This is a copy of info at http://support.rollsbattery.com/support/solutions/articles/10376-deficit-cycling
> Deficit Cycling
>Modified on: Tue, 26 Aug, 2014 at 4:22 PM
>Rolls batteries have been designed to provide many cycles and therefore long life. This long life, however, is dependent on the correct charging regime.
To fully charge a lead acid battery, more ampere hours must be returned to it than have been drawn from it. This is not always possible in Renewable Energy applications as systems may rely solely on the Sun and Wind without backup power (generator/charger). In these instances the battery may not receive a full charge before it is discharged again. If this deficit is not corrected the battery will eventually sulphate and its capacity will deteriorate. To lessen these symptoms it is essential the battery is returned to a fully charged state at least once a month. The battery’s state of charge (SOC) can be checked using a combination of its voltage and specific gravity.
>If the batteries do not respond to normal charging, a course of equalization* will be required. This is in essence controlled overcharging in order to return the acid back into the electrolyte. Given that the acid is more dense than the water, no noticeable increase in the specific gravity will be noted until the gassing voltage has been reached (2.4VPC) and the two start to diffuse.
>NOTE: Hydrocaps must be removed during equalization.
14:50 Automatic update to version 4.4 and MPPT firmware to 1.3
The update created an anomaly in that the restart created a new day and thereby pushed back all the history by a day. So I have saved the data and cleared the history. So today's history is missing all data before 14:50
**15th Mar** 10:25 Morning Low 12.47 I must discover when the low reading is taken as yesterday's now reads 12.32 which was probably just before I kipped out and switched of inverter, computer and lights, but by mistake - left the rooter on all night
**14th Mar** 10:58 Morning Low 12.74 I haven't properly discovered when the low reading is taken a) just after midnight or b) as soon as the first light is recorded.
**13th Mar** Charging all day whilst using inverter Y=1.47Wh??
**12th Mar** Morning Low 12.70 charging ??
**11th Mar** Morning Low 12.66 charged Y=570Wh
**10th Mar** Morning Low 12.31 charged Y=760Wh
**9th Mar** Morning Low 12.50 charging Y=170Wh
**8th Mar** Morning Low 12.59 charged Y=1.550KWh Inc 3 and 1
**7th Mar** Morning Low 12.62 charging :: 09:44 15.46v connected Batts 3 and :: 09:52 V=15.44 set Abs to 15.64v
**6th Mar** Morning Low 12.32 charging :: 09:40 14.6v at 13.6a
**5th Mar** Morning Low 12.51 Little charge and incubator on all day :: Lowest V=12.24
**4th Mar** Low 12.35 Charge (Yield = 880w some to Batts 3 and 1) (incubator on all night till Noon)
**3rd Mar** Low 12.39 (incubator on all night till Noon)
**2nd Mar** Low 12.36 (incubator on all night till 10am)
**1st Mar** Low 12.47 (incubator on all night till 10am)
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**27th Feb** See https://disqus.com/home/discussion/victronwiki/victronconnect_manual_12/newest/
The problem arose that the Load reading was incorrect and didn't seem to work. On 28th I assessed it was reading some 0.6A low so if I wasn't using much it appeared as there was no load. I disconnected the MPPT after sunset on 28th Feb and all seems OK again.
**9th Feb** See image [histFeb9,gif] It seems as though as the current increases the MPPT becomes less efficient to a degree of 90%. 100w was used during the day of 1.21K yield though there was little load.
**Today the 8th Feb** I recorded 240W usage from the previous day, most I expect from the late afternoon through to midnight: so maybe 8hr @ 30w more than double what I expected. So today I have noted 30w usage by 16:00 and have loaded (comp, router, led4, phone) which is Victron Connect reads as 1.3 amp. Will leave on until midnight and expect 8 x 1.3 x 12.5w or 130w + 30w for a total of 160. Let's see :)
**23:50** consumption 130w total So 30w before 16:00 and 100W over 8 hours with computer router and led4 for 8 hours (12.5w/h :: 1A x 12.5V)
The most important part of the charge cycle is the absorption charge. Since the bulk charge only recharges the battery bank to an 70-80% level, the absorption charge completes the charging cycle.
If the absorption charge is not completed fully a part of the battery plates will not cycle and are likely to become sulfated, which in turn leads to shorter period of bulk charging until the absorption level is reached. If this is done often then the battery will loose capacity and it can be quite dramatic in that after a few months it may be reduced to 50% capacity. One process to remove sulfation is to over-charge or use an equalisation voltage once the battery appears charged.
Some chargers have a timer that allows the user to adjust the duration for the required time to return the battery to full charge. In order to set the correct time, a simple calculation is required. With the help of the 20 AH capacity, you can figure out the remaining charge required for the battery bank using the following equation:
If the actual absorption time is significantly less than as calculated below then the likelihood is that the battery has reduced capacity.
If a charger measures the standing voltage, for example after 12 hours of no load, it may adjust the time of absorption noting the battery is nearly fully charged. This again can be misleading as a sulfated battery not only will have reduced capacity but a higher resistance and so the voltage will appear high when there is little charge in terms of capacity.
t = 0.42 x (C/I) and with an 80% charge
t = Absorption Charge Time (Hours)
C = 20 hr Rated Capacity (AH) [ex: 2 strings x S-550 models (428 AH) = 856 AH rated capacity]
I = Charging Current (Amps) [charger output min 5% up to max 10% of 20 hr rate]
**Example** For a single 120Ah battery charging at 12amps that equates to 0.42*(120/12) which is 4.2 hours and I doubt I reach half of that. Given that the recommended voltage is over 15v I have developed quite a problem maybe using 14.5v Oops!
Good info on https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery :: wikipedia Lead acid battery