Blue Nova charge current specs driving me crazy

[frankvw]

I have just bought a BlueNova BN26V-108-2.8k battery. I'm happy with it but the specs are confusing.

I'm using a charger/inverter in UPS-like mode for now, but I'm planning to add some solar panels soon, which raises the question about what current the charger controller should deliver in order to balance recharge times against service life. So I first had a look at the relevant specs in the datasheet that came with the battery. It specifies "Charge Current" as:

• Recommended: 20A
• Maximum: 100A continuous

However... On the top of the battery is a label that says:

• Charge current = 50A (standard); 100 A (max)

So we have "recommended" charge current, "standard" charge current and "max" charge current, while "max" is apparently also "continuous". Uh-huh.

I contacted Blue Nova South Africa for clarification. They responded with a set of specs that included:

• Charge current: 40 Amps

So they don't know either.

Does anyone here have any ideas about what's what? Or about what's sensible in general for LiFePO4 batteries?

Note: I'm using a Victron Multiplus inverter/charger which has a proper charge profile for LiFePO4, and I'm looking at a SmartSolar which either has one too or can be programmed with same.

 

[BBSA]

Since your Victron devices have LiFePO4 charging profiles, you can likely trust them to manage things properly. Set the charge current considering the following:

Start with the 20A recommended current for maximum battery life.

If you need faster recharging and are willing to potentially sacrifice some cycles, you could cautiously increase the charge current, up to the 50A "Standard" range.

Avoid exceeding 50A regularly, and definitely stay under 100Ah.

 

[frankvw]

Since your Victron devices have LiFePO4 charging profiles, you can likely trust them to manage things properly. Set the charge current considering the following:

Start with the 20A recommended current for maximum battery life.

If you need faster recharging and are willing to potentially sacrifice some cycles, you could cautiously increase the charge current, up to the 50A "Standard" range.

Avoid exceeding 50A regularly, and definitely stay under 100A unless it's an absolute, short-term necessity.

I agree with you on the reliability of Victron profiles. Right now I've got a Mulitplus 24/800/16 which charges the battery with 16A max so that's fine. It keeps the TV, lights, fans and backup water pump running nicely during loadshedding and unplanned outages.

However, I'm looking at adding a SmartSolar MPPT 100/50 (and 4 panels rated at a maximum power yield of 550W each) for charging and a Phoenix 24/1200 for powering an additional set of freezers. (I'm currently working out how much they draw; I want to keep the discharge current and cycle depth down to reasonable limits.)

The MPPT 100/50 can be programmed (as I understand it) to limit the charge current to less than the max. 50A. During daylight / sunshine hours I'd power the Phoenix inverter pretty much straight from the MPPT while only the excess would go into the battery. But the fridges and freezers don't run continuously, and during the night I'd rely on the 16A provided by the Mulitplus only while during sunlight hours this would be added to the current from the MPPT.

So that could still get a bit complicated...

 

[leon.davibe]

I agree with you on the reliability of Victron profiles. Right now I've got a Mulitplus 24/800/16 which charges the battery with 16A max so that's fine. It keeps the TV, lights, fans and backup water pump running nicely during loadshedding and unplanned outages.

However, I'm looking at adding a SmartSolar MPPT 100/50 (and 4 panels rated at a maximum power yield of 550W each) for charging and a Phoenix 24/1200 for powering an additional set of freezers. (I'm currently working out how much they draw; I want to keep the discharge current and cycle depth down to reasonable limits.)

The MPPT 100/50 can be programmed (as I understand it) to limit the charge current to less than the max. 50A. During daylight / sunshine hours I'd power the Phoenix inverter pretty much straight from the MPPT while only the excess would go into the battery. But the fridges and freezers don't run continuously, and during the night I'd rely on the 16A provided by the Mulitplus only while during sunlight hours this would be added to the current from the MPPT.

So that could still get a bit complicated...

Yea the problem is the 4 panels at 24 v system would be 91.66 amps. So having 4 panels will immediately mean you are buying panels to be idle

On bad weather days it is a plus though

So if you limit the mppt to 50A it will supply max 50a irrespective if it is going to battery or load effectively limiting your panels to 1200w


Imo it isn't worthwhile to try and extend the life of the battery foregoing on savings that will outstrip the cost of the battery

ie try and save R10k battery giving up on R20k + power. Savings over its life

So if the battery is capable of 1c/1c i would work it like that

You can limit the SOC to not go below 20% though as that impacts the cycles quite a bit

Imo that mppt is only suitable for 2 550w panels start with that and see what it delivers before trying to up size the array
Or buy a bigger mppt if you want to be able to utilise all 2200w

You will however have a fatter boob ie you will hit the 1200w limit earlier in the morning and maintain it for longer in the afternoon , and have more usable power in bad weather

But it comes at higher cost ie you will have 2extra panels that only produce from 7am till 9am? and then be idle until likely around 4pm and then as the output of the others drop off it will become usable again

likely sacrificing more than 60% of its potential output

ie you will lose the meat& potatoes portion of mid day on those panels

 

[leon.davibe]

Some batteries specify 0.5c/1c
And others specify /1c/1c

Normally the bms will be set to not exceed the cell specs

so not possible to exceed the cell specs

some bms's also has temp sensors so if stuff gets out of hand it limits charging

if not wanting to void the warrantee though best to use what they say

 

[frankvw]

Yea the problem is the 4 panels at 24 v system would be 91.66 amps. So having 4 panels will immediately mean you are buying panels to be idle

On bad weather days it is a plus though

So if you limit the mppt to 50A it will supply max 50a irrespective if it is going to battery or load effectively limiting your panels to 1200w

Keep in mind that the rated 550W solar panel yield is specified under absolute 100% optimal (almost theoretical) circumstances. In practice it will be closer to 300 more often than not, what with varying sunlight intensity, changing angle of the sun, contamination deposits on the panels etc. The fact that a panel is rated at 550W doesn't mean that that's what will be going into your batteries and loads.

 

[Gnome]

I've said this many times and people seem to be ignorant of this fact but you can't simply look at the watt-hour capacity of the battery.
The continuous discharge current and charge current are equally important.

If you are going to use 1 of these batteries, which is according to the product number 24v battery.
Your maximum discharge current is 100 amps, but they typically recommend half that for continuous.
That is 2400w (100amps) and 1200w (50 amps) respectively, and that is before you take inverter efficiency into account.

Inverters are pretty much switch mode power supplies, so at 80% load you can expect around 85-90% efficiency and any good electronic engineer would build a buffer in there, so take 80%
It is a good safety margin number.
That comes down to 1920w and 960w respectively inverter output.

It should become quickly obvious if you are running this with a 24v inverter you should be running 2 of these, assuming the inverter is the 3kVA variant.
5kVA you need a lot more batteries.

 

[rh1]

Op, the perfect song for your situation:

 

[leon.davibe]

Keep in mind that the rated 550W solar panel yield is specified under absolute 100% optimal (almost theoretical) circumstances. In practice it will be closer to 300 more often than not, what with varying sunlight intensity, changing angle of the sun, contamination deposits on the panels etc. The fact that a panel is rated at 550W doesn't mean that that's what will be going into your batteries and loads.

Yea agreed area dependant too (temps)

I have a 3650w array and normally see around 3200-3300w peak
ie 87-90% of rated
And have seen spikes up to 4800w on overcast days and higher peak during cooler months shorter time span though

in october i had 2275w array and got peaks of aroud 2250w

And exceed 50%of output between 9am and 5pm in summer hence why i say on sunny days the extra panels will do nothing from 9-5

Which would be close to what the 1200w limit would be of the 2200w array ie 54%

Now yes bad weather and and shorter days in winter it may be a different story

300w from a 550w would represent 54% bit pessimistic imo
(Though this opinion is based on my results and yours may be based on opinions from people closer , so i may be wrong as temps does affect things -salt)

 

[frankvw]

300w from a 550w would represent 54% bit pessimistic imo
(Though this opinion is based on my results and yours may be based on opinions from people closer , so i may be wrong as temps does affect things -salt)

I can see and ear the ocean from here (I'm at the KZN south coast) so we've got cloudy days more often than, say, the Highveld. Right now it's sunny but not quite clear; haze is quite common. So I'm trying to allow for that.

 

[Oldfut]

I regard Blue Nova as very marginal batteries, particularly for critical use or the longer term. I have one that has seen very little use as it is a backup but needed constant "topping up". BMS switched it off at one stage, now it has not recovered, 12V nominal now won't charge beyond 9.40V with a Victron charger.

Blue Nova have a technical help email ([email protected]) but don't expect too much. Rather switch to something of better quality?

 

[leon.davibe]

I regard Blue Nova as very marginal batteries, particularly for critical use or the longer term. I have one that has seen very little use as it is a backup but needed constant "topping up". BMS switched it off at one stage, now it has not recovered, 12V nominal now won't charge beyond 9.40V with a Victron charger.

Blue Nova have a technical help email ([email protected]) but don't expect too much. Rather switch to something of better quality?

Sounds like it needs a jump start

Cause lifepo4 will hit 12v+ very soon after charging starts
So it isn't charging in some protection mode, normally in low voltage protection mode voltage disappears or on the bms's i have used so far it has been the case

Touch the battery with spare battery or with a dumb charger while victron charger connected

Or any other 12v dc power source

Or charge a bit with a dumb charger once voltage lifts connect victron charger again

If it was in low voltage protection it should start charging

If not then it may be some other protection mode , maybe disconnect the terminal for a few seconds and see what voltage does, reconnect and try chatging again

Does the bluenova have bluetooth ? So you can see cell voltages

 

[UB40]

Agree with @BBSA Charge low and slow if you can. Find the right charge current for your needs through trial and error. No battery likes to be charged hard and fast. I recommend charging at 0.5C to keep the battery nice and cool so that it doesn't get warm/hot, this will also increase your life cycles on the battery.