Voltage In Relation To Current (Video)
- Thread starter Maine Sail
- Start date
If the load exceeds your charger then the voltage will fall and the charger will revert to constant current mode trying to attain the voltage set point. If the charger is large enough to support the load and the battery charging you will see a dip then a recovery as the charger adds current to the system in order to maintain the voltage.
If it is a steady load and the charger can maintain its voltage then the battery will still take what it needs and the appliance will get the rest. If the initial dip was big enough the battery will accept slightly more for a period of time than it was before the load but the charger will just suply what is needed. It only knows voltage and is only trying to maintain voltage. It will adjust the current to maintain the voltage. That said some older style chargers were rather sloppy at this. Newer power supply type chargers do a much better job and react quite quickly to sudden changes...
The charger on our boat is so fast as a power supply that I run it all winter with no batteries even connected.... I can flip lights and loads on and barely get any percievable dip...
I have a Battery Tender Jr. which I have used to keep the voltage up on Catalina 27's starting battery when I'm away from the boat. Is there anything wrong with just using the simple BTJ for this purpose as opposed to some more sophisticated system? I've used a BTJ for my boat and lawnmower batteries over the winter and as I understand them they don't overcharge a battery(they turn off the current when a battery is fully charge).
The problem with the Battery Tender units is that while they can do an decent job of "maintaining" a charge they really have a tough time actually "charging". Batteries, especially deep cycle, like to be charged at about 10% of "C". "C" is capacity so a 200Ah bank would ideally like a 20A charger. You can go smaller but the time to full just takes longer. Going too small leaves you with multiple days below 100% SOC which can degrade the bank. Now add a bilge pump or other "phantom" or parasitic load and the time to full can double or triple. A sufficient sized charger helps get the electrolyte rolling and gets the batteries back to "full" faster and with less sulfation.
The BTJ, IIRC, pumps out only 0.75A. So a 200Ah bank at 50% SOC would take 6.1 days to get to full (not including any phantom loads or bilge pump etc.). That is 6 days at below full every time you came back from a weekend with a depleted bank. If you go our every weekend you may wind up not even getting back to 100% before you leave again. Every day spent at less than 100% SOC cuts into the overall life of the battery especially in warmer climates with warmer water..
For "maintainers" the BTJ is not bad, except that Deltran tends to keep their charging voltages a big secret, don't know why? It will work but battery life would not be as optimal as it would be with a larger charger that can restore the battery faster.
Doesn't the indicator light on the BTJ when it turns green mean that the battery is fully charged? Invariably the light is green when I return to the boat. Also, on my boat I have a 110 bilge pump connected when I'm away.
I am looking at buying a C-Tek charger to charge and maintain a 60Ah Sealed Wet Cell and a 100Ah Gel Cell battery - at different times of course. I was given the Gel Cell and it still appears to be in good condition. However there is still some life in the 60Ah wet cell and I will use it in the boat until such times as it wears out and I will then change over to the 100Ah Gel cell.
The C-Tek M100 and MSX7.0 seem to essentially be the same charger. The M100 seems to get sold via marine retailers and the MSX7.0 via other retailers - I have no idea if there is any difference or if the arrangement is more to do with maintaining margins &/or separating channels on the products. The C-Tek manual for the M100 says "M100 can easily be configured to charge many different types of 12V lead-acid batteries; wet batteries, MF, AGM and for most GEL-batteries". LIkewise the MSX7.0 manual states ."14.4V/7A. Use for WET batteries, Ca/Ca, MF and for most GEL batteries".(my underlining of most in both cases). C-Tek say both chargers are good for charging 14-150Ah batteries and mainaining up to 225Ah batteries. From the data they present they say the lowest charging voltage is 14.4V (in 'Normal' mode) .This all sounds a bit odd in light of what you say about Gel Cells needing max 14.1V for charging. Do you think it safe to be using the M100 or MSX7.0 on a Gel Cell battery and seeing the charger is only a 7 amp charger is it a bit light weight for that battery?
Pretty tough to answer the question without knowing who made the battery and what they want to see for charging voltages. Most GEL batteries want to see no more than 14.1V. Pusing the voltage can cause "bubbles" to form in the Jello like electrolyte. These bubbles become permananet and eventually destroy the battery.
Lots of "cheap" chargers claim what ever they want to get you to part with your money it does not mean what they say, as in "most" is necessarily correct.
I always harken back to a customer of mine who destroyed THOUSANDS of dollars in GEL batteries using a cheap Schumacher charger that claimed "GEL" and even had a "GEL" button..
Thanks Maine Sail - yes I can see that was a tough ask. The Gel battery is a
Full River DC G100 - 12 (ie. Deep cycle battery) 12V 100Ah/20HR/GEL.
It does not seem to be listed on their current web site http://www.fullriver.com/products/dclist.htm
From information I gathered in the past I had the following notes:
Probably about 540CCA from web site info
Cyclic Application
Valve Regulated Rechargable
Constant Voltage Charge:
Flood Charge: 13.6-13.8V/77oF (25oC)
Cyclic Charge 14.5-14.9V/77oF (25oC)
Don't know if that is of help?
I am not very knowledgable on the electicical stuff but I presume this is saying that the initial 'bulk' charge should not be above 13.8V? Is that correct?
There is a "Charge Voltage Quick Reference" Guide on page 10 of the Full River brochure on these "DC" series batteries http://www.fullriver.com/products/admin/upfile/DCseriesbrochures.pdf
The information in this table seems to conflict a bit with the initial information I had collected above so I am totally lost as to what is the correct charging voltage.
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