32 replies to this topic

[DanoT]

My 2011 Phoenix camper came with a solenoid that connected starting and camper batteries when the engine is running, separates the batteries when engine is off.

 

On a recent trip the camper batteries got zero charge so I had my mechanic install a new solenoid. An up coming trip to Banff in April will determine if a failed solenoid was the problem.

[Vic Harder]

There is no problem using a VSR.   I would probably go with a bluesea SI-ACR for a few bucks more, as they are known reliable option:

https://www.amazon.c...keywords=si-acr

 

There is not really any 'priority' given.  The relay puts both batteries in parallel when either battery is charging, and isolates them when the charging stops. 

 

As usual, we have done an excellent job obfuscating the solution to a simple problem. 

 

Yes, I think in our efforts to "do it right" we forget that "good enough" is good enough.  

[ckent323]

DanoT,

 

Solenoids (battery isolators) are fine.  They do consume power and generate heat.  

 

"The primary difference between battery isolators and battery separators lies in the flow of current. An isolator works with a diode system that allows one-directional flow, whereas the separator has a solenoid function that can choose to pull power from either source."

 

http://info.waytekwi...-the-difference

 

Further, a solenoid does not provide for multi-stage charging.  All vehicle type 12 V batteries (FLA, SLA, AGM, Gel) require multi-stage charging to give the longest service life.

 

In the best case the standard FLA (capped battery) will likely hold up better than the others because it can accept a higher voltage in the absorption and float stages.  However, it is probable that other battery types will reach end of usable life prematurely.  The result of the over charging is not a particularly fast process and depending on how often and how far you drive while the solenoid is charging the batteries the batteries may or may not least several or even 4 or 5 years.  

 

Based on manufacturer specs and calculations I have done, a camper deep cycle house battery bank, when kept properly charged and under normal usage, and not being routinely discharged below 50% - 60% SOC, should last on the order of 10 years or more.

Edited by ckent323, 20 March 2018 - 06:32 PM.

[ckent323]

Philos 65,

 

The issue here is having a starting battery of one chemistry (say FLA)  and a house battery (or battery bank) of a different chemistry (say AGM).

 

As rando commented VSRs (and ACRs) work fine - as long as the batteries have the same chemistry.  I have checked with Blue Sea, Cetek, Xantrex and looked at specs from other manufacturers of VSRs and ACRs.  All of them advise against using the devices with systems having batteries of different types (chemistry).

 

What I have come to understand is that for maximum usable life ALL lead acid and LiFePO4 batteries must be charged in a multi-stage charge profile that is dictated by the battery chemistry.  That is, they all have a little bit different charging profile needs.

 

So how much life are we talking about reducing? 

 

Well that depends on the battery use and how much overcharging the battery receives over time so in practice it is highly variable. 

 

FLA batteries are not as sensitive to overcharging as the other types (chemistry) batteries.  Further, they are cheaper.  So maybe one is not really bothered too much if a $100 or $150 FLA battery only lasts 3 or 4 years instead of 5 or 6 years (or more).  That has been the case in all vehicles which only use a voltage regulator for decades.

 

But for someone who has a set of high quality AGM, Gel or LiFePO4 house batteries (or even an expensive vehicle starting battery) that might cost $300 - $600 or more, perhaps getting 8 or 10 years out of the batteries instead of half that time matters.

 

The truck AGM battery I had and which died prematurely after only 4 years cost nearly $300 - because it was being charged by a simple voltage regulator system in my truck not by a smart charger.

 

My house batteries cost me $600 and I want them to last as long as I can make them last which is why I did all this research.  

 

For all the reasons above - I recommend instrumenting expensive batteries (vehicle and or house bank) with a decent battery monitor to allow determination of state of charge and charge stage so that you will know if your batteries are being charged correctly as well as for diagnosing other issues like how much power different devices use so you can minimize the draw down of the house battery bank, etc 

 

I hope that helps explain things a bit better.

 

Craig

Edited by ckent323, 20 March 2018 - 06:58 PM.

[rando]

Craig, 

 

Have you actually measured your alternator output voltage?   I know on most of the cars I have owned (mostly Toyota/Lexus), the alternator provides 14.1 - 14.3V on startup, then drops down to 13.6 - 13.9 in fairly short order, and goes even lower on modern ECU controlled alternators.   

 

This is below the recommended max absorption voltage for almost all AGM and Flooded batteries, and is most likely to do them harm by undercharging (particularly with long wire runs), not by overcharging.  This where solar or you converter comes in, providing the final absorption charge and then switching to float at what ever you set it at.  

 

I know you are trying to help, but I think you are creating an issue where there isn't one.  Folks have been using AGM batteries in automotive applications for decades with no special electronics, and good success.  All the 'premium' car batteries (Odyssey, Die Hard Platinum, Optima) are AGMs, and I have had these last 7-10 years, even when mixed with flooded batteries in a dual battery set ups. 

 

If your alternator is putting out more than 14.5V or so, the best bet would be to adjust your regulator down to a max of 14.4V.   Then allow your solar to provide the final absorption and float charge. 

[ckent323]

rando,

 

I have not measured the voltage from my 1993 Dodge W250 diesel truck during operation.  I am instrumenting my truck battery now with an inexpensive wired to the cab battery monitor so I will know for sure going forward.

 

I drove my truck about 300 miles a week until June 2016 and since then I probably only driven it on the order of 50 miles a week except for a couple of long, over 1000 mile, trips a couple of times a year.  Perhaps all the sitting around for weeks at a time coupled with short distance trips locally between the occasional long trips resulted in sufficient undercharging to prematurely kill my AGM battery rather than chronic overcharging during the 2 prior years when I was driving it a lot more frequently.  Unfortunately, I have no data to allow sorting that out. That battery cost about $300 and only lasted a bit over 4 years.

 

According to the battery university site - it is true that AGM batteries are more susceptible to premature failure from chronic undercharging than FLA or Gel batteries and that they are also susceptible to premature failure from overcharging.  Indeed, you may be correct that undercharging is a more common problem, I just don't know.

 

I went by the manufacturer specs and developed my perspective after talking and emailing various reps (who may be trying to sell a product) as well as having read a number of industry articles, boat forums and off road enthusiast blogs on the subject.

 

I read a number of reports of AGMs (and a few Gel) batteries failing after only a few years (2-3) which seemed to be related, based on the information given, to not charging using multi-stage chargers and the failures resulting from both chronic overcharging and chronic failure to fully recharge (resulting in sulfation).

 

The battery reps and info I found from other manufacturers said that AGMs are sensitive to overcharging and that is a common cause of premature failure.  Frankly, I have no actual data or statistics to support that, only the information given to me by folks in the industry (which admittedly could be flawed).

 

Based on my research it is not clear to me that I have mis-understood this, particularly after several different manufacturer reps told me not use their products with systems having multiple battery types or I will damage the batteries,  but I am no expert and I sure hope I am not making a "mountain out of a molehill" 

 

I appreciate your comment and critical assessment. I will redouble my investigation as a consequence as I would like to find actual data.

 

Regards,

 

Craig

Edited by ckent323, 20 March 2018 - 08:08 PM.

[rando]

I don't think you are incorrect on any of this,  I just wonder if it is actually as significant as you think.   From your battery failure experience, it sounds FAR more likely that the problem was due to the last 2 years of undercharging as opposed to possible overcharging 2 years prior.    Without knowing your alternator output voltage from your alternator, there is no real evidence that the battery has even been overcharged. 

 

I appreciate your internet research, but caution you about putting too much stock in the battery and charger salesman's recommendations.   Of course they will reccomend that you use a programmable charger with settings specifically set to their specified voltages and of course battery charger companies will tell you only to use their highly programmable and expensive battery charger.  That is the optimum situation, but they have nothing to loose by recommending this.  I am also sure you can find anecdotal evidence on any numbers of causes for battery failure on the internet - this is the main problem with the internet, you can find 'evidence' to support any opinion you want. 

 

However, real world experience would indicate this is not a significant problem.   People buy expensive premium AGM batteries to use in their vehicles precisely because they last a long time, and in general they do last a long time without any modifications to the vehicles charging system.    I have had two Odyssey AGM batteries (one as a starting battery, one as a camper battery, but in different vehicles) last at least 8 years each (I sold both vehicles with 8 year old batteries, they may still be fine).    These were both charged with the vehicle factory charging system (presumably configured for FLA batteries) and received no special treatment.  

 

The problem here is that you are causing a lot of folks who may not be battery aficionados to think that they are doing something horribly wrong to their camper batteries using the stock relay/ACR, when there is no real evidence that there is actually a significant problem.  I would strongly suggest you take some measurements on your own system to see whether there is an actual problem before taking this any further.   I know that with my system (and likely anyone else using a modern vehicle) this issue would be way down the list of causes of premature battery failure.

[Vic Harder]

Some data...

 

So I noticed yesterday that I drove long enough (30 minutes) to get the starting battery warm and theoretically charged up by the alternator.  Likewise, the house batteries were at 100%.  I parked in the sun, turned off the engine and punched the remote on my ML-ACR to connect the two sytems.  The solar panel immediately started pushing current (2.6A) into the truck battery.  

 

Both are AGM.  So, I assume the Victron thought that the truck battery was still not fully charged.  Therefore, the alternator is NOT overcharging the truck battery. 

[ckent323]

rando/Vic,

 

I have been searching, downloading and reading numerous industry as well as numerous scholarly articles on vehicle lead acid batteries trying to find data on failure rates and causes.

 

With one exception all of the information appears to be analytical model based.  Because manufacturers and the battery industry give information on expected battery life that is shorter than the analytic models predict I suspect that there are proprietary data out there that is not readily accessible. I hoped to run across some of that data in the academic papers but I did not.  

 

The one exception I found is a JD Powers report summarized as follows:

 

• New to the top 10 list of problems reported in 2017 is battery failure. In fact, 44% more owners report a battery failure this year than in 2016. Batteries are the most frequently replaced component not related to normal wear and tear in 3-year-old vehicles at 6.1%—up 1.3 percentage points from 2016.

http://www.jdpower.c...ndability-study

 

This is attributed to chronic undercharging due to the newer "smart" vehicle electronics.

 

Here is a link to an article based on the JD Powers study:

 

https://www.forbes.c...s/#5eefb723323c

 

Indeed, shorter life due to chronic under charging is exactly what rando has asserted and is consistent with data from Vic on his vehicle.

 

The disappointing part is that I searched for "real world" lead acid battery failure information using multiple search terms which variously included "vehicle", "car", "fleet", and "service use".   I found lots of links to industry data and academic research on failure modes, failure analysis and failure prediction but no data on real world failure rates in vhehicles or campers/RVs besides the JD Power study.

 

I did find one "real world" academic study on valve regulated lead acid (VRLA aka sealed or SLA) battery performance in stationary utility applications.  I am not sure it is very helpful except to underscore the susceptibility of VLRA batteries to under or over charging.

 

http://www.sandia.go...D2001-1110j.pdf

 

The Sandia study does conclude, among other things, that "Inadequate float-voltage setting may be an important life-limiting factor for VRLA cells in float duty".  For real world use in vehicles and campers I think that can be reasonably interpreted to be improper or perhaps inadequate float stage charging.

 

It may be possible to use google trends to analyze search terms and related information but that is a large task.  I did try a search on google trends analyses for batteries but I did not get any definitive hits.  There are a lot of google trends data pertaining to batteries out there however.  I think it is a big research and analysis project to try to use that data.

 

All we are left with is model based predictions coupled with manufacturer and industry information and claims along with anecdotal data.  We each have our own experiences and there are lots of on-line comments by others, but collecting all that information and doing a statistical analysis is beyond my time and interest.

 

So I will summarize, with all due respect, that some folks get long life from their batteries and some folks do not. The reasons why some do and some don't are not clear and after searching I have found no data to better understand that except anecdotal accounts posted on the web - most of which have poor actual data content and as a result have low signal to noise relative to understanding why their batteries failed. 

 

All the analytical studies show that valve regulated lead acid batteries (SLA, AGM and Gel) are just as susceptible to pre-mature failure from chronic overcharging as they are from chronic under charging.  The only vehicle related study I found (JD Powers) suggests that undercharging may be more common than overcharging.  However, based on the JD powers and Sandia studies incorrect charging is a reasonable generalized characterization of these failures.

 

It is interesting that the range of expected life for a starting battery given in the industry and manufacturer sites ranges from a low of 3 - 4 years to a high of 6 - 7 years with the most common lifetime expectation given as 4-5 years.  This is several years shorter than the lifetime that the analytical battery models would suggest so it is clear that real world use is not well modeled and is highly variable.

 

Similarly, the industry numbers for deep cycle VLRA battery life ranges from 7 - 10 years with analytical studies showing years longer.

 

All of these lifetime estimates are tied to specific use scenarios relative to depth of discharge, frequency of DOD and temperature as well as charging through the various stages.  Clearly there are many factors which can diminish usable battery life.  However, my assessment from my reading is that the most common primary reason VLRA batteries fail pre-maturely is related to undercharging and perhaps close behind, overcharging.

 

So I return to the thought that instrumenting batteries to understand the state of charge and charging stage is important if one wants to be able to maximize battery life.  Coupled with that is having battery charging equipment installed that provides the proper charging through the charging stages.

 

In the end the pre-mature failure consequence of not properly charging a VLRA battery will probably not be realized for several years and it may be difficult to ascertain the cause of pre-mature failure post-facto unless one has been monitoring the battery condition regularly along the way. Further, it is not al all clear how much life is lost with a pre-mature failure in a given application.  I could be several years and it could be much less than that.

 

For those of us who have expensive batteries whose life we want to maximize I think it prudent to instrument the battery(s) with a battery monitor and to make sure that the batteries are charged appropriate with the specific battery manufacturer recommendations.  This will not guarantee longer battery life because there are other battery life limiting factors such as temperature as well as deep discharging and frequency of deep discharging that varies significantly from installation to installation, but it seems to me it is the best we can do and it is reasonable to do.

 

All reading this please understand that I am NOT trying to ring any alarm bells and I am not claiming that simple battery charging installations are a problem.  Indeed, many people use solenoids to control multi-battery installations and many of them seem to be happy with these devices.  However, there is no way to know if they are getting the maximum life out of their batteries or not.

 

So all I am saying that if one wants to take measures to maximize battery life there are things that can be done (as I have documented in this topic). Whether or not those measures are worth the trouble will only be known when the battery fails (hopefully many years later) and it is possible that spending the time and money installing this equipment will not yield much additional battery life but unfortunately there is no way to know ahead of time.  In that regard I guess it is somewhat akin to buying insurance vs being self insured. Whether one goes to the cost and trouble of installing this equipment to maximize battery life is a personal decision.

 

I hope all of this is clear, understandable, and informative.

 

My path forward because of the cost of the batteries in my truck and camper is to:

1. instrument the the truck and camper batteries so I can monitor the charge stage and the charge state (SOC/DOD)
2. use an ACR and the manunal switch to control the bulk charge to my house battery bank from my truck when driving and allow manual connection to charge or jump start the truck battery from the camper battery bank
3. rely on my solar system to properly finish charge and maintain my camper battery bank in the appropriate absorption and float stages
4. use a wall powered battery maintainer when the solar system is not working (i.e. whenever the camper is stored or placed for a prolonged in a way that blocks the solar panels from the sun)

If there were a device that would allow charging my multi-chemistry battery system with automatic stage charging as well as provide a way to jump start my truck battery from the camper batteries then I would seriously consider buying and installing it, but as far as I have been able to determine such a device does not (yet) exist for consumer use.

 

 

Quick Glossary:

 

Flooded Lead Acid  - FLA (aka capped, vented ==> the traditional car battery)

Valve Regulated Lead Acid - VRLA  (also known as sealed lead acid)

Sealed Lead Acid - SLA 

Absorbent Glass Matt - AGM

Gel

 

Ref:

http://batteryuniver...based_batteries

http://batteryuniver...t_glass_mat_agm

http://batteryuniver...ad_acid_battery

 

 

Regards,

 

Craig

 

P.S.  Reminder that all of this was stimulated because I had an expensive valve regulated lead acid (sealed) AGM battery in my truck which failed at just over 4 years and which I decided to replace with a much cheaper OEM Flooded lead acid (FLA) battery.  That created a complication in that I now have an FLA battery in my truck and my camper house batteries are expensive VLRA AGM as batteries which have different manufacturing charging requirements than my truck FLA battery.

Edited by ckent323, 22 March 2018 - 12:26 AM.

[pvstoy]

Craig thanks for summing all your research efforts in a well thought out post.   One thing you can do is obtain a proper wall charger for you truck battery when you need to maintain the flooded battery. between usages.