Charging Aux battery

Submitted: Sunday, Aug 03, 2003 at 17:59
ThreadID: 6344 Views:1709 Replies:6 FollowUps:2
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Hi All,

I am soon to be installing a dual battery system in my troopy. I understand the difference between solenoids, isolators, redarc, rotronics etc, but I would like to know is it better to charge each battery independently, or to connect the auxiliary in parallel with the main battery when charging the auxiliary.

Also, as the auxiliary battery will be used lots during school holidays but rarely during school terms, I was told that an exide extreme battery would be better than a deep cycle battery. Is this good advice?

Thanks heaps :-)
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Reply By: Member - DOZER- Sunday, Aug 03, 2003 at 18:02

Sunday, Aug 03, 2003 at 18:02
Independant is better for the batteries.(rotatronics)
Ever considered another alternator?
Andrewwheredayathinkwer mike?
AnswerID: 26681

Reply By: Allyn (Pilbara) - Sunday, Aug 03, 2003 at 18:27

Sunday, Aug 03, 2003 at 18:27
deep cycle not needed by my reckoning. No doubts others will disagreeso many places, so little time !!!
AnswerID: 26688

Reply By: bigboy - Sunday, Aug 03, 2003 at 19:07

Sunday, Aug 03, 2003 at 19:07
The exide extreme battery is a good in 4x4 use . it is not a deep cycle but it is a
extra cycle battery . so this means it can handle being flatend .
and it is vibration resistance .
i run a extreme in my 4x4 it has a 2 year warranty and 4 years later it still
cranks the diesel over . with 620 cca and 80 ah
AnswerID: 26689

Reply By: Voxson (Adelaide) - Sunday, Aug 03, 2003 at 19:34

Sunday, Aug 03, 2003 at 19:34
I use a gelcel in parallel with the main batt and the 80amp alt keeps em both charged perfectly.............
It has done 30,000kms with no probs at all......._____________________________________________

AnswerID: 26693

Reply By: Member - Bruce and Anne - Sunday, Aug 03, 2003 at 19:38

Sunday, Aug 03, 2003 at 19:38
We installed a 23 plate, 930 cranking amps battery, took it out of our yacht, hooked it through to the main battery with a 30 amp fuse each end and a $20 cut off switch. We ran a 80 litre Waeco just done 4 weeks to darwin and back, no trouble, I started the motor for about 15 minutes in the afternoon if we did not move for two days. I've been playing with 12 volt power on boats for 25 years and the best way to charge batteries is to have an alternator (12 volts ) that can constantly be able to put out as close to the amperage that it is made for. We do this on the yacht by by passing the regulator,(do have to monitor this manually).
The Chrissy's unit is the way to go in this environment. I could not pay some auto electrician $160 just for a soleniod and more to hook it up, been around too long.MU-ving on
AnswerID: 26695

Follow Up By: joc45 - Sunday, Aug 03, 2003 at 22:42

Sunday, Aug 03, 2003 at 22:42
Interesting - Why do you bypass the regulator?
FollowupID: 18259

Reply By: Member - Bruce and Anne - Monday, Aug 04, 2003 at 07:54

Monday, Aug 04, 2003 at 07:54
The alternator will charge the battery at nearly full amps untill the battery reaches say 13.8 volts but this is only surface charge, the alternator will than drop back to around 8 to 10 amps. All these smart charges you see work on the principal of that, so they sence when the reg tells the alternator the battery is charged and basicly turn it off untill it reaches say 14.4 volts and there for the battery gets charged a lot quicker, hope this answers your question, sorry I have to run leaving for Brisbane in a couple of minutes.
Regards BruceMU-ving on
AnswerID: 26728

Follow Up By: joc45 - Monday, Aug 04, 2003 at 19:21

Monday, Aug 04, 2003 at 19:21
I see where you're coming from, but trying to get that battery charged in 15 mins every few days on your boat is asking a bit much of the battery. The only way you will push in the amps, as you say, is to raise the voltage (hence the reason for bypassing the regulator), but in so doing, you could raise the volts to unacceptable levels, both for the battery, and for any electricals on the boat/vehicle.
In addition, lead acid batteries do not like fast recharges in the way that sealed Ni-Cd or Ni-MH batteries do. Sure, you might get the battery up fast, but at what cost? (as a lad, I used to charge my 6v motor bike battery up by putting it across a 12v battery - it charged in a few minutes, but didn't last long)
True, some solar regulators initially take the battery up to 15v following a deep discharge, but that is to initiate gassing to prevent stratification of the electrolyte, and then it is only for a short period and a moderate charge current before reverting to a max voltage of about 14.2.
The other issue is that even if you do monitor the charge (I'm not sure what your criterea are), how do you take into account load changes (eg fridge cutting in/out). This is what a regulator is for. An unregulated alternator can put out 50-100v (true!!) - is it worth the risk?
The 13.8v you quote sounds a bit on the low side for flooded cells, but is probably more than enough if you are running gel cells. While charge current will drop off as the battery charges, lead resistance from the alternator to the battery could be a factor in limiting your charge current. Some alternators have a separate sense lead from the battery back to the alternator regulator (my Patrol does), which takes into account the voltage drop between the two and corrects it; this will improve the charge current without running the battery over-volts.
rgds, Gerry
FollowupID: 18311

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