The ampere-hour rating of a battery is the measure on how many amperes it

can draw in a specific amount of time. The standard rating which is choose

by battery companies, is how long it takes to discharge a battery to 0%

State OF Charge (SOC) or is the same as 100% Depth Of Discharge (DOD).

For example:

A battery that can be discharge at 5 amperes at 20 hours, this is a 5 Amps x

20 hrs = 100 AH battery.

A reserved minute rating at 20 hours would be 20 hrs x 60 mins = 1200

reserved minutes.

Now as you increase the ampere draw of the battery, the ampere-hour rating

of the battery decreases. If you increase the the ampere load of the battery

to about 20 amperes, it may only deliver 20 amps for 4 hours, which is a

actual capacity of 80 ampere-hours.

You can convert the reserved minutes that is list for a battery. For

example, a battery with a 100 AH rating with a listed Reserved Minutes of

180 minutes for a 25 amp draw would be about:

180 min / 60 = 3 hrs

3hr x 25 amps = 75 amp-hrs

So you see, when the ampere draw of a battery goes up, you have less

ampere-hour available.

The average ampere draw for a EV is about 75 battery amperes. The reserved

minutes listed for a 100 Ah battery is about 60 minutes at 75 amps which is

about one third the time at 25 reserved minutes.

My Trojan T-145's is a 260 AH at a 20 hr rate battery with a 145 reserved

minutes at 75 amps. The actual ampere-hour would be:

145 mins / 60 = 2.41 hrs

2.41 hrs x 75 amps = 181.25 AH

It is best not to discharge a Pb-Acid battery below 50% DOD, so the maximum

ampere-hour draw out the battery would be 90 AH. For a long life I normally

charge at at 120 ampere-hour remaining in the battery or about 25 DOD%.

Roland

----- Original Message -----

From: "gulabrao ingle" <xx[email protected]>

To: <[email protected]>

Sent: Monday, July 30, 2007 12:12 AM

Subject: what does Ah or ampere hour signify

> Hello All

>

> What does Ampere hour signify ?

>

> does a higher ah rating equals more range , what is the ideal Ah

> rating for an EV

>

>

> Thanks

> Gulabrao

>

>