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Author Topic: Battery health check  (Read 4416 times)
Amy
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« on: November 02, 2010, 06:31:06 PM »

Ive had my batteries for several months now, and due to hold ups beyond my control, they still sit in the shed awaiting installation.
Ive been growing more concerned of late that they may be discharging somehow because of the bubbling sounds issuing forth.
I know its certain death for a battery to remain in storage in a depleted state.

I did check the voltage of all the cells several months ago and they were all above 2v 
I have rechecked them today and 18 were still showing 2.1, 2.2v etc but 6 were showing 1.97, 1.98, 1.96, 1.99, etc.

Can it be safe to leave them for another few weeks in this state before I get them installed in their new home and finally connected to the combi charger for a good old charge?
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johnrae
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« Reply #1 on: November 02, 2010, 06:45:33 PM »

Hi Amy

I'd get them on charge immediately since they should never drop below 2 volts when sitting idle. 
Do an SG check to confirm their state of charge.
The differences in cell voltages are a bit of a concern.
24 cells, 48 volts.  I believe you are aiming at a 12 volt system, so that presumably 4 separate banks.
Do not charge the cells as banks in parallel since the low cells may be "lazy" and won't take a charge if there's an alternative path for the current to flow.
Assign each cell it's own identification number and log data with respect to volts and SG before and as you charge them.
Some cells may come up quicker than others and the "slow" ones may need further charging to get their SG up.
Large croc clips will be good enough to do the cell interconnections if you don't yet have the proper connectors and cables, but better to use proper battery pole type  terminals even if you don't yet have the correct inter-cell cables.
Charge rate should not exceed C/7 but there is no lower limit, within reason, so don't be too bothered if you cannot meet the C/7 rating.
jack
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profp
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« Reply #2 on: November 02, 2010, 09:22:58 PM »

Large croc clips will be good enough to do the cell interconnections if you don't yet have the proper connectors and cables, but better to use proper battery pole type  terminals even if you don't yet have the correct inter-cell cables.

When I interconnected mine, I was originally going to tap & die each cell - turns out the lead is so soft that it isn't necessary - drill a slightly undersized hole and give an 8mm bolt a tap with a hammer to get it started, it then cuts its own thread.

P.
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biff
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« Reply #3 on: November 03, 2010, 01:26:36 AM »

hi amy,
    you have to be carefull ,when taking a charge they bubble and give of a gas which is highly explosive,so work in a well vented area with no naked flames and if you have to do some drilling etc,flood the surrounding cells with clean rainwater.
       biff
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johnrae
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« Reply #4 on: November 03, 2010, 07:01:49 AM »

Perhaps I should clarify that the use of croc clips was suggested only as a temporary measure to permit you to get them on charge as soon as possible.
jack
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profp
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« Reply #5 on: November 03, 2010, 09:49:38 AM »

    you have to be carefull ,when taking a charge they bubble and give of a gas which is highly explosive,so work in a well vented area with no naked flames and if you have to do some drilling etc,flood the surrounding cells with clean rainwater.

Probably missing something here, but I don't follow the logic of flooding the surrounding cells as hydrogen gas given off during charging is lighter than air, so shouldn't accumulate in the top of the cells?

P.
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johnrae
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« Reply #6 on: November 03, 2010, 04:00:07 PM »

Maybe he means do it outside whilst its raining   wackoold

Given the choice I'd avoid drilling into battery posts for whatever reason.  Getting the proper terminations is the better way to go.

Amy, bear in mind that battery terminals (well the connectors actually) and sea air don't go well together so apply plenty of vaseline to prevent corrosion and keep them healthy.  Going into the chemists and asking for a kilo tub of vaseline always draws a smile.  norfolk

jack
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Amy
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« Reply #7 on: November 03, 2010, 06:18:42 PM »

Maybe he means do it outside whilst its raining   wackoold

Given the choice I'd avoid drilling into battery posts for whatever reason.  Getting the proper terminations is the better way to go.

Amy, bear in mind that battery terminals (well the connectors actually) and sea air don't go well together so apply plenty of vaseline to prevent corrosion and keep them healthy.  Going into the chemists and asking for a kilo tub of vaseline always draws a smile.  norfolk

jack

Haha, always a good way to embarrass someone

Two nightwatchmen are having a cuppa and one asks the other how he keeps his tea so hot.

The guys says, go into the chemist and ask for one of these flasks, its called a durex. Next day the other guy goes into boots and asks for a durex and the girl says how big and he says, its got to hold a quart, im on all night hysteria
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Amy
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« Reply #8 on: November 03, 2010, 06:24:58 PM »

I drilled the posts a few months ago and inserted 6mm screw in threads. Im busting a gut this week to be in a position to get the cells installed ASAP
Ive got a length of 5x19mm copper bar to make cell links which I will cut to length and drill. Once they are installed in the box ive made, the lid will vent into a 4'' pipe leading to the extractor fan so all gas will exit the boat
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johnrae
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« Reply #9 on: November 03, 2010, 06:49:59 PM »

Just a minor point.  If the links are reasonable length I'd suggest fitting heat shrink on so's you minimise the area exposed to dropping a spanner onto.  Shrink onto the full length then cut back to clear the terminal posts.  What type of clamp bolts & nuts are you using on the posts  brass or stainless steel.  I'd recommend brass.

jack
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biff
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« Reply #10 on: November 03, 2010, 08:06:59 PM »

flooding the surrounding cells with rainwater does sound a bit extreme,,,,, Grin
      i agree lads, however and however i got this advice from a supplier of forklifts and forklift batteries, you see it is not quite as straightforward as it seems,for some reason this guy was very convincing ,well he showed me the results of an explosion in his workshop,the head of the cell goes straight up with a very convincing bang showering everyone within range in acid,his workshop is about 20ft high by 60ft x 40ft(full of forklifts and batts)he showed me the tracks where the cell hit the box profile, his brother who was listening became very excited, facepalmthey left me in no doubt.
    they were drilling with a hollow hole cutter to replace 2 dead cells,this method leaves a nice round post the same as the normal battery post.it should not have blown up, but it did,i think you will find this is not so uncommon,
        soooooooo,, yes go out side and do it in the rain or bring the rain inside but if you do it without taking precautions,well its a bit like that russian game they play with the one bullit and gun. wackoold
                 biff
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Baz
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« Reply #11 on: November 03, 2010, 10:50:38 PM »

Bit of compressed air blast is what you really need.
Brass and copper will corrode like mad. Try and tin it very thinly then cover with lead foil. Or fold up sheet lead and hammer to make a big thick bar.
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tony.
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« Reply #12 on: November 03, 2010, 10:59:09 PM »

I drilled the posts a few months ago and inserted 6mm screw in threads. Im busting a gut this week to be in a position to get the cells installed ASAP
Ive got a length of 5x19mm copper bar to make cell links which I will cut to length and drill. Once they are installed in the box ive made, the lid will vent into a 4'' pipe leading to the extractor fan so all gas will exit the boat

Amy,

Not sure if the fan and gases are a good combination.

Caboom

Possible just a passive vent

Tony
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Philip R
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« Reply #13 on: November 04, 2010, 12:49:13 AM »

Hi Amy,
I would not recommend you boxing up your battery, for the simple reason, as Tony has just mentioned, you would be relying on forced ventilation only to dissipate both heat and any gases released from the battery.
In my former ESI employment, I learned of a fatal accident involving a UPS battery which was mounted in a cubicle that was not fit for purpose. The charger float voltage was too high, the battery gassed and the gasses built up in the compartment. Maintenance staff responded to a plant alarm, they were sent to maintain the device, on switching off, set off an explosion. The result was a fatality and serious injury. Since then, fault finding has adopted much better risk assessment and hazard mitigation procedures, to hopefully reduce chances of such eventualities resulting in the future.

Subsequently, I worked with the gentleman whom was involved with the subsequent panel of enquiry.

I cannot quote the relavent BS an it has now been superceded by a BSEN. Google will help here. More to the point, I no longer have access to these updated docs. Basically try to rely on passive ventilation, witha some additional using a fan, thus offering good dilution, high and low level vents to allow passage of hydrogen from the containment.

If you are boxing it up, follow DSEAR (Dangerous Substances & Explosive Atmosphers regulations) ( UK subset of Euro ATEX Regs) guidelines and a suitably EX rated equipment.

In addition to Jacks comments regarding connected up cells, Insulate your spanner as well as your intercell connectors.
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Outtasight
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« Reply #14 on: November 21, 2010, 12:56:17 AM »


I did check the voltage of all the cells several months ago and they were all above 2v 
I have rechecked them today and 18 were still showing 2.1, 2.2v etc but 6 were showing 1.97, 1.98, 1.96, 1.99, etc.

Can it be safe to leave them for another few weeks in this state before I get them installed in their new home and finally connected to the combi charger for a good old charge?

The 6 that are reading less than 2V could already be toast...  At about 1.98V that means a 12V pack would only be 11.88V at long term rest...  12.8V would have been "full".  11.88V is going to be something like 60-70% discharged.  As most have faired better, there may be some dodgy things about the weak ones. Top culprits would be tracking across the top of the cell from dirt and moisture that is leeching current or an internal short due to buckled plates or sludge at the bottom of the cell reaching the bottoms of the plates.

Flooded antimony cells can lose in the region of 10-30% of their charge per month of standing at 25C.  If it's been hot in the shed, they'll run down faster.  There isn't a row of cells that is warm for some reason like the sun shining on them or the wall that they are resting against?

As they've been sitting at a low state of charge for more than a few days you'll have to slow charge them (C/20 or slower).  A fast charge won't break down the sulphate so well and will just make them gas.
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