Battery Charging Input Voltage Question

[wakeup]

Hi,

I have just replaced my starter and domestic batteries with 1x115ah starter and 2x115ah domestics.

The batteries are lead (openable) type not sealed nor gel and are manufactured by Numax (labelled deep cycle)

Both banks are connected to the same battery charger. Reading the configuration guide there are dip switch settings for the type of battery and those settings in turn set the input voltage during the boost and absorption phase.

The voltage input options are 15.1v (for lead tin delphi delco whatever they are?), 14.3v (lead sealed), 14.1v (Gel Lead) and 13.7v (open lead). I am not at all sure which ones I have. They are Numax (Non sealed)

Now I know that the batteries are neither sealed or gel so that eliminates 14.3v and 14.1v . The batteries have been on charge for 24 hours with boost on the lowest setting and the charger says each battery is only 92% full. Could it be that I should have the charger set to 15.1v not 13.7v? I would have expected them to be at 100%. Am I undercharging them with too low a voltage?

The above figures are for the boost phase only the absorption phase lowers to 14.4v for the lead tin delphi and 13v for the open lead. 13v seems low to me however I don't want to overdrive or boil this new set of batteries.

Any comments gratefully received.

 

[Richard10002]

From the alternator, which charges at 13.6v, my open batteries take forever to charge fully, if ever. I understand that Smart chargers charge at about 14.4v for the most part of the charging cycle, then reduce to around 13.6v for the last bit, then they trickle charge to keep them topped up

I also understand that modern alternators charge at around 14.4v, and a smart charger isnt necessary.

I would be tempted to charge them at 14.4v and be ready to top them up with water fairly regularly.... or watch the moniter, and reduce the charge manually to 13.6v for the last 5 or 10%.

I'm no expert, and may be completely wrong. It's just what I've gleaned over the past 3 years.

 

[msimms]

14.3V seems a little low and 15.1V a little high for absorption, the same goes for 13V and 14.4V for float.

My charger, Sterling, uses 14.4V for sealed and 14.8V for open. This is the same for the boost and absorption phases. Absorption maintains voltage and reduces current over time. Whenever I've monitored the status LEDs it never seems to be on boost.

For both types it drops to 13.6V float level. I have Numax too but the CXV sealed type.

I think I'd be tempted to run with the lead sealed setting to start with and then maybe the higher setting if I didn't think I was getting a full charge - but keeping a close eye on the water level.

Might be worth an email to Numax asking their advice.

Cheers

Mark

 

[Piers]

I believe msimms is right. Lead acid (open tops) requires 14.8v for charging.

 

[wakeup]

Thanks all for the replies, I think I now know what to do on the dip switches at the charger end thanks for the information and experienced feedback. Wakeup

 

[wakeup]

I've just re-read the manual on the switch settings for the charger, it would appear that the output for the starter battery is 0.4v lower in both absorption and floating mode than the domestic output as stated before. So sounds like I should set to 15.1volts as 14.7volts will be delivered to the starter during boost then drops to 14volts absorption which sounds about right?

 

[DavidJ]

[ QUOTE ]
The batteries have been on charge for 24 hours with boost on the lowest setting and the charger says each battery is only 92% full.

[/ QUOTE ]
Your charger may not be telling you the truth.
From an interesting article:
http://www.batteryuniversity.com/partone-13.htm
It says wait 24 hrs after charging and measure the voltage. A 100% charged lead acid battery should measure 12.65 V. I wonder what yours are giving?

 

[wakeup]

Hmm, thanks, now i've read too much, my head hurts.... I think I will give it 24 hours as suggested.

 

[AdeOlly]

Hmmmm interesting. My Marine Electronics Bible reckons a fully charged 12v battery on open circuit should be 12.75v.....

 

[DavidJ]

[ QUOTE ]
Hmm, thanks, now i've read too much, my head hurts.... I think I will give it 24 hours as suggested.

[/ QUOTE ]
Dunno where I got 24hrs from, reading again it says 4-8 hrs.

 

[wakeup]

I need the 24 hours for my brain to stop hurting after reading all parts 1 through 3 ;-)

 

[James_Hortop]

The Numax batteries are standard lead/acid if they have "openable" battery caps.

Bulk Charge: 14.6-14.8V
Float: 13.2V

If they are sealed wet lead/acid Numax units they are Lead Calcium and require a higher initial voltage to get them charging properly

Bulk: 14.9-15.2V
Float: 13.2V

James

 

[wakeup]

OK but the description in my charger's manual is the opposite, it says lead sealed should be at the lower input and float voltage than a delphi tin at 15.3v to 14.9v on float.

 

[wakeup]

Correction it reads tin , calcium delpi 15.1 volts boost, 14.4volts floating for domestics and 0.4volts lower on both for starter whereas it states open lead as 13.7volts in boost and 13 volts in float. therefore I am still confused.

It indicates 14.3volts at boost and 13.6volts for sealed batteries and Gel lower agian than that. So I am still tempted to set it to the highest at 15.1 volts for boost on domestics knowing that the starter will be at 14.7 volts on boost and 14.3 volts floating. Boost is time limited to 4 hours. I can switch the boost off altogether. I wish the manual was clearer. Could my open lead batteries also include calcium? If so that these settings should be fine yes?