I wonder whether any inverters (hybrid ideally) support 2 separate battery types/sources, my thinking here is that one battery string could be made up of pretty pricey LiTiO cells than can cater for manyC discharge and charge rates (many seems to be anywhere from 5 to 10) but only give you 40Ah and the 2nd battery string being more normal LiFePO4's that you restrict to C/2.

The LiTiO's seem to have a claimed lifecycle of 10000 or more cycles and for short term high energy supply would be perfect whereas the LiFePO4's not being pushed would have a longer life as well.

I guess this would need 2 separate integrated inverters and 2 separate integrated charge circuits all controlled by the controller of this doubly hybrid inverter...

LiTiO ? Never heard of that abbreviation, is it something new?

Do you perhaps mean Lithium Titanate (LTO)?

Edited March 8, 20215 yr by YellowTapemeasure

Also referred to as LTO, I think they've been around for a wee while, mainly on scooters and things, methinks, 2.3V or 2.4V nominal, so would need a somewhat larger quantity in series to make the requisite voltage battery, the energy density is lower than LiFePO4, but can, by all accounts handle a lot larger charge and discharge currents, relative to their capacity and apparently, many more 1000's of cycles as well.

11 minutes ago, Kalahari Meerkat said:

Also referred to as LTO, I think they've been around for a wee while, mainly on scooters and things, methinks, 2.3V or 2.4V nominal, so would need a somewhat larger quantity in series to make the requisite voltage battery, the energy density is lower than LiFePO4, but can, by all accounts handle a lot larger charge and discharge currents, relative to their capacity and apparently, many more 1000's of cycles as well.

Cool, OK. Zenaji make one, at 22000 cycles it's quite a beastie, and it's in the Aussie tests as well: https://zenaji.com/aeon-battery/

I guess that you would want the capability to upgrade seamlessly from LiFePO4? Or what other advantage would you see in an inverter handling two separate battery types?

Well, not needing excessive capacity on the one input, for long term low-ish power draw, where the second input will take up the slack when someone switches on a large consumer temporarily, that would, under normal circumstances is the possibility of the battery's BMS disconnecting, since the draw, now, exceeds the battery spec.

Lets assume its night, your draw is around 1.5kW in the house with a battery bank that's specced to allow 2kW draw, someone wants to heat up something in the microwave, which draws 1.2kW, ok, heating up you set it to 30% power, but what this means is (depending on the model) 6 seconds on (drawing 1.2kW) and 14 seconds (just making up numbers here) off, drawing very little (light, turntable, if it has one, timer & ancillary electronics, maybe 20W?) and then 6 seconds on again... rinse/repeat, basically if the battery gets hit with 2.7kW even though its spec is 2kW draw allowed, the BMS will likely shut down your house for you, assuming things are not grid tied... if you are grid tied, you're obviously laughing and don't care, but some of us and  more to come, will not be grid tied, be it that Eskom don't want your business, yay, or that they want close to 100kZAR's to connect you up in the 1st place with a prepaid meter and thus amount is better spent on solar gear...

Yes it is possible. I do not know of any like this available at the moment, though.

There are a number of inverters that work like this:

Battery -> boost -> HV DC bus

Panels -> boost/buck-boost/etc -> HV DC bus

and then from the HV DC bus -> AC 50Hz

So now you just need an extra battery <-> HV DC bus for all excess loads.

(The battery will be either bidir or also have a buck from HV DC -> battery, there are other simplifications as well.)

Overall it adds a lot of complexity for installers and will be a nightmare dealing with complaints etc. But certainly possible technically.