Temp-compensating charger: DP Paramode?

[booster]

I think you passed the test!

As far as I know, the Onan 2800s don't come with a battery or charger, I know ours didn't and I haven't seen any that did. Normally, it would only have a single 12v wire to it for the starter, ours was 10ga.

You also have a battery wire, obviously, and I would guess the rest is taken care of in the Magnetek, both charging and 12v distribution.

Where you want to wind up is with the Magnetek charging section gone and replaced by the Blue Sea, with AC input just moved, and the output of bank two going to the Magnetek distribution box input that used to come from the charging section of the Magnetek. Bank one of the Blue Sea would go to the batteries only. Ignore the relay for now as it will be easy once the rest is clear.

Unless there is other power pulled off that doesn't come from the Magnetek distribution section, I think that will be it. Of course, fuses, wire size changes and such may be needed, but you won't know what until you get into it.

[Crank]

That's what I wanted to hear!

You have evidently set me up with the best solution to optimize use of my batteries, and given me a clear understanding of the basic installation. It has been quite a learning experience. Thank you, Booster!!!

As you mention, some refinements can come later. (But I'm short on technical knowledge in this field )

The project is going to be a lot of work, mainly because of the adaptations I must make to accommodate the 2nd battery, for which the RoadTrek was not designed. Fortunately, the AGM batteries do not need to be in sealed, ventilated compartments, which helps a lot.

I can safely go ahead and order the major equipment now, knowing the project is do-able and is expected to yield the desired results.

[gregmchugh]

While many people have been known to not do so, AGM batteries should be in an area that does get ventilation, not a completely sealed space. They can outgas hydrogen on occasion so there is some risk if there is no ventilation.

[markopolo]

This has been an interesting topic. I haven't been too interested in temperature compensation in the past. I think that has somewhat to do with the added cost to get that feature and more that I live in a cooler temperature place. I don't use the RV in winter temperatures.

Just for fun I checked the voltage on a small 10lb AGM at 63F (according to probe). It had been sitting on a shelf for a while and it measured 12.57V. I moved it outside to below freezing temperatures for 6 hours then measured the voltage again. It had dropped to 12.53V. The last measurement was back inside at 70F after 6 hours and the voltage was 12.58V.

I decided to buy one of the yellow 15A Samlex chargers and to use it to maintain a bunch of batteries in my cool-ish basement. It's main purpose will be to maintain 108Ah of AGM's that will be the power for a UPS setup with PSW inverter and auto transfer switch.

It can charge 3 banks so I'll use some Anderson connectors to attach other batteries like a HD starting battery that is a spare. One nice feature is that it can be locked in 13.5V mode so a load doesn't trigger it to 14V or 14.4V mode. Because of it's relatively low amp output, transition from bulk to float will occur when the amps in drop to 1.5 or 2.0 amps or so.

I read on a forum (another board) post that the unit does have temperature compensation but it does not use a probe. That means the batteries would need to be in the same environment as the charger. 15A shouldn't heat a large bank up much.

I think it could actually work as a charger in my van. The amp output is low but so are my DC loads when parked & plugged in. Also, my setup permits maybe as much as 90A from the alternator to the house bank so I can't imagine arriving at a plug in site with low batteries after any reasonable drive. My AGM's are in the coach so the temp compensation should also work. It's just a thought as the PD unit seems to be working great so I have no plans to change it.

It will be fun playing with the Samlex. I'll report back on voltages seen in constant current mode and also on any voltage variations do to temperature etc..

[booster]

From the reading I did, I think it said that the theoretical correction is 4mv per degree C per cell or .024v/*C for a 12v battery. For 10*C (18*F) that gives .24v of change in charge voltage, which is really quite a lot when you look at past discussions of charge accuracy wanted. I would guess we get that much variation every day we camp, and most days nearer double that much, so close to .5v change needed. I was kind of surprised at that it would be that much in just everyday life. I would guess that the risks are more on the hot side for damage and the cold side for undercharge issues.

Magnum uses .5mv instead of the .4mv, and I assume they do this because the sensor is on a battery connection. I would guess that would cause a delayed reaction to temp change, especially when heating up fairly quickly during charging, so they want to cover that at the expense of other accuracy.

Since we go by amps to end the charging cycle and the amps settings are not temperature compensated, the voltage gets to be quite important at the end of charging. Too low of voltage for the temp and it will end too soon, and too high a voltage and it may never transition to float (very bad). Watching the amps going in at float on ours in the garage, we see almost no change with a 20*F temp swing and the temp comp on, so probably good. We do see the .3v increase in charge voltage correction.

[Crank]

Thank you for mentioning the supposed risk Greg. (My compartment does have small vents to the exterior.) Manufacturers print CYA warnings, because accidents can happen under extreme conditions. IMO we overreact to them: no-one is going to be blown up or suffocated by H2 under normal use and controlled charging.

"Even under severe overcharge conditions, hydrogen emission of AGM batteries is far below the 4% maximum specified for aircraft and enclosed spaces." absorbed glass mat (AGM) battery (Sorry I can't provide a primary reference). The Lifeline Technical Manual observes that the small amount of H2 released dissipates quickly, but that AGMs should not be enclosed in a sealed container. As of April 2014, no case of Lifeline thermal runaway is known.

I would greatly appreciate it if anyone who wishes to pursue this side issue or relate battery horror stories begin a new thread: please post a link here.

I would like this highly informative thread, which I began, to remain on topic: choice of batteries, chargers and installation matters, mainly in Class B campers where space, and so efficiency, is a premium, for the benefit of future readers.

[briancummings]

Here's a link to a guys blog I recommend to people who want to boondock. I have tested every single reading he talks about in regards to solar panels etc. and he is bang on. I used his advice when installing panels and batteries on my 1986 Okanagan Econoline 250 and have had great success, camped 3 weeks last summer and never plugged in once and never got below 66% battery capacity still left. https://handybobsolar.wordpress.com/ab

[booster]

As long as I had found the parts in my "extras" box to convert a Blue Sea charger to ignore the van loads and give true ending amp charging, and had some time in the garage while doing organizing and such, I decided to put together how I would envision an easy to install kit would be done. I had promised Blue Sea I would get that information after testing, but have been lax on that, so this makes it so they can see it also.

It is very simple, and not very expensive. A relay and a time delay is all that it takes. What I put together has a couple of auto reset breakers on it also, as you need them anyway and they were laying around.



Just 4 connections to make. One to the batteries or bank one of the charger (same connection). One to another bank on the charger. They both connect to the breakers. One connection to the distribution box or coach 12v power input that used to go to the batteries, from the relay output. And a ground from the relay coil.



When on batteries, everything is just like before adding anything. Power to the coach from the batteries though the normally closed relay contacts. When the charger comes on, there is a delay before anything happens, as the safety checks in the charger didn't like the load on a bank without a battery when it checked for shorts. Then the relay activates and shuts off the batteries to the coach and replaces it with power from the charger's other bank. This makes the programmed transition to float amp setting for the bank the batteries are on as accurate as a shunt based setup. The coach power bank seems to reference the battery voltage in the charger so it holds well. You set that transition amps high so it goes to prefloat right away.

Parts in one off quantities were less than $40 for the relay and time delay. If you get the 40 amp charger without the remote (the charger itself has a good display, the remote is just LEDs), it can be under $510, so the whole thing for about $550. The is close to 1/2 the next available option, which adds an inverter, but can't do two banks accurately like the Blue Sea with the add on.

In the end you have the ability to charge two banks of batteries accurately (coach and starter usually), separate power from the third bank to the coach, amp controlled float transitions, temp compensation (only one bank, though), all the charge voltages settable (same for all banks), and programmable current and voltage for equalizing or conditioning batteries.

[Crank]

This is really helpful, Booster, and most timely. I finally got my electrical layout and cable routing figured out, made some new space for battery #2 and was (and still am) planning on ordering components tomorrow.

Thanks for illustrating the lay-out for the P12 enhancement: there were a couple of things I did not understand: you now make it all very clear.

Technically, and functionally, this is a big step forward, finally assuring a full battery charge and an accurate indication of it, from a moderately priced, full function charger. Congratulations!

I could be one of the first to benefit from and field test this modification. I'll pass along anything of interest I notice, and make any specific observations you request Booster, when I am up and running with a Trimetric installed.

This thread has now really paid off big time, thanks to your continual engagement with it and contributions by others! It and its predecessor at:
http://www.classbforum.com/forums/f8/sizing-coach-battery-for-my-style-of-b-use- have been a real education on batteries and how to charge them properly by methods other than solar, and are helpful to electronic noobs, those who have not considered whether their charging system is all it should be, and even for those who are pretty well-informed.

I hope Blue Sea implements this improvement after they have tested it to their satisfaction.

Crank

[booster]

I hope Blue Sea considers making a kit themselves, too, as they said they have had quite a few questions about how to get around the load issue. I am sure they will have better access to components so they could probably do it better and cheaper. If they could find a good time delay relay, they would be down to one part only needed.

Let me know when you want this one and I will get it in the mail to you.

[Crank]

Woo-Hoo, here I come: The Blue Sea P12 40amp with Booster mod!

I think this is really going to be good: maximum battery performance and no charger-killed ones.

It is going to be a while before I get it and new batteries installed, because of other priorities. But I hope I will have something to report early in April.


Briancummings, thanks for the Solar link. While we have deliberately focused on batteries and charging them here (some of us don't have solar for one reason or another), solar has an important if not essential role in extended boondocking. I'm glad your experience was a good one.

In class Bs, boondocking duration is limited primarily by freshwater and waste tank capacity, and a battery/generator system will serve for that limited time. In my case, I inherited a generator with a used Roadtrek, so never considered the extra expense of adding solar worthwhile. Solar or not, one must have an optimal charging/storage system first: often lacking in older Bs and even in cheaper modern RVs.

[markopolo]

Originally Posted by markopolo

......................

I decided to buy one of the yellow 15A Samlex chargers and to use it to maintain a bunch of batteries in my cool-ish basement. It's main purpose will be to maintain 108Ah of AGM's that will be the power for a UPS setup with PSW inverter and auto transfer switch.

It can charge 3 banks so I'll use some Anderson connectors to attach other batteries like a HD starting battery that is a spare. One nice feature is that it can be locked in 13.5V mode so a load doesn't trigger it to 14V or 14.4V mode. Because of it's relatively low amp output, transition from bulk to float will occur when the amps in drop to 1.5 or 2.0 amps or so.

I read on a forum (another board) post that the unit does have temperature compensation but it does not use a probe. That means the batteries would need to be in the same environment as the charger. 15A shouldn't heat a large bank up much.

..............................

Just an update because I previously mention the yellow Samlex 15A charger. There is no temperature compensation that I have been able to detect. It does transition from bulk to float at approx 1.5 amps confirmed by ammeter in so you're pretty well assured to end up with fully charged batteries. Float is 13.5V as stated in the manual.

[booster]

Originally Posted by markopolo

Just an update because I previously mention the yellow Samlex 15A charger. There is no temperature compensation that I have been able to detect. It does transition from bulk to float at approx 1.5 amps confirmed by ammeter in so you're pretty well assured to end up with fully charged batteries. Float is 13.5V as stated in the manual.

It does seem to look like they are starting to switch over to 10% of charger capacity to transition on a lot of the new designed chargers. I don't know if that is better than timers or not The addition of some sort of adjustability for the % would go a long ways to making the next generation of chargers a whole lot better.

At 1.5 amps, that charger should be perfect for topping yours off without having to monitor them.

[Crank]

Marco, does your Samlex allow you to program each battery bank independently, so that different battery chemistries can be used on different banks? The Blue Sea does not, which precludes if from charging an AGM bank and also a wet cell cranking battery. Well, maybe it would be OK to do it in an occasional emergency: after all, one does not need a fully charged battery to crank.

Crank (Finally!)

[markopolo]

No. It has the same voltage under load on all three charger output terminals and they share the rated 15A output. The transition from 14.4V bulk to 13.5V float occurs when the amp output drops to 1.5A or less. Batteries at widely different state of charge could result in one bank being overcharged. I'm using it to maintain already charged batteries.

I have a timer based Progressive Dynamics unit and this ending amps based Samlex unit (used in separate applications).

Combining timer and ending amp functions in one unit would be a step up from both of the units I have.

[booster]

True multibank chargers that allow separate voltages on the banks are very, very, rare and extraordinarily expensive. Most manufacturers will recommend buying 3 smaller chargers instead

We did run our Blue Sea on three banks of batteries, one of which was the starting battery and which would ideally want different parameters.

It appears that that if the odd battery is the normal "starting" type battery, and not a deep cycle, they are actually quite durable and resistant to varying charging conditions. I think this is because the new vehicles have upped the charge voltages off the alternators so high that the batteries had to get tougher.

I don't think you would have any issues in hooking up the unused bank on the Blue Sea to the starting battery from a durability standpoint.

If you did decide to do it, and wanted to be also able to charge the AGM coach batteries off the alternator, you would have to add an automatic charge control relay to the circuit, though.