Discussion in 'Electronics Homework Help' started by sudhakar, Aug 9, 2017.

1. ### sudhakar

20
1
Jun 19, 2017
I have 12v , 150 AH two battery connected in series for DG Self start motor,the battery charged condition total voltage 24.5 v.then once I started the DG the battery voltage suddenly get down 2v to 3v offer few seconds voltage raised gradually up to 22v. why voltage get down ?

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
Your batteries are flat, have a dead cell or two, or are sulphated.

Last edited: Aug 10, 2017
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3. ### kellys_eye

4,314
1,164
Jun 25, 2010
Two fully charged and 'good' lead acid batteries should read around 28V when fully charged. This will fall almost immediately the charging voltage is removed but should still remain over 25.5V to prove a 'good' battery.

If they are over 5 years old then change them anyway - more so if you rely heavily on the generator and need 'immediate' electrical backup.

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4. ### 73's de Edd

3,254
1,364
Aug 21, 2015
If DG is a diesel generator that would have to be for the very high initial current draw created by the starting up of the starter motor in order to get it up to cranking speed, along with the additional strain of the compression load of the diesel motor until it starts up.
Take yourself on a bicycle, doesn't it take one heck of a starting effort, compared to the relative ease after you are a meter down the road.
The battery pair just do not have enough capacity to hold

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5. ### sudhakar

20
1
Jun 19, 2017
Sir,
what is mean flat , sulphated ?
How I arrest the problem ?

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
Flat means not charged. A 12V lead acid battery which measures as only 12V is very close to discharged.

Sulphation is a problem with lead acid cells where the lead sulphate changes into lead sulphide (typically after being left discharged for an extended period). The battery loses capacity.

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7. ### sudhakar

20
1
Jun 19, 2017

Thank you sir,