battery not charging

[numbnuts]

OK have two 95 amp hour batteries (deep cycle) connected pos to pos and neg to neg.
I left the light on in the caravan for a few days to discharge battery a bit and now they wont fully charge. I have one of those four amp battery chargers that is supposed to monitor the charge then just trickle charge to keep batt. full. the best i can get is 9.7 volts after a week. the batteries are just three months old.

[Oscars]

take them back to where u bought them and get them to test them

[bazooked]

deep cycle batteries are not ment to be run down totally flat, it litteraly fuks them, 9.7vlts also sounds like a dead cell, is this in both or just 1 battery?

[ausoops]

deep cycle batteries are not ment to be run down totally flat, it litteraly fuks them, 9.7vlts also sounds like a dead cell, is this in both or just 1 battery?

they are rooted

[-Scott-]

deep cycle batteries are not ment to be run down totally flat, it litteraly fuks them, 9.7vlts also sounds like a dead cell, is this in both or just 1 battery?

they are rooted

Yep. Don't tell the supplier about your "discharge test" (which wasn't a good idea) or they might try to void your warranty.

"Deep Cycle" batteries cope with deep discharge better than starting batteries (which don't like it, at all) but that doesn't mean deep discharging a Deep Cycle battery is a good thing.

Good luck,

Scott

[Toy80Diesel]

should fit a low voltage protector, they way when things get to a low level it shuts off, not harming the batteries.

I also agree they should have charged up by now and they might be faulty, or at least one of them, as you mentioned two are hooked together and one could be dragging the other down with it.

[drivesafe]

Hi numbnuts, although you haven’t stated what type of batteries you have, I’m assuming they are wet cells and you should never take them bellow 50% charge but by doing so, even to 10.5 volts, will not instantly destroy your batteries but it will shorten their operating life if you do it on a regular basis.

But even taking the batteries down to 10.5 volts on a regular basis, you should be able to do this around 50 times before the batteries are stuffed, so you could go camping once a month for 4 years before needing to replace the batteries.

The point I’m getting at is that flattening the batteries once should not immediately damage them so you should have a fair claim for having them replaced under warranty.

[spannercrab]

It's more like 80% of rated capacity for true deep cycle ... 50% for starter batteries.

Depends on the type of light it was also ... a fluro drawing 1A would drain 24Ah / Day - 72Ah Total drain, which isn't even 50% of the total capacity. So that would be no big deal and something which the batteries should be able to handle and then some.

Deep cycle batteries on various data sheets (e.g. US Battery, Trojan etc) suggest that their batteries will not reach full performance until they have been through a number (50 - 100) of deep cycles. One may glean from this that D/C batteries "like" to be excersised.

[drivesafe]

Hi spannercrab, all wet cell automotive batteries, whether they be cranking or deep cycle are not recommended to be discharged bellow 50% without the risk of shortening the operating life.

AGM batteries can be taken to lower levels of discharge but it varies depending on make.

Cheers

[spannercrab]

Battery life does decrease proportionally to the depth of discharge, however deep cycle batteries are rated to 80% DoD - but will last longer (almost 3 times) if only 10% DoD - but that kind of voids the point of having deep cycle in the first place? I would rather carry 1 x 220Ah battery and only get 1500 cycles than carry 7 of the same battery and get 4000 cycles only discharging to 10%

From the US Battery US2200 Deep Cycle Flooded (not AGM) data sheet:

For best battery life, batteries should not be discharged below 80% of their rated capacity. Proper battery sizing will help avoid excessive discharge.

And from WindSun's Battery FAQ:

Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates.

And from Trojan Batteries "Battery Maintainence" section:

3. 80% discharge is the maximum safe discharge.

4. Do not fully discharge flooded batteries (80% or more). This will damage (or kill) the battery

From Optima Batteries FAQ:

Deep Cycle refers to applications that typically discharge 60 to 70% or more of the battery capacity.

From Battery FAQ (Cornell):

11.14. Avoid shallow (below 10%) discharges of deep cycle batteries because lead dioxide builds up on the positive plates. In other words, you should discharge a deep cycle battery between 10% and 80% Depth-of-Discharge.

From Pacific Power Batteries FAQ:

There are 50% depth-of-discharge limits and sponge lead plates batteries, and there are the more expensive Deep Cycle (traction and stationary) batteries with 80% depth-of-discharge limits, solid lead plates, and longer lives.

[drivesafe]

Spannercrab, you can post all the web data you want but if you read what I posted, I stated you can take the battery down to 10.5 which equals 0% charge and you will not instantly destroy the battery, BUT you have to take in to consideration that you will eventually shorten the life of the battery if you do this regularly.

Most people don’t realise that many of the portable fridges on the market, with automatic low voltage cut-outs, do so at 10.5 volts so the more you use them the shorter the life span of your is going to be.

As you pointed out, you can deep discharge your 220 a/h battery so many times, to give you the power you require and have to replace it much sooner than if you carried 7? actually you only need to carry 2 batteries and you will extend the extend the life of the batteries, which is exactly what I posted, but all of this has nothing to do with numbnuts problem.

I was simply pointing out that one deep discharge is not likely to destroy his battery and that he should be able to make an honest claim based on what he posted.

Cheers.

[spannercrab]

whether they be cranking or deep cycle are not recommended to be discharged bellow 50% without the risk of shortening the operating life.

I was merely responding to this comment that a Deep Cycle battery is not intended to be discharged beyond 50% of it's total capacity - the manufacturers (Trojan, US Battery, Optima, Exide, Sunpower) all recommend that the safe discharge for their deep cycle batteries is 80%, not 50%. 50% applies only to sponge material starter batteries - you clearly stated that *any* battery is not recommended to be discharged below 50%.

I was furthur stating the anything beyond 10% will "severely" shorten the life of your battery - but no more than the difference between 10-30% will opposed to 50 - 80% for deep cycles - the same does not apply to a starter battery. Whereas beyond the recommended (80 or 50 respectively has the serious potential to shorten the life significantly).

7 batteries will extend the life of your batteries even furthur (in terms of number of discharge cycles available), by only discharging to 10% not 50 or 80% regardless of battery chemistry or construction.

I agree with your comment entirely re: 1 deep discharge won't destroy a battery (or is very unlikely to) .

[-Scott-]

whether they be cranking or deep cycle are not recommended to be discharged bellow 50% without the risk of shortening the operating life.

I was merely responding to this comment that a Deep Cycle battery is not intended to be discharged beyond 50% of it's total capacity - the manufacturers (Trojan, US Battery, Optima, Exide, Sunpower) all recommend that the safe discharge for their deep cycle batteries is 80%, not 50%. 50% applies only to sponge material starter batteries - you clearly stated that *any* battery is not recommended to be discharged below 50%.

I was furthur stating the anything beyond 10% will "severely" shorten the life of your battery - but no more than the difference between 10-30% will opposed to 50 - 80% for deep cycles - the same does not apply to a starter battery. Whereas beyond the recommended (80 or 50 respectively has the serious potential to shorten the life significantly).

7 batteries will extend the life of your batteries even furthur (in terms of number of discharge cycles available), by only discharging to 10% not 50 or 80% regardless of battery chemistry or construction.

I agree with your comment entirely re: 1 deep discharge won't destroy a battery (or is very unlikely to) .

That's right. One deep discharge won't necessarily destroy a battery. But the supplier might try to argue if they find out, so don't volunteer information which may complicate the issue.

Manufacturers are happy for you do discharge to 80%, because you'll still get a reasonable number of cycles, and they hope to get another sale sooner.

It's been a while for me, but the last time I saw a graph showing depth of discharge vs cycles, it was very much in favour of recharging more often. If this is no longer the case, I'd love to see some links.

Cheers,

Scott

[spannercrab]

Hi Scott,
I don't think it's changed an awful lot, although it looks like some of the newer Exide deep cycle technology can give a much higher number of discharge cycles comparative to the flooded batteries. Just sponge plate batts are damaged more easily and can handle less DoD.

Agree with not volunteering information - especially to retailers who may have a different view of what is warrantable and what isn't - although the couple of times that I've had batteries replaced because of failure during the warranty period it's been on a "no questions asked" basis.

Carbon pile load test failure result = new battery under warranty.

[drivesafe]

Hi spannercrab, I think you are getting a little bit of crossed wires when relating data about different batteries.

Some of the batteries you have listed are AGM batteries and are not commonly known as wet cell automotive batteries and Sunpower is not an automotive battery.

The term Wet Cell battery relates to either batteries that can have the water topped up by means of plugs or are the gel type maintenance free batteries.

AGM ( Absorbed Glass Mat ) such as the all Optima batteries and some of the Trojan and Exide batteries, and are a different type of battery with completely different charge / discharge and maintenance stats.

Even Trojan, although stating their batteries can be discharged down to 0%, lists a graph that shows the dramatic shortening of the life span of the battery based on discharge rates bellow 50%.

The best long term economics for battery use is to use a bigger battery so as not to have to discharge it as low as you would with a smaller battery. This will give you a much longer operating life and, in the long run, work out cheaper than continuously replacing the smaller battery.

This is an over simplification but is the basics for good dual battery set ups.

Cheers

[spannercrab]

Hi drivesafe,
I'm aware that some of the manufacturers I listed do make batteries of different chemistries and constructions - and specifically I was talking about flooded lead acid, but was making the point that other chemistries apart from standard flooded lead acid are recommended to be discharged to a safe limit of 80% without adverse effect, I am not in anyway discluding FLA D/C batteries from the discussion, merely adding more to the mix.

I am generalizing 80% to all different types of batteries because this is the recommendation given by the manufacturers of all these different types of batteries.

AGM is still a flooded lead acid type - with AGM separators instead of gel retainer - although these are not vented, but they are still wet batteries.

As numbnuts original enquiry related specifically to a caravan, this opens up a whole variety of different typs of batteries available to him - not specifically an automotive type, so it could full well be an AGM, traction, stationary or any other deep cycle battery as heat absorption is not typically a problem in a caravan situation. We are not talking about a dual battery setup, but a caravan setup.

If you intend to take a battery down to >80% DoD, the yes, the best economics is to use a larger battery as you will more than likely be replacing it regularly - but my original statements in response to yours, based on the manufacturer data, is that taking a battery down to 80% DoD is still a safe limit and will not have an adverse affect on the battery life in terms of charge cycles, and it is more efficient cost wise (given a 5 year ceiling on an average traction battery) especially when used intermittently in a camping / caravaning situation It will not cause plate separation on a deep cycle battery, it will not increase the likelyhood to near certainty of a cell dropping out, going open circuit or shorting (as numbnuts has likely experienced - could probably tell with a hygro) - unless the manufacturer of the battery specifies otherwise, as these are the terms and conditions of use of the battery.

At no point did I suggest that it was "Safe" to take a battery down to 100% DoD. Trojan do not specify this as a capability - from Trojans www:

Do not fully discharge flooded batteries (80% or more). This will damage (or kill) the battery.

In your original statement you specifically said that:

... all wet cell automotive batteries, whether they be cranking or deep cycle are not recommended to be discharged bellow 50% without the risk of shortening the operating life.

- this is the specific statement that I am talking about.

[drivesafe]

You have still missed the point, it’s not that they can’t be taken bellow 50%, it’s that the long term economics of having to replace the battery far more often because of taking it bellow 50%.

As I posted, you can get all the info you want, from the different manufacturer’s sites as long as you know how to use that info to your own benefit, or it’s a waste of time.

Again, as some of the batteries your mentioned, are not wet cell, the manufacturer’s info is irrelevant.

Cheers.

[spannercrab]

I understand your point - you are saying that if you take ANY wet cell battery beyond 50% DoD, then you will shorten the life enough that it would be financially better to invest in a larger capacity battery and only discharge to 50%.

I disagree with this to the point that this is arbitrary 50% figure for financial viability is applicable only to sponge plate starter type batteries NOT deep cycle batteries.

It's all well and good to say "you can get whatever information you want" but at the end of the day you have provided nothing except for your opinion as to why this is the case.

Which battery manufacturers or battery industry institutions recommend this arbitrary 50% figure as the most economical use of ANY battery? I have looked and cannot find any recommendatation to support this.

The only manufacturer I provided which are not wet cell batteries (and only on your hear-say - AGM is still a type of wet cell battery) is Optima relating to AGM batteries, so if we take that away, that leaves 5 manufacturers who specify an 80% DoD limit for wet cell deep cycle batteries and zero manufacturers who recommend only a 50% DoD. I've not found one yet who specifies only 50% DoD for deep cycle batteries.

I quote your original statement:

... all wet cell automotive batteries ... are not recommended to be discharged bellow 50%

I'm asking who's recommendation is this and where is this information coming from? Please point me in the right direction as to where I can find an article that supports this recommendation.

[drivesafe]

Hi spannercrab, you have your opinions on this subject, I have mine but neither of which now has much relevance on the original post by numbnuts so I will leave this where it is.

Cheers

[spannercrab]

drivesafe,
It really isn't a matter of opinion, it's a matter of published fact.

All I'm asking is that you reveal the source of your recommendations, as you seem adamant that you have information relating to the subject that is not available to the rest of us.

If I'm wrong about 80% being the manfacturer recommended "safe" DoD for flooded wet cell, then I'd really like to know about it so I might change my own usage habits of my flooded deep cycle batteries.

[drivesafe]

Hi spannercrab, this is way off subject but for you benefit, I base my posting on hands on experience and the feedback my customers give me.

As I have repeatedly pointed out, the best set up is designed to get the most economic value for the customer while at the same time making sure the system meets his needs.

And again, you have to use the info supplied by the manufactures to your advantage by working out which is the most economical operation. Do you continually run a small battery flat knowing that you will have to replace it after a short period of time or do you fit a larger battery or a number of batteries with the idea of not over working them and getting a much longer operating life from them.

From experience, the latter is the one the customers prefer so who am I to argue with them,

Cheers

[-Scott-]

Don't work solely off the manufacturer's recommendation. They are in the business of selling batteries - nothing else.

If they recommend a 50% DoD, the customer will calculate the size of the battery they need. The next manufacturer recommends 80% DoD, so the customer decides they can use a smaller battery, which is cheaper.

Hmmm. Which way will the customer go? Is it any wonder that all manufacturer's recommend exactly the same DoD?

Of course, if the customer uses a 50% DoD the battery will survive many more cycles. If the customer uses 80% DoD, the battery will lose capacity sooner, and the customer is back in the market for another battery. Hmmm. Why would this be bad for the manufacturer?

OK, so perhaps the manufacturer could recommend 90% DoD? No, the number of cycles at this depth is ridiculously short, the customer will be left with a bad impression, and that manufacturer will have lost a customer.

Manufacturer's don't necessarily recommend best practice - it's not necessarily in their best interest.

Some suppliers are more interested in keeping the customer happy than making a sale - it's easier to keep a customer than to gain a new one.

Treat the 80% DoD as an absolute maximum. Less is better.

Scott

[spannercrab]

drivesafe,
I can appreciate that you have experience - and I can appreciate also what you are saying re: economics - that there is a proportional relationship between DoD and battery life, and a battery system should be designed in the most economical way.

I don't disagree with you on this point in any way. This is not the issue - rather the issue is the arbitrary 50% figure you say is recommended

Where do you get your 50% figure from and how do you measure this outside of a controlled lab environment?

How do your customers measure to only 50% DoD consistently cycle after cycle? Surely they don't all carry hygrometers around with them to check the charge state? As introducing high temperatures to batteries and variable loading makes volt meters as a capacity checking method totally useless.

How can you be sure that their charging methods are approprate and the battery damage done to heavily discharged batteries isn't done during high-amp charging greater than C/10 (or whatever the manufacturers recommendataion is?) causing plate warpage or boiling? Or low-amp charging with an insufficiently sized charger? or improper configuration or running of the vehicles charging system? Or a correlation between excess heat, deep discharge and battery failure?

Perhaps for a given setup which you install, based on your customer feedback - 50% might be the average, but given a different set of circumstances, this figure could change.

Are these cases all related to deep cycle only wet cell (not combination batteries)? Given such a wide array of variables - how do you quantify all these results from real world situations into data?

Who, specifically, recommends 50% is the most economical DoD for their batteries?

As you say - is there a point in running a battery "flat" - well - what is "flat"? Is it 50%? or 80%? or 90%?

[spannercrab]

Hi Scott,
The recommendations I am referring to are not all manufacturers data - in fact half of them are researched papers in which 80% is the correct DoD for flooded lead acid and are based on the level of discharge acceptable before damage will start to occur.

The actual-absolute-you-are-taking-a-huge-chance-maximum figure is closer to 90% for deep cycle batteries only.

This is the point at which I'm sticking - it's the point where damage is likely to occur - not which will give you the most cycles. The point at which you get the most cycles is - leave it at 0% DoD charged 100% of the time, and the battery will last the longest - discharge only to 10% DoD and you'll get 2000 cycles - discharge to 80% DoD and you'll get only 800 cycles.

The original post by numbnuts was about caravan batteries - not that I'm trying to side step the overall issue, but specifically the 80% I came up with was relative to deep cycle batteries installed in caravans or campers, now most of these caravan or camper batteries would be lucky to see 100 full cycles to 80% before their 5 year lifespan average is reached, so the killer then is age - not cycle depth resulting in life degradation.

So why then, assuing that at a higher DoD you are only going to get 600 cycles, but only ever use 1-200 of them, is it economical for battery manufacturers to make this arbitrary recommendations. As I mentioned, these recommendations are not only from the battery manufactureres themselves, but other independant sources.

You are more likely to experience sulphation in a flooded battery which is discharged to a lesser DoD than more also, so how is this economical? Which shortens battery life - much of the time - severely.

80% is the maximum, that's the point - not 80% average DoD, but as a maximum.

Cheers,

[drivesafe]

Spanner, real world use is the only way you are going to see how long a battery is going to last if you cycle it to 80%.

At 80% cycling you would be lucky to get 50 cycles before the is stuffed and this is based on 18 years of designing, manufacturing and supplying dual battery charge controllers and as we have thousands and thousands of them out there and get a large amounts of feed back, I’ll stick with the real would stats and you can keep all your reading material for a cold nights amusement.

You already covered a number of problems that in themselves or COMBINED will shorten the life of a battery and again by avoiding taking the battery below 50%, you go some way to wards battery life longevity.

Scott put it perfectly and you can do what you want with your set up and post here what you think is the way to do it and everybody else can do the same but don’t just base your info on data acquired lab notes or manufactures info is not going to give you a working situation that meets the needs of most people. Real would operations require real world understanding of how these dual battery systems REALLY work.

Cheers.

[spannercrab]

So really the crux of the topic is that you are saying that you, personally, through experience, recommend 50% maximum DoD - by saying "it is generally recommended" - you are alluding that the majority others, other than yourself share your view and recommend 50% as a maximum DoD, which is simply not true.

My experience with deep cycle batteries is different to yours - I stopped using parallel charge mechanisms many years ago - I use a three stage charging algorithm both on and off vehicle, so far there are about 100 cycles on this set batteries, and they still test to 98% of capacity. These are flooded wet cell lead plate vented "old school" batteries - nothing fancy except for the charging techniques and monitoring DoD, levels and cell equlization.

This is proven with real world data, from which I have seen first hand not just text books and fact sheets (which is also gained from real world data, I might add) - I have data loggers on these batteries to monitor their capacity, cycle time, DoD etc. These 220Ah 6V deep cycle batteries are regularly drained to 80% DoD - so again your arbitrary "50 cycles" is something which is relevant only to your systems and installation methodologies and particular circumstances.

If you work to alleviate the other causes (heat, overcurrent, overvoltage) through proper or alternative mounting, three stage charging instead of just relay paralleling etc), it stands to reason that you can then achieve 80% DoD without shortening the life of the battery - and this is the whole point. Why would you ignore these other factors when it's clearly more economical to do something properly in the first place.

[-Scott-]

OK - now we seem to be getting somewhere. spannercrab has what sounds to be a very sophisticated system which allows careful monitoring of charge levels and controlling of charge rates. It sounds like an excellent system, and I'd like to learn more about it. Precisely what do you use it for?

But to generalise that 80% DoD is appropriate for your average 4wder with Engel fridge, Redarc isolator and Bosch voltage regulator on a 60A alternator, operating at high temperature under the bonnet of a 4wd vibrating up the Gibb River road? Horses for courses.

Scott

[drivesafe]

So spannercrab, what you are saying, is that we should all spend a fortune and loads of time nursing and monitoring the batteries, to achieve what can be do for a fraction of the cost and no monitoring at all.

Spannercrab, if this is your thing, thats great but to get anywhere near the accurate data that you are saying you have, you would have to have spent around $500 just on the battery monitor alone.

But again, in the real world, 95% of uses would be just happy to have a system that at the end of a days drive will give them the power they require, to operate their accessories for what ever time they need it to.

For about half the cost of just your monitor alone, they can set up the system that best meets their needs and when you take into account that most uses will not have either the foggiest idea of how to use a monitor nor would they want one. Based on years of hands on experience, the vast majority want nothing more than a fit and forget system.

If you personally like playing with that form of high end gear, go for it.

I have banks of batteries here, which I use for testing equipment and monitor it but this monitoring is for testing purposes only.

Once the majority of my customers have the gear in the vehicles, all they want, is for it to give them the power they need but they don’t want to know about it or how it’s working.

As Scott put it, horses for courses.

Cheers.

[spannercrab]

Scott,
It all sounds very fancy but not really - just an Amplepower 3 stage alternator regulator w/dual battery control (v3) for the truck, then 240v charging / float is achieved via either a 16 or 40A smart (3-5 step) charger(s) (one's a Projecta, the other is a home made job). The data logger is a Plastmatronics PL20 (which is also 3 step charge from solar). A also have another data logger based on a PIC16F628 which I can use for more involved information). I don't actually use a dual battery system in the truck as the heat under the bonnet (esp. in the Patrol - as a dual battery would have to be exhaust side) I deem to be too great to get the best life out of the batteries - besides the biggest battery I can find (at a pinch) to squeeze into a N70ZZ size hole is 100Ah. The batteries I use are a bank of 4 x 225Ah traction batteries on the camper.

So yes ... maybe it's a pretty complex setup ... and not all entirely necessary - but it gives me enough data and experience to make the statements that I make. Perhaps I should qualify:

"If you follow the manufacturer charging instructions - then you can safely discharge to 80% DoD with no adverse consequences".

Personally - I want to be able to use the full 500Ah @ 12v available to me, for as long as possible. The thing I want my batteries to die of is old age - not sulfation, warped plates, lead oxide build up etc.

drivesafe:

So spannercrab, what you are saying, is that we should all spend a fortune and loads of time nursing and monitoring the batteries, to achieve what can be do for a fraction of the cost and no monitoring at all.

No: what I'm saying is that you should follow the manufacturers recommendations for charging and maintaining batteries - following on from that you can then achieve the appropriate DoD with no adverse affect.

The same as when my vehicle manufacturer tells me to change the oil and filters in my car - I do that also (do you?). I also occasionally get the oil analysed, and realize that I don't have to change the oil every 5000km, but I do anyway ... so that I can get the best possible life from the engine. Sure - oil and filters are expensive - but I'm happy to spend the money to increase the life of my vehicle.

Same as I do the batteries - $1000 worth of deep cycle batteries - if I only got 1/2 the life from them - well ... there's $500 right there ... money better spent on a smart charger ... which is also fit and forget. I think of it as preventative maintenance. Or, if I only discharge to 50% instead of 80 or 90, then that's still $400 ... which still equates to a smart charger.

95% of people would love to drive round in a car and not have to service it, i surely would too - but sadly, if you want longevity, that's not the case. Same as they would love not to wash the outboard, change the washers in their taps, or change the blades on the lawnmower.

I guaruntee you that every motorhome owner with a bank of deep cycles has a smart charger attached to it - still fit and forget - but gives the best long term value for money.

Maintainence and proper installation is a part of life - either do it properly, or deal with not having the battery life as well ...

If your customers really are so technially lazy as to not want to know about the state of charge - how do they know if it's at 50%? How do you tell them "make sure you don't discharge beyond 50%".

Even following your train of thought, assuming you fit 1 x 80Ah battery to a customers vehicle & then say "but don't go below 50%!", and then further suppose that this customer wants 30% more life out of his battery. Do you suggest to go and buy a $60 Projecta 3-step charger so he can discharge to 80%, or do you then just fit an additional battery at a cost of $250 (by the time you take into account the battery, extra tray and wiring). I know which one is more economical.

[drivesafe]

Your theoretical evaluation is very nice but as stated above, has absolutely nothing to do with the real world.

Very, VERY few people are going to spend that sort of money, specially when it is going to cost them heaps more than a basic system and NOT give them any significant beneficial gain and that includes things like motor homes.

Cheers.