I am charging a 230AH FLA bank in a motorhome with a Victron IP65 Blue Smart 15 amp charger. The Dekka batteries call for 15.0 to 15.3V for equalization. Whatever I set the charging voltage at I measure .3V less at the battery terminals. With the charger display showing that it is putting out 15.3V the reading at the batteries is only 15.0, is this normal and if so which voltage should I use when applying manufacturer's recommendations. The charging cord is 6 feet and it is AWG 12 copper. Am I seeing voltage drop due to the wire?
Charger setting vs actual voltage at terminals
- Thread starter bigb56
- Start date
I got it figured out as voltage drop and will compensate as needed with adjustments, not sure if a 10 or 8 AWG would change much since we're only talking 2% VD. Meanwhile as far as temperature compensation do I use ambient or actual battery temperature?
MichaelK
Solar Wizard
I would consider even 8gauge thin for a battery connection.
Use the actual battery temperature by an acessory sensor attached to one of the terminals.
Lead won't take on ambient temperatures for many hours, so to avoid either accidental over or undercharge due to ambient sensors in the SCC or battery charger - especially when in the high-voltage EQ stage, - use a sensor at the battery terminal to get the real temp to get the proper compensation.
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Be carefully with the compensation.
If you mean with compensation that you put a higher voltage at the charger to see the expected voltage at the battery you run following risk; when the battery gets full, the current will drop. But then the voltage will drop less between charger and battery and you risk putting higher voltages then expected to the battery.
@Walter - so glad you pointed that out.
The compensation I meant was the automatic one in the SCC or charger itself being best determined with an accessory probe at the terminals.
Doing a manual-compensation if one has the ability - say with a programmable supply - is a fool's errand at EQ and looking at manual temperature-compensation charts. One wonders "who's making a bowl of rice-crispies right now? Oh crud, that's me!"
The compensation I meant was the automatic one in the SCC or charger itself being best determined with an accessory probe at the terminals.
Doing a manual-compensation if one has the ability - say with a programmable supply - is a fool's errand at EQ and looking at manual temperature-compensation charts. One wonders "who's making a bowl of rice-crispies right now? Oh crud, that's me!"
I am now confused, as the equalizing charge progressed the current gradually rose and as it did the voltage dropped. At the start the current as reported by the Victron charger was 6.3A and the voltage was 15.01 as measured at the battery terminals. Checking every 15 min for six hours current gradually increased (by tenths of an amp) and the voltage gradually decreased and by the end of the six hour period the current reported by the Victron charger was 7.2A and the voltage measured at the terminals was 14.97.
Ok, just to make sure we aren't heading into dangrous territory by leaving out some variables if one is relying on solely on voltage and current for FLA during the EQ process.
So...
What does the Dekka / East Penn (great batts btw) technical manual that should have come with your battery say to do? Does it involve taking reading with a hydrometer?
A very generic guideline of the process can be found here, but always follow your manufacturer's specific instructions:
Are we leaving out the all-important SG (specific gravity of the acidic electrolyte) readings as shown by a hydrometer as the ultimate arbiter of when things are done?
If you aren't doing a true FLA EQ, but a simplified "refresher" (sadly also called EQ in most SCC's which adds to the confusion) that doesn't involve the use of a hydrometer, we may be on a different page.
So...
What does the Dekka / East Penn (great batts btw) technical manual that should have come with your battery say to do? Does it involve taking reading with a hydrometer?
A very generic guideline of the process can be found here, but always follow your manufacturer's specific instructions:
https://www.usbattery.com/how-to-equalize-charge-and-prevent-stratification-on-deep-cycle-batteries/
Are we leaving out the all-important SG (specific gravity of the acidic electrolyte) readings as shown by a hydrometer as the ultimate arbiter of when things are done?
If you aren't doing a true FLA EQ, but a simplified "refresher" (sadly also called EQ in most SCC's which adds to the confusion) that doesn't involve the use of a hydrometer, we may be on a different page.
First of all thanks for taking the time to help me, it is much appreciated. The 1 year old batteries (which I acquired with the purchase of a used motor home) are 6 volt 230AH connected in series and are sold by Napa as Golf Car batteries and the part number I crossed to the East Penn Dekka battery, the info I found online from East Penn does say to equalize until SG no longer rises over 1 hour. I found other quoted information that East Penn also stated to equalize between 15.0 and 15.3V until current stops rising over 1 hour. I chose that method as it seemed more accurate than using a hydrometer which I sometimes have trouble with. The batteries were low on water when I got them, but the plates were not exposed, so I added quite a bit of water and hydrometer readings of course were then very low which is another reason I chose the second method.
Before I added the water the SG was between 1.275 and 1.300 on all cells but one which was just over 1.250. Afterwords they all seemed to be barely 1.275. As soon as I was finished we had to leave town on an emergency and the batteries were put into light use and also kept on MH converter charge during the evenings. Now home and will have time to check further.
Any advice will be gladly accepted. Also what is a good hydrometer, I have been using the basic glass tube ones and tried one with temperature compensation but both are presently old and dried out rubber, would like to order a good one.
Thanks, Brian
@bigb56 You're actually doing just fine. Don't sweat it - what you are doing now is 90% effective.
So it's not like you are maintaining brand-new Rolls batteries! Personally unless you want to become married to maintenance, I'd just do what you are doing now and call it a day. And there's the issue of trying to treat used Golf Cart batteries like they were gold. There is a practical limit on how lab-accurate one wants to become with these.
So you're doing just fine. Hydrometer recommendation? Use a stick-type, not any floating balls or pointers. Some come with temperature compensation built-in, (which sometime is in itself not accurate!), so now you have to consult a chart to offset.
Get it wrong and you actually blow your EQ. But here is what Rolls advises:
support.rollsbattery.com
Really? You can see why for your next bank you might want to look into LiFeP04!
You're doing fine now. A few elevated voltage refreshes now and then - enjoy the rest of your bank capacity. I think you are already on top of things as it stands!
So it's not like you are maintaining brand-new Rolls batteries! Personally unless you want to become married to maintenance, I'd just do what you are doing now and call it a day. And there's the issue of trying to treat used Golf Cart batteries like they were gold. There is a practical limit on how lab-accurate one wants to become with these.
So you're doing just fine. Hydrometer recommendation? Use a stick-type, not any floating balls or pointers. Some come with temperature compensation built-in, (which sometime is in itself not accurate!), so now you have to consult a chart to offset.
Get it wrong and you actually blow your EQ. But here is what Rolls advises:
measuring specific gravity
Specific Gravity: The most accurate and direct way to test the state of charge of a battery cell is to determine the specific gravity of the battery electrolyte. The higher the specific gravity of the electrolyte the higher the state of charg...
support.rollsbattery.com
Really? You can see why for your next bank you might want to look into LiFeP04!
You're doing fine now. A few elevated voltage refreshes now and then - enjoy the rest of your bank capacity. I think you are already on top of things as it stands!
Thanks, I tend to be a perfectionist with my vehicles but I can see your point, I could easily spend more money and time than the batteries are worth. I have a total of 8 FLA batteries in my care and I regularly maintain the water and occasionally load test the starting batteries with a carbon pile. I read up on load testing deep cycle batteries and not sure if I want to go to the trouble although I did set up a crude load test once using 12 volt lamps. I am pretty pleased with the Victron charger though.
