Yea, too complex.
Some comments in general...
The alternator/voltage regulator is not going to do a multi-stage charge unless you use a multi-stage voltage regulator(*), such as from Sterling Power Products:
That unit can apparently be piggy-backed on to the factory voltage regulator - but if the factory regulator is internal to the alternator, may require an alternator shop to mod the alternator to add external connectors.
(*) But that's okay - unless you are actually draining your starting battery a significant amount on a regular basis (you really shouldn't do that), then you DON'T need a multi-stage charger for it anyway. If all you are using it for is starting, then the factory alternator/voltage regulator will maintain it just fine.
For simplicity and reliability, what I'd do is:
This for charging while driving:
I personally run a dumb solenoid split-charge relay setup in my own truck.
If you really must have multi-stage charging for the aux batteries while driving - and I can't object to that, it is after all a good thing (though not needed for the starting battery), then run a couple of multi-stage DC-DC chargers. There is an off-topic mini discussion of those here (post #203 - #208):
This for charging from the solar:
Use it for the two aux batteries. You don't really need solar for the starting battery unless you are doing something silly like actually draining it rather than just using it for starting.
The Duo should be plenty large enough at 25a, even with the second panel added. If for some reason it turns out that it's not big enough to handle the second PV module - then run one Duo for the 215w permanent panel, and a second Duo for the portable panel.
This for charging from shore power:
It can do up to 3 batteries at the same time, though only 30a shared between them. That's okay, the smaller batteries will reach full charge voltage pretty quickly, and then most all of the output current will be going to whichever battery is still low.
The only caveat, is that with the Samlex, if you charge two (or three) batteries at the same time, then you have to switch it into 2-stage mode instead of 3-stage mode. So it will bulk and then drop to float and omit the absorb stage.
Fine, no big deal - the solar can take care of the absorb when the sun comes out if you aren't driving, and the alternator can take care of it if you are.
The reason to use 2-stage, is that when charging two different batteries (i.e., not tied permanently into a full-time bank), one will be full before the other, and so by the time the lower battery is fully absorbed, the higher battery ends up overcharged. So you set the charger to 2-stage and then it runs the bulk stage until all three batteries reach 14.4v and then drops to float.
I've said it before, and I'll say it again "AGM Specific" is marketing BS. Almost all AGM batteries take the same charge routines and voltages as almost all FLA (flooded lead-acid). If you look at the manual for the SunSaver duo charge controller I just linked, and also look at the manual for the Samlex charger I just linked they both have switches to set them. The switch positions are:
What works for AGMs works for FLAs and vice versa. The only caveat to that, is that with an FLA, you can push it to a higher voltage (as recommended by HandyBob, and I concur with him on that), but you'll use a bit more water. You shouldn't do that with (most) AGMs - they might pop their seals.
But only a programmable charger, or one pre-programmed for that (such as an Iota with IQ/4 module) will push a battery that high anyway. The SunSaver Duo and the Samlex will both bulk the batteries up to 14.4v which is what is recommended for 99% of the AGM and FLA batteries on the market. (Though, the Duo is in fact programmable though the use of Morningstar's interface and software so you could use it to pump the battery higher if you wanted/needed to.)
And also, batteries of different make/model/type/age/religious faith/etc WILL play nice together if they are only tied DURING CHARGING. It is only when tied into a full-time bank (series or parallel) that they must be identical.
Well, any mix of AGMs and FLAs will play nice. GELs require special handling (lower bulk voltage) and should never be mixed with anything except other GELs.
Of course, that's true only as long as you are using either a constant voltage charging system (like an alternator/voltage regulator), or a 2-stage charger. 3-stage is only for single batteries, or multiple batteries tied into a permanent bank.
Okay, so that's my recommendation. But perhaps you've already decided how you're going to do it, and are just looking for someone to check over the schematic for gotchas.
That's okay. Lemme see...well...gee...it looks complicated. Kinda scary. So...um...what's this job pay anyway? Is there hazard pay?
Don't worry about getting more amps. Optima recommends 10a anyway, and their Optima branded charger only does 12. Some AGMs can handle ungodly amounts of charge current - such as Odysseys which are rated to handle an unreal (and likely impossible to achieve in the real world) C*4 charge rate - but most specify C/4 or less.
You can go crazy trying to engineer the most perfect system - but at the end of the day, you're still just dealing with a hundred pounds of lead, water and sulfuric acid. I.e., batteries are all limited lifetime junk. Focus on simplicity and reliability and build a system that is "good enough to get the job done".
Last edited by dwh; 07-05-2012 at 11:07 PM.
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