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Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: woodi on March 05, 2015, 12:35:31 PM



Title: Charge setup for traction batteries
Post by: woodi on March 05, 2015, 12:35:31 PM
Having become proud parent to these traction batteries - 12x 2v, I now have the joy of trying to keep them alive as long as possible. My biggest BlueSolar controller allows for auto equalisation, should I use it, or do them manually from time to time. I've also got 3 controllers worth of charge settings to play with, so any tips on best voltage settings and general nurturing?


Title: Re: Charge setup for traction batteries
Post by: rogeriko on March 05, 2015, 08:35:10 PM
You will be lucky to even charge them in the winter, maybe in the summer you might get close once or twice. 4kw of PV in the UK is not a lot of power. 1000Ah of batteries is a lot of power, if they are low it will take about 3 days to charge them with the inverter off.  Run a generator early in the morning to bulk charge them with the inverter and then let the PV finish them off throughout the day. Equalise means bubbling hard, that alone will take over 10A just to maintain.


Title: Re: Charge setup for traction batteries
Post by: woodi on March 05, 2015, 09:14:05 PM
Ah, we'll never take them below 80%, and I'd say most of the time 90%. Here on a not-terribly-sunny day in Northern Ireland they were running 98% most of the time. I've found a 3kw turbine to see us through the winter months. Our consumption is low, but I want to make sure we have capacity when we need it, and that we don't have to spend a fortune replacing them earlier than is necessary.


Title: Re: Charge setup for traction batteries
Post by: rogeriko on March 05, 2015, 09:52:57 PM
Now we are talking Wind Turbines are the only way to go.      My house a few winters ago. exhappy: exhappy:


Title: Re: Charge setup for traction batteries
Post by: woodi on March 06, 2015, 06:58:04 AM
Very nice. Got any advice about charging voltages and absorbtion?


Title: Re: Charge setup for traction batteries
Post by: billi on March 06, 2015, 09:12:03 AM
Woodi , have a look in the Victron Multi plus  charger set up  menu   they even have a  traction cell charging  setting  if charged through the Victron Multi plus
from the VE config menue ....
Quote
Use tubular plate traction battery curve
If this option is checked the charge curve will be adapted in such a way that when during absorption the current gets as low as 10% of the bulk current, the current is kept at 10% until the absorption phase is ended or the battery voltage reaches 17V (for a 12V system).

This is used for tubular plate traction batteries. In the figure below it is called TPTB mode.


  for me , i have my absorbtion voltage set to 29.6 Volt and 3 hours .... i cannot tell you if that is perfect , but it seems matching to the batterysize and PV i have , but  i need about 50 l water a year ,  if you have a new battery i would advice to get a electrolyte steering air pump  to reduce water usage and full charged time

Billi
 



Title: Re: Charge setup for traction batteries
Post by: woodi on March 06, 2015, 09:16:37 AM
No mains/genny at the moment so just charging through the PV controller(s), the biggest of which does have a tubular plate setting - just go with its default then, do you reckon?


Title: Re: Charge setup for traction batteries
Post by: freddyuk on March 06, 2015, 08:53:35 PM
I requested battery supplier to check which algorithm would suit and they confirmed that 4 or 5 on the Blue Solar 150/70 would be ok. The charging current should never exceed 30 amps. This is on 2v  4IPZS460 Traction batteries. Their other comments below:
 
The charging current has to be restricted because the Lead-Acid battery can accept charge (electrical to chemical energy conversion) at a rate depending upon its state of charge. When recharging from 80% discharged state we can pump in up to 17%- 18% of AH Capacity (in Amps) until the system voltage rises to about 2.35V/cells. At this point the battery is around 70% charged. Beyond this voltage the battery’s charge acceptance drops down and we have to restrict the current to 6-7% of AH Capacity. Higher current input will be wasted and the waste energy will heat the battery up beyond the acceptable 45oC as well as cause excess electrolysis of water in the electrolyte and excess H2 and O2 gases will be evolved – consequently the battery will need frequent water topping-up, which is not desirable.
 
Note: To maintain 7% charge current after 2.35V/cell, the charger should be designed to boost the voltage to 2.6V/cell.
 
This is how lead-acid batteries recharge and Forklift batteries are the most cost effective compromise for cyclic use of batteries.
OPzS has higher electrolyte content and can be charged at slightly higher rates, But they cost double or more and have about 1.5 times or so life expectancy compared to Forklift batteries.
 
If Constant current charge is used, i.e. the current is maintained fixed all through the recharge period, through a feedback circuit in the charger, then the charge current should be restricted to 7% max. For 345AH battey that would be 24 Amps.
80% of 345AH + 10% = 304AH needs to be put in after 80% discharge. Time = 304/24 = 12.7 hours.
 
2 Step Constant or taper chargers are available which can recharge from 80% DOD in 7-8 hours. But that will be possible only if the charger is connected to AC mains or the generator. Solar PV power is temperamental.

Equalise charge up to 2.4V/cell at least (57.6V for 24 cells in series) is recommended every 30 days. If charger permits, the voltage should be raised to 2.6V/cell.
 
Caution: Low current discharge for prolonged period without recharge can actually result in deep-discharging the battery.
If the battery is not ‘fully recharged’ periodically or after a discharge, or if the battery is left in a partial state of charge for many days, it will irreversibly lose some AH Capacity progressively and eventually premature failure is possible.
 
Hope this helps.

 


Title: Re: Charge setup for traction batteries
Post by: woodi on March 06, 2015, 09:53:10 PM
Brilliant Freddyuk, thanks for that. Most helpful indeed. They are cycled back up to 100% every day at some point, and I'll set the BlueSolar up for them.