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Author Topic: using a forklift charger to recharge batteries when the generator is running?  (Read 3629 times)
nick disjunkt
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« on: May 05, 2010, 02:08:15 PM »

Hi all,

My first post here although Iíve been reading the forum on and off for a few years.

First a little about my project.  I have an 18 ton Mercedes truck which was an armoured cash in transit vehicle for brinks in a previous life; I am gradually converting it from useless lump of metal to round-the-world motorhome and have recently started work on the electrical side of things.

I recently brought some 550ah roll surette 5000 series batteries (second hand but well maintained) to use as the house batteries in the truck and am now preparing the charging side of things.

There will be three charging systems for the rolls batteries on the truck, first will be through a regulator/split charger from the starter battery, second will be from a couple of solar panels on the roof, and third will be from a mains powered charger which Iíll run from the generator mounted on the chassis of the truck or from the mains where itís available.

Itís the third one Iíve got some questions about.

I have a big forklift charger which is the wrong voltage and too powerfull but a local forklift place has agreed to swap my charger for a 24v 50a one which seems like a well suited output current.

Would a forklift charger be suitable in this application?

Are they able to fully charge batteries in the same way that the intelligent 3 stage chargers from the likes of victron, sterling trace, etc area? I know that forklift chargers do not typically adhere to the three stage charging system that solar/marine chargers tend to use but the decent ones certainly seem to apply some kind of intelligent charging system. It seems that after the bulk stage they taper down to the float voltage at a rate based on the length of time it took the charger to replenish the battery. Will I get a noticeable improvement if I use a marine/solar/expensive unit?

Additionally would a forklift charger be happy on a small generator?

The generator is a Pramac p4500 with a continuous output of 3.1 Kw.  Even a hideously inefficient 50a at 24v charger shouldnít pull more than about 2 Kw so theoretically the charger should run fine but what about the quality of the power? The generator is modern and newish but it has a single cylinder (yanmar) engine in and so it will never be producing a perfect sinewave; will the charger throw a tantrum? I havenít actually picked up the charger yet but almost every forklift charger Iíve used has has a big old transformer in it so is unlikely to use a fancy hf switch mode power supply.

My final question is probably unanswerable without knowing the make and model of charger but I was wondering whether a forklift charger would be happy with the mains power only being available sporadically? I am aware that some chargers have a kind of stored memory which remembers how long it has been since it put an equalisation charge into the batteries  which may be confused if the mains power is only available once a week or less. 

Sorry for all the questions but I hope some of you can answer them and maybe Iíll be able to repay the favour by contributing  in other areas where Iím less ignorant.

Thanks,

Nick
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biff
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« Reply #1 on: May 05, 2010, 09:00:38 PM »

hi nick,
    im looking forward to you getting plenty of replies,i will be looking over your shoulder as i have similar questions to ask.,however i believe that forklift chargers like plenty of powerfull juice and i got a feeling that your geni would be murdered trying to bulk your batteries. might be ok, but there are guys on here who can tell us. whistlie       
                                 biff
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spluger
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« Reply #2 on: May 05, 2010, 09:30:25 PM »

from my experience in the electric go-kart industry
from the way you described the charge process that sounds like 3 stage
IE constat current until x voltage reached then constant voltage for  stage 1 time + 50% then switch to float charge (lower voltage thane stage 2)

if your charger has big transformers then it wont care about the type of sine wave it will smooth it itself the only problem i see is the starting current might make the genny frow a wobbly or blow a fuse. but try it anyway

if the charger is monitoring the voltage then other sources can be used at the same time as it should taper the voltage to suite as long as no sweep delay is built in.

as for the sporadic use of mains
i think you answered that yourself if its a simple charger (2-3 stage no bells and whistles) then no probs

JUST make sure you don't over discharge your batts as this WILL KILL them!!!

David
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Justme
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« Reply #3 on: May 05, 2010, 09:42:57 PM »

You could use the forklift charger for the bulk phase & then switch over to a smart charger for the rest.
A simple timer on the forklift socket would do it.
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knighty
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« Reply #4 on: May 05, 2010, 10:53:01 PM »

according to the sticker on my forklift charger, it max input current is 27amps at 230v.... it puts out 60amps at 48v

so is a bit more than twice your 24v 50amp one....  so your 3.1kw should be fine ?


p.s. my forklift charger has an amps (out) display on it, and it always starts down low and builds up slow... so if yours does the same you should be ok for start up current too ?
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spluger
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« Reply #5 on: May 06, 2010, 06:57:40 PM »

Yes but watch for the inrush current when you turn it on for the 1st time this can be several hundred for a fraction of a second. might trip etc,

unless the charger has soft start or current limiters


David
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weather compensated boiler
nick disjunkt
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« Reply #6 on: May 07, 2010, 09:50:01 AM »

Hi all,

Thanks for the responses. Seems like I've got nothing major to worry about.

I'm picking up the charger on saturday so I'll let you know how I get on.

Untill I get a decent battery monitor (peukert based?) I won't know exactly how well the batteries are doing but I should be able to tell whether they're happy or not.

Seems like the charger I'm getting is designed to run on a range of voltage and mains frequencies so should be fine on my genny.

thanks,

nick
« Last Edit: May 07, 2010, 09:56:57 AM by nick disjunkt » Logged

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