Charging upgrades-good for all?

[booster]

The upgrades to our charging system, now done and working very well for us, do what they were intended to do, but would some, or all of these be necessary, or even good for others? I think that is a very valid question, and the answer IMO would be very good for some, horrible idea for others, based on how you use your B and how "hands off" you want it to be.

Who would benefit--If you are off grid a bunch, and don't have enough battery capacity to stay as long as you would like. If you have chronically undercharged batteries do to a poor charger, or rarely having shore power or long drives, that are killing your batteries early. If you want "free" extra battery capacity that you can gain by getting your existing batteries totally full, and also making the batteries last longer. Those with compressor frigs, which are getting more common, might be in more need.

What we gained--Our batteries were only getting 80-90% full on shore power off the Tripplite converter in our Roadtrek. We have 375AH of batteries, which is quite a bit more than the 220AH most Roadtreks have, which gives us about 185AH usable at 50% discharge, assuming they are totally full when starting. If they are at only at 80% SOC, we lose 40% of the usable AH, so we would only have 111AH usable. The batteries will also lose capacity over time when only charged to that level.

What we lost--We need to make sure that we don't overcharge the batteries, which gets to be very possible when all the parts are trying to get them 100% full. You stand the chance of failing batteries quickly by overcharging, where undercharging is a slow death. Automating all three charging systems, shore, solar, alternator, is not easy, and was beyond the complexity we wanted to even wanted to try. Maybe the very high end stuff from Outback and Magnum could do the automation, but I could find no information on how they control things, so I can't say one way or the other, plus we didn't have $5000 to put into this system.

As it appears to me, most of the standard components are not optimized to fill batteries all the way, so there is a lot of window to prevent overcharging due to multiple systems that are in our B's. The risks are just lower for the manufacturers that way, so I think it is intentional.

The overcharging problems we encountered are certainly not dire, or unsolvable, as we think we have them taken care of, but the do require some operator intervention. We have a manual disconnect on the separator, so the alternator will not be putting 14.4 volts, while driving, on totally full batteries when we come off shore power or the solar has filled the batteries (switch on the dash). We have are in the process of installing a switch on the solar so we can switch between two charge profiles, one for normal fill up the batteries as far as possible, and one for float voltage only if we start with full batteries. If we are running fairly large 12v loads in the van when we are at the end of the charge cycle of the shore charger, we shut them off for 30 seconds to allow the charger to go to float based on ending charge current, otherwise it will stay in absorption until the timer runs out or the loads are no longer used (we can see the amperage on the Trimetric meter, so it is easy).

If you are willing to do the above, what we see as very minor, things, you can have full batteries at nearly every charge cycle and greatly increase your off grid capability. You should also be able to achieve better battery life. If not, no or lesser, improvements would be better for you. I will put that in another post after this one.

[booster]

Ignoring doing the complete upgrade that we did, here are things that could be done, and what issues I have seen related to them.

* Using the higher voltage of 14.7/14.8v that many wet cell manufacturers recommend instead of the 14.4v on most of the chargers. This will positively fill the batteries 100% and faster, but you absolutely need to have temperature corrected charger controlled by a temp sensor on the batteries. In our initial testing of our charger, without the temp sensor in place, we came way to close to thermal runaway, and it was only 70* F in the shop. You also need to have a charger that knows how long to charge the batteries in absorption, and fixed timers don't work well for that. Our charger ends the absorption based on the ending amps for the batteries, which works great as long as there are no extra loads or charge from other sources. Outback talks about using their battery monitor to decide when full, but don't say how they do it, and I think it would be very difficult to do. If I were going to upgrade a one bank converter only, and didn't want to spring for a Blue Sea, I would put in a Progressive dynamics and a Trimetric meter. The Progressive Dynamics is non temp controlled, so it would have to run at 14.4 volts, but it does go into absorption at every plug in (good) and you can manually take it to float when the batteries are full, or another absorption cycle if the batteries aren't full. You would just have watch the Trimetric, and when you got to the ending amps for your batteries, push the button on the PD and take it to float. I think this is one of the best and easiest things folks can do to get full batteries, especially if the already are running a PD converter.

* Solar is great, but can over or undercharge pretty easy. If your solar is small compared to battery bank size, and more importantly, daily usage, you will be undercharged if you don't get plugged in or drive often enough. All you can do is make sure the solar is programmed to run all day to get the most you can out of it (ours was only set for a few hours from the factory). If your solar is big enough to consistently cover your usage, or if you are coming off shore power or driving with full batteries, it is very likely the batteries will see an overcharge. You get very limited in what you can do, because reducing overcharging by shortening the timers also reduces the charge time you might need when it is cloudy or shady. If you have a Morningstar, you can do the alternate program like we did, which looks to work very well with a single switch. You can also do the same thing as with PD converter and Trimetric, just watch the Trimetric and when you hit ending amps, shut off the solar.

* Alternator charging of the coach bank of batteries is needed, but not good on top of full batteries, and can make solar overcharging even worse, as it may allow the solar to go to a higher charge voltage (depending on settings). Putting in a manual disconnect is easy and cheap. You again can go by ending amps read on the Trimetric meter to know if you should disconnect the alternator due to full batteries.

As can be seen from the above stuff--the common thread is the Trimetric, or other battery monitor. It will allow you head off nearly all the issues you may have now, or find later, as it tells you what is going on. It is not all that accurate if you just use the AH or % full readouts for charging. Amps to the batteries will tell you much more IMO.