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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