best solution for range aside from what you suggested so I may give that a whirl and see if it helps.
