Optima Battery Problems

[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/PDF...ry-Charger.pdf

[teotwaki]

This is a good one for switching the alternator between batteries...
Dualbattery3.jpg

[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/PDF...ry-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. 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/sterli...rycharger.aspx

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

Promariner:
http://www.pmariner.com/productFeatu...oductNum=05504

Chargetek:
http://www.chargeteck.com/products/d...y-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. 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/produ...t/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).