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Discussion Starter #1
As many patient people on Yahoo's US Electricar Group know, I've been unable
so far to get my pack charged via the onboard system. I wanted to make sure
there wasn't a fundamental problem with the pack itself, so I dropped it
this morning and did a bunch of cleaning and testing. Here are photobucket
pics: http://s182.photobucket.com/albums/x20/magellan35/

Turns out I have 50 Hawker PC925s. Are these the legendary Hawkers that are
generally considered ideal for a Prism? I hope so.

I found a few corroded connections (one severely) and cleaned them with
baking soda and water, a brush and a wet-dry vac, followed by a voltage
check of each battery (after sitting for 2 weeks uncharged). I read the
following voltages by series and sequence.

Series 1:
18) 9.89 (negative cable for series 1)
17) 11.98
16) 10.94
15) 11.99
14) 12.07
13) 11.06
7) 11.02
6) 12.08
5) 11.95
4) 12.00
3) 12.08 (connects to #25 via master pack switch)
25) 10.72
24) 11.96
23) 11.00
36) 10.05
35) 12.04
34) 12.00
33) 12.00
39) 12.08
38) 11.02
37) 12.05
50) 12.07
49) 12.05
48) 12.06
47) 12.05 (positive cable for series 1)

----------290V for entire series-----------

Series 2:
46) 12.16 (negative cable for series 2)
45) 12.24
44) 12.08
43) 12.18
42) 11.12
41) 10.17
40) 12.24
32) 7.84
31) 12.00
30) 12.20
29) 12.22
28) 12.25
27) 12.28
26) 12.20 (connects to #2 via master pack switch)
2) 12.24
1) 12.15
10) 12.32
9) 12.28
8) 12.18
12) 12.29
11) 11.08
22) 7.82
21) 12.23
20) 10.20
19) 12.22 (positive cable for series 2)

----------291V for entire series----------

It seems noteworthy that several of the weak batteries are those to which a
cable (rather than buss bar) is attached. Is there a certain logic to that?

Of course I'm concerned about batteries #22, 32, 18, 36, and several others
in the 10v range. I imagine #s 22, 32, and 18 at least are write-offs. Is it
likely that I can make any of them serviceable with individual charging?
I've had #32 on a little 12v "smart charger" for two hours now and still
only see 8.67v.

My game plan at the moment is to build zener-regs for the whole pack, charge
and/or change out the weakest batteries, clean and re-torque every
connection, hoist the pack up and reconnect the cables, find out why it
won't charge, fix that problem, charge, then drop the pack again, check
voltages, and perform discharge tests on each battery. Sound logical? What
should I add or do differently?

Lon Hull
Portland, OR

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Discussion Starter #2
Loni Hull wrote:
> US Electricar... unable to get my pack charged via the onboard
> system. I have 50 Hawker PC925s... I found a few corroded connections
> (one severely) and cleaned them with baking soda and water, a brush
> and a wet-dry vac

I'd say that battery has a leaking seal. Acid from inside the battery is
getting out and onto the external connection. It will keep coming back
until you replace that battery. If you keep using it, you need to coat
the exposed copper with something to protect it from the acid. Try
coating the terminal with solder or lead, or coat it with grease.

> after sitting for 2 weeks uncharged... I read the following voltages
> by series and sequence...

Ouch! These are pretty bad! If the pack was fully charged 2 weeks ago,
you should have seen voltages somewhere in the 12.6-13.0v range, with
perhaps a 0.1v difference between highest and lowest.

> several of the weak batteries are those to which a cable (rather than
> buss bar) is attached. Is there a certain logic to that?

I think that is a coincidence.

> Of course I'm concerned about batteries #22, 32, 18, 36, and several
> others in the 10v range. I imagine #s 22, 32, and 18 at least are
> write-offs.

Probably true. The only way to know for sure will be individual testing.
They are certainly very dead now. If they have only sat for 2 weeks that
way, there is some chance of recovery. But if they never did get fully
charged 2 weeks ago, and have been this dead for a long time, there is
little hope of recovering anything close to normal performance.

US Electricar tended to use very long strings of AGMs with no monitoring
or balancing at all. This quickly led to major differences in state of
charge between batteries. The ones with less charge go dead early: The
driver has no indication of this, and so "just keeps driving" -- and
these batteries are murdered. While charging, the batteries with more
charge get full early: Again, the charger has no indication of this, and
so "just keeps charging" -- and these batteries are murdered.

The result is that US Electricar packs don't last long. When you open a
pack like yours, you find significant difference between batteries. Some
still good (by luck), some destroyed from overcharging, and some
destroyed from excessively deep discharges.

I went through a pack of 40 Hawker G12V38Ah10C batteries from a US
Electricar pickup EV:

- 13 were good (had about 80% of their original capacity).
- 20 had died from overcharging (lost water as evidenced by lost
weight, and had excessive resistance due to grid corrosion by
the excessively strong electrolyte).
- 7 had bad cells (from overly deep discharges and reversed cells).

> Is it likely that I can make any of them serviceable with
> individual charging?

Yes (see above). Some will have survived. But you won't want to keep
some old ones in the pack and just replace others; you'd be starting out
with a large imbalance between batteries, and they will die even sooner.

Use the batteries that survive for some other use; a UPS power supply,
or lower-voltage EV, or something. I used the survivors from the above
pack for our BEST kid's EVs (see www.bestoutreach.com).

If you don't correct this design problem, it will recur again to murder
your new pack. You need to add some type of battery management system
that a) monitors each battery, so you and your charger KNOW when a
battery hits "empty" or "full"; and b) does something about the
condition before it murders batteries. Such a system could be as simple
as the zener-lamp regulators I've described before, or a full-blown BMS
like my Battery Balancer system.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Discussion Starter #3
I'm planning to build zener-regs for the pack this weekend. I'm too far
behind the learning curve to build anything as complex as your BBS (though I
hope to in time). On the other hand, if any of you BBS/BMS-building gurus
want to visit Portland and walk me through implementation, my house is your
house! I mean it. Pleeeeeease.....

I don't believe the pack has received a full charge for over a month, and
was driven after that charge to boot. So my plan has been to charge each
battery, perform discharge tests, see if the pack is hammered, and if not,
replace the worst offenders, install zener-regs, and attempt to maintain a
stable and reasonably healthy pack for a year. By then we'll have power from
Orbo and the Eternal Mother-Goddess of the Quantum Vacuum, right?
Riiiiiiiight... ;^)

Actually, I'd love to get my hands on an entirely different battery
chemistry by then, or at least Fireflies.

Lon Hull,
Portland, OR

----- Original Message -----
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, October 26, 2007 9:50 AM
Subject: Re: [EVDL] US Electricar Prism Battery Situation


> Loni Hull wrote:
>> US Electricar... unable to get my pack charged via the onboard
>> system. I have 50 Hawker PC925s... I found a few corroded connections
>> (one severely) and cleaned them with baking soda and water, a brush
>> and a wet-dry vac
>
> I'd say that battery has a leaking seal. Acid from inside the battery is
> getting out and onto the external connection. It will keep coming back
> until you replace that battery. If you keep using it, you need to coat
> the exposed copper with something to protect it from the acid. Try
> coating the terminal with solder or lead, or coat it with grease.
>
>> after sitting for 2 weeks uncharged... I read the following voltages
>> by series and sequence...
>
> Ouch! These are pretty bad! If the pack was fully charged 2 weeks ago,
> you should have seen voltages somewhere in the 12.6-13.0v range, with
> perhaps a 0.1v difference between highest and lowest.
>
>> several of the weak batteries are those to which a cable (rather than
>> buss bar) is attached. Is there a certain logic to that?
>
> I think that is a coincidence.
>
>> Of course I'm concerned about batteries #22, 32, 18, 36, and several
>> others in the 10v range. I imagine #s 22, 32, and 18 at least are
>> write-offs.
>
> Probably true. The only way to know for sure will be individual testing.
> They are certainly very dead now. If they have only sat for 2 weeks that
> way, there is some chance of recovery. But if they never did get fully
> charged 2 weeks ago, and have been this dead for a long time, there is
> little hope of recovering anything close to normal performance.
>
> US Electricar tended to use very long strings of AGMs with no monitoring
> or balancing at all. This quickly led to major differences in state of
> charge between batteries. The ones with less charge go dead early: The
> driver has no indication of this, and so "just keeps driving" -- and
> these batteries are murdered. While charging, the batteries with more
> charge get full early: Again, the charger has no indication of this, and
> so "just keeps charging" -- and these batteries are murdered.
>
> The result is that US Electricar packs don't last long. When you open a
> pack like yours, you find significant difference between batteries. Some
> still good (by luck), some destroyed from overcharging, and some
> destroyed from excessively deep discharges.
>
> I went through a pack of 40 Hawker G12V38Ah10C batteries from a US
> Electricar pickup EV:
>
> - 13 were good (had about 80% of their original capacity).
> - 20 had died from overcharging (lost water as evidenced by lost
> weight, and had excessive resistance due to grid corrosion by
> the excessively strong electrolyte).
> - 7 had bad cells (from overly deep discharges and reversed cells).
>
>> Is it likely that I can make any of them serviceable with
>> individual charging?
>
> Yes (see above). Some will have survived. But you won't want to keep
> some old ones in the pack and just replace others; you'd be starting out
> with a large imbalance between batteries, and they will die even sooner.
>
> Use the batteries that survive for some other use; a UPS power supply,
> or lower-voltage EV, or something. I used the survivors from the above
> pack for our BEST kid's EVs (see www.bestoutreach.com).
>
> If you don't correct this design problem, it will recur again to murder
> your new pack. You need to add some type of battery management system
> that a) monitors each battery, so you and your charger KNOW when a
> battery hits "empty" or "full"; and b) does something about the
> condition before it murders batteries. Such a system could be as simple
> as the zener-lamp regulators I've described before, or a full-blown BMS
> like my Battery Balancer system.
>
> --
> Ring the bells that still can ring
> Forget the perfect offering
> There is a crack in everything
> That's how the light gets in -- Leonard Cohen
> --
> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 

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Registered
Joined
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Discussion Starter #4
Loni wrote:
> my plan is been to charge each battery, perform discharge tests, see
> if the pack is hammered, and if not, replace the worst offenders,
> install zener-regs, and attempt to maintain a stable and reasonably
> healthy pack for a year.

The zener-lamp regs work well if the batteries are reasonably closely
balanced, so 1-2 amphours per day of correction is enough to keep them
balanced. In your situation, the batteries are likely to need more than
this.

> Actually, I'd love to get my hands on an entirely different battery
> chemistry by then, or at least Fireflies.

Don't we all! :)
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
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