Proper 12 Volt charging?

I'm looking at buying 2 Fullriver HGL 120 which have a charge rate 14.5-14.9 boost and 13.6-13.8v float.
Q is it best to by separate dc-dc charger and solar reg that charge within these or is it best to buy say Redarc 1240 mppt that is only 14.5v boost-13.3v float, which is outside of specs, float only to look after battery's properly.
Matt
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Reply By: Nomadic Navara - Thursday, Mar 26, 2015 at 12:23

Thursday, Mar 26, 2015 at 12:23
There is no problem with several chargers connected to a battery in parallel unless the potential combined output of the chargers is too large.

What is the DC-DC charger and the solar controller you are using? What is the maximum current you have see the solar system producing?
PeterD
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Follow Up By: Peter_n_Margaret - Thursday, Mar 26, 2015 at 15:53

Thursday, Mar 26, 2015 at 15:53
Peter, my view is that the potential output of chargers is of no consequence, PROVIDED the voltage offered is appropriate.

The battery will accept what it can, depending on its internal resistance and the voltage offered.

Vis... Many alternators will offer over 100A to a single battery. This presents no risk to the battery because the voltage is not excessive.

I have used a 120Ah Fullriver HGL as the crank battery in the OKA for 5 years. It is the longest lasting crank battery I have had in the vehicle by a factor of 2X. It is NOT under the bonnet.
The alternator is 80A and the voltage is 14.3V.

It is advisable for charge sources to have battery temperature compensation, if the are outputting close to the maximum volts recommended by the battery maker.

I agree that there is no problem with connecting multiple charge sources at the same time.

Cheers,
Peter
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Follow Up By: Member - Phil G (SA) - Saturday, Mar 28, 2015 at 19:51

Saturday, Mar 28, 2015 at 19:51
I used to think the same as Peter_n_Margaret but after trashing an AGM in under 2 years, now agree with PeterD.
FullRiver quote a max charge rate of 24Amps in their specs for the 120Ah batteries. To charge at an unrestricted rate from an alternator will progressively reduce the batteries capacity until it becomes useless.

Using one as a starting battery in a cool environment is a cushy environment for a battery - would rarely exceed the 24 amps as it's stays fully charged and cranking uses next to nothing.
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Reply By: HKB Electronics - Thursday, Mar 26, 2015 at 12:38

Thursday, Mar 26, 2015 at 12:38
The battery you have specified has a maximum charge rate of 24A, so depending on how you are intending to arrange the batteries I would be wary of the 40A charger.

Most chargers in AGM mode will only output a maximum of 14.5V@25C.

I wouldn't worry about the float voltage being low, better low than high and generally they only become critical if your going to be floating the batteries 24/7. As most seldom drive long enough to fully charge the batteries (actual fully charge not when the charger shows fully charged) generally not a problem.

If you are going to float 24/7 then float voltages can become critical for SLA batteries and the manufactures specs for upper float voltage limits should be adhered to.

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Reply By: Allan B (Member, SunCoast) - Thursday, Mar 26, 2015 at 15:21

Thursday, Mar 26, 2015 at 15:21
Hi Mathew,

The Fullriver float voltage you quote of 13.6 - 13.8v is for a battery temperature of 20c. At most times in Australia its temperature is likely to be higher than that, possibly 40c or more. If located in the engine bay it could be considerably higher --- I have measured 70c at the battery location in my Troopy before I shielded and insulated the battery area.

I would recommend that AGM batteries not be located in the engine bay, but even if in the cabin or in a trailer, the battery temperature could rise to or above 40c during charging.

The Fullriver specs for the HGL series limit the float voltage to 13.29 volts for a temperature of 40c so the Redarc DC-DC chargers should be acceptable. A small amount of undercharge is preferable to any overcharge.

Cheers
Allan

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Reply By: Member - Cuppa - Thursday, Mar 26, 2015 at 23:05

Thursday, Mar 26, 2015 at 23:05
Worth considering DC series rather than HGL series Fullrivers. Thy generally last longer in mobile context where vibration is a factor).
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Follow Up By: Peter_n_Margaret - Thursday, Mar 26, 2015 at 23:20

Thursday, Mar 26, 2015 at 23:20
I agree that DC is better for cycling applications.
The HGL is predominantly a standby battery, but it has done me proud in high vibration which was the cause of my previous crank battery failures.

Cheers,
Peter
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