Optima Battery Problems

[dwh]

I'm more interested in the relevance of the bulk charge etc. and how the voltage and amperage rates interact with the battery. You seem to know a bit about it so let me know what you think. I'm interested in how this might compare to what my alternator is doing to the Optima but not the DieHard.

I'm not sure exactly what your question is...

Bulk Stage: Take the battery up to a certain "surface charge" voltage to get it recharged to 80% or so fairly quickly. Most AGM and flooded specify 14.4v for this, but some chargers will go higher. As previously mentioned, the Iota with IQ/4 module goes all the way up to 14.8v. Without the IQ/4 module, the Iota has a dongle to set bulk voltage to either 14.4v (dongle unplugged) or 14.6v (dongle plugged in).

Absorb Stage: Drop the voltage to a lower value and hold it there for some hours to get that last bit into the battery to reach full charge. The usual scheme is to hold at 14.2v until the amperage flow drops below 2a or so, then switch to float.

Float Stage: Drop the voltage to an even lower value to hold the battery at full charge without holding it at overcharge voltage. Generally 13.2v-13.6v.


That's 3-stage. 2-stage chargers omit the absorb stage and drop straight from bulk to float. The Iota without IQ/4 is a 2-stage charger. The bigger Battery MINDers are 3-stage, but that little one you linked to is a 2-stage.


Then there is:

Constant Voltage: Set the charger to a specific voltage and let the battery creep up till it gets there. 99% of all automotive "bench top" chargers are Constant Voltage. The amount of amps that flow is limited either by the resistance of the battery or the max output of the charger. The resistance of the battery is highest at both ends of the scale - when it's either dead or fully charged.

Constant Current: Keep cranking up the supply voltage until a specified amount of current - such as 15a or 25a or whatever - is flowing.

Current Limited: Put a cap on the amount of current allowed to flow - again, such as 15a or 25a or whatever. All battery chargers, either constant voltage or constant current are also current limited.


Alternator / Voltage Regulator setups are basically constant voltage.

The voltage regulator controls a sort of "electrical clutch" in the alternator - the "field current" or strength of the magnetic field of the rotor.

When the voltage on the battery side of the regulator hits (usually around) 13.5v, the regulator "engages the electrical clutch" by applying power to the rotor's field coils and the alternator makes power. When the voltage on the battery side hits (usually around) 14.5v, the regulator cuts power to the rotor's field coils and "disengages the electrical clutch" and the alternator "freewheels".


With constant voltage type charging systems, you set the voltage and let the amps fall where they may. So a million amp alternator might only be producing 5a if the battery is at the regulator's set point voltage and there are only 5a of loads drawing down the bus voltage.



So what happens with two batteries in a truck connected together by say a solenoid?

The voltage regulator will switch on the field coils in the rotor and the alternator will make power and the batteries will absorb however many amps can flow through them. Once the two batteries reach a "surface charge" of 14.5v, then the voltage regulator will switch off the rotor and the alternator does nothing.

Then the "bus voltage" (the batteries and the rest of the 12v system in the vehicle) will drop below 13.5v if there is any load - such as a radio and some headlights. When it gets down to 13.5v the voltage regulator switches the alternator back on again. This will happen pretty quick if the batteries were only at a high surface charge and not really fully charged.

Rinse and repeat and eventually both batteries will end up pretty well fully charged. If one battery - for instance the secondary or "house" battery - is deeply drained, then it can take anywhere from 8 hours *of driving* up to 24 or even 36 hours *of driving* to get it charged up fully. (I.e., fully absorbed as opposed to just pumped up to a shallow surface charge.)


Since AGMs and flooded batteries take basically the same charge voltages, they will be fine when connected in parallel to a constant voltage system such as almost any bench-top charger or a vehicle charging system.

They'll also be fine connected together to a 2-stage charger.

Same with different size batteries. Same with different age batteries.


However...if you hook up two different size batteries to a 3-stage charger - the smaller battery will usually be way overcharged by the time the larger battery has finished absorbing - so that's a bad idea.

Also a bad idea to hook a newer battery and an older battery to a 3-stage (even if they are the same type/model of battery) since the older battery will have a lower capacity than the new one and will end up overcharged.


And of course, batteries rigged either in series or rigged in a full-time parallel bank (instead of just connected when charging such as a vehicle solenoid setup) should always be identical make/model/size/age.


GELs take a lower charge voltage than AGM/flooded and there definitely ARE "GEL Specific" chargers. Morningstar solar charge controllers have a dip switch - flipped one way it's set for "AGM/flooded" and the bulk is set to 14.4v. Flipped the other way and it's set for "GEL" and the bulk is set to 14.2v. Samlex chargers usually have the same switch but the GEL setting is 14.0v instead of 14.2v.

 

[dwh]

All batteries suck and thats why Nikola Tesla and his competitor Albert Einstien spent sleepless nights inventing the electric company.

Wait...what?

 

[teotwaki]

-------snip---------

Alternator / Voltage Regulator setups are basically constant voltage.

The voltage regulator controls a sort of "electrical clutch" in the alternator - the "field current" or strength of the magnetic field of the rotor.

When the voltage on the battery side of the regulator hits (usually around) 13.5v, the regulator "engages the electrical clutch" by applying power to the rotor's field coils and the alternator makes power. When the voltage on the battery side hits (usually around) 14.5v, the regulator cuts power to the rotor's field coils and "disengages the electrical clutch" and the alternator "freewheels".

With constant voltage type charging systems, you set the voltage and let the amps fall where they may. So a million amp alternator might only be producing 5a if the battery is at the regulator's set point voltage and there are only 5a of loads drawing down the bus voltage.

So what happens with two batteries in a truck connected together by say a solenoid?

The voltage regulator will switch on the field coils in the rotor and the alternator will make power and the batteries will absorb however many amps can flow through them. Once the two batteries reach a "surface charge" of 14.5v, then the voltage regulator will switch off the rotor and the alternator does nothing.

Then the "bus voltage" (the batteries and the rest of the 12v system in the vehicle) will drop below 13.5v if there is any load - such as a radio and some headlights. When it gets down to 13.5v the voltage regulator switches the alternator back on again. This will happen pretty quick if the batteries were only at a high surface charge and not really fully charged.

Rinse and repeat and eventually both batteries will end up pretty well fully charged. If one battery - for instance the secondary or "house" battery - is deeply drained, then it can take anywhere from 8 hours *of driving* up to 24 or even 36 hours *of driving* to get it charged up fully. (I.e., fully absorbed as opposed to just pumped up to a shallow surface charge.)


Since AGMs and flooded batteries take basically the same charge voltages, they will be fine when connected in parallel to a constant voltage system such as almost any bench-top charger or a vehicle charging system.

They'll also be fine connected together to a 2-stage charger.

Same with different size batteries. Same with different age batteries.

snip----------

Thanks for your patience! You are helping me out here, way more than U-Know-Who..... :elkgrin: In essence, I might be ignorant of battery issues but I'm not stupid so this is great stuff.

Your information has given me so much to think about and I'd like to explore it much more because the Optima Engineer was never allowed to freely converse as you have.
I also think that much of the information that I have given previously may line up with it but they were just pieces of a puzzle, laying about. So I'll focus on those and not touch on battery quality.

(I have to reroute the CAT-5 cable for my Internet in just a bit so I'll try to throw things out quickly. Yes Cat-5. Physical security that WiFi cannot beat!)

Recapping, some key issues are the different state of charge of my batteries once the truck has started, parallel connection (solenoid) to the same constant voltage charging source (alternator) and available recharge (drive) time. All of these may add up to why the battery always needs an external charge treatment during average weekday driving but the fridge was cycling normally while the truck was parked. I think OJ touched on it indirectly when we were going over the amp hours taken out of the Optima versus the amp hours out of the starting battery each day.

I believe that the second issue is most important, that a hard wired (solenoid) connection may be the wrong design for this application especially if drive time is "short". There are intelligent solenoids out there that first ensure the primary battery is charged and then switch the alternator's output to the second battery. In an earlier post I pointed to a DC-to-DC battery charger that eliminated the need for solenoids and effectively isolated the two batteries from the alternator and each battery can get the charge that it needs, independent of the other's needs.

If the starting battery charged up quickly would the alternator then "back off" and the deep cycle battery would only receive a surface charge if the drive time is short? Short may mean 2 hours a day or something like that. Some of my amp readings on the Optima cable may point to this as I saw same decently high amps at first but they seemed to go low fairly quickly. The battery meter readings might also support it.

Gotta run. I can read on my PDA but it is a Pain in the PDA to type and edit much.

 

[dwh]

I believe that the second issue is most important, that a hard wired (solenoid) connection may be the wrong design for this application especially if drive time is "short".

The solenoid is not the issue. The issue is that the drive time is short. It's enough to recharge a couple of amp hours that were taken from the starting battery to start the truck, but not enough to recharge a more heavily depleted secondary battery.

So it doesn't really matter if you rig a solenoid, or suck power out of the primary and deliver it to the secondary (DC-DC charger) - you still aren't driving enough to replenish the missing watts.

There are intelligent solenoids out there that first ensure the primary battery is charged and then switch the alternator's output to the second battery.

That's not what actually happens...

With that type of unit, the brain senses that the starting battery is charged, and then TIES the two batteries together. The alternator output is not switched from one to the other - the second is added to the "12v bus".

The 12v bus is all the 12v stuff - the batteries, loads, alternator, etc. When the solenoid is disengaged, you have 2 separate 12v buses, but when the solenoid is engaged, they are tied into a single large 12v bus.

Imagine it this way...

You have two separate air systems - each has one tank and some lines and air outlets where you plug in tools and paint guns and whatever. But you've only got one compressor.

Then you put in an air line to tie the two systems together, and use an electric solenoid valve on that line.

Now say the primary air system is at 13 psi and the secondary is at 12 psi.

What happens when you open the valve?

Air flows from the primary system to the secondary system until the pressure in both systems is equal at something like 12.5 psi.

If the compressor is running, it will then raise the pressure of the whole shooting match to whatever the pressure switch (same as a voltage regulator) is set at and then the switch will shut the compressor off.


That's basically what happens with a solenoid setup. There are a couple of different brains. One just waits until the pressure (voltage) in the primary system is at a certain point and then opens the valve. Another will watch both sides and if the pressure in either one reaches charging pressure, it opens the valve.

One big difference between what I just described and the electrical version of the same thing - is that the flow from one battery to the other won't happen quickly. This is due to the resistances of the batteries.

In an earlier post I pointed to a DC-to-DC battery charger that eliminated the need for solenoids and effectively isolated the two batteries from the alternator and each battery can get the charge that it needs, independent of the other's needs.

Haven't been around much and missed a bunch of posts in this thread and didn't catch that. Could you repost the link to that unit please?

If the starting battery charged up quickly would the alternator then "back off" and the deep cycle battery would only receive a surface charge if the drive time is short?

The alternator will shut down when the "12v bus" reaches surface charge voltage. In other words, when BOTH batteries reach surface charge voltage. The primary might not be fully recharged (hasn't fully absorbed all it can) either. But yea, you've got the right idea.

When the alternator shuts down, the voltage of both batteries will drop some, but the secondary will drop further, faster. This will pull down the voltage of the 12v bus and cause power to flow from the primary battery to the 12v bus. Some of that will trickle into the secondary battery since it is now a load on the bus instead of a supply. Eventually the alternator will come back on to bring the bus voltage back up. Some of that will flow into both batteries.

Rinse and repeat until both batteries are finally totally full.

 

[762X39]

:lurk:

 

[teotwaki]

Projecta DC-DC charger. There have been arguments about their wording but FWIW here is the data sheet:

http://www.projecta.co.nz/Images/PDFs/Power-Management/DC-Battery-Charger.pdf

 

[teotwaki]

:lurk:

This is a good one for switching the alternator between batteries... :elkgrin:

 

[dwh]

Projecta DC-DC charger. There have been arguments about their wording but FWIW here is the data sheet:

http://www.projecta.co.nz/Images/PDFs/Power-Management/DC-Battery-Charger.pdf

(Anyone else notice that the truck in that first pic in the .pdf looks like a modern version of Casa Azul?)


Yea, that's a typical DC-DC 3-stage charger.

It doesn't "switch the alternator's output from the primary to the secondary" as you described.

What it does is draw power from the primary bus at whatever voltage and then step it up to 14.4v and feed it out as a 3-stage charge to the secondary bus.


The issue with DC-DC chargers is making sure that the charger doesn't draw down the primary too far. Some DC-DC chargers use voltage sensing, and when the primary drops to say 13.5v it stops sucking power from the primary.

This charger handles the issue by being switched on via the ignition switch.


Now, this charger does have an obvious problem that I see right off...this is a well-known issue with 3-stage chargers...

The problem is the absorb stage. If you look at the last page of that .pdf under the section called Charge Control, you see that it holds the absorb stage until the current flow drops below 3 amps.

The problem is this:

What happens if you've got more than 3a of loads running WHILE you are charging?
Well, the amp flow never does drop below 3a and the doofy charger never does drop out of absorb mode.
And your battery ends up severely overcharged.

Iota chargers overcome this problem by setting a timer on the absorb stage. Iotas will drop out of absorb after 8 hours regardless if the amp flow is still high.

Samlex chargers overcome the problem by having a dip switch which sets the charger to 2-stage operation and omits the absorb stage entirely. Samlex calls this, "UPS mode".

This charger in the .pdf *might* have some way to overcome the problem. That's not shown in the linked .pdf which is just a product brochure, but it might be mentioned in the product manual.

 

[teotwaki]

(Anyone else notice that the truck in that first pic in the .pdf looks like a modern version of Casa Azul?)

Yea, that's a typical DC-DC 3-stage charger.

It doesn't "switch the alternator's output from the primary to the secondary" as you described.

What it does is draw power from the primary bus at whatever voltage and then step it up to 14.4v and feed it out as a 3-stage charge to the secondary bus.

The issue with DC-DC chargers is making sure that the charger doesn't draw down the primary too far. Some DC-DC chargers use voltage sensing, and when the primary drops to say 13.5v it stops sucking power from the primary.

This charger handles the issue by being switched on via the ignition switch.

Now, this charger does have an obvious problem that I see right off...this is a well-known issue with 3-stage chargers...

The problem is the absorb stage. If you look at the last page of that .pdf under the section called Charge Control, you see that it holds the absorb stage until the current flow drops below 3 amps.

The problem is this:

What happens if you've got more than 3a of loads running WHILE you are charging?
Well, the amp flow never does drop below 3a and the doofy charger never does drop out of absorb mode.
And your battery ends up severely overcharged.

Iota chargers overcome this problem by setting a timer on the absorb stage. Iotas will drop out of absorb after 8 hours regardless if the amp flow is still high.

Samlex chargers overcome the problem by having a dip switch which sets the charger to 2-stage operation and omits the absorb stage entirely. Samlex calls this, "UPS mode".

This charger in the .pdf *might* have some way to overcome the problem. That's not shown in the linked .pdf which is just a product brochure, but it might be mentioned in the product manual.

"Typical" DC-DC 3-stage charger? Who else makes them? Iota and Samlex are both AC powered from what I saw but maybe I missed a particular model?.

The one thing you put in quotes is something I never said and a lot of other things were alluded to me but aren't close. My wording might have not been great but it was not atrocious either. Please quote me and it will be easier to follow your replies

 

[Michael]

Here is another alternative. The CTEK 250s is a bit pricey, but has some nice features. If you run a solar system in your vehicle, it also has a built-in MPPT solar controller. My observations so far is that the charging voltage, at least on the meters I have, is a bit above 14.4VDC.

Comments welcome dwh! Thanks again for the great tutorial on my electrical system. This thread is actually getting useful, in addition to being entertaining

Here is a link to the CTEK 250S user manual.

 

[teotwaki]

Here is another alternative. The CTEK 250s is a bit pricey, but has some nice features. If you run a solar system in your vehicle, it also has a built-in MPPT solar controller. My observations so far is that the charging voltage, at least on the meters I have, is a bit above 14.4VDC.

Comments welcome dwh! Thanks again for the great tutorial on my electrical system. This thread is actually getting useful, in addition to being entertaining

Here is a link to the CTEK 250S user manual.

Thanks Michael! Now we have two DC-DC style chargers. :sombrero: I'll have to add that info to the Expo SOlar FAQ

When I shopped for a battery maintainer for my trailer I looked at CTEKs but bought a different brand in the end. I'm not sure I ever saw the 250S or simply ignored it. With the MPPT solar function the unit offers a lot to Overlanders but it appears that you have to have at least 80 watts worth of panel for the CTEK to use that source. There is conflicting info on that. It might be new vs. old software revisions.

CTEK manuals are not that straightforward. It seems that a lot of folks in Oz use them and discuss them on forums. I found this info:

"CHARGING PROGRAM D250S DUAL
The charger starts charging the target battery when the supply voltage exceeds 13.1V for 5 sec (engine on).
The charger stops charging the target battery when the supply voltage drops below 12.8V for 10 sec (engine off)."


EDIT: Michael, did you install a 250S Dual?

 

[dwh]

"Typical" DC-DC 3-stage charger? Who else makes them? Iota and Samlex are both AC powered from what I saw but maybe I missed a particular model?.

Sterling Power Products:
http://sterling-power-usa.com/sterlingpowerusabatterytobatterycharger.aspx

Powerstream:
http://www.powerstream.com/DCC.htm

Promariner:
http://www.pmariner.com/productFeature.php?ProductNum=05504

Chargetek:
http://www.chargeteck.com/products/dc-input-battery-charger/ckv/

Pretty sure Analytic Systems makes them too, but I can't connect to their web site right now. Here's one of their 2-stage units:
http://www.wmjmarine.com/bcd305-12-12.html


No doubt a few others I've forgotten...


EDIT: Oh yea, almost forgot to mention that Sterling also makes multi-stage voltage regulators which turn a normal alternator setup into a (temperature compensated!) multi-stage charging system (not for alternators with internal regulators...):
http://sterling-power-usa.com/advancedregulators.aspx

The one thing you put in quotes is something I never said and a lot of other things were alluded to me but aren't close. My wording might have not been great but it was not atrocious either. Please quote me and it will be easier to follow your replies

There are intelligent solenoids out there that first ensure the primary battery is charged and then switch the alternator's output to the second battery. In an earlier post I pointed to a DC-to-DC battery charger that eliminated the need for solenoids and effectively isolated the two batteries from the alternator and each battery can get the charge that it needs, independent of the other's needs.

Okay, my bad. you didn't say it about DC-DC chargers, you said it about solenoids. It wasn't correct in either case - neither one switches the alternator's output.

Also, your comment above about the DC-DC charger is incorrect. The primary battery is not isolated from the alternator. The DC-DC charger draws its input from the primary bus, which is getting its power from the alternator. As the DC-DC charger draws down the voltage of the primary bus, the alternator fires up to replenish it.

Ergo, the secondary bus (and battery) is *dependant* on the primary bus (and battery), not *INdependant* of it.

 

[dwh]

Iota and Samlex are both AC powered from what I saw but maybe I missed a particular model?.

Also, I wasn't suggesting Iota or Samlex as alternative DC-DC chargers.

I was using them to illustrate two different methods of dealing with the "loads running while charging can cause a 3-stage charger to get stuck in absorb mode" problem.

 

[Michael]

Keep this good info coming guys!

teotwaki: Yes, I recently installed a CTEK 250s Dual DC/DC charger in my 2006 Tacoma. I was using an automatic charge relay (Blue Sea Systems 7610 ACR) to isolate/connect the starter/service batteries in my system. It did a great job managing my aux power system, but I found that my secondary battery wasn't staying healthy as evidenced by decreasing maximum charge level. I use an Optima yellow top D-31T as my aux battery and have 'abused' it frequently -- unintentionally down to 8.5VDC on one occasion. :snorkel: I routinely draw it down to 11.5VDC during the night when camping (I use a CPAP and ham radio at night) and I'm sure that, plus the deep draw down episode, has reduced the life of my battery. To offset my abusive behavior, I've been in the habit of deep charging my Optima between trips with a "smart charger" and it seems to be hanging in there just fine (12.8VDC resting charge with satisfactory discharge profile) over the last 2+ years.

Recently, the generosity of a fellow expeditioner (currently in Belize driving a Chevy Astro van!) allowed me to try out the CTEK 250s Dual DC/DC charger. After considerable research I decided to give it a try, primarily because it would give my aux battery a deep charge using a DC/DC "smart charger" immediately after deep discharge. My typical journeying is to camp in a different place each night so there is usually about 6-8 hours of driving between campsites. Regarding the built-in MPPT controller, there is a lot of science, and even more opinion, out there about the value of MPPT controllers for small solar systems. I have an 85W solar panel (max 4.95A), which is probably on the ragged edge of getting any benefit from the MPPT type controller over a less expensive PWM controller. My experience is that it does have some benefit for me (YMMV), based on observations of performance late in the day or under cloudy conditions. Based on what I'm seeing however, I wouldn't pursue the MPPT over a PWM as it probably isn't worth the additional cost for the MPPT for my size system.

The 250s charge voltage is temperature compensated and I simply taped the sensor to my aux battery near the positive terminal. Another interesting feature of the 250s, although it may not be unique, is that you can use the solar panel at the same time as the alternator (on an RV perhaps?). Also when using solar by itself, the 250s will charge the starter battery after the aux battery is fully charged. It does isolate the batteries at the voltages you mentioned and yes, the way the Swedes wrote the manual leaves something to be desired.

I notice that Optima is now selling (and presumably recommending the use of) CTEK chargers, but the 250s Dual is not on their list. I'm not sure if that reflects its performance or just the fact that the 250s is relatively new. A side benefit of the 250s, and I presume the rest of the DC/DC chargers, is that the wiring size is less critical if your battery is located some distance from the alternator (mine is in my camper shell). The 250s boosts whatever voltage it receives up to 14.4VDC (I'm seeing about 14.6, which is a bit high IMHO) so the voltage drop in the bus connecting your alternator to the aux battery is less critical. CTEK provides guidance regarding minimum wire size for various distances from the alternator to the aux battery. dwh has discussed the issue of selecting the correct wire gauge in depth in other posts.

So far, the CTEK 250s is doing what I expected and what it advertised. The only performance issue I'm watching closely is whether it has the potential to overcharge my AGM battery from the slightly higher voltages I'm seeing. I also hadn't considered the fact that other aux power loads on the charging bus may prolong the absorption phase of charging -- thanks for bringing that out.

Optima Jim: Any comments on using the CTEK 250s Dual with Optima Yellow Tops?

 

[dwh]

(I'm seeing about 14.6, which is a bit high IMHO)

It's within the Optima guidelines for Yellow Tops. Personally, I tend to agree with HandyBob that most battery specs are conservative. I wouldn't worry about it for the Yellow Top, but I might worry about pumping the engine start battery (depending on what engine battery you've got) up that high if the charger switches to charging that battery once the aux is charged.


http://www.optimabatteries.com/product_support/charging.php

Alternator:
13.65 to 15.0 volts, no amperage limit.
Battery Charger:
13.8 to 15.0 volts, 10 amps maximum, 6-12 hours approximate.
Cyclic Applications:
14.7 volts, no current limit as long as battery temperature remains below 125°F (51.7°C). When current falls below 1 amp, finish with 2 amp constant current for 1 hour.
Rapid Recharge:
Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.
Float Charge:
13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).