2- 6 volt batteries or large 12 volt battery

[wrcsixeight]

Canuckmariner, apologies. Post edited.

But please post where you saw or read info that says drain the battery to 0 volts is a good way to favorably condition it. I can post hundreds of links that say that it is not favorable, quite the opposite. Starting battery or deep cycle.

Lithium ion/polymer and Nicad chemistries not included.

 

[CanuckMariner/Nomad]

CanuckMariner Im also curious about bringing a battery to zero and back up. What is your source/link on this system? Also goes against everything I have read on batteries.

Canuckmariner, apologies. Post edited.

But please post where you saw or read info that says drain the battery to 0 volts is a good way to favorably condition it. I can post hundreds of links that say that it is not favorable, quite the opposite. Starting battery or deep cycle.

Lithium ion/polymer and Nicad chemistries not included.

Thank you wrcsixeight. I neither saw nor read this procedure anywhere nor did I state this anywhere, just that I was told this. Check with your local Interstate rep or Optima rep if they agree. And even if the don't I am not sure that this is necessarily a bad thing.

When I picked up my 2 Blue Tops from an Interstate dealer here, the manager told me that Optima does this before shipping but didn't know why or when they started doing this. He said that he was told all deep cycle batteries should have this done before normal use. I said if I did this and my batteries don't work normally any longer; will he replace them under warranty? He said sure, so I did and never looked back.

When I called Optima tech support, they said the same thing to me and told me that deep cycle batteries where made to be used completely. He said they where made to run dead and will charge again. I re-asked if I were to say hook up an application (fridge or headlights) and run it until the battery was dead, it would still recharge back to normal? He sure, that's what they are made for. He went on to tell me about the voltage level that today's smart chargers need to work versus the old manual ones.

That's how I came across this procedure. I have done it about twice in 5 years, unknowingly (left lights on or an application) and then recharged without problems.

This is similar to camera/PC batteries but they are a different type. I have heard one should not keep them fully charged and plugged in all the time as this reduces the life expectancy. Discharge to zero and then store until required and then charge completely. This will prevent battery memory or hysteresis.

Nothing was said whether or not the battery would last longer. Simply it can be done without adverse affects.

I am sure I am not the first to leave something on and drain the battery. For the price they charge (no pun intended) for these AGM deep cycle batteries, I would hope they could stand the discharge...after all they are called deep cycle, not shallow cycle.

Hope that clears this up.:costumed-smiley-007

 

[kjp1969]

That's how I came across this procedure. I have done it about twice in 5 years, unknowingly (left lights on or an application) and then recharged without problems.

It seems that this is almost guaranteed to happen at least once in a vehicle based installation. Do some batteries die (as in dead, non-rechargeable) if this happens?

 

[CanuckMariner/Nomad]

It seems that this is almost guaranteed to happen at least once in a vehicle based installation. Do some batteries die (as in dead, non-rechargeable) if this happens?

Kevin, I think most starting batteries are not meant to discharge completely and leaving your lights on all day might damage the battery. Depending on manufacturer, they might stand that once or twice when new.

Deep cycle batteries are generally made for lots of discharge and recharge use and can handle this type of abuse much easier. Check with your local Battery supplier for more info on your type of battery before it happens.:costumed-smiley-007

 

[cnynrat]

It seems that this is almost guaranteed to happen at least once in a vehicle based installation. Do some batteries die (as in dead, non-rechargeable) if this happens?

Depends on a number of factors, including whether you are talking about a deep cycle battery or a starting battery, the age/condition of the battery when the "full" discharge happens, and exactly how discharged the battery becomes.

Discharge an older battery deeply enough and you can definitely destroy it for good (Kevin, ask me to tell you how I know this next time around the campfire ). On the other hand, for a newer battery or a little less deep discharge you may get away with it, but you probably have affected the lifetime of the battery.

For deep cycle batteries, the general rule of thumb is not to discharge below 20% of charge or you begin to affect the number of charging cycles the battery is capable of in its lifetime. For a starting battery a similar rule of thumb is not to go below 50% charge.

 

[ersatzknarf]

Hi Dave,
Great post. Thanks.
This has me rethinking the approach for our application.
I like this simple, direct approach.

I've been down this thought process a couple times, once with my Bigfoot camper, and again recently when one of the group 31's in my AT Horizon died.

Let's start with what I think you should not do, which is run two 12v batteries in parallel. Not sure, but this may have been what bit you with your Optimas. When running dual 12v in parallel, you think you might get double the capacity because in theory each battery will supply 1/2 the current. In reality small differences in the electrical characteristics of the batteries lead to them not sharing the load equally, which means one battery will discharge more rapidly. Another issue is parasitic discharge, which is when one battery charges the other because they aren't in an equal state of charge. Think about it, and you realize these two phenomena are closely related. So in the end, doubling the capacity proves elusive, and IMO these problems also tend to shorten the life of the battery.

You already got the answer to your question about whether you double the capacity running two 6v batteries in series. The reason you don't double the capacity is because both batteries are supplying the full current to the load. Say you have a 25 amp draw, well then both 6v batteries are supplying 25a to the load.

There are a couple other things to look out for with 6v batteries. One is that they tend to be tall, so you may not have room for them. For a while I wanted to go this way for my camper, but there was no way I was going to fit two 6v batteries in the space I had. The second issue is the charging voltage is often pretty high. Looking at the spec for a 6v Lifeline AGM battery, the voltage for bulk/acceptance/absorption charge is 7.1-7.3v That would mean to put both batteries in the most rapid charging mode you would need to provide 14.2-14.6v. My FJC voltage regulator tends to run between 13.2-13.8v. It would charge the dual 6v batteries at that voltage, but only at a slower rate. If you are talking about a trailer you also need to factor in the voltage drop in the wiring to the trailer, which will probably reduce that charging voltage even further.

So that brings me to what I think is the ideal solution, which is a single 12v battery appropriately sized for your requirements. In both my camper and the AT Horizon I've gone to a single group 4D battery with a little over 200 AH capacity. Expensive, of course, but not that much more than the cost of two group 31s with 90-100 AH capacity. Heavy, you bet, but actually marginally lighter than the 2 group 31s it replaced.

Hope this helps.

 

[wrcsixeight]

Depends on a number of factors, including whether you are talking about a deep cycle battery or a starting battery, the age/condition of the battery when the "full" discharge happens, and exactly how discharged the battery becomes.

Discharge an older battery deeply enough and you can definitely destroy it for good (Kevin, ask me to tell you how I know this next time around the campfire ). On the other hand, for a newer battery or a little less deep discharge you may get away with it, but you probably have affected the lifetime of the battery.

For deep cycle batteries, the general rule of thumb is not to discharge below 20% of charge or you begin to affect the number of charging cycles the battery is capable of in its lifetime. For a starting battery a similar rule of thumb is not to go below 50% charge.

This is good info.

While a good battery can be brought back from this abuse(full discharge) it has still been abused, and lost some capacity in doing so. The longer the battery has sat at those extremely low voltages, the less likely it is to recover. The health of the battery at the time of full discharge has a big effect too.


Perhaps draining them overnight with a 20 amp load like the headlights, then a prompt recharge is much less detrimental then say a single dome light taking 3 weeks to deplete them to the same level.

While some deep cycle batteries say they can be cycled down to 20% without damage, most advise not going below 50%. I have never read any that said full 100% discharges could be done without damage. They might recover, but they have been damaged and lost capacity. I have heard with starting batteries, 80% is the percentage not to go below for maximum longevity.

The shallower the discharge, the longer any lead acid battery will last
The quicker the battery is fully recharged, the longer the battery will last.
If the battery is left plugged into a float charger at 13.2 to 13.6 volts, every couple weeks the voltage should be briefly brought up into the high 14's.

The following is typed without a negative tone or sarcasm.

The Optima techs and dealer who said they fully discharge the batteries before shipping must be wrong, incorrectly informed, or both. It takes a significant amount of energy and time to fully charge a battery and this does not fit in with the bean counter, maximum profit at any cost mentality which pervades modern culture to a sickening degree. I have heard from someone who worked in an AGM factory that they blasted the AGM's with so much amps before leaving the factory that the vents were whistling. This hardly seems the right treatment for batteries either. It must be done with the confidence that the batteries will withstand such abuse, but, it is still abuse.

Lead acid batteries have no memory effect.

If anybody is interested in the the most recent battery info, the following link is the authority. It has hours and hours of reading, and many links to many hours more.
http://www.batteryfaq.org/

 

[wrcsixeight]

Generally, 12 volt batteries in parallel will have issues if they are different ages and sizes and manufacture, but only really if they are left in parallel while being discharged.

2 12 volt batteries that are equal in the above factors and are sitting next to each other and wired in a balanced manner will not suffer effects of one battery taking more of the load or charging than the other.

When you have one battery in the engine compartment, then another 24 feet away(Full circuit length) with an isolator inbetween, then yes the charge/ discharge rates will be very unequal, and one battery will die before the other.

With 2 six volts, they are going to be next to each other, and there is no way to wire them in an unbalanced manner. Think of 2 six volts batteries as just a 12 volt battery that comes in 2 pieces. All you need to do is hook a wire from the negative of one to the positive of the other.

Wiring 12 volts in a balanced manner means taking the ground off one battery and the hot off the other, instead of the ground and hot off the same battery. Imbalance becomes more noticeable with more than 2 batteries, with too thin of interconnecting wires, and higher loads, or charging amps. Generally with just 2 equal size/make/age/manufacture batteries in parallel, right next to each other, the difference would be negligible but indeed measurable for the over analytical.

The real issue with six volts is their height, and the fact that if one does develop a shorted cell, then you have a 10.5 volt battery, or just a 6 volt when removed. Lose 1 of 2 12 volt batteries, and you still have 12 volts to power your accessories, just half the capacity or approximately so depending on the load and the Peukert effect.

The issue with 12 volt batteries is that getting a true deep cycle battery is much more difficult as so many that list "deep cycle" also list marine, trolling, rv on them, which makes them a dual purpose battery, which is just a starting battery slightly more tolerant of deeper discharges. A true deep cycle 12 volt battery has much different construction.

With 6 volt golf cart batteries you are getting a battery designed to be deeply cycled. They do not make 6 volt golf cart sized starting batteries, and this, IMO, is why many people say they get better service out of them.

 

[GXWagon]

I have heard of this being applied to NiCad batteries, but I have never ever heard of this being applicable to lead acid batteries. It goes against every thing I have ever real about the care and charging of lead acid batteries, and I would be very interested to read it from Optima or Interstate if you can provide a link.

Yeah I would like to hear more on this as well

 

[dwh]

Yeah I would like to hear more on this as well

It's "Old Wive's Tale" BS.

Total drain and recharge is a recovery procedure used on some lead-acid batteries in some situations. But even then, only when needed.

No battery manufacturer that I've ever heard of recommends that sort of thing for a new battery.

Maybe 50 years ago when flooded batteries sat around on gas station shelves for years before being sold.


Odyssey does recommend it to recover their batteries if they aren't holding full charge voltage any more. But not a drain and then a dinky trickle charge. They recommend a drain and then full recharge at C*.4 (40 amps charge current for a 100ah battery).

 

[DiploStrat]

YES, but … NO! but maybe … Caveat Emptor!

This thread is a terrible mixture of good and bad information for lead acid batteries. Danger Will Robinson! There are some possibly fatal howlers in here! (And the usual suspects are offering correct advice.)

Much of this has been beaten into the ground and I am too lazy to try to do a line by line analysis. I would simply say this, don't believe me, don't believe your charger manufacturer, READ and UNDERSTAND the battery manufacturer's manual. I have Lifeline AGM's so you better believe that I have committed this to memory: http://lifelinebatteries.com/wp-content/uploads/2015/12/manual.pdf

All of the other manufacturers have similar documents, most are simply not as complete as the Lifeline manual. If you read this you will learn:

-- How to charge your batteries as fast as possible.
-- When to charge your batteries.
-- How to wire your batteries.
-- How to kill your batteries.
-- How long to kill your batteries.
-- How to avoid insomnia.

And, of course, how to become an Internet curmudgeon/know-it-all.

 

[GXWagon]

I would love to know if anyone with an SUV expedition vehicle has been able to fit 2x 6v batts under the hood. Or if not under the hood where did you put them? I have a 4Runner so if you did it on one of those even better. Photos please!

 

[dwh]

I would love to know if anyone with an SUV expedition vehicle has been able to fit 2x 6v batts under the hood. Or if not under the hood where did you put them? I have a 4Runner so if you did it on one of those even better. Photos please!

The energy density of lead acid batteries basically goes by weight. 100 lbs. of 6v batteries vs. 100 lbs. of 12v batteries - same thing, same power, same amount of storage capacity.

In other words, it doesn't make any sense to hassle re-rigging a 12v car to take two 6v batteries, when it's a hell of a lot easier to rig it for two 12v batteries - and you end up with same amount of power stored either way.

When you start getting up into big numbers, like 6 or 8 batteries. 300lbs., 400lbs, and more - then you get an edge in performance from larger, lower voltage cells.

But for anything that would fit in a Toyota...it isn't going to matter.

 

[GXWagon]

The energy density of lead acid batteries basically goes by weight. 100 lbs. of 6v batteries vs. 100 lbs. of 12v batteries - same thing, same power, same amount of storage capacity.

In other words, it doesn't make any sense to hassle re-rigging a 12v car to take two 6v batteries, when it's a hell of a lot easier to rig it for two 12v batteries - and you end up with same amount of power stored either way.

When you start getting up into big numbers, like 6 or 8 batteries. 300lbs., 400lbs, and more - then you get an edge in performance from larger, lower voltage cells.

But for anything that would fit in a Toyota...it isn't going to matter.

My thoughts where I would have the 12 volt started battery and 2 x 6v for the house batteries. Aparently 2x 6v battery will give you 200+ amp hours vs 12 volt only 100+

 

[dwh]

Aparently 2x 6v battery will give you 200+ amp hours vs 12 volt only 100+

Two 50 lb. 6v batteries will give you twice as many amp hours as one 50 lb. 12v battery.

Because 100 lbs. of lead-acid battery stores twice as much energy as 50 lbs. of lead-acid battery.

Two 50 lb. 12v batteries is going to have the same amp hours as two 50 lb. 6v batteries.