Jon Ison
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| posted on 23/2/05 at 09:21 PM |
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Charging 2x batterys.
I'm gonna be fitting a second battery to the car, (both bike batterys) will be running 24v for reverse, now then, is there an easy to understand
way of charging the second battery or would,nt you bother, the reason i say would,nt you bother is i will only ever use reverse if asked to during
scrutineering, that said i guess the battery will last longer if its charged on the car rather than maybe once a month in the garage.
did i make sense ? prob not.
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clbarclay
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| posted on 23/2/05 at 09:25 PM |
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My experiance says that 24v systems need 24v charging systems (mains and alternator)
Why don't you wire the batteries in parallel (which gives 12v and twice capacity). then you can use a 12v motor for revesing, any engine starter
motor will do.
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Jon Ison
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| posted on 23/2/05 at 09:32 PM |
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the reverse is allready fitted n working, dont want too start over again if i can avoid it, for the very limited added weight of a second bike battery
it goes from slug pace too snail pace, its not that i want a reverse i have to have one, part of the test is it as to go over a 50mm square block of
wood, at slug pace it struggles, zero momentum, at snail pace it flys over, dont want to pay £xxx to enter a race just to be excluded after the event
cos i cant get me leg over a block of wood, its just maintaing the second battery i was querying.
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Deckman001
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| posted on 23/2/05 at 09:37 PM |
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your best bet is to keep it separate , or you'l need a 24v charger to feed em both but then take a supply off for the normal 12v system, if you
need a charging circuit on the car then best to keep it 12v and top the other battery up at the weekend as it were
Jason
I'll ask the charger company we use for you tomorrow to be sure 
[Edited on 23/2/05 by Deckman001]
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cosworth
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| posted on 23/2/05 at 10:03 PM |
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You can get a split charger unit which is a bit like a relay unit. Otherwise change the batteries over once a week so that they both get charged up on
the car.
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Jon Ison
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| posted on 23/2/05 at 10:06 PM |
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Mr Cosworth, so simple, ta........
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Peteff
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| posted on 23/2/05 at 10:25 PM |
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A caravan charging relay should do it Jon.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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stephen_gusterson
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| posted on 23/2/05 at 10:28 PM |
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i was gonna say that pete, but seems like youve blown your cover.
caravanner hey  
atb
steve
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Peteff
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| posted on 23/2/05 at 10:41 PM |
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Little old shed dragger me.
Yup. You could get the start'n'charge thing like the Lidl offer and take it out when you've run over the block Jon.
http://www.lidl.co.uk/gb/index.nsf/pages/c.o.oow.20050221.index
[Edited on 23/2/05 by Peteff]
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Jon Ison
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| posted on 24/2/05 at 07:12 AM |
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talking of caravans saw one upside down on M5 yesterday near Micheal Wood services, look out for chassis on ebay....
Cant realy do it that way Pete, they dont scrutineer for "elgibility" till after a race and the car cant be "touched" by
anyone or anything once it comes of the track into "parc thingy" thats when they check such things as weight, ride height and in our case
reverse.
[Edited on 24/2/05 by Jon Ison]
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Mix
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| posted on 24/2/05 at 09:01 AM |
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You say that you will normally be using one battery so I assume you're charging that during use @ 12V. When using reverse you add another
battery in series giving 24V. Therefore when the second battery is not in use I assume it is electrically disconnected. If it is disconnected why
can't you charge it from the vehicles 12V system?
Mick
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Mix
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| posted on 24/2/05 at 09:36 AM |
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Another option is to wire the batteries in parallel for normal use, (12V) and switch to series, (24V) for revesing.
Mick
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clbarclay
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| posted on 24/2/05 at 10:12 AM |
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Not sure what the aim of this electric reverse is but what have you use as motor, 12v motors are used to start large desiel engines (at least up to
14litre im 100% sure about) just make sure you have the gearing right.
alternatively wire the first battery in normally and the -ve terminal of the second to the +ve terminal of the first. this means that atlest one
battery is being charge by the car, the other will needregulare checking.
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indykid
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| posted on 24/2/05 at 10:44 AM |
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i was thinking that Mix.
but what would it do to the rest of the system when you put 24V on it.
maybe you should be looking at a 3 battery system .
i know it sounds daft, but it seems the only logical way to maintain a 12v system, running alongside a 24v system.
not very plausible, but an idea
tom
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Mix
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| posted on 24/2/05 at 10:56 AM |
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I was thinking more along the lines of isolating all but the reversing motor with the selector switch and relay.
Mick
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Mix
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| posted on 24/2/05 at 12:05 PM |
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I think this would work for changing the batteries from series to parallel.
 
Rescued attachment Batts.gif
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DarrenW
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| posted on 24/2/05 at 12:12 PM |
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Mr Ison,
I assume your electric reverse is currently 12V if you run it from a single battery and you are looking for a few more amps to get over the block.
Running 24V thro it surely would cause damage. Is the existing 12V battery just not man enough to power the reverse motor - ie it draws too much power
and the battery is being drained?
The simple way for me would be to use split charge caravan style circuit to charge both batteries all the time. Wire up both batteries (to give 12V)
so they power the full electric system all of the time. Fullpower will only be consumed by the device that needs it at that point in time - in your
case the reverse motor.
Alternativley why not try a bigger more powerful battery first to prove the theory?
Are you sure the reverse motor has a large enough feed cable or earth cable. Im wondering if volt drop is your problem. I had a problem starting a car
once even after it was fully rebuilt. Starter was very slow. Changed leads to Fork truck sized ones and it span over fast after that. If it is OK
thenperhaps the motor is not big enough or geared wrong (you didnt say what spec motor it is and sorry but im no expert in bec reverses).
HTH,
Darren.
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clbarclay
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| posted on 24/2/05 at 12:22 PM |
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Mix
kinda like the first idea, but make sure that the second battery is first disconected before reconnecting the other way round.
I you have 2 batterys wires in series and parallel at the same time its is like connectin a single wire from between bothe terminals of a battery, but
you have 2 f@#&%d batterys in stead on just the 1.
Not a good idea. so don't try the second idea
You also need some way of isolating the rest of the system from 24v. 12v circuits don't take kindly to double the recomended voltage.
[Edited on 24/2/05 by clbarclay]
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clbarclay
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| posted on 24/2/05 at 12:31 PM |
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Jon, is it possible to change the motor to a 12v unit. i've seen a beetle driven on its standard starter motor (12v), it was not very quick but
it seement to drive it ok.
Got any pics of the revesing system you are using.
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Mix
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| posted on 24/2/05 at 12:44 PM |
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Sorry
My diagram is not all it could be 
The two diagrams are of the same circuit, the dotted line is a ganged relay which would change the batteries from series to parallel connection. I
think that this circuit could be wired to isolate the other systems as it is, (could be wrong here though, electrickery isn't my strong
point)
Mick
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indykid
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| posted on 24/2/05 at 04:26 PM |
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that would be ok to run just the motor, but it means cutting power to all other systems to achieve it.
i don't know the race regs, but surely they would object to that.
iiwy i'd be looking to run a bigger single battery, or gear the motor lower.
tom
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