Sanity Check Please - Are my batteries dead?

[bullfrog]

If you are unsure take them to somewhere like Batteries + and drop them off to be tested.

 

[A_restless_development]

Thanks everybody for the replies:

@desertranger - The small red wire is a sensor wire for the battery monitor. The smaller battery cable, I don't know, I hadn't noticed until you pointed it out, but this is how it's been set up from the previous owner and was never changed. I'll be taking readings tonight.

@jonyjoe - Amps with alternator vary between 15 and 40, but lately it's been around the 20 mark while idling/driving. Panels will give me 8 or 10 in good sun. Yesterday I ran the van for hours (doing so again today) to charge things, and got a max voltage of 13.8 from the monitor.

@idsrellance - I'll be trying to do some testing tonight

@jimindenver - See above answer, got a 4 hour drive then I'll let things rest for a while disconnected

@bullfrog - sure seems that way, testing tonight will shed some light

 

[highdesertranger]

4 hours of driving and 13.8v won't cut it. You need to get those batteries charged to 100% ASAP. Jim had a good point you might have 1 bad battery. Highdesertranger

 

[ldsreliance]

Even if those batteries were brand new, it would take 18 hours (in theory and assuming 20% efficiency loss) to charge those 3 batteries from 0% SoC to 100% with the alternator averaging 20 Amps. More than double that for solar.

After we help you figure out the underlying performance problem that still surely exists, you probably need to think about how to get these batteries up to 100% every time you cycle them OR replace them with lithium.

 

[A_restless_development]

Is there any way this could be caused by my battery isolator? From what I understand, hooking the positive terminals of the starter battery and house batteries with an isolator in the middle is a fine way to charge the house batteries. I've been running the van all day (idling and errands) for almost 8 hours now, the voltage as measured by the battery monitor has bounced between 13 and 13.6, but has not gone any higher. Amperage going into the batteries fluctuates between 10 and 40, most of the time still in the 20 range.

I will be replacing these batteries with Lithium soon, thinking this 200AH Ampere Time battery: https://www.amazon.com/gp/product/B088RM4W48/ref=ox_sc_act_title_1?smid=A2EZ26GXN4H62H&psc=1

I read that I'll also need a battery to battery charger as the isolator isn't going to cut it for lithium.

Definitely appreciate all of your input, I just want to be able to put this electrical issue behind me and not think about it anymore.

 

[highdesertranger]

" From what I understand, hooking the positive terminals of the starter battery and house batteries with an isolator in the middle is a fine way to charge the house batteries."

Who ever told you that doesn't know what they are talking about. Just under normal cycling conditions it takes all day driving at highway speed to fully recharge a battery. If your battery was at 10.5v you will not get it fully charged in a day. You must fully charge your battery to 100% everyday.

So lets recap the important points,

It takes all day of driving AT HIGHWAY SPEED to fully recharge a regular battery cycle. that's taken down to 12.2
Idling won't cut it
you need to get to 100% everyday, 95% doesn't cut it
you need to get your batteries charge ASAP. just in the days since you posted this not getting them to 100% has seriously harmed them

Now don't get me wrong you should have your battery connected to your charging system as a supplemental charge source but don't rely on it as your primary source.

You need enough solar to get your batteries to 100% everyday. If it doesn't then either you have,

not enough solar
you are using to much power
you have a problem

So to recap,

you need to get those batteries to 100% ASAP not tomorrow.
you need to stop drawing power from them until they are 100%
Jim brought up you might have a bad battery. That makes sense. If you do you need to get it out of the system ASAP.

Highdesertranger

 

[ldsreliance]

Is there any way this could be caused by my battery isolator? From what I understand, hooking the positive terminals of the starter battery and house batteries with an isolator in the middle is a fine way to charge the house batteries. I've been running the van all day (idling and errands) for almost 8 hours now, the voltage as measured by the battery monitor has bounced between 13 and 13.6, but has not gone any higher. Amperage going into the batteries fluctuates between 10 and 40, most of the time still in the 20 range.

I will be replacing these batteries with Lithium soon, thinking this 200AH Ampere Time battery: https://www.amazon.com/gp/product/B088RM4W48/ref=ox_sc_act_title_1?smid=A2EZ26GXN4H62H&psc=1

I read that I'll also need a battery to battery charger as the isolator isn't going to cut it for lithium.

Definitely appreciate all of your input, I just want to be able to put this electrical issue behind me and not think about it anymore.

Hit me up when you decide you want to buy some lithium batteries.  Even if you don't purchase any from me, I would still like to help you out.  The short answer is that Ampere time battery is not a good battery but I don't have time to write a 10 page post on here explaining why right now.

 

[bullfrog]

Unfortunately there are very few electrical systems you can build and forget that involve AGM batteries as they should be at least monitored once a day to insure they reach a fully charged state. I have achieved really good battery life by never allowing my AGM batteries to go below 75%. I have done that with solar and a generator. I check my battery monitor each day just before 5 PM to see if the solar has gotten the job done, if not I start the generator and charge with it for the few hours necessary before going to bed. In the morning on cloudy days especially I bulk charge a couple hours with the generator then see if the solar I get the next day has been enough to top them off. Lithium batteries still require a source of power to charge them and require a a DC to DC charger rather than an isolator because of lithium batteries higher voltage requirements even if you have a Battery Management System(BMS) with a temperature sensor as they are more sensitive to temperature extremes somewhat. Their saving grace is the BMS, if it is working properly, will balance them and shut off the battery power before you drain them or over charge them to a point they are damaged. The BMS if it has all the necessary sensors and functions properly can save your batteries by preventing you from depleting them too much and letting them get way out of balance which is most likely what has happened to your AGM batteries. The BMS will let you know when you have used too much power by shutting everything off, is that really what you want? If you are confident your solar and driving provide enough power a lithium system will be the expensive less bothersome way to go.

 

[jonyjoe303]

I think your batteries are probably still good, they just need a good charge. When my agm battery went bad it was charging all the way to 14.4 volts but as soon as I put a load on it, it didnt last long. (it was a 102ah agm but the capacity was reduce to about 30ah)
Your battery only charging to 13.6 volts means its still taking a charge but its so depleted its going to take a long time to get full. And if you are still using the battery after charging all day, it will take even longer.

 

[XERTYX]

If the OP is still trying to figure this out I have a couple of points.

A: One thing that really stood out to me was you mentioned running a 7 amp load (fan) that was 12 volts yes? And not from the inverter 120v AC?

B: I have a sneaking suspicion as mentioned that you have 1 bad battery. I'll explain why.

As the electrician pointed out to you the batteries WERE installed improperly. I did this very thing with a system I built years ago from AGM batteries that come in home alarm systems.

It was wired like this.
Batt A. B. C.
_____(+)_______(+)________(+)
DC IN/OUT
_____(-)________(-)_________(-)

Batt A supplies nearly all of the power and then relies on B and C to charge it back up.

Eventually Batt A will become seriously damaged and lose capacity. The electrician moved the positive lead to battery C as it should be.

Now the system is trying to push the charge thru all 3 batteries but battery A has a boo boo and it's not charging all the way.

I had the same problem. What I did was to fully charge the system and separate all the batteries. I didnt have the patience to wait a few hours and check their voltages which is what you should do.

What I did was to run a load off of an AC inverter that I regularly used with the batteries so I had an idea of how long it SHOULD have ran on each battery individually. Wouldn't you know it? Battery A lasted only a few minutes. The others lasted the amount of time they should have.

I had already discovered my wiring mistake after using the bank for quite a while and cycling down to about 11 volts every night. After fixing my mistake I was having the problem you are now. My AC inverter would run for a few minutes and boom. Low volt disconnect. Just the same as it did when running only on Battery A alone. The others were just fine. They lasted as long as they should have... more or less.

So as advised above I would charge it up and then disconnect all 3 batteries. Wait a while. Measure each batteries voltage. I think what you find will surprise you. One will probably be around 10v and the others around 11-12 or so.

It would be best to leave them disconnected for 24 hours if possible before measuring the voltage.

And C: As stated. Charge those batteries. Like yesterday. Or even sooner than that.

 

[A_restless_development]

Hey all! Just wanted to say that I ran into some snags recently and haven't been able to test anything yet, but I have been charging the batteries as fast as possible and they now register 14.2ish volts under charging and measure 12.4 or so in the morning.

That being said, I've 100% stopped using the instant pot or anything else that draws from the inverter, so I'm using maybe 20% of the electricity that I normally would.

I'll definitely be disconnecting all 3 and measuring voltage/running load tests individually. If what you're saying is right and I have one bad battery, it sounds like if I simply take that out of the equation the other two batteries will perform much better, yes?

Thanks again for all of the suggestions!

 

[highdesertranger]

yes the two good batteries might work or you might have damaged them and/or shorten their life considerably. You're leaving them not fully charged for so long had to have some effect. Highdesertranger

 

[XERTYX]

If in fact it is one bad battery and those are true AGM batteries in my opinion what HDR said is absolutely true. The other 2 are falling fast.

If they're marked as AGM (Absorbed Glass Mat) but are really SLA (Sealed Lead Acid) the other 2 may still have a longish life ahead of them.

SLA is my favorite lead acid battery chemistry. Its very forgiving in my experience. Also SLAs may can be repaired so to speak.

True AGMs as I understand it will start to develop dry patches on the fiberglass mat inside the battery which is not recoverable.

Either way not isolating and testing them IS doing harm. Every day even more so.

Judging solely on the voltage to determine state of charge (not the best practice BTW) 12.4 volts in the morning is somewhere around 75% charge on the batteries.

If those are 100ah batteries then in the morning it seems like you've used about 75 amp hours overnight. Roughly around one kilowatt. That's suspect if you're not using much power any longer. Either there is a problem (bad battery) or they still are not being fully charged IMO.

100ah X 3 = 300ah. 300ah X 0.25 = 75ah

 

[A_restless_development]

Update: I was able to separate and test batteries over lunch, two measure 12.7 one measures 12.1. Will let them rest for a bit and check again later to make sure

 

[ldsreliance]

That makes sense. If they stay at 12.6 or 12.7 for another hour I think the other two batteries are fine and you can just pull out the dead one.

 

[A_restless_development]

Further update, letting them sit disconnected, measured 12.5 on two batteries and 11.8 on one. I'm thinking hook the system back up with the two better batteries and leave the oddball out.

 

[XERTYX]

Further update, letting them sit disconnected, measured 12.5 on two batteries and 11.8 on one. I'm thinking hook the system back up with the two better batteries and leave the oddball out.

Yup. DEFFO. As soon as possible shore up that battery cable umbilical cord. In the mean time at least LOCK OUT THE MIDDLE battery terminal. Electrical tape or better. Preferably better. Preferably terminal work.

But make triple sure that the positive and negative terminal that remain unused are both very well insulated. Electric rated tape. The metal of either shouldn't be able to come into contact with the other OR ANY other conductive surface.

Then Recharge. Keep usage low. Let it sit as undisturbed as possible overnight the first time you think its regained full charge. Just sorta let it soak in for a night after a deep discharge like that.

Going forward. Keep it charged up to where it sits 12.7 or 12.8 or better every morning at rest and even damaged AGM marked SLA batteries can come back from the dead damn near it.

YMMV. However.... I have killed the HELL outta SLAs before. Many times. And yet. That's why it's my fav chemistry. 

The dead one BTW could possibly be saved as well. But see if this fixes it.

 

[A_restless_development]

Great news everybody (Professor Farnsworth voice)!

After reconnecting the two good batteries and driving four hours, I was reaching 14.3v while charging and ended with 12.75v in the morning after running my ceiling fan and fridge all night.

Not counting my chickens by any means, but I believe we're on the right track.

Can't thank you all enough for your insight and suggestions!

 

[highdesertranger]

I believe the credit should go to Jim for being captain obvious and pointing out that you probably had one bad battery. Thanks Jim. Highdesertranger

 

[XERTYX]

AWESOME! I would also reccomended if at all possible if you have a friend with a battery charger, especially one that has a repair cycle to asap hook the "bad" battery up to it and leave it for as long as necessary. Then later leave it OFF the charger for 24hrs then measure it. I'd venture to say it possibly will be around 12.6 after serious charging and sitting for 24 hrs.

It might be possible to reconnect it if so, otherwise it might make a good backup battery for lights etc.

If not if it is an SLA someone with the skills might could pop off the case and check each of the 6 cells inside. One of them might need to be topped up with distilled water then charged again. Or it could be fried. SLAs are very forgiving in my experience.