Charge Current and Battery Temperature?

[Ingo]

All,

I have a 48V 300AH battery bank (two strings) and according to the datasheet it states 'Initial Charge Current' as 45A per battery(string). Now in my mind I can then charge at 90A for the bank and each string will get 45A as per the datasheet. That sounds a bit excessive so I actually limited my charge current to 30A (15A per string).

I basically have two questions:

1. Am I doing my battery bank a disservice in charging at a lower rate and

2. Temperature at 30A charging I saw this morning is at 37 degrees. I don't want to think what it will be at 90A.

Any comments would be appreciated.

Ingo

[Guest]

2 hours ago, Ingo said:

1. Am I doing my battery bank a disservice in charging at a lower rate and

2. Temperature at 30A charging I saw this morning is at 37 degrees. I don't want to think what it will be at 90A.

1. If the charge is between 8% and 13% of the banks ah, don't think so no. That is for lead acids.
2. Presume you have a Victron MPPT, it handles it all for you. Would not stress too much about it no.

Obviously, the cooler the bank can stay the better, but with charging it is going to generate a bit of heat.

[Ingo]

Quote

If the charge is between 8% and 13% of the banks ah, don't think so no. That is for lead acids.

Yip, it's Deltec Lead Crystal batteries. The charging is done straight from a Quattro, no MPPTs.

[Chris Louw]

Hi Ingo I also have 300Ah Lead crystal battery bank . Deltec claims the batteries are not prone to sulfation and can be used not charged 100 %  . How do you check your temperature . My charging rate is set at 50 Amps but do not go higher  than 40 Amps and is full at 09:30 . The battery maintenance states that every 3-6 months the battery must get a good discharge (50-70%) and then do a good charge in our case 90 Amp .  I do that every 6 months and up to now 22 months in use the batteries is still good  . Would like to know what your impression is of the Lead Crystals .

[Ingo]

Hi Chris,

The batteries are fairly new and only worked the normal Load Shedding discharges up to 4H at a time and not going past around 70% SOC. I bought an additional temp sensor to connect to my Venus so I can keep an eye on the temperature. I read somewhere that if I move the sensor from my Quattro to the Venus that it stops using temperature-corrected charging.

I actually found a Battery Guideline from Deltec (I think) that states in a float scenario you have to be more 'aggressive' with the cycling of the batteries. For now they work like a charm and I try and cycle it to around 60% every two weeks if Eskom doesn't beat me to it 

Quote

Lead Crystal
CHARGING AND COMMISSIONING REQUIREMENTS.

Initial charging current to be 0.3C ( IE 30 amps for each 100 A/H)a.This requirement is important and must be adhered too at all times.

Bulk charging voltage is 2.45volt per cell @ 25°C (14.7 v for a 12volt block)a.Charging below this rate will result in partial charging and void any warranty.

Absorption charging voltage is also to be 2.45 volt per cell @ 25°Ca.This should continue until the tail current reaches at least 0.03C (IE 3 amps for a 100A/H battery).

Float charging voltage to be set at 2.26667 volts per cell (IE 13.6 volts for a 12-volt block) @ 25°Ca.The current should be monitored to ensure it does not exceed 0.01C (IE 1 amp per 100 A/H in the battery circuit). b. Extended high float current will result in dehydration of the product. Extreme cases will result in a badly swollen product.

Temperature compensation on extended float voltage must be adhere too as extended float charging at high temperatures will have an effect on battery hydration levels.

Batteries that are used in float applications must be cycled to at least 50 % DOD on a bi-monthly basis.a.This is a warranty requirement from the manufacturer.

The manufacturer insists that the user or installer must prime the battery set by cycling it 5 times and equalizing the bank installation before commissioning the system.

If the installation consists of only one block then the battery must be fully cycled 5 times to 50% DOD and recharged as per specifications.

The procedures are set out in the installation manual of the manufacturer.

 

[Chris Louw]

This from the user manual from Betta batteries . They actually recommend a higher discharge . My normal cycling is to about 20% DOD . When I bought them a lot of people was quite critical about them . Up to now I am happy with them .

[Ingo]

Interesting...  Two sets of rules and when there is a warranty claim then the other set was the one to follow.

Edit: Strange that the file I got the info from no longer exists on their website.

Edited February 11, 2019 by Ingo

[Ingo]

I just had a look at a video from Betta Batteries and they insist you charge the batteries at 30% of rating during the Bulk stage. For my CNFJ-150's it means 45A per string but 35A will have to do as I only have 70A Max.

[Ingo]

Chris,

I changed my charging current to 70A and as luck would have it Eskom gave me the opportunity to test it after a 3H30 break in power. Like you, I only saw 40A charging current from a 78% SOC. Perhaps it will charge at a higher rate if the SOC falls lower. I am going to leave it like this to see what happens over time.

btw, the temperature reached while charging at 40A is 34 degrees C so no concerns there.

[Chris Louw]

At this stage I am happy with the state of my battery bank . Our energy consumption is the same everyday . I use a shunt and energy meter to record the amount of energy we use .The 2 things that is important for me is a set bulk charge time everyday 140 min. at 58.4 volt and the 90 Amp charge every few months . I do ad some external charging to get a full 90 Amps . The 140 min works for our use , adjust according state of battery and amount of energy used .

Do you have any balancers on your bank . The bank is fitted with 2 x HA02 balancers . They seam to do a good job . Once a week every battery is checked and there is little difference . I also do rotate the batteries once a year .

There is no battery management system on the bank . Don't want to spend money on something I not going to use in the future . Lithium was not available for my setup wen I bought this set  . Would like to get info from other Lead Crystal users .

[Ingo]

Your setup is similar to mine, the Bulk time I set to 4H when I raised the charge current from 30A to 70A and also at 58.4V. I too have two HA02's connected and they keep all eight batteries happy. The 90A 'oomph' I can't get to, that must be a serious charger you have there. I must say that going from 78% to mid 90's last night was fairly quick so keeping the Bulk time at 4H seems to work.

I don't have solar yet so it's just a big UPS for now and didn't want to go Lithium just for storage. Once my battery bank deteriorates I will consider Lithium or whatever tech is available for daily cycle as I will have solar by then. Looking at Solar for this year but I have a very specific roof area and the 'standard' high wattage panel dimensions won't fit properly. Unfortunately SunPower WILL fit the roof space but not my pocket - will have to get creative to maximize power.

[Ingo]

@Chris Louw this might be of interest to you.

Quote

Change log for v2.23~5

 

Add ModbusTCP registers:

- Add register for VE.Bus reset (write a one to it to restart the system after it locked out. Mirrors the functionality as the same option in the GUI).

- Add registers for LowCellVoltage alarm; works with the Lynx Ion BMS

- Add register for Battery Temperature on VE.Bus devices (Multi, Quattro)

- Make the battery monitor relay writable. Works with the Lynx Shunt VE.Can. (Thank you Shane for suggesting this)

- Added registers for charge current and temperature alarms; available for BYD and some other CANbus connected batteries.

 

In case you have noticed the Multi/Quattro battery temperature measurement above: yes; that is coming; also for monitoring via VRM; and using it for Shared Temperature Sense. More information about that later. In v2.23 all thats possible is reading it via ModbusTCP.