Figuring out what to install. Can't figure out what to do between these two options. Hoping to power lights, wifi, geyser, an AC, and one appliance (eg. microwave, airfryer, etc.) at a time

I'm a fan of the larger batteries, the only downside to the Deye 10.6kWh RW-G10.6 is that it is 0.5C. Naturally this is only an issue if the inverter is in off-grid mode with no PV, worst case scenario the inverter will 'trip' to remind you its only 0.5C. Hope that helps.

1 hour ago, MuneebK said:

Hoping to power lights, wifi, geyser, an AC, and one appliance (eg. microwave, airfryer, etc.) at a time

You will have to give us more info - e.g. do you plan to run the geyser and/or AC at night (i.e. from the battery)? For how long will you be running these power-hungry devices? What size element does your geyser have, and what is it's capacity (liters)? Also, are you planning on remaining connected to the grid, or do you plan to go off-grid in the future? For how long do you plan to be able to be "autonomous" (off grid due to power outage, cable theft, etc.)

I have 2 x 10.65kWh Sun-Batt (rebranded Eenovance) batteries connected to my 12kW Sunsynk inverter, and with these I can power my geyser for one hour from the batteries, and run my full normal household consumption for 2 consecutive days without grid power and cloudy sky, and still have enough battery capacity left for a third day without the geyser if I nurse my consumption - but our household is only my wife and I, and we can go without a lot of what most people would consider "necessary" consumption in an emergency... So, IMHO you would need at least 10kWh of battery capacity per 24 hour day to have a normal happy household.

I concur with @Mattyboy - I also prefer the larger batteries, but having two batteries does provide a measure of redundancy - you could still limp on with only one 5kWh battery if the other one packs up, but with only 1 large battery you will be totally without power if the grid fails on a cloudy, rainy day... best to get two large ones if at all possible 😁

6 minutes ago, HennieL said:

You will have to give us more info - e.g. do you plan to run the geyser and/or AC at night (i.e. from the battery)? For how long will you be running these power-hungry devices? What size element does your geyser have, and what is it's capacity (liters)? Also, are you planning on remaining connected to the grid, or do you plan to go off-grid in the future? For how long do you plan to be able to be "autonomous" (off grid due to power outage, cable theft, etc.)

I have 2 x 10.65kWh Sun-Batt (rebranded Eenovance) batteries connected to my 12kW Sunsynk inverter, and with these I can power my geyser for one hour from the batteries, and run my full normal household consumption for 2 consecutive days without grid power and cloudy sky, and still have enough battery capacity left for a third day without the geyser if I nurse my consumption - but our household is only my wife and I, and we can go without a lot of what most people would consider "necessary" consumption in an emergency... So, IMHO you would need at least 10kWh of battery capacity per 24 hour day to have a normal happy household.

I concur with @Mattyboy - I also prefer the larger batteries, but having two batteries does provide a measure of redundancy - you could still limp on with only one 5kWh battery if the other one packs up, but with only 1 large battery you will be totally without power if the grid fails on a cloudy, rainy day... best to get two large ones if at all possible 😁

@Mattyboy @HennieL Thanks! Out of curiosity could I ask why you guys prefer the larger RW range just for my knowledge?

Also in terms of capacity in terms of duration of use @HennieL I was planning on adding more capacity in the future. No plan to be fully off grid. Ideally 24 hours of backup power but it’s not necessary right now. But definitely some usage at night for an hour or two. AC is 1500 BTU and the geyser is 200L ~3Kv if I remember correctly.

1 hour ago, MuneebK said:

But definitely some usage at night for an hour or two. AC is 1500 BTU and the geyser is 200L ~3Kv if I remember correctly.

With only 10kWh of battery (1 x 10 or 2 x 5), I would suggest that you change the geyser element to 2kW - one hour of use (say) early morning before sunrise would drain ~20% of your battery capacity, whilst with a 3kW element you would drain ~30%.

1 hour ago, MuneebK said:

Out of curiosity could I ask why you guys prefer the larger RW range just for my knowledge?

My only two reasons for preferring the 10kWh units over the 5kWh ones were space (two larger units take up considerably less wall space than four 5kWh units...), and cost (again, 2 x 10kWh batteries were cheaper than 4 x 5kWh batteries, taking into account the additional (thick) wiring, high-amperage fuses, etc.)

For the loads you want to run and the money you're looking to spend, while staying on-grid, I'd suggest to consider going big from the outset with a 15kWh single battery as in the link below to Powerforum store. But if you shop around there could be more alternatives also not too far away in price. Not too long ago that was the price on a 5kWh battery.

Power Forum Renewable Energy Store | By Powerforum.co.za

KNY-P51300 15.36kWh Floor-Type LiFePO4 Battery

Limited Stock on this Special Price 51.2V 300Ah (15.36kWh) floor-standing LiFePO4 energy storage battery – Model KNY-P51300 from KNYSE Energy (part of the reputable Chilwee Group).This is a solid, no

19 hours ago, MuneebK said:

Figuring out what to install. Can't figure out what to do between these two options. Hoping to power lights, wifi, geyser, an AC, and one appliance (eg. microwave, airfryer, etc.) at a time

Have a look at the Deye SE-F16, 16kwh and around the same price

14 hours ago, HennieL said:

With only 10kWh of battery (1 x 10 or 2 x 5), I would suggest that you change the geyser element to 2kW - one hour of use (say) early morning before sunrise would drain ~20% of your battery capacity, whilst with a 3kW element you would drain ~30%.

Catch 22 situation. If you need 2kwh to heat the geyser (11.4deg) for a 150L geyser running a 2kw element for 1 hour then your 3kw element would only run 40min for the same 11.4deg heating. So no saving of power to do the same work. Either element would drain ~20%.

I do however agree the lower load from the battery will be kinder on the battery and increase life.

Edited May 1May 1 by Scorp007

8 hours ago, Scorp007 said:

I do however agree the lower load from the battery will be kinder on the battery and increase life.

Exactly - that was my point. Thanks for confirming this... To take this discussion a bit further, though - if one was off-grid, or simply did not want to use grid power to heat up one's geyser, and if one also would not want to drain one's batteries further after powering the house through the night, then a lower powered geyser element (say 2kW) would be able to start using PV power much earlier in the morning than a 3 or 4 kW element. It would also be able to use PV power later in the afternoons as well... but I'm not disputing the fact that (say) 2kWh power drawn from whatever power source would always be the same - be it 1 hour drawing 2kW, or 40 minutes drawing 3kW.

15 hours ago, HennieL said:

... a lower powered geyser element (say 2kW) would be able to start using PV power much earlier in the morning than a 3 or 4 kW element.

They say a picture paints a thousand words... here's two power graphs from this morning to illustrate the point I made in my previous post:

Picture 1. After a number of really cloudy & rainy days, finally some sunshine 😊. At 08:05 my panels were producing 2.79kW, and my batteries were charging at 2.3kW. At this point in time, there was sufficient PV power to run my geyser's 2kW element, should I have elected to prioritize the geyser, but with only minimal power going towards charging the batteries. There was still not enough PV to power a 3kW element.

Picture 2. At 09:00 the panels were producing 4.81kW, the batteries were charging at 2.1kW, and the load (including the 2kW geyser that was switched on at that time) was drawing 2.3kW. I prefer to keep the batteries' charge rate low, and have set the inverter to not supply more than 3.1kW to the batteries, and it is thus clear from these figures that the PV supply was maxed out at that point in time. It would still not have been possible to start a 3kW geyser element at this time whilst maintaining a +2kW battery charge at the same time.

Edited May 2May 2 by HennieL

This is I love forums.

I just asked what battery is better and we’ve got a technical discussion on geyser usage by power and time 😂

Never change guys.

Edited May 2May 2 by MuneebK

To answer @MuneebK question 1 x 10.6kWh or 2 x 5.32kwh batteries? Installing 1 battery module makes more sense less wiring less components much simpler.

As for the rest of the discussion my 2 cents. Try not to use high resistive loads(geysers) from your batteries.

Let us compare two very different cost models: PV generation vs stored energy.

Additional solar capacity (R/Wp) is still far cheaper per kWh produced over its lifetime than LiFePO⁴ storage (R/kWh usable).

Using batteries to run a 2–3kW resistive load like a geyser is one of the least efficient uses of stored energy (high discharge rate + unnecessary cycling).

If utility/grid is available, it generally makes no financial sense to size battery capacity for occasional cloudy periods just to support non-essential loads like water heating. That’s an expensive way to avoid a relatively cheap backup source(Eskom) used a few days a year. A better approach is load shifting + thermal storage: Heat the geyser during peak PV hours (10:00–15:00) and set thermostat to ~70 °C to increase stored energy capacity. Use a geyser blanket + pipe insulation to reduce standing losses. Let stored thermal energy carry evening demand (mixed down at the tap).

This effectively turns the geyser into a low-cost energy storage system, avoiding battery cycling and preserving stored electrical energy for essential loads..Also consider load staggering only one geyser active at a time..Prioritise based on SOC or excess PV.

Hierarchy should be:

1.Use PV directly

2.Shift loads to sun hours

3.Store as heat (geyser)

4.Use batteries for essentials

5.Use grid as fallback

Oversizing batteries to run high-power thermal loads at night is usually a capital inefficiency, not a system optimisation.

4 hours ago, TaliaB said:

Installing 1 battery module makes more sense less wiring less components much simpler.

Buying 2 x 5kWh batteries is probably cheaper and easier to expand on.

The best ROI is achieved with the smallest battery possible, but I can see that 10kWh or 15kWh is good for backup. If you start with one 10kWh battery, you have to jump to 20kWh when you want to expand.

For every ten 5kWh batteries I have seen, I have seen maybe one 10kWh battery. So, considering the second hand market after a couple of years: 5kWh will be easier to find.

Last consideration: phone two friends to pick up a 10kWh battery.

4 hours ago, TaliaB said:

Installing 1 battery module makes more sense less wiring less components much simpler.

Buying 2 x 5kWh batteries is probably cheaper and easier to expand on.

The best ROI is achieved with the smallest battery possible, but I can see that 10kWh or 15kWh is good for backup. If you start with one 10kWh battery, you have to jump to 20kWh when you want to expand.

For every ten 5kWh batteries I have seen, I have seen maybe one 10kWh battery. So, considering the second hand market after a couple of years: 5kWh will be easier to find.

Last consideration: phone two friends to pick up a 10kWh battery.

1 hour ago, frivan said:

Buying 2 x 5kWh batteries is probably cheaper and easier to expand on.

The best ROI is achieved with the smallest battery possible, but I can see that 10kWh or 15kWh is good for backup. If you start with one 10kWh battery, you have to jump to 20kWh when you want to expand.

For every ten 5kWh batteries I have seen, I have seen maybe one 10kWh battery. So, considering the second hand market after a couple of years: 5kWh will be easier to find.

Last consideration: phone two friends to pick up a 10kWh battery.

Your comments mixes a few practical truths with some assumptions that don’t always hold up technically or economically.

I agree with the first part smallest battery that meets your actual use case usually gives the best ROI. Especially in grid-connected systems, batteries are often the most expensive kWh you’ll ever “buy,” so oversizing them for things like geysers or daytime loads doesn’t make much sense when you can rather push that load into solar hours.

Where I differ is the jump from 10kWh to 20kWh being a “problem.” That’s more a system design and brand limitation than a universal truth. Many modern rack systems (Pylontech, Hubble, Dyness, Freedom Won, etc.) are inherently modular at ~5kWh per unit, so expansion is incremental by design. If someone installs a monolithic 10kWh battery, then yes they’ve locked themselves into larger expansion steps, but that’s a product choice, not a battery principle.

On the second-hand argument:

In theory, 5kWh units might be more liquid but in practice, the second-hand battery market is still very immature, and buyers are far more concerned about:

●Cycle count

●State of Health (SOH)

●Brand reputation and BMS compatibility

A 10kWh unit with good telemetry and warranty traceability will often be easier to move than multiple smaller units of uncertain history.

Also worth noting: more small batteries = more parallel strings, more comms complexity, more potential imbalance issues over time. There’s a real engineering trade-off there, especially in systems that already push multiple parallel packs.

The “phone two friends” comment is funny, but practically speaking, installation logistics shouldn’t drive system design. Most 10kWh-class batteries are still manageable with proper handling, and installers deal with this daily.

Get yourself one of these:

For me the bigger picture is this:

Size the battery for night load and outage requirements only use solar + load shifting for high-energy loads (geysers, pool pumps, etc.)

Keep the system modular where possible, but not at the expense of unnecessary complexity. If anything, I’d argue the real optimisation is:.Spend on panels first, battery second especially if the grid is available.

That’s where the real ROI difference sits.

Edited May 2May 2 by TaliaB

Well, this is morphing into a very interesting discussion...

23 hours ago, TaliaB said:

Try not to use high resistive loads(geysers) from your batteries.

Let us compare two very different cost models: PV generation vs stored energy.

Additional solar capacity (R/Wp) is still far cheaper per kWh produced over its lifetime than LiFePO⁴ storage (R/kWh usable).

Using batteries to run a 2–3kW resistive load like a geyser is one of the least efficient uses of stored energy (high discharge rate + unnecessary cycling).

If utility/grid is available, it generally makes no financial sense to size battery capacity for occasional cloudy periods just to support non-essential loads like water heating. That’s an expensive way to avoid a relatively cheap backup source(Eskom) used a few days a year.

If the object of installing solar is ONLY to save money then I agree with you... however, many of us have installed solar PRIMARILY to not be dependent on a corrupt and inefficient government "state owned enterprise" (Eksdom), compound further with living in a crime infested country where having the municipal and/or Eksdom power cables stolen has become the norm (and leaving users of the utility without any power for extended periods...), and not the exception... So, many people like me would rather pay more to be able to have reliable power when we need it.

17 hours ago, TaliaB said:

Size the battery for night load and outage requirements only use solar + load shifting for high-energy loads (geysers, pool pumps, etc.)

Again, this statement would be applicable to many modern city dwellers who go through life just buying and replacing things (that's what modern living is all about...) - but there are still a number of people who believe (as I do) in fixing things, or (heaven forbid...) actually making things themselves. Now, in my workshop I have (amongst others) a metal lathe with a 3kW motor, and before my recent retirement I could only work in my workshop during the evenings (still do, when it's not too cold...), and this absolutely needed to drain power from the batteries. I also have a good collection of power tools, TIG welder, etc. etc. - and that's why I opted for an overkill 12kW inverter and 20kW of LiFePO4 batteries, rather than having to rely on the unreliable Eksdom... my money, my choice.

17 hours ago, TaliaB said:

Keep the system modular where possible, but not at the expense of unnecessary complexity. If anything, I’d argue the real optimisation is:.Spend on panels first, battery second especially if the grid is available.

That’s where the real ROI difference sits.

I too would like to spend my money well, and have great ROI - but within context of the above... So, having "wasted..." money on a larger than needed for "normal" living system, would it not make ROI sense to deliberately discharge some of the batteries' capacity at night to heat the geyser between 04:00 and 05:00, thereby creating additional "storage space" to harvest more PV during the day (that would have been wasted otherwise)? By the way, in terms of actual ROI, I've recovered slightly more than 27% of my original investment in just more than 1.5 years, and with the utility rate increasing at the rate that it has over the last few years the return is bound to accelerate...

The above is not meant to insult or infuriate anyone other than our national power supplier - merely to point out that one should not judge (or assess) everyone using the same criteria 😇

On 2026/04/30 at 8:39 PM, GreenFields said:

For the loads you want to run and the money you're looking to spend, while staying on-grid, I'd suggest to consider going big from the outset with a 15kWh single battery as in the link below to Powerforum store. But if you shop around there could be more alternatives also not too far away in price. Not too long ago that was the price on a 5kWh battery.

Power Forum Renewable Energy Store | By Powerforum.co.za

KNY-P51300 15.36kWh Floor-Type LiFePO4 Battery

Limited Stock on this Special Price 51.2V 300Ah (15.36kWh) floor-standing LiFePO4 energy storage battery – Model KNY-P51300 from KNYSE Energy (part of the reputable Chilwee Group).This is a solid, no

What happens or what is the plan for redudancy if the whole battery packs up or come cells develop issues? Would your supplier be able to give you a temporary battery replacement whilst the other is being repaired or replaced under warranty? Smaller is cheaper to add additional storage and if one battery packs up, one can limp on one or two in the pack. Space considerations would also be a consideration @MuneebK how tight are you for space?

Not tight for space at all. I was just wondering if there was any tech differences between the two. Or power delivery differences. Plan was always to have at least 2 batteries. Starting with 10 now and later adding capacity for 10 more

On 2026/05/02 at 1:13 PM, MuneebK said:

I just asked what battery is better and we’ve got a technical discussion on geyser usage by power and time 😂

Never change guys.

You ain't seen nothing yet 😂

4 hours ago, HennieL said:

Well, this is morphing into a very interesting discussion...

If the object of installing solar is ONLY to save money then I agree with you... however, many of us have installed solar PRIMARILY to not be dependent on a corrupt and inefficient government "state owned enterprise" (Eksdom), compound further with living in a crime infested country where having the municipal and/or Eksdom power cables stolen has become the norm (and leaving users of the utility without any power for extended periods...), and not the exception... So, many people like me would rather pay more to be able to have reliable power when we need it.

Again, this statement would be applicable to many modern city dwellers who go through life just buying and replacing things (that's what modern living is all about...) - but there are still a number of people who believe (as I do) in fixing things, or (heaven forbid...) actually making things themselves. Now, in my workshop I have (amongst others) a metal lathe with a 3kW motor, and before my recent retirement I could only work in my workshop during the evenings (still do, when it's not too cold...), and this absolutely needed to drain power from the batteries. I also have a good collection of power tools, TIG welder, etc. etc. - and that's why I opted for an overkill 12kW inverter and 20kW of LiFePO4 batteries, rather than having to rely on the unreliable Eksdom... my money, my choice.

I too would like to spend my money well, and have great ROI - but within context of the above... So, having "wasted..." money on a larger than needed for "normal" living system, would it not make ROI sense to deliberately discharge some of the batteries' capacity at night to heat the geyser between 04:00 and 05:00, thereby creating additional "storage space" to harvest more PV during the day (that would have been wasted otherwise)? By the way, in terms of actual ROI, I've recovered slightly more than 27% of my original investment in just more than 1.5 years, and with the utility rate increasing at the rate that it has over the last few years the return is bound to accelerate...

The above is not meant to insult or infuriate anyone other than our national power supplier - merely to point out that one should not judge (or assess) everyone using the same criteria 😇

You’re 100% right on one key point not everyone is solving the same problem.

If your primary goal is resilience and independence from Eskom especially with cable theft, outages, and general instability then oversizing inverter and battery capacity is a completely rational decision. In that context, ROI isn’t just rands per kWh, it’s availability, reliability, and control, which are hard to price but very real.

Where I’d challenge the approach slightly is on how that oversized system is then operated. Using batteries to deliberately dump energy into a geyser at 04:00 to “make space” sounds logical at first, but technically it’s still one of the least efficient energy paths. You’ve already paid a premium to store that energy in LiFePO⁴ you then cycle it (adding wear) only to convert it to heat which could have been done directly from PV the next day

Even with “excess PV” in mind, most systems can be tuned to absorb surplus during the day instead: Raise geyser setpoints during solar hours (e.g. 70°C with good insulation) and use staged or priority-based load control (one geyser at a time)

Shift workshop loads where possible into sunlight hours on weekends or flexible days. That way you avoid unnecessary battery cycling, preserve battery lifespan (which is a major capital component) and still maximise PV utilisation.

On the “creating storage space” argument in a properly sized system, that situation should actually be rare. If you’re regularly hitting full batteries and clipping PV, that’s usually a sign the system could benefit more from additional daytime loads or even slightly less battery relative to PV

Your use case (lathe, welder, evening workshop work) is actually one of the few legitimate reasons to have a larger battery bank because you genuinely need high-power energy after sunset. That’s very different from heating water, which is a low-grade, time-flexible load.

Also, your ROI recovery (~27% in 1.5 years) is solid but I’d argue that’s largely driven by:

1.Tariff escalation

2.High self-consumption

3.Avoided downtime

Not necessarily by how the batteries are being cycled overnight. So I think the middle ground is:

Oversize for independence if that’s your goal absolutely valid.

But once you’ve got that system, run it in a way that prioritises solar-first, battery-second, especially for thermal loads like geysers.

Different goals, same physics and the physics still favours using the sun directly wherever you can. 😜

7 hours ago, TaliaB said:

Using batteries to deliberately dump energy into a geyser at 04:00 to “make space” sounds logical at first, but technically it’s still one of the least efficient energy paths. You’ve already paid a premium to store that energy in LiFePO⁴ you then cycle it (adding wear) only to convert it to heat which could have been done directly from PV the next day

Even with “excess PV” in mind, most systems can be tuned to absorb surplus during the day instead: Raise geyser setpoints during solar hours (e.g. 70°C with good insulation) and use staged or priority-based load control (one geyser at a time)

Thanks for your positive response @TaliaB

I would appreciate further comment regarding my deliberate battery use at night to heat the geyser:

There are two advantages for me in doing this: Firstly, we are early risers, and prefer to shower/bath in nice hot water, and this 2kW boost just takes the water temperature back up to the set limit of the thermostat (~65 Celsius). Secondly, harvesting an additional 2 kWh of free sunlight every day does have a small financial impact without (to my understanding) impacting negatively on the batteries' SoH.

I believe in treating my batteries as good as possible within reason, but they are there to work! My battery charge rate is set to a limit of 0.15C (60A), and the discharge rate is limited to 0.4C(160A). The batteries reach 99% SoC nearly every afternoon, and drop to ~85% SoC at sunrise if I do not heat the geyser (and do not use any power tools in the evening...), and to ~75% if I do heat the 2kW geyser for one hour at night at a current of ~39A. In my opinion this is a very mild partial discharge (0.1C), and I doubt if this use could seriously affect the life of the batteries (especially since I also keep their operating temperature between 15 and 25 degrees Celsius). However, I'm never to old to learn, and will gladly stop this practice if someone can convince me that it is truly detrimental to the service life of the batteries...

1 hour ago, HennieL said:

The batteries reach 99% SoC nearly every afternoon, and drop to ~85% SoC at sunrise if I do not heat the geyser (and do not use any power tools in the evening...), and to ~75% if I do heat the 2kW geyser for one hour at night at a current of ~39A.

I recently saw a video going though a study they did on LFP cells and it was quite informative , among one of the important points was that cycling from 75-100% caused the most cell degradation. Cycling at a lower SOC range, like 0-60%, resulted in less degradation. Cycling from 0-100% is better for the battery than 75-100% which most people probably wouldn't expect. Here is the study and video :

https://iopscience.iop.org/article/10.1149/1945-7111/ad6cbd/pdf

https://youtu.be/w1zKfIQUQ-s

Edited May 4May 4 by Nexuss
Grammar

1 hour ago, HennieL said:

Firstly, we are early risers, and prefer to shower/bath in nice hot water,

1 hour ago, HennieL said:

Secondly, harvesting an additional 2 kWh of free sunlight every day does have a small financial impact

The usual disclaimer: Layman's opinion, personal 2c worth, use at own risk, to be adapted for your own situation, get professional advice.

On the first comment, that you are early risers, etc. I agree that people have their own routines, own usage patterns, and that the optimum solution in one case might not work or make sense for others. The idea of increasing the water temperature to 70 degrees might work for people who want to store as much heat energy as possible for evening baths & showers for the kids, but if you then have adults who want to freshen up with a morning shower, I'm not sure if that using the geyser as a battery is always a workable strategy. For those who need hot water first thing in the morning, there's this idea to run off battery, alternatively a heat pump could do that heating for the morning (and generally) more efficiently off battery and solar. Finally, what I'm doing, is running the geyser from the grid in the early morning, using a timer, while on an off-peak time-of-use tariff that's cheaper.

Back to the battery, though, I'm wondering if the concern about "using up the battery" on low-grade non-essential tasks like water heating really... yes I'm going to say it ... holds water. Firstly, if you need hot water in the morning for the family to wash and go to work, school, etc. then that to me is essential and time-critical. Beyond a point you can't shift all loads to the day.

Next, though, I'm wondering whether the cost of the battery is really such a big factor as it was before, from the point of view that the cost per kWh cycled in and out of the battery has come down dramatically. Just using this 15kWh battery as an example (and I'm sorry for harping on it, I'm not a spokesperson for it, I just like the concept on paper), then 80% cycling down times 6000 cycles gives a cost of around R0.40 per kWh. A third of what it used to be when I first bought. You can't run from the grid at that price. Okay, one should factor in the capacity loss and installation costs and go on full quotations, but say that it ups the cost to R0.80/kWh. You still can't buy power from Eskom at that price, so I'd say to let rip, run a 2kW or even a 3kW element, well within the 100A recommended discharge capacity of the battery, without a second thought, and start treating home battery power like a disposable. The fact that some of these big batteries are floor-mounted and come with trolley wheels, tells me it shouldn't be that hard to swap them out while running on grid in the interim.

Edited May 4May 4 by GreenFields

My take after reading the thread digging into the tech.

The discussion is solid, but a few assumptions vs realities stand out.

Common Assumptions vs Reality

Two batteries = better redundancy

True in theory, but in practice for a typical home setup with daily solar, a quality single battery failing is quite rare.

Redundancy is nice but often overvalued at this small scale.

Bigger single battery = riskier Not really.

Modern 10–15 kWh LFP packs with good BMS are very reliable.

The real limiter is usually how well cells stay balanced over years.

All BMS are equal

This is the biggest gap. Most Deye batteries use passive (bleed) BMS simple, cheap, and sufficient for light use with regular full charges.

However, they dissipate excess energy as heat and balance slowly, especially with LFP’s flat voltage curve.

Better Educated Choice in Lithium Tech.

Active BMS like on the KNY-P51300 15.36 kWh transfers energy between cells efficiently instead of wasting it.

Benefits Are.

Faster balancing even during discharge/idle.

Less heat.

Better long term capacity retention.

Higher usable energy in real world conditions.

For a home grid tied setup with modest loads:

Single 10.6 kWh Deye (Passive BMS) Simple, clean, good enough if you get regular full charges.

KNY 15.36 kWh (Active BMS) Stronger long term choice more capacity plus superior balancing for only a bit more money.

For most homeowners, prioritize Active BMS good capacity over splitting into multiple smaller passive packs.

Focus more on smart load management geyser timing, insulation, PV direct use than worrying about single vs dual batteries.

The tech has matured active balancing is no longer premium only.

It’s now one of the smartest upgrades you can make for longevity and efficiency.

16 hours ago, Moffat said:

What happens or what is the plan for redudancy if the whole battery packs up or come cells develop issues? Would your supplier be able to give you a temporary battery replacement whilst the other is being repaired or replaced under warranty? Smaller is cheaper to add additional storage and if one battery packs up, one can limp on one or two in the pack. Space considerations would also be a consideration @MuneebK how tight are you for space?

Their warranty is a Swap Out Warranty still carry in so cost of transport is for the consumer.

User feedback on these batteries are very good and Supplier have not had one faulty return thus far.

Active BMS means the battery will be much more reliable.

On 2026/05/03 at 4:25 PM, HennieL said:

20kW of LiFePO4 batteries, rather than having to rely on the unreliable Eksdom... my money, my choice.

@HennieL I would have suggested sharing some solar with your mother in law. But seeing that you already wasted the money, she must move in with you!