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testing house batteries accurately ?


Sir Traveller
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Hello Everyone…

 

I have a 2003 Ford F-53 RV

 

What’s the most accurate way to test house batteries using multimeter and hydrometer? Disconnect from shore power then keep few lights on inside the RV to give a bit of load?  Do I have to disconnect the 2 batteries from each other and test each one separately? or no need to disconnect anything ?

I appreciate any suggestions…

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Just now, Sir Traveller said:

What’s the most accurate way to test house batteries using multimeter and hydrometer?

Sir, great question, here's my take:   Wellllllllll if you are using ONLY a voltmeter and hydrometer you can arrive at a good indication of the batteries state of charge including each and every individual cell (hydrometer) which is great and useful  information.

 HOWEVER once that's determined it would take a "Load Test" (can buy a load tester not too expensive)  to determine the battery energy storage and delivery capacity, and that in addition to the SOC, is what's really important if you need to use stored battery energy for dry camping IE a battery can show full charged in each cell but lack energy storage and delivery capacity to pump out much current for very long WHAT AN RV NEEDS WHEN DRY CAMPED   stored energy and the ability to pump it (X amps for X time) into a load. 

NOTE Instantaneous Power in Watts a battery can deliver is Volts X Amps while Energy is Volt x Amps x Time and often measured and stated in Amp Hours..as the case for RV and Golf Cart use, the more AH the more energy storage capacity.

 For an accurate measure of a batteries SOC as related to its voltage, the reading must be taken AT REST AND STABILIZED with no loads and no charging for at least 20 to 30 minutes

Temperature: 77 degrees Fahrenheit

 Percent  Hydrometer  Unloaded
  charge     reading   voltage
     100       1.265     12.63
      75        1.210     12.30
      50        1.160     12.00
      25        1.120     11.76
       0         1.100     11.64

Theres more that could be said and hopefully the other fine gents can add to this, but enough for now lol

 

Best wishes

John T

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19 minutes ago, Sir Traveller said:

Do I have to disconnect the 2 batteries from each other and test each one separately? or no need to disconnect anything ?

YES I would disconnect each from the other just to be safe and (see above) have them at rest and stabilized with no loads or no charging for at least 20 to 30 minutes

 

John T 

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What is the reason you are wanting to check your batteries?

Are you having a problem and are trying to find out if your batteries are good, or do you just want to check to see if the batteries are charged?

Are you planning on doing some dry camping or boondocking and want to know if your batteries are in good enough shape to dry camp with?

Any other reason?

The hydrometer is the best tool to check the state of charge (SOC).  Be sure to compensate for the temperature.  Details should have come with the hydrometer. 

However if you want to know the SOC of your batteries while dry camping you really need a battery monitor like a Trimetric or Victron 712.

 

Edited by Al F
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  • 2 weeks later...

So I disconnected the shore power and turned off the house battery switch, I tested the batteries,  and the measurements were as follows: the voltage ( using a millimeter was 12.83 , and when I used the hydrometer, the first battery tested 1.3 and the second battery 12.65 , are these too high? Is it possible to be because of overcharging?

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What is the reason you are checking your batteries?  I asked that question earlier.  The replies you have received just tell you what to check to see if you batteries are fully charged.  Not how to check for problems.

For the battery that was at 12.83V, the surface charge from charging had not bled off yet.  Let it rest another hour or so and check again.

For the battery at 12.65.  Is that a typo for the hydrometer reading and should be 1.265?  If it is voltage then that is showing a fully charged battery.  If it is hydrometer reading then, just as the first battery, the surface charge has not bled off yet.  

As far as the hydrometer reading, what are the readings for every cell?  If you have two 12V batteries you will have 12 cells to check.  If you have a pair of 6V batteries you will have 6 cells to check.

With the hydrometer readings what you are looking for is a significant difference in one or more of the cells.  Such as if the the cells you check are reading 1.265 and you find one or more lower such as 1.120 (25% SOC) or even at 1.210 (75% SOC) then you have a weak cell then that is a bad battery.  

So far is seems like you have batteries that are charged.  

You need to recheck the batteries after a few days and see if they are holding a charge.  If they are holding a charge then reconnect them to the RV and turn all the lights on in the RV and after 30 minutes to an hour check the battery voltages (while the lights are on) again to see if they have dropped way down. Be sure that nothing else is pulling power from the batteries, such as an inverter powering something. 

To estimate the load on your batteries, each incandescent bulb pulls about 1.5 amp, florescent light fixtures pull around 3-4amps depending on the size of the light fixture. You want a load of around 10amps or so. 

 

 

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Sir, I doubt the batteries were overcharged but not being there or unsure of your equipment I cant say from here . I can say a full charged lead acid battery AT REST AND STABILIZED at 77 degrees would be 12.63 volts, I suspect you may not have allowed enough rest time (no loads no charging) prior to taking your reading. The Hydrometer readings need to be taken IN EACH AND EVERY INDIVIDUAL CELL and look for perhaps a single bad cell with a far different reading and/or ONE of the cells having a different off color or gray or milky appearance indicative of a BAD CELL. 

 

 As I noted above iffffffffffffff all the cells test good (needs to be) and ifffffffffff the battery reads 12.63 at rest and stabilized (needs to  be) it may still lack energy storage capacity due to age or sulfation THATS WHY YOU ALSO NEED A LOAD TEST to better understand the condition of your batteries. I bought a 6/12 Schumaker (spelling ?) Load Tester at Advance Auto around $50. Soooooooo Hydrometer in EACH cell,,,,,,,,,Voltmeter,,,,,,,,,Load Tester is whats needed. Many shops do that for free. Check EACH cell with a Hydrometer and insure proper levels and no off colors  Let is set longer and try again with no loads and no charging, disconnect a lead to insure

 

 John T  

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47 minutes ago, Al F said:

What is the reason you are checking your batteries?  I asked that question earlier.  The replies you have received just tell you what to check to see if you batteries are fully charged.  Not how to check for problems.

I am wondering pretty much the same things. We are really trying to help but arean't sure what to answer. As an additional bit of information, the charts that show proper hydrometer readings/voltages are temperature sensitive and so if you are not sure this link shows a series of charts that are adjusted for the stated ambient temperatures. The hydrometer readings are based on an average of all cells in the battery and as Al points out, some variation is normal but not a great deal. 

Are you having some sort of battery problems, or just trying to evaluate the condition of your batteries? If you have problems, share a little more information about then and we may be of more help. 

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Sir, I may have mentioned this before, but its possible for your battery to pass each and every cells Hydrometer test,,,,,,,To pass the full charged voltage level test,,,,,BUT STILL MISERABLY FAIL A LOAD TEST and/or be lacking in energy storage capacity due to age or abuse or sulfation on the plates. Its energy storage capacity in Amp Hours you're looking for in an RV battery application. If the batteries are getting old especially if they are NOT full true Deep Cycles or haven't  been well maintained or abused like over charged or undercharged (possible with an older non smart non staged charger) or too often discharged over 50% or fluid levels are too low etc, even if the Voltage is up to par they may need replaced......

 You can do this, best wishes

John T

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8 hours ago, Al F said:

What is the reason you are checking your batteries?  I asked that question earlier.  The replies you have received just tell you what to check to see if you batteries are fully charged.  Not how to check for problems.

 

 

 

there are few reasons, first I saw leak from the caps so I wanted to know if the batteries were going bad or just boiling from being overcharged ( my RV has built-in charger , I do not know if it is smart charger, it is a 2003 F-53 Ford , Four winds hurricane ) I also leave the RV in storage for 6 months a year usually May through November, then hook it up to shore power from November to May, many people notified me that this kind of use does affect the life of the batteries , that is why I wanted to check

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I appreciate all the replies, it really help... I will try to give as much information as possible, I am not savvy when it comes to electrical systems and batteries, overall I am still new when it comes to RVs... I did not maintain the batteries well in the first 2 years for the lack of my knowledge about what I needed to do, thus IU am trying to catch up now ... again many thanks to everyone 

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1 hour ago, Sir Traveller said:

I am not savvy when it comes to electrical systems and batteries,

You do need to check the electrolyte levels in your batteries on a regular basis when connected to shore power as normal charging and discharging does cause some loss of water and it must be replaced with distilled water as needed. I suggest that you may want to watch this battery maintenance video from Trojan battery company.

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Sir, thanks for the update that helps.

1) If your flooded lead acid batteries are often boiling over electrolyte, there's a chance (in addition to a bad battery) you have an older cheaper more like constant voltage Converter/Charger and left unattended for extended periods they have been known to overcharge and damage batteries.  A modern so called "Smart Charger" is better and it wont overcharge plus do a better job using 3 or 4 stage charging parameters 

2) You need to check the levels on a regular basis and if they are often low or often overflowing the battery is likely BAD   and/or  your Converter/Charger is at fault.

3) Long term storage ESPECIALLY IF ITS FREEZING is hard on lead acid batteries due to the normal chemical self discharge. Most use a small Battery Tender keep connected to the batteries for long term storage IFFFFFFFF  120 VAC power is available. If not some take them out and place in a heated garage etc  and charge them now and then or leave a Trickle charger battery maintainer on them AT LEAST unhook the batteries for long term storage is better then nothing and can prevent phantom loads or discharges.

4) Many battery shops like Interstate or Batteries Plus etc or even auto supply stores will test and load test a battery for free  ID SUGEST THAT BE DONE. If they are bad I strongly suggest you replace them with full true Deep Cycles NOT hybrid dual purpose cheaper RV/Marine batteries. If you go AGM you dont have to worry with checking and adding water

5) Id also strongly suggest if needed you replace your Converter/Charger with a modern Smart 3/4 Stage suited to your chosen battery chemistry (Wet flooded lead acid or AGM or Lithium etc) battery type  

Hope this helps

John T

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20 hours ago, Sir Traveller said:

I appreciate all the replies, it really help... I will try to give as much information as possible, I am not savvy when it comes to electrical systems and batteries, overall I am still new when it comes to RVs... I did not maintain the batteries well in the first 2 years for the lack of my knowledge about what I needed to do, thus IU am trying to catch up now ... again many thanks to everyone 

Here is a link to lots of info about the batteries we use in an RV and should answer a lot of your questions.  At the bottom of the webpage, be sure to click on the "continue to part 2" for more info about RV batteries, solar, etc. 

http://www.marxrv.com/12volt/12volt.htm

Leaving the batteries sitting w/o a trickle charge allows them to self discharge.  In 6 months time they probably have discharged enough and sat long enough to "sulfate" and loose capacity.  Sulfating  happens when batteries are not kept at 100% charge and then left at a charge level of less than about 80-85% repeatedly for more than about 5-7 days, or just continuously for weeks or months. 

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  • 3 weeks later...

Tell us what make and model your 2003 charger is; most likely you will be purchasing a smart charger.  New smart chargers can be left on 24x7 and will not over charge the batteries most are capable of lead acid, AGM and Lithium types.  If you upgrade to AGM budget for a new charger if you do not your old charger will kill the AGM in a few years.

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