Multiple battery bank question.

[NJM]

Hi everyone i have a question for you. Can I hook up one tracer 4215BN CC  40amps on a 6x 320w  solar panels?. I have a plan to mount 6X 320w panels in parallel, then i think Ill use 3 charge controllers feeding 3 different battery bank 12  24  48v with 3 inverters and then put all the inverters and the charge controllers in automation. When one bank is charged, the other starts charging. But the problem if i will have a problem using the charge controllers with the higher amperage on input. Thank to all in advance. Njm

[Wolvenar]

For a start, it would be helpful to have a lot more details such as model numbers and specs of each device if you have them.

If you don't have them yet, can you supply more detail of your solar panels at least spec wise, with voltages and such relevant information.

[NJM]

Hi Wolvenar, thank you for the response, i made a draw of the system that i want to mount, i have already the 3 charge controllers, 3 power inverters, and some more devices, described on the picture.  I colleting some informations if my idea is resonable, or there is the better way to get the better rsults, my intention is puting the system working on shift,  8 hours which one, giving the battery banks a chance to recharge during the sun hours, with the premisse that i can add the batterys in case. I will apreciet e your comments, NJM

[welshman]

yes it will work, maybe you could explain why you want 3 battery banks, 1 with 12, 24 and 48 v?

is it just because you already have 3 charge controllers and want to use them?

or are you planning on using the 12,24 and 48 v on seperate inverters ?

have you considered just using one battery bank and tapping off the batteries the voltages you require?

[welshman]

Maybe this for better efficiency?
or even this?

[NJM]

Hi, thanks for your input. I have  3 charge controlers and 3  power inverters 1 -12v 1-24v 148v. I have a plan to use them 3 . With separeted baterry bank, sharing just the pannels. One question; if i tape the battery bank, 12,24,48v will not damage becouse the balancing.thanks.

[welshman]

Hi, thanks for your input. I have  3 charge controlers and 3  power inverters 1 -12v 1-24v 148v. I have a plan to use them 3 . With separeted baterry bank, sharing just the pannels. One question; if i tape the battery bank, 12,24,48v will not damage becouse the balancing.thanks.

i wouldn't worry about that at all. also, like i demonstrated in the second image that you can mix and match as you like, putting more in parallel will boost the amps, in other words time.

[Wolvenar]

Welshman doesn't this leave a bank that is never charged evenly, and some batteries constantly over/under charged.

[MadScientist267]

What wolv said.

That's recipe for balance nightmare that will kill the lead with a quickness.

[NJM]

Thank you  guys, build the 3 separed battery banks 12,24,48v is not a problem at all the. My main doubt is; if i can hook up 3  charge controllers on the same 6 solar panels string . Or this will damage the charge controlers?  Assuming the single CC will receve higher amperage then its capacity. Thanks.NJM

[MadScientist267]

NJM -

It likely won't "damage" anything... no... but you may find that they don't play nice together.

I had a somewhat related thing going on with some direct connections to part of my PV array, and it caused the classic (charge controller) MPPT algorithm to get confused and not load the panels properly. The end result of this was radically reduced overall system efficiency.

This isn't to say that *all* MPPT algos will get confused by interaction, as I was able to change to "legacy P&O" mode and counteract it somewhat. Ultimately tho, I disconnected the other load so that I could use the smarter algo for charging.

What you're facing there is what typically gets encountered with the so called "grown in place" phenomenon... normally encountered when the needs of the system demand more than available equipment in an existing nominal system voltage can provide. Battery voltage is one of those core system attributes that is part of defining the system itself. The dilemma of course is usually "well what do I do with all this extra equipment that's not compatible".

By all appearances, it looks like you're going in to all of this from scratch... My single piece of advice would be "simplify". If you're looking at loads that require things like inverters that need the 48V layout to be efficient, skip the 12 and 24 completely from the beginning.

Other than possibly a small auxiliary system that's more or less separate (or sometimes piggybacked after the main bank), the lower voltage stuff will just frustrate you down the road, and introduce extra points of failure. Neither of which are any good.

All that said, you might want to take a peek at this to get a better feel for why all this matters so much. It was written with the idea of people in mind such as yourself that are heading into the magic of renewable, in hopes of saving you from some of the mistakes that lurk in the shadows that sneak up on newcomers. 

Hope this helps, and welcome to the forum.

Steve

[welshman]

Welshman doesn't this leave a bank that is never charged evenly, and some batteries constantly over/under charged.

the system would always try to even out the charge, as the batteries get full their resistance drops. it would be just like taking a 90amp, 60 amp and two 30 amp batteries and putting them all in series. the 30 amps in reality dont die or overcharge in practice, this system is regular used in boats where space is an issue.

as the smaller capacity batteries  run down, the other batteries compensate, so a situation will occurs that while there is a draw on the total string of batteries, the smaller batteries are being charged by the larger. charging and discharing will occur simultanoeusly in the string.

what i would advise against is placing a flat battery in the string of fully charged batteries, that could be dangerous the currennts generated would be huge.

[lighthunter]

 would be just like taking a 90amp, 60 amp and two 30 amp batteries and putting them all in series...
as the smaller capacity batteries  run down, the other batteries compensate, so a situation will occurs that while there is a draw on the total string of batteries, the smaller batteries are being charged by the larger.

Hi Welshman, your description could work if batteries were in parallel (provided voltage ratings are same). But absolutely not in series.

In a series battery string with unequal amp hour sizes you will risk reverse voltage on the weakest/smallest battery during discharge as it will hit 0 volts when the others will be at rated volts. Not saying it isnt possible to do with monitoring / shutoff circuits added but certainly not a normal design. You would need special balance charging circuits as well such as are used in lithium charging.
When a battery is charged in series. <current is same in loop> therefore each battery in string recieves same number of pixies er electrons. The small AH battery will get full first and go overvolts/gas, positive grid corrode etc. While overall bank v has not risen enough to terminate charge.

The exact reason portable equipment manufacturers always specify in manuals, never mix battery types and always replace complete set of batteries together with new.

Not saying i havent ignored that a time or two in a pinch  but when it causes an electrolyte leak in the battery compartment and ruins my laser level I cant scream at energizer.

[MadScientist267]

Even subtle differences in cell capacity in a series string can have strong effects. In fact even just normal *temperature gradients* across a string lead to differences that have significant impact on balance.

As drawn in the schematics from Welshman, they would be staged for *severe* imbalance.

Imbalance kills.

It doesn't have to even be as extreme as lighthunter mentions, with cell reversals. It's more than just voltages and currents. Lower capacity cells (regardless of cause) run higher voltage during charge, lower voltage during discharge, and at a higher temperature during both because the C rate is higher, with higher impedance, which generates more heat. Hotter cells need a lower charging voltage, but because they're reduced capacity, they're seeing even *more* abuse. This isn't even to mention that a hotter cell will lose more water (which further changes it's characteristics), and that heat in general reduces life expectancy significantly because of accelerated reaction rates in the cell.

When you put all of this together, it forms a runaway process (both short term during that particular cycle, and long term over the life of the bank) that will do permanent damage to the lower capacity cells quickly.

It's hard enough to keep a matched set of equal capacity cells in balance with one another, and you'd be surprised at how little it actually takes to throw them significantly out of whack with one another.

Will they provide power in a mixed situation? For a while... But if you care about the longevity, they need to be as "perfect" for each other as every other cell in the bank, as much as possible.