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Discussion Starter · #1 ·
Re: [EVDL] Early Hawker deaths

To revive an old thread - I have a set of AGM batteries
that I know have lost water due to unbalanced charging.
I can see it also inside the covers over the cell-caps
that there are markings of gasses escaping.

So, I started by simply giving all cells a 20 ml spike of
distilled water, probably I want to continue to add water
until I no longer see the capacity grow.
Starting capacity (after several months floating the
battery at 13.7V just to make sure it was completely charged)
was only about 40 Ah, tested with a 30A load.
Original capacity of this battery is 110Ah and I would like to
get it back up above 80Ah if possible.
If the cells are seriously dry, then it is likely that I will
need to add much more water than 20 ml, as indicated in the
thread below where a 17 Ah Hawker was refilled with 10 to 20 ml
per cell.

Anybody have an idea how to check if an AGM has sufficient
water? Fill until water is dripping from the mat?
Note that this is a black case, so I can't see what is in the
bottom of the cell.

I have another question about a yellow top battery: does
anyone know how to pry that one open to see if watering may help
it to regain some capacity? It is down to about 10 Ah now.


Cor van de Water
Systems Architect
Proxim Wireless Corporation
Email: [email protected] Private:
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
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Second Life:

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Mike Phillips
Sent: Thursday, March 23, 2006 10:51 AM
To: Neon John
Subject: Early Hawker deaths (was Re: help choose best AGM battery for lawnmower)

Hi John,

I will somehow post the graph of my charger's CC/CV curve. I recorded it one day to see what it looked like. Maybe you will see some magic bullet in the numbers. But I don't see it. Other than maybe the fact that the ah's are way too small. The other odd thing is you won't find a USE truck with very many miles on it. So I think the problem is universal. With such a small volume of amps flowing back and forth I don't see why the water loss is so high.

Where can I post an Excel spread sheet?


--- In [email protected], Neon John <[email protected]> wrote:
> I've been using those 17ah Hawkers for years on scooter projects. I've
> found them to be bullet-proof with one exception and that is
> overcharging. You can very quickly kill one with too much voltage.
> You need to take a look at the charger's voltage. 1.6 amps is more
> than enough to kill a Hawker if there is sufficient voltage available
> to force that through a charged pack.
> Hawker is very explicit about charging voltage. If you follow their
> instructions exactly, the batteries will last a long time. I have two
> scooters using those 17ah Hawkers with over 4 years on them. I have
> several out in customers' hands.
> My GoBig scooter uses the 30 ah version and has over 3 years of daily
> use on them. Relatively severe duty, with >300 battery amps during
> acceleration being the norm and around 80 amps while cruising at full
> speed. This scooter has an E-meter and it shows that the pack still
> has its original capacity. I've never seen another battery that could
> come even close. Maybe the Optima, though I've not had a chance to
> use a set long-term.
> I killed a few Hawkers in the beginning while learning to take what
> they say about charging to heart. Once I started paying attention I
> never killed another one.
> John
> On Wed, 22 Mar 2006 20:44:08 -0000, "Mike Phillips"
> <[email protected]> wrote:
> >Hi John,
> >
> >I have experience to the contrary with the 16ah Hawkers. I own just
> >over 100 of them. I inherited them with my truck. They only had 400
> >miles of driving cycles on them when I got the vehicle. After having
> >tested all of them 3 times with a 40 amp load, they have very little
> >life left after 5000 miles. The charger only puts out 6.5 amps into
> >the pack. So average would be 1.625 amps per string. Most of them
> >were severely low on water. I bought 8 new ones to compare the old ones to.
> >Most took 10ml of water per cell to come back to nominal weight. Many
> >took 20ml of water per cell to acheive nominal weight. What would
> >cause such a loss of water with such light loads and charging?
> >
> >Since there are 4 strings of 26, none of the strings are exposed to
> >much of a load. The truck is limited to 200 amps draw from the pack.
> >So 50 amps per string is not much stress for a Hawker.
> >
> >So I think to their longevity depends on the way they are used. In my
> >truck they suck. The poor guy who put them in paid $7k. There may be
> >better uses for them than EV street driving.
> >
> >Mike
> >
> >
> >
> >
> >--- In [email protected], John Wayland <[email protected]> wrote:
> >>
> >> Dmitri Hurik wrote:
> >>
> >> > Ok, not exactly EV, but if anybody could help that would be
cool. I
> >> > need an AGM battery for starting an ICE lawnmower that has low
> >> > self-discharge and long life. Probably around the 12-14ah range.
> >> > I looked at the Hawker Odyssey 13ah.
> >>
> >>
> >> You'd be hard-pressed to find a better quality battery.
> >>
> >> > They claim it's really tough....
> >>
> >>
> >> They are 'extremely' tough. Search the EV list archives for my many
> >> posts about 'the Amazing Hawkers', and many posts from others
> >> the same.
> >>
> >>
> >> >can sustain being left at 0% charge for weeks/months and still
> >recover
> >> ....
> >>
> >>
> >> Hmmm...that's a tall claim. I 'have' had this exact battery taken
> >> to zero volts and left there for three months, and upon a
recharge, it
> >> came back without any cell reversals. Now, did it still have the
> >> capacity? I doubt it. You can't get away from permanent sulfation.
> >> In general, it's never good for any lead acid battery to do this.
> >>
> >>
> >> >and sit for years...
> >>
> >>
> >> This is absolutely true with Hawkers. I have quite a few 8 year old
> >> Hawker 16 ahr versions that have been sitting for long lengths of
> >> that still work well. Again though, there is going to be some
> >> sulfation that will occur if you let a battery sit so long unused
> >> uncharged, so they really can't sit for years and power-up to 100%
> >capacity.
> >>
> >>
> >> > ....but for $80+ seems like a bit much for just a 13ah battery.
> >>
> >>
> >> Not when that same battery can deliver 500+ amps repeatedly
without any
> >> noticeable degradation of the battery! 28 of the slightly larger
> >> version of this battery powered my race car at 750 amps for 13
> >> to a world record back in 2000. Hawker toughness and long life are
> >> legendary on this EVDL. The internal inter-cell straps are very
> >> and can sustain high currents without melting. Small Hawker
> >> can deliver HUGE currents and are worlds away from ordinary
> >batteries of
> >> the same size and weight. All of these traits may not be
applicable for
> >> you though, for merely starting a lawnmower.
> >>
> >> > Speaking of Hawker, what are people's general opinion on Hawker
> >> > batteries?
> >>
> >>
> >> See my web page about White Zombie, for how I feel about Hawker
> >batteries:
> >>
> >>
> >>
> >> See Ya......John Wayland
> >>
> >
> >
> >
> >
> >
> ---
> John De Armond
> See my website for my current email address
> Cleveland, Occupied TN A foolish consistency is the hobgoblin of
> little minds.-Ralph Waldo

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· Registered
72,624 Posts
Discussion Starter · #2 ·
Re: [EVDL] Early Hawker deaths

Cor van de Water wrote:
> I have a set of AGM batteries that I know have lost water due to
> unbalanced charging... Anybody have an idea how to check if an AGM
> has sufficient water?

When I've done it, I estimated the amount of water to add by weighing
good batteries, and adding enough to bring the bad ones up to the same
weight. It takes a good scale to do this, as we're talking about 1-2
ounces difference on a 60 lbs battery.

If the battery has be very low in water for a long time, it suffers from
serious grid corrosion. The internal resistance will have permanently
increased -- even after adding water and capacity returns, it may have
too much resistance to be useful.

Too much water only seems to cause excessive gassing. It just gasses
away the excess water, or may even vent liquid if it is really full.

> I have another question about a yellow top battery: Does anyone
> know how to pry that one open to see if watering may help it
> to regain some capacity?

The cover on an Optima is glued on pretty tightly, and there are only 2
vents for all 6 cells (they all share a common air space above the
cells). What I did is to drill a hole for a #6 screw over each cell. Add
water using this hole. Then plug the hole with a nylon or stainless
steel screw.
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,

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· Registered
72,624 Posts
Discussion Starter · #3 ·
Re: [EVDL] Early Hawker deaths

Don't add too much water. You don't want to see it dripping from the mat.

In VRLA batteries the proper electrolyte fill volume is essential to the
recombinant nature of the battery. Usually the amount of electrolyte in a VRLA
is enough to be absorbed into the separator at an 80-95% level.

>From the factory, enough electrolyte is added to react with the active lead
material to provide the desired discharge capacity. Any more electrolyte
lowers the recombination efficiency.

VRLA batteries are exceptional in their design. But as good as VRLA
batteries are, one unfortunate characteristic is that very small changes in cell
material and electrolyte volume can greatly alter the recombination behavior and
charging characteristics of the battery.

Most EV list members using VRLA batteries are all too familiar with the
unfortunate charging characteristics and the need for a good battery management

Lawson Huntley

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