Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

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EV_dub
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Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Wed Nov 09, 2011 12:23 pm

Thought I might share my battery restoration experience on here.

So I have 8 100ah mre units 6v from a Berlingo.

They have been stood for a while and showing varying voltages from 4.5-6v

A quick test with my 100amp battery tester shows promising results without any major voltage sag.

First of all I have slowly taken each battery down to 3v (0.6v per cell) using some 1.4-ohm resistors.

According to the saft manual a 6amp 21hour recharge is required for reconditioning
Last edited by EV_dub on Wed Nov 09, 2011 3:37 pm, edited 2 times in total.
1993 Veedub Golf, 156v, 1200A, 150ah's

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EV_dub
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Re: Saft Ni-Cd MRE battery restoration, (berlingo batts)

Postby EV_dub » Wed Nov 09, 2011 12:30 pm

Charged the first two Batts with 6amps constant current for 21hours.

After a few a hours to rest they are both holding 6.8volts

Again I tested them with 100amps load tester for 2 mins and both hold 6volts under load :D

6 more batteries to go!!

I forgot to mention I might be selling these as I dont have a project in mind for them. if you are interested, please express an interest.
1993 Veedub Golf, 156v, 1200A, 150ah's

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ChrisB
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Re: Saft Ni-Cd MRE battery restoration, (berlingo batts)

Postby ChrisB » Thu Nov 10, 2011 6:16 pm

EV_dub wrote:Again I tested them with 100amps load tester for 2 mins and both hold 6volts under load :D


So they should :wink: load them at that level for +15mins and we might be impressed :wink: you'll need some cooling set up on them I suspect or you could cook them a tadge, in my Berlingo its not unusual to see discharge currents @ 50mph of +50amps for 1/2 hr when I'm romping down the motorway, so 2mins @ 100amps isnt really going to give any real judge of capacity or condition. From memory you need to pull about 30amps for 3hrs to get an idea of their true capacity

TBH the safts are pretty robust units and from what I've found generally only fail due to a physical failer rather than just expiring due to use or being left, in the main its the pre 2000 units but I've currently got a post 2000 unit which has got some sort of physical failure :roll:

ChrisB
I reject reality and substitute my own !!!!!!

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EV_dub
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Re: Saft Ni-Cd MRE battery restoration, (berlingo batts)

Postby EV_dub » Thu Nov 10, 2011 6:42 pm

ChrisB wrote:
EV_dub wrote:Again I tested them with 100amps load tester for 2 mins and both hold 6volts under load :D


:wink: load them at that level for +15mins and we might be impressed ChrisB


Yes, a capacity test will be next just as soon as I get them all at the same level.

The 3hr rate is 100ah so a 30 amp for 3 hrs is close

Might try and rig up a 30amp load or I will time them with the 100 amp loads with pumped water cooling!

I could parallel 3 batts with the 100amp load for 3 hours,

The batts are 2001!
1993 Veedub Golf, 156v, 1200A, 150ah's

Grumpy-b
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby Grumpy-b » Thu Nov 10, 2011 7:55 pm

Most seem to die with complete cell failure, or have an initially higher than normal voltage then lose a cell at about 50% charge. Having had well discharged cells and charged them, they often take a charge to a higher initial voltage then still fail, under load. I have probably about 40+ duff batteries with various numbers of dead cells. Once they fail in use they are genarally not much good. Except as a battery with a duff cell, you could string a load together and use them for static power I guess.

I dont think I will be attempting to recondition any of the ones I have.

Grumpy-b

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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Thu Nov 10, 2011 9:03 pm

Yes its frustrating these are sealed units.

The saft batteries used in aircraft are made up of individual cells. We test these by discharging each cell with c1 rating and then gently to 0.6v and cap off each cell before they go into reverse polarity. Also we are able to replace only the weak cells instead of the complete battery.

With Nicads, initially there is a huge number of very tiny crystals on the surface of the positive plate, but due to a gradual change in the nickel oxide/hydroxide crystal structure, (usualy from under discharging, "memory effect") these are gradually replaced by much larger crystals. This Reduces the surface area of plate to the electrolyte.
Reconditioning shrinks the crystals on the surface of the plates and dissolve any dendrites that may have formed
However this process wont achieve much if the batteries porous separators have been seriously damaged by
dendrite growth.

There is a risk with these sealed batteries, that they may have damaged cells although I'm hopefull and we'll just have to see with further testing!!
1993 Veedub Golf, 156v, 1200A, 150ah's

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timpootle
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby timpootle » Fri Nov 11, 2011 12:09 pm

Good work! What's your day-job? Sound's like you know plenty about aircraft Ni-Cads.

(I'm an engineer for Monarch here at Manchester. Before that BA Citi-express, which got bought by FlyBe after I left.)
Tim Crumpton

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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Fri Nov 11, 2011 2:14 pm

Hi Tim,

Well i'm no expert with Ni-Cads, althought I did a stint in the battery bay at work so I know a little.

I'm a Mechanic for Flybe in Exeter.

I know a couple of our guys looking for jobs with a Monarch, they must be paying better :)

Whats your role, are you licenced? You must be an expert on emb145's?
1993 Veedub Golf, 156v, 1200A, 150ah's

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EV_dub
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby EV_dub » Sat Nov 12, 2011 1:22 pm

A quick update:

Selected 3 batts within the same voltage range (6.8v) and carried out capacity test:

100amp load over 3 batts in parallel for approx 33amps on each

starting voltage under load = 6.3volts

After one hour under load= 6volts

after 2hrs= 5.8volts under load

2.5 hrs = 5.5v under load

2hrs 40mins = 4.8v under load

It appears they held up well untill after 2hrs 40 mins . having taken them off load at this point they climbed to between 5.5 and 5.8volts about 1.1v per cell

seems quite good to me.
1993 Veedub Golf, 156v, 1200A, 150ah's

Grumpy-b
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Re: Saft Ni-Cd MRE battery reconditioning, (berlingo batts)

Postby Grumpy-b » Sat Nov 12, 2011 4:30 pm

Looks like one duff cell in each to me. Thats a similar result to a failing cell.

Grumpy-b


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