Author Topic: Fork truck help needed  (Read 914 times)

Offline John Stevenson

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Fork truck help needed
« on: February 08, 2017, 04:47:33 PM »
We have some clever guys and gals on this forum and many have big boys toys so here goes.

Got this Komatsu fork truck, battery / electric and it runs on 48 volts from 24 2V cells.
Charger is a Varta  but I've googles it and can't find any reference to fork truck chargers.

When I plug it in and switch on it reads L43 on the display which with time goes down as I was told that's how it works and has done in the past although i have only had this machine 3 months or so.

At the moment the battery indicator on the truck is flashing red so bunged it on change today and it got down to L25 last but one time I looked.
Just before knock off I went to switch it off and it was reading H 0 [ zero ] Uncoupled it and plugged the truck back in but still reading flashing red on the battery meter.

The batteries haven't seemed bad on this so suspect the charger.
4 toggle switches on the front with no idea what they are for but it only reads the L display in one mode so left it in that mode.

Anyone got any experience of these chargers ?

Second question.
I still have a 48v charger off the old truck which had the exact same batteries as seeing as it only charges the batteries off the truck as it were can't see why this charger won't work ?
Problem is it's the wrong stab in fitting if that's the correct term. Fitting is clearly marked + and - and the + cable has a bit of red tape round it but whilst pi$$ing about getting this fitting off so did the tape, so now got two heavy black leads.

Ok no sweat, stick a meter on the end and switch on ? 

No don't work, these must need to have the battery load on them before the charger will switch on. So what to do 50% chance I connect it wrong and blow the batteries.
I could climb up into the hay loft where it is, dig it out from 27496 years of accummlated junk and get the cover off in the hopes that the charger end of the cables is marked.

Any easier ways ?

Am I right in thinking that our own and famous Mr Wilson is a Fork Truck guru ?
John Stevenson

Offline awemawson

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Re: Fork truck help needed
« Reply #1 on: February 08, 2017, 04:54:38 PM »
John, can you put any other load on the charger leads, such as a DC motor or big rheostat to encourage it to switch on so you can positively identify their polarity ?

Years back I made up a 'dummy load' to test fork lift batteries from a roll of galvanised fencing wire wrapped on an asbestos flue and I reckon that would work as a load for your charger.
Andrew Mawson
East Sussex

Offline John Stevenson

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Re: Fork truck help needed
« Reply #2 on: February 08, 2017, 05:00:30 PM »
I've got next door cat locked in the workshop, will that do ?

I've got a big variac 250v in ??
John Stevenson

Offline awemawson

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Re: Fork truck help needed
« Reply #3 on: February 08, 2017, 05:05:01 PM »
It DC resistance is probably too low - measure it on an ordinary multimeter but I reckon it'll only be a few ohms
Andrew Mawson
East Sussex

Offline sparky961

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Re: Fork truck help needed
« Reply #4 on: February 08, 2017, 07:02:33 PM »
Heater elements are often a good choice for DC loads.  Watch out though, they'll heat up with use...  ;)

You can series or parallel a bunch if you can't find just one with a suitable resistance or rating.

Offline John Rudd

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Re: Fork truck help needed
« Reply #5 on: February 09, 2017, 02:28:25 AM »
Guys,
I think you may find that the charger is looking for a dc supply coming back from the battery....the charger sees a voltage fed into a sensing network that then permits the 'charging circuit' to energise and start pumping juice.....then when the voltage level reaches the fully charged state it switches off....
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Offline PK

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Re: Fork truck help needed
« Reply #6 on: February 09, 2017, 02:53:06 AM »
Guys,
I think you may find that the charger is looking for a dc supply coming back from the battery....the charger sees a voltage fed into a sensing network that then permits the 'charging circuit' to energise and start pumping juice.....then when the voltage level reaches the fully charged state it switches off....
Seconded. I've 'fixed' a few 'it won't charge a dead flat battery' faults over the years by trickle charging to some threshold voltage.
Clever chargers measure the start voltage to ensure they don't overcharge a pack with shorted cell. If the initial pack voltage isn't high enough then it locks out.

Offline John Rudd

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Re: Fork truck help needed
« Reply #7 on: February 09, 2017, 03:36:09 AM »
If the charger operates the way I suggested, connecting the leads the wrong way round should prevent the charger from doing anything stupid like reverse charging the batteries.....

So, get a dvm, on volts.....connect charger to mains, connect charger to battery and with dvm across try charging but watch the meter....the reading  should give you an idea that its working....you could put a fuse in series with one of the charger leads....( 3 amp fuse should be ok...) to give you a bit of insurance against reverse polarity....

Latly, have the boys in red on standby just in case.... :zap:
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Offline Will_D

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Re: Fork truck help needed
« Reply #8 on: February 09, 2017, 06:09:23 PM »
I've had a similar problem with a totally flat (like 6V) car battery (12V);

My modern, safe, sealed battery charger won't charge the battery as the charger doesn't see the battery. 6V is way too low.

Trick is to connect another 12 battery in parallel for some time and then apply charger to both, after a while you remove the good battery.

So blag 4 12 car batterys, connect in series then connect to the fork batter in parallel.

Also the 4 in series will test the charger!

HTH

Will
Engineer and Chemist to the NHC.ie
http://www.nationalhomebrewclub.ie/forum/

Offline John Stevenson

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Re: Fork truck help needed
« Reply #9 on: February 09, 2017, 06:28:54 PM »
The pucker factor is now in the red after reading all the replies.
I think I'll venture into the hay loft and remove a few panels, if that fails I'll re read the posts  :zap:

My first fork truck was bought with two batteries linked out where the guy previous had connected it wrong and blown the tops out complete, and these are big batteries.
A second hand set fetches 500 on Ebay so not worth the risk.
John Stevenson

Offline Fred Bloggs

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Re: Fork truck help needed
« Reply #10 on: February 10, 2017, 04:25:24 AM »
John you have PM

Best Regards

Fred