Mixing different types of batteries

jrcent · June 2019

I just got a midnight classic 150 and currently have 12v agm batteries on the 1st input . I want to start updating with new lead acid batteries . Place I got it from said that I can have 3 separate legs inputting with different types of batteries. Is this true? Normally you can't but this is supposed to be able to know the difference.

mcgivor · June 2019

Different types require different charging parameters, however if the type reference is regarding capacity but the same construction, AGM, flooded or GEL then it is possible to parrallel bu not necessarily desirable.

Different age mixing is not recommended because the battery's needs change as they age, therefore it's better to start with like batteries of equal capacity, avoiding parallel strings if possible or keeping them to a minimum no more than three.

So define type, legs and if you intend to mix new with old.

jrcent · June 2019

I currently have 8 atm 100 ah batteries in 24v configuration. They are about 5 years old.

I would like to go to lead acid 6v batteries.

I wanted to use both banks at the same time according to the shop I was talking with.

The classic 150 can control 3 separate bank of 24v batteries with each bank of different types of batteries at the same time?

Sounds like I should go with only the new bank and keep old bank a separate system.

BB. · June 2019

I am not quite sure I understand your question... I am guessing you are asking about 3 parallel strings of batteries (and each string possibly a different type/age/etc. of battery)?

In general, AGM (which are a form of lead acid battery) and Flooded Cell Deep Cycle Lead Acid batteries have different "ideal" charge settings (absorb, float, time on charge, etc.). And you just cannot put the different types of batteries in parallel and keep each of them "happy" with their own voltage/time setpoints.

And mixing different battery types (and ages) is usually even "worse" in series strings... FLA batteries are relatively tolerant of controlled over charging (equalize charging) used to bring all cells in a series string back to 100% full.

AGM batteries (and other chemistries) are not really good at "controlled" over charging. AGM batteries, it really reduces their life, and with Li Ion types, it can kill them pretty quickly.

If you had an emergency (as in a shortage of cash)--Folks have mixed parallel strings of AGM and FLA batteries... It can work... But it is not a good way to get maximum life out of your batteries.

-Bill

jrcent · June 2019

Yes mixing. I wouldn't do it normally but basically the shop trying to sell me stuff is "misinformed " about the equipment!

mcgivor · June 2019

The AGM batteries are probably near end of life at 5 years, 6V flooded lead acid golf cart batteries are probably the best value format due to supply and demand. They are generally longer lasting than AGM if correctly maintained, which involves checking electrolyte levels as well as monitoring specific gravity (SG) with a hydrometer.

There will be a learning curve but once understood it's quite simple, before installing though make sure to ask questions if you don't already know, there are some procedures to follow before actually using them, which if followed, will improve the performance over their lifetime.

jrcent · June 2019

Cost per ah is good enough to deal with the maintenance. I remember the days when that was all we had and keeping distilled water around. I've seen nema boxes blow up because they didn't vent.

Estragon · June 2019

I'm pretty sure a Classic 150 won't charge 3 different types of battery (with different charging regimes) at the same time. They'll charge lots of different types of batteries, but not simultaneously. To do so, they would need 3 separate outputs, each with independent charging parameters. AFAIK, they still just have the one output.

jrcent · June 2019

Thank you. I didn't really think so but electronics are always changing.

littleharbor2 · June 2019

Morningstar makes a small charge controller that will charge two separate batteries. AFAIK it's the only multi battery charge controller.

Image: https://us.v-cdn.net/6024911/uploads/editor/i4/mabsodh1awmb.jpg

mathias · June 2019

They are others. I found this :
https://sea-m.banggood.com/MPPT5025A-DUO-MPPT-25A-12V-Solar-Charge-Controller-With-LCD-Solar-Regulator-For-Solar-Panel-Charger-p-1334924.html?rmmds=search&&_APPDRAINAGE=1

No idea how good or bad it is, or if it's really mppt as claimed. I'm not affiliated with the seller.

Mat
(Please delete link if inappropriate)

Dave Angelini · June 2019

Just an FYI and not really for the OP.

Very large systems can have multiple battery banks, and/or different chemistries or different ages, each with it's own battery monitor.

Individual bank charge parameters are programmed in with modbus. A Schneider Sales engineer can do this for a fee and I think Outback can also.

mcgivor · June 2019

Dave Angelini said:

Just an FYI and not really for the OP.

Very large systems can have multiple battery banks, and/or different chemistries or different ages, each with it's own battery monitor.

Individual bank charge parameters are programmed in with modbus. A Schneider Sales engineer can do this for a fee and I think Outback can also.

Very interesting, multiple banks with different chemistries or ages all charged by a single controller each with its own battery monitor, are you sure this is possible ?

BB. · June 2019

Multiple "smaller systems" (battery+charger+inverter) all networked together in a single large system?

-Bill

Dave Angelini · June 2019

Bill, probably anything is possible if you can write the code. The problem with smaller systems is the network by itself is not smart enough without modbus commands for one network with multiple chemistries/invchg etc.

You can switch manually between inv/chargers, mppts, batt mons, and networks, which I do for some clients and here at home. I suppose there could be an IFTTT solution but I don't see any easy ones yet, short of hiring Schneider to do this. They love to bill engineering hours

The Gateway has a path to this but it is not done yet. They call it clusters and it is mainly for 3 phase. You can see their path evolving with the dual networks on gateway. In the past they would master slave comboxes but that was for systems a huge number of devices.

The big however is a small system needs someone to do the switching safely. The large microgrid system can afford or have the talent on site or pay to automate/monitor.

Estragon · June 2019

Not something I'm planning on anytime real soon, but I have wondered if a sort of stacked mixed system would make any sense.

In good spring/summer weather, my 48v bank typically doesn't cycle much below ~80-85% SOC. The 12v bank rarely goes below 90%. What I'm wondering is whether it would make any sense to have the first 15-20% or so discharge handled by a smaller lithium bank, and only cycle the L.A. bank in bad weather. I could probably do the modbus stuff, but not sure the benefit would outweigh the complications and potential for faults.

Dave Angelini · June 2019

Sounds like for you it would the opposite of KISS for you. I like the complete backup especially in wildfire season or in a stormy winter. It buys time for me to deal with power in a relaxed fashion. A comfort for my wife also if I get abducted by Aliens.

For many even a manual switch is too complicated/expensive. With the fairly high failure rate of LFP and NMC out of the home storage testing in Australia, it does make sense to have a LA ready to go if your situation warrants it.

jrcent · June 2019

I originally thinking of just being able to upgrade my battery and keep hold bank running till eol. Maybe have a separate inverter for each bank. Never thought it would be permanent.

Mixing different types of batteries

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