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How long should batteries last


dc92974

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For now I just have everything mounted on a plywood structure under the camper which is skirted. Trying to make sure I have everything I need and understand how it works before I start permanently mounting stuff. I'm terrible at that stuff so don't really want to have to do it twice 🙂

Figuring out where and how everything gets mounted will be a project for next summer.

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Just make sure the shunt for your new battery monitor is mounted correctly to your battery bank.  It needs to be mounted to the negative post of your bank (single battery cable from the post to the shunt) and then all other negative cables need to be mounted to the other side of the shunt.  This way it measures all voltage going in/out of the battery bank.  The Victron is a very good piece of equipment and will give you a lot more information to help you diagnose your battery usage issues.

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  • 3 weeks later...

Reporting back...

I ordered and setup the Victron. While I was waiting I took my batteries  to a place I could plug them in and let them charge for the week (I pulled my rv charger and used that). It took about 1.5 days before the charger dropped to the trickle maintenance mode. So, I'm pretty sure my initial testing didn't start with fully charged batteries.

The voltages are about the same but the Victron is showing that my batteries have stayed in the 90% level all week. We haven't had any sun for solar this week but I did run my generator a few times while I was making dinner in the evening.

I seem to pull about 0-4w most of the time which seems reasonable. It's awesome to be able to turn something on/off and immediately see the impact it has.

I don't see anywhere where the Victron shows the input when I'm charging. On my solar panel I can see I managed about 30ah for the week but I don't see anything on the Victron, am I just missing it? It would be nice to get a better picture of how my charging is affecting the battery charge. There is a summary screen that looks like it should show input but it seems to low.

It would be nice to have the ability to scroll through historic numbers (and to see numbers when I'm not connected). I can live without that though, for now I have a battery voltage monitor that shows history. So that combined with the Victron and Renogy solar controller gives a decent picture of what's going on.

 

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2 hours ago, dc92974 said:

I don't see anywhere where the Victron shows the input when I'm charging. On my solar panel I can see I managed about 30ah for the week but I don't see anything on the Victron, am I just missing it? It would be nice to get a better picture of how my charging is affecting the battery charge. There is a summary screen that looks like it should show input but it seems to low.

The Victron will show the net current going in and out of the batteries.  The Amp Hour total will be negative if you've used more power than you've replaced via charging and will creep back towards zero as the batteries gain a charge.

If there's a 30 Ah discrepency between what the panels are putting out and what the Victron says is reaching the batteries, that's how much current your RV used over that time.

Edited by Lou Schneider
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On ‎10‎/‎22‎/‎2018 at 2:22 PM, dc92974 said:

I looked up some other charts and I see what you mean. The only thing I can come up with is the inclusion of temperature? Most of the charts I saw seemed to be for a set temperature like 80F.

We do have pretty big temp swings right now. 50-60 for the high in the afternoon and 25-35 for the low in the morning. It's a little less of a change under the skirting but it's still probably a 20 degree temp difference when I check before I go to bed and get up in the morning. Could the temperature be what I'm seeing in the voltage differences?

Bingo.  If you fully charge the battery, disconnect charging and allow the battery to set with no draw or charging you should have a voltage of about 12.9 at about 70 degrees.  When the temperature drops you will see a decrease in voltage, again with no charging or no draw.  Then if you actually do draw some AHs from the battery and go to fully recharge you will enter true insanity.  Let us say you pull 20 AH from a 100 AH battery.  It would make sense that you merely recharge by that amount.  NO....  The battery will not be at full capacity. Instead you need to overcharge the battery.  After you have replaced the 20 AH you need to continue charging at 14.3 v until the battery will maintain that voltage with about 1 amp of applied charging.  That can take several hours.  It the process is interrupted, you will virtually need to start over on that several hour process.  At that point you can switch to float charging by maintaining 13.3 volts.  The "overcharging" is not something you need to do everyday especially for a battery which is barely used.  It should be done at least every couple of weeks.  Depending on the battery design you may also improve life if you do an equalization charge cycle every few weeks or months.   You need to check with the manufacturer for the exact specs as there are some differences especially between AGM and non AGM battery types.  Batteries are not efficient when it comes to pulling out AHs and replacing those AHs.

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  • 2 years later...
3 hours ago, noteven said:

This truth is known to DC electric people:

Amp hours is amp hours. Once they are gone, you gotta put 'em back. 

Actually you not only have to put them back but you need to put back about an additional 5-10%.  Those amps flow into the battery bank very slowly.  Once you have theoretically put back the used amp hours plan on another 2-4 hours of charging at 14.3 volts.

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On 11/9/2018 at 11:12 PM, JimK said:

Bingo.

 

31 minutes ago, JimK said:

Actually

Notice the age of the questions being answered? And who gave the last response in 2018? The original poster has not been back since your previous reply.  😆

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5 minutes ago, Kirk W said:

 

Notice the age of the questions being answered? And who gave the last response in 2018? The original poster has not been back since your previous reply.  😆

Often the original poster chooses not to participate in the ongoing conversation. That shouldn't stop others from carrying on a conversation about the general subject matter, or peripheral topics as well. Just my opinion.  Jay 

 

 
 
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On 11/9/2018 at 3:44 PM, dc92974 said:

Reporting back...

I ordered and setup the Victron. While I was waiting I took my batteries  to a place I could plug them in and let them charge for the week (I pulled my rv charger and used that). It took about 1.5 days before the charger dropped to the trickle maintenance mode. So, I'm pretty sure my initial testing didn't start with fully charged batteries.

The voltages are about the same but the Victron is showing that my batteries have stayed in the 90% level all week. We haven't had any sun for solar this week but I did run my generator a few times while I was making dinner in the evening.

I seem to pull about 0-4w most of the time which seems reasonable. It's awesome to be able to turn something on/off and immediately see the impact it has.

I don't see anywhere where the Victron shows the input when I'm charging. On my solar panel I can see I managed about 30ah for the week but I don't see anything on the Victron, am I just missing it? It would be nice to get a better picture of how my charging is affecting the battery charge. There is a summary screen that looks like it should show input but it seems to low.

It would be nice to have the ability to scroll through historic numbers (and to see numbers when I'm not connected). I can live without that though, for now I have a battery voltage monitor that shows history. So that combined with the Victron and Renogy solar controller gives a decent picture of what's going on.

 

We have victron controls and battleborn batteries. We have an app that will show how much charge our batteries absorbed through solar for the day and it has a history as well. I believe it "reads" the solar charge controller. We absorbed 9.64kWh through solar today. almost 6 the last 2 days, 7kwh the day before, etc. I can see the last 30 days. We haven't been using as much power as we did 30 days ago so the batteries didn't get as low. obviously we can't absorb power if the batteries are topped off.

We also have an app for the inverter so we can see how much power is being inverted (to AC). This doesn't account for our DC lights (4W each). Currently drawing 205W. We have 3 fans running and so that means the fridge is probably running as well at this moment. It's a standard residential fridge. And the clock on the stove is on. Oh. And my phone is charging and probably my ear buds.

225Ah at 12v isn't very many watts.  That's only 2700Whtotal. Plus, you likely should only drain your batteries to about 50% which means you have a "usable" 1350Wh before you start damaging the battery. We have battleborn lithium batteries and they come a BMS and can actually be run down to "zero" without damaging them. We have 1000Ah at 12v. Ok. That's a lie. We have it configured into a 24v system so we actually have 500Ah @24v. But it all equals 12,000 Wh. 

We can read everything from the app - state of charge %, power being inverted, and how much solar we are taking in at any moment (plus the history totals for 30 days). 

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