12v lithium battery capacity meter (house battery)

sportcoupe · 10-03-2022, 09:01 PM

I have two 100ah lithium house batteries. Can someone recommend a simple 12v lithium battery capacity meter for my house batteries that fairly accurately reads percentage battery life remaining? I don't want to memorize voltages

I'd prefer one without a shunt on house battery negative. I have one like that but when my BIM connects to chassis battery, the house battery AH percentage remaining is no longer accurate.

Beau388 · 10-03-2022, 10:35 PM

Quote:

Originally Posted by sportcoupe

I have two 100ah lithium house batteries. Can someone recommend a simple 12v lithium battery capacity meter for my house batteries that fairly accurately reads percentage battery life remaining? I don't want to memorize voltages

I'd prefer one without a shunt on house battery negative. I have one like that but when my BIM connects to chassis battery, the house battery AH percentage remaining is no longer accurate.

You cannot accurately measure battery capacity or DC usage without a shunt. If there is only one ground hooked to the house batteries, the shunt should give you a good reading even if the positive current is coming in from the alternator. Yes I know the elections flow in the opposite direction of the current.

sportcoupe · 10-03-2022, 10:54 PM

Quote:

Originally Posted by Beau388

You cannot accurately measure battery capacity or DC usage without a shunt. If there is only one ground hooked to the house batteries, the shunt should give you a good reading even if the positive current is coming in from the alternator. Yes I know the elections flow in the opposite direction of the current.

I'm not looking for 2% accuracy. ~10% would be acceptable.

With the shunt on just the house negative, when the BIM connects to chassis battery and charged house, the shunt doesn't take those AH into account. At least that's what I have seen with my Renogy battery monitor.

**16ACE27** · 10-03-2022, 11:18 PM

Quote:

Originally Posted by sportcoupe

I'm not looking for 2% accuracy. ~10% would be acceptable.

With the shunt on just the house negative, when the BIM connects to chassis battery and charged house, the shunt doesn't take those AH into account. At least that's what I have seen with my Renergy battery monitor.

You mean Renogy battery monitor?

Why would the shunt need to take AHs from the chassis battery into account? They're not coming out of the house batteries.

I have the Renogy battery monitor above and it always displays the exact status of my two LiFePO4 house batteries.

Beau388 · 10-03-2022, 11:33 PM

Quote:

Originally Posted by sportcoupe

I'm not looking for 2% accuracy. ~10% would be acceptable.

With the shunt on just the house negative, when the BIM connects to chassis battery and charged house, the shunt doesn't take those AH into account. At least that's what I have seen with my Renergy battery monitor.

It takes two wires to complete the circuit from the source to the load. In a DC system circuit current flows from positive to negative (downhill according to Ben Franklin). You cannot create any new electrons by normal physics, but you can move them along a wire if there is a voltage present and voltage plus current can do work.. So any positive current from the chassis battery or alternator has to be balanced by the current leaving the house batteries. through the negative. The batteries do not store electrons or current, but have the chemical reactions to create a stored voltage (potential) to move current along the wire. When you charge any battery, you are creating a charge (voltage) to move current at a later time. When you discharge a battery, the potential (voltage) to move current is decreased. Old Gaston Plante figured all this out in about 1860.

sportcoupe · 10-03-2022, 11:45 PM

Quote:

Originally Posted by 16ACE27

You mean Renogy battery monitor?

Why would the shunt need to take AHs from the chassis battery into account? They're not coming out of the house batteries.

I have the Renogy battery monitor above and it always displays the exact status of my two LiFePO4 house batteries.

Yes Renogy. Typo.

When BIM connects, the house and chassis batteries are wired in parallel. AH going into the house from chassis battery doesn't pass through the house battery shunt from what I can tell. Either that or I have a bad Renogy monitor.

Beau388 · 10-04-2022, 12:27 AM

Quote:

Originally Posted by sportcoupe

Yes Renogy. Typo.

When BIM connects, the house and chassis batteries are wired in parallel. AH going into the house from chassis battery doesn't pass through the house battery shunt from what I can tell. Either that or I have a bad Renogy monitor.

If the shunt is on a single ground wire from the house battery bank. it is measuring the total current flow in and out of the batteries. It doesn't matter where the current comes from (the number of positive sources). The only problem wold be the if the meter calibration to the shunt is in accurate or a second ground.

Let me describe a shunt. To accurately measure DC current flow the entire current must flow through meter's windings and an analog to digital converter change that into a digital reading. A meter to handle 100 amps (regardless of the voltage) requires a big wire and an expensive meter. A shunt is a calibrated leak around the main wire. I shall pick a number for the leak. If the main wire is carrying 100 amps at 12 volts or 120 volts DC the shunt meter will only see 0.5 amps. The other 99.5 amps goes through the main part of the shunt). This is a 200 to one shunt. Your display interprets this current of 0.5 amps as 100 amps and shows that on the display. If you were to use a 100 to 1 or 300 to one shunt with the same display made for a 200 to one you would have an error. The better displays can handle several different shunt ratios.

**16ACE27** · 10-04-2022, 02:23 AM

Quote:

Originally Posted by sportcoupe

Yes Renogy. Typo.

When BIM connects, the house and chassis batteries are wired in parallel. AH going into the house from chassis battery doesn't pass through the house battery shunt from what I can tell. Either that or I have a bad Renogy monitor.

Into the house what? Battery? AH don't move. It is just an expression of current flow (Amps) for a given period of time (hours). Current can not flow into or out of the house batteries unless it flows through the shunt on the negative side. Current CAN flow to house loads from the alternator/chassis battery without going into the house batteries - the shunt will not and is not designed to measure that.

sportcoupe · 10-04-2022, 07:21 AM

Quote:

Originally Posted by 16ACE27

Into the house what? Battery? AH don't move. It is just an expression of current flow (Amps) for a given period of time (hours). Current can not flow into or out of the house batteries unless it flows through the shunt on the negative side. Current CAN flow to house loads from the alternator/chassis battery without going into the house batteries - the shunt will not and is not designed to measure that.

I stated house battery.

Example: Current Renogy monitor is calibrated for 100ah house battery. When the chassis battery is added in parallel, the AH of the battery pair is now ~150Ah. This is why I believe my monitor is misbehaving or it is defective in some way.

I will call Renogy.

DavidEM · 10-04-2022, 10:14 AM

Let me try to explain it one more time:

When the chassis battery connects to the house battery two things have to happen at least for the Precision Circuits BIM: The chassis battery has to be above 13 volts and the house battery has to be at or below 12.5 volts. One then charges the other just like connecting a solar panel to the house battery.

When the voltages drop which they will do when you put a load on the house battery, the chassis battery is disconnected. It is not available to provide battery amp hours, only charging amps.

So leave your Renogy settings as is. BTW is that a shunt based monitor or just a voltage based one. Looks like Renogy has a new shunt based monitor for $78 on Amazon and it looks like the one in your picture.

David

**16ACE27** · 10-04-2022, 02:46 PM

Quote:

Originally Posted by sportcoupe

I stated house battery.

Example: Current Renogy monitor is calibrated for 100ah house battery. When the chassis battery is added in parallel, the AH of the battery pair is now ~150Ah. This is why I believe my monitor is misbehaving or it is defective in some way.

I will call Renogy.

Well if you have two 100 AH batteries the battery monitor should be set for 200 AH, not 100 AH.

And when the BIM connects the chassis battery is NOT added in parallel as far as the shunt and meter are concerned. To be added in parallel the negative side of the chassis battery would have to be connected to the negative side of the house batteries. It is not - it is connected to the other side of the shunt.

Civrot · 10-09-2022, 06:22 PM

https://battlebornbatteries.com/prod...ooth-built-in/

Sir,
i installed the victron monitor.... it works perfectly doing exactly what u want....
i called battleborn batteries... they are extremely knowledgeable and helpful...
they stayed with me during the entire install.... love it..... give em a call...

Vic
Retired US Army

**16ACE27** · 10-09-2022, 08:57 PM

Quote:

Originally Posted by Civrot

https://battlebornbatteries.com/prod...ooth-built-in/

Sir,
i installed the victron monitor.... it works perfectly doing exactly what u want....
i called battleborn batteries... they are extremely knowledgeable and helpful...
they stayed with me during the entire install.... love it..... give em a call...

Vic
Retired US Army

Assuming your comment is directed to the OP, the Victron works exactly as the Renogy does with a shunt on the negative side.

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