battery charging

Submitted: Thursday, Jun 16, 2005 at 08:47
ThreadID: 23910 Views:1973 Replies:8 FollowUps:4
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Usually i disconnect the positive lead from the vehicle battery before connecting the 7 amp battery charger to the vehicle.

Is this necessary or could I simply connect the charger without disconnecting any battery leads?
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Reply By: Russel & Mary - Thursday, Jun 16, 2005 at 09:11

Thursday, Jun 16, 2005 at 09:11
If you connect the charger and then turn it on, there shouldn't be any power spikes that will potentially cause damage. Rus.
AnswerID: 115999

Reply By: Bob Y. - Qld - Thursday, Jun 16, 2005 at 09:25

Thursday, Jun 16, 2005 at 09:25
It's preferable to disconnect neg terminal, then there is no risk of anything shorting between pos terminal, and any part of bodywork, engine etc. Shouldn't need to disconnect any terminal, just to charge battery.

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Can't remember most of it.

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AnswerID: 116001

Reply By: Member - John C (QLD) - Thursday, Jun 16, 2005 at 09:46

Thursday, Jun 16, 2005 at 09:46
Usually shouldn't need to, but on trying to charge the golf MK1 had to disconnect the negative and positive last night to see the charger charging.
In the past I disconnect both out of habit, and take the fill plugs out too for a heavy charge so the hydrogen doesn't build up too much. Usually check water levels before charging any way. Have seen a few bubbles on charging a low battery.
AnswerID: 116002

Follow Up By: Member - Collyn R (WA) - Thursday, Jun 16, 2005 at 10:27

Thursday, Jun 16, 2005 at 10:27
Re gassing

A conventional lead acid battery begins to gas at approx 70% of full charge. As that's more or less the maximum that they can be charged to by a car alternato, heavy gassing is rare.

Do note however that a deep-cycle battery is best charged as close as feasible to 100%. This is only possible via a smart alternator regulator, a three-stage battery charger, or via solar. Then gassing is a normal effect and is not helped or hindered by removing the battery fillers (which are ventilated anyway). As such a battery approaches 100% charge gassing is quite strong and the battery may almost seem to be 'boiling'. My big home system (24 by 680 Ah two-volt cells) can be heard charging from 20 metres away - and are now close to 7 years old.

A quick and dirty guide to battery charging is that a battery that is routinely being well charged should use about one centimetre of water every 8-10 weeks.

Re disconnecting leads before charging - not normally necessary - but if you have a three-stage charger with an equalising function make sure nothing electronic is switched on during that cycle (which may go up to 16-volts).
Collyn Rivers
FollowupID: 371570

Follow Up By: Tony J - Thursday, Jun 16, 2005 at 17:30

Thursday, Jun 16, 2005 at 17:30
Hi Collyn R,

What is a "smart alternator regulator"? Is this something that can be fitted to my 80 series or is there one there already? How can I tell?

Tony J
FollowupID: 371614

Reply By: Longreach - Thursday, Jun 16, 2005 at 15:07

Thursday, Jun 16, 2005 at 15:07
This is an interesting site for battery info.

Battery Info
AnswerID: 116026

Reply By: Member - Collyn R (WA) - Thursday, Jun 16, 2005 at 18:53

Thursday, Jun 16, 2005 at 18:53
A smart regulator acts much as a three-stage battery charger. It is fitted in place of the existing regulator and charges the vehicle battery/s as heavily as is safe and very close to 100%. They are commonly used on boats but are less know in Oz with RVs. I have had one on my OKA for the past eight years - works superbly and will charge the house batteries at up to 100 amps!

Give Outback Marine (Qld) a ring if interested.

Another solution is a very ingenious NZ device just recently developed that boosts the charge voltage and applies it as a variable width pulse at up to 15 volts.

It seems perfect for 4WD and camper trailer use not least because it does not interfere at all with the vehicle's electrics.

I shall be having one for evaluation shortly and will advise what I find on my own website. Will also post a brief report on this site.
Collyn Rivers
AnswerID: 116042

Follow Up By: ev700 - Friday, Jun 17, 2005 at 00:27

Friday, Jun 17, 2005 at 00:27
Thanks, enjoyed your A4 bound book too. Will keep an eye on the site.
FollowupID: 371661

Follow Up By: Austravel - Thursday, Jun 30, 2005 at 17:25

Thursday, Jun 30, 2005 at 17:25
Hi Collyn,

You stated in a previous message that a vehicle alternator will only charge to about 70%. I thought this would be based on time. I under stand that the regulator reduces charging but my vehicle charges at a constant (pretty much) 14.0 volts so even with current regulation if I drive for some hours (maybe a day) then my battery should fully charge. I've drained my 3 onboard batteries (2 in car and one in camper) and then driven about 6 hours home, put on the 3 stage 15amp charger and within an hour or less it switches to float.

FollowupID: 373454

Reply By: Member - Jeff M (WA) - Thursday, Jun 16, 2005 at 22:28

Thursday, Jun 16, 2005 at 22:28
Bugger it and all the techno fobes out there, I've got all the electronic ECU and crap, I also have a stack of accessories, I just whack the bugger (8 amp charger) on and let er' rip. Never had a problem.
AnswerID: 116079

Reply By: ev700 - Friday, Jun 17, 2005 at 00:30

Friday, Jun 17, 2005 at 00:30
Thanks everyone for your replies. ;-)

AnswerID: 116095

Reply By: Member - Collyn R (WA) - Friday, Jul 01, 2005 at 09:52

Friday, Jul 01, 2005 at 09:52
Apologies for delay in responding - had total computer crash that required equally total computer rebuild.

The 70% limitation is a generalisation but battery makers agree that the most common charging limit with standard alternators and regulators is 70% give or take a few per cent.

The limitation is inherent in constant voltage charging because as the battery voltage rises towards trhe charging voltage, the current tapers off. By 70% the charge rate has dropped to a trickle. Charging will continue but at a progressively decreasing rate. This limitation is deliberate to prevent overcharging in vehicles such as country sales reps cars that are driven vast distances each day.

(Given several days at a constant 14.4 volts however a starter battery will approach 90% or so charge - but this rarely if ever happens in real life, not least because most voltage regs are now set up at 14.2 volts).

In practice conventional lead acid batteries only fully charge (even from three-stage chargers) if they are allowed to run up to about 15.0 volts and then drop back to about 14.4 volts for a few hours to absorb the charge - and onmly then drop to floating.

With your charger, is it a true three-stage charger, or is it one of those constant voltage units that switches directly to float? If it is, then it is sensing the charge across the plates of the deep cycle batteries. This does not reflect the true state of charge.

Do also bear in that a corollary of the above is that instantaneous voltage readings of deep cycle batteries are almost meaningless unless that battery has rested for at least two full days off-load (it is this affect that causes some battery chargers to switch to float prematurely). Any deep cycle battery taken off-charge will show a much higher voltage than reality for many hours - until the internal chemical interactions have ceased and the charge is homogenous.
Collyn Rivers
AnswerID: 118374

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