Deep Zombie Batteries?

[brahmon]

sorry for the dumb noob questions but here's another.   i have 15 everstart marine maxx batteries and have been running 10000 btus for 6 hrs a day.   2000w solar.  

This morning I went deep under the bed to multimeter the volts and on 5 i got the dreaded red light (11.5v).    Does this mean theyre dead?  Theyve been charging up to over 13 everydaybbbbb

 

[Lowdesertpatrol]

You cant charge batteries "to just 13"

If you do not charge to at least 14.6v and hold that voltage until the amps go below 3-5% bank capacity you are destroying your batteries. Yes youve probably ruined 5 already and it shows sulfation has already taken hold. 2kw of solar is about half to 3/4 what you need for that size bank.

Take the 5 out out of the loop and you will be much better off. Even if they're not totally bad your bank will be closer to appropriate size for the solar. In fact take 7 out.

 

[brahmon]

thank you man!

 

[brahmon]

quick question, just out of curiosity and to learn.... how is it possible -- if these batteries are dead -- that they can still transfer power since one dead battery is an end/corner battery with solar powering thru from 3 mppt controllers. shouldn't a dead battery be just that? DEAD?

 

[B and C]

All your batteries are wired in parallel. The leads from the next battery transfer the power.

 

[Cajunwolf]

Here are my two cents worth. If you convert the 10000 BTUs to watts (10k divided by 3.41), you get just South of 3k watts per hour or 18k watts in 6 hours, if I'm reading your post right. If so, then I have to agree with @Lowdesertpatrol in that you not only don't have near enough solar, but the wrong kind of batteries too. You need deep-cycle lead-acid if you can't afford LiFePO4's. Marine starting batteries are just that, starting batteries with a quick burst of energy, and are not designed to be discharged and cycled repeatedly like solar house batteries.

 

[MrAlvinDude]

shouldn't a dead battery be just that?  DEAD?

Not really. As the energy storage in batteries are dependent on chemical processes. It is not a mechanical yes/no action. So, for as long as even a tiny bit of that chemical process can happen, then the battery will be able to accept a charge. It will however only be a percentage of the ability of the original process/charge.

So for different types of application, there will be a different %-level, of original capacity, where a battery will be considered "no longer useful" (or dead).

So a battery that might originally be able to service a certain load/task - let us say, for 3 hours - is very likely to be considered 'dead', when it can only sustain that same load/task for what? 1 hour, 30 minutes, 2 minutes?
Thus a very used/very sulfated  (and now very low capacity) battery will still appear to be taking a charge, but may do so in only minutes, as opposed to originally, in hours. And it will appear to be fully charged, if one only looks a the voltage, but the truth will be that only a very small percentage of the surface of the battery, is actually charged.

And this is for instance why it is not possible to fully evaluate how worn out a battery is, by only measuring the voltage.

At some point, it is no longer possible to charge the battery, and then it is dead-dead, but in reality, that battery has been useless for some time, and has been dragging better (parallel coupled) batteries down (for some time).

 

[MrAlvinDude]

To know the current actual total Ah capacity state, of each battery in your bank, you need to disconnect them (all) and perfor a capacity test on each battery.

A capacity test typically means:
- fully charging
- fully discharging (to a pre-determined lowest voltage) - at a known amp load, while measuring time (and voltage).
- fully charging - while measuring time, amp and voltage
And possibly repeating this processes a couple of times.


And then you will know which batteries to eliminate from your big 15 paralleled bank. As the weakest of the batteries (the one with the least remaining capacity ability) will be dragging all the better batteries down towards its (low) level.

 

[B and C]

Water level also plays a roll if water can be added.

 

[brahmon]

mralvindudemand cajunwolf i cant afford lithium but shouldn't have bought so many marine batteries. im just gungho into learning about this stuff since it's so fun. as they saynin thisnforum, its my starter pack that gets killed. fortunately walmart willnreplace em all form free. maybe ill upgrade to agms.

 

[brahmon]

brian i called everstart and 3 different reps boasted theyre "maintenance free" and that i "should NOT add any water."

 

[regis101]

* fortunately walmart willnreplace em all form free *

Because why ?

 

[highdesertranger]

AGM's won't help. 15 marine batteries had to cost at least 1,500 bucks. that would have gotten you a couple lithium's, I think.

if the caps come off you add water. do the caps come off?

highdesertranger

 

[Cajunwolf]

AGM's won't help. 15 marine batteries had to cost at least 1,500 bucks. that would have gotten you a couple lithium's, I think. highdesertranger

I agree and I bet it was a lot more than $1500 too. You say you can't afford Lithium, but you can at that price. You can go for 6-volt Lead-Acid golf-cart or Fork-Lift batteries in series to produce 12 volts and you've got yourself a heavy-duty battery bank, but heavy as hell, and cost more.

As to Lithium, you can buy the Raw LiFePo 3.2 volt Prismatic Battery Cells in 4-packs (4x3.2v Cells) in 100ah, 200ah, 300ah, and here 400ah for $2300, but you supply the BMS and assemble the battery ...

LiFePO4 12V400Ah Lithium Iron Phosphate Battery Pack

... for $2,299.00, and It's not hard to do.

 

[brahmon]

hdr. yes caps come off, but shouldn't i heed the manufacurer's advice? i now they're crap batteries and all, but... lol
i could've bought 150 ah of lithium. not enough. also, i don't like overpaying for overhyped product.

regis. walmart didn't even question my last battery. their revenues are so off the charts they can't be bothered with a crappy battery return.

 

[Lowdesertpatrol]

When you need a bank that size you go with 8D or L16's because you dont want 15 batteries in a string like that for various reasons that youre finding out now. You want to keep it like 4-6 in a group. And you need serious sized connector cables. Like 1/0+

One thing you can do is series-parallel what you have and run a 24v system.

Like I said 2kw seems big but its all relative. Its basically a little over 100w per battery. A 5-7 amp charger on a 100ah battery with only 5hr to fill it its ridiculously under sized. You need more like 10-15A per battery AND in reality a generator with ~200a converter to bulk charge. Those batteries can take 250A plus youre load.

You cannot keep undercharging lead acid like this. Its going to kill them very fast. They need 100% at least 3-5 days a week.

 

[highdesertranger]

they don't know what they are talking about then. also didn't they also tell you charging them to 13.8 was good enough? highdesertranger

 

[brahmon]

i went upstairs to sam's club today and checked out their 6v 75ah golf cart batteries for $89. so for a 12v system, i'd string 2 together for 150ah? not sure how that all works.

 

[brahmon]

they don't know what they are talking about then.  also didn't they also tell you charging them to 13.8 was good enough?  highdesertranger

yes, i know.   but they're the perfect learning batteries.  i blow em up and they replace em, until i know wtf i'm doing!  lol.  with all the great advice from you guys...

 

[highdesertranger]

aren't the Sam 6v golf cart batteries 215ah. anyhow to get 12v you would wire them in series which would double the volts but the ah's would stay the same. highdesertranger