Battery discharge curves and policy - USS Tambor

copernico · 10-30-17, 06:18 AM

I have accurately measured battery times in SH4's USS Tambor submarine.

The recharge time is mostly linear: from Discharged to Fully Charged, if the submarine is running at 1/3 speed, it takes 3:30 hours. If the speed is faster, it may take twice as much, or more.

The discharge time is instead very variable. It depends, of course, on speed, and the curves are significantly different for the different speeds: see the attached chart

or else the details below. Very importantly, when the batteries are not fully charged the high speeds are no longer attainable. Therefore, the difference in discharge rate between the different "telegraph" speeds is mainly for fresh batteries: when the batteries are down to 25% speed does not exceed 5kt anyway, at 10% you just have 2kt and when fully discharged 1.2kt. As a consequence, although the curves for speeds 1/2, 2/3 and Standard are very different, the curves for Standard, Full and Flank are quite similar. Discharge and speed curves are made up of linear segments. Find below an abridged result for the different speeds, starting with batteries fully charged 100% and counting time starting from 00:00 hours.

The format of the following lies is as follows:
speed: xx.xx yyy% zzkt. xx.xx yyy% zzkt. xx.xx yyy% zzkt. and so on, where
speed is telegraph, xx.xx is hours:minutes, yyy% is battery charge and zzkt is the actual speed in knots.

1/3: 0:00 100% 3.6kt. 12:00 25% 3.6kt. 16:30 0% 1.2kt.

2/3: 0:00 100% 5.2kt. 4:30 25% 5.2kt. 8:30 0% 1.2kt.

Standard: 0:00 100% 7.4kt. 0:30 75% 7.4kt. 1:00 50% 6.7kt. 1:55 25% 4.9kt. 4:10 10% 2.3kt. 6:00 0% 1.2kt.

Full: 0:00 100% 8.5kt. 0:40 50% 8.0kt. 1:30 25% 4.9kt. 3:45 10% 2.1kt. 5:30 0% 1.2kt.

Flank: 0:00 100% 9.1kt. 0:40 50% 7.5kt (less than Full!). Then same data as Full.

Policy:
1. When submerged, batteries provide the best mileage at 1/3, decreasing with higher speeds. Use Standard, Full and Flank for relatively short bursts only, or else in just 2 hours you will be down to 4kt and in a further 4 hrs you will be fully discharged.
2. Flank gives you just 0.6kt more than Full, but after just 30 min. you will be worse off! So use Flank only for emergency escapes during less than 20 min., say.
3. Sunset: as night closes in, as soon as the batteries are at 0%, set speed at 1/3 and surface to recharge. After 3:30 hours your batteries are fully recharged and you can set any faster speed since you are emerged.
4. Sunrise: as you dive to periscope depth to avoid detection, set speed at 1/3 to have batteries lasting until sunset (just!). While submerged use faster speeds only for short bursts: this may later force you to stay All Stop until sunset, with no possibility to evade any attacks.

10-30-17, 06:18 AM	#1
copernico Bilge Rat Join Date: Oct 2017 Location: Italy Posts: 1 Downloads: 4 Uploads: 0	Battery discharge curves and policy - USS Tambor I have accurately measured battery times in SH4's USS Tambor submarine. The recharge time is mostly linear: from Discharged to Fully Charged, if the submarine is running at 1/3 speed, it takes 3:30 hours. If the speed is faster, it may take twice as much, or more. The discharge time is instead very variable. It depends, of course, on speed, and the curves are significantly different for the different speeds: see the attached chart or else the details below. Very importantly, when the batteries are not fully charged the high speeds are no longer attainable. Therefore, the difference in discharge rate between the different "telegraph" speeds is mainly for fresh batteries: when the batteries are down to 25% speed does not exceed 5kt anyway, at 10% you just have 2kt and when fully discharged 1.2kt. As a consequence, although the curves for speeds 1/2, 2/3 and Standard are very different, the curves for Standard, Full and Flank are quite similar. Discharge and speed curves are made up of linear segments. Find below an abridged result for the different speeds, starting with batteries fully charged 100% and counting time starting from 00:00 hours. The format of the following lies is as follows: speed: xx.xx yyy% zzkt. xx.xx yyy% zzkt. xx.xx yyy% zzkt. and so on, where speed is telegraph, xx.xx is hours:minutes, yyy% is battery charge and zzkt is the actual speed in knots. 1/3: 0:00 100% 3.6kt. 12:00 25% 3.6kt. 16:30 0% 1.2kt. 2/3: 0:00 100% 5.2kt. 4:30 25% 5.2kt. 8:30 0% 1.2kt. Standard: 0:00 100% 7.4kt. 0:30 75% 7.4kt. 1:00 50% 6.7kt. 1:55 25% 4.9kt. 4:10 10% 2.3kt. 6:00 0% 1.2kt. Full: 0:00 100% 8.5kt. 0:40 50% 8.0kt. 1:30 25% 4.9kt. 3:45 10% 2.1kt. 5:30 0% 1.2kt. Flank: 0:00 100% 9.1kt. 0:40 50% 7.5kt (less than Full!). Then same data as Full. Policy: 1. When submerged, batteries provide the best mileage at 1/3, decreasing with higher speeds. Use Standard, Full and Flank for relatively short bursts only, or else in just 2 hours you will be down to 4kt and in a further 4 hrs you will be fully discharged. 2. Flank gives you just 0.6kt more than Full, but after just 30 min. you will be worse off! So use Flank only for emergency escapes during less than 20 min., say. 3. Sunset: as night closes in, as soon as the batteries are at 0%, set speed at 1/3 and surface to recharge. After 3:30 hours your batteries are fully recharged and you can set any faster speed since you are emerged. 4. Sunrise: as you dive to periscope depth to avoid detection, set speed at 1/3 to have batteries lasting until sunset (just!). While submerged use faster speeds only for short bursts: this may later force you to stay All Stop until sunset, with no possibility to evade any attacks.