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We had our system checked and the VE engineer set the ABS to 14.70 and the Float to 13.8.
However, the batteries have been charging at 15.75v and they're now cooked. How could this happen? He has sent me a screenshot to show the settings so I don't think he's done anything wrong. The batteries are: VE AGM supercycle 125a x 6.
Totally different system but I had a similar issue:
https://community.victronenergy.com/questions/8273/bluesolar-7515-voltage-too-high.html
You mentioned that the battery model you use is VE AGM supercycle, and the battery type indicated in the screenshot is VE AGM Deep Discharge (including other types).
Is this the right setting for your battery model ?
That's a good point, but it seems that profile is Kind of the super cycle batteries. Having now looked at the history on the new battery monitor is shows they've had 20V at some point in the last 3 weeks. So, no wonder they're cooked. But I need to find out how that happened. Really odd. Any ideas gratefully received.
Is a temperature sensor fitted that is connected to the Multiplus?
What enclosure are the batteries in? How much venting is there?
What is their average and peak temperature? Can you touch them while charging?. Has the charge voltage been derated for ambient temperature above 25deg/c? if the enclosure gets to that?
How much air gap is between the batteries?
Can you please post a photo of your battery install?
Are the solar chargers set to 12volts, not 24?
I have had a couple of installations lately where the last person had batteries mounted too close together without temp compensation on the charger, causing thermal runaway.
It's not nice trying to explain to a client why his 8 Lifeline batteries are toast.
Agree with Boekel on his comments.
Any answers you can gather to these questions would help greatly
Darren
Dear Darren
I think you might be right. The batteries are pretty tight in the two fibreglass boxes. They are touching each other. Please see photos. We don't have a battery temperature sensor (although this is something we will now install). The solar chargers are definitely set to 12V. Maybe when the VE engineer changed the settings to fast charge the extra temperature caused by this setting could have caused the damage? They have been ok for the last year at a lower charge setting. 
Oh my.. I don't much like paralleled batts under perfect conditions, and your's haven't been given that. Wiring I mean.. http://www.smartgauge.co.uk/batt_con.html
What do you mean - wiring? We paid extra last year in France to make sure the wiring was balanced and right for our new batteries?
Do you mean the wiring of the monitor or the actual batteries themselves?
The batt wiring.. Sure they may be large wires, but true balance is a real challenge to achieve with 6x in parallel. In fact it's almost impossible. Please read the link I posted. Tis why I suggested a softer charge profile.
Boekel also stressed temps. And I agree. So which batt do you add the temp sensor to given natural imbalance, when the hotter batt will develop less resistance and get even hotter with more current flowing - until it dies.
And it's neighbour stays cool.. and the hot batt may be the fittest, but it dies first.
I have an auxiliary 4x parallel bank of old batts doing light duty, that I expected to die early. I give em a soft charge, and they've lasted way longer than expected.
So, how should new batteries be wired? Or wire the same with a much softer profile, plus a temperature sensor?
750Ah @ 12V is a substantial bank. In 6x strings with no 'midpoint' to monitor, a bit of a gamble. I can't help that, such is life..
I could suggest stuff that mightn't physically fit, like 6V or 2V batts, or Li's with their own bms. The stepup will invariably cost, and mightn't find your favour.
If you replace your existing setup with similar batts, wire them optimally and treat with kid gloves.
I don't think we can argue for different batteries from VE, so it is likely we will be getting the same. The Li's are horrendously expensive and out of our price range. I think treating new batteries with kid gloves is the only option. ie try and keep them cool and keep the charge cycle low.
That is a very interesting article you posted. It seems that the original set up was the positive at one end of the 6 and the neg at the other end - as per option 2 on the data sheet. However, in Malta we had a new battery monitor installed and he installed a new shunt. Because the neg cable was cut, the neg now comes of battery 4. He said it didn't matter, but it clearly does.
Catweazle, If I may so bold and if you HAVE not already purchased the new batteries, Have a very good look at changing to lithium phosphate batteries.
1/4 the weight 1/4 the size and they usually come with a Battery management system that WONT allow you to damage them, yes they maybe double the cost but they will last for ages and ages
if you have 6 lead acids then to achieve the same amp hours of usable capacity you only need 2 lithium's phosphate on balance.
plus if you are running 2 x 3000 multiplus inverters then I think its a must that you change away from the lead acid ones.
you could be over cycling the lead acid ones as well as they are only good for 500 cycles on average.
the lithium's phosphate are usually good for 2000 down to 80 to 90 % discharge levels per cycle and then after the 2000 cycles they still have 80% of there original capacity.
I am a big fan of these especially on BOATS we have been putting them in now for 7 years and have still not had ONE failure in that time
Thge advantages for a boat are imense
Ie
1. they dont get hot at the levels a boat uses them even if air cons are used
2. they charge 20% quicker, ie on a lead acid if you discharge out say 100 amps for 1 hour then you charge 125 amps for 1 hour top bring them back up (not 100% correct but close enough)
Lithium phosphate - take 100amps out put back 105 amps
3. 1/4 the size and weight
4. you can discharge them down from 100% to 10% without damage DAILY if you want
5.they come with a BMS that balances the cels and shuts the system down if a undercharge happens or a overcharge
6. basically all the charging systems are compatible.
7. yopu can discharge and charge at very high currents without damage
8. in a lead acid the last 20% of a full charge takes 4 hrs, in a lithium phosphate its about 5 to 10 min, so the alternator puts out MAX amps until they are full. Not so with a lead acid
Ie you have 750 amp ours in 6 batteries max you should use is 50% so usable is 375
2 x 200 amp Lithium phosphate batteries would replace all those so 400 amp hrs of which the max you should use is 360 amp hrs
We just had the same issue. Two 48/5000/70 in parallel connected to a set of lithium battery. We were investigating why the Lithium battery BMS kept tripping on over-voltage. Using Ve.Config multi we lowered the Voltage set point on both unit and started to charge. The Quattro started to charge at 25A each. Current and voltage were verified by the BMS and voltmeter. Here is a screen shot of the system while charging:
You can see that the Quattro is pushing 25A while the voltage was 0.3V above the Absorption voltage. In prior incident the Quattro pushed the voltage as high as 55.89 V at which point the BMS disconnected the battery on overvoltage.
Each unit has a temperature sensor connected to them.
Unit are normally connected to a CCGX. They are not in the picture above to allow Ve.Config proper operation. Software version was 2753413.
We did a firmware upgrade of both unit to 2753433 and reloaded the set-up. It all worked as expected. Once the voltage reached the absorption voltage the Udc stayed exactly at the setpoint and the current decayed slowly.
Any idea if the firmware upgrade is/was the solution or is there something else happening?
Hi @Jmarc@aeandmengineering.com
It's not very clear what exactly is happening, but when troubleshooting, always update to the latest firmware (433 is very old).
Anyway: I don't see 'lithium batteries' selected in ve.config, so temperature compensation might be a reason for a higher charge voltage.
What lithium batteries are in this system?
Most 48 volt Lithium batteries have CANbus communication, and will take over the charge voltage settings over the configured settings in the inverters.
If you have more questions, please make a separate topic, as the topic your posting in is quite long (and about Lead/acid batteries) and your question is kind of buried away in it.
Hi Daniel,
Thank you for your response. The system is on a Greenline boat with Greenline batteries. Set-up is from factory as far as I know. I will review with them the choice of battery type.
Can you clarify the usage of the temperature compensation. It does look like that until rev 460, the Coefficient was fixed. I tried to use the table in appendix F to see if it could be the cause of our problem but I cannot really understand the chart. they are two curves and two scales apparently for 12 and 24V systems but no indication of what is what. Supposedly the voltage are set for 25 DegC but the chart only show multiples of 10. So it is almost impossible to even guess estimate the correction on a 48V system. in our case the temperature was 10 DegC. So 15 Deg below setpoint. If I interpret the chart this would mean about 1V correction at 48V. The overcharge exceeded 1.5V. Is my interpretation correct?
Reading the manual I also noticed that only one sensor should be used in a parallel system. What is the consequence of having two like we have?
But in general I agree with you there should not be any temperature compensation for lithium. In our case should we even have sensors? or does the Quattro use the measurement to provide High and low temperature protection when Lithium is selected?
I did realized later that 433 was not the latest it was the last one I installed a year ago. We will install 469 as soon as possible.
As far as I know the BMS used on this boat has canbus but it is not compatible with Victron protocol and it is not connected to the CCGX. Newer model are if I my information is correct.
second sensor doesn't do anything, the slave inverter does not control the charging.
do -not- use temp compensation on lithium batteries.
also you do you have a copy of the settings before the engineer went back in and checked it ? When it comes to warranty issues and what not, settings frequently get "changed" to what will cover their ass if it wasnt done correctly to begin with.
