Standby AGM Bank Charger Recommendations

[Soulearner]

Hello,
My wife has medical needs which require electricity; wheelchair, ventilator, diet, much more.
I have 4 100W panels in storage and will be acquiring 4 200W panels for a separate system as $ allow. I have found 2 decent EPever charge controllers yet to buy. The systems will be deployed when needed.
I have 6 CSB HRL12540 FR AGM batteries and will be likely buy at least 2 more. Two batteries are floating on a Epic Pwrgate @ 13.7V - which from what I've learned is correct (they rest @ 12.9). The remaining 4 (or more) need to be kept on a charger/maintainer but I am having a lot of trouble finding a proper and affordable charger for this standby use. I sure could use some help.

[SunEagle]

With 800 watts you are going to need at least a 60amp MPPT CC or you might as well go with an 80 amp if you need to add more panel wattage.

Affordable and Quality do not belong in the same sentence when dealing with solar equipment.

If it is important to you than go with a quality CC made by Outback or Midnite or even Blue Sky.

[Soulearner]

Thank you SunEagle.
I can not give what I do not have, therefore quality must be the greater of the compromise.
The 2nd panel system can be downsized to 600W and still meet our needs, so a 40A controller will do. I see Schneider has an affordable, well-regarded 40A unit - But is a PWM. MPPT is supposed the be the preferred choice, the cost of which puts me back to foreign-sourced units.
My current need is for a charger to maintain the battery bank in standby until the system is deployed, and the best compromise I can find is an Iota DLS-30-X with an IQ4.

[SunEagle]

Thank you SunEagle.
I can not give what I do not have, therefore quality must be the greater of the compromise.
The 2nd panel system can be downsized to 600W and still meet our needs, so a 40A controller will do. I see Schneider has an affordable, well-regarded 40A unit - But is a PWM. MPPT is supposed the be the preferred choice, the cost of which puts me back to foreign-sourced units.
My current need is for a charger to maintain the battery bank in standby until the system is deployed, and the best compromise I can find is an Iota DLS-30-X with an IQ4.

The IOTA is a great battery charger. You see them in a lot of large RV's like mine.

I understand a quality MPPT CC is expensive but in the long run using a PWM actually reduces the amount of charging wattage by 1/3. So you end up getting more panels to compensate. That usually means more money for panels and wiring and combiner box where you can wire more panels in series to the MPPT.

A quick rule of thumb for MPPT is to divide the panel wattage by the battery voltage to get the amp rating. For a PWM you look at the total panel amps to size your CC.

The choice is yours to make but I try to convince people that going with an MPPT is better in the long run.

[Soulearner]

The IOTA is a great battery charger. You see them in a lot of large RV's like mine.

Thank you! I am on the right path.

A quick rule of thumb for MPPT is to divide the panel wattage by the battery voltage to get the amp rating. For a PWM you look at the total panel amps to size your CC.

...and thanks again; I have seen this but not given the rule sufficient weight. This is a good answer to the unbidden "why".

[PNjunction]

If you are dealing with wheelchairs, and how to properly power them, you'll find you are getting burned big time with those CSB's - designed mainly for UPS use, not wheelchairs.

As much as I respect the knowledge on this forum, I sincerely have to point you to those who actually LIVE in them. The forums of many topics, but the first one I emplore you to read is this one regarding lead-acid for wheelchairs:

http://www.wheelchairdriver.com/board/viewtopic.php?f=2&t=3609

Nearly *everyone* gets this wrong, and indicator being the UPS style CSB's agm's you want to use , which are totally inappropriate, a total rip-off for this application, and ultimately unsatisfying for the wheelchair user.

In addition to battery advice, the warning about how most chair-users are killing the batteries with poor infrastructure, not enough time to actually finish a charge overnight etc ..

Basically pay heed to Op: Burgerman. He lives it daily and can set you straight. If you want a Sunking-like no-bull experience about wheelchairs and charging, this guy is your man.

[PNjunction]

**SPOILER** alert re wheelchairs:

What you'll find at wheelchair-driver is that ultimately in regards to 'chairs, there are very few decent agm's, and only one or two gel's worth it.

The key issue is to shoot for the lowest internal impedance - to enable one to not only have a good chair experience, but also the ability to HAMMER them with a recharge - as fast as possible to get enough time in for at least 8-12 hours of FLOAT to get that last 1-percent of charge in (which takes long time no matter what) - otherwise you are going to "walk down" the agm capacity due to sulfation. There's no avoiding it - just like with solar if you are cycling daily - you'll kill them fast if you don't get enough charge in.

The issue that Sunking mentions about bulk-absorb-float , or failing that at least an 8-12 hour lower voltage float AFTER absorb has completed is key with agm's. And even gel's BUT you have to be very careful with those!

24-volt wiring and DIY chargers to replace those funky chair chargers are discussed. Things like not being able to push more than 12 amps through the typical audio-XLR charging jacks and more are discussed along with totally unrealistic "gas gauges" and the like are also revealed.

Although these guys have moved on to using their own DIY LifeP04 banks, lead-acid concerns come up from time to time. Expect recommendations to use Odyssey AGM's, but of course do what you like. Burgerman has lived this life after an accident and is a respected engineer.

The *LIE* about the difference between GEL and AGM CV voltages is also discussed heavily - driven by marketing to make chargers the same for gel and agm (which is marketing BULL) is also revealed.

I just wanted to make mention of this, since solar backup and wheelchair usage, while having some commonality in regards to batteries and charging, has a slightly different no-bull engineering aspect from those that have their butts literally sitting on top of these things every single day.