Brand new exide dual purpose deep cycle/starting - Not charging past 12.9v?

[CamaroMan]

Hi all - bought a brand new exide 3 days ago - month stamped on it says manufactured last month -

I left it on a 4 stage charger overnight and it charged up to 12.96 (measured after removing charger). After letting it sit overnight it "cooled" down to 12.85v -

is this possibly an indication of sth wrong? im used to batteries charging up to 13.5v, sometimes 13.8 - and slowly going down to perhaps 13.3.. but 12.9 MAX seems to be very odd.

Model is Exide 27mdp
http://www.exide.com/us/en/product-...oduct/exide-nautilus-marine-dual-purpose.aspx

 

[MH Hawker]

12.9 is fine, most brand new baterys will be around 12.6 to 12.9 volts after sitting over night, 13.5 is charging volts

 

[CamaroMan]

thanks - i was under the impression initial charging volts would be 14.4? anyway ill see how it goes, I have a 12 month warranty. If this thing shows ANY signs of running down too quick ill take it right back.

 

[MH Hawker]

it depends a battery will draw a lot when first hooked up, then drops off and this is very generalized for charging systems, do a test of your truck battery before the first start of the day

 

[dingbat]

A fresh, fully charged battery should fall in 12.85 to 12.9 range. Anything over that is a residual surface charge that should be discharged prior to testing

 

[Silvertip]

You have a 12 volt battery (12.6 volts to be exact) which consists of the six cells of 2.1 volts each. You do not have a 13.5 volt or 14.4 volt battery. A 12 volt battery needs to charge at a voltage higher than 12.6 volts or it will never fully charge. Once the charger is removed the voltage will quickly drop back to 12.6 volts.So in a nutshell, you have a perfectly normal battery.

 

[CamaroMan]

great thanks guys! yes it settled at 12.86 and not much less over a week. Worked fine over the weekend. Another question - the 2 terminals, are they connected? ie on same circuit or is the big one for starting ONLY and smaller one for accs (deep cycle) or can i put some accs on bog terminal as well? both batteries are dual purpose -

thanks

 

[Bondo]

Another question - the 2 terminals, are they connected? ie on same circuit or is the big one for starting ONLY and smaller one for accs (deep cycle) or can i put some accs on bog terminal as well? both batteries are dual purpose -

Ayuh,.... What terminals, where,..??

 

[esox07]

Post deleted.

 

[esox07]

The Exide batteries have both bolt and nut type terminals, as well as the standard lead posts. They are both the same. Regardless which connection you use, they should function the same. They are just two alternate connectors. Generally you use the posts for connecting to the starter on the motor and you would use the other screw posts for connecting electronics.

 

[esox07]

By the way, I have two of these batteries (Deep Cycle version as pictured above). I have had one on my travel trailer for three years now and just bought a second one for my trolling motor. So far so good. I keep the travel trailer one on a BatteryMinder 1500 when not in use and occassionally put it on the trolling motor battery to top it off every so often. Maintenance is the key. Most marine batteries will last a long time if you keep them maintained right after and between uses.

 

[CamaroMan]

thanks esox - thats what i was looking for! they seemed to hold up well on last trip. My boat is old and the wiring is probably a little different that original - I wanted a one wire with a diode to run from alternator to my backup battery so it will basically always get a charge without me hav ing to switch the battery isolator to "both" on a long run -

issue i have is the primary battery will feed into this constantly with only a single diode:

my plan is to wire it as such:


Alt =>>=========== diode1 >>> main batt
|
|
|
2nd diode to backup batt

this way the power can only flow into backup battery from alternator, and diode 1 blocks current flowing from batt 1 to my backup -



fyi im using the 50v hi amp diode from radioshack at about 2 bucks a piece. this way both batteries get charged and neither battery can flow into the other one

 

[dingbat]

fyi im using the 50v hi amp diode from radioshack at about 2 bucks a piece. this way both batteries get charged and neither battery can flow into the other one

Have a part number for these $2, 50 amp diodes?

What is the voltage drop thru them?

 

[bruceb58]

Don't use diodes. Use an ACR. Charging through a diode is a bad idea because of the voltage drop and will not allow your battery to fully charge.

https://www.bluesea.com/products/category/35/Automatic Charging Relays

 

[CamaroMan]

thanks for that - wont be spending 75+ now on another part.. ill see what volt drop im getting - currently the system runs at 14.8 max, so im sure a little drop wouldnt be too much of an issue? ill take some readings next time boat is running.

 

[bruceb58]

thanks for that - wont be spending 75+ now on another part.. ill see what volt drop im getting - currently the system runs at 14.8 max, so im sure a little drop wouldnt be too much of an issue? ill take some readings next time boat is running.

Not an issue if you don't mind your batteries not getting full charged which in my opinion is a poor choice.

 

[CamaroMan]

Ill measure it next when running - I did notice my main batt was around 12.6 when I went out.. after fishing for about 2 hours (after standing she was at 13.3) - is it reasonably safe to assume the diode isnt taking too much out?

How much drop wd I expect from a 50v diode?

I wd like to understand thanks

 

[bruceb58]

How much drop wd I expect from a 50v diode?

Depends on what type of diode. Can be as much as 0.7V.

The problem is that because of the diode drop, the alternator is fooled and thinks your battery is charged sooner than it really is. It may get to be 90% charged but wouldn't you like it to get 100% charged?

Out of curiosity, how much current is this diode rated for? Typically, you would need a diode with a huge heat sink on it to work properly. You could easily get massive amounts of current through the diode if the battery being fed by the diode is very discharged.

 

[CamaroMan]

cant quite recall - its a 50v inline one that looks like a resistor.. no heatsink etc - bought 2 from r-shack for 2 bucks.. ill do a running test and see what the drop is.

was just looking for a cheap way to charge both while running - was planning to put one going to main batt and one on the "T" to the 2nd batt, that way batt 1 cant flow over to batt 2.. the alt tho might think its charging one large batt?

not sure -

 

[bruceb58]

cant quite recall - its a 50v inline one that looks like a resistor.. no heatsink etc - bought 2 from r-shack for 2 bucks.. ill do a running test and see what the drop is.

was just looking for a cheap way to charge both while running - was planning to put one going to main batt and one on the "T" to the 2nd batt, that way batt 1 cant flow over to batt 2.. the alt tho might think its charging one large batt?

not sure -

If there is no heatsink on it and one of the batteries that the diode is feeding gets really discharged, what do you think is going to happen to it when 40A flows through it? Poof!!!! 40A x 0.7V = 28W.