Wire for 125 amp fuse

[Isetech]

The lithium 12 VDC battery is around R5-8000. the gel battery we get for R2-3000.

Most customers done see the benefit of spend 3 times the price, I dont have enough experience with lithium or know of anyone who has had lithium installed long term yet.

It boils down to monitoring and tweeking the system, we find that most issue with batteries, are installer related (inexperience and setup) and no remote monitoring.

[Isetech]

Something that has me wondering about the "cutoff" voltage. The test I have just completed had the default gel setting used by the inverter (cutoff - 21 VDC) I plan to change the setup to user and increase it to 23 VDC.

The inverter got to the cutoff voltage and I switched of the load, resulting in an increase in voltage which stabilised at 23.3 VDC. The question I ask myself, why increase the cutoff voltage to 23 VDC when the voltage under load, is it a true reflection of the voltage, I would assume and will do the test as soon as the battery is fully charge, that the higher the load the higher the voltage will jump once the load is removed. With a 60 % load the voltage may stabilise at 24 VDC. It is going to be interesting monitoring the test results and response.

[Isetech]

The result of the first test using a 3 kva MCE/RCT/Meccer (axpert, also branded under other names) type inverter, with a 2 x 100 amp/hr gel batteries. At a cost of around R10-12000.

Only loaded to 30 % you will only get 1hr20min of backup using the default gel setup not even even going to get you through 2 hours of load shedding. If you want to save the batteries and reduce the DOD, you will only get 1 hour.

I want to see how little you can load to get 2-3 hours of backup using gel batteries. I dont have a lithium battery so I can test. A customer might be buying a lithium battery so I can test them.

I havent decided on the brand yet, I have considered Blue nova or Hubble or BSL or maybe even a pylontech ( just too many choices)

[GCE]

Using 2 x 100Amphour gel batteries at 30% gives 720whr that you can use - We say no more than 300watts of load per hour which will give the 2hours and a bit of load shedding and keep under the 720watt hours available.

2 x 100Amp hour gel batteries are about 5K - 1 x 200Amp hr lithium replacement is 8K but at 12v or alternatively 2 x 100Amphour lithium replacement at 10K for 24v system.

[Isetech]

A few things I learnt during our 13 day power outage: I wish I had solar panels installed.

Lead acid batteries are way cheaper, but the negative impact is not worth the money saving. I had 4 lead acid and 2 gel batteries, so everyday I had to swop out a set.

You need to take the time required to recharge lead acid batteries, a 10 amp charger will take 10 hours to charge them, then you might say well just triple the charge current and reduce the charge time, not so simple. the lead acid and gel batteries have a max charge current (the gels I have on the workbench cannot charge more that 20 amps)

The depth of discharge also becomes and issue unless you are prepared to sacrifice the battery cycles.

Just so many things to take into consideration, without even going into the DOD and peukit effect, etc of lead acid batteries, it just doesnt make sense to use lead or gel batteries, unless you have a 100 watt (230VAC) load and 4 x 100 amp/hr batteries and even then in 3 years time you have to outlay another R8-10 K to replace the batteries. Some people say their batteries last more than 5 years, show us the stats wit the recording to back it up.

When buying lithium batteries a BMS is advised, not sure how the this would affect installing 2 or more lithium batteries to an inverter.

[Isetech]

What is your total load in watts? You have 2400wh × 0.5(50%dod)=1200wh if you have a computer in the mix why don't you rather use a ups better protection and switching times

When I first read this reply, my thought, why the battery DOD was mentioned, it got me thinking about cable and fuse selection and the C rating of the battery. IF you have a C rating of 0.5, you can only charge and discharge the battery at half the rating, so could you not use the Crating of the battery to determine the cable and fuse size? Why would you need a 160 amp fuse and 50 mm cable, if the battery can only charge or discharge at around 70-80 amps(half the power rating of the inverter), am I missing something?

[Justloadit]

A few things I learnt during our 13 day power outage: I wish I had solar panels installed.

Lead acid batteries are way cheaper, but the negative impact is not worth the money saving. I had 4 lead acid and 2 gel batteries, so everyday I had to swop out a set.

You need to take the time required to recharge lead acid batteries, a 10 amp charger will take 10 hours to charge them, then you might say well just triple the charge current and reduce the charge time, not so simple. the lead acid and gel batteries have a max charge current (the gels I have on the workbench cannot charge more that 20 amps)

The depth of discharge also becomes and issue unless you are prepared to sacrifice the battery cycles.

Just so many things to take into consideration, without even going into the DOD and peukit effect, etc of lead acid batteries, it just doesnt make sense to use lead or gel batteries, unless you have a 100 watt (230VAC) load and 4 x 100 amp/hr batteries and even then in 3 years time you have to outlay another R8-10 K to replace the batteries. Some people say their batteries last more than 5 years, show us the stats wit the recording to back it up.

I refuse to install any system with lead acid, I rather walk away if the customer insists.
After 10 years of playing around with lead acid in the solar arena, no matter the make, I found that after approximately 200 days, irrespective if used only slightly over night, that the capacity started to degrade. It has something to do with sulphating.
Just had too many complaints saying that I supplied crappy batteries.

Having used Lithium Phosphate, after 5 years are still running, and do not seem to have lost any of its capacity. When these batteries originally came out, they were costly, something like R4,000.00 where the Lead acid was R90.00 but even at the original high cost, they have out performed the lead acid, and saved in money both in the battery cost, and the call out fee, had I continued to use and replace the lead acid.

When buying lithium batteries a BMS is advised, not sure how the this would affect installing 2 or more lithium batteries to an inverter.

If am not mistaken, all battery manufacturers are required by law to have a BMS in their battery packs. The only time that BMS are not supplied, is in the case that you actually purchase the individual cells, but as soon as you pack them into a battery, you have to use a BMS for protection.

[Isetech]

The only upside to lead acid, if you are the company replacing them, it is the quickest R6-800 you can make in a couple minutes. If you install systems with lead acid batteries, you have guaranteed money, throw in a bit of load shedding and its money for jam.

[BEVIN]

HI THERE SIR
THANKS FOR THE GREAT INFO
I WOULD LIKE TO ASK A QUESTION PLEASE
I HAVE AN 8 KW SUNSYNK INVERTER WITH 2X 48/51VOLT BATTERIES LITHIUM SUNSYNK ALSO
I HAVE A DOUBLE FUSE SET UP WITH 2X 160 AMP FUSES
WHAT SIZE OF CABLE WILL I NEED TO USE . THE DISTANCE WILL BE LESS THAN 2M FROM THE INVERTER TO THE BATTERIES AND FUSES ACTUALLY BENEATH EACH OTHER
I DO NOT HAVE ANY SOLAR PANELS IF THAT WILL INFLUENCE ANY THING
IF I HAVE 25MM CABLES AND RUN THOSE CABLES PARALLELL(DOUBLE) WILL THAT BE OK ? (AND PLACE THE TWO LUGS ON ONE FUSE CONNECTION BOLT
I WOULD PREFER AVOIDING THE BUSBAR METHOD
THANK YOU SO MUCH
PS AT THE RISK OF APPEARING FOOLISH THE CALCULATIONS TO DETERMINE THEFUSE SIZE AMPS FROM KWH IS BASICALLY P=IV THE BATTERIES ARE BOTH 100 AMP HR 5KW

[Isetech]

The cable from the inverter to the fuse disconnect should not be less than 50 mmsq (selected as per your calculations, could be bigger)

The cables between the battery and the fuse disconnect, cannot be more than 25mmsq (the terminals on most lithium batteries can only cater for 25 mmsq).

I use 1 x fuse 160 amp or 1 x 250 amp depending on the installation design, connect the batteries in parallel cascade, which means I connect the 2 batteries together with 25 mmsq cable, then take the 2 outer cables to the fuse disconnect, then 50 mmsq from the 1 fuse disconnect to the battery terminals on the inverter.

HI THERE SIR
THANKS FOR THE GREAT INFO
I WOULD LIKE TO ASK A QUESTION PLEASE
I HAVE AN 8 KW SUNSYNK INVERTER WITH 2X 48/51VOLT BATTERIES LITHIUM SUNSYNK ALSO
I HAVE A DOUBLE FUSE SET UP WITH 2X 160 AMP FUSES
WHAT SIZE OF CABLE WILL I NEED TO USE . THE DISTANCE WILL BE LESS THAN 2M FROM THE INVERTER TO THE BATTERIES AND FUSES ACTUALLY BENEATH EACH OTHER
I DO NOT HAVE ANY SOLAR PANELS IF THAT WILL INFLUENCE ANY THING
IF I HAVE 25MM CABLES AND RUN THOSE CABLES PARALLELL(DOUBLE) WILL THAT BE OK ? (AND PLACE THE TWO LUGS ON ONE FUSE CONNECTION BOLT
I WOULD PREFER AVOIDING THE BUSBAR METHOD
THANK YOU SO MUCH
PS AT THE RISK OF APPEARING FOOLISH THE CALCULATIONS TO DETERMINE THEFUSE SIZE AMPS FROM KWH IS BASICALLY P=IV THE BATTERIES ARE BOTH 100 AMP HR 5KW