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[no1chunk]

Hello guys prob been covered before but i get all loat and confused which the different rate etc. I have some lead acid batteries for my dutch courage build and now my graupner nordic build. What rate would you suggest i charge the batteries i have a ripmax sigma eq eco or how do you calculate thanks guys

[Taranis]

30% of current capacity is good
10ah charge at 3amp


Less current is fine but will take longer of course

[no1chunk]

Ok cheers want 2 x 6v 7ah for my nordic build and i got a 12v 10ah for my dutch courage build so 30% of the ah is gd

[nemesis]

treat them like babies, less is more. If in doubt of any lead acid stick them on half an amp. Yes they will take longer but you will be safe at that limit. When I used L/Acid I put them on charge at that rate and disconnected them two days later when the reading was trickling on in milliamps. nemesis

[no1chunk]

Cheers i did a low amp on my sons ride on car battery and it actually stopped charging as the charger reached a limit so il av to give the manual a good read

[malcolmfrary]

Hidden in the instructions - http://www.ripmax.com/Instructions/o-ip3052.pdf - is the snipper that for lead acid, "optimal charge current is 1/10 of the capacity."
Good advice.
Discharging lead acid batteries shuffles the chemical coating of the plates, charging shuffles it back, but there is no guarrantee that it will all shuffle back exactly the same, so batteries age.  Fast charging and discharging ages them faster as the plates grow bald bits.

[Colin Bishop]

Also I think a lot of people don't appreciate that the usable capacity of an SLA battery is normally only around 50% of the quoted figure as they should not be discharged below 50% wherea the usable capacity of a NiMH pack is much closer to its nominal figure.

SLAs can cost a fair bit less overall for a similar actual capacity if the the weight isn't an issue (about fourfold I think.) and you are not looking for performance. As always it is horses for courses and a trade off between price, capacity, weight etc.

Colin

[roycv]

Hi all, trickle charging at 1/10th. capacity can go on for as long as you want, usually add 40% to this for a full charge.  Best to use a dedicated SLA charger, they are not dear preferably an intelligent one which will give a green light when charging complete.
The dedicated charger does not work on constant current, it taper charges i.e. the applied voltage reduces as the charge on the battery increases its' voltage and progresses until the voltage is about equal to the battery.  The current is initially limited but is governed by the increasing voltage of the battery on charge.

There is a major difference in how the capacity is measured between SLA and Nimh batteries.  SLA are rated at the 20 hour rate and Nimh's at the 5 hour rate.
This means that an SLA of 5AH (or 5000MAhs) capacity will deliver 5/20 amps for 20 hours this is 1/4 amps (250 mamps) for 20 hours.  If you take more current the capacity reduces with heat losses etc.
A NiMh battery of same nominal capacity will give the full capacity over a 5 hour period at 1 amp.The SLA can deliver 1 amp easily but for far less time.

I had a 12 volt SLA battery 3.5 Ah driving a boat and the current was 2.5 amps, (30 watts) nothing got that hot but run time was just about 40 minutes.  If you convert to watt minutes you will see that the actual capacity available at the higher current was only half the nominal capacity of 3.5 Ahs.

If a NiMh battery was used of 3.5 Ah capacity I would have expected at least an hour running if not more, but I never did the comparison.
Clearly the NiMh battery is dearer but that is what you are paying for.  By the way the cylindrical SLA batteries are rated at the 5 hour rate so cost more as well.
Hope this helps some, sorry if I am suggesting ways to suck eggs to the others.
regards Roy

[Colin Bishop]

Anything that helps explain technicalities is good Roy. It is a closed book to many people.


Colin

[nemesis]

Lead acid require constant voltage whereas ni-cads, hydrides and lipos etc require constant current. nemesis

[no1chunk]

Thanks for replies iv got battery already so stick with that for ballast and cost. Currently building a graupner nordic manual recomends 2 x 6v 7ah but i have 1 6v 14ah so was just gonna use that. What rate would i charge that using my ripmax sigma do you guys suggest. Im new to all this i ised to use stick packs years ago with a simple turn dial type charger.
Thanks

[roycv]

Hi 14 Amp hour divide 14 by 10 = 1.4 amps and this is the trickle charge rate.  Do you have a meter?  If you do then when the battery gets to 7.2 volts it is fully charged.  The 7.2 volts is based on a fully charged cell ( a battery is a group of cells) is 2.4 volts there are 3 cells in a 6 volt battery so times 3 gives you 7.2 volts.
regards

Roy

[no1chunk]

Thanks for tht info appreciate it

[Taranis]

To be honest I just make sure my batteries are recharged straight away after full discharge. I'm not too particular about calculations I just set my intelligent charger at 2 amps and let it do the business.




I have cobbled together some surplus solar panels on my shed and I have old batteries from my van. These power multiple chargers when I need them without charge (pun)











This is the best charger I've had yet and I paid under £45 ebay. Gets good reviews on the tube and its very small for a dual charger.

[no1chunk]

Looking good that setup i have 2 solar panels in the shed from our old touring caravan its only a 20watt trickle but could do the trick in summer i supose

[malcolmfrary]

Probably not that good for overnight charging.

[Netleyned]

I have that trouble with my Solar Powered Torch
Ned

[Taranis]

Mine switch to lunar mode 

[Netleyned]

Mine tends to tick in that mode
Ned