DIY Electric Car Forums banner

1 - 2 of 2 Posts

·
Registered
Joined
·
70 Posts
Discussion Starter #1
Hello All,

I want to know what kind of battery management system or power distribution
system has be constructed in order to meet the following criteria, also what
cost will be incurred in it and can it be made at home,
1. instead of all batteries discharging equally together can there be a
system in which small sets of 2-3 batteries discharge more than the rest of
the pack without the overall pack voltage becoming down.
2. these small sets once discharged are disconnected and then are charged by
an external means like an alternator or solar panels
3. once fully charged they are again connected to the main pack and another
small set which has become discharged takes their place at the charging port
4. for this setup which battery technology is more suitable li-ion ni-mh
pb-acid ?

Need for the above setup
1. to make a conversion that can go atleast 120 miles @ 50 mph sustained
using pb-acid batteries off the shelf
2. this conversion will be the ultimate urban animal
3. if this is sucessful then to market the system to the global audience

Thank you
your guidance is most valued
Gulabrao
 

·
Registered
Joined
·
70 Posts
Discussion Starter #2
Hello Gulabrao,

Using pb-acid for 120 mile range with a maximum discharge to 50% DOD, which
is the preferred max discharge for long life and very little balancing, the
total vehicle weight will never catch up to the battery and net vehicle
weight.

If you can hold your maximum discharge to about 25% DOD, or 75% State of
Charge, then you will not need any battery management system. For the last
32 years, the maximum discharge rate is to 25% DOD for about 99% of the
time. The other 1% was testing once to 50% DOD.

This means I carry four times the AH battery I need for my range for a 25%
DOD, no BMS, and replacements average of 12 years.

For my vehicle of 7000 lbs, (use to weigh 8000 lbs with 300 AH batteries),
with 2400 lbs of batteries my range is limited to 50 miles at 50% DOD
maximum, but I recharge at 25% DOD.

To increase this range to 150 miles at 50 mph and only discharge the Pb-acid
to 50% for a 7000 lb EV, but the batteries would be 9600 lbs for a 1040 AH
cell plus the total weight of the vehicle would be about 14,000 lbs.

Even if reduce the net weight of the EV to 3500 lbs, it still takes 4320 lbs
of PB-acid which the vehicle total weight will now be about 7620 lbs using
520 AH battery. My first pack which was 90 cells 18 inches high, weigh 4500
lbs which was place in a 3200 lb vehicle had a range of 50 miles at 50% DOD
so it does make your 120 miles at 50 mph at 50% and these were proto type
cobalt cells which some of the li-ion cells are using now.

This EV before I received it, was test ran for 24 hours, running at a
average of 44 mph and fast charge every 60 minutes for 15 to 20 minutes at
charge amperes up to 200 amps. The EV ran 1056 miles in 24 hours with
maximum discharge rates of 30% to 50% DOD.

So the more batteries you carry, the weight go's up, the more power it takes
to move, the range barely increases.

Roland




----- Original Message -----
From: "gulabrao ingle" <[email protected]>
To: <[email protected]>
Sent: Saturday, July 28, 2007 12:16 AM
Subject: battery management and power distribution system design


> Hello All,
>
> I want to know what kind of battery management system or power
> distribution
> system has be constructed in order to meet the following criteria, also
> what
> cost will be incurred in it and can it be made at home,
> 1. instead of all batteries discharging equally together can there be a
> system in which small sets of 2-3 batteries discharge more than the rest
> of
> the pack without the overall pack voltage becoming down.
> 2. these small sets once discharged are disconnected and then are charged
> by
> an external means like an alternator or solar panels
> 3. once fully charged they are again connected to the main pack and
> another
> small set which has become discharged takes their place at the charging
> port
> 4. for this setup which battery technology is more suitable li-ion ni-mh
> pb-acid ?
>
> Need for the above setup
> 1. to make a conversion that can go atleast 120 miles @ 50 mph sustained
> using pb-acid batteries off the shelf
> 2. this conversion will be the ultimate urban animal
> 3. if this is sucessful then to market the system to the global audience
>
> Thank you
> your guidance is most valued
> Gulabrao
>
 
1 - 2 of 2 Posts
Top